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Diffstat (limited to 'Documentation/dev-tools')
51 files changed, 2705 insertions, 1351 deletions
diff --git a/Documentation/dev-tools/autofdo.rst b/Documentation/dev-tools/autofdo.rst new file mode 100644 index 000000000000..bcf06e7d6ffa --- /dev/null +++ b/Documentation/dev-tools/autofdo.rst @@ -0,0 +1,168 @@ +.. SPDX-License-Identifier: GPL-2.0 + +=================================== +Using AutoFDO with the Linux kernel +=================================== + +This enables AutoFDO build support for the kernel when using +the Clang compiler. AutoFDO (Auto-Feedback-Directed Optimization) +is a type of profile-guided optimization (PGO) used to enhance the +performance of binary executables. It gathers information about the +frequency of execution of various code paths within a binary using +hardware sampling. This data is then used to guide the compiler's +optimization decisions, resulting in a more efficient binary. AutoFDO +is a powerful optimization technique, and data indicates that it can +significantly improve kernel performance. It's especially beneficial +for workloads affected by front-end stalls. + +For AutoFDO builds, unlike non-FDO builds, the user must supply a +profile. Acquiring an AutoFDO profile can be done in several ways. +AutoFDO profiles are created by converting hardware sampling using +the "perf" tool. It is crucial that the workload used to create these +perf files is representative; they must exhibit runtime +characteristics similar to the workloads that are intended to be +optimized. Failure to do so will result in the compiler optimizing +for the wrong objective. + +The AutoFDO profile often encapsulates the program's behavior. If the +performance-critical codes are architecture-independent, the profile +can be applied across platforms to achieve performance gains. For +instance, using the profile generated on Intel architecture to build +a kernel for AMD architecture can also yield performance improvements. + +There are two methods for acquiring a representative profile: +(1) Sample real workloads using a production environment. +(2) Generate the profile using a representative load test. +When enabling the AutoFDO build configuration without providing an +AutoFDO profile, the compiler only modifies the dwarf information in +the kernel without impacting runtime performance. It's advisable to +use a kernel binary built with the same AutoFDO configuration to +collect the perf profile. While it's possible to use a kernel built +with different options, it may result in inferior performance. + +One can collect profiles using AutoFDO build for the previous kernel. +AutoFDO employs relative line numbers to match the profiles, offering +some tolerance for source changes. This mode is commonly used in a +production environment for profile collection. + +In a profile collection based on a load test, the AutoFDO collection +process consists of the following steps: + +#. Initial build: The kernel is built with AutoFDO options + without a profile. + +#. Profiling: The above kernel is then run with a representative + workload to gather execution frequency data. This data is + collected using hardware sampling, via perf. AutoFDO is most + effective on platforms supporting advanced PMU features like + LBR on Intel machines. + +#. AutoFDO profile generation: Perf output file is converted to + the AutoFDO profile via offline tools. + +The support requires a Clang compiler LLVM 17 or later. + +Preparation +=========== + +Configure the kernel with:: + + CONFIG_AUTOFDO_CLANG=y + +Customization +============= + +The default CONFIG_AUTOFDO_CLANG setting covers kernel space objects for +AutoFDO builds. One can, however, enable or disable AutoFDO build for +individual files and directories by adding a line similar to the following +to the respective kernel Makefile: + +- For enabling a single file (e.g. foo.o) :: + + AUTOFDO_PROFILE_foo.o := y + +- For enabling all files in one directory :: + + AUTOFDO_PROFILE := y + +- For disabling one file :: + + AUTOFDO_PROFILE_foo.o := n + +- For disabling all files in one directory :: + + AUTOFDO_PROFILE := n + +Workflow +======== + +Here is an example workflow for AutoFDO kernel: + +1) Build the kernel on the host machine with LLVM enabled, + for example, :: + + $ make menuconfig LLVM=1 + + Turn on AutoFDO build config:: + + CONFIG_AUTOFDO_CLANG=y + + With a configuration that with LLVM enabled, use the following command:: + + $ scripts/config -e AUTOFDO_CLANG + + After getting the config, build with :: + + $ make LLVM=1 + +2) Install the kernel on the test machine. + +3) Run the load tests. The '-c' option in perf specifies the sample + event period. We suggest using a suitable prime number, like 500009, + for this purpose. + + - For Intel platforms:: + + $ perf record -e BR_INST_RETIRED.NEAR_TAKEN:k -a -N -b -c <count> -o <perf_file> -- <loadtest> + + - For AMD platforms: + + The supported systems are: Zen3 with BRS, or Zen4 with amd_lbr_v2. To check, + + For Zen3:: + + $ cat /proc/cpuinfo | grep " brs" + + For Zen4:: + + $ cat /proc/cpuinfo | grep amd_lbr_v2 + + The following command generated the perf data file:: + + $ perf record --pfm-events RETIRED_TAKEN_BRANCH_INSTRUCTIONS:k -a -N -b -c <count> -o <perf_file> -- <loadtest> + +4) (Optional) Download the raw perf file to the host machine. + +5) To generate an AutoFDO profile, two offline tools are available: + create_llvm_prof and llvm_profgen. The create_llvm_prof tool is part + of the AutoFDO project and can be found on GitHub + (https://github.com/google/autofdo), version v0.30.1 or later. + The llvm_profgen tool is included in the LLVM compiler itself. It's + important to note that the version of llvm_profgen doesn't need to match + the version of Clang. It needs to be the LLVM 19 release of Clang + or later, or just from the LLVM trunk. :: + + $ llvm-profgen --kernel --binary=<vmlinux> --perfdata=<perf_file> -o <profile_file> + + or :: + + $ create_llvm_prof --binary=<vmlinux> --profile=<perf_file> --format=extbinary --out=<profile_file> + + Note that multiple AutoFDO profile files can be merged into one via:: + + $ llvm-profdata merge -o <profile_file> <profile_1> <profile_2> ... <profile_n> + +6) Rebuild the kernel using the AutoFDO profile file with the same config as step 1, + (Note CONFIG_AUTOFDO_CLANG needs to be enabled):: + + $ make LLVM=1 CLANG_AUTOFDO_PROFILE=<profile_file> diff --git a/Documentation/dev-tools/checkpatch.rst b/Documentation/dev-tools/checkpatch.rst index c3389c6f3838..fa2988dd4657 100644 --- a/Documentation/dev-tools/checkpatch.rst +++ b/Documentation/dev-tools/checkpatch.rst @@ -168,7 +168,7 @@ Available options: - --fix - This is an EXPERIMENTAL feature. If correctable errors exists, a file + This is an EXPERIMENTAL feature. If correctable errors exist, a file <inputfile>.EXPERIMENTAL-checkpatch-fixes is created which has the automatically fixable errors corrected. @@ -181,7 +181,7 @@ Available options: - --ignore-perl-version - Override checking of perl version. Runtime errors maybe encountered after + Override checking of perl version. Runtime errors may be encountered after enabling this flag if the perl version does not meet the minimum specified. - --codespell @@ -342,24 +342,6 @@ API usage See: https://www.kernel.org/doc/html/latest/RCU/whatisRCU.html#full-list-of-rcu-apis - **DEPRECATED_VARIABLE** - EXTRA_{A,C,CPP,LD}FLAGS are deprecated and should be replaced by the new - flags added via commit f77bf01425b1 ("kbuild: introduce ccflags-y, - asflags-y and ldflags-y"). - - The following conversion scheme maybe used:: - - EXTRA_AFLAGS -> asflags-y - EXTRA_CFLAGS -> ccflags-y - EXTRA_CPPFLAGS -> cppflags-y - EXTRA_LDFLAGS -> ldflags-y - - See: - - 1. https://lore.kernel.org/lkml/20070930191054.GA15876@uranus.ravnborg.org/ - 2. https://lore.kernel.org/lkml/1313384834-24433-12-git-send-email-lacombar@gmail.com/ - 3. https://www.kernel.org/doc/html/latest/kbuild/makefiles.html#compilation-flags - **DEVICE_ATTR_FUNCTIONS** The function names used in DEVICE_ATTR is unusual. Typically, the store and show functions are used with <attr>_store and @@ -470,8 +452,6 @@ API usage usleep_range() should be preferred over udelay(). The proper way of using usleep_range() is mentioned in the kernel docs. - See: https://www.kernel.org/doc/html/latest/timers/timers-howto.html#delays-information-on-the-various-kernel-delay-sleep-mechanisms - Comments -------- @@ -481,16 +461,9 @@ Comments line comments is:: /* - * This is the preferred style - * for multi line comments. - */ - - The networking comment style is a bit different, with the first line - not empty like the former:: - - /* This is the preferred comment style - * for files in net/ and drivers/net/ - */ + * This is the preferred style + * for multi line comments. + */ See: https://www.kernel.org/doc/html/latest/process/coding-style.html#commenting @@ -515,6 +488,15 @@ Comments See: https://lore.kernel.org/lkml/20131006222342.GT19510@leaf/ + **UNCOMMENTED_RGMII_MODE** + Historically, the RGMII PHY modes specified in Device Trees have been + used inconsistently, often referring to the usage of delays on the PHY + side rather than describing the board. + + PHY modes "rgmii", "rgmii-rxid" and "rgmii-txid" modes require the clock + signal to be delayed on the PCB; this unusual configuration should be + described in a comment. If they are not (meaning that the delay is realized + internally in the MAC or PHY), "rgmii-id" is the correct PHY mode. Commit message -------------- @@ -906,6 +888,20 @@ Macros, Attributes and Symbols See: https://lore.kernel.org/lkml/1399671106.2912.21.camel@joe-AO725/ + **MACRO_ARG_UNUSED** + If function-like macros do not utilize a parameter, it might result + in a build warning. We advocate for utilizing static inline functions + to replace such macros. + For example, for a macro such as the one below:: + + #define test(a) do { } while (0) + + there would be a warning like below:: + + WARNING: Argument 'a' is not used in function-like macro. + + See: https://www.kernel.org/doc/html/latest/process/coding-style.html#macros-enums-and-rtl + **SINGLE_STATEMENT_DO_WHILE_MACRO** For the multi-statement macros, it is necessary to use the do-while loop to avoid unpredictable code paths. The do-while loop helps to @@ -1242,6 +1238,16 @@ Others The patch file does not appear to be in unified-diff format. Please regenerate the patch file before sending it to the maintainer. + **PLACEHOLDER_USE** + Detects unhandled placeholder text left in cover letters or commit headers/logs. + Common placeholders include lines like:: + + *** SUBJECT HERE *** + *** BLURB HERE *** + + These typically come from autogenerated templates. Replace them with a proper + subject and description before sending. + **PRINTF_0XDECIMAL** Prefixing 0x with decimal output is defective and should be corrected. diff --git a/Documentation/dev-tools/checkuapi.rst b/Documentation/dev-tools/checkuapi.rst new file mode 100644 index 000000000000..9072f21b50b0 --- /dev/null +++ b/Documentation/dev-tools/checkuapi.rst @@ -0,0 +1,477 @@ +.. SPDX-License-Identifier: GPL-2.0-only + +============ +UAPI Checker +============ + +The UAPI checker (``scripts/check-uapi.sh``) is a shell script which +checks UAPI header files for userspace backwards-compatibility across +the git tree. + +Options +======= + +This section will describe the options with which ``check-uapi.sh`` +can be run. + +Usage:: + + check-uapi.sh [-b BASE_REF] [-p PAST_REF] [-j N] [-l ERROR_LOG] [-i] [-q] [-v] + +Available options:: + + -b BASE_REF Base git reference to use for comparison. If unspecified or empty, + will use any dirty changes in tree to UAPI files. If there are no + dirty changes, HEAD will be used. + -p PAST_REF Compare BASE_REF to PAST_REF (e.g. -p v6.1). If unspecified or empty, + will use BASE_REF^1. Must be an ancestor of BASE_REF. Only headers + that exist on PAST_REF will be checked for compatibility. + -j JOBS Number of checks to run in parallel (default: number of CPU cores). + -l ERROR_LOG Write error log to file (default: no error log is generated). + -i Ignore ambiguous changes that may or may not break UAPI compatibility. + -q Quiet operation. + -v Verbose operation (print more information about each header being checked). + +Environmental args:: + + ABIDIFF Custom path to abidiff binary + CC C compiler (default is "gcc") + ARCH Target architecture of C compiler (default is host arch) + +Exit codes:: + + 0) Success + 1) ABI difference detected + 2) Prerequisite not met + +Examples +======== + +Basic Usage +----------- + +First, let's try making a change to a UAPI header file that obviously +won't break userspace:: + + cat << 'EOF' | patch -l -p1 + --- a/include/uapi/linux/acct.h + +++ b/include/uapi/linux/acct.h + @@ -21,7 +21,9 @@ + #include <asm/param.h> + #include <asm/byteorder.h> + + -/* + +#define FOO + + + +/* + * comp_t is a 16-bit "floating" point number with a 3-bit base 8 + * exponent and a 13-bit fraction. + * comp2_t is 24-bit with 5-bit base 2 exponent and 20 bit fraction + diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h + EOF + +Now, let's use the script to validate:: + + % ./scripts/check-uapi.sh + Installing user-facing UAPI headers from dirty tree... OK + Installing user-facing UAPI headers from HEAD... OK + Checking changes to UAPI headers between HEAD and dirty tree... + All 912 UAPI headers compatible with x86 appear to be backwards compatible + +Let's add another change that *might* break userspace:: + + cat << 'EOF' | patch -l -p1 + --- a/include/uapi/linux/bpf.h + +++ b/include/uapi/linux/bpf.h + @@ -74,7 +74,7 @@ struct bpf_insn { + __u8 dst_reg:4; /* dest register */ + __u8 src_reg:4; /* source register */ + __s16 off; /* signed offset */ + - __s32 imm; /* signed immediate constant */ + + __u32 imm; /* unsigned immediate constant */ + }; + + /* Key of an a BPF_MAP_TYPE_LPM_TRIE entry */ + EOF + +The script will catch this:: + + % ./scripts/check-uapi.sh + Installing user-facing UAPI headers from dirty tree... OK + Installing user-facing UAPI headers from HEAD... OK + Checking changes to UAPI headers between HEAD and dirty tree... + ==== ABI differences detected in include/linux/bpf.h from HEAD -> dirty tree ==== + [C] 'struct bpf_insn' changed: + type size hasn't changed + 1 data member change: + type of '__s32 imm' changed: + typedef name changed from __s32 to __u32 at int-ll64.h:27:1 + underlying type 'int' changed: + type name changed from 'int' to 'unsigned int' + type size hasn't changed + ================================================================================== + + error - 1/912 UAPI headers compatible with x86 appear _not_ to be backwards compatible + +In this case, the script is reporting the type change because it could +break a userspace program that passes in a negative number. Now, let's +say you know that no userspace program could possibly be using a negative +value in ``imm``, so changing to an unsigned type there shouldn't hurt +anything. You can pass the ``-i`` flag to the script to ignore changes +in which the userspace backwards compatibility is ambiguous:: + + % ./scripts/check-uapi.sh -i + Installing user-facing UAPI headers from dirty tree... OK + Installing user-facing UAPI headers from HEAD... OK + Checking changes to UAPI headers between HEAD and dirty tree... + All 912 UAPI headers compatible with x86 appear to be backwards compatible + +Now, let's make a similar change that *will* break userspace:: + + cat << 'EOF' | patch -l -p1 + --- a/include/uapi/linux/bpf.h + +++ b/include/uapi/linux/bpf.h + @@ -71,8 +71,8 @@ enum { + + struct bpf_insn { + __u8 code; /* opcode */ + - __u8 dst_reg:4; /* dest register */ + __u8 src_reg:4; /* source register */ + + __u8 dst_reg:4; /* dest register */ + __s16 off; /* signed offset */ + __s32 imm; /* signed immediate constant */ + }; + EOF + +Since we're re-ordering an existing struct member, there's no ambiguity, +and the script will report the breakage even if you pass ``-i``:: + + % ./scripts/check-uapi.sh -i + Installing user-facing UAPI headers from dirty tree... OK + Installing user-facing UAPI headers from HEAD... OK + Checking changes to UAPI headers between HEAD and dirty tree... + ==== ABI differences detected in include/linux/bpf.h from HEAD -> dirty tree ==== + [C] 'struct bpf_insn' changed: + type size hasn't changed + 2 data member changes: + '__u8 dst_reg' offset changed from 8 to 12 (in bits) (by +4 bits) + '__u8 src_reg' offset changed from 12 to 8 (in bits) (by -4 bits) + ================================================================================== + + error - 1/912 UAPI headers compatible with x86 appear _not_ to be backwards compatible + +Let's commit the breaking change, then commit the innocuous change:: + + % git commit -m 'Breaking UAPI change' include/uapi/linux/bpf.h + [detached HEAD f758e574663a] Breaking UAPI change + 1 file changed, 1 insertion(+), 1 deletion(-) + % git commit -m 'Innocuous UAPI change' include/uapi/linux/acct.h + [detached HEAD 2e87df769081] Innocuous UAPI change + 1 file changed, 3 insertions(+), 1 deletion(-) + +Now, let's run the script again with no arguments:: + + % ./scripts/check-uapi.sh + Installing user-facing UAPI headers from HEAD... OK + Installing user-facing UAPI headers from HEAD^1... OK + Checking changes to UAPI headers between HEAD^1 and HEAD... + All 912 UAPI headers compatible with x86 appear to be backwards compatible + +It doesn't catch any breaking change because, by default, it only +compares ``HEAD`` to ``HEAD^1``. The breaking change was committed on +``HEAD~2``. If we wanted the search scope to go back further, we'd have to +use the ``-p`` option to pass a different past reference. In this case, +let's pass ``-p HEAD~2`` to the script so it checks UAPI changes between +``HEAD~2`` and ``HEAD``:: + + % ./scripts/check-uapi.sh -p HEAD~2 + Installing user-facing UAPI headers from HEAD... OK + Installing user-facing UAPI headers from HEAD~2... OK + Checking changes to UAPI headers between HEAD~2 and HEAD... + ==== ABI differences detected in include/linux/bpf.h from HEAD~2 -> HEAD ==== + [C] 'struct bpf_insn' changed: + type size hasn't changed + 2 data member changes: + '__u8 dst_reg' offset changed from 8 to 12 (in bits) (by +4 bits) + '__u8 src_reg' offset changed from 12 to 8 (in bits) (by -4 bits) + ============================================================================== + + error - 1/912 UAPI headers compatible with x86 appear _not_ to be backwards compatible + +Alternatively, we could have also run with ``-b HEAD~``. This would set the +base reference to ``HEAD~`` so then the script would compare it to ``HEAD~^1``. + +Architecture-specific Headers +----------------------------- + +Consider this change:: + + cat << 'EOF' | patch -l -p1 + --- a/arch/arm64/include/uapi/asm/sigcontext.h + +++ b/arch/arm64/include/uapi/asm/sigcontext.h + @@ -70,6 +70,7 @@ struct sigcontext { + struct _aarch64_ctx { + __u32 magic; + __u32 size; + + __u32 new_var; + }; + + #define FPSIMD_MAGIC 0x46508001 + EOF + +This is a change to an arm64-specific UAPI header file. In this example, I'm +running the script from an x86 machine with an x86 compiler, so, by default, +the script only checks x86-compatible UAPI header files:: + + % ./scripts/check-uapi.sh + Installing user-facing UAPI headers from dirty tree... OK + Installing user-facing UAPI headers from HEAD... OK + No changes to UAPI headers were applied between HEAD and dirty tree + +With an x86 compiler, we can't check header files in ``arch/arm64``, so the +script doesn't even try. + +If we want to check the header file, we'll have to use an arm64 compiler and +set ``ARCH`` accordingly:: + + % CC=aarch64-linux-gnu-gcc ARCH=arm64 ./scripts/check-uapi.sh + Installing user-facing UAPI headers from dirty tree... OK + Installing user-facing UAPI headers from HEAD... OK + Checking changes to UAPI headers between HEAD and dirty tree... + ==== ABI differences detected in include/asm/sigcontext.h from HEAD -> dirty tree ==== + [C] 'struct _aarch64_ctx' changed: + type size changed from 64 to 96 (in bits) + 1 data member insertion: + '__u32 new_var', at offset 64 (in bits) at sigcontext.h:73:1 + -- snip -- + [C] 'struct zt_context' changed: + type size changed from 128 to 160 (in bits) + 2 data member changes (1 filtered): + '__u16 nregs' offset changed from 64 to 96 (in bits) (by +32 bits) + '__u16 __reserved[3]' offset changed from 80 to 112 (in bits) (by +32 bits) + ======================================================================================= + + error - 1/884 UAPI headers compatible with arm64 appear _not_ to be backwards compatible + +We can see with ``ARCH`` and ``CC`` set properly for the file, the ABI +change is reported properly. Also notice that the total number of UAPI +header files checked by the script changes. This is because the number +of headers installed for arm64 platforms is different than x86. + +Cross-Dependency Breakages +-------------------------- + +Consider this change:: + + cat << 'EOF' | patch -l -p1 + --- a/include/uapi/linux/types.h + +++ b/include/uapi/linux/types.h + @@ -52,7 +52,7 @@ typedef __u32 __bitwise __wsum; + #define __aligned_be64 __be64 __attribute__((aligned(8))) + #define __aligned_le64 __le64 __attribute__((aligned(8))) + + -typedef unsigned __bitwise __poll_t; + +typedef unsigned short __bitwise __poll_t; + + #endif /* __ASSEMBLY__ */ + #endif /* _UAPI_LINUX_TYPES_H */ + EOF + +Here, we're changing a ``typedef`` in ``types.h``. This doesn't break +a UAPI in ``types.h``, but other UAPIs in the tree may break due to +this change:: + + % ./scripts/check-uapi.sh + Installing user-facing UAPI headers from dirty tree... OK + Installing user-facing UAPI headers from HEAD... OK + Checking changes to UAPI headers between HEAD and dirty tree... + ==== ABI differences detected in include/linux/eventpoll.h from HEAD -> dirty tree ==== + [C] 'struct epoll_event' changed: + type size changed from 96 to 80 (in bits) + 2 data member changes: + type of '__poll_t events' changed: + underlying type 'unsigned int' changed: + type name changed from 'unsigned int' to 'unsigned short int' + type size changed from 32 to 16 (in bits) + '__u64 data' offset changed from 32 to 16 (in bits) (by -16 bits) + ======================================================================================== + include/linux/eventpoll.h did not change between HEAD and dirty tree... + It's possible a change to one of the headers it includes caused this error: + #include <linux/fcntl.h> + #include <linux/types.h> + +Note that the script noticed the failing header file did not change, +so it assumes one of its includes must have caused the breakage. Indeed, +we can see ``linux/types.h`` is used from ``eventpoll.h``. + +UAPI Header Removals +-------------------- + +Consider this change:: + + cat << 'EOF' | patch -l -p1 + diff --git a/include/uapi/asm-generic/Kbuild b/include/uapi/asm-generic/Kbuild + index ebb180aac74e..a9c88b0a8b3b 100644 + --- a/include/uapi/asm-generic/Kbuild + +++ b/include/uapi/asm-generic/Kbuild + @@ -31,6 +31,6 @@ mandatory-y += stat.h + mandatory-y += statfs.h + mandatory-y += swab.h + mandatory-y += termbits.h + -mandatory-y += termios.h + +#mandatory-y += termios.h + mandatory-y += types.h + mandatory-y += unistd.h + EOF + +This script removes a UAPI header file from the install list. Let's run +the script:: + + % ./scripts/check-uapi.sh + Installing user-facing UAPI headers from dirty tree... OK + Installing user-facing UAPI headers from HEAD... OK + Checking changes to UAPI headers between HEAD and dirty tree... + ==== UAPI header include/asm/termios.h was removed between HEAD and dirty tree ==== + + error - 1/912 UAPI headers compatible with x86 appear _not_ to be backwards compatible + +Removing a UAPI header is considered a breaking change, and the script +will flag it as such. + +Checking Historic UAPI Compatibility +------------------------------------ + +You can use the ``-b`` and ``-p`` options to examine different chunks of your +git tree. For example, to check all changed UAPI header files between tags +v6.0 and v6.1, you'd run:: + + % ./scripts/check-uapi.sh -b v6.1 -p v6.0 + Installing user-facing UAPI headers from v6.1... OK + Installing user-facing UAPI headers from v6.0... OK + Checking changes to UAPI headers between v6.0 and v6.1... + + --- snip --- + error - 37/907 UAPI headers compatible with x86 appear _not_ to be backwards compatible + +Note: Before v5.3, a header file needed by the script is not present, +so the script is unable to check changes before then. + +You'll notice that the script detected many UAPI changes that are not +backwards compatible. Knowing that kernel UAPIs are supposed to be stable +forever, this is an alarming result. This brings us to the next section: +caveats. + +Caveats +======= + +The UAPI checker makes no assumptions about the author's intention, so some +types of changes may be flagged even though they intentionally break UAPI. + +Removals For Refactoring or Deprecation +--------------------------------------- + +Sometimes drivers for very old hardware are removed, such as in this example:: + + % ./scripts/check-uapi.sh -b ba47652ba655 + Installing user-facing UAPI headers from ba47652ba655... OK + Installing user-facing UAPI headers from ba47652ba655^1... OK + Checking changes to UAPI headers between ba47652ba655^1 and ba47652ba655... + ==== UAPI header include/linux/meye.h was removed between ba47652ba655^1 and ba47652ba655 ==== + + error - 1/910 UAPI headers compatible with x86 appear _not_ to be backwards compatible + +The script will always flag removals (even if they're intentional). + +Struct Expansions +----------------- + +Depending on how a structure is handled in kernelspace, a change which +expands a struct could be non-breaking. + +If a struct is used as the argument to an ioctl, then the kernel driver +must be able to handle ioctl commands of any size. Beyond that, you need +to be careful when copying data from the user. Say, for example, that +``struct foo`` is changed like this:: + + struct foo { + __u64 a; /* added in version 1 */ + + __u32 b; /* added in version 2 */ + + __u32 c; /* added in version 2 */ + } + +By default, the script will flag this kind of change for further review:: + + [C] 'struct foo' changed: + type size changed from 64 to 128 (in bits) + 2 data member insertions: + '__u32 b', at offset 64 (in bits) + '__u32 c', at offset 96 (in bits) + +However, it is possible that this change was made safely. + +If a userspace program was built with version 1, it will think +``sizeof(struct foo)`` is 8. That size will be encoded in the +ioctl value that gets sent to the kernel. If the kernel is built +with version 2, it will think the ``sizeof(struct foo)`` is 16. + +The kernel can use the ``_IOC_SIZE`` macro to get the size encoded +in the ioctl code that the user passed in and then use +``copy_struct_from_user()`` to safely copy the value:: + + int handle_ioctl(unsigned long cmd, unsigned long arg) + { + switch _IOC_NR(cmd) { + 0x01: { + struct foo my_cmd; /* size 16 in the kernel */ + + ret = copy_struct_from_user(&my_cmd, arg, sizeof(struct foo), _IOC_SIZE(cmd)); + ... + +``copy_struct_from_user`` will zero the struct in the kernel and then copy +only the bytes passed in from the user (leaving new members zeroized). +If the user passed in a larger struct, the extra members are ignored. + +If you know this situation is accounted for in the kernel code, you can +pass ``-i`` to the script, and struct expansions like this will be ignored. + +Flex Array Migration +-------------------- + +While the script handles expansion into an existing flex array, it does +still flag initial migration to flex arrays from 1-element fake flex +arrays. For example:: + + struct foo { + __u32 x; + - __u32 flex[1]; /* fake flex */ + + __u32 flex[]; /* real flex */ + }; + +This change would be flagged by the script:: + + [C] 'struct foo' changed: + type size changed from 64 to 32 (in bits) + 1 data member change: + type of '__u32 flex[1]' changed: + type name changed from '__u32[1]' to '__u32[]' + array type size changed from 32 to 'unknown' + array type subrange 1 changed length from 1 to 'unknown' + +At this time, there's no way to filter these types of changes, so be +aware of this possible false positive. + +Summary +------- + +While many types of false positives are filtered out by the script, +it's possible there are some cases where the script flags a change +which does not break UAPI. It's also possible a change which *does* +break userspace would not be flagged by this script. While the script +has been run on much of the kernel history, there could still be corner +cases that are not accounted for. + +The intention is for this script to be used as a quick check for +maintainers or automated tooling, not as the end-all authority on +patch compatibility. It's best to remember: use your best judgment +(and ideally a unit test in userspace) to make sure your UAPI changes +are backwards-compatible! diff --git a/Documentation/dev-tools/clang-format.rst b/Documentation/dev-tools/clang-format.rst new file mode 100644 index 000000000000..1d089a847c1b --- /dev/null +++ b/Documentation/dev-tools/clang-format.rst @@ -0,0 +1,184 @@ +.. _clangformat: + +clang-format +============ + +``clang-format`` is a tool to format C/C++/... code according to +a set of rules and heuristics. Like most tools, it is not perfect +nor covers every single case, but it is good enough to be helpful. + +``clang-format`` can be used for several purposes: + + - Quickly reformat a block of code to the kernel style. Specially useful + when moving code around and aligning/sorting. See clangformatreformat_. + + - Spot style mistakes, typos and possible improvements in files + you maintain, patches you review, diffs, etc. See clangformatreview_. + + - Help you follow the coding style rules, specially useful for those + new to kernel development or working at the same time in several + projects with different coding styles. + +Its configuration file is ``.clang-format`` in the root of the kernel tree. +The rules contained there try to approximate the most common kernel +coding style. They also try to follow :ref:`Documentation/process/coding-style.rst <codingstyle>` +as much as possible. Since not all the kernel follows the same style, +it is possible that you may want to tweak the defaults for a particular +subsystem or folder. To do so, you can override the defaults by writing +another ``.clang-format`` file in a subfolder. + +The tool itself has already been included in the repositories of popular +Linux distributions for a long time. Search for ``clang-format`` in +your repositories. Otherwise, you can either download pre-built +LLVM/clang binaries or build the source code from: + + https://releases.llvm.org/download.html + +See more information about the tool at: + + https://clang.llvm.org/docs/ClangFormat.html + + https://clang.llvm.org/docs/ClangFormatStyleOptions.html + + +.. _clangformatreview: + +Review files and patches for coding style +----------------------------------------- + +By running the tool in its inline mode, you can review full subsystems, +folders or individual files for code style mistakes, typos or improvements. + +To do so, you can run something like:: + + # Make sure your working directory is clean! + clang-format -i kernel/*.[ch] + +And then take a look at the git diff. + +Counting the lines of such a diff is also useful for improving/tweaking +the style options in the configuration file; as well as testing new +``clang-format`` features/versions. + +``clang-format`` also supports reading unified diffs, so you can review +patches and git diffs easily. See the documentation at: + + https://clang.llvm.org/docs/ClangFormat.html#script-for-patch-reformatting + +To avoid ``clang-format`` formatting some portion of a file, you can do:: + + int formatted_code; + // clang-format off + void unformatted_code ; + // clang-format on + void formatted_code_again; + +While it might be tempting to use this to keep a file always in sync with +``clang-format``, specially if you are writing new files or if you are +a maintainer, please note that people might be running different +``clang-format`` versions or not have it available at all. Therefore, +you should probably refrain yourself from using this in kernel sources; +at least until we see if ``clang-format`` becomes commonplace. + + +.. _clangformatreformat: + +Reformatting blocks of code +--------------------------- + +By using an integration with your text editor, you can reformat arbitrary +blocks (selections) of code with a single keystroke. This is specially +useful when moving code around, for complex code that is deeply intended, +for multi-line macros (and aligning their backslashes), etc. + +Remember that you can always tweak the changes afterwards in those cases +where the tool did not do an optimal job. But as a first approximation, +it can be very useful. + +There are integrations for many popular text editors. For some of them, +like vim, emacs, BBEdit and Visual Studio you can find support built-in. +For instructions, read the appropriate section at: + + https://clang.llvm.org/docs/ClangFormat.html + +For Atom, Eclipse, Sublime Text, Visual Studio Code, XCode and other +editors and IDEs you should be able to find ready-to-use plugins. + +For this use case, consider using a secondary ``.clang-format`` +so that you can tweak a few options. See clangformatextra_. + + +.. _clangformatmissing: + +Missing support +--------------- + +``clang-format`` is missing support for some things that are common +in kernel code. They are easy to remember, so if you use the tool +regularly, you will quickly learn to avoid/ignore those. + +In particular, some very common ones you will notice are: + + - Aligned blocks of one-line ``#defines``, e.g.:: + + #define TRACING_MAP_BITS_DEFAULT 11 + #define TRACING_MAP_BITS_MAX 17 + #define TRACING_MAP_BITS_MIN 7 + + vs.:: + + #define TRACING_MAP_BITS_DEFAULT 11 + #define TRACING_MAP_BITS_MAX 17 + #define TRACING_MAP_BITS_MIN 7 + + - Aligned designated initializers, e.g.:: + + static const struct file_operations uprobe_events_ops = { + .owner = THIS_MODULE, + .open = probes_open, + .read = seq_read, + .llseek = seq_lseek, + .release = seq_release, + .write = probes_write, + }; + + vs.:: + + static const struct file_operations uprobe_events_ops = { + .owner = THIS_MODULE, + .open = probes_open, + .read = seq_read, + .llseek = seq_lseek, + .release = seq_release, + .write = probes_write, + }; + + +.. _clangformatextra: + +Extra features/options +---------------------- + +Some features/style options are not enabled by default in the configuration +file in order to minimize the differences between the output and the current +code. In other words, to make the difference as small as possible, +which makes reviewing full-file style, as well diffs and patches as easy +as possible. + +In other cases (e.g. particular subsystems/folders/files), the kernel style +might be different and enabling some of these options may approximate +better the style there. + +For instance: + + - Aligning assignments (``AlignConsecutiveAssignments``). + + - Aligning declarations (``AlignConsecutiveDeclarations``). + + - Reflowing text in comments (``ReflowComments``). + + - Sorting ``#includes`` (``SortIncludes``). + +They are typically useful for block re-formatting, rather than full-file. +You might want to create another ``.clang-format`` file and use that one +from your editor/IDE instead. diff --git a/Documentation/dev-tools/coccinelle.rst b/Documentation/dev-tools/coccinelle.rst index d9976069ed12..6e70a1e9a3c0 100644 --- a/Documentation/dev-tools/coccinelle.rst +++ b/Documentation/dev-tools/coccinelle.rst @@ -219,7 +219,7 @@ instance:: cat cocci.err You can use SPFLAGS to add debugging flags; for instance you may want to -add both --profile --show-trying to SPFLAGS when debugging. For example +add both ``--profile --show-trying`` to SPFLAGS when debugging. For example you may want to use:: rm -f err.log @@ -248,27 +248,19 @@ variables for .cocciconfig is as follows: - Your current user's home directory is processed first - Your directory from which spatch is called is processed next -- The directory provided with the --dir option is processed last, if used - -Since coccicheck runs through make, it naturally runs from the kernel -proper dir; as such the second rule above would be implied for picking up a -.cocciconfig when using ``make coccicheck``. +- The directory provided with the ``--dir`` option is processed last, if used ``make coccicheck`` also supports using M= targets. If you do not supply any M= target, it is assumed you want to target the entire kernel. The kernel coccicheck script has:: - if [ "$KBUILD_EXTMOD" = "" ] ; then - OPTIONS="--dir $srctree $COCCIINCLUDE" - else - OPTIONS="--dir $KBUILD_EXTMOD $COCCIINCLUDE" - fi - -KBUILD_EXTMOD is set when an explicit target with M= is used. For both cases -the spatch --dir argument is used, as such third rule applies when whether M= -is used or not, and when M= is used the target directory can have its own -.cocciconfig file. When M= is not passed as an argument to coccicheck the -target directory is the same as the directory from where spatch was called. + OPTIONS="--dir $srcroot $COCCIINCLUDE" + +Here, $srcroot refers to the source directory of the target: it points to the +external module's source directory when M= used, and otherwise, to the kernel +source directory. The third rule ensures the spatch reads the .cocciconfig from +the target directory, allowing external modules to have their own .cocciconfig +file. If not using the kernel's coccicheck target, keep the above precedence order logic of .cocciconfig reading. If using the kernel's coccicheck target, diff --git a/Documentation/dev-tools/gcov.rst b/Documentation/dev-tools/gcov.rst index 5fce2b06f229..075df6a4598d 100644 --- a/Documentation/dev-tools/gcov.rst +++ b/Documentation/dev-tools/gcov.rst @@ -23,7 +23,7 @@ Possible uses: associated code is never run?) .. _gcov: https://gcc.gnu.org/onlinedocs/gcc/Gcov.html -.. _lcov: http://ltp.sourceforge.net/coverage/lcov.php +.. _lcov: https://github.com/linux-test-project/lcov Preparation @@ -75,6 +75,17 @@ Only files which are linked to the main kernel image or are compiled as kernel modules are supported by this mechanism. +Module specific configs +----------------------- + +Gcov kernel configs for specific modules are described below: + +CONFIG_GCOV_PROFILE_RDS: + Enables GCOV profiling on RDS for checking which functions or + lines are executed. This config is used by the rds selftest to + generate coverage reports. If left unset the report is omitted. + + Files ----- diff --git a/Documentation/dev-tools/gdb-kernel-debugging.rst b/Documentation/dev-tools/gdb-kernel-debugging.rst deleted file mode 100644 index 8e0f1fe8d17a..000000000000 --- a/Documentation/dev-tools/gdb-kernel-debugging.rst +++ /dev/null @@ -1,175 +0,0 @@ -.. highlight:: none - -Debugging kernel and modules via gdb -==================================== - -The kernel debugger kgdb, hypervisors like QEMU or JTAG-based hardware -interfaces allow to debug the Linux kernel and its modules during runtime -using gdb. Gdb comes with a powerful scripting interface for python. The -kernel provides a collection of helper scripts that can simplify typical -kernel debugging steps. This is a short tutorial about how to enable and use -them. It focuses on QEMU/KVM virtual machines as target, but the examples can -be transferred to the other gdb stubs as well. - - -Requirements ------------- - -- gdb 7.2+ (recommended: 7.4+) with python support enabled (typically true - for distributions) - - -Setup ------ - -- Create a virtual Linux machine for QEMU/KVM (see www.linux-kvm.org and - www.qemu.org for more details). For cross-development, - https://landley.net/aboriginal/bin keeps a pool of machine images and - toolchains that can be helpful to start from. - -- Build the kernel with CONFIG_GDB_SCRIPTS enabled, but leave - CONFIG_DEBUG_INFO_REDUCED off. If your architecture supports - CONFIG_FRAME_POINTER, keep it enabled. - -- Install that kernel on the guest, turn off KASLR if necessary by adding - "nokaslr" to the kernel command line. - Alternatively, QEMU allows to boot the kernel directly using -kernel, - -append, -initrd command line switches. This is generally only useful if - you do not depend on modules. See QEMU documentation for more details on - this mode. In this case, you should build the kernel with - CONFIG_RANDOMIZE_BASE disabled if the architecture supports KASLR. - -- Enable the gdb stub of QEMU/KVM, either - - - at VM startup time by appending "-s" to the QEMU command line - - or - - - during runtime by issuing "gdbserver" from the QEMU monitor - console - -- cd /path/to/linux-build - -- Start gdb: gdb vmlinux - - Note: Some distros may restrict auto-loading of gdb scripts to known safe - directories. In case gdb reports to refuse loading vmlinux-gdb.py, add:: - - add-auto-load-safe-path /path/to/linux-build - - to ~/.gdbinit. See gdb help for more details. - -- Attach to the booted guest:: - - (gdb) target remote :1234 - - -Examples of using the Linux-provided gdb helpers ------------------------------------------------- - -- Load module (and main kernel) symbols:: - - (gdb) lx-symbols - loading vmlinux - scanning for modules in /home/user/linux/build - loading @0xffffffffa0020000: /home/user/linux/build/net/netfilter/xt_tcpudp.ko - loading @0xffffffffa0016000: /home/user/linux/build/net/netfilter/xt_pkttype.ko - loading @0xffffffffa0002000: /home/user/linux/build/net/netfilter/xt_limit.ko - loading @0xffffffffa00ca000: /home/user/linux/build/net/packet/af_packet.ko - loading @0xffffffffa003c000: /home/user/linux/build/fs/fuse/fuse.ko - ... - loading @0xffffffffa0000000: /home/user/linux/build/drivers/ata/ata_generic.ko - -- Set a breakpoint on some not yet loaded module function, e.g.:: - - (gdb) b btrfs_init_sysfs - Function "btrfs_init_sysfs" not defined. - Make breakpoint pending on future shared library load? (y or [n]) y - Breakpoint 1 (btrfs_init_sysfs) pending. - -- Continue the target:: - - (gdb) c - -- Load the module on the target and watch the symbols being loaded as well as - the breakpoint hit:: - - loading @0xffffffffa0034000: /home/user/linux/build/lib/libcrc32c.ko - loading @0xffffffffa0050000: /home/user/linux/build/lib/lzo/lzo_compress.ko - loading @0xffffffffa006e000: /home/user/linux/build/lib/zlib_deflate/zlib_deflate.ko - loading @0xffffffffa01b1000: /home/user/linux/build/fs/btrfs/btrfs.ko - - Breakpoint 1, btrfs_init_sysfs () at /home/user/linux/fs/btrfs/sysfs.c:36 - 36 btrfs_kset = kset_create_and_add("btrfs", NULL, fs_kobj); - -- Dump the log buffer of the target kernel:: - - (gdb) lx-dmesg - [ 0.000000] Initializing cgroup subsys cpuset - [ 0.000000] Initializing cgroup subsys cpu - [ 0.000000] Linux version 3.8.0-rc4-dbg+ (... - [ 0.000000] Command line: root=/dev/sda2 resume=/dev/sda1 vga=0x314 - [ 0.000000] e820: BIOS-provided physical RAM map: - [ 0.000000] BIOS-e820: [mem 0x0000000000000000-0x000000000009fbff] usable - [ 0.000000] BIOS-e820: [mem 0x000000000009fc00-0x000000000009ffff] reserved - .... - -- Examine fields of the current task struct(supported by x86 and arm64 only):: - - (gdb) p $lx_current().pid - $1 = 4998 - (gdb) p $lx_current().comm - $2 = "modprobe\000\000\000\000\000\000\000" - -- Make use of the per-cpu function for the current or a specified CPU:: - - (gdb) p $lx_per_cpu("runqueues").nr_running - $3 = 1 - (gdb) p $lx_per_cpu("runqueues", 2).nr_running - $4 = 0 - -- Dig into hrtimers using the container_of helper:: - - (gdb) set $next = $lx_per_cpu("hrtimer_bases").clock_base[0].active.next - (gdb) p *$container_of($next, "struct hrtimer", "node") - $5 = { - node = { - node = { - __rb_parent_color = 18446612133355256072, - rb_right = 0x0 <irq_stack_union>, - rb_left = 0x0 <irq_stack_union> - }, - expires = { - tv64 = 1835268000000 - } - }, - _softexpires = { - tv64 = 1835268000000 - }, - function = 0xffffffff81078232 <tick_sched_timer>, - base = 0xffff88003fd0d6f0, - state = 1, - start_pid = 0, - start_site = 0xffffffff81055c1f <hrtimer_start_range_ns+20>, - start_comm = "swapper/2\000\000\000\000\000\000" - } - - -List of commands and functions ------------------------------- - -The number of commands and convenience functions may evolve over the time, -this is just a snapshot of the initial version:: - - (gdb) apropos lx - function lx_current -- Return current task - function lx_module -- Find module by name and return the module variable - function lx_per_cpu -- Return per-cpu variable - function lx_task_by_pid -- Find Linux task by PID and return the task_struct variable - function lx_thread_info -- Calculate Linux thread_info from task variable - lx-dmesg -- Print Linux kernel log buffer - lx-lsmod -- List currently loaded modules - lx-symbols -- (Re-)load symbols of Linux kernel and currently loaded modules - -Detailed help can be obtained via "help <command-name>" for commands and "help -function <function-name>" for convenience functions. diff --git a/Documentation/dev-tools/gpio-sloppy-logic-analyzer.rst b/Documentation/dev-tools/gpio-sloppy-logic-analyzer.rst new file mode 100644 index 000000000000..d69f24c0d9e1 --- /dev/null +++ b/Documentation/dev-tools/gpio-sloppy-logic-analyzer.rst @@ -0,0 +1,93 @@ +.. SPDX-License-Identifier: GPL-2.0 + +============================================= +Linux Kernel GPIO based sloppy logic analyzer +============================================= + +:Author: Wolfram Sang + +Introduction +============ + +This document briefly describes how to run the GPIO based in-kernel sloppy +logic analyzer running on an isolated CPU. + +The sloppy logic analyzer will utilize a few GPIO lines in input mode on a +system to rapidly sample these digital lines, which will, if the Nyquist +criteria is met, result in a time series log with approximate waveforms as they +appeared on these lines. One way to use it is to analyze external traffic +connected to these GPIO lines with wires (i.e. digital probes), acting as a +common logic analyzer. + +Another feature is to snoop on on-chip peripherals if the I/O cells of these +peripherals can be used in GPIO input mode at the same time as they are being +used as inputs or outputs for the peripheral. That means you could e.g. snoop +I2C traffic without any wiring (if your hardware supports it). In the pin +control subsystem such pin controllers are called "non-strict": a certain pin +can be used with a certain peripheral and as a GPIO input line at the same +time. + +Note that this is a last resort analyzer which can be affected by latencies, +non-deterministic code paths and non-maskable interrupts. It is called 'sloppy' +for a reason. However, for e.g. remote development, it may be useful to get a +first view and aid further debugging. + +Setup +===== + +Your kernel must have CONFIG_DEBUG_FS and CONFIG_CPUSETS enabled. Ideally, your +runtime environment does not utilize cpusets otherwise, then isolation of a CPU +core is easiest. If you do need cpusets, check that helper script for the +sloppy logic analyzer does not interfere with your other settings. + +Tell the kernel which GPIOs are used as probes. For a Device Tree based system, +you need to use the following bindings. Because these bindings are only for +debugging, there is no official schema:: + + i2c-analyzer { + compatible = "gpio-sloppy-logic-analyzer"; + probe-gpios = <&gpio6 21 GPIO_OPEN_DRAIN>, <&gpio6 4 GPIO_OPEN_DRAIN>; + probe-names = "SCL", "SDA"; + }; + +Note that you must provide a name for every GPIO specified. Currently a +maximum of 8 probes are supported. 32 are likely possible but are not +implemented yet. + +Usage +===== + +The logic analyzer is configurable via files in debugfs. However, it is +strongly recommended to not use them directly, but to use the script +``tools/gpio/gpio-sloppy-logic-analyzer``. Besides checking parameters more +extensively, it will isolate the CPU core so you will have the least +disturbance while measuring. + +The script has a help option explaining the parameters. For the above DT +snippet which analyzes an I2C bus at 400kHz on a Renesas Salvator-XS board, the +following settings are used: The isolated CPU shall be CPU1 because it is a big +core in a big.LITTLE setup. Because CPU1 is the default, we don't need a +parameter. The bus speed is 400kHz. So, the sampling theorem says we need to +sample at least at 800kHz. However, falling edges of both signals in an I2C +start condition happen faster, so we need a higher sampling frequency, e.g. +``-s 1500000`` for 1.5MHz. Also, we don't want to sample right away but wait +for a start condition on an idle bus. So, we need to set a trigger to a falling +edge on SDA while SCL stays high, i.e. ``-t 1H+2F``. Last is the duration, let +us assume 15ms here which results in the parameter ``-d 15000``. So, +altogether:: + + gpio-sloppy-logic-analyzer -s 1500000 -t 1H+2F -d 15000 + +Note that the process will return you back to the prompt but a sub-process is +still sampling in the background. Unless this has finished, you will not find a +result file in the current or specified directory. For the above example, we +will then need to trigger I2C communication:: + + i2cdetect -y -r <your bus number> + +Result is a .sr file to be consumed with PulseView or sigrok-cli from the free +`sigrok`_ project. It is a zip file which also contains the binary sample data +which may be consumed by other software. The filename is the logic analyzer +instance name plus a since-epoch timestamp. + +.. _sigrok: https://sigrok.org/ diff --git a/Documentation/dev-tools/index.rst b/Documentation/dev-tools/index.rst index 6b0663075dc0..4b8425e348ab 100644 --- a/Documentation/dev-tools/index.rst +++ b/Documentation/dev-tools/index.rst @@ -10,15 +10,16 @@ whole; patches welcome! A brief overview of testing-specific tools can be found in Documentation/dev-tools/testing-overview.rst -.. class:: toc-title - - Table of contents +Tools that are specific to debugging can be found in +Documentation/process/debugging/index.rst .. toctree:: + :caption: Table of contents :maxdepth: 2 testing-overview checkpatch + clang-format coccinelle sparse kcov @@ -28,12 +29,15 @@ Documentation/dev-tools/testing-overview.rst ubsan kmemleak kcsan + lkmm/index kfence - gdb-kernel-debugging - kgdb kselftest kunit/index ktap + checkuapi + gpio-sloppy-logic-analyzer + autofdo + propeller .. only:: subproject and html diff --git a/Documentation/dev-tools/kasan.rst b/Documentation/dev-tools/kasan.rst index 5c93ab915049..a034700da7c4 100644 --- a/Documentation/dev-tools/kasan.rst +++ b/Documentation/dev-tools/kasan.rst @@ -1,5 +1,8 @@ -The Kernel Address Sanitizer (KASAN) -==================================== +.. SPDX-License-Identifier: GPL-2.0 +.. Copyright (C) 2023, Google LLC. + +Kernel Address Sanitizer (KASAN) +================================ Overview -------- @@ -41,8 +44,8 @@ Support Architectures ~~~~~~~~~~~~~ -Generic KASAN is supported on x86_64, arm, arm64, powerpc, riscv, s390, and -xtensa, and the tag-based KASAN modes are supported only on arm64. +Generic KASAN is supported on x86_64, arm, arm64, powerpc, riscv, s390, xtensa, +and loongarch, and the tag-based KASAN modes are supported only on arm64. Compilers ~~~~~~~~~ @@ -107,9 +110,12 @@ effectively disables ``panic_on_warn`` for KASAN reports. Alternatively, independent of ``panic_on_warn``, the ``kasan.fault=`` boot parameter can be used to control panic and reporting behaviour: -- ``kasan.fault=report`` or ``=panic`` controls whether to only print a KASAN - report or also panic the kernel (default: ``report``). The panic happens even - if ``kasan_multi_shot`` is enabled. +- ``kasan.fault=report``, ``=panic``, or ``=panic_on_write`` controls whether + to only print a KASAN report, panic the kernel, or panic the kernel on + invalid writes only (default: ``report``). The panic happens even if + ``kasan_multi_shot`` is enabled. Note that when using asynchronous mode of + Hardware Tag-Based KASAN, ``kasan.fault=panic_on_write`` always panics on + asynchronously checked accesses (including reads). Software and Hardware Tag-Based KASAN modes (see the section about various modes below) support altering stack trace collection behavior: @@ -137,16 +143,36 @@ disabling KASAN altogether or controlling its features: Asymmetric mode: a bad access is detected synchronously on reads and asynchronously on writes. +- ``kasan.write_only=off`` or ``kasan.write_only=on`` controls whether KASAN + checks the write (store) accesses only or all accesses (default: ``off``). + - ``kasan.vmalloc=off`` or ``=on`` disables or enables tagging of vmalloc allocations (default: ``on``). +- ``kasan.page_alloc.sample=<sampling interval>`` makes KASAN tag only every + Nth page_alloc allocation with the order equal or greater than + ``kasan.page_alloc.sample.order``, where N is the value of the ``sample`` + parameter (default: ``1``, or tag every such allocation). + This parameter is intended to mitigate the performance overhead introduced + by KASAN. + Note that enabling this parameter makes Hardware Tag-Based KASAN skip checks + of allocations chosen by sampling and thus miss bad accesses to these + allocations. Use the default value for accurate bug detection. + +- ``kasan.page_alloc.sample.order=<minimum page order>`` specifies the minimum + order of allocations that are affected by sampling (default: ``3``). + Only applies when ``kasan.page_alloc.sample`` is set to a value greater + than ``1``. + This parameter is intended to allow sampling only large page_alloc + allocations, which is the biggest source of the performance overhead. + Error reports ~~~~~~~~~~~~~ A typical KASAN report looks like this:: ================================================================== - BUG: KASAN: slab-out-of-bounds in kmalloc_oob_right+0xa8/0xbc [test_kasan] + BUG: KASAN: slab-out-of-bounds in kmalloc_oob_right+0xa8/0xbc [kasan_test] Write of size 1 at addr ffff8801f44ec37b by task insmod/2760 CPU: 1 PID: 2760 Comm: insmod Not tainted 4.19.0-rc3+ #698 @@ -156,8 +182,8 @@ A typical KASAN report looks like this:: print_address_description+0x73/0x280 kasan_report+0x144/0x187 __asan_report_store1_noabort+0x17/0x20 - kmalloc_oob_right+0xa8/0xbc [test_kasan] - kmalloc_tests_init+0x16/0x700 [test_kasan] + kmalloc_oob_right+0xa8/0xbc [kasan_test] + kmalloc_tests_init+0x16/0x700 [kasan_test] do_one_initcall+0xa5/0x3ae do_init_module+0x1b6/0x547 load_module+0x75df/0x8070 @@ -177,8 +203,8 @@ A typical KASAN report looks like this:: save_stack+0x43/0xd0 kasan_kmalloc+0xa7/0xd0 kmem_cache_alloc_trace+0xe1/0x1b0 - kmalloc_oob_right+0x56/0xbc [test_kasan] - kmalloc_tests_init+0x16/0x700 [test_kasan] + kmalloc_oob_right+0x56/0xbc [kasan_test] + kmalloc_tests_init+0x16/0x700 [kasan_test] do_one_initcall+0xa5/0x3ae do_init_module+0x1b6/0x547 load_module+0x75df/0x8070 @@ -254,6 +280,27 @@ traces point to places in code that interacted with the object but that are not directly present in the bad access stack trace. Currently, this includes call_rcu() and workqueue queuing. +CONFIG_KASAN_EXTRA_INFO +~~~~~~~~~~~~~~~~~~~~~~~ + +Enabling CONFIG_KASAN_EXTRA_INFO allows KASAN to record and report more +information. The extra information currently supported is the CPU number and +timestamp at allocation and free. More information can help find the cause of +the bug and correlate the error with other system events, at the cost of using +extra memory to record more information (more cost details in the help text of +CONFIG_KASAN_EXTRA_INFO). + +Here is the report with CONFIG_KASAN_EXTRA_INFO enabled (only the +different parts are shown):: + + ================================================================== + ... + Allocated by task 134 on cpu 5 at 229.133855s: + ... + Freed by task 136 on cpu 3 at 230.199335s: + ... + ================================================================== + Implementation details ---------------------- @@ -467,19 +514,14 @@ Tests ~~~~~ There are KASAN tests that allow verifying that KASAN works and can detect -certain types of memory corruptions. The tests consist of two parts: +certain types of memory corruptions. -1. Tests that are integrated with the KUnit Test Framework. Enabled with -``CONFIG_KASAN_KUNIT_TEST``. These tests can be run and partially verified +All KASAN tests are integrated with the KUnit Test Framework and can be enabled +via ``CONFIG_KASAN_KUNIT_TEST``. The tests can be run and partially verified automatically in a few different ways; see the instructions below. -2. Tests that are currently incompatible with KUnit. Enabled with -``CONFIG_KASAN_MODULE_TEST`` and can only be run as a module. These tests can -only be verified manually by loading the kernel module and inspecting the -kernel log for KASAN reports. - -Each KUnit-compatible KASAN test prints one of multiple KASAN reports if an -error is detected. Then the test prints its number and status. +Each KASAN test prints one of multiple KASAN reports if an error is detected. +Then the test prints its number and status. When a test passes:: @@ -487,15 +529,15 @@ When a test passes:: When a test fails due to a failed ``kmalloc``:: - # kmalloc_large_oob_right: ASSERTION FAILED at lib/test_kasan.c:163 + # kmalloc_large_oob_right: ASSERTION FAILED at mm/kasan/kasan_test.c:245 Expected ptr is not null, but is - not ok 4 - kmalloc_large_oob_right + not ok 5 - kmalloc_large_oob_right When a test fails due to a missing KASAN report:: - # kmalloc_double_kzfree: EXPECTATION FAILED at lib/test_kasan.c:974 + # kmalloc_double_kzfree: EXPECTATION FAILED at mm/kasan/kasan_test.c:709 KASAN failure expected in "kfree_sensitive(ptr)", but none occurred - not ok 44 - kmalloc_double_kzfree + not ok 28 - kmalloc_double_kzfree At the end the cumulative status of all KASAN tests is printed. On success:: @@ -506,16 +548,16 @@ Or, if one of the tests failed:: not ok 1 - kasan -There are a few ways to run KUnit-compatible KASAN tests. +There are a few ways to run the KASAN tests. 1. Loadable module - With ``CONFIG_KUNIT`` enabled, KASAN-KUnit tests can be built as a loadable - module and run by loading ``test_kasan.ko`` with ``insmod`` or ``modprobe``. + With ``CONFIG_KUNIT`` enabled, the tests can be built as a loadable module + and run by loading ``kasan_test.ko`` with ``insmod`` or ``modprobe``. 2. Built-In - With ``CONFIG_KUNIT`` built-in, KASAN-KUnit tests can be built-in as well. + With ``CONFIG_KUNIT`` built-in, the tests can be built-in as well. In this case, the tests will run at boot as a late-init call. 3. Using kunit_tool diff --git a/Documentation/dev-tools/kcov.rst b/Documentation/dev-tools/kcov.rst index d83c9ab49427..8127849d40f5 100644 --- a/Documentation/dev-tools/kcov.rst +++ b/Documentation/dev-tools/kcov.rst @@ -1,42 +1,50 @@ -kcov: code coverage for fuzzing +KCOV: code coverage for fuzzing =============================== -kcov exposes kernel code coverage information in a form suitable for coverage- -guided fuzzing (randomized testing). Coverage data of a running kernel is -exported via the "kcov" debugfs file. Coverage collection is enabled on a task -basis, and thus it can capture precise coverage of a single system call. +KCOV collects and exposes kernel code coverage information in a form suitable +for coverage-guided fuzzing. Coverage data of a running kernel is exported via +the ``kcov`` debugfs file. Coverage collection is enabled on a task basis, and +thus KCOV can capture precise coverage of a single system call. -Note that kcov does not aim to collect as much coverage as possible. It aims -to collect more or less stable coverage that is function of syscall inputs. -To achieve this goal it does not collect coverage in soft/hard interrupts -and instrumentation of some inherently non-deterministic parts of kernel is -disabled (e.g. scheduler, locking). +Note that KCOV does not aim to collect as much coverage as possible. It aims +to collect more or less stable coverage that is a function of syscall inputs. +To achieve this goal, it does not collect coverage in soft/hard interrupts +(unless remove coverage collection is enabled, see below) and from some +inherently non-deterministic parts of the kernel (e.g. scheduler, locking). -kcov is also able to collect comparison operands from the instrumented code -(this feature currently requires that the kernel is compiled with clang). +Besides collecting code coverage, KCOV can also collect comparison operands. +See the "Comparison operands collection" section for details. + +Besides collecting coverage data from syscall handlers, KCOV can also collect +coverage for annotated parts of the kernel executing in background kernel +tasks or soft interrupts. See the "Remote coverage collection" section for +details. Prerequisites ------------- -Configure the kernel with:: +KCOV relies on compiler instrumentation and requires GCC 6.1.0 or later +or any Clang version supported by the kernel. - CONFIG_KCOV=y +Collecting comparison operands is supported with GCC 8+ or with Clang. -CONFIG_KCOV requires gcc 6.1.0 or later. +To enable KCOV, configure the kernel with:: -If the comparison operands need to be collected, set:: + CONFIG_KCOV=y + +To enable comparison operands collection, set:: CONFIG_KCOV_ENABLE_COMPARISONS=y -Profiling data will only become accessible once debugfs has been mounted:: +Coverage data only becomes accessible once debugfs has been mounted:: mount -t debugfs none /sys/kernel/debug Coverage collection ------------------- -The following program demonstrates coverage collection from within a test -program using kcov: +The following program demonstrates how to use KCOV to collect coverage for a +single syscall from within a test program: .. code-block:: c @@ -84,7 +92,7 @@ program using kcov: perror("ioctl"), exit(1); /* Reset coverage from the tail of the ioctl() call. */ __atomic_store_n(&cover[0], 0, __ATOMIC_RELAXED); - /* That's the target syscal call. */ + /* Call the target syscall call. */ read(-1, NULL, 0); /* Read number of PCs collected. */ n = __atomic_load_n(&cover[0], __ATOMIC_RELAXED); @@ -103,7 +111,7 @@ program using kcov: return 0; } -After piping through addr2line output of the program looks as follows:: +After piping through ``addr2line`` the output of the program looks as follows:: SyS_read fs/read_write.c:562 @@ -121,12 +129,13 @@ After piping through addr2line output of the program looks as follows:: fs/read_write.c:562 If a program needs to collect coverage from several threads (independently), -it needs to open /sys/kernel/debug/kcov in each thread separately. +it needs to open ``/sys/kernel/debug/kcov`` in each thread separately. The interface is fine-grained to allow efficient forking of test processes. -That is, a parent process opens /sys/kernel/debug/kcov, enables trace mode, -mmaps coverage buffer and then forks child processes in a loop. Child processes -only need to enable coverage (disable happens automatically on thread end). +That is, a parent process opens ``/sys/kernel/debug/kcov``, enables trace mode, +mmaps coverage buffer, and then forks child processes in a loop. The child +processes only need to enable coverage (it gets disabled automatically when +a thread exits). Comparison operands collection ------------------------------ @@ -205,52 +214,78 @@ Comparison operands collection is similar to coverage collection: return 0; } -Note that the kcov modes (coverage collection or comparison operands) are -mutually exclusive. +Note that the KCOV modes (collection of code coverage or comparison operands) +are mutually exclusive. Remote coverage collection -------------------------- -With KCOV_ENABLE coverage is collected only for syscalls that are issued -from the current process. With KCOV_REMOTE_ENABLE it's possible to collect -coverage for arbitrary parts of the kernel code, provided that those parts -are annotated with kcov_remote_start()/kcov_remote_stop(). - -This allows to collect coverage from two types of kernel background -threads: the global ones, that are spawned during kernel boot in a limited -number of instances (e.g. one USB hub_event() worker thread is spawned per -USB HCD); and the local ones, that are spawned when a user interacts with -some kernel interface (e.g. vhost workers); as well as from soft -interrupts. - -To enable collecting coverage from a global background thread or from a -softirq, a unique global handle must be assigned and passed to the -corresponding kcov_remote_start() call. Then a userspace process can pass -a list of such handles to the KCOV_REMOTE_ENABLE ioctl in the handles -array field of the kcov_remote_arg struct. This will attach the used kcov -device to the code sections, that are referenced by those handles. - -Since there might be many local background threads spawned from different -userspace processes, we can't use a single global handle per annotation. -Instead, the userspace process passes a non-zero handle through the -common_handle field of the kcov_remote_arg struct. This common handle gets -saved to the kcov_handle field in the current task_struct and needs to be -passed to the newly spawned threads via custom annotations. Those threads -should in turn be annotated with kcov_remote_start()/kcov_remote_stop(). - -Internally kcov stores handles as u64 integers. The top byte of a handle -is used to denote the id of a subsystem that this handle belongs to, and -the lower 4 bytes are used to denote the id of a thread instance within -that subsystem. A reserved value 0 is used as a subsystem id for common -handles as they don't belong to a particular subsystem. The bytes 4-7 are -currently reserved and must be zero. In the future the number of bytes -used for the subsystem or handle ids might be increased. - -When a particular userspace process collects coverage via a common -handle, kcov will collect coverage for each code section that is annotated -to use the common handle obtained as kcov_handle from the current -task_struct. However non common handles allow to collect coverage -selectively from different subsystems. +Besides collecting coverage data from handlers of syscalls issued from a +userspace process, KCOV can also collect coverage for parts of the kernel +executing in other contexts - so-called "remote" coverage. + +Using KCOV to collect remote coverage requires: + +1. Modifying kernel code to annotate the code section from where coverage + should be collected with ``kcov_remote_start`` and ``kcov_remote_stop``. + +2. Using ``KCOV_REMOTE_ENABLE`` instead of ``KCOV_ENABLE`` in the userspace + process that collects coverage. + +Both ``kcov_remote_start`` and ``kcov_remote_stop`` annotations and the +``KCOV_REMOTE_ENABLE`` ioctl accept handles that identify particular coverage +collection sections. The way a handle is used depends on the context where the +matching code section executes. + +KCOV supports collecting remote coverage from the following contexts: + +1. Global kernel background tasks. These are the tasks that are spawned during + kernel boot in a limited number of instances (e.g. one USB ``hub_event`` + worker is spawned per one USB HCD). + +2. Local kernel background tasks. These are spawned when a userspace process + interacts with some kernel interface and are usually killed when the process + exits (e.g. vhost workers). + +3. Soft interrupts. + +For #1 and #3, a unique global handle must be chosen and passed to the +corresponding ``kcov_remote_start`` call. Then a userspace process must pass +this handle to ``KCOV_REMOTE_ENABLE`` in the ``handles`` array field of the +``kcov_remote_arg`` struct. This will attach the used KCOV device to the code +section referenced by this handle. Multiple global handles identifying +different code sections can be passed at once. + +For #2, the userspace process instead must pass a non-zero handle through the +``common_handle`` field of the ``kcov_remote_arg`` struct. This common handle +gets saved to the ``kcov_handle`` field in the current ``task_struct`` and +needs to be passed to the newly spawned local tasks via custom kernel code +modifications. Those tasks should in turn use the passed handle in their +``kcov_remote_start`` and ``kcov_remote_stop`` annotations. + +KCOV follows a predefined format for both global and common handles. Each +handle is a ``u64`` integer. Currently, only the one top and the lower 4 bytes +are used. Bytes 4-7 are reserved and must be zero. + +For global handles, the top byte of the handle denotes the id of a subsystem +this handle belongs to. For example, KCOV uses ``1`` as the USB subsystem id. +The lower 4 bytes of a global handle denote the id of a task instance within +that subsystem. For example, each ``hub_event`` worker uses the USB bus number +as the task instance id. + +For common handles, a reserved value ``0`` is used as a subsystem id, as such +handles don't belong to a particular subsystem. The lower 4 bytes of a common +handle identify a collective instance of all local tasks spawned by the +userspace process that passed a common handle to ``KCOV_REMOTE_ENABLE``. + +In practice, any value can be used for common handle instance id if coverage +is only collected from a single userspace process on the system. However, if +common handles are used by multiple processes, unique instance ids must be +used for each process. One option is to use the process id as the common +handle instance id. + +The following program demonstrates using KCOV to collect coverage from both +local tasks spawned by the process and the global task that handles USB bus #1: .. code-block:: c @@ -326,7 +361,12 @@ selectively from different subsystems. */ sleep(2); - n = __atomic_load_n(&cover[0], __ATOMIC_RELAXED); + /* + * The load to the coverage count should be an acquire to pair with + * pair with the corresponding write memory barrier (smp_wmb()) on + * the kernel-side in kcov_move_area(). + */ + n = __atomic_load_n(&cover[0], __ATOMIC_ACQUIRE); for (i = 0; i < n; i++) printf("0x%lx\n", cover[i + 1]); if (ioctl(fd, KCOV_DISABLE, 0)) diff --git a/Documentation/dev-tools/kcsan.rst b/Documentation/dev-tools/kcsan.rst index 3ae866dcc924..8575178aa87f 100644 --- a/Documentation/dev-tools/kcsan.rst +++ b/Documentation/dev-tools/kcsan.rst @@ -1,8 +1,8 @@ .. SPDX-License-Identifier: GPL-2.0 .. Copyright (C) 2019, Google LLC. -The Kernel Concurrency Sanitizer (KCSAN) -======================================== +Kernel Concurrency Sanitizer (KCSAN) +==================================== The Kernel Concurrency Sanitizer (KCSAN) is a dynamic race detector, which relies on compile-time instrumentation, and uses a watchpoint-based sampling @@ -91,6 +91,16 @@ the below options are available: behaviour when encountering a data race is deemed safe. Please see `"Marking Shared-Memory Accesses" in the LKMM`_ for more information. +* Similar to ``data_race(...)``, the type qualifier ``__data_racy`` can be used + to document that all data races due to accesses to a variable are intended + and should be ignored by KCSAN:: + + struct foo { + ... + int __data_racy stats_counter; + ... + }; + * Disabling data race detection for entire functions can be accomplished by using the function attribute ``__no_kcsan``:: @@ -193,7 +203,7 @@ they happen concurrently in different threads, and at least one of them is a least one is a write. For a more thorough discussion and definition, see `"Plain Accesses and Data Races" in the LKMM`_. -.. _"Plain Accesses and Data Races" in the LKMM: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/tools/memory-model/Documentation/explanation.txt#n1922 +.. _"Plain Accesses and Data Races" in the LKMM: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/tools/memory-model/Documentation/explanation.txt?id=8f6629c004b193d23612641c3607e785819e97ab#n2164 Relationship with the Linux-Kernel Memory Consistency Model (LKMM) ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ @@ -351,7 +361,8 @@ Alternatives Considered ----------------------- An alternative data race detection approach for the kernel can be found in the -`Kernel Thread Sanitizer (KTSAN) <https://github.com/google/ktsan/wiki>`_. +`Kernel Thread Sanitizer (KTSAN) +<https://github.com/google/kernel-sanitizers/blob/master/KTSAN.md>`_. KTSAN is a happens-before data race detector, which explicitly establishes the happens-before order between memory operations, which can then be used to determine data races as defined in `Data Races`_. diff --git a/Documentation/dev-tools/kfence.rst b/Documentation/dev-tools/kfence.rst index 936f6aaa75c8..541899353865 100644 --- a/Documentation/dev-tools/kfence.rst +++ b/Documentation/dev-tools/kfence.rst @@ -53,6 +53,13 @@ configurable via the Kconfig option ``CONFIG_KFENCE_DEFERRABLE``. The KUnit test suite is very likely to fail when using a deferrable timer since it currently causes very unpredictable sample intervals. +By default KFENCE will only sample 1 heap allocation within each sample +interval. *Burst mode* allows to sample successive heap allocations, where the +kernel boot parameter ``kfence.burst`` can be set to a non-zero value which +denotes the *additional* successive allocations within a sample interval; +setting ``kfence.burst=N`` means that ``1 + N`` successive allocations are +attempted through KFENCE for each sample interval. + The KFENCE memory pool is of fixed size, and if the pool is exhausted, no further KFENCE allocations occur. With ``CONFIG_KFENCE_NUM_OBJECTS`` (default 255), the number of available guarded objects can be controlled. Each object diff --git a/Documentation/dev-tools/kgdb.rst b/Documentation/dev-tools/kgdb.rst deleted file mode 100644 index f83ba2601e55..000000000000 --- a/Documentation/dev-tools/kgdb.rst +++ /dev/null @@ -1,939 +0,0 @@ -================================================= -Using kgdb, kdb and the kernel debugger internals -================================================= - -:Author: Jason Wessel - -Introduction -============ - -The kernel has two different debugger front ends (kdb and kgdb) which -interface to the debug core. It is possible to use either of the -debugger front ends and dynamically transition between them if you -configure the kernel properly at compile and runtime. - -Kdb is simplistic shell-style interface which you can use on a system -console with a keyboard or serial console. You can use it to inspect -memory, registers, process lists, dmesg, and even set breakpoints to -stop in a certain location. Kdb is not a source level debugger, although -you can set breakpoints and execute some basic kernel run control. Kdb -is mainly aimed at doing some analysis to aid in development or -diagnosing kernel problems. You can access some symbols by name in -kernel built-ins or in kernel modules if the code was built with -``CONFIG_KALLSYMS``. - -Kgdb is intended to be used as a source level debugger for the Linux -kernel. It is used along with gdb to debug a Linux kernel. The -expectation is that gdb can be used to "break in" to the kernel to -inspect memory, variables and look through call stack information -similar to the way an application developer would use gdb to debug an -application. It is possible to place breakpoints in kernel code and -perform some limited execution stepping. - -Two machines are required for using kgdb. One of these machines is a -development machine and the other is the target machine. The kernel to -be debugged runs on the target machine. The development machine runs an -instance of gdb against the vmlinux file which contains the symbols (not -a boot image such as bzImage, zImage, uImage...). In gdb the developer -specifies the connection parameters and connects to kgdb. The type of -connection a developer makes with gdb depends on the availability of -kgdb I/O modules compiled as built-ins or loadable kernel modules in the -test machine's kernel. - -Compiling a kernel -================== - -- In order to enable compilation of kdb, you must first enable kgdb. - -- The kgdb test compile options are described in the kgdb test suite - chapter. - -Kernel config options for kgdb ------------------------------- - -To enable ``CONFIG_KGDB`` you should look under -:menuselection:`Kernel hacking --> Kernel debugging` and select -:menuselection:`KGDB: kernel debugger`. - -While it is not a hard requirement that you have symbols in your vmlinux -file, gdb tends not to be very useful without the symbolic data, so you -will want to turn on ``CONFIG_DEBUG_INFO`` which is called -:menuselection:`Compile the kernel with debug info` in the config menu. - -It is advised, but not required, that you turn on the -``CONFIG_FRAME_POINTER`` kernel option which is called :menuselection:`Compile -the kernel with frame pointers` in the config menu. This option inserts code -into the compiled executable which saves the frame information in registers -or on the stack at different points which allows a debugger such as gdb to -more accurately construct stack back traces while debugging the kernel. - -If the architecture that you are using supports the kernel option -``CONFIG_STRICT_KERNEL_RWX``, you should consider turning it off. This -option will prevent the use of software breakpoints because it marks -certain regions of the kernel's memory space as read-only. If kgdb -supports it for the architecture you are using, you can use hardware -breakpoints if you desire to run with the ``CONFIG_STRICT_KERNEL_RWX`` -option turned on, else you need to turn off this option. - -Next you should choose one of more I/O drivers to interconnect debugging -host and debugged target. Early boot debugging requires a KGDB I/O -driver that supports early debugging and the driver must be built into -the kernel directly. Kgdb I/O driver configuration takes place via -kernel or module parameters which you can learn more about in the in the -section that describes the parameter kgdboc. - -Here is an example set of ``.config`` symbols to enable or disable for kgdb:: - - # CONFIG_STRICT_KERNEL_RWX is not set - CONFIG_FRAME_POINTER=y - CONFIG_KGDB=y - CONFIG_KGDB_SERIAL_CONSOLE=y - -Kernel config options for kdb ------------------------------ - -Kdb is quite a bit more complex than the simple gdbstub sitting on top -of the kernel's debug core. Kdb must implement a shell, and also adds -some helper functions in other parts of the kernel, responsible for -printing out interesting data such as what you would see if you ran -``lsmod``, or ``ps``. In order to build kdb into the kernel you follow the -same steps as you would for kgdb. - -The main config option for kdb is ``CONFIG_KGDB_KDB`` which is called -:menuselection:`KGDB_KDB: include kdb frontend for kgdb` in the config menu. -In theory you would have already also selected an I/O driver such as the -``CONFIG_KGDB_SERIAL_CONSOLE`` interface if you plan on using kdb on a -serial port, when you were configuring kgdb. - -If you want to use a PS/2-style keyboard with kdb, you would select -``CONFIG_KDB_KEYBOARD`` which is called :menuselection:`KGDB_KDB: keyboard as -input device` in the config menu. The ``CONFIG_KDB_KEYBOARD`` option is not -used for anything in the gdb interface to kgdb. The ``CONFIG_KDB_KEYBOARD`` -option only works with kdb. - -Here is an example set of ``.config`` symbols to enable/disable kdb:: - - # CONFIG_STRICT_KERNEL_RWX is not set - CONFIG_FRAME_POINTER=y - CONFIG_KGDB=y - CONFIG_KGDB_SERIAL_CONSOLE=y - CONFIG_KGDB_KDB=y - CONFIG_KDB_KEYBOARD=y - -Kernel Debugger Boot Arguments -============================== - -This section describes the various runtime kernel parameters that affect -the configuration of the kernel debugger. The following chapter covers -using kdb and kgdb as well as providing some examples of the -configuration parameters. - -Kernel parameter: kgdboc ------------------------- - -The kgdboc driver was originally an abbreviation meant to stand for -"kgdb over console". Today it is the primary mechanism to configure how -to communicate from gdb to kgdb as well as the devices you want to use -to interact with the kdb shell. - -For kgdb/gdb, kgdboc is designed to work with a single serial port. It -is intended to cover the circumstance where you want to use a serial -console as your primary console as well as using it to perform kernel -debugging. It is also possible to use kgdb on a serial port which is not -designated as a system console. Kgdboc may be configured as a kernel -built-in or a kernel loadable module. You can only make use of -``kgdbwait`` and early debugging if you build kgdboc into the kernel as -a built-in. - -Optionally you can elect to activate kms (Kernel Mode Setting) -integration. When you use kms with kgdboc and you have a video driver -that has atomic mode setting hooks, it is possible to enter the debugger -on the graphics console. When the kernel execution is resumed, the -previous graphics mode will be restored. This integration can serve as a -useful tool to aid in diagnosing crashes or doing analysis of memory -with kdb while allowing the full graphics console applications to run. - -kgdboc arguments -~~~~~~~~~~~~~~~~ - -Usage:: - - kgdboc=[kms][[,]kbd][[,]serial_device][,baud] - -The order listed above must be observed if you use any of the optional -configurations together. - -Abbreviations: - -- kms = Kernel Mode Setting - -- kbd = Keyboard - -You can configure kgdboc to use the keyboard, and/or a serial device -depending on if you are using kdb and/or kgdb, in one of the following -scenarios. The order listed above must be observed if you use any of the -optional configurations together. Using kms + only gdb is generally not -a useful combination. - -Using loadable module or built-in -^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ - -1. As a kernel built-in: - - Use the kernel boot argument:: - - kgdboc=<tty-device>,[baud] - -2. As a kernel loadable module: - - Use the command:: - - modprobe kgdboc kgdboc=<tty-device>,[baud] - - Here are two examples of how you might format the kgdboc string. The - first is for an x86 target using the first serial port. The second - example is for the ARM Versatile AB using the second serial port. - - 1. ``kgdboc=ttyS0,115200`` - - 2. ``kgdboc=ttyAMA1,115200`` - -Configure kgdboc at runtime with sysfs -^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ - -At run time you can enable or disable kgdboc by echoing a parameters -into the sysfs. Here are two examples: - -1. Enable kgdboc on ttyS0:: - - echo ttyS0 > /sys/module/kgdboc/parameters/kgdboc - -2. Disable kgdboc:: - - echo "" > /sys/module/kgdboc/parameters/kgdboc - -.. note:: - - You do not need to specify the baud if you are configuring the - console on tty which is already configured or open. - -More examples -^^^^^^^^^^^^^ - -You can configure kgdboc to use the keyboard, and/or a serial device -depending on if you are using kdb and/or kgdb, in one of the following -scenarios. - -1. kdb and kgdb over only a serial port:: - - kgdboc=<serial_device>[,baud] - - Example:: - - kgdboc=ttyS0,115200 - -2. kdb and kgdb with keyboard and a serial port:: - - kgdboc=kbd,<serial_device>[,baud] - - Example:: - - kgdboc=kbd,ttyS0,115200 - -3. kdb with a keyboard:: - - kgdboc=kbd - -4. kdb with kernel mode setting:: - - kgdboc=kms,kbd - -5. kdb with kernel mode setting and kgdb over a serial port:: - - kgdboc=kms,kbd,ttyS0,115200 - -.. note:: - - Kgdboc does not support interrupting the target via the gdb remote - protocol. You must manually send a :kbd:`SysRq-G` unless you have a proxy - that splits console output to a terminal program. A console proxy has a - separate TCP port for the debugger and a separate TCP port for the - "human" console. The proxy can take care of sending the :kbd:`SysRq-G` - for you. - -When using kgdboc with no debugger proxy, you can end up connecting the -debugger at one of two entry points. If an exception occurs after you -have loaded kgdboc, a message should print on the console stating it is -waiting for the debugger. In this case you disconnect your terminal -program and then connect the debugger in its place. If you want to -interrupt the target system and forcibly enter a debug session you have -to issue a :kbd:`Sysrq` sequence and then type the letter :kbd:`g`. Then you -disconnect the terminal session and connect gdb. Your options if you -don't like this are to hack gdb to send the :kbd:`SysRq-G` for you as well as -on the initial connect, or to use a debugger proxy that allows an -unmodified gdb to do the debugging. - -Kernel parameter: ``kgdboc_earlycon`` -------------------------------------- - -If you specify the kernel parameter ``kgdboc_earlycon`` and your serial -driver registers a boot console that supports polling (doesn't need -interrupts and implements a nonblocking read() function) kgdb will attempt -to work using the boot console until it can transition to the regular -tty driver specified by the ``kgdboc`` parameter. - -Normally there is only one boot console (especially that implements the -read() function) so just adding ``kgdboc_earlycon`` on its own is -sufficient to make this work. If you have more than one boot console you -can add the boot console's name to differentiate. Note that names that -are registered through the boot console layer and the tty layer are not -the same for the same port. - -For instance, on one board to be explicit you might do:: - - kgdboc_earlycon=qcom_geni kgdboc=ttyMSM0 - -If the only boot console on the device was "qcom_geni", you could simplify:: - - kgdboc_earlycon kgdboc=ttyMSM0 - -Kernel parameter: ``kgdbwait`` ------------------------------- - -The Kernel command line option ``kgdbwait`` makes kgdb wait for a -debugger connection during booting of a kernel. You can only use this -option if you compiled a kgdb I/O driver into the kernel and you -specified the I/O driver configuration as a kernel command line option. -The kgdbwait parameter should always follow the configuration parameter -for the kgdb I/O driver in the kernel command line else the I/O driver -will not be configured prior to asking the kernel to use it to wait. - -The kernel will stop and wait as early as the I/O driver and -architecture allows when you use this option. If you build the kgdb I/O -driver as a loadable kernel module kgdbwait will not do anything. - -Kernel parameter: ``kgdbcon`` ------------------------------ - -The ``kgdbcon`` feature allows you to see printk() messages inside gdb -while gdb is connected to the kernel. Kdb does not make use of the kgdbcon -feature. - -Kgdb supports using the gdb serial protocol to send console messages to -the debugger when the debugger is connected and running. There are two -ways to activate this feature. - -1. Activate with the kernel command line option:: - - kgdbcon - -2. Use sysfs before configuring an I/O driver:: - - echo 1 > /sys/module/kgdb/parameters/kgdb_use_con - -.. note:: - - If you do this after you configure the kgdb I/O driver, the - setting will not take effect until the next point the I/O is - reconfigured. - -.. important:: - - You cannot use kgdboc + kgdbcon on a tty that is an - active system console. An example of incorrect usage is:: - - console=ttyS0,115200 kgdboc=ttyS0 kgdbcon - -It is possible to use this option with kgdboc on a tty that is not a -system console. - -Run time parameter: ``kgdbreboot`` ----------------------------------- - -The kgdbreboot feature allows you to change how the debugger deals with -the reboot notification. You have 3 choices for the behavior. The -default behavior is always set to 0. - -.. tabularcolumns:: |p{0.4cm}|p{11.5cm}|p{5.6cm}| - -.. flat-table:: - :widths: 1 10 8 - - * - 1 - - ``echo -1 > /sys/module/debug_core/parameters/kgdbreboot`` - - Ignore the reboot notification entirely. - - * - 2 - - ``echo 0 > /sys/module/debug_core/parameters/kgdbreboot`` - - Send the detach message to any attached debugger client. - - * - 3 - - ``echo 1 > /sys/module/debug_core/parameters/kgdbreboot`` - - Enter the debugger on reboot notify. - -Kernel parameter: ``nokaslr`` ------------------------------ - -If the architecture that you are using enable KASLR by default, -you should consider turning it off. KASLR randomizes the -virtual address where the kernel image is mapped and confuse -gdb which resolve kernel symbol address from symbol table -of vmlinux. - -Using kdb -========= - -Quick start for kdb on a serial port ------------------------------------- - -This is a quick example of how to use kdb. - -1. Configure kgdboc at boot using kernel parameters:: - - console=ttyS0,115200 kgdboc=ttyS0,115200 nokaslr - - OR - - Configure kgdboc after the kernel has booted; assuming you are using - a serial port console:: - - echo ttyS0 > /sys/module/kgdboc/parameters/kgdboc - -2. Enter the kernel debugger manually or by waiting for an oops or - fault. There are several ways you can enter the kernel debugger - manually; all involve using the :kbd:`SysRq-G`, which means you must have - enabled ``CONFIG_MAGIC_SYSRQ=y`` in your kernel config. - - - When logged in as root or with a super user session you can run:: - - echo g > /proc/sysrq-trigger - - - Example using minicom 2.2 - - Press: :kbd:`CTRL-A` :kbd:`f` :kbd:`g` - - - When you have telneted to a terminal server that supports sending - a remote break - - Press: :kbd:`CTRL-]` - - Type in: ``send break`` - - Press: :kbd:`Enter` :kbd:`g` - -3. From the kdb prompt you can run the ``help`` command to see a complete - list of the commands that are available. - - Some useful commands in kdb include: - - =========== ================================================================= - ``lsmod`` Shows where kernel modules are loaded - ``ps`` Displays only the active processes - ``ps A`` Shows all the processes - ``summary`` Shows kernel version info and memory usage - ``bt`` Get a backtrace of the current process using dump_stack() - ``dmesg`` View the kernel syslog buffer - ``go`` Continue the system - =========== ================================================================= - -4. When you are done using kdb you need to consider rebooting the system - or using the ``go`` command to resuming normal kernel execution. If you - have paused the kernel for a lengthy period of time, applications - that rely on timely networking or anything to do with real wall clock - time could be adversely affected, so you should take this into - consideration when using the kernel debugger. - -Quick start for kdb using a keyboard connected console ------------------------------------------------------- - -This is a quick example of how to use kdb with a keyboard. - -1. Configure kgdboc at boot using kernel parameters:: - - kgdboc=kbd - - OR - - Configure kgdboc after the kernel has booted:: - - echo kbd > /sys/module/kgdboc/parameters/kgdboc - -2. Enter the kernel debugger manually or by waiting for an oops or - fault. There are several ways you can enter the kernel debugger - manually; all involve using the :kbd:`SysRq-G`, which means you must have - enabled ``CONFIG_MAGIC_SYSRQ=y`` in your kernel config. - - - When logged in as root or with a super user session you can run:: - - echo g > /proc/sysrq-trigger - - - Example using a laptop keyboard: - - Press and hold down: :kbd:`Alt` - - Press and hold down: :kbd:`Fn` - - Press and release the key with the label: :kbd:`SysRq` - - Release: :kbd:`Fn` - - Press and release: :kbd:`g` - - Release: :kbd:`Alt` - - - Example using a PS/2 101-key keyboard - - Press and hold down: :kbd:`Alt` - - Press and release the key with the label: :kbd:`SysRq` - - Press and release: :kbd:`g` - - Release: :kbd:`Alt` - -3. Now type in a kdb command such as ``help``, ``dmesg``, ``bt`` or ``go`` to - continue kernel execution. - -Using kgdb / gdb -================ - -In order to use kgdb you must activate it by passing configuration -information to one of the kgdb I/O drivers. If you do not pass any -configuration information kgdb will not do anything at all. Kgdb will -only actively hook up to the kernel trap hooks if a kgdb I/O driver is -loaded and configured. If you unconfigure a kgdb I/O driver, kgdb will -unregister all the kernel hook points. - -All kgdb I/O drivers can be reconfigured at run time, if -``CONFIG_SYSFS`` and ``CONFIG_MODULES`` are enabled, by echo'ing a new -config string to ``/sys/module/<driver>/parameter/<option>``. The driver -can be unconfigured by passing an empty string. You cannot change the -configuration while the debugger is attached. Make sure to detach the -debugger with the ``detach`` command prior to trying to unconfigure a -kgdb I/O driver. - -Connecting with gdb to a serial port ------------------------------------- - -1. Configure kgdboc - - Configure kgdboc at boot using kernel parameters:: - - kgdboc=ttyS0,115200 - - OR - - Configure kgdboc after the kernel has booted:: - - echo ttyS0 > /sys/module/kgdboc/parameters/kgdboc - -2. Stop kernel execution (break into the debugger) - - In order to connect to gdb via kgdboc, the kernel must first be - stopped. There are several ways to stop the kernel which include - using kgdbwait as a boot argument, via a :kbd:`SysRq-G`, or running the - kernel until it takes an exception where it waits for the debugger to - attach. - - - When logged in as root or with a super user session you can run:: - - echo g > /proc/sysrq-trigger - - - Example using minicom 2.2 - - Press: :kbd:`CTRL-A` :kbd:`f` :kbd:`g` - - - When you have telneted to a terminal server that supports sending - a remote break - - Press: :kbd:`CTRL-]` - - Type in: ``send break`` - - Press: :kbd:`Enter` :kbd:`g` - -3. Connect from gdb - - Example (using a directly connected port):: - - % gdb ./vmlinux - (gdb) set serial baud 115200 - (gdb) target remote /dev/ttyS0 - - - Example (kgdb to a terminal server on TCP port 2012):: - - % gdb ./vmlinux - (gdb) target remote 192.168.2.2:2012 - - - Once connected, you can debug a kernel the way you would debug an - application program. - - If you are having problems connecting or something is going seriously - wrong while debugging, it will most often be the case that you want - to enable gdb to be verbose about its target communications. You do - this prior to issuing the ``target remote`` command by typing in:: - - set debug remote 1 - -Remember if you continue in gdb, and need to "break in" again, you need -to issue an other :kbd:`SysRq-G`. It is easy to create a simple entry point by -putting a breakpoint at ``sys_sync`` and then you can run ``sync`` from a -shell or script to break into the debugger. - -kgdb and kdb interoperability -============================= - -It is possible to transition between kdb and kgdb dynamically. The debug -core will remember which you used the last time and automatically start -in the same mode. - -Switching between kdb and kgdb ------------------------------- - -Switching from kgdb to kdb -~~~~~~~~~~~~~~~~~~~~~~~~~~ - -There are two ways to switch from kgdb to kdb: you can use gdb to issue -a maintenance packet, or you can blindly type the command ``$3#33``. -Whenever the kernel debugger stops in kgdb mode it will print the -message ``KGDB or $3#33 for KDB``. It is important to note that you have -to type the sequence correctly in one pass. You cannot type a backspace -or delete because kgdb will interpret that as part of the debug stream. - -1. Change from kgdb to kdb by blindly typing:: - - $3#33 - -2. Change from kgdb to kdb with gdb:: - - maintenance packet 3 - - .. note:: - - Now you must kill gdb. Typically you press :kbd:`CTRL-Z` and issue - the command:: - - kill -9 % - -Change from kdb to kgdb -~~~~~~~~~~~~~~~~~~~~~~~ - -There are two ways you can change from kdb to kgdb. You can manually -enter kgdb mode by issuing the kgdb command from the kdb shell prompt, -or you can connect gdb while the kdb shell prompt is active. The kdb -shell looks for the typical first commands that gdb would issue with the -gdb remote protocol and if it sees one of those commands it -automatically changes into kgdb mode. - -1. From kdb issue the command:: - - kgdb - - Now disconnect your terminal program and connect gdb in its place - -2. At the kdb prompt, disconnect the terminal program and connect gdb in - its place. - -Running kdb commands from gdb ------------------------------ - -It is possible to run a limited set of kdb commands from gdb, using the -gdb monitor command. You don't want to execute any of the run control or -breakpoint operations, because it can disrupt the state of the kernel -debugger. You should be using gdb for breakpoints and run control -operations if you have gdb connected. The more useful commands to run -are things like lsmod, dmesg, ps or possibly some of the memory -information commands. To see all the kdb commands you can run -``monitor help``. - -Example:: - - (gdb) monitor ps - 1 idle process (state I) and - 27 sleeping system daemon (state M) processes suppressed, - use 'ps A' to see all. - Task Addr Pid Parent [*] cpu State Thread Command - - 0xc78291d0 1 0 0 0 S 0xc7829404 init - 0xc7954150 942 1 0 0 S 0xc7954384 dropbear - 0xc78789c0 944 1 0 0 S 0xc7878bf4 sh - (gdb) - -kgdb Test Suite -=============== - -When kgdb is enabled in the kernel config you can also elect to enable -the config parameter ``KGDB_TESTS``. Turning this on will enable a special -kgdb I/O module which is designed to test the kgdb internal functions. - -The kgdb tests are mainly intended for developers to test the kgdb -internals as well as a tool for developing a new kgdb architecture -specific implementation. These tests are not really for end users of the -Linux kernel. The primary source of documentation would be to look in -the ``drivers/misc/kgdbts.c`` file. - -The kgdb test suite can also be configured at compile time to run the -core set of tests by setting the kernel config parameter -``KGDB_TESTS_ON_BOOT``. This particular option is aimed at automated -regression testing and does not require modifying the kernel boot config -arguments. If this is turned on, the kgdb test suite can be disabled by -specifying ``kgdbts=`` as a kernel boot argument. - -Kernel Debugger Internals -========================= - -Architecture Specifics ----------------------- - -The kernel debugger is organized into a number of components: - -1. The debug core - - The debug core is found in ``kernel/debugger/debug_core.c``. It - contains: - - - A generic OS exception handler which includes sync'ing the - processors into a stopped state on an multi-CPU system. - - - The API to talk to the kgdb I/O drivers - - - The API to make calls to the arch-specific kgdb implementation - - - The logic to perform safe memory reads and writes to memory while - using the debugger - - - A full implementation for software breakpoints unless overridden - by the arch - - - The API to invoke either the kdb or kgdb frontend to the debug - core. - - - The structures and callback API for atomic kernel mode setting. - - .. note:: kgdboc is where the kms callbacks are invoked. - -2. kgdb arch-specific implementation - - This implementation is generally found in ``arch/*/kernel/kgdb.c``. As - an example, ``arch/x86/kernel/kgdb.c`` contains the specifics to - implement HW breakpoint as well as the initialization to dynamically - register and unregister for the trap handlers on this architecture. - The arch-specific portion implements: - - - contains an arch-specific trap catcher which invokes - kgdb_handle_exception() to start kgdb about doing its work - - - translation to and from gdb specific packet format to struct pt_regs - - - Registration and unregistration of architecture specific trap - hooks - - - Any special exception handling and cleanup - - - NMI exception handling and cleanup - - - (optional) HW breakpoints - -3. gdbstub frontend (aka kgdb) - - The gdbstub is located in ``kernel/debug/gdbstub.c``. It contains: - - - All the logic to implement the gdb serial protocol - -4. kdb frontend - - The kdb debugger shell is broken down into a number of components. - The kdb core is located in kernel/debug/kdb. There are a number of - helper functions in some of the other kernel components to make it - possible for kdb to examine and report information about the kernel - without taking locks that could cause a kernel deadlock. The kdb core - contains implements the following functionality. - - - A simple shell - - - The kdb core command set - - - A registration API to register additional kdb shell commands. - - - A good example of a self-contained kdb module is the ``ftdump`` - command for dumping the ftrace buffer. See: - ``kernel/trace/trace_kdb.c`` - - - For an example of how to dynamically register a new kdb command - you can build the kdb_hello.ko kernel module from - ``samples/kdb/kdb_hello.c``. To build this example you can set - ``CONFIG_SAMPLES=y`` and ``CONFIG_SAMPLE_KDB=m`` in your kernel - config. Later run ``modprobe kdb_hello`` and the next time you - enter the kdb shell, you can run the ``hello`` command. - - - The implementation for kdb_printf() which emits messages directly - to I/O drivers, bypassing the kernel log. - - - SW / HW breakpoint management for the kdb shell - -5. kgdb I/O driver - - Each kgdb I/O driver has to provide an implementation for the - following: - - - configuration via built-in or module - - - dynamic configuration and kgdb hook registration calls - - - read and write character interface - - - A cleanup handler for unconfiguring from the kgdb core - - - (optional) Early debug methodology - - Any given kgdb I/O driver has to operate very closely with the - hardware and must do it in such a way that does not enable interrupts - or change other parts of the system context without completely - restoring them. The kgdb core will repeatedly "poll" a kgdb I/O - driver for characters when it needs input. The I/O driver is expected - to return immediately if there is no data available. Doing so allows - for the future possibility to touch watchdog hardware in such a way - as to have a target system not reset when these are enabled. - -If you are intent on adding kgdb architecture specific support for a new -architecture, the architecture should define ``HAVE_ARCH_KGDB`` in the -architecture specific Kconfig file. This will enable kgdb for the -architecture, and at that point you must create an architecture specific -kgdb implementation. - -There are a few flags which must be set on every architecture in their -``asm/kgdb.h`` file. These are: - -- ``NUMREGBYTES``: - The size in bytes of all of the registers, so that we - can ensure they will all fit into a packet. - -- ``BUFMAX``: - The size in bytes of the buffer GDB will read into. This must - be larger than NUMREGBYTES. - -- ``CACHE_FLUSH_IS_SAFE``: - Set to 1 if it is always safe to call - flush_cache_range or flush_icache_range. On some architectures, - these functions may not be safe to call on SMP since we keep other - CPUs in a holding pattern. - -There are also the following functions for the common backend, found in -``kernel/kgdb.c``, that must be supplied by the architecture-specific -backend unless marked as (optional), in which case a default function -maybe used if the architecture does not need to provide a specific -implementation. - -.. kernel-doc:: include/linux/kgdb.h - :internal: - -kgdboc internals ----------------- - -kgdboc and uarts -~~~~~~~~~~~~~~~~ - -The kgdboc driver is actually a very thin driver that relies on the -underlying low level to the hardware driver having "polling hooks" to -which the tty driver is attached. In the initial implementation of -kgdboc the serial_core was changed to expose a low level UART hook for -doing polled mode reading and writing of a single character while in an -atomic context. When kgdb makes an I/O request to the debugger, kgdboc -invokes a callback in the serial core which in turn uses the callback in -the UART driver. - -When using kgdboc with a UART, the UART driver must implement two -callbacks in the struct uart_ops. -Example from ``drivers/8250.c``:: - - - #ifdef CONFIG_CONSOLE_POLL - .poll_get_char = serial8250_get_poll_char, - .poll_put_char = serial8250_put_poll_char, - #endif - - -Any implementation specifics around creating a polling driver use the -``#ifdef CONFIG_CONSOLE_POLL``, as shown above. Keep in mind that -polling hooks have to be implemented in such a way that they can be -called from an atomic context and have to restore the state of the UART -chip on return such that the system can return to normal when the -debugger detaches. You need to be very careful with any kind of lock you -consider, because failing here is most likely going to mean pressing the -reset button. - -kgdboc and keyboards -~~~~~~~~~~~~~~~~~~~~~~~~ - -The kgdboc driver contains logic to configure communications with an -attached keyboard. The keyboard infrastructure is only compiled into the -kernel when ``CONFIG_KDB_KEYBOARD=y`` is set in the kernel configuration. - -The core polled keyboard driver for PS/2 type keyboards is in -``drivers/char/kdb_keyboard.c``. This driver is hooked into the debug core -when kgdboc populates the callback in the array called -:c:expr:`kdb_poll_funcs[]`. The kdb_get_kbd_char() is the top-level -function which polls hardware for single character input. - -kgdboc and kms -~~~~~~~~~~~~~~~~~~ - -The kgdboc driver contains logic to request the graphics display to -switch to a text context when you are using ``kgdboc=kms,kbd``, provided -that you have a video driver which has a frame buffer console and atomic -kernel mode setting support. - -Every time the kernel debugger is entered it calls -kgdboc_pre_exp_handler() which in turn calls con_debug_enter() -in the virtual console layer. On resuming kernel execution, the kernel -debugger calls kgdboc_post_exp_handler() which in turn calls -con_debug_leave(). - -Any video driver that wants to be compatible with the kernel debugger -and the atomic kms callbacks must implement the ``mode_set_base_atomic``, -``fb_debug_enter`` and ``fb_debug_leave operations``. For the -``fb_debug_enter`` and ``fb_debug_leave`` the option exists to use the -generic drm fb helper functions or implement something custom for the -hardware. The following example shows the initialization of the -.mode_set_base_atomic operation in -drivers/gpu/drm/i915/intel_display.c:: - - - static const struct drm_crtc_helper_funcs intel_helper_funcs = { - [...] - .mode_set_base_atomic = intel_pipe_set_base_atomic, - [...] - }; - - -Here is an example of how the i915 driver initializes the -fb_debug_enter and fb_debug_leave functions to use the generic drm -helpers in ``drivers/gpu/drm/i915/intel_fb.c``:: - - - static struct fb_ops intelfb_ops = { - [...] - .fb_debug_enter = drm_fb_helper_debug_enter, - .fb_debug_leave = drm_fb_helper_debug_leave, - [...] - }; - - -Credits -======= - -The following people have contributed to this document: - -1. Amit Kale <amitkale@linsyssoft.com> - -2. Tom Rini <trini@kernel.crashing.org> - -In March 2008 this document was completely rewritten by: - -- Jason Wessel <jason.wessel@windriver.com> - -In Jan 2010 this document was updated to include kdb. - -- Jason Wessel <jason.wessel@windriver.com> diff --git a/Documentation/dev-tools/kmemleak.rst b/Documentation/dev-tools/kmemleak.rst index 5483fd39ef29..7d784e03f3f9 100644 --- a/Documentation/dev-tools/kmemleak.rst +++ b/Documentation/dev-tools/kmemleak.rst @@ -161,6 +161,7 @@ See the include/linux/kmemleak.h header for the functions prototype. - ``kmemleak_free_percpu`` - notify of a percpu memory block freeing - ``kmemleak_update_trace`` - update object allocation stack trace - ``kmemleak_not_leak`` - mark an object as not a leak +- ``kmemleak_transient_leak`` - mark an object as a transient leak - ``kmemleak_ignore`` - do not scan or report an object as leak - ``kmemleak_scan_area`` - add scan areas inside a memory block - ``kmemleak_no_scan`` - do not scan a memory block @@ -227,7 +228,7 @@ Testing with kmemleak-test -------------------------- To check if you have all set up to use kmemleak, you can use the kmemleak-test -module, a module that deliberately leaks memory. Set CONFIG_DEBUG_KMEMLEAK_TEST +module, a module that deliberately leaks memory. Set CONFIG_SAMPLE_KMEMLEAK as module (it can't be used as built-in) and boot the kernel with kmemleak enabled. Load the module and perform a scan with:: diff --git a/Documentation/dev-tools/kmsan.rst b/Documentation/dev-tools/kmsan.rst index 55fa82212eb2..0dc668b183f6 100644 --- a/Documentation/dev-tools/kmsan.rst +++ b/Documentation/dev-tools/kmsan.rst @@ -1,9 +1,9 @@ .. SPDX-License-Identifier: GPL-2.0 .. Copyright (C) 2022, Google LLC. -=================================== -The Kernel Memory Sanitizer (KMSAN) -=================================== +=============================== +Kernel Memory Sanitizer (KMSAN) +=============================== KMSAN is a dynamic error detector aimed at finding uses of uninitialized values. It is based on compiler instrumentation, and is quite similar to the @@ -110,6 +110,13 @@ in the Makefile. Think of this as applying ``__no_sanitize_memory`` to every function in the file or directory. Most users won't need KMSAN_SANITIZE, unless their code gets broken by KMSAN (e.g. runs at early boot time). +KMSAN checks can also be temporarily disabled for the current task using +``kmsan_disable_current()`` and ``kmsan_enable_current()`` calls. Each +``kmsan_enable_current()`` call must be preceded by a +``kmsan_disable_current()`` call; these call pairs may be nested. One needs to +be careful with these calls, keeping the regions short and preferring other +ways to disable instrumentation, where possible. + Support ======= @@ -126,7 +133,7 @@ KMSAN shadow memory ------------------- KMSAN associates a metadata byte (also called shadow byte) with every byte of -kernel memory. A bit in the shadow byte is set iff the corresponding bit of the +kernel memory. A bit in the shadow byte is set if the corresponding bit of the kernel memory byte is uninitialized. Marking the memory uninitialized (i.e. setting its shadow bytes to ``0xff``) is called poisoning, marking it initialized (setting the shadow bytes to ``0x00``) is called unpoisoning. @@ -338,11 +345,11 @@ Per-task KMSAN state ~~~~~~~~~~~~~~~~~~~~ Every task_struct has an associated KMSAN task state that holds the KMSAN -context (see above) and a per-task flag disallowing KMSAN reports:: +context (see above) and a per-task counter disallowing KMSAN reports:: struct kmsan_context { ... - bool allow_reporting; + unsigned int depth; struct kmsan_context_state cstate; ... } diff --git a/Documentation/dev-tools/kselftest.rst b/Documentation/dev-tools/kselftest.rst index 12b575b76b20..18c2da67fae4 100644 --- a/Documentation/dev-tools/kselftest.rst +++ b/Documentation/dev-tools/kselftest.rst @@ -31,11 +31,21 @@ kselftest runs as a userspace process. Tests that can be written/run in userspace may wish to use the `Test Harness`_. Tests that need to be run in kernel space may wish to use a `Test Module`_. +Documentation on the tests +========================== + +For documentation on the kselftests themselves, see: + +.. toctree:: + + testing-devices + Running the selftests (hotplug tests are run in limited mode) ============================================================= To build the tests:: + $ make headers $ make -C tools/testing/selftests To run the tests:: @@ -111,7 +121,7 @@ You can specify multiple tests to skip:: You can also specify a restricted list of tests to run together with a dedicated skiplist:: - $ make TARGETS="bpf breakpoints size timers" SKIP_TARGETS=bpf kselftest + $ make TARGETS="breakpoints size timers" SKIP_TARGETS=size kselftest See the top-level tools/testing/selftests/Makefile for the list of all possible targets. @@ -164,10 +174,32 @@ To see the list of available tests, the `-l` option can be used:: The `-c` option can be used to run all the tests from a test collection, or the `-t` option for specific single tests. Either can be used multiple times:: - $ ./run_kselftest.sh -c bpf -c seccomp -t timers:posix_timers -t timer:nanosleep + $ ./run_kselftest.sh -c size -c seccomp -t timers:posix_timers -t timer:nanosleep For other features see the script usage output, seen with the `-h` option. +Timeout for selftests +===================== + +Selftests are designed to be quick and so a default timeout is used of 45 +seconds for each test. Tests can override the default timeout by adding +a settings file in their directory and set a timeout variable there to the +configured a desired upper timeout for the test. Only a few tests override +the timeout with a value higher than 45 seconds, selftests strives to keep +it that way. Timeouts in selftests are not considered fatal because the +system under which a test runs may change and this can also modify the +expected time it takes to run a test. If you have control over the systems +which will run the tests you can configure a test runner on those systems to +use a greater or lower timeout on the command line as with the `-o` or +the `--override-timeout` argument. For example to use 165 seconds instead +one would use:: + + $ ./run_kselftest.sh --override-timeout 165 + +You can look at the TAP output to see if you ran into the timeout. Test +runners which know a test must run under a specific time can then optionally +treat these timeouts then as fatal. + Packaging selftests =================== @@ -187,7 +219,7 @@ option is supported, such as:: tests by using variables specified in `Running a subset of selftests`_ section:: - $ make -C tools/testing/selftests gen_tar TARGETS="bpf" FORMAT=.xz + $ make -C tools/testing/selftests gen_tar TARGETS="size" FORMAT=.xz .. _tar's auto-compress: https://www.gnu.org/software/tar/manual/html_node/gzip.html#auto_002dcompress @@ -205,6 +237,13 @@ In general, the rules for selftests are * Don't cause the top-level "make run_tests" to fail if your feature is unconfigured. + * The output of tests must conform to the TAP standard to ensure high + testing quality and to capture failures/errors with specific details. + The kselftest.h and kselftest_harness.h headers provide wrappers for + outputting test results. These wrappers should be used for pass, + fail, exit, and skip messages. CI systems can easily parse TAP output + messages to detect test results. + Contributing new tests (details) ================================ @@ -222,6 +261,10 @@ Contributing new tests (details) TEST_PROGS, TEST_GEN_PROGS mean it is the executable tested by default. + TEST_GEN_MODS_DIR should be used by tests that require modules to be built + before the test starts. The variable will contain the name of the directory + containing the modules. + TEST_CUSTOM_PROGS should be used by tests that require custom build rules and prevent common build rule use. @@ -232,9 +275,21 @@ Contributing new tests (details) TEST_PROGS_EXTENDED, TEST_GEN_PROGS_EXTENDED mean it is the executable which is not tested by default. + TEST_FILES, TEST_GEN_FILES mean it is the file which is used by test. + TEST_INCLUDES is similar to TEST_FILES, it lists files which should be + included when exporting or installing the tests, with the following + differences: + + * symlinks to files in other directories are preserved + * the part of paths below tools/testing/selftests/ is preserved when + copying the files to the output directory + + TEST_INCLUDES is meant to list dependencies located in other directories of + the selftests hierarchy. + * First use the headers inside the kernel source and/or git repo, and then the system headers. Headers for the kernel release as opposed to headers installed by the distro on the system should be the primary focus to be able @@ -292,7 +347,7 @@ kselftest. We use kselftests for lib/ as an example. 1. Create the test module 2. Create the test script that will run (load/unload) the module - e.g. ``tools/testing/selftests/lib/printf.sh`` + e.g. ``tools/testing/selftests/lib/bitmap.sh`` 3. Add line to config file e.g. ``tools/testing/selftests/lib/config`` diff --git a/Documentation/dev-tools/ktap.rst b/Documentation/dev-tools/ktap.rst index 414c105b10a9..a9810bed5fd4 100644 --- a/Documentation/dev-tools/ktap.rst +++ b/Documentation/dev-tools/ktap.rst @@ -5,7 +5,7 @@ The Kernel Test Anything Protocol (KTAP), version 1 =================================================== TAP, or the Test Anything Protocol is a format for specifying test results used -by a number of projects. It's website and specification are found at this `link +by a number of projects. Its website and specification are found at this `link <https://testanything.org/>`_. The Linux Kernel largely uses TAP output for test results. However, Kernel testing frameworks have special needs for test results which don't align with the original TAP specification. Thus, a "Kernel TAP" @@ -20,6 +20,7 @@ machine-readable, whereas the diagnostic data is unstructured and is there to aid human debugging. KTAP output is built from four different types of lines: + - Version lines - Plan lines - Test case result lines @@ -38,6 +39,7 @@ All KTAP-formatted results begin with a "version line" which specifies which version of the (K)TAP standard the result is compliant with. For example: + - "KTAP version 1" - "TAP version 13" - "TAP version 14" @@ -276,6 +278,7 @@ Example KTAP output This output defines the following hierarchy: A single test called "main_test", which fails, and has three subtests: + - "example_test_1", which passes, and has one subtest: - "test_1", which passes, and outputs the diagnostic message "test_1: initializing test_1" diff --git a/Documentation/dev-tools/kunit/api/clk.rst b/Documentation/dev-tools/kunit/api/clk.rst new file mode 100644 index 000000000000..eeaa50089453 --- /dev/null +++ b/Documentation/dev-tools/kunit/api/clk.rst @@ -0,0 +1,10 @@ +.. SPDX-License-Identifier: GPL-2.0 + +======== +Clk API +======== + +The KUnit clk API is used to test clk providers and clk consumers. + +.. kernel-doc:: drivers/clk/clk_kunit_helpers.c + :export: diff --git a/Documentation/dev-tools/kunit/api/functionredirection.rst b/Documentation/dev-tools/kunit/api/functionredirection.rst new file mode 100644 index 000000000000..3791efc2fcca --- /dev/null +++ b/Documentation/dev-tools/kunit/api/functionredirection.rst @@ -0,0 +1,162 @@ +.. SPDX-License-Identifier: GPL-2.0 + +======================== +Function Redirection API +======================== + +Overview +======== + +When writing unit tests, it's important to be able to isolate the code being +tested from other parts of the kernel. This ensures the reliability of the test +(it won't be affected by external factors), reduces dependencies on specific +hardware or config options (making the test easier to run), and protects the +stability of the rest of the system (making it less likely for test-specific +state to interfere with the rest of the system). + +While for some code (typically generic data structures, helpers, and other +"pure functions") this is trivial, for others (like device drivers, +filesystems, core subsystems) the code is heavily coupled with other parts of +the kernel. + +This coupling is often due to global state in some way: be it a global list of +devices, the filesystem, or some hardware state. Tests need to either carefully +manage, isolate, and restore state, or they can avoid it altogether by +replacing access to and mutation of this state with a "fake" or "mock" variant. + +By refactoring access to such state, such as by introducing a layer of +indirection which can use or emulate a separate set of test state. However, +such refactoring comes with its own costs (and undertaking significant +refactoring before being able to write tests is suboptimal). + +A simpler way to intercept and replace some of the function calls is to use +function redirection via static stubs. + + +Static Stubs +============ + +Static stubs are a way of redirecting calls to one function (the "real" +function) to another function (the "replacement" function). + +It works by adding a macro to the "real" function which checks to see if a test +is running, and if a replacement function is available. If so, that function is +called in place of the original. + +Using static stubs is pretty straightforward: + +1. Add the KUNIT_STATIC_STUB_REDIRECT() macro to the start of the "real" + function. + + This should be the first statement in the function, after any variable + declarations. KUNIT_STATIC_STUB_REDIRECT() takes the name of the + function, followed by all of the arguments passed to the real function. + + For example: + + .. code-block:: c + + void send_data_to_hardware(const char *str) + { + KUNIT_STATIC_STUB_REDIRECT(send_data_to_hardware, str); + /* real implementation */ + } + +2. Write one or more replacement functions. + + These functions should have the same function signature as the real function. + In the event they need to access or modify test-specific state, they can use + kunit_get_current_test() to get a struct kunit pointer. This can then + be passed to the expectation/assertion macros, or used to look up KUnit + resources. + + For example: + + .. code-block:: c + + void fake_send_data_to_hardware(const char *str) + { + struct kunit *test = kunit_get_current_test(); + KUNIT_EXPECT_STREQ(test, str, "Hello World!"); + } + +3. Activate the static stub from your test. + + From within a test, the redirection can be enabled with + kunit_activate_static_stub(), which accepts a struct kunit pointer, + the real function, and the replacement function. You can call this several + times with different replacement functions to swap out implementations of the + function. + + In our example, this would be + + .. code-block:: c + + kunit_activate_static_stub(test, + send_data_to_hardware, + fake_send_data_to_hardware); + +4. Call (perhaps indirectly) the real function. + + Once the redirection is activated, any call to the real function will call + the replacement function instead. Such calls may be buried deep in the + implementation of another function, but must occur from the test's kthread. + + For example: + + .. code-block:: c + + send_data_to_hardware("Hello World!"); /* Succeeds */ + send_data_to_hardware("Something else"); /* Fails the test. */ + +5. (Optionally) disable the stub. + + When you no longer need it, disable the redirection (and hence resume the + original behaviour of the 'real' function) using + kunit_deactivate_static_stub(). Otherwise, it will be automatically disabled + when the test exits. + + For example: + + .. code-block:: c + + kunit_deactivate_static_stub(test, send_data_to_hardware); + + +It's also possible to use these replacement functions to test to see if a +function is called at all, for example: + +.. code-block:: c + + void send_data_to_hardware(const char *str) + { + KUNIT_STATIC_STUB_REDIRECT(send_data_to_hardware, str); + /* real implementation */ + } + + /* In test file */ + int times_called = 0; + void fake_send_data_to_hardware(const char *str) + { + times_called++; + } + ... + /* In the test case, redirect calls for the duration of the test */ + kunit_activate_static_stub(test, send_data_to_hardware, fake_send_data_to_hardware); + + send_data_to_hardware("hello"); + KUNIT_EXPECT_EQ(test, times_called, 1); + + /* Can also deactivate the stub early, if wanted */ + kunit_deactivate_static_stub(test, send_data_to_hardware); + + send_data_to_hardware("hello again"); + KUNIT_EXPECT_EQ(test, times_called, 1); + + + +API Reference +============= + +.. kernel-doc:: include/kunit/static_stub.h + :internal: diff --git a/Documentation/dev-tools/kunit/api/index.rst b/Documentation/dev-tools/kunit/api/index.rst index 45ce04823f9f..5cdb552a0808 100644 --- a/Documentation/dev-tools/kunit/api/index.rst +++ b/Documentation/dev-tools/kunit/api/index.rst @@ -4,17 +4,45 @@ API Reference ============= .. toctree:: + :hidden: test resource + functionredirection + clk + of + platformdevice -This section documents the KUnit kernel testing API. It is divided into the + +This page documents the KUnit kernel testing API. It is divided into the following sections: +Core KUnit API +============== + Documentation/dev-tools/kunit/api/test.rst - - documents all of the standard testing API + - Documents all of the standard testing API Documentation/dev-tools/kunit/api/resource.rst - - documents the KUnit resource API + - Documents the KUnit resource API + +Documentation/dev-tools/kunit/api/functionredirection.rst + + - Documents the KUnit Function Redirection API + +Driver KUnit API +================ + +Documentation/dev-tools/kunit/api/clk.rst + + - Documents the KUnit clk API + +Documentation/dev-tools/kunit/api/of.rst + + - Documents the KUnit device tree (OF) API + +Documentation/dev-tools/kunit/api/platformdevice.rst + + - Documents the KUnit platform device API diff --git a/Documentation/dev-tools/kunit/api/of.rst b/Documentation/dev-tools/kunit/api/of.rst new file mode 100644 index 000000000000..cb4193dcddbb --- /dev/null +++ b/Documentation/dev-tools/kunit/api/of.rst @@ -0,0 +1,13 @@ +.. SPDX-License-Identifier: GPL-2.0 + +==================== +Device Tree (OF) API +==================== + +The KUnit device tree API is used to test device tree (of_*) dependent code. + +.. kernel-doc:: include/kunit/of.h + :internal: + +.. kernel-doc:: drivers/of/of_kunit_helpers.c + :export: diff --git a/Documentation/dev-tools/kunit/api/platformdevice.rst b/Documentation/dev-tools/kunit/api/platformdevice.rst new file mode 100644 index 000000000000..49ddd5729003 --- /dev/null +++ b/Documentation/dev-tools/kunit/api/platformdevice.rst @@ -0,0 +1,10 @@ +.. SPDX-License-Identifier: GPL-2.0 + +=================== +Platform Device API +=================== + +The KUnit platform device API is used to test platform devices. + +.. kernel-doc:: lib/kunit/platform.c + :export: diff --git a/Documentation/dev-tools/kunit/api/resource.rst b/Documentation/dev-tools/kunit/api/resource.rst index 0a94f831259e..ec6002a6b0db 100644 --- a/Documentation/dev-tools/kunit/api/resource.rst +++ b/Documentation/dev-tools/kunit/api/resource.rst @@ -11,3 +11,12 @@ state on a per-test basis, register custom cleanup actions, and more. .. kernel-doc:: include/kunit/resource.h :internal: + +Managed Devices +--------------- + +Functions for using KUnit-managed struct device and struct device_driver. +Include ``kunit/device.h`` to use these. + +.. kernel-doc:: include/kunit/device.h + :internal: diff --git a/Documentation/dev-tools/kunit/architecture.rst b/Documentation/dev-tools/kunit/architecture.rst index e95ab05342bb..f335f883f8f6 100644 --- a/Documentation/dev-tools/kunit/architecture.rst +++ b/Documentation/dev-tools/kunit/architecture.rst @@ -119,9 +119,9 @@ All expectations/assertions are formatted as: terminated immediately. - Assertions call the function: - ``void __noreturn kunit_abort(struct kunit *)``. + ``void __noreturn __kunit_abort(struct kunit *)``. - - ``kunit_abort`` calls the function: + - ``__kunit_abort`` calls the function: ``void __noreturn kunit_try_catch_throw(struct kunit_try_catch *try_catch)``. - ``kunit_try_catch_throw`` calls the function: diff --git a/Documentation/dev-tools/kunit/run_manual.rst b/Documentation/dev-tools/kunit/run_manual.rst index e7b46421f247..98e8d5b28808 100644 --- a/Documentation/dev-tools/kunit/run_manual.rst +++ b/Documentation/dev-tools/kunit/run_manual.rst @@ -35,6 +35,12 @@ or be built into the kernel. a good way of quickly testing everything applicable to the current config. + KUnit can be enabled or disabled at boot time, and this behavior is + controlled by the kunit.enable kernel parameter. + By default, kunit.enable is set to 1 because KUNIT_DEFAULT_ENABLED is + enabled by default. To ensure that tests are executed as expected, + verify that kunit.enable=1 at boot time. + Once we have built our kernel (and/or modules), it is simple to run the tests. If the tests are built-in, they will run automatically on the kernel boot. The results will be written to the kernel log (``dmesg``) @@ -49,9 +55,52 @@ loaded. The results will appear in TAP format in ``dmesg``. +debugfs +======= + +KUnit can be accessed from userspace via the debugfs filesystem (See more +information about debugfs at Documentation/filesystems/debugfs.rst). + +If ``CONFIG_KUNIT_DEBUGFS`` is enabled, the KUnit debugfs filesystem is +mounted at /sys/kernel/debug/kunit. You can use this filesystem to perform +the following actions. + +Retrieve Test Results +===================== + +You can use debugfs to retrieve KUnit test results. The test results are +accessible from the debugfs filesystem in the following read-only file: + +.. code-block :: bash + + /sys/kernel/debug/kunit/<test_suite>/results + +The test results are printed in a KTAP document. Note this document is separate +to the kernel log and thus, may have different test suite numbering. + +Run Tests After Kernel Has Booted +================================= + +You can use the debugfs filesystem to trigger built-in tests to run after +boot. To run the test suite, you can use the following command to write to +the ``/sys/kernel/debug/kunit/<test_suite>/run`` file: + +.. code-block :: bash + + echo "any string" > /sys/kernel/debugfs/kunit/<test_suite>/run + +As a result, the test suite runs and the results are printed to the kernel +log. + +However, this feature is not available with KUnit suites that use init data, +because init data may have been discarded after the kernel boots. KUnit +suites that use init data should be defined using the +kunit_test_init_section_suites() macro. + +Also, you cannot use this feature to run tests concurrently. Instead a test +will wait to run until other tests have completed or failed. + .. note :: - If ``CONFIG_KUNIT_DEBUGFS`` is enabled, KUnit test results will - be accessible from the ``debugfs`` filesystem (if mounted). - They will be in ``/sys/kernel/debug/kunit/<test_suite>/results``, in - TAP format. + For test authors, to use this feature, tests will need to correctly initialise + and/or clean up any data, so the test runs correctly a second time. diff --git a/Documentation/dev-tools/kunit/run_wrapper.rst b/Documentation/dev-tools/kunit/run_wrapper.rst index dafe8eb28d30..6697c71ee8ca 100644 --- a/Documentation/dev-tools/kunit/run_wrapper.rst +++ b/Documentation/dev-tools/kunit/run_wrapper.rst @@ -182,6 +182,8 @@ via UML. To run tests on qemu, by default it requires two flags: is ignored), the tests will run via UML. Non-UML architectures, for example: i386, x86_64, arm and so on; run on qemu. + ``--arch help`` lists all valid ``--arch`` values. + - ``--cross_compile``: Specifies the Kbuild toolchain. It passes the same argument as passed to the ``CROSS_COMPILE`` variable used by Kbuild. As a reminder, this will be the prefix for the toolchain @@ -321,3 +323,15 @@ command line arguments: - ``--json``: If set, stores the test results in a JSON format and prints to `stdout` or saves to a file if a filename is specified. + +- ``--filter``: Specifies filters on test attributes, for example, ``speed!=slow``. + Multiple filters can be used by wrapping input in quotes and separating filters + by commas. Example: ``--filter "speed>slow, module=example"``. + +- ``--filter_action``: If set to ``skip``, filtered tests will be shown as skipped + in the output rather than showing no output. + +- ``--list_tests``: If set, lists all tests that will be run. + +- ``--list_tests_attr``: If set, lists all tests that will be run and all of their + attributes. diff --git a/Documentation/dev-tools/kunit/running_tips.rst b/Documentation/dev-tools/kunit/running_tips.rst index 8e8c493f17d1..bd689db6fdd2 100644 --- a/Documentation/dev-tools/kunit/running_tips.rst +++ b/Documentation/dev-tools/kunit/running_tips.rst @@ -139,6 +139,17 @@ If your installed version of gcc doesn't work, you can tweak the steps: $ ./tools/testing/kunit/kunit.py run --make_options=CC=/usr/bin/gcc-6 $ lcov -t "my_kunit_tests" -o coverage.info -c -d .kunit/ --gcov-tool=/usr/bin/gcov-6 +Alternatively, LLVM-based toolchains can also be used: + +.. code-block:: bash + + # Build with LLVM and append coverage options to the current config + $ ./tools/testing/kunit/kunit.py run --make_options LLVM=1 --kunitconfig=.kunit/ --kunitconfig=tools/testing/kunit/configs/coverage_uml.config + $ llvm-profdata merge -sparse default.profraw -o default.profdata + $ llvm-cov export --format=lcov .kunit/vmlinux -instr-profile default.profdata > coverage.info + # The coverage.info file is in lcov-compatible format and it can be used to e.g. generate HTML report + $ genhtml -o /tmp/coverage_html coverage.info + Running tests manually ====================== @@ -262,3 +273,176 @@ other code executed during boot, e.g. # Reset coverage counters before running the test. $ echo 0 > /sys/kernel/debug/gcov/reset $ modprobe kunit-example-test + + +Test Attributes and Filtering +============================= + +Test suites and cases can be marked with test attributes, such as speed of +test. These attributes will later be printed in test output and can be used to +filter test execution. + +Marking Test Attributes +----------------------- + +Tests are marked with an attribute by including a ``kunit_attributes`` object +in the test definition. + +Test cases can be marked using the ``KUNIT_CASE_ATTR(test_name, attributes)`` +macro to define the test case instead of ``KUNIT_CASE(test_name)``. + +.. code-block:: c + + static const struct kunit_attributes example_attr = { + .speed = KUNIT_VERY_SLOW, + }; + + static struct kunit_case example_test_cases[] = { + KUNIT_CASE_ATTR(example_test, example_attr), + }; + +.. note:: + To mark a test case as slow, you can also use ``KUNIT_CASE_SLOW(test_name)``. + This is a helpful macro as the slow attribute is the most commonly used. + +Test suites can be marked with an attribute by setting the "attr" field in the +suite definition. + +.. code-block:: c + + static const struct kunit_attributes example_attr = { + .speed = KUNIT_VERY_SLOW, + }; + + static struct kunit_suite example_test_suite = { + ..., + .attr = example_attr, + }; + +.. note:: + Not all attributes need to be set in a ``kunit_attributes`` object. Unset + attributes will remain uninitialized and act as though the attribute is set + to 0 or NULL. Thus, if an attribute is set to 0, it is treated as unset. + These unset attributes will not be reported and may act as a default value + for filtering purposes. + +Reporting Attributes +-------------------- + +When a user runs tests, attributes will be present in the raw kernel output (in +KTAP format). Note that attributes will be hidden by default in kunit.py output +for all passing tests but the raw kernel output can be accessed using the +``--raw_output`` flag. This is an example of how test attributes for test cases +will be formatted in kernel output: + +.. code-block:: none + + # example_test.speed: slow + ok 1 example_test + +This is an example of how test attributes for test suites will be formatted in +kernel output: + +.. code-block:: none + + KTAP version 2 + # Subtest: example_suite + # module: kunit_example_test + 1..3 + ... + ok 1 example_suite + +Additionally, users can output a full attribute report of tests with their +attributes, using the command line flag ``--list_tests_attr``: + +.. code-block:: bash + + kunit.py run "example" --list_tests_attr + +.. note:: + This report can be accessed when running KUnit manually by passing in the + module_param ``kunit.action=list_attr``. + +Filtering +--------- + +Users can filter tests using the ``--filter`` command line flag when running +tests. As an example: + +.. code-block:: bash + + kunit.py run --filter speed=slow + + +You can also use the following operations on filters: "<", ">", "<=", ">=", +"!=", and "=". Example: + +.. code-block:: bash + + kunit.py run --filter "speed>slow" + +This example will run all tests with speeds faster than slow. Note that the +characters < and > are often interpreted by the shell, so they may need to be +quoted or escaped, as above. + +Additionally, you can use multiple filters at once. Simply separate filters +using commas. Example: + +.. code-block:: bash + + kunit.py run --filter "speed>slow, module=kunit_example_test" + +.. note:: + You can use this filtering feature when running KUnit manually by passing + the filter as a module param: ``kunit.filter="speed>slow, speed<=normal"``. + +Filtered tests will not run or show up in the test output. You can use the +``--filter_action=skip`` flag to skip filtered tests instead. These tests will be +shown in the test output in the test but will not run. To use this feature when +running KUnit manually, use the module param ``kunit.filter_action=skip``. + +Rules of Filtering Procedure +---------------------------- + +Since both suites and test cases can have attributes, there may be conflicts +between attributes during filtering. The process of filtering follows these +rules: + +- Filtering always operates at a per-test level. + +- If a test has an attribute set, then the test's value is filtered on. + +- Otherwise, the value falls back to the suite's value. + +- If neither are set, the attribute has a global "default" value, which is used. + +List of Current Attributes +-------------------------- + +``speed`` + +This attribute indicates the speed of a test's execution (how slow or fast the +test is). + +This attribute is saved as an enum with the following categories: "normal", +"slow", or "very_slow". The assumed default speed for tests is "normal". This +indicates that the test takes a relatively trivial amount of time (less than +1 second), regardless of the machine it is running on. Any test slower than +this could be marked as "slow" or "very_slow". + +The macro ``KUNIT_CASE_SLOW(test_name)`` can be easily used to set the speed +of a test case to "slow". + +``module`` + +This attribute indicates the name of the module associated with the test. + +This attribute is automatically saved as a string and is printed for each suite. +Tests can also be filtered using this attribute. + +``is_init`` + +This attribute indicates whether the test uses init data or functions. + +This attribute is automatically saved as a boolean and tests can also be +filtered using this attribute. diff --git a/Documentation/dev-tools/kunit/start.rst b/Documentation/dev-tools/kunit/start.rst index c736613c9b19..a98235326bab 100644 --- a/Documentation/dev-tools/kunit/start.rst +++ b/Documentation/dev-tools/kunit/start.rst @@ -250,15 +250,20 @@ Now we are ready to write the test cases. }; kunit_test_suite(misc_example_test_suite); + MODULE_LICENSE("GPL"); + 2. Add the following lines to ``drivers/misc/Kconfig``: .. code-block:: kconfig config MISC_EXAMPLE_TEST tristate "Test for my example" if !KUNIT_ALL_TESTS - depends on MISC_EXAMPLE && KUNIT=y + depends on MISC_EXAMPLE && KUNIT default KUNIT_ALL_TESTS +Note: If your test does not support being built as a loadable module (which is +discouraged), replace tristate by bool, and depend on KUNIT=y instead of KUNIT. + 3. Add the following lines to ``drivers/misc/Makefile``: .. code-block:: make diff --git a/Documentation/dev-tools/kunit/style.rst b/Documentation/dev-tools/kunit/style.rst index b6d0d7359f00..eac81a714a29 100644 --- a/Documentation/dev-tools/kunit/style.rst +++ b/Documentation/dev-tools/kunit/style.rst @@ -188,15 +188,26 @@ For example, a Kconfig entry might look like: Test File and Module Names ========================== -KUnit tests can often be compiled as a module. These modules should be named -after the test suite, followed by ``_test``. If this is likely to conflict with -non-KUnit tests, the suffix ``_kunit`` can also be used. +KUnit tests are often compiled as a separate module. To avoid conflicting +with regular modules, KUnit modules should be named after the test suite, +followed by ``_kunit`` (e.g. if "foobar" is the core module, then +"foobar_kunit" is the KUnit test module). -The easiest way of achieving this is to name the file containing the test suite -``<suite>_test.c`` (or, as above, ``<suite>_kunit.c``). This file should be -placed next to the code under test. +Test source files, whether compiled as a separate module or an +``#include`` in another source file, are best kept in a ``tests/`` +subdirectory to not conflict with other source files (e.g. for +tab-completion). + +Note that the ``_test`` suffix has also been used in some existing +tests. The ``_kunit`` suffix is preferred, as it makes the distinction +between KUnit and non-KUnit tests clearer. + +So for the common case, name the file containing the test suite +``tests/<suite>_kunit.c``. The ``tests`` directory should be placed at +the same level as the code under test. For example, tests for +``lib/string.c`` live in ``lib/tests/string_kunit.c``. If the suite name contains some or all of the name of the test's parent -directory, it may make sense to modify the source filename to reduce redundancy. -For example, a ``foo_firmware`` suite could be in the ``foo/firmware_test.c`` -file. +directory, it may make sense to modify the source filename to reduce +redundancy. For example, a ``foo_firmware`` suite could be in the +``foo/tests/firmware_kunit.c`` file. diff --git a/Documentation/dev-tools/kunit/usage.rst b/Documentation/dev-tools/kunit/usage.rst index 48f8196d5aad..ebd06f5ea455 100644 --- a/Documentation/dev-tools/kunit/usage.rst +++ b/Documentation/dev-tools/kunit/usage.rst @@ -121,6 +121,12 @@ there's an allocation error. ``return`` so they only work from the test function. In KUnit, we stop the current kthread on failure, so you can call them from anywhere. +.. note:: + Warning: There is an exception to the above rule. You shouldn't use assertions + in the suite's exit() function, or in the free function for a resource. These + run when a test is shutting down, and an assertion here prevents further + cleanup code from running, potentially leading to a memory leak. + Customizing error messages -------------------------- @@ -160,7 +166,12 @@ many similar tests. In order to reduce duplication in these closely related tests, most unit testing frameworks (including KUnit) provide the concept of a *test suite*. A test suite is a collection of test cases for a unit of code with optional setup and teardown functions that run before/after the whole -suite and/or every test case. For example: +suite and/or every test case. + +.. note:: + A test case will only run if it is associated with a test suite. + +For example: .. code-block:: c @@ -190,7 +201,10 @@ after everything else. ``kunit_test_suite(example_test_suite)`` registers the test suite with the KUnit test framework. .. note:: - A test case will only run if it is associated with a test suite. + The ``exit`` and ``suite_exit`` functions will run even if ``init`` or + ``suite_init`` fail. Make sure that they can handle any inconsistent + state which may result from ``init`` or ``suite_init`` encountering errors + or exiting early. ``kunit_test_suite(...)`` is a macro which tells the linker to put the specified test suite in a special linker section so that it can be run by KUnit @@ -528,11 +542,31 @@ There is more boilerplate code involved, but it can: Parameterized Testing ~~~~~~~~~~~~~~~~~~~~~ -The table-driven testing pattern is common enough that KUnit has special -support for it. +To run a test case against multiple inputs, KUnit provides a parameterized +testing framework. This feature formalizes and extends the concept of +table-driven tests discussed previously. + +A KUnit test is determined to be parameterized if a parameter generator function +is provided when registering the test case. A test user can either write their +own generator function or use one that is provided by KUnit. The generator +function is stored in ``kunit_case->generate_params`` and can be set using the +macros described in the section below. -By reusing the same ``cases`` array from above, we can write the test as a -"parameterized test" with the following. +To establish the terminology, a "parameterized test" is a test which is run +multiple times (once per "parameter" or "parameter run"). Each parameter run has +both its own independent ``struct kunit`` (the "parameter run context") and +access to a shared parent ``struct kunit`` (the "parameterized test context"). + +Passing Parameters to a Test +^^^^^^^^^^^^^^^^^^^^^^^^^^^^ +There are three ways to provide the parameters to a test: + +Array Parameter Macros: + + KUnit provides special support for the common table-driven testing pattern. + By applying either ``KUNIT_ARRAY_PARAM`` or ``KUNIT_ARRAY_PARAM_DESC`` to the + ``cases`` array from the previous section, we can create a parameterized test + as shown below: .. code-block:: c @@ -541,7 +575,7 @@ By reusing the same ``cases`` array from above, we can write the test as a const char *str; const char *sha1; }; - const struct sha1_test_case cases[] = { + static const struct sha1_test_case cases[] = { { .str = "hello world", .sha1 = "2aae6c35c94fcfb415dbe95f408b9ce91ee846ed", @@ -552,13 +586,9 @@ By reusing the same ``cases`` array from above, we can write the test as a }, }; - // Need a helper function to generate a name for each test case. - static void case_to_desc(const struct sha1_test_case *t, char *desc) - { - strcpy(desc, t->str); - } - // Creates `sha1_gen_params()` to iterate over `cases`. - KUNIT_ARRAY_PARAM(sha1, cases, case_to_desc); + // Creates `sha1_gen_params()` to iterate over `cases` while using + // the struct member `str` for the case description. + KUNIT_ARRAY_PARAM_DESC(sha1, cases, str); // Looks no different from a normal test. static void sha1_test(struct kunit *test) @@ -574,12 +604,324 @@ By reusing the same ``cases`` array from above, we can write the test as a } // Instead of KUNIT_CASE, we use KUNIT_CASE_PARAM and pass in the - // function declared by KUNIT_ARRAY_PARAM. + // function declared by KUNIT_ARRAY_PARAM or KUNIT_ARRAY_PARAM_DESC. static struct kunit_case sha1_test_cases[] = { KUNIT_CASE_PARAM(sha1_test, sha1_gen_params), {} }; +Custom Parameter Generator Function: + + The generator function is responsible for generating parameters one-by-one + and has the following signature: + ``const void* (*)(struct kunit *test, const void *prev, char *desc)``. + You can pass the generator function to the ``KUNIT_CASE_PARAM`` + or ``KUNIT_CASE_PARAM_WITH_INIT`` macros. + + The function receives the previously generated parameter as the ``prev`` argument + (which is ``NULL`` on the first call) and can also access the parameterized + test context passed as the ``test`` argument. KUnit calls this function + repeatedly until it returns ``NULL``, which signifies that a parameterized + test ended. + + Below is an example of how it works: + +.. code-block:: c + + #define MAX_TEST_BUFFER_SIZE 8 + + // Example generator function. It produces a sequence of buffer sizes that + // are powers of two, starting at 1 (e.g., 1, 2, 4, 8). + static const void *buffer_size_gen_params(struct kunit *test, const void *prev, char *desc) + { + long prev_buffer_size = (long)prev; + long next_buffer_size = 1; // Start with an initial size of 1. + + // Stop generating parameters if the limit is reached or exceeded. + if (prev_buffer_size >= MAX_TEST_BUFFER_SIZE) + return NULL; + + // For subsequent calls, calculate the next size by doubling the previous one. + if (prev) + next_buffer_size = prev_buffer_size << 1; + + return (void *)next_buffer_size; + } + + // Simple test to validate that kunit_kzalloc provides zeroed memory. + static void buffer_zero_test(struct kunit *test) + { + long buffer_size = (long)test->param_value; + // Use kunit_kzalloc to allocate a zero-initialized buffer. This makes the + // memory "parameter run managed," meaning it's automatically cleaned up at + // the end of each parameter run. + int *buf = kunit_kzalloc(test, buffer_size * sizeof(int), GFP_KERNEL); + + // Ensure the allocation was successful. + KUNIT_ASSERT_NOT_NULL(test, buf); + + // Loop through the buffer and confirm every element is zero. + for (int i = 0; i < buffer_size; i++) + KUNIT_EXPECT_EQ(test, buf[i], 0); + } + + static struct kunit_case buffer_test_cases[] = { + KUNIT_CASE_PARAM(buffer_zero_test, buffer_size_gen_params), + {} + }; + +Runtime Parameter Array Registration in the Init Function: + + For scenarios where you might need to initialize a parameterized test, you + can directly register a parameter array to the parameterized test context. + + To do this, you must pass the parameterized test context, the array itself, + the array size, and a ``get_description()`` function to the + ``kunit_register_params_array()`` macro. This macro populates + ``struct kunit_params`` within the parameterized test context, effectively + storing a parameter array object. The ``get_description()`` function will + be used for populating parameter descriptions and has the following signature: + ``void (*)(struct kunit *test, const void *param, char *desc)``. Note that it + also has access to the parameterized test context. + + .. important:: + When using this way to register a parameter array, you will need to + manually pass ``kunit_array_gen_params()`` as the generator function to + ``KUNIT_CASE_PARAM_WITH_INIT``. ``kunit_array_gen_params()`` is a KUnit + helper that will use the registered array to generate the parameters. + + If needed, instead of passing the KUnit helper, you can also pass your + own custom generator function that utilizes the parameter array. To + access the parameter array from within the parameter generator + function use ``test->params_array.params``. + + The ``kunit_register_params_array()`` macro should be called within a + ``param_init()`` function that initializes the parameterized test and has + the following signature ``int (*)(struct kunit *test)``. For a detailed + explanation of this mechanism please refer to the "Adding Shared Resources" + section that is after this one. This method supports registering both + dynamically built and static parameter arrays. + + The code snippet below shows the ``example_param_init_dynamic_arr`` test that + utilizes ``make_fibonacci_params()`` to create a dynamic array, which is then + registered using ``kunit_register_params_array()``. To see the full code + please refer to lib/kunit/kunit-example-test.c. + +.. code-block:: c + + /* + * Example of a parameterized test param_init() function that registers a dynamic + * array of parameters. + */ + static int example_param_init_dynamic_arr(struct kunit *test) + { + size_t seq_size; + int *fibonacci_params; + + kunit_info(test, "initializing parameterized test\n"); + + seq_size = 6; + fibonacci_params = make_fibonacci_params(test, seq_size); + if (!fibonacci_params) + return -ENOMEM; + /* + * Passes the dynamic parameter array information to the parameterized test + * context struct kunit. The array and its metadata will be stored in + * test->parent->params_array. The array itself will be located in + * params_data.params. + */ + kunit_register_params_array(test, fibonacci_params, seq_size, + example_param_dynamic_arr_get_desc); + return 0; + } + + static struct kunit_case example_test_cases[] = { + /* + * Note how we pass kunit_array_gen_params() to use the array we + * registered in example_param_init_dynamic_arr() to generate + * parameters. + */ + KUNIT_CASE_PARAM_WITH_INIT(example_params_test_with_init_dynamic_arr, + kunit_array_gen_params, + example_param_init_dynamic_arr, + example_param_exit_dynamic_arr), + {} + }; + +Adding Shared Resources +^^^^^^^^^^^^^^^^^^^^^^^ +All parameter runs in this framework hold a reference to the parameterized test +context, which can be accessed using the parent ``struct kunit`` pointer. The +parameterized test context is not used to execute any test logic itself; instead, +it serves as a container for shared resources. + +It's possible to add resources to share between parameter runs within a +parameterized test by using ``KUNIT_CASE_PARAM_WITH_INIT``, to which you pass +custom ``param_init()`` and ``param_exit()`` functions. These functions run once +before and once after the parameterized test, respectively. + +The ``param_init()`` function, with the signature ``int (*)(struct kunit *test)``, +can be used for adding resources to the ``resources`` or ``priv`` fields of +the parameterized test context, registering the parameter array, and any other +initialization logic. + +The ``param_exit()`` function, with the signature ``void (*)(struct kunit *test)``, +can be used to release any resources that were not parameterized test managed (i.e. +not automatically cleaned up after the parameterized test ends) and for any other +exit logic. + +Both ``param_init()`` and ``param_exit()`` are passed the parameterized test +context behind the scenes. However, the test case function receives the parameter +run context. Therefore, to manage and access shared resources from within a test +case function, you must use ``test->parent``. + +For instance, finding a shared resource allocated by the Resource API requires +passing ``test->parent`` to ``kunit_find_resource()``. This principle extends to +all other APIs that might be used in the test case function, including +``kunit_kzalloc()``, ``kunit_kmalloc_array()``, and others (see +Documentation/dev-tools/kunit/api/test.rst and the +Documentation/dev-tools/kunit/api/resource.rst). + +.. note:: + The ``suite->init()`` function, which executes before each parameter run, + receives the parameter run context. Therefore, any resources set up in + ``suite->init()`` are cleaned up after each parameter run. + +The code below shows how you can add the shared resources. Note that this code +utilizes the Resource API, which you can read more about here: +Documentation/dev-tools/kunit/api/resource.rst. To see the full version of this +code please refer to lib/kunit/kunit-example-test.c. + +.. code-block:: c + + static int example_resource_init(struct kunit_resource *res, void *context) + { + ... /* Code that allocates memory and stores context in res->data. */ + } + + /* This function deallocates memory for the kunit_resource->data field. */ + static void example_resource_free(struct kunit_resource *res) + { + kfree(res->data); + } + + /* This match function locates a test resource based on defined criteria. */ + static bool example_resource_alloc_match(struct kunit *test, struct kunit_resource *res, + void *match_data) + { + return res->data && res->free == example_resource_free; + } + + /* Function to initialize the parameterized test. */ + static int example_param_init(struct kunit *test) + { + int ctx = 3; /* Data to be stored. */ + void *data = kunit_alloc_resource(test, example_resource_init, + example_resource_free, + GFP_KERNEL, &ctx); + if (!data) + return -ENOMEM; + kunit_register_params_array(test, example_params_array, + ARRAY_SIZE(example_params_array)); + return 0; + } + + /* Example test that uses shared resources in test->resources. */ + static void example_params_test_with_init(struct kunit *test) + { + int threshold; + const struct example_param *param = test->param_value; + /* Here we pass test->parent to access the parameterized test context. */ + struct kunit_resource *res = kunit_find_resource(test->parent, + example_resource_alloc_match, + NULL); + + threshold = *((int *)res->data); + KUNIT_ASSERT_LE(test, param->value, threshold); + kunit_put_resource(res); + } + + static struct kunit_case example_test_cases[] = { + KUNIT_CASE_PARAM_WITH_INIT(example_params_test_with_init, kunit_array_gen_params, + example_param_init, NULL), + {} + }; + +As an alternative to using the KUnit Resource API for sharing resources, you can +place them in ``test->parent->priv``. This serves as a more lightweight method +for resource storage, best for scenarios where complex resource management is +not required. + +As stated previously ``param_init()`` and ``param_exit()`` get the parameterized +test context. So, you can directly use ``test->priv`` within ``param_init/exit`` +to manage shared resources. However, from within the test case function, you must +navigate up to the parent ``struct kunit`` i.e. the parameterized test context. +Therefore, you need to use ``test->parent->priv`` to access those same +resources. + +The resources placed in ``test->parent->priv`` will need to be allocated in +memory to persist across the parameter runs. If memory is allocated using the +KUnit memory allocation APIs (described more in the "Allocating Memory" section +below), you won't need to worry about deallocation. The APIs will make the memory +parameterized test 'managed', ensuring that it will automatically get cleaned up +after the parameterized test concludes. + +The code below demonstrates example usage of the ``priv`` field for shared +resources: + +.. code-block:: c + + static const struct example_param { + int value; + } example_params_array[] = { + { .value = 3, }, + { .value = 2, }, + { .value = 1, }, + { .value = 0, }, + }; + + /* Initialize the parameterized test context. */ + static int example_param_init_priv(struct kunit *test) + { + int ctx = 3; /* Data to be stored. */ + int arr_size = ARRAY_SIZE(example_params_array); + + /* + * Allocate memory using kunit_kzalloc(). Since the `param_init` + * function receives the parameterized test context, this memory + * allocation will be scoped to the lifetime of the parameterized test. + */ + test->priv = kunit_kzalloc(test, sizeof(int), GFP_KERNEL); + + /* Assign the context value to test->priv.*/ + *((int *)test->priv) = ctx; + + /* Register the parameter array. */ + kunit_register_params_array(test, example_params_array, arr_size, NULL); + return 0; + } + + static void example_params_test_with_init_priv(struct kunit *test) + { + int threshold; + const struct example_param *param = test->param_value; + + /* By design, test->parent will not be NULL. */ + KUNIT_ASSERT_NOT_NULL(test, test->parent); + + /* Here we use test->parent->priv to access the shared resource. */ + threshold = *(int *)test->parent->priv; + + KUNIT_ASSERT_LE(test, param->value, threshold); + } + + static struct kunit_case example_tests[] = { + KUNIT_CASE_PARAM_WITH_INIT(example_params_test_with_init_priv, + kunit_array_gen_params, + example_param_init_priv, NULL), + {} + }; + Allocating Memory ----------------- @@ -601,17 +943,109 @@ For example: KUNIT_ASSERT_STREQ(test, buffer, ""); } +Registering Cleanup Actions +--------------------------- + +If you need to perform some cleanup beyond simple use of ``kunit_kzalloc``, +you can register a custom "deferred action", which is a cleanup function +run when the test exits (whether cleanly, or via a failed assertion). + +Actions are simple functions with no return value, and a single ``void*`` +context argument, and fulfill the same role as "cleanup" functions in Python +and Go tests, "defer" statements in languages which support them, and +(in some cases) destructors in RAII languages. + +These are very useful for unregistering things from global lists, closing +files or other resources, or freeing resources. + +For example: + +.. code-block:: C + + static void cleanup_device(void *ctx) + { + struct device *dev = (struct device *)ctx; + + device_unregister(dev); + } + + void example_device_test(struct kunit *test) + { + struct my_device dev; + + device_register(&dev); + + kunit_add_action(test, &cleanup_device, &dev); + } + +Note that, for functions like device_unregister which only accept a single +pointer-sized argument, it's possible to automatically generate a wrapper +with the ``KUNIT_DEFINE_ACTION_WRAPPER()`` macro, for example: + +.. code-block:: C + + KUNIT_DEFINE_ACTION_WRAPPER(device_unregister, device_unregister_wrapper, struct device *); + kunit_add_action(test, &device_unregister_wrapper, &dev); + +You should do this in preference to manually casting to the ``kunit_action_t`` type, +as casting function pointers will break Control Flow Integrity (CFI). + +``kunit_add_action`` can fail if, for example, the system is out of memory. +You can use ``kunit_add_action_or_reset`` instead which runs the action +immediately if it cannot be deferred. + +If you need more control over when the cleanup function is called, you +can trigger it early using ``kunit_release_action``, or cancel it entirely +with ``kunit_remove_action``. + Testing Static Functions ------------------------ -If we do not want to expose functions or variables for testing, one option is to -conditionally ``#include`` the test file at the end of your .c file. For -example: +If you want to test static functions without exposing those functions outside of +testing, one option is conditionally export the symbol. When KUnit is enabled, +the symbol is exposed but remains static otherwise. To use this method, follow +the template below. + +.. code-block:: c + + /* In the file containing functions to test "my_file.c" */ + + #include <kunit/visibility.h> + #include <my_file.h> + ... + VISIBLE_IF_KUNIT int do_interesting_thing() + { + ... + } + EXPORT_SYMBOL_IF_KUNIT(do_interesting_thing); + + /* In the header file "my_file.h" */ + + #if IS_ENABLED(CONFIG_KUNIT) + int do_interesting_thing(void); + #endif + + /* In the KUnit test file "my_file_test.c" */ + + #include <kunit/visibility.h> + #include <my_file.h> + ... + MODULE_IMPORT_NS("EXPORTED_FOR_KUNIT_TESTING"); + ... + // Use do_interesting_thing() in tests + +For a full example, see this `patch <https://lore.kernel.org/all/20221207014024.340230-3-rmoar@google.com/>`_ +where a test is modified to conditionally expose static functions for testing +using the macros above. + +As an **alternative** to the method above, you could conditionally ``#include`` +the test file at the end of your .c file. This is not recommended but works +if needed. For example: .. code-block:: c - /* In my_file.c */ + /* In "my_file.c" */ static int do_interesting_thing(); @@ -648,10 +1082,9 @@ We can do this via the ``kunit_test`` field in ``task_struct``, which we can access using the ``kunit_get_current_test()`` function in ``kunit/test-bug.h``. ``kunit_get_current_test()`` is safe to call even if KUnit is not enabled. If -KUnit is not enabled, was built as a module (``CONFIG_KUNIT=m``), or no test is -running in the current task, it will return ``NULL``. This compiles down to -either a no-op or a static key check, so will have a negligible performance -impact when no test is running. +KUnit is not enabled, or if no test is running in the current task, it will +return ``NULL``. This compiles down to either a no-op or a static key check, +so will have a negligible performance impact when no test is running. The example below uses this to implement a "mock" implementation of a function, ``foo``: @@ -726,8 +1159,56 @@ structures as shown below: #endif ``kunit_fail_current_test()`` is safe to call even if KUnit is not enabled. If -KUnit is not enabled, was built as a module (``CONFIG_KUNIT=m``), or no test is -running in the current task, it will do nothing. This compiles down to either a -no-op or a static key check, so will have a negligible performance impact when -no test is running. +KUnit is not enabled, or if no test is running in the current task, it will do +nothing. This compiles down to either a no-op or a static key check, so will +have a negligible performance impact when no test is running. + +Managing Fake Devices and Drivers +--------------------------------- + +When testing drivers or code which interacts with drivers, many functions will +require a ``struct device`` or ``struct device_driver``. In many cases, setting +up a real device is not required to test any given function, so a fake device +can be used instead. + +KUnit provides helper functions to create and manage these fake devices, which +are internally of type ``struct kunit_device``, and are attached to a special +``kunit_bus``. These devices support managed device resources (devres), as +described in Documentation/driver-api/driver-model/devres.rst + +To create a KUnit-managed ``struct device_driver``, use ``kunit_driver_create()``, +which will create a driver with the given name, on the ``kunit_bus``. This driver +will automatically be destroyed when the corresponding test finishes, but can also +be manually destroyed with ``driver_unregister()``. + +To create a fake device, use the ``kunit_device_register()``, which will create +and register a device, using a new KUnit-managed driver created with ``kunit_driver_create()``. +To provide a specific, non-KUnit-managed driver, use ``kunit_device_register_with_driver()`` +instead. Like with managed drivers, KUnit-managed fake devices are automatically +cleaned up when the test finishes, but can be manually cleaned up early with +``kunit_device_unregister()``. + +The KUnit devices should be used in preference to ``root_device_register()``, and +instead of ``platform_device_register()`` in cases where the device is not otherwise +a platform device. + +For example: + +.. code-block:: c + + #include <kunit/device.h> + + static void test_my_device(struct kunit *test) + { + struct device *fake_device; + const char *dev_managed_string; + + // Create a fake device. + fake_device = kunit_device_register(test, "my_device"); + KUNIT_ASSERT_NOT_ERR_OR_NULL(test, fake_device) + + // Pass it to functions which need a device. + dev_managed_string = devm_kstrdup(fake_device, "Hello, World!"); + // Everything is cleaned up automatically when the test ends. + }
\ No newline at end of file diff --git a/Documentation/dev-tools/lkmm/docs/access-marking.rst b/Documentation/dev-tools/lkmm/docs/access-marking.rst new file mode 100644 index 000000000000..80058a4da980 --- /dev/null +++ b/Documentation/dev-tools/lkmm/docs/access-marking.rst @@ -0,0 +1,11 @@ +.. SPDX-License-Identifier: GPL-2.0 + +Access Marking +-------------- + +Literal include of ``tools/memory-model/Documentation/access-marking.txt``. + +------------------------------------------------------------------ + +.. kernel-include:: tools/memory-model/Documentation/access-marking.txt + :literal: diff --git a/Documentation/dev-tools/lkmm/docs/cheatsheet.rst b/Documentation/dev-tools/lkmm/docs/cheatsheet.rst new file mode 100644 index 000000000000..37681f6a6a8c --- /dev/null +++ b/Documentation/dev-tools/lkmm/docs/cheatsheet.rst @@ -0,0 +1,11 @@ +.. SPDX-License-Identifier: GPL-2.0 + +Cheatsheet +---------- + +Literal include of ``tools/memory-model/Documentation/cheatsheet.txt``. + +------------------------------------------------------------------ + +.. kernel-include:: tools/memory-model/Documentation/cheatsheet.txt + :literal: diff --git a/Documentation/dev-tools/lkmm/docs/control-dependencies.rst b/Documentation/dev-tools/lkmm/docs/control-dependencies.rst new file mode 100644 index 000000000000..5ae97e8861eb --- /dev/null +++ b/Documentation/dev-tools/lkmm/docs/control-dependencies.rst @@ -0,0 +1,11 @@ +.. SPDX-License-Identifier: GPL-2.0 + +Control Dependencies +-------------------- + +Literal include of ``tools/memory-model/Documentation/control-dependencies.txt``. + +------------------------------------------------------------------ + +.. kernel-include:: tools/memory-model/Documentation/control-dependencies.txt + :literal: diff --git a/Documentation/dev-tools/lkmm/docs/explanation.rst b/Documentation/dev-tools/lkmm/docs/explanation.rst new file mode 100644 index 000000000000..0bcba9a5ddf7 --- /dev/null +++ b/Documentation/dev-tools/lkmm/docs/explanation.rst @@ -0,0 +1,11 @@ +.. SPDX-License-Identifier: GPL-2.0 + +Explanation +----------- + +Literal include of ``tools/memory-model/Documentation/explanation.txt``. + +------------------------------------------------------------------ + +.. kernel-include:: tools/memory-model/Documentation/explanation.txt + :literal: diff --git a/Documentation/dev-tools/lkmm/docs/glossary.rst b/Documentation/dev-tools/lkmm/docs/glossary.rst new file mode 100644 index 000000000000..849aefdf3d6e --- /dev/null +++ b/Documentation/dev-tools/lkmm/docs/glossary.rst @@ -0,0 +1,11 @@ +.. SPDX-License-Identifier: GPL-2.0 + +Glossary +-------- + +Literal include of ``tools/memory-model/Documentation/glossary.txt``. + +------------------------------------------------------------------ + +.. kernel-include:: tools/memory-model/Documentation/glossary.txt + :literal: diff --git a/Documentation/dev-tools/lkmm/docs/herd-representation.rst b/Documentation/dev-tools/lkmm/docs/herd-representation.rst new file mode 100644 index 000000000000..f7b41f286eb9 --- /dev/null +++ b/Documentation/dev-tools/lkmm/docs/herd-representation.rst @@ -0,0 +1,11 @@ +.. SPDX-License-Identifier: GPL-2.0 + +herd-representation +------------------- + +Literal include of ``tools/memory-model/Documentation/herd-representation.txt``. + +------------------------------------------------------------------ + +.. kernel-include:: tools/memory-model/Documentation/herd-representation.txt + :literal: diff --git a/Documentation/dev-tools/lkmm/docs/index.rst b/Documentation/dev-tools/lkmm/docs/index.rst new file mode 100644 index 000000000000..abbddcc009de --- /dev/null +++ b/Documentation/dev-tools/lkmm/docs/index.rst @@ -0,0 +1,21 @@ +.. SPDX-License-Identifier: GPL-2.0 + +Documentation +============= + +.. toctree:: + :maxdepth: 1 + + readme + simple + ordering + litmus-tests + locking + recipes + control-dependencies + access-marking + cheatsheet + explanation + herd-representation + glossary + references diff --git a/Documentation/dev-tools/lkmm/docs/litmus-tests.rst b/Documentation/dev-tools/lkmm/docs/litmus-tests.rst new file mode 100644 index 000000000000..3293f4540156 --- /dev/null +++ b/Documentation/dev-tools/lkmm/docs/litmus-tests.rst @@ -0,0 +1,11 @@ +.. SPDX-License-Identifier: GPL-2.0 + +Litmus Tests +------------ + +Literal include of ``tools/memory-model/Documentation/litmus-tests.txt``. + +------------------------------------------------------------------ + +.. kernel-include:: tools/memory-model/Documentation/litmus-tests.txt + :literal: diff --git a/Documentation/dev-tools/lkmm/docs/locking.rst b/Documentation/dev-tools/lkmm/docs/locking.rst new file mode 100644 index 000000000000..b5eae4c0acb7 --- /dev/null +++ b/Documentation/dev-tools/lkmm/docs/locking.rst @@ -0,0 +1,11 @@ +.. SPDX-License-Identifier: GPL-2.0 + +Locking +------- + +Literal include of ``tools/memory-model/Documentation/locking.txt``. + +------------------------------------------------------------------ + +.. kernel-include:: tools/memory-model/Documentation/locking.txt + :literal: diff --git a/Documentation/dev-tools/lkmm/docs/ordering.rst b/Documentation/dev-tools/lkmm/docs/ordering.rst new file mode 100644 index 000000000000..a2343c12462d --- /dev/null +++ b/Documentation/dev-tools/lkmm/docs/ordering.rst @@ -0,0 +1,11 @@ +.. SPDX-License-Identifier: GPL-2.0 + +Ordering +-------- + +Literal include of ``tools/memory-model/Documentation/ordering.txt``. + +------------------------------------------------------------------ + +.. kernel-include:: tools/memory-model/Documentation/ordering.txt + :literal: diff --git a/Documentation/dev-tools/lkmm/docs/readme.rst b/Documentation/dev-tools/lkmm/docs/readme.rst new file mode 100644 index 000000000000..51e7a64e4435 --- /dev/null +++ b/Documentation/dev-tools/lkmm/docs/readme.rst @@ -0,0 +1,11 @@ +.. SPDX-License-Identifier: GPL-2.0 + +README (for LKMM Documentation) +------------------------------- + +Literal include of ``tools/memory-model/Documentation/README``. + +------------------------------------------------------------------ + +.. kernel-include:: tools/memory-model/Documentation/README + :literal: diff --git a/Documentation/dev-tools/lkmm/docs/recipes.rst b/Documentation/dev-tools/lkmm/docs/recipes.rst new file mode 100644 index 000000000000..e55952640047 --- /dev/null +++ b/Documentation/dev-tools/lkmm/docs/recipes.rst @@ -0,0 +1,11 @@ +.. SPDX-License-Identifier: GPL-2.0 + +Recipes +------- + +Literal include of ``tools/memory-model/Documentation/recipes.txt``. + +------------------------------------------------------------------ + +.. kernel-include:: tools/memory-model/Documentation/recipes.txt + :literal: diff --git a/Documentation/dev-tools/lkmm/docs/references.rst b/Documentation/dev-tools/lkmm/docs/references.rst new file mode 100644 index 000000000000..c6831b3c9c02 --- /dev/null +++ b/Documentation/dev-tools/lkmm/docs/references.rst @@ -0,0 +1,11 @@ +.. SPDX-License-Identifier: GPL-2.0 + +References +---------- + +Literal include of ``tools/memory-model/Documentation/references.txt``. + +------------------------------------------------------------------ + +.. kernel-include:: tools/memory-model/Documentation/references.txt + :literal: diff --git a/Documentation/dev-tools/lkmm/docs/simple.rst b/Documentation/dev-tools/lkmm/docs/simple.rst new file mode 100644 index 000000000000..5c1094c95f45 --- /dev/null +++ b/Documentation/dev-tools/lkmm/docs/simple.rst @@ -0,0 +1,11 @@ +.. SPDX-License-Identifier: GPL-2.0 + +Simple +------ + +Literal include of ``tools/memory-model/Documentation/simple.txt``. + +------------------------------------------------------------------ + +.. kernel-include:: tools/memory-model/Documentation/simple.txt + :literal: diff --git a/Documentation/dev-tools/lkmm/index.rst b/Documentation/dev-tools/lkmm/index.rst new file mode 100644 index 000000000000..e52782449ca3 --- /dev/null +++ b/Documentation/dev-tools/lkmm/index.rst @@ -0,0 +1,15 @@ +.. SPDX-License-Identifier: GPL-2.0 + +============================================ +Linux Kernel Memory Consistency Model (LKMM) +============================================ + +This section literally renders documents under ``tools/memory-model/`` +and ``tools/memory-model/Documentation/``, which are maintained in +the *pure* plain text form. + +.. toctree:: + :maxdepth: 2 + + readme + docs/index diff --git a/Documentation/dev-tools/lkmm/readme.rst b/Documentation/dev-tools/lkmm/readme.rst new file mode 100644 index 000000000000..a7f847109584 --- /dev/null +++ b/Documentation/dev-tools/lkmm/readme.rst @@ -0,0 +1,11 @@ +.. SPDX-License-Identifier: GPL-2.0 + +README (for LKMM) +================= + +Literal include of ``tools/memory-model/README``. + +------------------------------------------------------------ + +.. kernel-include:: tools/memory-model/README + :literal: diff --git a/Documentation/dev-tools/propeller.rst b/Documentation/dev-tools/propeller.rst new file mode 100644 index 000000000000..92195958e3db --- /dev/null +++ b/Documentation/dev-tools/propeller.rst @@ -0,0 +1,162 @@ +.. SPDX-License-Identifier: GPL-2.0 + +===================================== +Using Propeller with the Linux kernel +===================================== + +This enables Propeller build support for the kernel when using Clang +compiler. Propeller is a profile-guided optimization (PGO) method used +to optimize binary executables. Like AutoFDO, it utilizes hardware +sampling to gather information about the frequency of execution of +different code paths within a binary. Unlike AutoFDO, this information +is then used right before linking phase to optimize (among others) +block layout within and across functions. + +A few important notes about adopting Propeller optimization: + +#. Although it can be used as a standalone optimization step, it is + strongly recommended to apply Propeller on top of AutoFDO, + AutoFDO+ThinLTO or Instrument FDO. The rest of this document + assumes this paradigm. + +#. Propeller uses another round of profiling on top of + AutoFDO/AutoFDO+ThinLTO/iFDO. The whole build process involves + "build-afdo - train-afdo - build-propeller - train-propeller - + build-optimized". + +#. Propeller requires LLVM 19 release or later for Clang/Clang++ + and the linker(ld.lld). + +#. In addition to LLVM toolchain, Propeller requires a profiling + conversion tool: https://github.com/google/autofdo with a release + after v0.30.1: https://github.com/google/autofdo/releases/tag/v0.30.1. + +The Propeller optimization process involves the following steps: + +#. Initial building: Build the AutoFDO or AutoFDO+ThinLTO binary as + you would normally do, but with a set of compile-time / link-time + flags, so that a special metadata section is created within the + kernel binary. The special section is only intend to be used by the + profiling tool, it is not part of the runtime image, nor does it + change kernel run time text sections. + +#. Profiling: The above kernel is then run with a representative + workload to gather execution frequency data. This data is collected + using hardware sampling, via perf. Propeller is most effective on + platforms supporting advanced PMU features like LBR on Intel + machines. This step is the same as profiling the kernel for AutoFDO + (the exact perf parameters can be different). + +#. Propeller profile generation: Perf output file is converted to a + pair of Propeller profiles via an offline tool. + +#. Optimized build: Build the AutoFDO or AutoFDO+ThinLTO optimized + binary as you would normally do, but with a compile-time / + link-time flag to pick up the Propeller compile time and link time + profiles. This build step uses 3 profiles - the AutoFDO profile, + the Propeller compile-time profile and the Propeller link-time + profile. + +#. Deployment: The optimized kernel binary is deployed and used + in production environments, providing improved performance + and reduced latency. + +Preparation +=========== + +Configure the kernel with:: + + CONFIG_AUTOFDO_CLANG=y + CONFIG_PROPELLER_CLANG=y + +Customization +============= + +The default CONFIG_PROPELLER_CLANG setting covers kernel space objects +for Propeller builds. One can, however, enable or disable Propeller build +for individual files and directories by adding a line similar to the +following to the respective kernel Makefile: + +- For enabling a single file (e.g. foo.o):: + + PROPELLER_PROFILE_foo.o := y + +- For enabling all files in one directory:: + + PROPELLER_PROFILE := y + +- For disabling one file:: + + PROPELLER_PROFILE_foo.o := n + +- For disabling all files in one directory:: + + PROPELLER__PROFILE := n + + +Workflow +======== + +Here is an example workflow for building an AutoFDO+Propeller kernel: + +1) Assuming an AutoFDO profile is already collected following + instructions in the AutoFDO document, build the kernel on the host + machine, with AutoFDO and Propeller build configs :: + + CONFIG_AUTOFDO_CLANG=y + CONFIG_PROPELLER_CLANG=y + + and :: + + $ make LLVM=1 CLANG_AUTOFDO_PROFILE=<autofdo-profile-name> + +2) Install the kernel on the test machine. + +3) Run the load tests. The '-c' option in perf specifies the sample + event period. We suggest using a suitable prime number, like 500009, + for this purpose. + + - For Intel platforms:: + + $ perf record -e BR_INST_RETIRED.NEAR_TAKEN:k -a -N -b -c <count> -o <perf_file> -- <loadtest> + + - For AMD platforms:: + + $ perf record --pfm-event RETIRED_TAKEN_BRANCH_INSTRUCTIONS:k -a -N -b -c <count> -o <perf_file> -- <loadtest> + + Note you can repeat the above steps to collect multiple <perf_file>s. + +4) (Optional) Download the raw perf file(s) to the host machine. + +5) Use the create_llvm_prof tool (https://github.com/google/autofdo) to + generate Propeller profile. :: + + $ create_llvm_prof --binary=<vmlinux> --profile=<perf_file> + --format=propeller --propeller_output_module_name + --out=<propeller_profile_prefix>_cc_profile.txt + --propeller_symorder=<propeller_profile_prefix>_ld_profile.txt + + "<propeller_profile_prefix>" can be something like "/home/user/dir/any_string". + + This command generates a pair of Propeller profiles: + "<propeller_profile_prefix>_cc_profile.txt" and + "<propeller_profile_prefix>_ld_profile.txt". + + If there are more than 1 perf_file collected in the previous step, + you can create a temp list file "<perf_file_list>" with each line + containing one perf file name and run:: + + $ create_llvm_prof --binary=<vmlinux> --profile=@<perf_file_list> + --format=propeller --propeller_output_module_name + --out=<propeller_profile_prefix>_cc_profile.txt + --propeller_symorder=<propeller_profile_prefix>_ld_profile.txt + +6) Rebuild the kernel using the AutoFDO and Propeller + profiles. :: + + CONFIG_AUTOFDO_CLANG=y + CONFIG_PROPELLER_CLANG=y + + and :: + + $ make LLVM=1 CLANG_AUTOFDO_PROFILE=<profile_file> CLANG_PROPELLER_PROFILE_PREFIX=<propeller_profile_prefix> diff --git a/Documentation/dev-tools/testing-devices.rst b/Documentation/dev-tools/testing-devices.rst new file mode 100644 index 000000000000..ab26adb99051 --- /dev/null +++ b/Documentation/dev-tools/testing-devices.rst @@ -0,0 +1,47 @@ +.. SPDX-License-Identifier: GPL-2.0 +.. Copyright (c) 2024 Collabora Ltd + +============================= +Device testing with kselftest +============================= + + +There are a few different kselftests available for testing devices generically, +with some overlap in coverage and different requirements. This document aims to +give an overview of each one. + +Note: Paths in this document are relative to the kselftest folder +(``tools/testing/selftests``). + +Device oriented kselftests: + +* Devicetree (``dt``) + + * **Coverage**: Probe status for devices described in Devicetree + * **Requirements**: None + +* Error logs (``devices/error_logs``) + + * **Coverage**: Error (or more critical) log messages presence coming from any + device + * **Requirements**: None + +* Discoverable bus (``devices/probe``) + + * **Coverage**: Presence and probe status of USB or PCI devices that have been + described in the reference file + * **Requirements**: Manually describe the devices that should be tested in a + YAML reference file (see ``devices/probe/boards/google,spherion.yaml`` for + an example) + +* Exist (``devices/exist``) + + * **Coverage**: Presence of all devices + * **Requirements**: Generate the reference (see ``devices/exist/README.rst`` + for details) on a known-good kernel + +Therefore, the suggestion is to enable the error log and devicetree tests on all +(DT-based) platforms, since they don't have any requirements. Then to greatly +improve coverage, generate the reference for each platform and enable the exist +test. The discoverable bus test can be used to verify the probe status of +specific USB or PCI devices, but is probably not worth it for most cases. diff --git a/Documentation/dev-tools/testing-overview.rst b/Documentation/dev-tools/testing-overview.rst index 0aaf6ea53608..1619e5e5cc9c 100644 --- a/Documentation/dev-tools/testing-overview.rst +++ b/Documentation/dev-tools/testing-overview.rst @@ -104,6 +104,8 @@ Some of these tools are listed below: KASAN and can be used in production. See Documentation/dev-tools/kfence.rst * lockdep is a locking correctness validator. See Documentation/locking/lockdep-design.rst +* Runtime Verification (RV) supports checking specific behaviours for a given + subsystem. See Documentation/trace/rv/runtime-verification.rst * There are several other pieces of debug instrumentation in the kernel, many of which can be found in lib/Kconfig.debug diff --git a/Documentation/dev-tools/ubsan.rst b/Documentation/dev-tools/ubsan.rst index 1be6618e232d..e3591f8e9d5b 100644 --- a/Documentation/dev-tools/ubsan.rst +++ b/Documentation/dev-tools/ubsan.rst @@ -1,5 +1,7 @@ -The Undefined Behavior Sanitizer - UBSAN -======================================== +.. SPDX-License-Identifier: GPL-2.0 + +Undefined Behavior Sanitizer - UBSAN +==================================== UBSAN is a runtime undefined behaviour checker. @@ -47,34 +49,22 @@ Report example Usage ----- -To enable UBSAN configure kernel with:: - - CONFIG_UBSAN=y - -and to check the entire kernel:: - - CONFIG_UBSAN_SANITIZE_ALL=y - -To enable instrumentation for specific files or directories, add a line -similar to the following to the respective kernel Makefile: +To enable UBSAN, configure the kernel with:: -- For a single file (e.g. main.o):: + CONFIG_UBSAN=y - UBSAN_SANITIZE_main.o := y - -- For all files in one directory:: - - UBSAN_SANITIZE := y - -To exclude files from being instrumented even if -``CONFIG_UBSAN_SANITIZE_ALL=y``, use:: +To exclude files from being instrumented use:: UBSAN_SANITIZE_main.o := n -and:: +and to exclude all targets in one directory use:: UBSAN_SANITIZE := n +When disabled for all targets, specific files can be enabled using:: + + UBSAN_SANITIZE_main.o := y + Detection of unaligned accesses controlled through the separate option - CONFIG_UBSAN_ALIGNMENT. It's off by default on architectures that support unaligned accesses (CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS=y). One could |