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Diffstat (limited to 'Documentation/dev-tools')
24 files changed, 882 insertions, 1197 deletions
diff --git a/Documentation/dev-tools/autofdo.rst b/Documentation/dev-tools/autofdo.rst new file mode 100644 index 000000000000..1f0a451e9ccd --- /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..abb3ff682076 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 @@ -470,8 +470,6 @@ 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 -------- @@ -906,6 +904,20 @@ 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 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 535ce126fb4f..6e70a1e9a3c0 100644 --- a/Documentation/dev-tools/coccinelle.rst +++ b/Documentation/dev-tools/coccinelle.rst @@ -250,25 +250,17 @@ variables for .cocciconfig is as follows: - 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``. - ``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 895285c037c7..000000000000 --- a/Documentation/dev-tools/gdb-kernel-debugging.rst +++ /dev/null @@ -1,179 +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. - -- Build the gdb scripts (required on kernels v5.1 and above):: - - make scripts_gdb - -- 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 efa49cdc8e2e..65c54b27a60b 100644 --- a/Documentation/dev-tools/index.rst +++ b/Documentation/dev-tools/index.rst @@ -10,12 +10,16 @@ whole; patches welcome! A brief overview of testing-specific tools can be found in Documentation/dev-tools/testing-overview.rst +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 @@ -26,12 +30,13 @@ Documentation/dev-tools/testing-overview.rst kmemleak kcsan 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 858c77fe7dc4..0a1418ab72fd 100644 --- a/Documentation/dev-tools/kasan.rst +++ b/Documentation/dev-tools/kasan.rst @@ -169,7 +169,7 @@ 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 @@ -179,8 +179,8 @@ 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 @@ -200,8 +200,8 @@ 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 @@ -277,6 +277,27 @@ 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 ---------------------- @@ -490,19 +511,14 @@ 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:: @@ -510,15 +526,15 @@ 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:: @@ -529,16 +545,16 @@ 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/kcsan.rst b/Documentation/dev-tools/kcsan.rst index 94b6802ab0ab..d81c42d1063e 100644 --- a/Documentation/dev-tools/kcsan.rst +++ b/Documentation/dev-tools/kcsan.rst @@ -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``:: @@ -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 2cb00b53339f..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 diff --git a/Documentation/dev-tools/kmsan.rst b/Documentation/dev-tools/kmsan.rst index 323eedad53cd..0dc668b183f6 100644 --- a/Documentation/dev-tools/kmsan.rst +++ b/Documentation/dev-tools/kmsan.rst @@ -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 ab376b316c36..fdb1df86783a 100644 --- a/Documentation/dev-tools/kselftest.rst +++ b/Documentation/dev-tools/kselftest.rst @@ -31,6 +31,15 @@ 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) ============================================================= @@ -183,7 +192,7 @@ 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: +one would use:: $ ./run_kselftest.sh --override-timeout 165 @@ -228,6 +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) ================================ @@ -245,6 +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. @@ -255,9 +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 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/index.rst b/Documentation/dev-tools/kunit/api/index.rst index 2d8f756aab56..5cdb552a0808 100644 --- a/Documentation/dev-tools/kunit/api/index.rst +++ b/Documentation/dev-tools/kunit/api/index.rst @@ -9,11 +9,17 @@ API Reference test resource functionredirection + clk + of + platformdevice 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 @@ -25,3 +31,18 @@ Documentation/dev-tools/kunit/api/resource.rst 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/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/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 2de7c63415da..e3591f8e9d5b 100644 --- a/Documentation/dev-tools/ubsan.rst +++ b/Documentation/dev-tools/ubsan.rst @@ -49,34 +49,22 @@ Report example Usage ----- -To enable UBSAN configure kernel with:: +To enable UBSAN, configure the kernel with:: - CONFIG_UBSAN=y + 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: - -- For a single file (e.g. main.o):: - - 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 |