diff options
Diffstat (limited to 'Documentation/kbuild')
| -rw-r--r-- | Documentation/kbuild/gcc-plugins.rst | 97 | ||||
| -rw-r--r-- | Documentation/kbuild/index.rst | 2 | ||||
| -rw-r--r-- | Documentation/kbuild/kbuild.rst | 5 | ||||
| -rw-r--r-- | Documentation/kbuild/kconfig-language.rst | 27 | ||||
| -rw-r--r-- | Documentation/kbuild/llvm.rst | 87 |
5 files changed, 215 insertions, 3 deletions
diff --git a/Documentation/kbuild/gcc-plugins.rst b/Documentation/kbuild/gcc-plugins.rst new file mode 100644 index 000000000000..4b1c10f88e30 --- /dev/null +++ b/Documentation/kbuild/gcc-plugins.rst @@ -0,0 +1,97 @@ +========================= +GCC plugin infrastructure +========================= + + +Introduction +============ + +GCC plugins are loadable modules that provide extra features to the +compiler [1]_. They are useful for runtime instrumentation and static analysis. +We can analyse, change and add further code during compilation via +callbacks [2]_, GIMPLE [3]_, IPA [4]_ and RTL passes [5]_. + +The GCC plugin infrastructure of the kernel supports all gcc versions from +4.5 to 6.0, building out-of-tree modules, cross-compilation and building in a +separate directory. +Plugin source files have to be compilable by both a C and a C++ compiler as well +because gcc versions 4.5 and 4.6 are compiled by a C compiler, +gcc-4.7 can be compiled by a C or a C++ compiler, +and versions 4.8+ can only be compiled by a C++ compiler. + +Currently the GCC plugin infrastructure supports only the x86, arm, arm64 and +powerpc architectures. + +This infrastructure was ported from grsecurity [6]_ and PaX [7]_. + +-- + +.. [1] https://gcc.gnu.org/onlinedocs/gccint/Plugins.html +.. [2] https://gcc.gnu.org/onlinedocs/gccint/Plugin-API.html#Plugin-API +.. [3] https://gcc.gnu.org/onlinedocs/gccint/GIMPLE.html +.. [4] https://gcc.gnu.org/onlinedocs/gccint/IPA.html +.. [5] https://gcc.gnu.org/onlinedocs/gccint/RTL.html +.. [6] https://grsecurity.net/ +.. [7] https://pax.grsecurity.net/ + + +Files +===== + +**$(src)/scripts/gcc-plugins** + + This is the directory of the GCC plugins. + +**$(src)/scripts/gcc-plugins/gcc-common.h** + + This is a compatibility header for GCC plugins. + It should be always included instead of individual gcc headers. + +**$(src)/scripts/gcc-plugin.sh** + + This script checks the availability of the included headers in + gcc-common.h and chooses the proper host compiler to build the plugins + (gcc-4.7 can be built by either gcc or g++). + +**$(src)/scripts/gcc-plugins/gcc-generate-gimple-pass.h, +$(src)/scripts/gcc-plugins/gcc-generate-ipa-pass.h, +$(src)/scripts/gcc-plugins/gcc-generate-simple_ipa-pass.h, +$(src)/scripts/gcc-plugins/gcc-generate-rtl-pass.h** + + These headers automatically generate the registration structures for + GIMPLE, SIMPLE_IPA, IPA and RTL passes. They support all gcc versions + from 4.5 to 6.0. + They should be preferred to creating the structures by hand. + + +Usage +===== + +You must install the gcc plugin headers for your gcc version, +e.g., on Ubuntu for gcc-4.9:: + + apt-get install gcc-4.9-plugin-dev + +Or on Fedora:: + + dnf install gcc-plugin-devel + +Enable a GCC plugin based feature in the kernel config:: + + CONFIG_GCC_PLUGIN_CYC_COMPLEXITY = y + +To compile only the plugin(s):: + + make gcc-plugins + +or just run the kernel make and compile the whole kernel with +the cyclomatic complexity GCC plugin. + + +4. How to add a new GCC plugin +============================== + +The GCC plugins are in $(src)/scripts/gcc-plugins/. You can use a file or a directory +here. It must be added to $(src)/scripts/gcc-plugins/Makefile, +$(src)/scripts/Makefile.gcc-plugins and $(src)/arch/Kconfig. +See the cyc_complexity_plugin.c (CONFIG_GCC_PLUGIN_CYC_COMPLEXITY) GCC plugin. diff --git a/Documentation/kbuild/index.rst b/Documentation/kbuild/index.rst index 0f144fad99a6..cee2f99f734b 100644 --- a/Documentation/kbuild/index.rst +++ b/Documentation/kbuild/index.rst @@ -19,6 +19,8 @@ Kernel Build System issues reproducible-builds + gcc-plugins + llvm .. only:: subproject and html diff --git a/Documentation/kbuild/kbuild.rst b/Documentation/kbuild/kbuild.rst index 510f38d7e78a..2d1fc03d346e 100644 --- a/Documentation/kbuild/kbuild.rst +++ b/Documentation/kbuild/kbuild.rst @@ -262,3 +262,8 @@ KBUILD_BUILD_USER, KBUILD_BUILD_HOST These two variables allow to override the user@host string displayed during boot and in /proc/version. The default value is the output of the commands whoami and host, respectively. + +LLVM +---- +If this variable is set to 1, Kbuild will use Clang and LLVM utilities instead +of GCC and GNU binutils to build the kernel. diff --git a/Documentation/kbuild/kconfig-language.rst b/Documentation/kbuild/kconfig-language.rst index d0111dd26410..a1601ec3317b 100644 --- a/Documentation/kbuild/kconfig-language.rst +++ b/Documentation/kbuild/kconfig-language.rst @@ -159,11 +159,11 @@ applicable everywhere (see syntax). Given the following example:: config FOO - tristate + tristate "foo" imply BAZ config BAZ - tristate + tristate "baz" depends on BAR The following values are possible: @@ -173,7 +173,10 @@ applicable everywhere (see syntax). === === ============= ============== n y n N/m/y m y m M/y/n - y y y Y/n + y y y Y/m/n + n m n N/m + m m m M/n + y m n M/n y n * N === === ============= ============== @@ -181,6 +184,24 @@ applicable everywhere (see syntax). ability to hook into a secondary subsystem while allowing the user to configure that subsystem out without also having to unset these drivers. + Note: If the combination of FOO=y and BAR=m causes a link error, + you can guard the function call with IS_REACHABLE():: + + foo_init() + { + if (IS_REACHABLE(CONFIG_BAZ)) + baz_register(&foo); + ... + } + + Note: If the feature provided by BAZ is highly desirable for FOO, + FOO should imply not only BAZ, but also its dependency BAR:: + + config FOO + tristate "foo" + imply BAR + imply BAZ + - limiting menu display: "visible if" <expr> This attribute is only applicable to menu blocks, if the condition is diff --git a/Documentation/kbuild/llvm.rst b/Documentation/kbuild/llvm.rst new file mode 100644 index 000000000000..c776b6eee969 --- /dev/null +++ b/Documentation/kbuild/llvm.rst @@ -0,0 +1,87 @@ +============================== +Building Linux with Clang/LLVM +============================== + +This document covers how to build the Linux kernel with Clang and LLVM +utilities. + +About +----- + +The Linux kernel has always traditionally been compiled with GNU toolchains +such as GCC and binutils. Ongoing work has allowed for `Clang +<https://clang.llvm.org/>`_ and `LLVM <https://llvm.org/>`_ utilities to be +used as viable substitutes. Distributions such as `Android +<https://www.android.com/>`_, `ChromeOS +<https://www.chromium.org/chromium-os>`_, and `OpenMandriva +<https://www.openmandriva.org/>`_ use Clang built kernels. `LLVM is a +collection of toolchain components implemented in terms of C++ objects +<https://www.aosabook.org/en/llvm.html>`_. Clang is a front-end to LLVM that +supports C and the GNU C extensions required by the kernel, and is pronounced +"klang," not "see-lang." + +Clang +----- + +The compiler used can be swapped out via `CC=` command line argument to `make`. +`CC=` should be set when selecting a config and during a build. + + make CC=clang defconfig + + make CC=clang + +Cross Compiling +--------------- + +A single Clang compiler binary will typically contain all supported backends, +which can help simplify cross compiling. + + ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- make CC=clang + +`CROSS_COMPILE` is not used to prefix the Clang compiler binary, instead +`CROSS_COMPILE` is used to set a command line flag: `--target <triple>`. For +example: + + clang --target aarch64-linux-gnu foo.c + +LLVM Utilities +-------------- + +LLVM has substitutes for GNU binutils utilities. Kbuild supports `LLVM=1` +to enable them. + + make LLVM=1 + +They can be enabled individually. The full list of the parameters: + + make CC=clang LD=ld.lld AR=llvm-ar NM=llvm-nm STRIP=llvm-strip \\ + OBJCOPY=llvm-objcopy OBJDUMP=llvm-objdump OBJSIZE=llvm-size \\ + READELF=llvm-readelf HOSTCC=clang HOSTCXX=clang++ HOSTAR=llvm-ar \\ + HOSTLD=ld.lld + +Currently, the integrated assembler is disabled by default. You can pass +`LLVM_IAS=1` to enable it. + +Getting Help +------------ + +- `Website <https://clangbuiltlinux.github.io/>`_ +- `Mailing List <https://groups.google.com/forum/#!forum/clang-built-linux>`_: <clang-built-linux@googlegroups.com> +- `Issue Tracker <https://github.com/ClangBuiltLinux/linux/issues>`_ +- IRC: #clangbuiltlinux on chat.freenode.net +- `Telegram <https://t.me/ClangBuiltLinux>`_: @ClangBuiltLinux +- `Wiki <https://github.com/ClangBuiltLinux/linux/wiki>`_ +- `Beginner Bugs <https://github.com/ClangBuiltLinux/linux/issues?q=is%3Aopen+is%3Aissue+label%3A%22good+first+issue%22>`_ + +Getting LLVM +------------- + +- http://releases.llvm.org/download.html +- https://github.com/llvm/llvm-project +- https://llvm.org/docs/GettingStarted.html +- https://llvm.org/docs/CMake.html +- https://apt.llvm.org/ +- https://www.archlinux.org/packages/extra/x86_64/llvm/ +- https://github.com/ClangBuiltLinux/tc-build +- https://github.com/ClangBuiltLinux/linux/wiki/Building-Clang-from-source +- https://android.googlesource.com/platform/prebuilts/clang/host/linux-x86/ |