summaryrefslogtreecommitdiffstats
path: root/Documentation/kbuild/gcc-plugins.rst
diff options
context:
space:
mode:
authorJonathan Corbet <corbet@lwn.net>2020-03-02 15:24:04 -0700
committerJonathan Corbet <corbet@lwn.net>2020-03-10 11:20:46 -0600
commit2b4cbd5c950525b6d4d2cd384dcefdd95fedabe3 (patch)
treedd40dacd113a4fa407bada3b5369534632e3d2ce /Documentation/kbuild/gcc-plugins.rst
parent5e72017279957b764c225f143c16391b3c51f225 (diff)
docs: move gcc-plugins to the kbuild manual
Information about GCC plugins is relevant to kernel building, so move this document to the kbuild manual. Acked-by: Masahiro Yamada <masahiroy@kernel.org> Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Diffstat (limited to 'Documentation/kbuild/gcc-plugins.rst')
-rw-r--r--Documentation/kbuild/gcc-plugins.rst97
1 files changed, 97 insertions, 0 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.