GCC plugin infrastructure¶
GCC plugins are loadable modules that provide extra features to the compiler . They are useful for runtime instrumentation and static analysis. We can analyse, change and add further code during compilation via callbacks , GIMPLE , IPA  and RTL passes .
The GCC plugin infrastructure of the kernel supports building out-of-tree modules, cross-compilation and building in a separate directory. Plugin source files have to be compilable by a C++ compiler.
Currently the GCC plugin infrastructure supports only some architectures. Grep “select HAVE_GCC_PLUGINS” to find out which architectures support GCC plugins.
This is the directory of the GCC plugins.
This is a compatibility header for GCC plugins. It should be always included instead of individual gcc headers.
$(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 should be preferred to creating the structures by hand.
You must install the gcc plugin headers for your gcc version, e.g., on Ubuntu for gcc-10:
apt-get install gcc-10-plugin-dev
Or on Fedora:
dnf install gcc-plugin-devel
Enable the GCC plugin infrastructure and some plugin(s) you want to use in the kernel config:
CONFIG_GCC_PLUGINS=y CONFIG_GCC_PLUGIN_CYC_COMPLEXITY=y CONFIG_GCC_PLUGIN_LATENT_ENTROPY=y ...
To compile the minimum tool set including the plugin(s):
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 scripts/gcc-plugins/. You need to put plugin source files right under scripts/gcc-plugins/. Creating subdirectories is not supported. It must be added to scripts/gcc-plugins/Makefile, scripts/Makefile.gcc-plugins and a relevant Kconfig file. See the cyc_complexity_plugin.c (CONFIG_GCC_PLUGIN_CYC_COMPLEXITY) GCC plugin.