========================= 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 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 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-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. Usage ===== 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):: make scripts 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.