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- =========================
- 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.
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