=========================
|
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.
|
