mirror of https://github.com/Qortal/Brooklyn
You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
116 lines
3.7 KiB
116 lines
3.7 KiB
========================= |
|
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/ |
|
|
|
|
|
Purpose |
|
======= |
|
|
|
GCC plugins are designed to provide a place to experiment with potential |
|
compiler features that are neither in GCC nor Clang upstream. Once |
|
their utility is proven, the goal is to upstream the feature into GCC |
|
(and Clang), and then to finally remove them from the kernel once the |
|
feature is available in all supported versions of GCC. |
|
|
|
Specifically, new plugins should implement only features that have no |
|
upstream compiler support (in either GCC or Clang). |
|
|
|
When a feature exists in Clang but not GCC, effort should be made to |
|
bring the feature to upstream GCC (rather than just as a kernel-specific |
|
GCC plugin), so the entire ecosystem can benefit from it. |
|
|
|
Similarly, even if a feature provided by a GCC plugin does *not* exist |
|
in Clang, but the feature is proven to be useful, effort should be spent |
|
to upstream the feature to GCC (and Clang). |
|
|
|
After a feature is available in upstream GCC, the plugin will be made |
|
unbuildable for the corresponding GCC version (and later). Once all |
|
kernel-supported versions of GCC provide the feature, the plugin will |
|
be removed from the kernel. |
|
|
|
|
|
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_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.
|
|
|