1=========================
2GCC plugin infrastructure
3=========================
4
5
6Introduction
7============
8
9GCC plugins are loadable modules that provide extra features to the
10compiler [1]_. They are useful for runtime instrumentation and static analysis.
11We can analyse, change and add further code during compilation via
12callbacks [2]_, GIMPLE [3]_, IPA [4]_ and RTL passes [5]_.
13
14The GCC plugin infrastructure of the kernel supports all gcc versions from
154.5 to 6.0, building out-of-tree modules, cross-compilation and building in a
16separate directory.
17Plugin source files have to be compilable by both a C and a C++ compiler as well
18because gcc versions 4.5 and 4.6 are compiled by a C compiler,
19gcc-4.7 can be compiled by a C or a C++ compiler,
20and versions 4.8+ can only be compiled by a C++ compiler.
21
22Currently the GCC plugin infrastructure supports only the x86, arm, arm64 and
23powerpc architectures.
24
25This infrastructure was ported from grsecurity [6]_ and PaX [7]_.
26
27--
28
29.. [1] https://gcc.gnu.org/onlinedocs/gccint/Plugins.html
30.. [2] https://gcc.gnu.org/onlinedocs/gccint/Plugin-API.html#Plugin-API
31.. [3] https://gcc.gnu.org/onlinedocs/gccint/GIMPLE.html
32.. [4] https://gcc.gnu.org/onlinedocs/gccint/IPA.html
33.. [5] https://gcc.gnu.org/onlinedocs/gccint/RTL.html
34.. [6] https://grsecurity.net/
35.. [7] https://pax.grsecurity.net/
36
37
38Files
39=====
40
41**$(src)/scripts/gcc-plugins**
42
43	This is the directory of the GCC plugins.
44
45**$(src)/scripts/gcc-plugins/gcc-common.h**
46
47	This is a compatibility header for GCC plugins.
48	It should be always included instead of individual gcc headers.
49
50**$(src)/scripts/gcc-plugin.sh**
51
52	This script checks the availability of the included headers in
53	gcc-common.h and chooses the proper host compiler to build the plugins
54	(gcc-4.7 can be built by either gcc or g++).
55
56**$(src)/scripts/gcc-plugins/gcc-generate-gimple-pass.h,
57$(src)/scripts/gcc-plugins/gcc-generate-ipa-pass.h,
58$(src)/scripts/gcc-plugins/gcc-generate-simple_ipa-pass.h,
59$(src)/scripts/gcc-plugins/gcc-generate-rtl-pass.h**
60
61	These headers automatically generate the registration structures for
62	GIMPLE, SIMPLE_IPA, IPA and RTL passes. They support all gcc versions
63	from 4.5 to 6.0.
64	They should be preferred to creating the structures by hand.
65
66
67Usage
68=====
69
70You must install the gcc plugin headers for your gcc version,
71e.g., on Ubuntu for gcc-4.9::
72
73	apt-get install gcc-4.9-plugin-dev
74
75Enable a GCC plugin based feature in the kernel config::
76
77	CONFIG_GCC_PLUGIN_CYC_COMPLEXITY = y
78
79To compile only the plugin(s)::
80
81	make gcc-plugins
82
83or just run the kernel make and compile the whole kernel with
84the cyclomatic complexity GCC plugin.
85
86
874. How to add a new GCC plugin
88==============================
89
90The GCC plugins are in $(src)/scripts/gcc-plugins/. You can use a file or a directory
91here. It must be added to $(src)/scripts/gcc-plugins/Makefile,
92$(src)/scripts/Makefile.gcc-plugins and $(src)/arch/Kconfig.
93See the cyc_complexity_plugin.c (CONFIG_GCC_PLUGIN_CYC_COMPLEXITY) GCC plugin.
94