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Based on kernel version 4.9. Page generated on 2016-12-21 14:34 EST.

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