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1GCC plugin infrastructure
2=========================
3
4
51. Introduction
6===============
7
8GCC plugins are loadable modules that provide extra features to the
9compiler [1]. They are useful for runtime instrumentation and static analysis.
10We can analyse, change and add further code during compilation via
11callbacks [2], GIMPLE [3], IPA [4] and RTL passes [5].
12
13The GCC plugin infrastructure of the kernel supports all gcc versions from
144.5 to 6.0, building out-of-tree modules, cross-compilation and building in a
15separate directory.
16Plugin source files have to be compilable by both a C and a C++ compiler as well
17because gcc versions 4.5 and 4.6 are compiled by a C compiler,
18gcc-4.7 can be compiled by a C or a C++ compiler,
19and versions 4.8+ can only be compiled by a C++ compiler.
20
21Currently the GCC plugin infrastructure supports only the x86, arm and arm64
22architectures.
23
24This 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
362. 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
613. Usage
62========
63
64You must install the gcc plugin headers for your gcc version,
65e.g., on Ubuntu for gcc-4.9:
66
67 apt-get install gcc-4.9-plugin-dev
68
69Enable a GCC plugin based feature in the kernel config:
70
71 CONFIG_GCC_PLUGIN_CYC_COMPLEXITY = y
72
73To compile only the plugin(s):
74
75 make gcc-plugins
76
77or just run the kernel make and compile the whole kernel with
78the cyclomatic complexity GCC plugin.
79
80
814. How to add a new GCC plugin
82==============================
83
84The GCC plugins are in $(src)/scripts/gcc-plugins/. You can use a file or a directory
85here. It must be added to $(src)/scripts/gcc-plugins/Makefile,
86$(src)/scripts/Makefile.gcc-plugins and $(src)/arch/Kconfig.
87See the cyc_complexity_plugin.c (CONFIG_GCC_PLUGIN_CYC_COMPLEXITY) GCC plugin.