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1 =========================
2 GCC plugin infrastructure
3 =========================
4
5
6 Introduction
7 ============
8
9 GCC plugins are loadable modules that provide extra features to the
10 compiler [1]_. They are useful for runtime instrumentation and static analysis.
11 We can analyse, change and add further code during compilation via
12 callbacks [2]_, GIMPLE [3]_, IPA [4]_ and RTL passes [5]_.
13
14 The GCC plugin infrastructure of the kernel supports all gcc versions from
15 4.5 to 6.0, building out-of-tree modules, cross-compilation and building in a
16 separate directory.
17 Plugin source files have to be compilable by both a C and a C++ compiler as well
18 because gcc versions 4.5 and 4.6 are compiled by a C compiler,
19 gcc-4.7 can be compiled by a C or a C++ compiler,
20 and versions 4.8+ can only be compiled by a C++ compiler.
21
22 Currently the GCC plugin infrastructure supports only the x86, arm, arm64 and
23 powerpc architectures.
24
25 This 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
38 Files
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
67 Usage
68 =====
69
70 You must install the gcc plugin headers for your gcc version,
71 e.g., on Ubuntu for gcc-4.9::
72
73 apt-get install gcc-4.9-plugin-dev
74
75 Enable a GCC plugin based feature in the kernel config::
76
77 CONFIG_GCC_PLUGIN_CYC_COMPLEXITY = y
78
79 To compile only the plugin(s)::
80
81 make gcc-plugins
82
83 or just run the kernel make and compile the whole kernel with
84 the cyclomatic complexity GCC plugin.
85
86
87 4. How to add a new GCC plugin
88 ==============================
89
90 The GCC plugins are in $(src)/scripts/gcc-plugins/. You can use a file or a directory
91 here. It must be added to $(src)/scripts/gcc-plugins/Makefile,
92 $(src)/scripts/Makefile.gcc-plugins and $(src)/arch/Kconfig.
93 See the cyc_complexity_plugin.c (CONFIG_GCC_PLUGIN_CYC_COMPLEXITY) GCC plugin.