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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. |