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