| | 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. |
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