projects / deliverable / linux.git / blame
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| 6b90bd4b ER |
1 | GCC plugin infrastructure |
| 2 | ========================= | |
| 3 | ||
| 4 | ||
| 5 | 1. Introduction | |
| 6 | =============== | |
| 7 | ||
| 8 | GCC plugins are loadable modules that provide extra features to the | |
| 9 | compiler [1]. They are useful for runtime instrumentation and static analysis. | |
| 10 | We can analyse, change and add further code during compilation via | |
| 11 | callbacks [2], GIMPLE [3], IPA [4] and RTL passes [5]. | |
| 12 | ||
| 13 | The GCC plugin infrastructure of the kernel supports all gcc versions from | |
| 14 | 4.5 to 6.0, building out-of-tree modules, cross-compilation and building in a | |
| 15 | separate directory. | |
| 16 | Plugin source files have to be compilable by both a C and a C++ compiler as well | |
| 17 | because gcc versions 4.5 and 4.6 are compiled by a C compiler, | |
| 18 | gcc-4.7 can be compiled by a C or a C++ compiler, | |
| 19 | and versions 4.8+ can only be compiled by a C++ compiler. | |
| 20 | ||
| 21 | Currently the GCC plugin infrastructure supports only the x86, arm and arm64 | |
| 22 | architectures. | |
| 23 | ||
| 24 | This 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 | ||
| 36 | 2. 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 | ||
| 61 | 3. Usage | |
| 62 | ======== | |
| 63 | ||
| 64 | You must install the gcc plugin headers for your gcc version, | |
| 65 | e.g., on Ubuntu for gcc-4.9: | |
| 66 | ||
| 67 | apt-get install gcc-4.9-plugin-dev | |
| 68 | ||
| 69 | Enable a GCC plugin based feature in the kernel config: | |
| 70 | ||
| 71 | CONFIG_GCC_PLUGIN_CYC_COMPLEXITY = y | |
| 72 | ||
| 73 | To compile only the plugin(s): | |
| 74 | ||
| 75 | make gcc-plugins | |
| 76 | ||
| 77 | or just run the kernel make and compile the whole kernel with | |
| 78 | the cyclomatic complexity GCC plugin. | |
| 79 | ||
| 80 | ||
| 81 | 4. How to add a new GCC plugin | |
| 82 | ============================== | |
| 83 | ||
| 84 | The GCC plugins are in $(src)/scripts/gcc-plugins/. You can use a file or a directory | |
| 85 | here. It must be added to $(src)/scripts/gcc-plugins/Makefile, | |
| 86 | $(src)/scripts/Makefile.gcc-plugins and $(src)/arch/Kconfig. | |
| 87 | See the cyc_complexity_plugin.c (CONFIG_GCC_PLUGIN_CYC_COMPLEXITY) GCC plugin. |