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94 lines
2.9 KiB
Plaintext
94 lines
2.9 KiB
Plaintext
=========================
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GCC plugin infrastructure
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=========================
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Introduction
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============
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GCC plugins are loadable modules that provide extra features to the
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compiler [1]_. They are useful for runtime instrumentation and static analysis.
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We can analyse, change and add further code during compilation via
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callbacks [2]_, GIMPLE [3]_, IPA [4]_ and RTL passes [5]_.
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The GCC plugin infrastructure of the kernel supports all gcc versions from
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4.5 to 6.0, building out-of-tree modules, cross-compilation and building in a
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separate directory.
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Plugin source files have to be compilable by both a C and a C++ compiler as well
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because gcc versions 4.5 and 4.6 are compiled by a C compiler,
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gcc-4.7 can be compiled by a C or a C++ compiler,
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and versions 4.8+ can only be compiled by a C++ compiler.
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Currently the GCC plugin infrastructure supports only the x86, arm, arm64 and
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powerpc architectures.
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This infrastructure was ported from grsecurity [6]_ and PaX [7]_.
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--
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.. [1] https://gcc.gnu.org/onlinedocs/gccint/Plugins.html
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.. [2] https://gcc.gnu.org/onlinedocs/gccint/Plugin-API.html#Plugin-API
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.. [3] https://gcc.gnu.org/onlinedocs/gccint/GIMPLE.html
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.. [4] https://gcc.gnu.org/onlinedocs/gccint/IPA.html
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.. [5] https://gcc.gnu.org/onlinedocs/gccint/RTL.html
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.. [6] https://grsecurity.net/
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.. [7] https://pax.grsecurity.net/
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Files
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=====
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**$(src)/scripts/gcc-plugins**
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This is the directory of the GCC plugins.
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**$(src)/scripts/gcc-plugins/gcc-common.h**
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This is a compatibility header for GCC plugins.
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It should be always included instead of individual gcc headers.
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**$(src)/scripts/gcc-plugin.sh**
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This script checks the availability of the included headers in
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gcc-common.h and chooses the proper host compiler to build the plugins
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(gcc-4.7 can be built by either gcc or g++).
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**$(src)/scripts/gcc-plugins/gcc-generate-gimple-pass.h,
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$(src)/scripts/gcc-plugins/gcc-generate-ipa-pass.h,
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$(src)/scripts/gcc-plugins/gcc-generate-simple_ipa-pass.h,
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$(src)/scripts/gcc-plugins/gcc-generate-rtl-pass.h**
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These headers automatically generate the registration structures for
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GIMPLE, SIMPLE_IPA, IPA and RTL passes. They support all gcc versions
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from 4.5 to 6.0.
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They should be preferred to creating the structures by hand.
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Usage
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=====
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You must install the gcc plugin headers for your gcc version,
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e.g., on Ubuntu for gcc-4.9::
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apt-get install gcc-4.9-plugin-dev
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Enable a GCC plugin based feature in the kernel config::
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CONFIG_GCC_PLUGIN_CYC_COMPLEXITY = y
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To compile only the plugin(s)::
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make gcc-plugins
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or just run the kernel make and compile the whole kernel with
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the cyclomatic complexity GCC plugin.
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4. How to add a new GCC plugin
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==============================
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The GCC plugins are in $(src)/scripts/gcc-plugins/. You can use a file or a directory
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here. It must be added to $(src)/scripts/gcc-plugins/Makefile,
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$(src)/scripts/Makefile.gcc-plugins and $(src)/arch/Kconfig.
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See the cyc_complexity_plugin.c (CONFIG_GCC_PLUGIN_CYC_COMPLEXITY) GCC plugin.
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