The kernel has been using noinstr for correctness to politely request that the compiler avoid adding various forms of instrumentation to certain functions. GCOV and PGO can both instrument functions, yet the function attribute to disable such instrumentation (no_profile_instrument_function) was not being used to suppress such implementation. Also, clang only just recently gained support for no_profile_instrument_function. GCC has supported that since 7.1+. Add a new function annotation __no_profile that expands to __attribute__((__no_profile_instrument_function__)) and Kconfig values CC_HAS_NO_PROFILE_FN_ATTR and ARCH_WANTS_NO_INSTR. Make GCOV and PGO depend on either !ARCH_WANTS_NO_INSTR or CC_HAS_NO_PROFILE_FN_ATTR. Changes V1 -> V2: * s/no_profile/no_profile_instrument_function/ * fix trailing double underscore on GCC 4 define, as per Fangrui+Miguel. * Pick up Fangrui + Miguel's reviewed-by tag. * Add link to GCC's doc. * Fix clang's doc format; will appear once clang-13 is released. * New cleanup patch 2/3. Orthogonal to the series, but while I'm here... Base is https://git.kernel.org/pub/scm/linux/kernel/git/kees/linux.git/log/?h=for-next/clang/pgo. Nick Desaulniers (3): compiler_attributes.h: define __no_profile, add to noinstr compiler_attributes.h: cleanups for GCC 4.9+ Kconfig: add ARCH_WANTS_NO_INSTR+CC_HAS_NO_PROFILE_FN_ATTR, depend on for GCOV and PGO arch/Kconfig | 7 +++++++ arch/arm64/Kconfig | 1 + arch/s390/Kconfig | 1 + arch/x86/Kconfig | 1 + include/linux/compiler_attributes.h | 19 ++++++++++++++++--- include/linux/compiler_types.h | 2 +- init/Kconfig | 3 +++ kernel/gcov/Kconfig | 1 + kernel/pgo/Kconfig | 3 ++- 9 files changed, 33 insertions(+), 5 deletions(-) base-commit: 4356bc4c0425c81e204f561acf4dd0095544a6cb -- 2.32.0.288.g62a8d224e6-goog
