On Sat, 19 Jun 2021 at 01:30, Nick Desaulniers <ndesaulniers@xxxxxxxxxx> wrote: > > We don't want compiler instrumentation to touch noinstr functions, which > are annotated with the no_profile function attribute. Add a Kconfig test > for this and make PGO and GCOV depend on it. > > Cc: Masahiro Yamada <masahiroy@xxxxxxxxxx> > Cc: Peter Oberparleiter <oberpar@xxxxxxxxxxxxx> > Link: https://lore.kernel.org/lkml/YMTn9yjuemKFLbws@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/ > Link: https://lore.kernel.org/lkml/YMcssV%2Fn5IBGv4f0@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/ > Suggested-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx> > Signed-off-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx> > --- > init/Kconfig | 3 +++ > kernel/gcov/Kconfig | 1 + > kernel/pgo/Kconfig | 3 ++- > 3 files changed, 6 insertions(+), 1 deletion(-) > > diff --git a/init/Kconfig b/init/Kconfig > index 1ea12c64e4c9..540f862b40c6 100644 > --- a/init/Kconfig > +++ b/init/Kconfig > @@ -83,6 +83,9 @@ config TOOLS_SUPPORT_RELR > config CC_HAS_ASM_INLINE > def_bool $(success,echo 'void foo(void) { asm inline (""); }' | $(CC) -x c - -c -o /dev/null) > > +config CC_HAS_NO_PROFILE_FN_ATTR > + def_bool $(success,echo '__attribute__((no_profile)) int x();' | $(CC) -x c - -c -o /dev/null -Werror) > + > config CONSTRUCTORS > bool > > diff --git a/kernel/gcov/Kconfig b/kernel/gcov/Kconfig > index 58f87a3092f3..19facd4289cd 100644 > --- a/kernel/gcov/Kconfig > +++ b/kernel/gcov/Kconfig > @@ -5,6 +5,7 @@ config GCOV_KERNEL > bool "Enable gcov-based kernel profiling" > depends on DEBUG_FS > depends on !CC_IS_CLANG || CLANG_VERSION >= 110000 > + depends on !X86 || (X86 && CC_HAS_NO_PROFILE_FN_ATTR) [+Cc Mark] arm64 is also starting to rely on noinstr working properly. This should probably be a 'select ARCH_HAS_GCOV_PROFILE_ALL if CC_HAS_NO_PROFILE_FN_ATTR' in the relevant arch/../Kconfig. Alternatively, using: https://lkml.kernel.org/r/YMcssV/n5IBGv4f0@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx But I'd probably not overcomplicate things at this point and just use ARCH_HAS_GCOV_PROFILE_ALL, because GCOV seems to be a) rarely used, and b) if someone decides to selectively instrument stuff like entry code, we can just say it's user error. > select CONSTRUCTORS > default n > help > diff --git a/kernel/pgo/Kconfig b/kernel/pgo/Kconfig > index d2053df1111c..26f75ac4c6c1 100644 > --- a/kernel/pgo/Kconfig > +++ b/kernel/pgo/Kconfig > @@ -8,7 +8,8 @@ config PGO_CLANG > bool "Enable clang's PGO-based kernel profiling" > depends on DEBUG_FS > depends on ARCH_SUPPORTS_PGO_CLANG > - depends on CC_IS_CLANG && CLANG_VERSION >= 120000 > + depends on CC_IS_CLANG > + depends on CC_HAS_NO_PROFILE_FN_ATTR > help > This option enables clang's PGO (Profile Guided Optimization) based > code profiling to better optimize the kernel. > -- > 2.32.0.288.g62a8d224e6-goog >
