[PATCH 2/2] Kconfig: CC_HAS_NO_PROFILE_FN_ATTR, depend on for GCOV and PGO

Nick Desaulniers
2021-06-18T23:30:54Z

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@kernel.org>
Cc: Peter Oberparleiter <oberpar@linux.ibm.com>
Link: https://lore.kernel.org/lkml/YMTn9yjuemKFLbws@hirez.programming.kicks-ass.net/
Link: https://lore.kernel.org/lkml/YMcssV%2Fn5IBGv4f0@hirez.programming.kicks-ass.net/
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
---
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)
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