On 6/21/2021 4:18 PM, 'Nick Desaulniers' via Clang Built Linux wrote:
noinstr implies that we would like the compiler to avoid instrumenting a
function. Add support for the compiler attribute
no_profile_instrument_function to compiler_attributes.h, then add
__no_profile to the definition of noinstr.
Link: https://lore.kernel.org/lkml/20210614162018.GD68749@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/
Link: https://reviews.llvm.org/D104257
Link: https://reviews.llvm.org/D104475
Link: https://reviews.llvm.org/D104658
Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80223
Reviewed-by: Fangrui Song <maskray@xxxxxxxxxx>
Reviewed-by: Miguel Ojeda <ojeda@xxxxxxxxxx>
Suggested-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Signed-off-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx>
Reviewed-by: Nathan Chancellor <nathan@xxxxxxxxxx>
---
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.
include/linux/compiler_attributes.h | 13 +++++++++++++
include/linux/compiler_types.h | 2 +-
2 files changed, 14 insertions(+), 1 deletion(-)
diff --git a/include/linux/compiler_attributes.h b/include/linux/compiler_attributes.h
index c043b8d2b17b..225511b17223 100644
--- a/include/linux/compiler_attributes.h
+++ b/include/linux/compiler_attributes.h
@@ -33,6 +33,7 @@
# define __GCC4_has_attribute___externally_visible__ 1
# define __GCC4_has_attribute___no_caller_saved_registers__ 0
# define __GCC4_has_attribute___noclone__ 1
+# define __GCC4_has_attribute___no_profile_instrument_function__ 0
# define __GCC4_has_attribute___nonstring__ 0
# define __GCC4_has_attribute___no_sanitize_address__ (__GNUC_MINOR__ >= 8)
# define __GCC4_has_attribute___no_sanitize_undefined__ (__GNUC_MINOR__ >= 9)
@@ -237,6 +238,18 @@
# define __nonstring
#endif
+/*
+ * Optional: only supported since GCC >= 7.1, clang >= 13.0.
+ *
+ * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-no_005fprofile_005finstrument_005ffunction-function-attribute
+ * clang: https://clang.llvm.org/docs/AttributeReference.html#no-profile-instrument-function
+ */
+#if __has_attribute(__no_profile_instrument_function__)
+# define __no_profile __attribute__((__no_profile_instrument_function__))
+#else
+# define __no_profile
+#endif
+
/*
* gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noreturn-function-attribute
* clang: https://clang.llvm.org/docs/AttributeReference.html#noreturn
diff --git a/include/linux/compiler_types.h b/include/linux/compiler_types.h
index d29bda7f6ebd..d509169860f1 100644
--- a/include/linux/compiler_types.h
+++ b/include/linux/compiler_types.h
@@ -210,7 +210,7 @@ struct ftrace_likely_data {
/* Section for code which can't be instrumented at all */
#define noinstr \
noinline notrace __attribute((__section__(".noinstr.text"))) \
- __no_kcsan __no_sanitize_address
+ __no_kcsan __no_sanitize_address __no_profile
#endif /* __KERNEL__ */
