Kconfig: Introduce ARCH_WANTS_NO_INSTR and CC_HAS_NO_PROFILE_FN_ATTR

We don't want compiler instrumentation to touch noinstr functions,
which are annotated with the no_profile_instrument_function function
attribute. Add a Kconfig test for this and make GCOV depend on it, and
in the future, PGO.

If an architecture is using noinstr, it should denote that via this
Kconfig value. That makes Kconfigs that depend on noinstr able to express
dependencies in an architecturally agnostic way.

Cc: Masahiro Yamada <masahiroy@kernel.org>
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: Nathan Chancellor <nathan@kernel.org>
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Reviewed-by: Peter Oberparleiter <oberpar@linux.ibm.com>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Acked-by: Heiko Carstens <hca@linux.ibm.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20210621231822.2848305-4-ndesaulniers@google.com

diff --git a/arch/Kconfig b/arch/Kconfig
index c45b770d3579a3ef0ff9e482e452e88f40ade8b8..129df498a8e12c5d6e7da2ac14f9da3811e3d827 100644 (file)
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -285,6 +285,13 @@ config ARCH_THREAD_STACK_ALLOCATOR
 config ARCH_WANTS_DYNAMIC_TASK_STRUCT
        bool
 
+config ARCH_WANTS_NO_INSTR
+       bool
+       help
+         An architecture should select this if the noinstr macro is being used on
+         functions to denote that the toolchain should avoid instrumenting such
+         functions and is required for correctness.
+
 config ARCH_32BIT_OFF_T
        bool
        depends on !64BIT

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 9f1d8566bbf95c9e56c2f284482edab5d9d92cb7..39bf982b06f8dc787518b194e44d65cf052f9f0f 100644 (file)
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -93,6 +93,7 @@ config ARM64
        select ARCH_WANT_FRAME_POINTERS
        select ARCH_WANT_HUGE_PMD_SHARE if ARM64_4K_PAGES || (ARM64_16K_PAGES && !ARM64_VA_BITS_36)
        select ARCH_WANT_LD_ORPHAN_WARN
+       select ARCH_WANTS_NO_INSTR
        select ARCH_HAS_UBSAN_SANITIZE_ALL
        select ARM_AMBA
        select ARM_ARCH_TIMER

diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
index b4c7c34069f81a0e52e0cc4cefafbf381113fad5..bd60310f33b9d80f018640afd10762ff7dc7237e 100644 (file)
--- a/arch/s390/Kconfig
+++ b/arch/s390/Kconfig
@@ -117,6 +117,7 @@ config S390
        select ARCH_USE_BUILTIN_BSWAP
        select ARCH_USE_CMPXCHG_LOCKREF
        select ARCH_WANTS_DYNAMIC_TASK_STRUCT
+       select ARCH_WANTS_NO_INSTR
        select ARCH_WANT_DEFAULT_BPF_JIT
        select ARCH_WANT_IPC_PARSE_VERSION
        select BUILDTIME_TABLE_SORT

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 12fa0d7bfa644b2efd91d5bc17157831843c68f2..268a5dec8b3f6299786303225f1815db8c3406be 100644 (file)
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -113,6 +113,7 @@ config X86
        select ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
        select ARCH_WANT_DEFAULT_BPF_JIT        if X86_64
        select ARCH_WANTS_DYNAMIC_TASK_STRUCT
+       select ARCH_WANTS_NO_INSTR
        select ARCH_WANT_HUGE_PMD_SHARE
        select ARCH_WANT_LD_ORPHAN_WARN
        select ARCH_WANTS_THP_SWAP              if X86_64

diff --git a/init/Kconfig b/init/Kconfig
index 1ea12c64e4c9f3662bc8b76bd8760295ec735dc8..31397a7a45fb7a955e2e95405ee08017f47697cb 100644 (file)
--- 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_instrument_function)) int x();' | $(CC) -x c - -c -o /dev/null -Werror)
+
 config CONSTRUCTORS
        bool
 

diff --git a/kernel/gcov/Kconfig b/kernel/gcov/Kconfig
index 58f87a3092f320bf002cf3272b2e8223ac106b68..053447183ac5b44591bb9091878103e02ecb684f 100644 (file)
--- 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 !ARCH_WANTS_NO_INSTR || CC_HAS_NO_PROFILE_FN_ATTR
        select CONSTRUCTORS
        default n
        help