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 c45b770..129df49 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 9f1d856..39bf982 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 b4c7c34..bd60310 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 12fa0d7..268a5de 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 1ea12c6..31397a7 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 58f87a3..0534471 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