kcov: add __no_sanitize_coverage to fix noinstr for all architectures

Until now no compiler supported an attribute to disable coverage
instrumentation as used by KCOV.

To work around this limitation on x86, noinstr functions have their
coverage instrumentation turned into nops by objtool.  However, this
solution doesn't scale automatically to other architectures, such as
arm64, which are migrating to use the generic entry code.

Clang [1] and GCC [2] have added support for the attribute recently.
[1] https://github.com/llvm/llvm-project/commit/280333021e9550d80f5c1152a34e33e81df1e178
[2] https://gcc.gnu.org/git/?p=gcc.git;a=commit;h=cec4d4a6782c9bd8d071839c50a239c49caca689
The changes will appear in Clang 13 and GCC 12.

Add __no_sanitize_coverage for both compilers, and add it to noinstr.

Note: In the Clang case, __has_feature(coverage_sanitizer) is only true if
the feature is enabled, and therefore we do not require an additional
defined(CONFIG_KCOV) (like in the GCC case where __has_attribute(..) is
always true) to avoid adding redundant attributes to functions if KCOV is
off.  That being said, compilers that support the attribute will not
generate errors/warnings if the attribute is redundantly used; however,
where possible let's avoid it as it reduces preprocessed code size and
associated compile-time overheads.

Link: https://lkml.kernel.org/r/20210525175819.699786-1-elver@google.com
Signed-off-by: Marco Elver <elver@google.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Miguel Ojeda <ojeda@kernel.org>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Will Deacon <will@kernel.org>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
Cc: Arvind Sankar <nivedita@alum.mit.edu>
Cc: Masahiro Yamada <masahiroy@kernel.org>
Cc: Sami Tolvanen <samitolvanen@google.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>

diff --git a/include/linux/compiler-clang.h b/include/linux/compiler-clang.h
index adbe76b203e2fd27356d7cb772542c4e22e23ca1..370565f4cfde817166d7b8e782cadc561d092c85 100644 (file)
--- a/include/linux/compiler-clang.h
+++ b/include/linux/compiler-clang.h
@@ -45,6 +45,12 @@
 #define __no_sanitize_undefined
 #endif
 
+#if defined(CONFIG_KCOV) && CONFIG_CLANG_VERSION >= 130000
+#define __no_sanitize_coverage __attribute__((no_sanitize("coverage")))
+#else
+#define __no_sanitize_coverage
+#endif
+
 /*
  * Not all versions of clang implement the type-generic versions
  * of the builtin overflow checkers. Fortunately, clang implements

diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h
index 5d97ef738a575e0232c5325d7afc55b45aed009f..cb9217fc60af0a29ca9d95eecd7ef63ed4922f5a 100644 (file)
--- a/include/linux/compiler-gcc.h
+++ b/include/linux/compiler-gcc.h
@@ -122,6 +122,12 @@
 #define __no_sanitize_undefined
 #endif
 
+#if defined(CONFIG_KCOV) && __has_attribute(__no_sanitize_coverage__)
+#define __no_sanitize_coverage __attribute__((no_sanitize_coverage))
+#else
+#define __no_sanitize_coverage
+#endif
+
 #if GCC_VERSION >= 50100
 #define COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW 1
 #endif

diff --git a/include/linux/compiler_types.h b/include/linux/compiler_types.h
index d29bda7f6ebddf8141443801ceb553b3f57eb934..cc2bee7f097776b5eed49faba902c58399f49e15 100644 (file)
--- 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_sanitize_coverage
 
 #endif /* __KERNEL__ */