[PATCH -rcu/kcsan 2/2] kcsan: Add __no_kcsan function attribute

Marco Elver
2019-12-12T00:07:41Z

Since the use of -fsanitize=thread is an implementation detail of KCSAN,
the name __no_sanitize_thread could be misleading if used widely.
Instead, we introduce the __no_kcsan attribute which is shorter and more
accurate in the context of KCSAN.

This matches the attribute name __no_kcsan_or_inline. The use of
__kcsan_or_inline itself is still required for __always_inline functions
to retain compatibility with older compilers.

Signed-off-by: Marco Elver <elver@google.com>
---
include/linux/compiler-gcc.h | 3 +--
include/linux/compiler.h | 7 +++++--
2 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h
index 0eb2a1cc411d..cf294faec2f8 100644
--- a/include/linux/compiler-gcc.h
+++ b/include/linux/compiler-gcc.h
@@ -146,8 +146,7 @@
#endif

#if defined(__SANITIZE_THREAD__) && __has_attribute(__no_sanitize_thread__)
-#define __no_sanitize_thread \
- __attribute__((__noinline__)) __attribute__((no_sanitize_thread))
+#define __no_sanitize_thread __attribute__((no_sanitize_thread))
#else
#define __no_sanitize_thread
#endif
diff --git a/include/linux/compiler.h b/include/linux/compiler.h
index 7d3e77781578..a35d5493eeaa 100644
--- a/include/linux/compiler.h
+++ b/include/linux/compiler.h
@@ -207,12 +207,15 @@ void ftrace_likely_update(struct ftrace_likely_data *f, int val,
# define __no_kasan_or_inline __always_inline
#endif

+#define __no_kcsan __no_sanitize_thread
#ifdef __SANITIZE_THREAD__
/*
* Rely on __SANITIZE_THREAD__ instead of CONFIG_KCSAN, to avoid not inlining in
- * compilation units where instrumentation is disabled.
+ * compilation units where instrumentation is disabled. The attribute 'noinline'
+ * is required for older compilers, where implicit inlining of very small
+ * functions renders __no_sanitize_thread ineffective.
*/
-# define __no_kcsan_or_inline __no_sanitize_thread notrace __maybe_unused
+# define __no_kcsan_or_inline __no_kcsan noinline notrace __maybe_unused
# define __no_sanitize_or_inline __no_kcsan_or_inline
#else
# define __no_kcsan_or_inline __always_inline
--
2.24.0.525.g8f36a354ae-goog