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Subject[PATCH -rcu] kcsan: Turn barrier instrumentation into macros
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Some architectures use barriers in 'extern inline' functions, from which
we should not refer to static inline functions.

For example, building Alpha with gcc and W=1 shows:

./include/asm-generic/barrier.h:70:30: warning: 'kcsan_rmb' is static but used in inline function 'pmd_offset' which is not static
70 | #define smp_rmb() do { kcsan_rmb(); __smp_rmb(); } while (0)
| ^~~~~~~~~
./arch/alpha/include/asm/pgtable.h:293:9: note: in expansion of macro 'smp_rmb'
293 | smp_rmb(); /* see above */
| ^~~~~~~

Which seems to warn about 6.7.4#3 of the C standard:
"An inline definition of a function with external linkage shall not
contain a definition of a modifiable object with static or thread
storage duration, and shall not contain a reference to an identifier
with internal linkage."

Fix it by turning barrier instrumentation into macros, which matches
definitions in <asm/barrier.h>.

Perhaps we can revert this change in future, when there are no more
'extern inline' users left.

Link: https://lkml.kernel.org/r/202112041334.X44uWZXf-lkp@intel.com
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Marco Elver <elver@google.com>
---
include/linux/kcsan-checks.h | 24 +++++++++++++-----------
1 file changed, 13 insertions(+), 11 deletions(-)

diff --git a/include/linux/kcsan-checks.h b/include/linux/kcsan-checks.h
index 9d2c869167f2..92f3843d9ebb 100644
--- a/include/linux/kcsan-checks.h
+++ b/include/linux/kcsan-checks.h
@@ -241,28 +241,30 @@ static inline void __kcsan_disable_current(void) { }
* disabled with the __no_kcsan function attribute.
*
* Also see definition of __tsan_atomic_signal_fence() in kernel/kcsan/core.c.
+ *
+ * These are all macros, like <asm/barrier.h>, since some architectures use them
+ * in non-static inline functions.
*/
#define __KCSAN_BARRIER_TO_SIGNAL_FENCE(name) \
- static __always_inline void kcsan_##name(void) \
- { \
+ do { \
barrier(); \
__atomic_signal_fence(__KCSAN_BARRIER_TO_SIGNAL_FENCE_##name); \
barrier(); \
- }
-__KCSAN_BARRIER_TO_SIGNAL_FENCE(mb)
-__KCSAN_BARRIER_TO_SIGNAL_FENCE(wmb)
-__KCSAN_BARRIER_TO_SIGNAL_FENCE(rmb)
-__KCSAN_BARRIER_TO_SIGNAL_FENCE(release)
+ } while (0)
+#define kcsan_mb() __KCSAN_BARRIER_TO_SIGNAL_FENCE(mb)
+#define kcsan_wmb() __KCSAN_BARRIER_TO_SIGNAL_FENCE(wmb)
+#define kcsan_rmb() __KCSAN_BARRIER_TO_SIGNAL_FENCE(rmb)
+#define kcsan_release() __KCSAN_BARRIER_TO_SIGNAL_FENCE(release)
#elif defined(CONFIG_KCSAN_WEAK_MEMORY) && defined(__KCSAN_INSTRUMENT_BARRIERS__)
#define kcsan_mb __kcsan_mb
#define kcsan_wmb __kcsan_wmb
#define kcsan_rmb __kcsan_rmb
#define kcsan_release __kcsan_release
#else /* CONFIG_KCSAN_WEAK_MEMORY && ... */
-static inline void kcsan_mb(void) { }
-static inline void kcsan_wmb(void) { }
-static inline void kcsan_rmb(void) { }
-static inline void kcsan_release(void) { }
+#define kcsan_mb() do { } while (0)
+#define kcsan_wmb() do { } while (0)
+#define kcsan_rmb() do { } while (0)
+#define kcsan_release() do { } while (0)
#endif /* CONFIG_KCSAN_WEAK_MEMORY && ... */

/**
--
2.34.1.400.ga245620fadb-goog
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