From c4b2c0c5f647aa1093e8f9097a30c17ce0f94d4d Mon Sep 17 00:00:00 2001 From: Hannes Frederic Sowa Date: Sat, 19 Oct 2013 21:48:53 +0200 Subject: static_key: WARN on usage before jump_label_init was called Usage of the static key primitives to toggle a branch must not be used before jump_label_init() is called from init/main.c. jump_label_init reorganizes and wires up the jump_entries so usage before that could have unforeseen consequences. Following primitives are now checked for correct use: * static_key_slow_inc * static_key_slow_dec * static_key_slow_dec_deferred * jump_label_rate_limit The x86 architecture already checks this by testing if the default_nop was already replaced with an optimal nop or with a branch instruction. It will panic then. Other architectures don't check for this. Because we need to relax this check for the x86 arch to allow code to transition from default_nop to the enabled state and other architectures did not check for this at all this patch introduces checking on the static_key primitives in a non-arch dependent manner. All checked functions are considered slow-path so the additional check does no harm to performance. The warnings are best observed with earlyprintk. Based on a patch from Andi Kleen. Cc: Steven Rostedt Cc: Peter Zijlstra Cc: Andi Kleen Signed-off-by: Hannes Frederic Sowa Signed-off-by: David S. Miller --- include/linux/jump_label_ratelimit.h | 2 ++ 1 file changed, 2 insertions(+) (limited to 'include/linux/jump_label_ratelimit.h') diff --git a/include/linux/jump_label_ratelimit.h b/include/linux/jump_label_ratelimit.h index 113788389b3d..089f70f83e97 100644 --- a/include/linux/jump_label_ratelimit.h +++ b/include/linux/jump_label_ratelimit.h @@ -23,12 +23,14 @@ struct static_key_deferred { }; static inline void static_key_slow_dec_deferred(struct static_key_deferred *key) { + STATIC_KEY_CHECK_USE(); static_key_slow_dec(&key->key); } static inline void jump_label_rate_limit(struct static_key_deferred *key, unsigned long rl) { + STATIC_KEY_CHECK_USE(); } #endif /* HAVE_JUMP_LABEL */ #endif /* _LINUX_JUMP_LABEL_RATELIMIT_H */ -- cgit v1.2.3-59-g8ed1b