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.h | 10 ++++++++++ 1 file changed, 10 insertions(+) (limited to 'include/linux/jump_label.h') diff --git a/include/linux/jump_label.h b/include/linux/jump_label.h index a5079072da66..e96be7245717 100644 --- a/include/linux/jump_label.h +++ b/include/linux/jump_label.h @@ -48,6 +48,13 @@ #include #include +#include + +extern bool static_key_initialized; + +#define STATIC_KEY_CHECK_USE() WARN(!static_key_initialized, \ + "%s used before call to jump_label_init", \ + __func__) #if defined(CC_HAVE_ASM_GOTO) && defined(CONFIG_JUMP_LABEL) @@ -128,6 +135,7 @@ struct static_key { static __always_inline void jump_label_init(void) { + static_key_initialized = true; } static __always_inline bool static_key_false(struct static_key *key) @@ -146,11 +154,13 @@ static __always_inline bool static_key_true(struct static_key *key) static inline void static_key_slow_inc(struct static_key *key) { + STATIC_KEY_CHECK_USE(); atomic_inc(&key->enabled); } static inline void static_key_slow_dec(struct static_key *key) { + STATIC_KEY_CHECK_USE(); atomic_dec(&key->enabled); } -- cgit v1.2.3