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| author | Hannes Frederic Sowa <hannes@stressinduktion.org> | 2013-10-19 23:48:53 +0400 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2013-10-20 03:45:35 +0400 |
| commit | c4b2c0c5f647aa1093e8f9097a30c17ce0f94d4d (patch) | |
| tree | 37d56a25f147e626b68532543c8569a739f7fee3 /include/linux | |
| parent | b50026b5ac8fe2932e6af0c54b21da0913c4c1c7 (diff) | |
| download | linux-c4b2c0c5f647aa1093e8f9097a30c17ce0f94d4d.tar.xz | |
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 <rostedt@goodmis.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Andi Kleen <andi@firstfloor.org>
Signed-off-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'include/linux')
| -rw-r--r-- | include/linux/jump_label.h | 10 | ||||
| -rw-r--r-- | include/linux/jump_label_ratelimit.h | 2 |
2 files changed, 12 insertions, 0 deletions
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 <linux/types.h> #include <linux/compiler.h> +#include <linux/bug.h> + +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); } 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 */ |