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authorHannes Frederic Sowa <hannes@stressinduktion.org>2013-10-19 23:48:53 +0400
committerDavid S. Miller <davem@davemloft.net>2013-10-20 03:45:35 +0400
commitc4b2c0c5f647aa1093e8f9097a30c17ce0f94d4d (patch)
tree37d56a25f147e626b68532543c8569a739f7fee3 /include/linux/jump_label.h
parentb50026b5ac8fe2932e6af0c54b21da0913c4c1c7 (diff)
downloadlinux-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/jump_label.h')
-rw-r--r--include/linux/jump_label.h10
1 files changed, 10 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);
}