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authorHannes Frederic Sowa <hannes@stressinduktion.org>2013-10-19 21:48:53 +0200
committerDavid S. Miller <davem@davemloft.net>2013-10-19 19:45:35 -0400
commitc4b2c0c5f647aa1093e8f9097a30c17ce0f94d4d (patch)
tree37d56a25f147e626b68532543c8569a739f7fee3 /init
parentb50026b5ac8fe2932e6af0c54b21da0913c4c1c7 (diff)
downloadlinux-linaro-stable-c4b2c0c5f647aa1093e8f9097a30c17ce0f94d4d.tar.gz
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 'init')
-rw-r--r--init/main.c7
1 files changed, 7 insertions, 0 deletions
diff --git a/init/main.c b/init/main.c
index af310afbef28..27bbec1a5b35 100644
--- a/init/main.c
+++ b/init/main.c
@@ -136,6 +136,13 @@ static char *execute_command;
static char *ramdisk_execute_command;
/*
+ * Used to generate warnings if static_key manipulation functions are used
+ * before jump_label_init is called.
+ */
+bool static_key_initialized __read_mostly = false;
+EXPORT_SYMBOL_GPL(static_key_initialized);
+
+/*
* If set, this is an indication to the drivers that reset the underlying
* device before going ahead with the initialization otherwise driver might
* rely on the BIOS and skip the reset operation.