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 --- init/main.c | 7 +++++++ 1 file changed, 7 insertions(+) (limited to 'init') diff --git a/init/main.c b/init/main.c index af310afbef28..27bbec1a5b35 100644 --- a/init/main.c +++ b/init/main.c @@ -135,6 +135,13 @@ static char *static_command_line; 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 -- cgit v1.2.3-70-g09d2