diff options
| author | Hannes Frederic Sowa <hannes@stressinduktion.org> | 2013-10-19 21:48:53 +0200 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2013-10-19 19:45:35 -0400 |
| commit | c4b2c0c5f647aa1093e8f9097a30c17ce0f94d4d (patch) | |
| tree | 37d56a25f147e626b68532543c8569a739f7fee3 /init/main.c | |
| parent | b50026b5ac8fe2932e6af0c54b21da0913c4c1c7 (diff) | |
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/main.c')
| -rw-r--r-- | init/main.c | 7 |
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. |