tree 5997b7318d7e41cf07bc27c3a828481f745d5fab
parent 9c01fe4593db123c5a72dc36f0400f776e92c954
author Steven Rostedt (Red Hat) <rostedt@goodmis.org> 1374631575 -0400
committer Steven Rostedt <rostedt@rostedt.homelinux.com> 1374679374 -0400

ftrace: Add check for NULL regs if ops has SAVE_REGS set

If a ftrace ops is registered with the SAVE_REGS flag set, and there's
already a ops registered to one of its functions but without the
SAVE_REGS flag, there's a small race window where the SAVE_REGS ops gets
added to the list of callbacks to call for that function before the
callback trampoline gets set to save the regs.

The problem is, the function is not currently saving regs, which opens
a small race window where the ops that is expecting regs to be passed
to it, wont. This can cause a crash if the callback were to reference
the regs, as the SAVE_REGS guarantees that regs will be set.

To fix this, we add a check in the loop case where it checks if the ops
has the SAVE_REGS flag set, and if so, it will ignore it if regs is
not set.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>