kprobes: Warn if optprobe handler tries to change execution path

kprobes: Warn if optprobe handler tries to change execution path

Warn if optprobe handler tries to change execution path.
As described in Documentation/kprobes.txt, with optprobe
user handler can not change instruction pointer. In that
case user must avoid optimizing the kprobes by setting
post_handler or break_handler.

Signed-off-by: Masami Hiramatsu <[email protected]>
Cc: Alexei Starovoitov <[email protected]>
Cc: Alexei Starovoitov <[email protected]>
Cc: Ananth N Mavinakayanahalli <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Paul E . McKenney <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Steven Rostedt <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Link: http://lkml.kernel.org/r/150581521955.32348.3615624715034787365.stgit@devbox
Signed-off-by: Ingo Molnar <[email protected]>