objtool: Fix sibling call detection logic

With some configs, objtool reports the following warning:

  arch/x86/kernel/ftrace.o: warning: objtool: ftrace_modify_code_direct()+0x2d: sibling call from callable instruction with modified stack frame

The instruction it's complaining about isn't actually a sibling call.
It's just a normal jump to an address inside the function.  Objtool
thought it was a sibling call because the instruction's jump_dest wasn't
initialized because the function was supposed to be ignored due to its
use of sync_core().

Objtool ended up validating the function instead of ignoring it because
it didn't properly recognize a sibling call to the function.  So fix the
sibling call logic.  Also add a warning to catch ignored functions being
validated so we'll get a more useful error message next time.

Reported-by: Mike Galbraith <[email protected]>
Signed-off-by: Josh Poimboeuf <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Link: http://lkml.kernel.org/r/96cc8ecbcdd8cb29ddd783817b4af918a6a171b0.1499437107.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar <[email protected]>

0 files changed, 0 insertions, 0 deletions