objtool: Fix false positive warnings related to sibling calls

jpoimboe · Ingo Molnar · commit d8d1b2cb5854 · 2016-03-09T10:48:08.000+01:00
With some configs [1], objtool prints a bunch of false positive warnings like: arch/x86/events/core.o: warning: objtool: x86_del_exclusive()+0x0: frame pointer state mismatch For some reason this config has a bunch of sibling calls. When objtool follows a sibling call jump, it attempts to compare the frame pointer state. But it also accidentally compares the FENTRY state, resulting in a false positive warning. [1] https://lkml.kernel.org/r/20160308154909.GA20956@gmail.com Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Andy Lutomirski <luto@kernel.org> Cc: Arnaldo Carvalho de Melo <acme@infradead.org> Cc: Arnaldo Carvalho de Melo <acme@kernel.org> Cc: Bernd Petrovitsch <bernd@petrovitsch.priv.at> Cc: Borislav Petkov <bp@alien8.de> Cc: Chris J Arges <chris.j.arges@canonical.com> Cc: Jiri Slaby <jslaby@suse.cz> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Michal Marek <mmarek@suse.cz> Cc: Namhyung Kim <namhyung@gmail.com> Cc: Pedro Alves <palves@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: live-patching@vger.kernel.org Link: http://lkml.kernel.org/r/382de77ccaaa8cd79b27a155c3d109ebd4ce0219.1457502970.git.jpoimboe@redhat.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
diff --git a/tools/objtool/builtin-check.c b/tools/objtool/builtin-check.c
@@ -729,6 +729,11 @@ static bool has_valid_stack_frame(struct instruction *insn)
 	       (insn->state & STATE_FP_SETUP);
 }
 
+static unsigned int frame_state(unsigned long state)
+{
+	return (state & (STATE_FP_SAVED | STATE_FP_SETUP));
+}
+
 /*
  * Follow the branch starting at the given instruction, and recursively follow
  * any other branches (jumps).  Meanwhile, track the frame pointer state at
@@ -756,7 +761,7 @@ static int validate_branch(struct objtool_file *file,
 
 	while (1) {
 		if (insn->visited) {
-			if (insn->state != state) {
+			if (frame_state(insn->state) != frame_state(state)) {
 				WARN_FUNC("frame pointer state mismatch",
 					  sec, insn->offset);
 				warnings++;
