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 <efa...@gmx.de>
Signed-off-by: Josh Poimboeuf <jpoim...@redhat.com>
---
tools/objtool/check.c | 13 +++++++++++--
1 file changed, 11 insertions(+), 2 deletions(-)
diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index fea2221..2c6d748 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -1371,6 +1371,12 @@ static int validate_branch(struct objtool_file *file,
struct instruction *first,
func = insn->func;
+ if (func && insn->ignore) {
+ WARN_FUNC("BUG: why am I validating an ignored
function?",
+ sec, insn->offset);
+ return -1;
+ }
+
if (insn->visited) {
if (!!insn_state_match(insn, &state))
return 1;
@@ -1426,16 +1432,19 @@ static int validate_branch(struct objtool_file *file,
struct instruction *first,
case INSN_JUMP_CONDITIONAL:
case INSN_JUMP_UNCONDITIONAL:
- if (insn->jump_dest) {
+ if (insn->jump_dest &&
+ (!func || !insn->jump_dest->func ||
+ func == insn->jump_dest->func)) {
ret = validate_branch(file, insn->jump_dest,
state);
if (ret)
return 1;
+
} else if (func && has_modified_stack_frame(&state)) {
WARN_FUNC("sibling call from callable
instruction with modified stack frame",
sec, insn->offset);
return 1;
- } /* else it's a sibling call */
+ }
if (insn->type == INSN_JUMP_UNCONDITIONAL)
return 0;
--
2.7.5
