Commit 4855022a authored by Josh Poimboeuf's avatar Josh Poimboeuf Committed by Ingo Molnar

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: default avatarMike Galbraith <efault@gmx.de>
Signed-off-by: default avatarJosh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/96cc8ecbcdd8cb29ddd783817b4af918a6a171b0.1499437107.git.jpoimboe@redhat.comSigned-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 4422d80e
...@@ -1371,6 +1371,12 @@ static int validate_branch(struct objtool_file *file, struct instruction *first, ...@@ -1371,6 +1371,12 @@ static int validate_branch(struct objtool_file *file, struct instruction *first,
func = insn->func; 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->visited) {
if (!!insn_state_match(insn, &state)) if (!!insn_state_match(insn, &state))
return 1; return 1;
...@@ -1426,16 +1432,19 @@ static int validate_branch(struct objtool_file *file, struct instruction *first, ...@@ -1426,16 +1432,19 @@ static int validate_branch(struct objtool_file *file, struct instruction *first,
case INSN_JUMP_CONDITIONAL: case INSN_JUMP_CONDITIONAL:
case INSN_JUMP_UNCONDITIONAL: 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, ret = validate_branch(file, insn->jump_dest,
state); state);
if (ret) if (ret)
return 1; return 1;
} else if (func && has_modified_stack_frame(&state)) { } else if (func && has_modified_stack_frame(&state)) {
WARN_FUNC("sibling call from callable instruction with modified stack frame", WARN_FUNC("sibling call from callable instruction with modified stack frame",
sec, insn->offset); sec, insn->offset);
return 1; return 1;
} /* else it's a sibling call */ }
if (insn->type == INSN_JUMP_UNCONDITIONAL) if (insn->type == INSN_JUMP_UNCONDITIONAL)
return 0; return 0;
......
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