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objtool: Fix objtool fallthrough detection with function padding 

When GCC adds NOP padding between functions, those NOPs aren't
associated with a function symbol, which breaks objtool's detection of a
function falling through to another function.  Instead it shows
confusing errors like:

  drivers/mtd/chips/cfi_util.o: warning: objtool: cfi_qry_mode_on()+0x8b: return with modified stack frame
  drivers/mtd/chips/cfi_util.o: warning: objtool: cfi_qry_mode_on()+0x0: stack state mismatch: cfa1=-4-32 cfa2=7+8
  drivers/mtd/chips/cfi_cmdset_0002.o: warning: objtool: fixup_use_fwh_lock()+0x8: unknown stack-related register move
  drivers/mtd/chips/cfi_cmdset_0002.o: warning: objtool: fixup_use_fwh_lock()+0x0: stack state mismatch: cfa1=6+16 cfa2=7+8
  drivers/mtd/chips/cfi_cmdset_0002.o: warning: objtool: do_otp_write()+0xa: unsupported stack pointer realignment
  drivers/mtd/chips/cfi_cmdset_0002.o: warning: objtool: do_otp_write()+0x0: stack state mismatch: cfa1=-4-40 cfa2=7+8

Reported-by: kbuild test robot <fengguang.wu@intel.com>
Signed-off-by: Josh 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/43e7aae9a7a7710cd6df597fa9dc501da4ba0602.1502472193.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Josh Poimboeuf 2017-08-11 12:24:15 -05:00 committed by Ingo Molnar
parent fa2016a8e7
commit ee97638b57
1 changed files with 7 additions and 7 deletions
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14
tools/objtool/check.c
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@ -1536,15 +1536,15 @@ static int validate_branch(struct objtool_file *file, struct instruction *first,
while (1) {
next_insn = next_insn_same_sec(file, insn);
if (file->c_file && insn->func) {
if (func && func != insn->func) {
WARN("%s() falls through to next function %s()",
func->name, insn->func->name);
return 1;
}
if (file->c_file && func && insn->func && func != insn->func) {
WARN("%s() falls through to next function %s()",
func->name, insn->func->name);
return 1;
}
func = insn->func;
if (insn->func)
func = insn->func;
if (func && insn->ignore) {
WARN_FUNC("BUG: why am I validating an ignored function?",