Commit ee97638b authored Aug 11, 2017 by Josh Poimboeuf Committed by Ingo Molnar Aug 21, 2017

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>

parent fa2016a8

tools/objtool/check.c

+7 −7

Original line number	Diff line number	Diff line
		@@ -1536,14 +1536,14 @@ 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) {

		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;
		}
		}

		if (insn->func)
		func = insn->func;

		if (func && insn->ignore) {

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