Commit 607a4029 authored Sep 27, 2017 by Josh Poimboeuf Committed by Ingo Molnar Sep 28, 2017

objtool: Support unoptimized frame pointer setup

Arnd Bergmann reported a bunch of warnings like:

crypto/jitterentropy.o: warning: objtool: jent_fold_time()+0x3b: call without frame pointer save/setup
crypto/jitterentropy.o: warning: objtool: jent_stuck()+0x1d: call without frame pointer save/setup
crypto/jitterentropy.o: warning: objtool: jent_unbiased_bit()+0x15: call without frame pointer save/setup
crypto/jitterentropy.o: warning: objtool: jent_read_entropy()+0x32: call without frame pointer save/setup
crypto/jitterentropy.o: warning: objtool: jent_entropy_collector_free()+0x19: call without frame pointer save/setup

and

arch/x86/events/core.o: warning: objtool: collect_events uses BP as a scratch register
arch/x86/events/core.o: warning: objtool: events_ht_sysfs_show()+0x22: call without frame pointer save/setup

With certain rare configurations, GCC sometimes sets up the frame
pointer with:

lea (%rsp),%rbp

instead of:

mov %rsp,%rbp

The instructions are equivalent, so treat the former like the latter.

Reported-by: Arnd Bergmann <arnd@arndb.de>
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/a468af8b28a69b83fffc6d7668be9b6fcc873699.1506526584.git.jpoimboe@redhat.com

Signed-off-by: Ingo Molnar <mingo@kernel.org>

parent da541b20

tools/objtool/arch/x86/decode.c

+8 −3

Original line number	Diff line number	Diff line
		@@ -284,11 +284,16 @@ int arch_decode_instruction(struct elf elf, struct section sec,
		case 0x8d:
		if (sib == 0x24 && rex_w && !rex_b && !rex_x) {

		/* lea disp(%rsp), reg */
		*type = INSN_STACK;
		if (!insn.displacement.value) {
		/* lea (%rsp), reg */
		op->src.type = OP_SRC_REG;
		} else {
		/* lea disp(%rsp), reg */
		op->src.type = OP_SRC_ADD;
		op->src.reg = CFI_SP;
		op->src.offset = insn.displacement.value;
		}
		op->src.reg = CFI_SP;
		op->dest.type = OP_DEST_REG;
		op->dest.reg = op_to_cfi_reg[modrm_reg][rex_r];