Commit fb084fde authored by Julien Thierry's avatar Julien Thierry Committed by Josh Poimboeuf
Browse files

objtool: Fully validate the stack frame 



A valid stack frame should contain both the return address and the
previous frame pointer value.

On x86, the return value is placed on the stack by the calling
instructions. On other architectures, the callee needs to explicitly
save the return address on the stack.

Add the necessary checks to verify a function properly sets up all the
elements of the stack frame.

Signed-off-by: default avatarJulien Thierry <jthierry@redhat.com>
Acked-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: default avatarJosh Poimboeuf <jpoimboe@redhat.com>
parent 7c53f6b6

tools/objtool/check.c

+11 −4
Original line number Diff line number Diff line
@@ -1733,12 +1733,20 @@ static bool has_modified_stack_frame(struct instruction *insn, struct insn_state 
	return false;

}



static bool check_reg_frame_pos(const struct cfi_reg *reg,

				int expected_offset)

{

	return reg->base == CFI_CFA &&

	       reg->offset == expected_offset;

}



static bool has_valid_stack_frame(struct insn_state *state)

{

	struct cfi_state *cfi = &state->cfi;



	if (cfi->cfa.base == CFI_BP && cfi->regs[CFI_BP].base == CFI_CFA &&

	    cfi->regs[CFI_BP].offset == -16)

	if (cfi->cfa.base == CFI_BP &&

	    check_reg_frame_pos(&cfi->regs[CFI_BP], -cfi->cfa.offset) &&

	    check_reg_frame_pos(&cfi->regs[CFI_RA], -cfi->cfa.offset + 8))

		return true;



	if (cfi->drap && cfi->regs[CFI_BP].base == CFI_BP)
@@ -1867,8 +1875,7 @@ static int update_cfi_state(struct instruction *insn, struct cfi_state *cfi, 
		case OP_SRC_REG:

			if (op->src.reg == CFI_SP && op->dest.reg == CFI_BP &&

			    cfa->base == CFI_SP &&

			    regs[CFI_BP].base == CFI_CFA &&

			    regs[CFI_BP].offset == -cfa->offset) {

			    check_reg_frame_pos(&regs[CFI_BP], -cfa->offset)) {



				/* mov %rsp, %rbp */

				cfa->base = op->dest.reg;