From fb084fde0c8106bc86df243411751c3421c07c08 Mon Sep 17 00:00:00 2001 From: Julien Thierry Date: Wed, 14 Oct 2020 08:38:00 +0100 Subject: [PATCH] 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: Julien Thierry Acked-by: Peter Zijlstra (Intel) Signed-off-by: Josh Poimboeuf --- tools/objtool/check.c | 15 +++++++++++---- 1 file changed, 11 insertions(+), 4 deletions(-) diff --git a/tools/objtool/check.c b/tools/objtool/check.c index 5f8d3eed78a1..88210b0856f7 100644 --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -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(®s[CFI_BP], -cfa->offset)) { /* mov %rsp, %rbp */ cfa->base = op->dest.reg;