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SubjectRe: [PATCH v2 2/3] objtool,x86: Additionally decode: mov %rsp, (%reg)
On Tue, Feb 09, 2021 at 10:16:02AM +0100, Peter Zijlstra wrote:
> Where we already decode: mov %rsp, %reg, also decode mov %rsp, (%reg).
>
> Nothing should match for this new stack-op.
>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> ---
> tools/objtool/arch/x86/decode.c | 23 ++++++++++++++++++-----
> 1 file changed, 18 insertions(+), 5 deletions(-)
>
> --- a/tools/objtool/arch/x86/decode.c
> +++ b/tools/objtool/arch/x86/decode.c
> @@ -222,14 +222,24 @@ int arch_decode_instruction(const struct
> break;
>
> case 0x89:
> - if (rex_w && !rex_r && modrm_mod == 3 && modrm_reg == 4) {
> + if (rex_w && !rex_r && modrm_reg == 4) {
>
> - /* mov %rsp, reg */
> + /* mov %rsp, */
> ADD_OP(op) {
> op->src.type = OP_SRC_REG;
> op->src.reg = CFI_SP;
> - op->dest.type = OP_DEST_REG;
> - op->dest.reg = op_to_cfi_reg[modrm_rm][rex_b];
> + if (modrm_mod == 3) {
> +
> + /* mov %rsp, reg */
> + op->dest.type = OP_DEST_REG;
> + op->dest.reg = op_to_cfi_reg[modrm_rm][rex_b];
> +
> + } else if (modrm_mod == 0) {
> +
> + /* mov %rsp, (%reg) */
> + op->dest.type = OP_DEST_REG_INDIRECT;
> + op->dest.reg = op_to_cfi_reg[modrm_rm][rex_b];
> + }

What if modrm_mod is 1 or 2? Should 'if' below the 'case' make sure
it's 0 or 3?

> }
> break;
> }
> @@ -259,8 +269,10 @@ int arch_decode_instruction(const struct
> op->dest.reg = CFI_BP;
> op->dest.offset = insn.displacement.value;
> }
> + break;
> + }
>
> - } else if (rex_w && !rex_b && modrm_rm == 4 && sib == 0x24) {
> + if (rex_w && !rex_b && modrm_rm == 4 && sib == 0x24) {
>
> /* mov reg, disp(%rsp) */
> ADD_OP(op) {
> @@ -270,6 +282,7 @@ int arch_decode_instruction(const struct
> op->dest.reg = CFI_SP;
> op->dest.offset = insn.displacement.value;
> }
> + break;
> }
>
> break;
>

Did this change have a point?

--
Josh

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