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objtool,x86: Rewrite LEA decode

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Current LEA decoding is a bunch of special cases, properly decode the
instruction, with exception of full SIB and RIP-relative modes.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Tested-by: Nick Desaulniers <ndesaulniers@google.com>
Link: https://lkml.kernel.org/r/20210211173627.143250641@infradead.org
This commit is contained in:
Peter Zijlstra 2021-02-09 21:29:16 +01:00 • committed by Ingo Molnar
parent d473b18b2e
commit 2ee0c36349
1 changed files with 33 additions and 63 deletions
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96
tools/objtool/arch/x86/decode.c
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@ -91,9 +91,10 @@ int arch_decode_instruction(const struct elf *elf, const struct section *sec,
{
struct insn insn;
int x86_64, sign;
unsigned char op1, op2, rex = 0, rex_b = 0, rex_r = 0, rex_w = 0,
rex_x = 0, modrm = 0, modrm_mod = 0, modrm_rm = 0,
modrm_reg = 0, sib = 0;
unsigned char op1, op2,
rex = 0, rex_b = 0, rex_r = 0, rex_w = 0, rex_x = 0,
modrm = 0, modrm_mod = 0, modrm_rm = 0, modrm_reg = 0,
sib = 0;
struct stack_op *op = NULL;
struct symbol *sym;
@ -328,68 +329,37 @@ int arch_decode_instruction(const struct elf *elf, const struct section *sec,
break;
case 0x8d:
if (sib == 0x24 && rex_w && !rex_b && !rex_x) {
ADD_OP(op) {
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.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];
}
} else if (rex == 0x48 && modrm == 0x65) {
/* lea disp(%rbp), %rsp */
ADD_OP(op) {
op->src.type = OP_SRC_ADD;
op->src.reg = CFI_BP;
op->src.offset = insn.displacement.value;
op->dest.type = OP_DEST_REG;
op->dest.reg = CFI_SP;
}
} else if (rex == 0x49 && modrm == 0x62 &&
insn.displacement.value == -8) {
/*
* lea -0x8(%r10), %rsp
*
* Restoring rsp back to its original value after a
* stack realignment.
*/
ADD_OP(op) {
op->src.type = OP_SRC_ADD;
op->src.reg = CFI_R10;
op->src.offset = -8;
op->dest.type = OP_DEST_REG;
op->dest.reg = CFI_SP;
}
} else if (rex == 0x49 && modrm == 0x65 &&
insn.displacement.value == -16) {
/*
* lea -0x10(%r13), %rsp
*
* Restoring rsp back to its original value after a
* stack realignment.
*/
ADD_OP(op) {
op->src.type = OP_SRC_ADD;
op->src.reg = CFI_R13;
op->src.offset = -16;
op->dest.type = OP_DEST_REG;
op->dest.reg = CFI_SP;
}
if (modrm_mod == 3) {
WARN("invalid LEA encoding at %s:0x%lx", sec->name, offset);
break;
}
/* skip non 64bit ops */
if (!rex_w)
break;
/* skip nontrivial SIB */
if (modrm_rm == 4 && !(sib == 0x24 && rex_b == rex_x))
break;
/* skip RIP relative displacement */
if (modrm_rm == 5 && modrm_mod == 0)
break;
/* lea disp(%src), %dst */
ADD_OP(op) {
op->src.offset = insn.displacement.value;
if (!op->src.offset) {
/* lea (%src), %dst */
op->src.type = OP_SRC_REG;
} else {
/* lea disp(%src), %dst */
op->src.type = OP_SRC_ADD;
}
op->src.reg = op_to_cfi_reg[modrm_rm][rex_b];
op->dest.type = OP_DEST_REG;
op->dest.reg = op_to_cfi_reg[modrm_reg][rex_r];
}
break;
case 0x8f: