I promise, I'll stop poking at it more :-)
---
Subject: objtool,x86: More ModRM sugar
From: Peter Zijlstra <pet...@infradead.org>
Date: Fri Feb 12 09:13:00 CET 2021
Better helpers to decode ModRM.
Signed-off-by: Peter Zijlstra (Intel) <pet...@infradead.org>
---
tools/objtool/arch/x86/decode.c | 28 +++++++++++++++++-----------
1 file changed, 17 insertions(+), 11 deletions(-)
--- a/tools/objtool/arch/x86/decode.c
+++ b/tools/objtool/arch/x86/decode.c
@@ -82,15 +82,21 @@ unsigned long arch_jump_destination(stru
* 01 | [r/m + d8] |[S+d]| [r/m + d8] |
* 10 | [r/m + d32] |[S+D]| [r/m + d32] |
* 11 | r/ m |
- *
*/
+
+#define mod_is_mem() (modrm_mod != 3)
+#define mod_is_reg() (modrm_mod == 3)
+
#define is_RIP() ((modrm_rm & 7) == CFI_BP && modrm_mod == 0)
-#define have_SIB() ((modrm_rm & 7) == CFI_SP && modrm_mod != 3)
+#define have_SIB() ((modrm_rm & 7) == CFI_SP && mod_is_mem())
#define rm_is(reg) (have_SIB() ? \
sib_base == (reg) && sib_index == CFI_SP : \
modrm_rm == (reg))
+#define rm_is_mem(reg) (mod_is_mem() && !is_RIP() && rm_is(reg))
+#define rm_is_reg(reg) (mod_is_reg() && modrm_rm == (reg))
+
int arch_decode_instruction(const struct elf *elf, const struct section *sec,
unsigned long offset, unsigned int maxlen,
unsigned int *len, enum insn_type *type,
@@ -154,7 +160,7 @@ int arch_decode_instruction(const struct
case 0x1:
case 0x29:
- if (rex_w && modrm_mod == 3 && modrm_rm == CFI_SP) {
+ if (rex_w && rm_is_reg(CFI_SP)) {
/* add/sub reg, %rsp */
ADD_OP(op) {
@@ -219,7 +225,7 @@ int arch_decode_instruction(const struct
break;
/* %rsp target only */
- if (!(modrm_mod == 3 && modrm_rm == CFI_SP))
+ if (!rm_is_reg(CFI_SP))
break;
imm = insn.immediate.value;
@@ -272,7 +278,7 @@ int arch_decode_instruction(const struct
if (modrm_reg == CFI_SP) {
- if (modrm_mod == 3) {
+ if (mod_is_reg()) {
/* mov %rsp, reg */
ADD_OP(op) {
op->src.type = OP_SRC_REG;
@@ -308,7 +314,7 @@ int arch_decode_instruction(const struct
break;
}
- if (modrm_mod == 3 && modrm_rm == CFI_SP) {
+ if (rm_is_reg(CFI_SP)) {
/* mov reg, %rsp */
ADD_OP(op) {
@@ -325,7 +331,7 @@ int arch_decode_instruction(const struct
if (!rex_w)
break;
- if ((modrm_mod == 1 || modrm_mod == 2) && modrm_rm == CFI_BP) {
+ if (rm_is_mem(CFI_BP)) {
/* mov reg, disp(%rbp) */
ADD_OP(op) {
@@ -338,7 +344,7 @@ int arch_decode_instruction(const struct
break;
}
- if (modrm_mod != 3 && rm_is(CFI_SP)) {
+ if (rm_is_mem(CFI_SP)) {
/* mov reg, disp(%rsp) */
ADD_OP(op) {
@@ -357,7 +363,7 @@ int arch_decode_instruction(const struct
if (!rex_w)
break;
- if ((modrm_mod == 1 || modrm_mod == 2) && modrm_rm == CFI_BP) {
+ if (rm_is_mem(CFI_BP)) {
/* mov disp(%rbp), reg */
ADD_OP(op) {
@@ -370,7 +376,7 @@ int arch_decode_instruction(const struct
break;
}
- if (modrm_mod != 3 && rm_is(CFI_SP)) {
+ if (rm_is_mem(CFI_SP)) {
/* mov disp(%rsp), reg */
ADD_OP(op) {
@@ -386,7 +392,7 @@ int arch_decode_instruction(const struct
break;
case 0x8d:
- if (modrm_mod == 3) {
+ if (mod_is_reg()) {
WARN("invalid LEA encoding at %s:0x%lx", sec->name,
offset);
break;
}
