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objtool,x86: More ModRM sugar
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Better helpers to decode ModRM.

Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Signed-off-by: Ingo Molnar <[email protected]>
Acked-by: Josh Poimboeuf <[email protected]>
Link: https://lkml.kernel.org/r/YCZB/[email protected]
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Peter Zijlstra authored and Ingo Molnar committed Mar 6, 2021
1 parent 961d83b commit 36d92e4
Showing 1 changed file with 17 additions and 11 deletions.
28 changes: 17 additions & 11 deletions tools/objtool/arch/x86/decode.c
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Original file line number Diff line number Diff line change
Expand Up @@ -82,15 +82,21 @@ unsigned long arch_jump_destination(struct instruction *insn)
* 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,
Expand Down Expand Up @@ -154,7 +160,7 @@ int arch_decode_instruction(const struct elf *elf, const struct section *sec,

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) {
Expand Down Expand Up @@ -219,7 +225,7 @@ int arch_decode_instruction(const struct elf *elf, const struct section *sec,
break;

/* %rsp target only */
if (!(modrm_mod == 3 && modrm_rm == CFI_SP))
if (!rm_is_reg(CFI_SP))
break;

imm = insn.immediate.value;
Expand Down Expand Up @@ -272,7 +278,7 @@ int arch_decode_instruction(const struct elf *elf, const struct section *sec,

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;
Expand Down Expand Up @@ -308,7 +314,7 @@ int arch_decode_instruction(const struct elf *elf, const struct section *sec,
break;
}

if (modrm_mod == 3 && modrm_rm == CFI_SP) {
if (rm_is_reg(CFI_SP)) {

/* mov reg, %rsp */
ADD_OP(op) {
Expand All @@ -325,7 +331,7 @@ int arch_decode_instruction(const struct elf *elf, const struct section *sec,
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) {
Expand All @@ -338,7 +344,7 @@ int arch_decode_instruction(const struct elf *elf, const struct section *sec,
break;
}

if (modrm_mod != 3 && rm_is(CFI_SP)) {
if (rm_is_mem(CFI_SP)) {

/* mov reg, disp(%rsp) */
ADD_OP(op) {
Expand All @@ -357,7 +363,7 @@ int arch_decode_instruction(const struct elf *elf, const struct section *sec,
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) {
Expand All @@ -370,7 +376,7 @@ int arch_decode_instruction(const struct elf *elf, const struct section *sec,
break;
}

if (modrm_mod != 3 && rm_is(CFI_SP)) {
if (rm_is_mem(CFI_SP)) {

/* mov disp(%rsp), reg */
ADD_OP(op) {
Expand All @@ -386,7 +392,7 @@ int arch_decode_instruction(const struct elf *elf, const struct section *sec,
break;

case 0x8d:
if (modrm_mod == 3) {
if (mod_is_reg()) {
WARN("invalid LEA encoding at %s:0x%lx", sec->name, offset);
break;
}
Expand Down

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