ART: Fix x86 disassembler
Index 4 in SIB is valid when given Rex.x, where it denotes r12 and
not the invalid rsp.
Bug: 19149560
Change-Id: I1a74bcbb1ccf3686e45a3df5d852a86444f9d850
diff --git a/disassembler/disassembler_x86.cc b/disassembler/disassembler_x86.cc
index 1a768c8..203488d 100644
--- a/disassembler/disassembler_x86.cc
+++ b/disassembler/disassembler_x86.cc
@@ -119,12 +119,6 @@
DumpAddrReg(os, rex, reg_num);
}
-static void DumpIndexReg(std::ostream& os, uint8_t rex, uint8_t reg) {
- bool rex_x = (rex & REX_X) != 0;
- uint8_t reg_num = rex_x ? (reg + 8) : reg;
- DumpAddrReg(os, rex, reg_num);
-}
-
static void DumpOpcodeReg(std::ostream& os, uint8_t rex, uint8_t reg,
bool byte_operand, uint8_t size_override) {
bool rex_b = (rex & REX_B) != 0;
@@ -184,18 +178,30 @@
uint8_t index = (sib >> 3) & 7;
uint8_t base = sib & 7;
address << "[";
+
+ // REX.x is bit 3 of index.
+ if ((rex64 & REX_X) != 0) {
+ index += 8;
+ }
+
+ // Mod = 0 && base = 5 (ebp): no base (ignores REX.b).
+ bool has_base = false;
if (base != 5 || mod != 0) {
+ has_base = true;
DumpBaseReg(address, rex64, base);
- if (index != 4) {
+ }
+
+ // Index = 4 (esp/rsp) is disallowed.
+ if (index != 4) {
+ if (has_base) {
address << " + ";
}
- }
- if (index != 4) {
- DumpIndexReg(address, rex64, index);
+ DumpAddrReg(address, rex64, index);
if (scale != 0) {
address << StringPrintf(" * %d", 1 << scale);
}
}
+
if (mod == 0) {
if (base == 5) {
if (index != 4) {