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Be more restrictive with VSIB encodings

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This commit is contained in:
Alexis Engelke
2019-11-10 15:02:27 +01:00
parent e63fa88da4
commit e73dbb3eea
1 changed files with 9 additions and 1 deletions
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10
decode.c
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@@ -196,7 +196,7 @@ decode_modrm(const uint8_t* buffer, int len, DecodeMode mode, FdInstr* instr,
if (UNLIKELY(off >= len)) if (UNLIKELY(off >= len))
{ {
return -1; return FD_ERR_PARTIAL;
} }
uint8_t modrm = buffer[off++]; uint8_t modrm = buffer[off++];
@@ -204,6 +204,10 @@ decode_modrm(const uint8_t* buffer, int len, DecodeMode mode, FdInstr* instr,
uint8_t mod_reg = (modrm & 0x38) >> 3; uint8_t mod_reg = (modrm & 0x38) >> 3;
uint8_t rm = modrm & 0x07; uint8_t rm = modrm & 0x07;
// VSIB must have a memory operand with SIB byte.
if (vsib && (rm != 4 || mod == 3))
return FD_ERR_UD;
// Operand 2 may be NULL when reg field is used as opcode extension // Operand 2 may be NULL when reg field is used as opcode extension
if (out_o2) if (out_o2)
{ {
@@ -499,6 +503,10 @@ fd_decode(const uint8_t* buffer, size_t len_sz, int mode_int, uintptr_t address,
{ {
FdOp* operand = &instr->operands[DESC_VEXREG_IDX(desc)]; FdOp* operand = &instr->operands[DESC_VEXREG_IDX(desc)];
operand->type = FD_OT_REG; operand->type = FD_OT_REG;
#if defined(ARCH_386)
if (mode == DECODE_32)
vex_operand &= 0x7;
#endif
operand->reg = vex_operand; operand->reg = vex_operand;
} }
else if (vex_operand != 0) else if (vex_operand != 0)