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instrs: Fix decoding of XCHG r8, rax

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Opcode 90 is only a NOP if there is no REX.B.
This commit is contained in:
Alexis Engelke
2020-06-14 13:34:47 +02:00
parent c3df15e19b
commit 80ec7ed960
3 changed files with 21 additions and 1 deletions
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15
decode.c
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@@ -608,6 +608,21 @@ fd_decode(const uint8_t* buffer, size_t len_sz, int mode_int, uintptr_t address,
}
}
if (instr->type == FDI_XCHG_NOP)
{
// Only 4890, 90, and 6690 are true NOPs.
if (instr->operands[0].reg == 0 && instr->operands[1].reg == 0)
{
instr->operands[0].type = FD_OT_NONE;
instr->operands[1].type = FD_OT_NONE;
instr->type = FDI_NOP;
}
else
{
instr->type = FDI_XCHG;
}
}
if ((prefixes & PREFIX_LOCK) && !desc->lock)
return FD_ERR_UD;
if ((prefixes & PREFIX_LOCK) && instr->operands[0].type != FD_OT_MEM)