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decode: Unify VEX opcode escape extraction

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This commit is contained in:
Alexis Engelke
2023-04-23 08:54:36 +02:00
parent 239be46d4a
commit 247acd6221
1 changed files with 2 additions and 3 deletions
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5
decode.c
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@@ -245,18 +245,17 @@ fd_decode(const uint8_t* buffer, size_t len_sz, int mode_int, uintptr_t address,
{
if (byte & 0x08) // Bit 3 of opcode_escape must be clear.
return FD_ERR_UD;
opcode_escape = (byte & 0x07);
_Static_assert(PREFIX_REXRR == 0x10, "wrong REXRR value");
if (mode == DECODE_64)
prefix_rex |= (byte & PREFIX_REXRR) ^ PREFIX_REXRR;
}
else // 3-byte VEX
{
if (byte & 0x1c) // Bits 4:2 of opcode_escape must be clear.
if (byte & 0x18) // Bits 4:3 of opcode_escape must be clear.
return FD_ERR_UD;
opcode_escape = (byte & 0x03); // 4 is table index with VEX
}
opcode_escape = (byte & 0x07);
if (UNLIKELY(opcode_escape == 0)) {
int prefix_len = vex_prefix == 0x62 ? 4 : 3;
// Pretend to decode the prefix plus one opcode byte.