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decode: Remove TABLE_PREFIX_REP and use NFx prefix

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This commit is contained in:
Alexis Engelke
2020-11-08 10:03:18 +01:00
parent 69ce124354
commit 2e7e396325
4 changed files with 102 additions and 72 deletions
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21
decode.c
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@@ -34,7 +34,6 @@ typedef enum DecodeMode DecodeMode;
#define ENTRY_TABLE72 4
#define ENTRY_TABLE_PREFIX 5
#define ENTRY_TABLE_VEX 6
#define ENTRY_TABLE_PREFIX_REP 7
#define ENTRY_TABLE_ROOT 8
#define ENTRY_MASK 7
@@ -326,6 +325,7 @@ struct InstrDesc
#define DESC_SIZE_FIX1(desc) (((desc)->operand_sizes >> 10) & 7)
#define DESC_SIZE_FIX2(desc) (((desc)->operand_sizes >> 13) & 3)
#define DESC_INSTR_WIDTH(desc) (((desc)->operand_sizes >> 15) & 1)
#define DESC_IGN66(desc) (((desc)->reg_types >> 15) & 1)
int
fd_decode(const uint8_t* buffer, size_t len_sz, int mode_int, uintptr_t address,
@@ -409,18 +409,12 @@ fd_decode(const uint8_t* buffer, size_t len_sz, int mode_int, uintptr_t address,
if (kind == ENTRY_TABLE_PREFIX)
{
// If a prefix is mandatory and used as opcode extension, it has no
// further effect on the instruction. This is especially important
// for the 0x66 prefix, which could otherwise override the operand
// size of general purpose registers.
prefixes &= ~(PREFIX_OPSZ | PREFIX_REPNZ | PREFIX_REP);
ENTRY_UNPACK(table, kind, table[mandatory_prefix]);
}
else if (kind == ENTRY_TABLE_PREFIX_REP)
{
// Discard 66h mandatory prefix
uint8_t index = mandatory_prefix != 1 ? mandatory_prefix : 0;
// further effect on the instruction. This, however, does not completely
// apply to the 66 prefix: in rare cases it may affect the size of
// general purpose registers. The instruction descriptor encodes whether
// the 66 prefix has an effect on the instruction (IGN66).
prefixes &= ~(PREFIX_REPNZ | PREFIX_REP);
ENTRY_UNPACK(table, kind, table[index]);
ENTRY_UNPACK(table, kind, table[mandatory_prefix]);
}
// For VEX prefix, we have to distinguish between VEX.W and VEX.L which may
@@ -438,6 +432,9 @@ fd_decode(const uint8_t* buffer, size_t len_sz, int mode_int, uintptr_t address,
struct InstrDesc* desc = (struct InstrDesc*) table;
if (DESC_IGN66(desc))
prefixes &= ~PREFIX_OPSZ;
instr->type = desc->type;
instr->flags = prefixes & 0x7f;
if (mode == DECODE_64)