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decode: Replace T8+T72 with T16+T8E for R/M value

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This commit is contained in:
Alexis Engelke
2020-11-08 11:20:03 +01:00
parent 7d7e72746e
commit 9df6ac1788
2 changed files with 27 additions and 18 deletions
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15
decode.c
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@@ -30,8 +30,8 @@ typedef enum DecodeMode DecodeMode;
#define ENTRY_NONE 0
#define ENTRY_INSTR 1
#define ENTRY_TABLE256 2
#define ENTRY_TABLE8 3
#define ENTRY_TABLE72 4
#define ENTRY_TABLE16 3
#define ENTRY_TABLE8E 4
#define ENTRY_TABLE_PREFIX 5
#define ENTRY_TABLE_VEX 6
#define ENTRY_TABLE_ROOT 8
@@ -409,13 +409,12 @@ fd_decode(const uint8_t* buffer, size_t len_sz, int mode_int, uintptr_t address,
}
// Then, walk through ModR/M-encoded opcode extensions.
if ((kind == ENTRY_TABLE8 || kind == ENTRY_TABLE72) && LIKELY(off < len))
{
if (kind == ENTRY_TABLE72 && (buffer[off] & 0xc0) == 0xc0)
ENTRY_UNPACK(table, kind, table[buffer[off++] - 0xb8]);
else
ENTRY_UNPACK(table, kind, table[(buffer[off] >> 3) & 7]);
if (kind == ENTRY_TABLE16 && LIKELY(off < len)) {
unsigned isreg = (buffer[off] & 0xc0) == 0xc0 ? 8 : 0;
ENTRY_UNPACK(table, kind, table[((buffer[off] >> 3) & 7) | isreg]);
}
if (kind == ENTRY_TABLE8E && LIKELY(off < len))
ENTRY_UNPACK(table, kind, table[buffer[off++] & 7]);
// For VEX prefix, we have to distinguish between VEX.W and VEX.L which may
// be part of the opcode.