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decode: Replace table walk macro with function

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This commit is contained in:
Alexis Engelke
2020-11-17 10:43:08 +01:00
parent 95070908d0
commit 318fdc50eb
1 changed files with 21 additions and 29 deletions
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50
decode.c
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@@ -37,11 +37,12 @@ typedef enum DecodeMode DecodeMode;
#define ENTRY_TABLE_ROOT 8
#define ENTRY_MASK 7
#define ENTRY_UNPACK(table,kind,entry) do { \
uint16_t entry_copy = entry; \
table = &_decode_table[(entry_copy & ~7) >> 1]; \
kind = entry_copy & ENTRY_MASK; \
} while (0)
static inline unsigned
table_walk(unsigned cur_idx, unsigned entry_idx, unsigned* out_kind) {
unsigned entry = _decode_table[cur_idx + entry_idx];
*out_kind = entry & ENTRY_MASK;
return (entry & ~ENTRY_MASK) >> 1;
}
#define LOAD_LE_1(buf) ((size_t) *(uint8_t*) (buf))
#define LOAD_LE_2(buf) (LOAD_LE_1(buf) | LOAD_LE_1((uint8_t*) (buf) + 1)<<8)
@@ -332,30 +333,23 @@ int
fd_decode(const uint8_t* buffer, size_t len_sz, int mode_int, uintptr_t address,
FdInstr* instr)
{
const uint16_t* table = NULL;
DecodeMode mode;
int len = len_sz > 15 ? 15 : len_sz;
// Ensure that we can actually handle the decode request
if (mode_int == 32)
DecodeMode mode;
unsigned table_idx;
unsigned kind = ENTRY_TABLE_ROOT;
switch (mode_int)
{
#if defined(ARCH_386)
table = &_decode_table[FD_TABLE_OFFSET_32];
mode = DECODE_32;
case 32: table_idx = FD_TABLE_OFFSET_32; mode = DECODE_32; break;
#endif
}
else if (mode_int == 64)
{
#if defined(ARCH_X86_64)
table = &_decode_table[FD_TABLE_OFFSET_64];
mode = DECODE_64;
case 64: table_idx = FD_TABLE_OFFSET_64; mode = DECODE_64; break;
#endif
default: return FD_ERR_INTERNAL;
}
if (UNLIKELY(table == NULL))
return FD_ERR_INTERNAL;
int retval;
int off = 0;
uint8_t vex_operand = 0;
@@ -372,8 +366,6 @@ fd_decode(const uint8_t* buffer, size_t len_sz, int mode_int, uintptr_t address,
return FD_ERR_PARTIAL;
off += retval;
uint32_t kind = ENTRY_TABLE_ROOT;
if (UNLIKELY(prefixes & PREFIX_VEX))
{
if (opcode_escape < 0 || opcode_escape > 3)
@@ -393,9 +385,9 @@ fd_decode(const uint8_t* buffer, size_t len_sz, int mode_int, uintptr_t address,
off += opcode_escape >= 2 ? 2 : 1;
}
ENTRY_UNPACK(table, kind, table[opcode_escape]);
table_idx = table_walk(table_idx, opcode_escape, &kind);
if (LIKELY(off < len))
ENTRY_UNPACK(table, kind, table[buffer[off++]]);
table_idx = table_walk(table_idx, buffer[off++], &kind);
// Handle mandatory prefixes (which behave like an opcode ext.).
if (kind == ENTRY_TABLE_PREFIX)
@@ -406,16 +398,16 @@ fd_decode(const uint8_t* buffer, size_t len_sz, int mode_int, uintptr_t address,
// 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[mandatory_prefix]);
table_idx = table_walk(table_idx, mandatory_prefix, &kind);
}
// Then, walk through ModR/M-encoded opcode extensions.
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]);
table_idx = table_walk(table_idx, ((buffer[off] >> 3) & 7) | isreg, &kind);
if (kind == ENTRY_TABLE8E)
table_idx = table_walk(table_idx, buffer[off++] & 7, &kind);
}
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.
@@ -424,13 +416,13 @@ fd_decode(const uint8_t* buffer, size_t len_sz, int mode_int, uintptr_t address,
uint8_t index = 0;
index |= prefixes & PREFIX_REXW ? (1 << 0) : 0;
index |= prefixes & PREFIX_VEXL ? (1 << 1) : 0;
ENTRY_UNPACK(table, kind, table[index]);
table_idx = table_walk(table_idx, index, &kind);
}
if (UNLIKELY(kind != ENTRY_INSTR))
return kind == 0 ? FD_ERR_UD : FD_ERR_PARTIAL;
struct InstrDesc* desc = (struct InstrDesc*) table;
struct InstrDesc* desc = (struct InstrDesc*) &_decode_table[table_idx];
if (DESC_IGN66(desc))
prefixes &= ~PREFIX_OPSZ;