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Support 32 bit and 64 bit decoding with one binary

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It is possible to configure the build process such that decoding of 32
bit and 64 bit instructions can be chosen at runtime using an additional
parameter of the decode function. The header file is now entirely
architecture-independent and no longer required any previous defines.

Decoding x86-64 still requires a 64-bit pointer size.
This commit is contained in:
Alexis Engelke
2019-01-13 11:58:59 +01:00
parent 83ea2f0769
commit ed53b4a54d
9 changed files with 138 additions and 78 deletions
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108
decode.c
View File

@@ -5,14 +5,28 @@
#include <decode.h>
#if defined(ARCH_X86_64) && __SIZEOF_POINTER__ < 8
#error "Decoding x86-64 requires a 64-bit architecture"
#endif
#define LIKELY(x) __builtin_expect((x), 1)
#define UNLIKELY(x) __builtin_expect((x), 0)
#define DECODE_TABLE_DATA
static const uint8_t _decode_table[] = {
#if defined(ARCH_386)
#define DECODE_TABLE_DATA_32
static const uint8_t _decode_table32[] = {
#include <decode-table.inc>
};
#undef DECODE_TABLE_DATA
#undef DECODE_TABLE_DATA_32
#endif
#if defined(ARCH_X86_64)
#define DECODE_TABLE_DATA_64
static const uint8_t _decode_table64[] = {
#include <decode-table.inc>
};
#undef DECODE_TABLE_DATA_64
#endif
#define ENTRY_NONE 0
@@ -52,8 +66,8 @@ static const uint8_t _decode_table[] = {
static
int
decode_prefixes(const uint8_t* buffer, int len, PrefixSet* out_prefixes,
uint8_t* out_vex_operand)
decode_prefixes(const uint8_t* buffer, int len, DecodeMode mode,
PrefixSet* out_prefixes, uint8_t* out_vex_operand)
{
int off = 0;
PrefixSet prefixes = 0;
@@ -102,7 +116,7 @@ decode_prefixes(const uint8_t* buffer, int len, PrefixSet* out_prefixes,
prefixes |= PREFIX_REP;
}
#if defined(ARCH_X86_64)
else if (LIKELY(prefix >= 0x40 && prefix <= 0x4F))
else if (mode == DECODE_64 && LIKELY(prefix >= 0x40 && prefix <= 0x4F))
{
prefixes |= PREFIX_REX;
if (prefix & 0x1)
@@ -134,7 +148,7 @@ decode_prefixes(const uint8_t* buffer, int len, PrefixSet* out_prefixes,
return -1;
}
#if defined(ARCH_386)
if ((buffer[off + 1] & 0xc0) != 0xc0)
if (mode == DECODE_32 && (buffer[off + 1] & 0xc0) != 0xc0)
{
break;
}
@@ -144,15 +158,15 @@ decode_prefixes(const uint8_t* buffer, int len, PrefixSet* out_prefixes,
prefixes |= PREFIX_VEX;
#if defined(ARCH_X86_64)
if ((byte2 & 0x80) == 0)
if (mode == DECODE_64 && (byte2 & 0x80) == 0)
{
prefixes |= PREFIX_REXR;
}
if ((byte2 & 0x40) == 0)
if (mode == DECODE_64 && (byte2 & 0x40) == 0)
{
prefixes |= PREFIX_REXX;
}
if ((byte2 & 0x20) == 0)
if (mode == DECODE_64 && (byte2 & 0x20) == 0)
{
prefixes |= PREFIX_REXB;
}
@@ -172,7 +186,7 @@ decode_prefixes(const uint8_t* buffer, int len, PrefixSet* out_prefixes,
// SDM Vol 2A 2-16 (Dec. 2016)
// - "In 32-bit modes, VEX.W is silently ignored."
// - VEX.W either replaces REX.W, is don't care or is reserved.
if (byte3 & 0x80)
if (mode == DECODE_64 && (byte3 & 0x80))
{
prefixes |= PREFIX_REXW;
}
@@ -198,7 +212,7 @@ decode_prefixes(const uint8_t* buffer, int len, PrefixSet* out_prefixes,
return -1;
}
#if defined(ARCH_386)
if ((buffer[off + 1] & 0xc0) != 0xc0)
if (mode == DECODE_32 && (buffer[off + 1] & 0xc0) != 0xc0)
{
break;
}
@@ -207,7 +221,7 @@ decode_prefixes(const uint8_t* buffer, int len, PrefixSet* out_prefixes,
prefixes |= PREFIX_VEX | PREFIX_ESC_0F;
#if defined(ARCH_X86_64)
if ((byte & 0x80) == 0)
if (mode == DECODE_64 && (byte & 0x80) == 0)
{
prefixes |= PREFIX_REXR;
}
@@ -246,7 +260,7 @@ decode_prefixes(const uint8_t* buffer, int len, PrefixSet* out_prefixes,
static
int
decode_modrm(const uint8_t* buffer, int len, Instr* instr,
decode_modrm(const uint8_t* buffer, int len, DecodeMode mode, Instr* instr,
struct Operand* out_o1, struct Operand* out_o2)
{
int off = 0;
@@ -336,10 +350,11 @@ decode_modrm(const uint8_t* buffer, int len, Instr* instr,
if (mod == 0 && rm == 5)
{
#if defined(ARCH_X86_64)
out_o1->reg = RI_IP;
#else
out_o1->reg = REG_NONE;
if (mode == DECODE_64)
out_o1->reg = RI_IP;
else
#endif
out_o1->reg = REG_NONE;
return off;
}
@@ -402,8 +417,23 @@ struct InstrDesc
#define DESC_IMM_BYTE(desc) (((desc)->immediate >> 7) & 1)
int
decode(const uint8_t* buffer, int len, Instr* instr)
decode(const uint8_t* buffer, int len, DecodeMode mode, Instr* instr)
{
const uint8_t* decode_table = NULL;
// Ensure that we can actually handle the decode request
#if defined(ARCH_386)
if (mode == DECODE_32)
decode_table = _decode_table32;
#endif
#if defined(ARCH_X86_64)
if (mode == DECODE_64)
decode_table = _decode_table64;
#endif
if (decode_table == NULL)
return -2;
int retval;
int off = 0;
uint8_t vex_operand = 0;
@@ -411,27 +441,28 @@ decode(const uint8_t* buffer, int len, Instr* instr)
__builtin_memset(instr->operands, 0, sizeof(instr->operands));
retval = decode_prefixes(buffer + off, len - off, &prefixes, &vex_operand);
retval = decode_prefixes(buffer + off, len - off, mode, &prefixes,
&vex_operand);
if (UNLIKELY(retval < 0 || off + retval >= len))
{
return -1;
}
off += retval;
uint16_t* table = (uint16_t*) _decode_table;
const uint16_t* table = (uint16_t*) decode_table;
uint32_t kind = ENTRY_TABLE256;
if (UNLIKELY(prefixes & PREFIX_ESC_MASK))
{
uint32_t escape = prefixes & PREFIX_ESC_MASK;
table = (uint16_t*) &_decode_table[table[0x0F] & ~7];
table = (uint16_t*) &decode_table[table[0x0F] & ~7];
if (escape == PREFIX_ESC_0F38)
{
table = (uint16_t*) &_decode_table[table[0x38] & ~7];
table = (uint16_t*) &decode_table[table[0x38] & ~7];
}
else if (escape == PREFIX_ESC_0F3A)
{
table = (uint16_t*) &_decode_table[table[0x3A] & ~7];
table = (uint16_t*) &decode_table[table[0x3A] & ~7];
}
}
@@ -497,7 +528,7 @@ decode(const uint8_t* buffer, int len, Instr* instr)
}
kind = entry & ENTRY_MASK;
table = (uint16_t*) &_decode_table[entry & ~7];
table = (uint16_t*) &decode_table[entry & ~7];
} while (LIKELY(off < len));
if (UNLIKELY(kind != ENTRY_INSTR))
@@ -552,7 +583,7 @@ decode(const uint8_t* buffer, int len, Instr* instr)
op_size = 2;
}
#if defined(ARCH_X86_64)
else if (desc->gp_size_def64)
else if (mode == DECODE_64 && desc->gp_size_def64)
{
op_size = 8;
}
@@ -603,7 +634,7 @@ decode(const uint8_t* buffer, int len, Instr* instr)
{
operand2 = &instr->operands[DESC_MODREG_IDX(desc)];
}
retval = decode_modrm(buffer + off, len - off, instr,
retval = decode_modrm(buffer + off, len - off, mode, instr,
operand1, operand2);
if (UNLIKELY(retval < 0))
@@ -649,19 +680,26 @@ decode(const uint8_t* buffer, int len, Instr* instr)
instr->scale = 0;
// TODO: Address size overrides
#if defined(ARCH_386)
if (UNLIKELY(off + 4 > len))
if (mode == DECODE_32)
{
return -1;
if (UNLIKELY(off + 4 > len))
{
return -1;
}
instr->disp = LOAD_LE_4(&buffer[off]);
off += 4;
}
instr->disp = LOAD_LE_4(&buffer[off]);
off += 4;
#else
if (UNLIKELY(off + 8 > len))
#endif
#if defined(ARCH_X86_64)
if (mode == DECODE_64)
{
return -1;
if (UNLIKELY(off + 8 > len))
{
return -1;
}
instr->disp = LOAD_LE_8(&buffer[off]);
off += 8;
}
instr->disp = LOAD_LE_8(&buffer[off]);
off += 8;
#endif
}
else if (UNLIKELY(imm_control != 0))