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nasm/disasm.c
Cyrill Gorcunov 0a45cc8ce8 disasm.c: eatbyte -- use snprintf to prevent potential buffer overflow 
At moment we can't overrun buffer even if we would like to
but better to stay on a safe side and use snprintf.

Signed-off-by: Cyrill Gorcunov <gorcunov@gmail.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
2009-08-09 10:30:48 -07:00

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/* ----------------------------------------------------------------------- *
*
* Copyright 1996-2009 The NASM Authors - All Rights Reserved
* See the file AUTHORS included with the NASM distribution for
* the specific copyright holders.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following
* conditions are met:
*
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above
* copyright notice, this list of conditions and the following
* disclaimer in the documentation and/or other materials provided
* with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
* CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
* INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
* OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
* EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
* ----------------------------------------------------------------------- */
/*
* disasm.c where all the _work_ gets done in the Netwide Disassembler
*/
#include "compiler.h"
#include <stdio.h>
#include <string.h>
#include <limits.h>
#include <inttypes.h>
#include "nasm.h"
#include "disasm.h"
#include "sync.h"
#include "insns.h"
#include "tables.h"
#include "regdis.h"
/*
* Flags that go into the `segment' field of `insn' structures
* during disassembly.
*/
#define SEG_RELATIVE 1
#define SEG_32BIT 2
#define SEG_RMREG 4
#define SEG_DISP8 8
#define SEG_DISP16 16
#define SEG_DISP32 32
#define SEG_NODISP 64
#define SEG_SIGNED 128
#define SEG_64BIT 256
/*
* Prefix information
*/
struct prefix_info {
uint8_t osize; /* Operand size */
uint8_t asize; /* Address size */
uint8_t osp; /* Operand size prefix present */
uint8_t asp; /* Address size prefix present */
uint8_t rep; /* Rep prefix present */
uint8_t seg; /* Segment override prefix present */
uint8_t wait; /* WAIT "prefix" present */
uint8_t lock; /* Lock prefix present */
uint8_t vex[3]; /* VEX prefix present */
uint8_t vex_c; /* VEX "class" (VEX, XOP, ...) */
uint8_t vex_m; /* VEX.M field */
uint8_t vex_v;
uint8_t vex_lp; /* VEX.LP fields */
uint32_t rex; /* REX prefix present */
};
#define getu8(x) (*(uint8_t *)(x))
#if X86_MEMORY
/* Littleendian CPU which can handle unaligned references */
#define getu16(x) (*(uint16_t *)(x))
#define getu32(x) (*(uint32_t *)(x))
#define getu64(x) (*(uint64_t *)(x))
#else
static uint16_t getu16(uint8_t *data)
{
return (uint16_t)data[0] + ((uint16_t)data[1] << 8);
}
static uint32_t getu32(uint8_t *data)
{
return (uint32_t)getu16(data) + ((uint32_t)getu16(data+2) << 16);
}
static uint64_t getu64(uint8_t *data)
{
return (uint64_t)getu32(data) + ((uint64_t)getu32(data+4) << 32);
}
#endif
#define gets8(x) ((int8_t)getu8(x))
#define gets16(x) ((int16_t)getu16(x))
#define gets32(x) ((int32_t)getu32(x))
#define gets64(x) ((int64_t)getu64(x))
/* Important: regval must already have been adjusted for rex extensions */
static enum reg_enum whichreg(int32_t regflags, int regval, int rex)
{
if (!(regflags & (REGISTER|REGMEM)))
return 0; /* Registers not permissible?! */
regflags |= REGISTER;
if (!(REG_AL & ~regflags))
return R_AL;
if (!(REG_AX & ~regflags))
return R_AX;
if (!(REG_EAX & ~regflags))
return R_EAX;
if (!(REG_RAX & ~regflags))
return R_RAX;
if (!(REG_DL & ~regflags))
return R_DL;
if (!(REG_DX & ~regflags))
return R_DX;
if (!(REG_EDX & ~regflags))
return R_EDX;
if (!(REG_RDX & ~regflags))
return R_RDX;
if (!(REG_CL & ~regflags))
return R_CL;
if (!(REG_CX & ~regflags))
return R_CX;
if (!(REG_ECX & ~regflags))
return R_ECX;
if (!(REG_RCX & ~regflags))
return R_RCX;
if (!(FPU0 & ~regflags))
return R_ST0;
if (!(XMM0 & ~regflags))
return R_XMM0;
if (!(YMM0 & ~regflags))
return R_YMM0;
if (!(REG_CS & ~regflags))
return (regval == 1) ? R_CS : 0;
if (!(REG_DESS & ~regflags))
return (regval == 0 || regval == 2
|| regval == 3 ? nasm_rd_sreg[regval] : 0);
if (!(REG_FSGS & ~regflags))
return (regval == 4 || regval == 5 ? nasm_rd_sreg[regval] : 0);
if (!(REG_SEG67 & ~regflags))
return (regval == 6 || regval == 7 ? nasm_rd_sreg[regval] : 0);
/* All the entries below look up regval in an 16-entry array */
if (regval < 0 || regval > 15)
return 0;
if (!(REG8 & ~regflags)) {
if (rex & (REX_P|REX_NH))
return nasm_rd_reg8_rex[regval];
else
return nasm_rd_reg8[regval];
}
if (!(REG16 & ~regflags))
return nasm_rd_reg16[regval];
if (!(REG32 & ~regflags))
return nasm_rd_reg32[regval];
if (!(REG64 & ~regflags))
return nasm_rd_reg64[regval];
if (!(REG_SREG & ~regflags))
return nasm_rd_sreg[regval & 7]; /* Ignore REX */
if (!(REG_CREG & ~regflags))
return nasm_rd_creg[regval];
if (!(REG_DREG & ~regflags))
return nasm_rd_dreg[regval];
if (!(REG_TREG & ~regflags)) {
if (regval > 7)
return 0; /* TR registers are ill-defined with rex */
return nasm_rd_treg[regval];
}
if (!(FPUREG & ~regflags))
return nasm_rd_fpureg[regval & 7]; /* Ignore REX */
if (!(MMXREG & ~regflags))
return nasm_rd_mmxreg[regval & 7]; /* Ignore REX */
if (!(XMMREG & ~regflags))
return nasm_rd_xmmreg[regval];
if (!(YMMREG & ~regflags))
return nasm_rd_ymmreg[regval];
return 0;
}
/*
* Process a DREX suffix
*/
static uint8_t *do_drex(uint8_t *data, insn *ins)
{
uint8_t drex = *data++;
operand *dst = &ins->oprs[ins->drexdst];
if ((drex & 8) != ((ins->rex & REX_OC) ? 8 : 0))
return NULL; /* OC0 mismatch */
ins->rex = (ins->rex & ~7) | (drex & 7);
dst->segment = SEG_RMREG;
dst->basereg = drex >> 4;
return data;
}
/*
* Process an effective address (ModRM) specification.
*/
static uint8_t *do_ea(uint8_t *data, int modrm, int asize,
int segsize, operand * op, insn *ins)
{
int mod, rm, scale, index, base;
int rex;
uint8_t sib = 0;
mod = (modrm >> 6) & 03;
rm = modrm & 07;
if (mod != 3 && rm == 4 && asize != 16)
sib = *data++;
if (ins->rex & REX_D) {
data = do_drex(data, ins);
if (!data)
return NULL;
}
rex = ins->rex;
if (mod == 3) { /* pure register version */
op->basereg = rm+(rex & REX_B ? 8 : 0);
op->segment |= SEG_RMREG;
return data;
}
op->disp_size = 0;
op->eaflags = 0;
if (asize == 16) {
/*
* <mod> specifies the displacement size (none, byte or
* word), and <rm> specifies the register combination.
* Exception: mod=0,rm=6 does not specify [BP] as one might
* expect, but instead specifies [disp16].
*/
op->indexreg = op->basereg = -1;
op->scale = 1; /* always, in 16 bits */
switch (rm) {
case 0:
op->basereg = R_BX;
op->indexreg = R_SI;
break;
case 1:
op->basereg = R_BX;
op->indexreg = R_DI;
break;
case 2:
op->basereg = R_BP;
op->indexreg = R_SI;
break;
case 3:
op->basereg = R_BP;
op->indexreg = R_DI;
break;
case 4:
op->basereg = R_SI;
break;
case 5:
op->basereg = R_DI;
break;
case 6:
op->basereg = R_BP;
break;
case 7:
op->basereg = R_BX;
break;
}
if (rm == 6 && mod == 0) { /* special case */
op->basereg = -1;
if (segsize != 16)
op->disp_size = 16;
mod = 2; /* fake disp16 */
}
switch (mod) {
case 0:
op->segment |= SEG_NODISP;
break;
case 1:
op->segment |= SEG_DISP8;
op->offset = (int8_t)*data++;
break;
case 2:
op->segment |= SEG_DISP16;
op->offset = *data++;
op->offset |= ((unsigned)*data++) << 8;
break;
}
return data;
} else {
/*
* Once again, <mod> specifies displacement size (this time
* none, byte or *dword*), while <rm> specifies the base
* register. Again, [EBP] is missing, replaced by a pure
* disp32 (this time that's mod=0,rm=*5*) in 32-bit mode,
* and RIP-relative addressing in 64-bit mode.
*
* However, rm=4
* indicates not a single base register, but instead the
* presence of a SIB byte...
*/
int a64 = asize == 64;
op->indexreg = -1;
if (a64)
op->basereg = nasm_rd_reg64[rm | ((rex & REX_B) ? 8 : 0)];
else
op->basereg = nasm_rd_reg32[rm | ((rex & REX_B) ? 8 : 0)];
if (rm == 5 && mod == 0) {
if (segsize == 64) {
op->eaflags |= EAF_REL;
op->segment |= SEG_RELATIVE;
mod = 2; /* fake disp32 */
}
if (asize != 64)
op->disp_size = asize;
op->basereg = -1;
mod = 2; /* fake disp32 */
}
if (rm == 4) { /* process SIB */
scale = (sib >> 6) & 03;
index = (sib >> 3) & 07;
base = sib & 07;
op->scale = 1 << scale;
if (index == 4 && !(rex & REX_X))
op->indexreg = -1; /* ESP/RSP cannot be an index */
else if (a64)
op->indexreg = nasm_rd_reg64[index | ((rex & REX_X) ? 8 : 0)];
else
op->indexreg = nasm_rd_reg32[index | ((rex & REX_X) ? 8 : 0)];
if (base == 5 && mod == 0) {
op->basereg = -1;
mod = 2; /* Fake disp32 */
} else if (a64)
op->basereg = nasm_rd_reg64[base | ((rex & REX_B) ? 8 : 0)];
else
op->basereg = nasm_rd_reg32[base | ((rex & REX_B) ? 8 : 0)];
if (segsize == 16)
op->disp_size = 32;
}
switch (mod) {
case 0:
op->segment |= SEG_NODISP;
break;
case 1:
op->segment |= SEG_DISP8;
op->offset = gets8(data);
data++;
break;
case 2:
op->segment |= SEG_DISP32;
op->offset = gets32(data);
data += 4;
break;
}
return data;
}
}
/*
* Determine whether the instruction template in t corresponds to the data
* stream in data. Return the number of bytes matched if so.
*/
#define case4(x) case (x): case (x)+1: case (x)+2: case (x)+3
static int matches(const struct itemplate *t, uint8_t *data,
const struct prefix_info *prefix, int segsize, insn *ins)
{
uint8_t *r = (uint8_t *)(t->code);
uint8_t *origdata = data;
bool a_used = false, o_used = false;
enum prefixes drep = 0;
enum prefixes dwait = 0;
uint8_t lock = prefix->lock;
int osize = prefix->osize;
int asize = prefix->asize;
int i, c;
int op1, op2;
struct operand *opx, *opy;
uint8_t opex = 0;
int s_field_for = -1; /* No 144/154 series code encountered */
bool vex_ok = false;
int regmask = (segsize == 64) ? 15 : 7;
for (i = 0; i < MAX_OPERANDS; i++) {
ins->oprs[i].segment = ins->oprs[i].disp_size =
(segsize == 64 ? SEG_64BIT : segsize == 32 ? SEG_32BIT : 0);
}
ins->condition = -1;
ins->rex = prefix->rex;
memset(ins->prefixes, 0, sizeof ins->prefixes);
if (t->flags & (segsize == 64 ? IF_NOLONG : IF_LONG))
return false;
if (prefix->rep == 0xF2)
drep = P_REPNE;
else if (prefix->rep == 0xF3)
drep = P_REP;
dwait = prefix->wait ? P_WAIT : 0;
while ((c = *r++) != 0) {
op1 = (c & 3) + ((opex & 1) << 2);
op2 = ((c >> 3) & 3) + ((opex & 2) << 1);
opx = &ins->oprs[op1];
opy = &ins->oprs[op2];
opex = 0;
switch (c) {
case 01:
case 02:
case 03:
case 04:
while (c--)
if (*r++ != *data++)
return false;
break;
case 05:
case 06:
case 07:
opex = c;
break;
case4(010):
{
int t = *r++, d = *data++;
if (d < t || d > t + 7)
return false;
else {
opx->basereg = (d-t)+
(ins->rex & REX_B ? 8 : 0);
opx->segment |= SEG_RMREG;
}
break;
}
case4(014):
case4(0274):
opx->offset = (int8_t)*data++;
opx->segment |= SEG_SIGNED;
break;
case4(020):
opx->offset = *data++;
break;
case4(024):
opx->offset = *data++;
break;
case4(030):
opx->offset = getu16(data);
data += 2;
break;
case4(034):
if (osize == 32) {
opx->offset = getu32(data);
data += 4;
} else {
opx->offset = getu16(data);
data += 2;
}
if (segsize != asize)
opx->disp_size = asize;
break;
case4(040):
case4(0254):
opx->offset = getu32(data);
data += 4;
break;
case4(044):
switch (asize) {
case 16:
opx->offset = getu16(data);
data += 2;
if (segsize != 16)
opx->disp_size = 16;
break;
case 32:
opx->offset = getu32(data);
data += 4;
if (segsize == 16)
opx->disp_size = 32;
break;
case 64:
opx->offset = getu64(data);
opx->disp_size = 64;
data += 8;
break;
}
break;
case4(050):
opx->offset = gets8(data++);
opx->segment |= SEG_RELATIVE;
break;
case4(054):
opx->offset = getu64(data);
data += 8;
break;
case4(060):
opx->offset = gets16(data);
data += 2;
opx->segment |= SEG_RELATIVE;
opx->segment &= ~SEG_32BIT;
break;
case4(064):
opx->segment |= SEG_RELATIVE;
if (osize == 16) {
opx->offset = gets16(data);
data += 2;
opx->segment &= ~(SEG_32BIT|SEG_64BIT);
} else if (osize == 32) {
opx->offset = gets32(data);
data += 4;
opx->segment &= ~SEG_64BIT;
opx->segment |= SEG_32BIT;
}
if (segsize != osize) {
opx->type =
(opx->type & ~SIZE_MASK)
| ((osize == 16) ? BITS16 : BITS32);
}
break;
case4(070):
opx->offset = gets32(data);
data += 4;
opx->segment |= SEG_32BIT | SEG_RELATIVE;
break;
case4(0100):
case4(0110):
case4(0120):
case4(0130):
{
int modrm = *data++;
opx->segment |= SEG_RMREG;
data = do_ea(data, modrm, asize, segsize, opy, ins);
if (!data)
return false;
opx->basereg = ((modrm >> 3) & 7) + (ins->rex & REX_R ? 8 : 0);
break;
}
case4(0140):
if (s_field_for == op1) {
opx->offset = gets8(data);
data++;
} else {
opx->offset = getu16(data);
data += 2;
}
break;
case4(0144):
case4(0154):
s_field_for = (*data & 0x02) ? op1 : -1;
if ((*data++ & ~0x02) != *r++)
return false;
break;
case4(0150):
if (s_field_for == op1) {
opx->offset = gets8(data);
data++;
} else {
opx->offset = getu32(data);
data += 4;
}
break;
case4(0160):
ins->rex |= REX_D;
ins->drexdst = op1;
break;
case4(0164):
ins->rex |= REX_D|REX_OC;
ins->drexdst = op1;
break;
case 0171:
data = do_drex(data, ins);
if (!data)
return false;
break;
case 0172:
{
uint8_t ximm = *data++;
c = *r++;
ins->oprs[c >> 3].basereg = (ximm >> 4) & regmask;
ins->oprs[c >> 3].segment |= SEG_RMREG;
ins->oprs[c & 7].offset = ximm & 15;
}
break;
case 0173:
{
uint8_t ximm = *data++;
c = *r++;
if ((c ^ ximm) & 15)
return false;
ins->oprs[c >> 4].basereg = (ximm >> 4) & regmask;
ins->oprs[c >> 4].segment |= SEG_RMREG;
}
break;
case 0174:
{
uint8_t ximm = *data++;
c = *r++;
ins->oprs[c].basereg = (ximm >> 4) & regmask;
ins->oprs[c].segment |= SEG_RMREG;
}
break;
case4(0200):
case4(0204):
case4(0210):
case4(0214):
case4(0220):
case4(0224):
case4(0230):
case4(0234):
{
int modrm = *data++;
if (((modrm >> 3) & 07) != (c & 07))
return false; /* spare field doesn't match up */
data = do_ea(data, modrm, asize, segsize, opy, ins);
if (!data)
return false;
break;
}
case4(0260):
{
int vexm = *r++;
int vexwlp = *r++;
ins->rex |= REX_V;
if ((prefix->rex & (REX_V|REX_D|REX_P)) != REX_V)
return false;
if ((vexm & 0x1f) != prefix->vex_m)
return false;
switch (vexwlp & 030) {
case 000:
if (prefix->rex & REX_W)
return false;
break;
case 010:
if (!(prefix->rex & REX_W))
return false;
ins->rex &= ~REX_W;
break;
case 020: /* VEX.W is a don't care */
ins->rex &= ~REX_W;
break;
case 030:
break;
}
if ((vexwlp & 007) != prefix->vex_lp)
return false;
opx->segment |= SEG_RMREG;
opx->basereg = prefix->vex_v;
vex_ok = true;
break;
}
case 0270:
{
int vexm = *r++;
int vexwlp = *r++;
ins->rex |= REX_V;
if ((prefix->rex & (REX_V|REX_D|REX_P)) != REX_V)
return false;
if ((vexm & 0x1f) != prefix->vex_m)
return false;
switch (vexwlp & 030) {
case 000:
if (ins->rex & REX_W)
return false;
break;
case 010:
if (!(ins->rex & REX_W))
return false;
break;
default:
break; /* Need to do anything special here? */
}
if ((vexwlp & 007) != prefix->vex_lp)
return false;
if (prefix->vex_v != 0)
return false;
vex_ok = true;
break;
}
case 0310:
if (asize != 16)
return false;
else
a_used = true;
break;
case 0311:
if (asize != 32)
return false;
else
a_used = true;
break;
case 0312:
if (asize != segsize)
return false;
else
a_used = true;
break;
case 0313:
if (asize != 64)
return false;
else
a_used = true;
break;
case 0314:
if (prefix->rex & REX_B)
return false;
break;
case 0315:
if (prefix->rex & REX_X)
return false;
break;
case 0316:
if (prefix->rex & REX_R)
return false;
break;
case 0317:
if (prefix->rex & REX_W)
return false;
break;
case 0320:
if (osize != 16)
return false;
else
o_used = true;
break;
case 0321:
if (osize != 32)
return false;
else
o_used = true;
break;
case 0322:
if (osize != (segsize == 16) ? 16 : 32)
return false;
else
o_used = true;
break;
case 0323:
ins->rex |= REX_W; /* 64-bit only instruction */
osize = 64;
o_used = true;
break;
case 0324:
if (!(ins->rex & (REX_P|REX_W)) || osize != 64)
return false;
o_used = true;
break;
case 0325:
ins->rex |= REX_NH;
break;
case 0330:
{
int t = *r++, d = *data++;
if (d < t || d > t + 15)
return false;
else
ins->condition = d - t;
break;
}
case 0331:
if (prefix->rep)
return false;
break;
case 0332:
if (prefix->rep != 0xF2)
return false;
drep = 0;
break;
case 0333:
if (prefix->rep != 0xF3)
return false;
drep = 0;
break;
case 0334:
if (lock) {
ins->rex |= REX_R;
lock = 0;
}
break;
case 0335:
if (drep == P_REP)
drep = P_REPE;
break;
case 0336:
case 0337:
break;
case 0340:
return false;
case 0341:
if (prefix->wait != 0x9B)
return false;
dwait = 0;
break;
case4(0344):
ins->oprs[0].basereg = (*data++ >> 3) & 7;
break;
case 0360:
if (prefix->osp || prefix->rep)
return false;
break;
case 0361:
if (!prefix->osp || prefix->rep)
return false;
o_used = true;
break;
case 0362:
if (prefix->osp || prefix->rep != 0xf2)
return false;
drep = 0;
break;
case 0363:
if (prefix->osp || prefix->rep != 0xf3)
return false;
drep = 0;
break;
case 0364:
if (prefix->osp)
return false;
break;
case 0365:
if (prefix->asp)
return false;
break;
case 0366:
if (!prefix->osp)
return false;
o_used = true;
break;
case 0367:
if (!prefix->asp)
return false;
a_used = true;
break;
default:
return false; /* Unknown code */
}
}
if (!vex_ok && (ins->rex & REX_V))
return false;
/* REX cannot be combined with DREX or VEX */
if ((ins->rex & (REX_D|REX_V)) && (prefix->rex & REX_P))
return false;
/*
* Check for unused rep or a/o prefixes.
*/
for (i = 0; i < t->operands; i++) {
if (ins->oprs[i].segment != SEG_RMREG)
a_used = true;
}
if (lock) {
if (ins->prefixes[PPS_LREP])
return false;
ins->prefixes[PPS_LREP] = P_LOCK;
}
if (drep) {
if (ins->prefixes[PPS_LREP])
return false;
ins->prefixes[PPS_LREP] = drep;
}
ins->prefixes[PPS_WAIT] = dwait;
if (!o_used) {
if (osize != ((segsize == 16) ? 16 : 32)) {
enum prefixes pfx = 0;
switch (osize) {
case 16:
pfx = P_O16;
break;
case 32:
pfx = P_O32;
break;
case 64:
pfx = P_O64;
break;
}
if (ins->prefixes[PPS_OSIZE])
return false;
ins->prefixes[PPS_OSIZE] = pfx;
}
}
if (!a_used && asize != segsize) {
if (ins->prefixes[PPS_ASIZE])
return false;
ins->prefixes[PPS_ASIZE] = asize == 16 ? P_A16 : P_A32;
}
/* Fix: check for redundant REX prefixes */
return data - origdata;
}
/* Condition names for disassembly, sorted by x86 code */
static const char * const condition_name[16] = {
"o", "no", "c", "nc", "z", "nz", "na", "a",
"s", "ns", "pe", "po", "l", "nl", "ng", "g"
};
int32_t disasm(uint8_t *data, char *output, int outbufsize, int segsize,
int32_t offset, int autosync, uint32_t prefer)
{
const struct itemplate * const *p, * const *best_p;
const struct disasm_index *ix;
uint8_t *dp;
int length, best_length = 0;
char *segover;
int i, slen, colon, n;
uint8_t *origdata;
int works;
insn tmp_ins, ins;
uint32_t goodness, best;
int best_pref;
struct prefix_info prefix;
bool end_prefix;
memset(&ins, 0, sizeof ins);
/*
* Scan for prefixes.
*/
memset(&prefix, 0, sizeof prefix);
prefix.asize = segsize;
prefix.osize = (segsize == 64) ? 32 : segsize;
segover = NULL;
origdata = data;
ix = itable;
end_prefix = false;
while (!end_prefix) {
switch (*data) {
case 0xF2:
case 0xF3:
prefix.rep = *data++;
break;
case 0x9B:
prefix.wait = *data++;
break;
case 0xF0:
prefix.lock = *data++;
break;
case 0x2E:
segover = "cs", prefix.seg = *data++;
break;
case 0x36:
segover = "ss", prefix.seg = *data++;
break;
case 0x3E:
segover = "ds", prefix.seg = *data++;
break;
case 0x26:
segover = "es", prefix.seg = *data++;
break;
case 0x64:
segover = "fs", prefix.seg = *data++;
break;
case 0x65:
segover = "gs", prefix.seg = *data++;
break;
case 0x66:
prefix.osize = (segsize == 16) ? 32 : 16;
prefix.osp = *data++;
break;
case 0x67:
prefix.asize = (segsize == 32) ? 16 : 32;
prefix.asp = *data++;
break;
case 0xC4:
case 0xC5:
if (segsize == 64 || (data[1] & 0xc0) == 0xc0) {
prefix.vex[0] = *data++;
prefix.vex[1] = *data++;
prefix.rex = REX_V;
prefix.vex_c = RV_VEX;
if (prefix.vex[0] == 0xc4) {
prefix.vex[2] = *data++;
prefix.rex |= (~prefix.vex[1] >> 5) & 7; /* REX_RXB */
prefix.rex |= (prefix.vex[2] >> (7-3)) & REX_W;
prefix.vex_m = prefix.vex[1] & 0x1f;
prefix.vex_v = (~prefix.vex[2] >> 3) & 15;
prefix.vex_lp = prefix.vex[2] & 7;
} else {
prefix.rex |= (~prefix.vex[1] >> (7-2)) & REX_R;
prefix.vex_m = 1;
prefix.vex_v = (~prefix.vex[1] >> 3) & 15;
prefix.vex_lp = prefix.vex[1] & 7;
}
ix = itable_vex[RV_VEX][prefix.vex_m][prefix.vex_lp];
}
end_prefix = true;
break;
case 0x8F:
if ((data[1] & 030) != 0 &&
(segsize == 64 || (data[1] & 0xc0) == 0xc0)) {
prefix.vex[0] = *data++;
prefix.vex[1] = *data++;
prefix.vex[2] = *data++;
prefix.rex = REX_V;
prefix.vex_c = RV_XOP;
prefix.rex |= (~prefix.vex[1] >> 5) & 7; /* REX_RXB */
prefix.rex |= (prefix.vex[2] >> (7-3)) & REX_W;
prefix.vex_m = prefix.vex[1] & 0x1f;
prefix.vex_v = (~prefix.vex[2] >> 3) & 15;
prefix.vex_lp = prefix.vex[2] & 7;
ix = itable_vex[RV_XOP][prefix.vex_m][prefix.vex_lp];
}
end_prefix = true;
break;
case REX_P + 0x0:
case REX_P + 0x1:
case REX_P + 0x2:
case REX_P + 0x3:
case REX_P + 0x4:
case REX_P + 0x5:
case REX_P + 0x6:
case REX_P + 0x7:
case REX_P + 0x8:
case REX_P + 0x9:
case REX_P + 0xA:
case REX_P + 0xB:
case REX_P + 0xC:
case REX_P + 0xD:
case REX_P + 0xE:
case REX_P + 0xF:
if (segsize == 64) {
prefix.rex = *data++;
if (prefix.rex & REX_W)
prefix.osize = 64;
}
end_prefix = true;
break;
default:
end_prefix = true;
break;
}
}
best = -1; /* Worst possible */
best_p = NULL;
best_pref = INT_MAX;
if (!ix)
return 0; /* No instruction table at all... */
dp = data;
ix += *dp++;
while (ix->n == -1) {
ix = (const struct disasm_index *)ix->p + *dp++;
}
p = (const struct itemplate * const *)ix->p;
for (n = ix->n; n; n--, p++) {
if ((length = matches(*p, data, &prefix, segsize, &tmp_ins))) {
works = true;
/*
* Final check to make sure the types of r/m match up.
* XXX: Need to make sure this is actually correct.
*/
for (i = 0; i < (*p)->operands; i++) {
if (!((*p)->opd[i] & SAME_AS) &&
(
/* If it's a mem-only EA but we have a
register, die. */
((tmp_ins.oprs[i].segment & SEG_RMREG) &&
!(MEMORY & ~(*p)->opd[i])) ||
/* If it's a reg-only EA but we have a memory
ref, die. */
(!(tmp_ins.oprs[i].segment & SEG_RMREG) &&
!(REG_EA & ~(*p)->opd[i]) &&
!((*p)->opd[i] & REG_SMASK)) ||
/* Register type mismatch (eg FS vs REG_DESS):
die. */
((((*p)->opd[i] & (REGISTER | FPUREG)) ||
(tmp_ins.oprs[i].segment & SEG_RMREG)) &&
!whichreg((*p)->opd[i],
tmp_ins.oprs[i].basereg, tmp_ins.rex))
)) {
works = false;
break;
}
}
/*
* Note: we always prefer instructions which incorporate
* prefixes in the instructions themselves. This is to allow
* e.g. PAUSE to be preferred to REP NOP, and deal with
* MMX/SSE instructions where prefixes are used to select
* between MMX and SSE register sets or outright opcode
* selection.
*/
if (works) {
int i, nprefix;
goodness = ((*p)->flags & IF_PFMASK) ^ prefer;
nprefix = 0;
for (i = 0; i < MAXPREFIX; i++)
if (tmp_ins.prefixes[i])
nprefix++;
if (nprefix < best_pref ||
(nprefix == best_pref && goodness < best)) {
/* This is the best one found so far */
best = goodness;
best_p = p;
best_pref = nprefix;
best_length = length;
ins = tmp_ins;
}
}
}
}
if (!best_p)
return 0; /* no instruction was matched */
/* Pick the best match */
p = best_p;
length = best_length;
slen = 0;
/* TODO: snprintf returns the value that the string would have if
* the buffer were long enough, and not the actual length of
* the returned string, so each instance of using the return
* value of snprintf should actually be checked to assure that
* the return value is "sane." Maybe a macro wrapper could
* be used for that purpose.
*/
for (i = 0; i < MAXPREFIX; i++) {
const char *prefix = prefix_name(ins.prefixes[i]);
if (prefix)
slen += snprintf(output+slen, outbufsize-slen, "%s ", prefix);
}
i = (*p)->opcode;
if (i >= FIRST_COND_OPCODE)
slen += snprintf(output + slen, outbufsize - slen, "%s%s",
nasm_insn_names[i], condition_name[ins.condition]);
else
slen += snprintf(output + slen, outbufsize - slen, "%s",
nasm_insn_names[i]);
colon = false;
length += data - origdata; /* fix up for prefixes */
for (i = 0; i < (*p)->operands; i++) {
opflags_t t = (*p)->opd[i];
const operand *o = &ins.oprs[i];
int64_t offs;
if (t & SAME_AS) {
o = &ins.oprs[t & ~SAME_AS];
t = (*p)->opd[t & ~SAME_AS];
}
output[slen++] = (colon ? ':' : i == 0 ? ' ' : ',');
offs = o->offset;
if (o->segment & SEG_RELATIVE) {
offs += offset + length;
/*
* sort out wraparound
*/
if (!(o->segment & (SEG_32BIT|SEG_64BIT)))
offs &= 0xffff;
else if (segsize != 64)
offs &= 0xffffffff;
/*
* add sync marker, if autosync is on
*/
if (autosync)
add_sync(offs, 0L);
}
if (t & COLON)
colon = true;
else
colon = false;
if ((t & (REGISTER | FPUREG)) ||
(o->segment & SEG_RMREG)) {
enum reg_enum reg;
reg = whichreg(t, o->basereg, ins.rex);
if (t & TO)
slen += snprintf(output + slen, outbufsize - slen, "to ");
slen += snprintf(output + slen, outbufsize - slen, "%s",
nasm_reg_names[reg-EXPR_REG_START]);
} else if (!(UNITY & ~t)) {
output[slen++] = '1';
} else if (t & IMMEDIATE) {
if (t & BITS8) {
slen +=
snprintf(output + slen, outbufsize - slen, "byte ");
if (o->segment & SEG_SIGNED) {
if (offs < 0) {
offs *= -1;
output[slen++] = '-';
} else
output[slen++] = '+';
}
} else if (t & BITS16) {
slen +=
snprintf(output + slen, outbufsize - slen, "word ");
} else if (t & BITS32) {
slen +=
snprintf(output + slen, outbufsize - slen, "dword ");
} else if (t & BITS64) {
slen +=
snprintf(output + slen, outbufsize - slen, "qword ");
} else if (t & NEAR) {
slen +=
snprintf(output + slen, outbufsize - slen, "near ");
} else if (t & SHORT) {
slen +=
snprintf(output + slen, outbufsize - slen, "short ");
}
slen +=
snprintf(output + slen, outbufsize - slen, "0x%"PRIx64"",
offs);
} else if (!(MEM_OFFS & ~t)) {
slen +=
snprintf(output + slen, outbufsize - slen,
"[%s%s%s0x%"PRIx64"]",
(segover ? segover : ""),
(segover ? ":" : ""),
(o->disp_size == 64 ? "qword " :
o->disp_size == 32 ? "dword " :
o->disp_size == 16 ? "word " : ""), offs);
segover = NULL;
} else if (!(REGMEM & ~t)) {
int started = false;
if (t & BITS8)
slen +=
snprintf(output + slen, outbufsize - slen, "byte ");
if (t & BITS16)
slen +=
snprintf(output + slen, outbufsize - slen, "word ");
if (t & BITS32)
slen +=
snprintf(output + slen, outbufsize - slen, "dword ");
if (t & BITS64)
slen +=
snprintf(output + slen, outbufsize - slen, "qword ");
if (t & BITS80)
slen +=
snprintf(output + slen, outbufsize - slen, "tword ");
if (t & BITS128)
slen +=
snprintf(output + slen, outbufsize - slen, "oword ");
if (t & BITS256)
slen +=
snprintf(output + slen, outbufsize - slen, "yword ");
if (t & FAR)
slen += snprintf(output + slen, outbufsize - slen, "far ");
if (t & NEAR)
slen +=
snprintf(output + slen, outbufsize - slen, "near ");
output[slen++] = '[';
if (o->disp_size)
slen += snprintf(output + slen, outbufsize - slen, "%s",
(o->disp_size == 64 ? "qword " :
o->disp_size == 32 ? "dword " :
o->disp_size == 16 ? "word " :
""));
if (o->eaflags & EAF_REL)
slen += snprintf(output + slen, outbufsize - slen, "rel ");
if (segover) {
slen +=
snprintf(output + slen, outbufsize - slen, "%s:",
segover);
segover = NULL;
}
if (o->basereg != -1) {
slen += snprintf(output + slen, outbufsize - slen, "%s",
nasm_reg_names[(o->basereg-EXPR_REG_START)]);
started = true;
}
if (o->indexreg != -1) {
if (started)
output[slen++] = '+';
slen += snprintf(output + slen, outbufsize - slen, "%s",
nasm_reg_names[(o->indexreg-EXPR_REG_START)]);
if (o->scale > 1)
slen +=
snprintf(output + slen, outbufsize - slen, "*%d",
o->scale);
started = true;
}
if (o->segment & SEG_DISP8) {
const char *prefix;
uint8_t offset = offs;
if ((int8_t)offset < 0) {
prefix = "-";
offset = -offset;
} else {
prefix = "+";
}
slen +=
snprintf(output + slen, outbufsize - slen, "%s0x%"PRIx8"",
prefix, offset);
} else if (o->segment & SEG_DISP16) {
const char *prefix;
uint16_t offset = offs;
if ((int16_t)offset < 0 && started) {
offset = -offset;
prefix = "-";
} else {
prefix = started ? "+" : "";
}
slen +=
snprintf(output + slen, outbufsize - slen,
"%s0x%"PRIx16"", prefix, offset);
} else if (o->segment & SEG_DISP32) {
if (prefix.asize == 64) {
const char *prefix;
uint64_t offset = (int64_t)(int32_t)offs;
if ((int32_t)offs < 0 && started) {
offset = -offset;
prefix = "-";
} else {
prefix = started ? "+" : "";
}
slen +=
snprintf(output + slen, outbufsize - slen,
"%s0x%"PRIx64"", prefix, offset);
} else {
const char *prefix;
uint32_t offset = offs;
if ((int32_t) offset < 0 && started) {
offset = -offset;
prefix = "-";
} else {
prefix = started ? "+" : "";
}
slen +=
snprintf(output + slen, outbufsize - slen,
"%s0x%"PRIx32"", prefix, offset);
}
}
output[slen++] = ']';
} else {
slen +=
snprintf(output + slen, outbufsize - slen, "<operand%d>",
i);
}
}
output[slen] = '\0';
if (segover) { /* unused segment override */
char *p = output;
int count = slen + 1;
while (count--)
p[count + 3] = p[count];
strncpy(output, segover, 2);
output[2] = ' ';
}
return length;
}
/*
* This is called when we don't have a complete instruction. If it
* is a standalone *single-byte* prefix show it as such, otherwise
* print it as a literal.
*/
int32_t eatbyte(uint8_t *data, char *output, int outbufsize, int segsize)
{
uint8_t byte = *data;
const char *str = NULL;
switch (byte) {
case 0xF2:
str = "repne";
break;
case 0xF3:
str = "rep";
break;
case 0x9B:
str = "wait";
break;
case 0xF0:
str = "lock";
break;
case 0x2E:
str = "cs";
break;
case 0x36:
str = "ss";
break;
case 0x3E:
str = "ss";
break;
case 0x26:
str = "es";
break;
case 0x64:
str = "fs";
break;
case 0x65:
str = "gs";
break;
case 0x66:
str = (segsize == 16) ? "o32" : "o16";
break;
case 0x67:
str = (segsize == 32) ? "a16" : "a32";
break;
case REX_P + 0x0:
case REX_P + 0x1:
case REX_P + 0x2:
case REX_P + 0x3:
case REX_P + 0x4:
case REX_P + 0x5:
case REX_P + 0x6:
case REX_P + 0x7:
case REX_P + 0x8:
case REX_P + 0x9:
case REX_P + 0xA:
case REX_P + 0xB:
case REX_P + 0xC:
case REX_P + 0xD:
case REX_P + 0xE:
case REX_P + 0xF:
if (segsize == 64) {
snprintf(output, outbufsize, "rex%s%s%s%s%s",
(byte == REX_P) ? "" : ".",
(byte & REX_W) ? "w" : "",
(byte & REX_R) ? "r" : "",
(byte & REX_X) ? "x" : "",
(byte & REX_B) ? "b" : "");
break;
}
/* else fall through */
default:
snprintf(output, outbufsize, "db 0x%02x", byte);
break;
}
if (str)
snprintf(output, outbufsize, "%s", str);
return 1;
}
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