static void walk_instructions(unsigned char *pos, unsigned char *end,
void (*cb)(unsigned char *pos, unsigned len, void *arg), void *arg)
{
unsigned char *cur = pos;
while (cur < end)
{
/* FIXME: if our mapping includes some non-instructions,
* and these accidentally decode into multi-byte instructions,
* we might get misaligned here. We *will* catch this when
* we do the paranoid second scan, but it would be better not
* to rely on this. */
unsigned len = instr_len(cur, end);
cb(cur, len, arg);
cur += (len ? len : 1);
}
}
static int decode_segreg(struct sigcontext *scp)
{
unsigned cs, eip;
unsigned char *csp, *orig_csp;
int ret = -1;
x86_ins x86;
x86._32bit = dpmi_mhp_get_selector_size(_cs);
cs = GetSegmentBase(_cs);
eip = _eip + x86_handle_prefixes(scp, cs, &x86);
csp = (unsigned char *)MEM_BASE32(cs + eip);
orig_csp = (unsigned char *)MEM_BASE32(cs + _eip);
switch(*csp) {
case 0x8e: /* mov segreg,r/m16 */
ret = sreg_idx(*(unsigned char *)MEM_BASE32(cs + eip + 1) >> 3);
_eip += instr_len(orig_csp, x86._32bit);
break;
case 0xca: /*retf imm 16*/
case 0xcb: /*retf*/
case 0xcf: /*iret*/
{
unsigned tmp_eip = x86_pop(scp, &x86);
x86_pop(scp, &x86);
ret = cs_INDEX;
switch (*(unsigned char *)MEM_BASE32(cs + eip)) {
case 0xca: /*retf imm 16*/
_esp += ((unsigned short *) (MEM_BASE32(cs + eip + 1)))[0];
break;
case 0xcf: /*iret*/
scp->eflags = x86_pop(scp, &x86);
break;
}
_eip = tmp_eip;
}
break;
case 0xea: /* jmp seg:off16/off32 */
{
unsigned tmp_eip;
tmp_eip = x86.operand_size == 4 ? READ_DWORDP(MEM_BASE32(cs + eip + 1)) :
READ_WORDP(MEM_BASE32(cs + eip + 1));
ret = cs_INDEX;
_eip = tmp_eip;
}
break;
case 0xc4: /* les */
ret = es_INDEX;
_eip += instr_len(orig_csp, x86._32bit);
break;
case 0xc5: /* lds */
ret = ds_INDEX;
_eip += instr_len(orig_csp, x86._32bit);
break;
case 0x07: /* pop es */
case 0x17: /* pop ss */
case 0x1f: /* pop ds */
ret = sreg_idx(*(unsigned char *)MEM_BASE32(cs + eip) >> 3);
x86_pop(scp, &x86);
_eip = eip + 1;
break;
case 0x0f:
eip++;
switch (*(unsigned char *)MEM_BASE32(cs + eip)) {
case 0xa1: /* pop fs */
case 0xa9: /* pop gs */
x86_pop(scp, &x86);
ret = sreg_idx(*(unsigned char *)MEM_BASE32(cs + eip) >> 3);
_eip = eip + 1;
break;
case 0xb2: /* lss */
ret = ss_INDEX;
_eip += instr_len(orig_csp, x86._32bit);
break;
case 0xb4: /* lfs */
ret = fs_INDEX;
_eip += instr_len(orig_csp, x86._32bit);
break;
case 0xb5: /* lgs */
ret = gs_INDEX;
_eip += instr_len(orig_csp, x86._32bit);
break;
}
break;
}
return ret;
}
