/*
* x86 instruction analysis
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
*
* Copyright (C) IBM Corporation, 2002, 2004, 2009
*/
#include <linux/string.h>
#include <asm/inat.h>
#include <asm/insn.h>
#define get_next(t, insn) \
({t r; r = *(t*)insn->next_byte; insn->next_byte += sizeof(t); r; })
#define peek_next(t, insn) \
({t r; r = *(t*)insn->next_byte; r; })
/**
* insn_init() - initialize struct insn
* @insn: &struct insn to be initialized
* @kaddr: address (in kernel memory) of instruction (or copy thereof)
* @x86_64: !0 for 64-bit kernel or 64-bit app
*/
void insn_init(struct insn *insn, const void *kaddr, int x86_64)
{
memset(insn, 0, sizeof(*insn));
insn->kaddr = kaddr;
insn->next_byte = kaddr;
insn->x86_64 = x86_64 ? 1 : 0;
insn->opnd_bytes = 4;
if (x86_64)
insn->addr_bytes = 8;
else
insn->addr_bytes = 4;
}
/**
* insn_get_prefixes - scan x86 instruction prefix bytes
* @insn: &struct insn containing instruction
*
* Populates the @insn->prefixes bitmap, and updates @insn->next_byte
* to point to the (first) opcode. No effect if @insn->prefixes.got
* is already set.
*/
void insn_get_prefixes(struct insn *insn)
{
struct insn_field *prefixes = &insn->prefixes;
insn_attr_t attr;
insn_byte_t b, lb;
int i, nb;
if (prefixes->got)
return;
nb = 0;
lb = 0;
b = peek_next(insn_byte_t, insn);
attr = inat_get_opcode_attribute(b);
while (inat_is_legacy_prefix(attr)) {
/* Skip if same prefix */
for (i = 0; i < nb; i++)
if (prefixes->bytes[i] == b)
goto found;
if (nb == 4)
/* Invalid instruction */
break;
prefixes->bytes[nb++] = b;
if (inat_is_address_size_prefix(attr)) {
/* address size switches 2/4 or 4/8 */
if (insn->x86_64)
insn->addr_bytes ^= 12;
else
insn->addr_bytes ^= 6;
} else if (inat_is_operand_size_prefix(attr)) {
/* oprand size switches 2/4 */
insn->opnd_bytes ^= 6;
}
found:
prefixes->nbytes++;
insn->next_byte++;
lb = b;
b = peek_next(insn_byte_t, insn);
attr = inat_get_opcode_attribute(b);
}
/* Set the last prefix */
if (lb && lb != insn->prefixes.bytes[3]) {
if (unlikely(insn->prefixes.bytes[3])) {
/* Swap the last prefix */
b = insn->prefixes.bytes[3];
for (i = 0; i < nb; i++)
if (prefixes->bytes[i] == lb)
prefixes->bytes[i] = b;
}
insn->prefixes.bytes[3] = lb;
}
if (insn->x86_64) {
b = peek_next(insn_byte_t, insn);
attr = inat_get_opcode_attribute(b);
if (inat_is_rex_prefix(attr)) {
insn->rex_prefix.value = b;
insn->rex_prefix.nbytes = 1;
insn->next_byte++;
if (X86_REX_W(b))
/* REX.W overrides opnd_size */
insn->opnd_bytes = 8;
}
}
insn->rex_prefix.got = 1;
prefixes->got = 1;
return;
}
/**
* insn_get_opcode - collect opcode(s)
* @insn: &struct insn containing instruction
*
* Populates @insn->opcode, updates @insn->next_byte to point past the
* opcode byte(s), and set @insn->attr (except for groups).
* If necessary, first collects any preceding (prefix) bytes.
* Sets @insn->opcode.value = opcode1. No effect if @insn->opcode.got
* is already 1.
*/
void insn_get_opcode(struct insn *insn)
{
struct insn_field *opcode = &insn->opcode;
insn_byte_t op, pfx;
if (opcode->got)
return;
if (!insn->prefixes.got)
insn_get_prefixes(insn);
/* Get first opcode */
op = get_next(insn_byte_t, insn);
opcode->bytes[0] = op;
opcode->nbytes = 1;
insn->attr = inat_get_opcode_attribute(op);
while (inat_is_escape(insn->attr)) {
/* Get escaped opcode */
op = get_next(insn_byte_t, insn);
opcode->bytes[opcode->nbytes++] = op;
pfx = insn_last_prefix(insn);
insn->attr = inat_get_escape_attribute(op, pfx, insn->attr);
}
opcode->got = 1;
}
/**
* insn_get_modrm - collect ModRM byte, if any
* @insn: &struct insn containing instruction
*
* Populates @insn->modrm and updates @insn->next_byte to point past the
* ModRM byte, if any. If necessary, first collects the preceding bytes
* (prefixes and opcode(s)). No effect if @insn->modrm.got is already 1.
*/
void insn_get_modrm(struct insn *insn)
{
struct insn_field *modrm = &insn->modrm;
insn_byte_t pfx, mod;
if (modrm->got)
return;
if (!insn->opcode.got)
insn_get_opcode(insn);
if (inat_has_modrm(insn->attr)) {
mod = get_next(insn_byte_t, insn);
modrm->value = mod;
modrm->nbytes = 1;
if (inat_is_group(insn->attr)) {
pfx = insn_last_prefix(insn);
insn->attr = inat_get_group_attribute(mod, pfx,
insn->attr);
}
}
if (insn->x86_64 && inat_is_force64(insn->attr))
insn->opnd_bytes = 8;
modrm->got = 1;
}
/**
* insn_rip_relative() - Does instruction use RIP-relative addressing mode?
* @insn: &struct insn containing instruction
*
* If necessary, first collects the instruction up to and including the
* ModRM byte. No effect if @insn->x86_64 is 0.
*/
int insn_rip_relative(struct insn *insn)
{
struct insn_field *modrm = &insn->modrm;
if (!insn->x86_64)
return 0;
if (!modrm->got)
insn_get_modrm(insn);
/*
* For rip-relative instructions, the mod field (top 2 bits)
* is zero and the r/m field (bottom 3 bits) is 0x5.
*/
return (modrm->nbytes && (modrm->value & 0xc7) == 0x5);
}
/**
* insn_get_sib() - Get the SIB byte of instruction
* @insn: &struct insn containing instruction
*
* If necessary, first collects the instruction up to and including the
* ModRM byte.
*/
void insn_get_sib(struct insn *insn)
{
insn_byte_t modrm;
if (insn->sib.got)
return;
if (!insn->modrm.got)
insn_get_modrm(insn);
if (insn->modrm.nbytes) {
modrm = (insn_byte_t)insn->modrm.value;
if (insn->addr_bytes != 2 &&
X86_MODRM_MOD(modrm) != 3 && X86_MODRM_RM(modrm) == 4) {
insn->sib.value = get_next(insn_byte_t, insn);
insn->sib.nbytes = 1;
}
}
insn->sib.got = 1;
}
/**
* insn_get_displacement() - Get the displacement of instruction
* @insn: &struct insn containing instruction
*
* If necessary, first collects the instruction up to and including the
* SIB byte.
* Displacement value is sign-expanded.
*/
void insn_get_displacement(struct insn *insn)
{
insn_byte_t mod, rm, base;
if (insn->displacement.got)
return;
if (!insn->sib.got)
insn_get_sib(insn);
if (insn->modrm.nbytes) {
/*
* Interpreting the modrm byte:
* mod = 00 - no displacement fields (exceptions below)
* mod = 01 - 1-byte displacement field
* mod = 10 - displacement field is 4 bytes, or 2 bytes if
* address size = 2 (0x67 prefix in 32-bit mode)
* mod = 11 - no memory operand
*
* If address size = 2...
* mod = 00, r/m = 110 - displacement field is 2 bytes
*
* If address size != 2...
* mod != 11, r/m = 100 - SIB byte exists
* mod = 00, SIB base = 101 - displacement field is 4 bytes
* mod = 00, r/m = 101 - rip-relative addressing, displacement
* field is 4 bytes
*/
mod = X86_MODRM_MOD(insn->modrm.value);
rm = X86_MODRM_RM(insn->modrm.value);
base = X86_SIB_BASE(insn->sib.value);
if (mod == 3)
goto out;
if (mod == 1) {
insn->displacement.value = get_next(char, insn);
insn->displacement.nbytes = 1;
} else if (insn->addr_bytes == 2) {
if ((mod == 0 && rm == 6) || mod == 2) {
insn->displacement.value =
get_next(short, insn);
insn->displacement.nbytes = 2;
}
} else {
if ((mod == 0 && rm == 5) || mod == 2 ||
(mod == 0 && base == 5)) {
insn->displacement.value = get_next(int, insn);
insn->displacement.nbytes = 4;
}
}
}
out:
insn->displacement.got = 1;
}
/* Decode moffset16/32/64 */
static void __get_moffset(struct insn *insn)
{
switch (insn->addr_bytes) {
case 2:
insn->moffset1.value = get_next(short, insn);
insn->moffset1.nbytes = 2;
break;
case 4:
insn->moffset1.value = get_next(int, insn);
insn->moffset1.nbytes = 4;
break;
case 8:
insn->moffset1.value = get_next(int, insn);
insn->moffset1.nbytes = 4;
insn->moffset2.value = get_next(int, insn);
insn->moffset2.nbytes = 4;
break;
}
insn->moffset1.got = insn->moffset2.got = 1;
}
/* Decode imm v32(Iz) */
static void __get_immv32(struct insn *insn)
{
switch (insn->opnd_bytes) {
case 2:
insn->immediate.value = get_next(short, insn);
insn->immediate.nbytes = 2;
break;
case 4:
case 8:
insn->immediate.value = get_next(int, insn);
insn->immediate.nbytes = 4;
break;
}
}
/* Decode imm v64(Iv/Ov) */
static void __get_immv(struct insn *insn)
{
switch (insn->opnd_bytes) {
case 2:
insn->immediate1.value = get_next(short, insn);
insn->immediate1.nbytes = 2;
break;
case 4:
insn->immediate1.value = get_next(int, insn);
insn->immediate1.nbytes = 4;
break;
case 8:
insn->immediate1.value = get_next(int, insn);
insn->immediate1.nbytes = 4;
insn->immediate2.value = get_next(int, insn);
insn->immediate2.nbytes = 4;
break;
}
insn->immediate1.got = insn->immediate2.got = 1;
}
/* Decode ptr16:16/32(Ap) */
static void __get_immptr(struct insn *insn)
{
switch (insn->opnd_bytes) {
case 2:
insn->immediate1.value = get_next(short, insn);
insn->immediate1.nbytes = 2;
break;
case 4:
insn->immediate1.value = get_next(int, insn);
insn->immediate1.nbytes = 4;
break;
case 8:
/* ptr16:64 is not exist (no segment) */
return;
}
insn->immediate2.value = get_next(unsigned short, insn);
insn->immediate2.nbytes = 2;
insn->immediate1.got = insn->immediate2.got = 1;
}
/**
* insn_get_immediate() - Get the immediates of instruction
* @insn: &struct insn containing instruction
*
* If necessary, first collects the instruction up to and including the
* displacement bytes.
* Basically, most of immediates are sign-expanded. Unsigned-value can be
* get by bit masking with ((1 << (nbytes * 8)) - 1)
*/
void insn_get_immediate(struct insn *insn)
{
if (insn->immediate.got)
return;
if (!insn->displacement.got)
insn_get_displacement(insn);
if (inat_has_moffset(insn->attr)) {
__get_moffset(insn);
goto done;
}
if (!inat_has_immediate(insn->attr))
/* no immediates */
goto done;
switch (inat_immediate_size(insn->attr)) {
case INAT_IMM_BYTE:
insn->immediate.value = get_next(char, insn);
insn->immediate.nbytes = 1;
break;
case INAT_IMM_WORD:
insn->immediate.value = get_next(short, insn);
insn->immediate.nbytes = 2;
break;
case INAT_IMM_DWORD:
insn->immediate.value = get_next(int, insn);
insn->immediate.nbytes = 4;
break;
case INAT_IMM_QWORD:
insn->immediate1.value = get_next(int, insn);
insn->immediate1.nbytes = 4;
insn->immediate2.value = get_next(int, insn);
insn->immediate2.nbytes = 4;
break;
case INAT_IMM_PTR:
__get_immptr(insn);
break;
case INAT_IMM_VWORD32:
__get_immv32(insn);
break;
case INAT_IMM_VWORD:
__get_immv(insn);
break;
default:
break;
}
if (inat_has_second_immediate(insn->attr)) {
insn->immediate2.value = get_next(char, insn);
insn->immediate2.nbytes = 1;
}
done:
insn->immediate.got = 1;
}
/**
* insn_get_length() - Get the length of instruction
* @insn: &struct insn containing instruction
*
* If necessary, first collects the instruction up to and including the
* immediates bytes.
*/
void insn_get_length(struct insn *insn)
{
if (insn->length)
return;
if (!insn->immediate.got)
insn_get_immediate(insn);
insn->length = (unsigned char)((unsigned long)insn->next_byte
- (unsigned long)insn->kaddr);
}
