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popnhax/libdisasm/ia32_invariant.c

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#include <stdlib.h>
#include <string.h>
#include "ia32_invariant.h"
#include "ia32_insn.h"
#include "ia32_settings.h"
extern ia32_table_desc_t *ia32_tables;
extern ia32_settings_t ia32_settings;
extern size_t ia32_table_lookup( unsigned char *buf, size_t buf_len,
unsigned int table, ia32_insn_t **raw_insn,
unsigned int *prefixes );
/* -------------------------------- ModR/M, SIB */
/* Convenience flags */
#define MODRM_EA 1 /* ModR/M is an effective addr */
#define MODRM_reg 2 /* ModR/M is a register */
/* ModR/M flags */
#define MODRM_RM_SIB 0x04 /* R/M == 100 */
#define MODRM_RM_NOREG 0x05 /* R/B == 101 */
/* if (MODRM.MOD_NODISP && MODRM.RM_NOREG) then just disp32 */
#define MODRM_MOD_NODISP 0x00 /* mod == 00 */
#define MODRM_MOD_DISP8 0x01 /* mod == 01 */
#define MODRM_MOD_DISP32 0x02 /* mod == 10 */
#define MODRM_MOD_NOEA 0x03 /* mod == 11 */
/* 16-bit modrm flags */
#define MOD16_MOD_NODISP 0
#define MOD16_MOD_DISP8 1
#define MOD16_MOD_DISP16 2
#define MOD16_MOD_REG 3
#define MOD16_RM_BXSI 0
#define MOD16_RM_BXDI 1
#define MOD16_RM_BPSI 2
#define MOD16_RM_BPDI 3
#define MOD16_RM_SI 4
#define MOD16_RM_DI 5
#define MOD16_RM_BP 6
#define MOD16_RM_BX 7
/* SIB flags */
#define SIB_INDEX_NONE 0x04
#define SIB_BASE_EBP 0x05
#define SIB_SCALE_NOBASE 0x00
/* Convenience struct for modR/M bitfield */
struct modRM_byte {
unsigned int mod : 2;
unsigned int reg : 3;
unsigned int rm : 3;
};
/* Convenience struct for SIB bitfield */
struct SIB_byte {
unsigned int scale : 2;
unsigned int index : 3;
unsigned int base : 3;
};
#ifdef WIN32
static void byte_decode(unsigned char b, struct modRM_byte *modrm) {
#else
static inline void byte_decode(unsigned char b, struct modRM_byte *modrm) {
#endif
/* generic bitfield-packing routine */
modrm->mod = b >> 6; /* top 2 bits */
modrm->reg = (b & 56) >> 3; /* middle 3 bits */
modrm->rm = b & 7; /* bottom 3 bits */
}
static int ia32_invariant_modrm( unsigned char *in, unsigned char *out,
unsigned int mode_16, x86_invariant_op_t *op) {
struct modRM_byte modrm;
struct SIB_byte sib;
unsigned char *c, *cin;
unsigned short *s;
unsigned int *i;
int size = 0; /* modrm byte is already counted */
byte_decode(*in, &modrm); /* get bitfields */
out[0] = in[0]; /* save modrm byte */
cin = &in[1];
c = &out[1];
s = (unsigned short *)&out[1];
i = (unsigned int *)&out[1];
op->type = op_expression;
op->flags |= op_pointer;
if ( ! mode_16 && modrm.rm == MODRM_RM_SIB &&
modrm.mod != MODRM_MOD_NOEA ) {
size ++;
byte_decode(*cin, (struct modRM_byte *)(void*)&sib);
out[1] = in[1]; /* save sib byte */
cin = &in[2];
c = &out[2];
s = (unsigned short *)&out[2];
i = (unsigned int *)&out[2];
if ( sib.base == SIB_BASE_EBP && ! modrm.mod ) {
/* disp 32 is variant! */
memset( i, X86_WILDCARD_BYTE, 4 );
size += 4;
}
}
if (! modrm.mod && modrm.rm == 101) {
if ( mode_16 ) { /* straight RVA in disp */
memset( s, X86_WILDCARD_BYTE, 2 );
size += 2;
} else {
memset( i, X86_WILDCARD_BYTE, 2 );
size += 4;
}
} else if (modrm.mod && modrm.mod < 3) {
if (modrm.mod == MODRM_MOD_DISP8) { /* offset in disp */
*c = *cin;
size += 1;
} else if ( mode_16 ) {
*s = (* ((unsigned short *) cin));
size += 2;
} else {
*i = (*((unsigned int *) cin));
size += 4;
}
} else if ( modrm.mod == 3 ) {
op->type = op_register;
op->flags &= ~op_pointer;
}
return (size);
}
static int ia32_decode_invariant( unsigned char *buf, size_t buf_len,
ia32_insn_t *t, unsigned char *out,
unsigned int prefixes, x86_invariant_t *inv) {
unsigned int addr_size, op_size, mode_16;
unsigned int op_flags[3] = { t->dest_flag, t->src_flag, t->aux_flag };
int x, type, bytes = 0, size = 0, modrm = 0;
/* set addressing mode */
if (ia32_settings.options & opt_16_bit) {
op_size = ( prefixes & PREFIX_OP_SIZE ) ? 4 : 2;
addr_size = ( prefixes & PREFIX_ADDR_SIZE ) ? 4 : 2;
mode_16 = ( prefixes & PREFIX_ADDR_SIZE ) ? 0 : 1;
} else {
op_size = ( prefixes & PREFIX_OP_SIZE ) ? 2 : 4;
addr_size = ( prefixes & PREFIX_ADDR_SIZE ) ? 2 : 4;
mode_16 = ( prefixes & PREFIX_ADDR_SIZE ) ? 1 : 0;
}
for (x = 0; x < 3; x++) {
inv->operands[x].access = (enum x86_op_access)
OP_PERM(op_flags[x]);
inv->operands[x].flags = (enum x86_op_flags)
(OP_FLAGS(op_flags[x]) >> 12);
switch (op_flags[x] & OPTYPE_MASK) {
case OPTYPE_c:
size = (op_size == 4) ? 2 : 1;
break;
case OPTYPE_a: case OPTYPE_v:
size = (op_size == 4) ? 4 : 2;
break;
case OPTYPE_p:
size = (op_size == 4) ? 6 : 4;
break;
case OPTYPE_b:
size = 1;
break;
case OPTYPE_w:
size = 2;
break;
case OPTYPE_d: case OPTYPE_fs: case OPTYPE_fd:
case OPTYPE_fe: case OPTYPE_fb: case OPTYPE_fv:
case OPTYPE_si: case OPTYPE_fx:
size = 4;
break;
case OPTYPE_s:
size = 6;
break;
case OPTYPE_q: case OPTYPE_pi:
size = 8;
break;
case OPTYPE_dq: case OPTYPE_ps: case OPTYPE_ss:
case OPTYPE_pd: case OPTYPE_sd:
size = 16;
break;
case OPTYPE_m:
size = (addr_size == 4) ? 4 : 2;
break;
default:
break;
}
type = op_flags[x] & ADDRMETH_MASK;
switch (type) {
case ADDRMETH_E: case ADDRMETH_M: case ADDRMETH_Q:
case ADDRMETH_R: case ADDRMETH_W:
modrm = 1;
bytes += ia32_invariant_modrm( buf, out,
mode_16, &inv->operands[x]);
break;
case ADDRMETH_C: case ADDRMETH_D: case ADDRMETH_G:
case ADDRMETH_P: case ADDRMETH_S: case ADDRMETH_T:
case ADDRMETH_V:
inv->operands[x].type = op_register;
modrm = 1;
break;
case ADDRMETH_A: case ADDRMETH_O:
/* pad with xF4's */
memset( &out[bytes + modrm], X86_WILDCARD_BYTE,
size );
bytes += size;
inv->operands[x].type = op_offset;
if ( type == ADDRMETH_O ) {
inv->operands[x].flags |= op_signed |
op_pointer;
}
break;
case ADDRMETH_I: case ADDRMETH_J:
/* grab imm value */
if ((op_flags[x] & OPTYPE_MASK) == OPTYPE_v) {
/* assume this is an address */
memset( &out[bytes + modrm],
X86_WILDCARD_BYTE, size );
} else {
memcpy( &out[bytes + modrm],
&buf[bytes + modrm], size );
}
bytes += size;
if ( type == ADDRMETH_J ) {
if ( size == 1 ) {
inv->operands[x].type =
op_relative_near;
} else {
inv->operands[x].type =
op_relative_far;
}
inv->operands[x].flags |= op_signed;
} else {
inv->operands[x].type = op_immediate;
}
break;
case ADDRMETH_F:
inv->operands[x].type = op_register;
break;
case ADDRMETH_X:
inv->operands[x].flags |= op_signed |
op_pointer | op_ds_seg | op_string;
break;
case ADDRMETH_Y:
inv->operands[x].flags |= op_signed |
op_pointer | op_es_seg | op_string;
break;
case ADDRMETH_RR:
inv->operands[x].type = op_register;
break;
case ADDRMETH_II:
inv->operands[x].type = op_immediate;
break;
default:
inv->operands[x].type = op_unused;
break;
}
}
return (bytes + modrm);
}
size_t ia32_disasm_invariant( unsigned char * buf, size_t buf_len,
x86_invariant_t *inv ) {
ia32_insn_t *raw_insn = NULL;
unsigned int prefixes;
unsigned int type;
size_t size;
/* Perform recursive table lookup starting with main table (0) */
size = ia32_table_lookup( buf, buf_len, 0, &raw_insn, &prefixes );
if ( size == INVALID_INSN || size > buf_len ) {
/* TODO: set errno */
return 0;
}
/* copy opcode bytes to buffer */
memcpy( inv->bytes, buf, size );
/* set mnemonic type and group */
type = raw_insn->mnem_flag & ~INS_FLAG_MASK;
inv->group = (enum x86_insn_group) (INS_GROUP(type)) >> 12;
inv->type = (enum x86_insn_type) INS_TYPE(type);
/* handle operands */
size += ia32_decode_invariant( buf + size, buf_len - size, raw_insn,
&buf[size - 1], prefixes, inv );
inv->size = size;
return size; /* return size of instruction in bytes */
}
size_t ia32_disasm_size( unsigned char *buf, size_t buf_len ) {
x86_invariant_t inv = { {0} };
return( ia32_disasm_invariant( buf, buf_len, &inv ) );
}
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