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/* ia32-encode.c - ia32 instruction encoding
*
* by scut
*
* XXX: note, this is just very basic at the moment
*/
#include <assert.h>
#include <stdio.h>
#include <string.h>
#include <ia32-decode.h>
#include <ia32-encode.h>
#include <ia32_opcodes.h>
/* from ia32-decode.c */
extern ia32_opcode_e ia32_opcode_table[];
/*** STATIC PROTOTYPES */
/* ia32_encode_instruction_try
*
* try encoding the instruction `inst' to memory `dest'.
*
* return zero on failure
* return length of complete instruction (prefix and opcode) on success
*/
static unsigned int
ia32_encode_instruction_try (ia32_instruction *inst, unsigned char *dest);
/*** IMPLEMENTATION */
unsigned int
ia32_encode_instruction (unsigned int inst_num, ia32_instruction *inst,
unsigned char *dest)
{
unsigned int in, /* instruction list walker */
len;
if (inst_num == IA32_OP_rcr || inst_num == IA32_OP_rcl)
printf ("foo\n");
for (in = 0 ; ia32_opcode_table[in].opcode_num != 0 ; ++in) {
if (ia32_opcode_table[in].opcode_num != inst_num)
continue;
inst->opc.opcode = &ia32_opcode_table[in];
len = ia32_encode_instruction_try (inst, dest);
if (len > 0)
return (len);
}
printf ("failed at opcode %d, \"%s\" (t: %d, s: %d)\n",
inst_num, inst->opc.opcode->name, inst->opc.target_reg,
inst->opc.source_reg);
return (0);
}
/* rather incomplete. will grow over time
*/
static unsigned int
ia32_encode_instruction_try (ia32_instruction *inst, unsigned char *dest)
{
unsigned int dn = 0, /* relative dest buffer offset */
bp;
int did_source = 0,
did_target = 0;
unsigned int source_reg,
target_reg;
ia32_opcode_e * oel = inst->opc.opcode;
/* 1. prefix
*/
if (inst->pfx.lock)
dest[dn++] = IA32_PREFIX_CODE_LOCK;
switch (inst->pfx.rep) {
case (IA32_PREFIX_REPNE):
dest[dn++] = IA32_PREFIX_CODE_REPNE;
break;
case (IA32_PREFIX_REP):
dest[dn++] = IA32_PREFIX_CODE_REP;
break;
default:
break;
}
if (inst->pfx.oper_size)
dest[dn++] = IA32_PREFIX_CODE_OPER;
if (inst->pfx.addr_size)
dest[dn++] = IA32_PREFIX_CODE_ADDR;
/* 2. TODO: set displacement/immediate size according to prefix */
if ((OD_TEST (oel->flags, OD_IMM) == 0 &&
inst->opc.source_type == OP_TYPE_IMM) ||
(OD_TEST (oel->flags, OD_IMM) &&
inst->opc.source_type != OP_TYPE_IMM))
{
return (0);
}
if (OD_TEST (oel->flags, OD_IMM_DISPL) ||
OD_TEST (oel->flags, OD_IMM_OFFSET) ||
OD_TEST (oel->flags, OD_IMM_OFFSET) ||
OD_TEST (oel->flags, OD_CONTROL))
return (0);
if (OD_TEST (oel->flags, OD_REG_HARD_EAX)) {
if (inst->opc.target_reg != IA32_REG_EAX)
return (0);
did_target = 1;
}
if (inst->opc.source_type == OP_TYPE_IMM) {
if (inst->opc.imm_size != IA32_WIDTH_32)
return (0);
inst->opc.wide = 1;
}
if (OD_TEST (oel->flags, OD_REG12_REV)) {
inst->opc.reversed = 1;
source_reg = inst->opc.target_reg;
target_reg = inst->opc.source_reg;
} else {
source_reg = inst->opc.source_reg;
target_reg = inst->opc.target_reg;
}
assert (inst->opc.target_type == OP_TYPE_REG &&
(inst->opc.source_type == OP_TYPE_REG ||
inst->opc.source_type == OP_TYPE_IMM));
for (bp = 0 ; oel->opc[bp] != OD_END ; ++bp) {
unsigned int oc;
unsigned char db;
oc = oel->opc[bp];
db = (oc & 0xff) & ((oc & 0xff00) >> 8);
if (OD_TEST (oc, OD_W))
db |= inst->opc.wide ? OD_W_MASK : 0x00;
else if (OD_TEST (oc, OD_W3))
db |= inst->opc.wide ? OD_W3_MASK : 0x00;
/* TODO: S flag */
/* TODO: D flag */
if (OD_TEST (oc, OD_LREG)) {
if (OD_TEST (oel->flags, OD_REG_HARD_EAX)) {
db |= source_reg;
did_source = 1;
} else {
db |= target_reg;
did_target = 1;
}
}
if (OD_TEST (oc, OD_MOD)) {
if (inst->opc.source_type == OP_TYPE_IMM) {
db |= OD_MOD_MASK; /* 11b = reg/reg */
if (OD_TEST (oc, OD_REG)) {
db |= source_reg << OD_REG_SHIFT;
did_source = 1;
}
} else {
db |= OD_MOD_MASK; /* 11b = reg/reg */
if (OD_TEST (oc, OD_REG)) {
db |= source_reg << OD_REG_SHIFT;
did_source = 1;
}
}
/* set bits 210 (OD_REG2) */
db |= target_reg;
did_target = 1;
}
dest[dn++] = db;
}
if (inst->opc.source_type == OP_TYPE_IMM) {
ia32_encode_value (&dest[dn], inst->opc.imm_size,
inst->opc.imm_value);
dn += ia32_bit_to_byte (inst->opc.imm_size);
}
#if 0
if (did_source == 0 || did_target == 0)
return (0);
#endif
return (dn);
}
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