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popnhax/libdisasm/ia32_operand.c

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#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "libdis.h"
#include "ia32_insn.h"
#include "ia32_operand.h"
#include "ia32_modrm.h"
#include "ia32_reg.h"
#include "x86_imm.h"
#include "x86_operand_list.h"
/* apply segment override to memory operand in insn */
static void apply_seg( x86_op_t *op, unsigned int prefixes ) {
if (! prefixes ) return;
/* apply overrides from prefix */
switch ( prefixes & PREFIX_REG_MASK ) {
case PREFIX_CS:
op->flags |= op_cs_seg; break;
case PREFIX_SS:
op->flags |= op_ss_seg; break;
case PREFIX_DS:
op->flags |= op_ds_seg; break;
case PREFIX_ES:
op->flags |= op_es_seg; break;
case PREFIX_FS:
op->flags |= op_fs_seg; break;
case PREFIX_GS:
op->flags |= op_gs_seg; break;
}
return;
}
static size_t decode_operand_value( unsigned char *buf, size_t buf_len,
x86_op_t *op, x86_insn_t *insn,
unsigned int addr_meth, size_t op_size,
unsigned int op_value, unsigned char modrm,
size_t gen_regs ) {
size_t size = 0;
/* ++ Do Operand Addressing Method / Decode operand ++ */
switch (addr_meth) {
/* This sets the operand Size based on the Intel Opcode Map
* (Vol 2, Appendix A). Letter encodings are from section
* A.1.1, 'Codes for Addressing Method' */
/* ---------------------- Addressing Method -------------- */
/* Note that decoding mod ModR/M operand adjusts the size of
* the instruction, but decoding the reg operand does not.
* This should not cause any problems, as every 'reg' operand
* has an associated 'mod' operand.
* Goddamn-Intel-Note:
* Some Intel addressing methods [M, R] specify that modR/M
* byte may only refer to a memory address/may only refer to
* a register -- however Intel provides no clues on what to do
* if, say, the modR/M for an M opcode decodes to a register
* rather than a memory address ... returning 0 is out of the
* question, as this would be an Immediate or a RelOffset, so
* instead these modR/Ms are decoded with total disregard to
* the M, R constraints. */
/* MODRM -- mod operand. sets size to at least 1! */
case ADDRMETH_E: /* ModR/M present, Gen reg or memory */
size = ia32_modrm_decode( buf, buf_len, op, insn,
gen_regs );
break;
case ADDRMETH_M: /* ModR/M only refers to memory */
size = ia32_modrm_decode( buf, buf_len, op, insn,
gen_regs );
break;
case ADDRMETH_Q: /* ModR/M present, MMX or Memory */
size = ia32_modrm_decode( buf, buf_len, op, insn,
REG_MMX_OFFSET );
break;
case ADDRMETH_R: /* ModR/M mod == gen reg */
size = ia32_modrm_decode( buf, buf_len, op, insn,
gen_regs );
break;
case ADDRMETH_W: /* ModR/M present, mem or SIMD reg */
size = ia32_modrm_decode( buf, buf_len, op, insn,
REG_SIMD_OFFSET );
break;
/* MODRM -- reg operand. does not effect size! */
case ADDRMETH_C: /* ModR/M reg == control reg */
ia32_reg_decode( modrm, op, REG_CTRL_OFFSET );
break;
case ADDRMETH_D: /* ModR/M reg == debug reg */
ia32_reg_decode( modrm, op, REG_DEBUG_OFFSET );
break;
case ADDRMETH_G: /* ModR/M reg == gen-purpose reg */
ia32_reg_decode( modrm, op, gen_regs );
break;
case ADDRMETH_P: /* ModR/M reg == qword MMX reg */
ia32_reg_decode( modrm, op, REG_MMX_OFFSET );
break;
case ADDRMETH_S: /* ModR/M reg == segment reg */
ia32_reg_decode( modrm, op, REG_SEG_OFFSET );
break;
case ADDRMETH_T: /* ModR/M reg == test reg */
ia32_reg_decode( modrm, op, REG_TEST_OFFSET );
break;
case ADDRMETH_V: /* ModR/M reg == SIMD reg */
ia32_reg_decode( modrm, op, REG_SIMD_OFFSET );
break;
/* No MODRM : note these set operand type explicitly */
case ADDRMETH_A: /* No modR/M -- direct addr */
op->type = op_absolute;
/* segment:offset address used in far calls */
x86_imm_sized( buf, buf_len,
&op->data.absolute.segment, 2 );
if ( insn->addr_size == 4 ) {
x86_imm_sized( buf, buf_len,
&op->data.absolute.offset.off32, 4 );
size = 6;
} else {
x86_imm_sized( buf, buf_len,
&op->data.absolute.offset.off16, 2 );
size = 4;
}
break;
case ADDRMETH_I: /* Immediate val */
op->type = op_immediate;
/* if it ever becomes legal to have imm as dest and
* there is a src ModR/M operand, we are screwed! */
if ( op->flags & op_signed ) {
x86_imm_signsized(buf, buf_len, &op->data.byte,
op_size);
} else {
x86_imm_sized(buf, buf_len, &op->data.byte,
op_size);
}
size = op_size;
break;
case ADDRMETH_J: /* Rel offset to add to IP [jmp] */
/* this fills op->data.near_offset or
op->data.far_offset depending on the size of
the operand */
op->flags |= op_signed;
if ( op_size == 1 ) {
/* one-byte near offset */
op->type = op_relative_near;
x86_imm_signsized(buf, buf_len,
&op->data.relative_near, 1);
} else {
/* far offset...is this truly signed? */
op->type = op_relative_far;
x86_imm_signsized(buf, buf_len,
&op->data.relative_far, op_size );
}
size = op_size;
break;
case ADDRMETH_O: /* No ModR/M; op is word/dword offset */
/* NOTE: these are actually RVAs not offsets to seg!! */
/* note bene: 'O' ADDR_METH uses addr_size to
determine operand size */
op->type = op_offset;
op->flags |= op_pointer;
x86_imm_sized( buf, buf_len, &op->data.offset,
insn->addr_size );
size = insn->addr_size;
break;
/* Hard-coded: these are specified in the insn definition */
case ADDRMETH_F: /* EFLAGS register */
op->type = op_register;
op->flags |= op_hardcode;
ia32_handle_register( &op->data.reg, REG_FLAGS_INDEX );
break;
case ADDRMETH_X: /* Memory addressed by DS:SI [string] */
op->type = op_expression;
op->flags |= op_hardcode;
op->flags |= op_ds_seg | op_pointer | op_string;
ia32_handle_register( &op->data.expression.base,
REG_DWORD_OFFSET + 6 );
break;
case ADDRMETH_Y: /* Memory addressed by ES:DI [string] */
op->type = op_expression;
op->flags |= op_hardcode;
op->flags |= op_es_seg | op_pointer | op_string;
ia32_handle_register( &op->data.expression.base,
REG_DWORD_OFFSET + 7 );
break;
case ADDRMETH_RR: /* Gen Register hard-coded in opcode */
op->type = op_register;
op->flags |= op_hardcode;
ia32_handle_register( &op->data.reg,
op_value + gen_regs );
break;
case ADDRMETH_RS: /* Seg Register hard-coded in opcode */
op->type = op_register;
op->flags |= op_hardcode;
ia32_handle_register( &op->data.reg,
op_value + REG_SEG_OFFSET );
break;
case ADDRMETH_RF: /* FPU Register hard-coded in opcode */
op->type = op_register;
op->flags |= op_hardcode;
ia32_handle_register( &op->data.reg,
op_value + REG_FPU_OFFSET );
break;
case ADDRMETH_RT: /* TST Register hard-coded in opcode */
op->type = op_register;
op->flags |= op_hardcode;
ia32_handle_register( &op->data.reg,
op_value + REG_TEST_OFFSET );
break;
case ADDRMETH_II: /* Immediate hard-coded in opcode */
op->type = op_immediate;
op->data.dword = op_value;
op->flags |= op_hardcode;
break;
case 0: /* Operand is not used */
default:
/* ignore -- operand not used in this insn */
op->type = op_unused; /* this shouldn't happen! */
break;
}
return size;
}
static size_t decode_operand_size( unsigned int op_type, x86_insn_t *insn,
x86_op_t *op ){
size_t size;
/* ++ Do Operand Type ++ */
switch (op_type) {
/* This sets the operand Size based on the Intel Opcode Map
* (Vol 2, Appendix A). Letter encodings are from section
* A.1.2, 'Codes for Operand Type' */
/* NOTE: in this routines, 'size' refers to the size
* of the operand in the raw (encoded) instruction;
* 'datatype' stores the actual size and datatype
* of the operand */
/* ------------------------ Operand Type ----------------- */
case OPTYPE_c: /* byte or word [op size attr] */
size = (insn->op_size == 4) ? 2 : 1;
op->datatype = (size == 4) ? op_word : op_byte;
break;
case OPTYPE_a: /* 2 word or 2 dword [op size attr] */
/* pointer to a 16:16 or 32:32 BOUNDS operand */
size = (insn->op_size == 4) ? 8 : 4;
op->datatype = (size == 4) ? op_bounds32 : op_bounds16;
break;
case OPTYPE_v: /* word or dword [op size attr] */
size = (insn->op_size == 4) ? 4 : 2;
op->datatype = (size == 4) ? op_dword : op_word;
break;
case OPTYPE_p: /* 32/48-bit ptr [op size attr] */
/* technically these flags are not accurate: the
* value s a 16:16 pointer or a 16:32 pointer, where
* the first '16' is a segment */
size = (insn->addr_size == 4) ? 6 : 4;
op->datatype = (size == 4) ? op_descr32 : op_descr16;
break;
case OPTYPE_b: /* byte, ignore op-size */
size = 1;
op->datatype = op_byte;
break;
case OPTYPE_w: /* word, ignore op-size */
size = 2;
op->datatype = op_word;
break;
case OPTYPE_d: /* dword , ignore op-size */
size = 4;
op->datatype = op_dword;
break;
case OPTYPE_s: /* 6-byte psuedo-descriptor */
/* ptr to 6-byte value which is 32:16 in 32-bit
* mode, or 8:24:16 in 16-bit mode. The high byte
* is ignored in 16-bit mode. */
size = 6;
op->datatype = (insn->addr_size == 4) ?
op_pdescr32 : op_pdescr16;
break;
case OPTYPE_q: /* qword, ignore op-size */
size = 8;
op->datatype = op_qword;
break;
case OPTYPE_dq: /* d-qword, ignore op-size */
size = 16;
op->datatype = op_dqword;
break;
case OPTYPE_ps: /* 128-bit FP data */
size = 16;
/* really this is 4 packed SP FP values */
op->datatype = op_ssimd;
break;
case OPTYPE_pd: /* 128-bit FP data */
size = 16;
/* really this is 2 packed DP FP values */
op->datatype = op_dsimd;
break;
case OPTYPE_ss: /* Scalar elem of 128-bit FP data */
size = 16;
/* this only looks at the low dword (4 bytes)
* of the xmmm register passed as a param.
* This is a 16-byte register where only 4 bytes
* are used in the insn. Painful, ain't it? */
op->datatype = op_sssimd;
break;
case OPTYPE_sd: /* Scalar elem of 128-bit FP data */
size = 16;
/* this only looks at the low qword (8 bytes)
* of the xmmm register passed as a param.
* This is a 16-byte register where only 8 bytes
* are used in the insn. Painful, again... */
op->datatype = op_sdsimd;
break;
case OPTYPE_pi: /* qword mmx register */
size = 8;
op->datatype = op_qword;
break;
case OPTYPE_si: /* dword integer register */
size = 4;
op->datatype = op_dword;
break;
case OPTYPE_fs: /* single-real */
size = 4;
op->datatype = op_sreal;
break;
case OPTYPE_fd: /* double real */
size = 8;
op->datatype = op_dreal;
break;
case OPTYPE_fe: /* extended real */
size = 10;
op->datatype = op_extreal;
break;
case OPTYPE_fb: /* packed BCD */
size = 10;
op->datatype = op_bcd;
break;
case OPTYPE_fv: /* pointer to FPU env: 14 or 28-bytes */
size = (insn->addr_size == 4)? 28 : 14;
op->datatype = (size == 28)? op_fpuenv32: op_fpuenv16;
break;
case OPTYPE_ft: /* pointer to FPU env: 94 or 108 bytes */
size = (insn->addr_size == 4)? 108 : 94;
op->datatype = (size == 108)?
op_fpustate32: op_fpustate16;
break;
case OPTYPE_fx: /* 512-byte register stack */
size = 512;
op->datatype = op_fpregset;
break;
case OPTYPE_fp: /* floating point register */
size = 10; /* double extended precision */
op->datatype = op_fpreg;
break;
case OPTYPE_m: /* fake operand type used for "lea Gv, M" */
size = insn->addr_size;
op->datatype = (size == 4) ? op_dword : op_word;
break;
case OPTYPE_none: /* handle weird instructions that have no encoding but use a dword datatype, like invlpg */
size = 0;
op->datatype = op_none;
break;
case 0:
default:
size = insn->op_size;
op->datatype = (size == 4) ? op_dword : op_word;
break;
}
return size;
}
size_t ia32_decode_operand( unsigned char *buf, size_t buf_len,
x86_insn_t *insn, unsigned int raw_op,
unsigned int raw_flags, unsigned int prefixes,
unsigned char modrm ) {
unsigned int addr_meth, op_type, op_size, gen_regs;
x86_op_t *op;
size_t size;
/* ++ Yank optype and addr mode out of operand flags */
addr_meth = raw_flags & ADDRMETH_MASK;
op_type = raw_flags & OPTYPE_MASK;
if ( raw_flags == ARG_NONE ) {
/* operand is not used in this instruction */
return 0;
}
/* allocate a new operand */
op = x86_operand_new( insn );
/* ++ Copy flags from opcode table to x86_insn_t */
op->access = (enum x86_op_access) OP_PERM(raw_flags);
op->flags = (enum x86_op_flags) (OP_FLAGS(raw_flags) >> 12);
/* Get size (for decoding) and datatype of operand */
op_size = decode_operand_size(op_type, insn, op);
/* override default register set based on Operand Type */
/* this allows mixing of 8, 16, and 32 bit regs in insn */
if (op_size == 1) {
gen_regs = REG_BYTE_OFFSET;
} else if (op_size == 2) {
gen_regs = REG_WORD_OFFSET;
} else {
gen_regs = REG_DWORD_OFFSET;
}
size = decode_operand_value( buf, buf_len, op, insn, addr_meth,
op_size, raw_op, modrm, gen_regs );
/* if operand is an address, apply any segment override prefixes */
if ( op->type == op_expression || op->type == op_offset ) {
apply_seg(op, prefixes);
}
return size; /* return number of bytes in instruction */
}
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