disasm.c

nasm的全套源代码,有些我做了些修改,以方便您更方便更容易调试成功,方便学习做编译器

        if (c >= 064 && c <= 066) {
            ins->oprs[c - 064].offset = *data++;
            ins->oprs[c - 064].offset |= (((unsigned)*data++) << 8);
            if (osize == 32) {
                ins->oprs[c - 064].offset |= (((long)*data++) << 16);
                ins->oprs[c - 064].offset |= (((long)*data++) << 24);
                ins->oprs[c - 064].segment |= SEG_32BIT;
            } else
                ins->oprs[c - 064].segment &= ~SEG_32BIT;
            ins->oprs[c - 064].segment |= SEG_RELATIVE;
            if (segsize != osize) {
                ins->oprs[c - 064].type =
                    (ins->oprs[c - 064].type & NON_SIZE)
                    | ((osize == 16) ? BITS16 : BITS32);
            }
        }
        if (c >= 070 && c <= 072) {
            ins->oprs[c - 070].offset = *data++;
            ins->oprs[c - 070].offset |= (((unsigned)*data++) << 8);
            ins->oprs[c - 070].offset |= (((long)*data++) << 16);
            ins->oprs[c - 070].offset |= (((long)*data++) << 24);
            ins->oprs[c - 070].segment |= SEG_32BIT | SEG_RELATIVE;
        }
        if (c >= 0100 && c < 0130) {
            int modrm = *data++;
            ins->oprs[c & 07].basereg = (modrm >> 3) & 07;
            ins->oprs[c & 07].segment |= SEG_RMREG;
            data = do_ea(data, modrm, asize, segsize,
                         &ins->oprs[(c >> 3) & 07]);
        }
        if (c >= 0130 && c <= 0132) {
            ins->oprs[c - 0130].offset = *data++;
            ins->oprs[c - 0130].offset |= (((unsigned)*data++) << 8);
        }
        if (c >= 0140 && c <= 0142) {
            ins->oprs[c - 0140].offset = *data++;
            ins->oprs[c - 0140].offset |= (((unsigned)*data++) << 8);
            ins->oprs[c - 0140].offset |= (((long)*data++) << 16);
            ins->oprs[c - 0140].offset |= (((long)*data++) << 24);
        }
        if (c >= 0200 && c <= 0277) {
            int modrm = *data++;
            if (((modrm >> 3) & 07) != (c & 07))
                return FALSE;   /* spare field doesn't match up */
            data = do_ea(data, modrm, asize, segsize,
                         &ins->oprs[(c >> 3) & 07]);
        }
        if (c >= 0300 && c <= 0302) {
            if (asize)
                ins->oprs[c - 0300].segment |= SEG_32BIT;
            else
                ins->oprs[c - 0300].segment &= ~SEG_32BIT;
            a_used = TRUE;
        }
        if (c == 0310) {
            if (asize == 32)
                return FALSE;
            else
                a_used = TRUE;
        }
        if (c == 0311) {
            if (asize == 16)
                return FALSE;
            else
                a_used = TRUE;
        }
        if (c == 0312) {
            if (asize != segsize)
                return FALSE;
            else
                a_used = TRUE;
        }
        if (c == 0320) {
            if (osize == 32)
                return FALSE;
            else
                o_used = TRUE;
        }
        if (c == 0321) {
            if (osize == 16)
                return FALSE;
            else
                o_used = TRUE;
        }
        if (c == 0322) {
            if (osize != segsize)
                return FALSE;
            else
                o_used = TRUE;
        }
        if (c == 0330) {
            int t = *r++, d = *data++;
            if (d < t || d > t + 15)
                return FALSE;
            else
                ins->condition = d - t;
        }
        if (c == 0331) {
            if (rep)
                return FALSE;
        }
        if (c == 0332) {
            if (drep == P_REP)
                drep = P_REPE;
        }
        if (c == 0333) {
            if (rep != 0xF3)
                return FALSE;
            drep = 0;
        }
    }

    /*
     * Check for unused rep or a/o prefixes.
     */
    ins->nprefix = 0;
    if (drep)
        ins->prefixes[ins->nprefix++] = drep;
    if (!a_used && asize != segsize)
        ins->prefixes[ins->nprefix++] = (asize == 16 ? P_A16 : P_A32);
    if (!o_used && osize != segsize)
        ins->prefixes[ins->nprefix++] = (osize == 16 ? P_O16 : P_O32);

    return data - origdata;
}

long disasm(unsigned char *data, char *output, int outbufsize, int segsize,
            long offset, int autosync, unsigned long prefer)
{
    struct itemplate **p, **best_p;
    int length, best_length = 0;
    char *segover;
    int rep, lock, asize, osize, i, slen, colon;
    unsigned char *origdata;
    int works;
    insn tmp_ins, ins;
    unsigned long goodness, best;

    /*
     * Scan for prefixes.
     */
    asize = osize = segsize;
    segover = NULL;
    rep = lock = 0;
    origdata = data;
    for (;;) {
        if (*data == 0xF3 || *data == 0xF2)
            rep = *data++;
        else if (*data == 0xF0)
            lock = *data++;
        else if (*data == 0x2E || *data == 0x36 || *data == 0x3E ||
                 *data == 0x26 || *data == 0x64 || *data == 0x65) {
            switch (*data++) {
            case 0x2E:
                segover = "cs";
                break;
            case 0x36:
                segover = "ss";
                break;
            case 0x3E:
                segover = "ds";
                break;
            case 0x26:
                segover = "es";
                break;
            case 0x64:
                segover = "fs";
                break;
            case 0x65:
                segover = "gs";
                break;
            }
        } else if (*data == 0x66)
            osize = 48 - segsize, data++;
        else if (*data == 0x67)
            asize = 48 - segsize, data++;
        else
            break;
    }

    tmp_ins.oprs[0].segment = tmp_ins.oprs[1].segment =
        tmp_ins.oprs[2].segment =
        tmp_ins.oprs[0].addr_size = tmp_ins.oprs[1].addr_size =
        tmp_ins.oprs[2].addr_size = (segsize == 16 ? 0 : SEG_32BIT);
    tmp_ins.condition = -1;
    best = ~0UL;                /* Worst possible */
    best_p = NULL;
    for (p = itable[*data]; *p; p++) {
        if ((length = matches(*p, data, asize, osize,
                              segsize, rep, &tmp_ins))) {
            works = TRUE;
            /*
             * Final check to make sure the types of r/m match up.
             */
            for (i = 0; i < (*p)->operands; i++) {
                if (
                       /* If it's a mem-only EA but we have a register, die. */
                       ((tmp_ins.oprs[i].segment & SEG_RMREG) &&
                        !(MEMORY & ~(*p)->opd[i])) ||
                       /* If it's a reg-only EA but we have a memory ref, die. */
                       (!(tmp_ins.oprs[i].segment & SEG_RMREG) &&
                        !(REGNORM & ~(*p)->opd[i]) &&
                        !((*p)->opd[i] & REG_SMASK)) ||
                       /* Register type mismatch (eg FS vs REG_DESS): die. */
                       ((((*p)->opd[i] & (REGISTER | FPUREG)) ||
                         (tmp_ins.oprs[i].segment & SEG_RMREG)) &&
                        !whichreg((*p)->opd[i],
                                  tmp_ins.oprs[i].basereg))) {
                    works = FALSE;
                    break;
                }
            }

            if (works) {
                goodness = ((*p)->flags & IF_PFMASK) ^ prefer;
                if (goodness < best) {
                    /* This is the best one found so far */
                    best = goodness;
                    best_p = p;
                    best_length = length;
                    ins = tmp_ins;
                }
            }
        }
    }

    if (!best_p)
        return 0;               /* no instruction was matched */

    /* Pick the best match */
    p = best_p;
    length = best_length;

    slen = 0;

    /* TODO: snprintf returns the value that the string would have if
     *      the buffer were long enough, and not the actual length of 
     *      the returned string, so each instance of using the return
     *      value of snprintf should actually be checked to assure that
     *      the return value is "sane."  Maybe a macro wrapper could
     *      be used for that purpose.
     */
    if (lock)
        slen += snprintf(output + slen, outbufsize - slen, "lock ");
    for (i = 0; i < ins.nprefix; i++)
        switch (ins.prefixes[i]) {
        case P_REP:
            slen += snprintf(output + slen, outbufsize - slen, "rep ");
            break;
        case P_REPE:
            slen += snprintf(output + slen, outbufsize - slen, "repe ");
            break;
        case P_REPNE:
            slen += snprintf(output + slen, outbufsize - slen, "repne ");
            break;
        case P_A16:
            slen += snprintf(output + slen, outbufsize - slen, "a16 ");
            break;
        case P_A32:
            slen += snprintf(output + slen, outbufsize - slen, "a32 ");
            break;
        case P_O16:
            slen += snprintf(output + slen, outbufsize - slen, "o16 ");
            break;
        case P_O32:
            slen += snprintf(output + slen, outbufsize - slen, "o32 ");
            break;
        }

    for (i = 0; i < elements(ico); i++)
        if ((*p)->opcode == ico[i]) {
            slen +=
                snprintf(output + slen, outbufsize - slen, "%s%s", icn[i],
                         whichcond(ins.condition));
            break;
        }
    if (i >= elements(ico))
        slen +=
            snprintf(output + slen, outbufsize - slen, "%s",
                     insn_names[(*p)->opcode]);
    colon = FALSE;
    length += data - origdata;  /* fix up for prefixes */
    for (i = 0; i < (*p)->operands; i++) {
        output[slen++] = (colon ? ':' : i == 0 ? ' ' : ',');

        if (ins.oprs[i].segment & SEG_RELATIVE) {
            ins.oprs[i].offset += offset + length;
            /*
             * sort out wraparound
             */
            if (!(ins.oprs[i].segment & SEG_32BIT))
                ins.oprs[i].offset &= 0xFFFF;
            /*
             * add sync marker, if autosync is on
             */
            if (autosync)
                add_sync(ins.oprs[i].offset, 0L);
        }

        if ((*p)->opd[i] & COLON)
            colon = TRUE;
        else
            colon = FALSE;

        if (((*p)->opd[i] & (REGISTER | FPUREG)) ||
            (ins.oprs[i].segment & SEG_RMREG)) {
            ins.oprs[i].basereg = whichreg((*p)->opd[i],
                                           ins.oprs[i].basereg);
            if ((*p)->opd[i] & TO)
                slen += snprintf(output + slen, outbufsize - slen, "to ");
            slen += snprintf(output + slen, outbufsize - slen, "%s",
                             reg_names[ins.oprs[i].basereg -
                                       EXPR_REG_START]);
        } else if (!(UNITY & ~(*p)->opd[i])) {
            output[slen++] = '1';
        } else if ((*p)->opd[i] & IMMEDIATE) {
            if ((*p)->opd[i] & BITS8) {
                slen +=
                    snprintf(output + slen, outbufsize - slen, "byte ");
                if (ins.oprs[i].segment & SEG_SIGNED) {
                    if (ins.oprs[i].offset < 0) {
                        ins.oprs[i].offset *= -1;
                        output[slen++] = '-';
                    } else
                        output[slen++] = '+';
                }
            } else if ((*p)->opd[i] & BITS16) {
                slen +=
                    snprintf(output + slen, outbufsize - slen, "word ");
            } else if ((*p)->opd[i] & BITS32) {
                slen +=
                    snprintf(output + slen, outbufsize - slen, "dword ");
            } else if ((*p)->opd[i] & NEAR) {
                slen +=
                    snprintf(output + slen, outbufsize - slen, "near ");
            } else if ((*p)->opd[i] & SHORT) {
                slen +=
                    snprintf(output + slen, outbufsize - slen, "short ");
            }
            slen +=
                snprintf(output + slen, outbufsize - slen, "0x%lx",
                         ins.oprs[i].offset);
        } else if (!(MEM_OFFS & ~(*p)->opd[i])) {
            slen +=
                snprintf(output + slen, outbufsize - slen, "[%s%s%s0x%lx]",
                         (segover ? segover : ""), (segover ? ":" : ""),
                         (ins.oprs[i].addr_size ==
                          32 ? "dword " : ins.oprs[i].addr_size ==
                          16 ? "word " : ""), ins.oprs[i].offset);
            segover = NULL;
        } else if (!(REGMEM & ~(*p)->opd[i])) {
            int started = FALSE;
            if ((*p)->opd[i] & BITS8)
                slen +=
                    snprintf(output + slen, outbufsize - slen, "byte ");
            if ((*p)->opd[i] & BITS16)
                slen +=
                    snprintf(output + slen, outbufsize - slen, "word ");
            if ((*p)->opd[i] & BITS32)
                slen +=
                    snprintf(output + slen, outbufsize - slen, "dword ");
            if ((*p)->opd[i] & BITS64)
                slen +=
                    snprintf(output + slen, outbufsize - slen, "qword ");
            if ((*p)->opd[i] & BITS80)
                slen +=
                    snprintf(output + slen, outbufsize - slen, "tword ");
            if ((*p)->opd[i] & FAR)
                slen += snprintf(output + slen, outbufsize - slen, "far ");
            if ((*p)->opd[i] & NEAR)
                slen +=
                    snprintf(output + slen, outbufsize - slen, "near ");
            output[slen++] = '[';
            if (ins.oprs[i].addr_size)
                slen += snprintf(output + slen, outbufsize - slen, "%s",
                                 (ins.oprs[i].addr_size == 32 ? "dword " :
                                  ins.oprs[i].addr_size ==
                                  16 ? "word " : ""));
            if (segover) {
                slen +=
                    snprintf(output + slen, outbufsize - slen, "%s:",
                             segover);
                segover = NULL;
            }
            if (ins.oprs[i].basereg != -1) {
                slen += snprintf(output + slen, outbufsize - slen, "%s",
                                 reg_names[(ins.oprs[i].basereg -
                                            EXPR_REG_START)]);
                started = TRUE;
            }
            if (ins.oprs[i].indexreg != -1) {
                if (started)
                    output[slen++] = '+';
                slen += snprintf(output + slen, outbufsize - slen, "%s",
                                 reg_names[(ins.oprs[i].indexreg -
                                            EXPR_REG_START)]);
                if (ins.oprs[i].scale > 1)
                    slen +=
                        snprintf(output + slen, outbufsize - slen, "*%d",
                                 ins.oprs[i].scale);
                started = TRUE;
            }
            if (ins.oprs[i].segment & SEG_DISP8) {
                int sign = '+';
                if (ins.oprs[i].offset & 0x80) {
                    ins.oprs[i].offset = -(signed char)ins.oprs[i].offset;
                    sign = '-';
                }
                slen +=
                    snprintf(output + slen, outbufsize - slen, "%c0x%lx",
                             sign, ins.oprs[i].offset);
            } else if (ins.oprs[i].segment & SEG_DISP16) {
                if (started)
                    output[slen++] = '+';
                slen +=
                    snprintf(output + slen, outbufsize - slen, "0x%lx",
                             ins.oprs[i].offset);
            } else if (ins.oprs[i].segment & SEG_DISP32) {
                if (started)
                    output[slen++] = '+';
                slen +=
                    snprintf(output + slen, outbufsize - slen, "0x%lx",
                             ins.oprs[i].offset);
            }
            output[slen++] = ']';
        } else {
            slen +=
                snprintf(output + slen, outbufsize - slen, "<operand%d>",
                         i);
        }
    }
    output[slen] = '\0';
    if (segover) {              /* unused segment override */
        char *p = output;
        int count = slen + 1;
        while (count--)
            p[count + 3] = p[count];
        strncpy(output, segover, 2);
        output[2] = ' ';
    }
    return length;
}

long eatbyte(unsigned char *data, char *output, int outbufsize)
{
    snprintf(output, outbufsize, "db 0x%02X", *data);
    return 1;
}