outcoff.c

nasm早期的源代码,比较简单是学习汇编和编译原理的好例子

            s = sects[i];
            break;
        }
    if (!s) {
        int tempint;            /* ignored */
        if (segto != coff_section_names(".text", 2, &tempint))
            error(ERR_PANIC, "strange segment conditions in COFF driver");
        else
            s = sects[nsects - 1];
    }

    if (!s->data && type != OUT_RESERVE) {
        error(ERR_WARNING, "attempt to initialize memory in"
              " BSS section `%s': ignored", s->name);
        if (type == OUT_REL2ADR)
            realbytes = 2;
        else if (type == OUT_REL4ADR)
            realbytes = 4;
        s->len += realbytes;
        return;
    }

    if (type == OUT_RESERVE) {
        if (s->data) {
            error(ERR_WARNING, "uninitialised space declared in"
                  " non-BSS section `%s': zeroing", s->name);
            coff_sect_write(s, NULL, realbytes);
        } else
            s->len += realbytes;
    } else if (type == OUT_RAWDATA) {
        if (segment != NO_SEG)
            error(ERR_PANIC, "OUT_RAWDATA with other than NO_SEG");
        coff_sect_write(s, data, realbytes);
    } else if (type == OUT_ADDRESS) {
        if (!(win64)) {
            if (realbytes != 4 && (segment != NO_SEG || wrt != NO_SEG))
                error(ERR_NONFATAL, "COFF format does not support non-32-bit"
                      " relocations");
            else {
                int32_t fix = 0;
                if (segment != NO_SEG || wrt != NO_SEG) {
                    if (wrt != NO_SEG) {
                        error(ERR_NONFATAL, "COFF format does not support"
                              " WRT types");
                    } else if (segment % 2) {
                        error(ERR_NONFATAL, "COFF format does not support"
                              " segment base references");
                    } else
                        fix = coff_add_reloc(s, segment, false, false);
                }
                p = mydata;
                WRITELONG(p, *(int32_t *)data + fix);
                coff_sect_write(s, mydata, realbytes);
            }
        } else {
            int32_t fix = 0;
            p = mydata;
            if (realbytes == 8) {
/*            if (segment != NO_SEG || wrt != NO_SEG) {
                if (wrt != NO_SEG) {
                    error(ERR_NONFATAL, "COFF format does not support"
                          " WRT types");
                } else if (segment % 2) {
                    error(ERR_NONFATAL, "COFF format does not support"
                          " segment base references");
                } else
                    fix = coff_add_reloc(s, segment, false);
            } */
                fix = coff_add_reloc(s, segment, false, true);
                WRITEDLONG(p, *(int64_t *)data + fix);
                coff_sect_write(s, mydata, realbytes);
            } else {
                fix = coff_add_reloc(s, segment, false, false);
                WRITELONG(p, *(int32_t *)data + fix);
                coff_sect_write(s, mydata, realbytes);
            }
        }
    } else if (type == OUT_REL2ADR) {
        error(ERR_NONFATAL, "COFF format does not support 16-bit"
              " relocations");
    } else if (type == OUT_REL4ADR) {
        if (segment == segto && !(win64))  /* Acceptable for RIP-relative */
            error(ERR_PANIC, "intra-segment OUT_REL4ADR");
        else if (segment == NO_SEG && win32)
            error(ERR_NONFATAL, "Win32 COFF does not correctly support"
                  " relative references to absolute addresses");
        else {
            int32_t fix = 0;
            if (segment != NO_SEG && segment % 2) {
                error(ERR_NONFATAL, "COFF format does not support"
                      " segment base references");
            } else
                fix = coff_add_reloc(s, segment, true, false);
            p = mydata;
            if (win32 | win64) {
                WRITELONG(p, *(int32_t *)data + 4 - realbytes + fix);
            } else {
                WRITELONG(p, *(int32_t *)data - (realbytes + s->len) + fix);
            }
            coff_sect_write(s, mydata, 4L);
        }

    }
}

static void coff_sect_write(struct Section *sect,
                            const uint8_t *data, uint32_t len)
{
    saa_wbytes(sect->data, data, len);
    sect->len += len;
}

typedef struct tagString {
    struct tagString *Next;
    int len;
    char *String;
} STRING;

#define EXPORT_SECTION_NAME ".drectve"
#define EXPORT_SECTION_FLAGS INFO_FLAGS
/* 
#define EXPORT_SECTION_NAME ".text"
#define EXPORT_SECTION_FLAGS TEXT_FLAGS
*/

static STRING *Exports = NULL;
static struct Section *directive_sec;
void AddExport(char *name)
{
    STRING *rvp = Exports, *newS;

    newS = (STRING *) nasm_malloc(sizeof(STRING));
    newS->len = strlen(name);
    newS->Next = NULL;
    newS->String = (char *)nasm_malloc(newS->len + 1);
    strcpy(newS->String, name);
    if (rvp == NULL) {
        int i;
        for (i = 0; i < nsects; i++)

            if (!strcmp(EXPORT_SECTION_NAME, sects[i]->name))
                break;
        if (i == nsects)
            directive_sec =
                sects[coff_make_section
                      (EXPORT_SECTION_NAME, EXPORT_SECTION_FLAGS)];
        else
            directive_sec = sects[i];
        Exports = newS;
    } else {
        while (rvp->Next) {
            if (!strcmp(rvp->String, name))
                return;
            rvp = rvp->Next;
        }
        rvp->Next = newS;
    }
}

void BuildExportTable(void)
{
    STRING *rvp = Exports, *next;
    uint8_t buf[256];
    int len;
    if (rvp == NULL)
        return;
    while (rvp) {
        len = sprintf((char *)buf, "-export:%s ", rvp->String);
        coff_sect_write(directive_sec, buf, len);
        rvp = rvp->Next;
    }

    next = Exports;
    while ((rvp = next)) {
        next = rvp->Next;
        nasm_free(rvp->String);
        nasm_free(rvp);
    }
    Exports = NULL;
}

static int coff_directives(char *directive, char *value, int pass)
{
    if (!strcmp(directive, "export")) {
        char *q, *name;

        if (pass == 2)
            return 1;           /* ignore in pass two */
        name = q = value;
        while (*q && !isspace(*q))
            q++;
        if (isspace(*q)) {
            *q++ = '\0';
            while (*q && isspace(*q))
                q++;
        }

        if (!*name) {
            error(ERR_NONFATAL, "`export' directive requires export name");
            return 1;
        }
        if (*q) {
            error(ERR_NONFATAL, "unrecognized export qualifier `%s'", q);
            return 1;
        }
        AddExport(name);
        return 1;
    }
    return 0;
}

static void coff_write(void)
{
    int32_t pos, sympos, vsize;
    int i;

    BuildExportTable();         /* fill in the .drectve section with -export's */
    /*
     * Work out how big the file will get. Calculate the start of
     * the `real' symbols at the same time.
     */
    pos = 0x14 + 0x28 * nsects;
    initsym = 3;                /* two for the file, one absolute */
    for (i = 0; i < nsects; i++) {
        if (sects[i]->data) {
            sects[i]->pos = pos;
            pos += sects[i]->len;
            sects[i]->relpos = pos;
            pos += 10 * sects[i]->nrelocs;
        } else
            sects[i]->pos = sects[i]->relpos = 0L;
        initsym += 2;           /* two for each section */
    }
    sympos = pos;

    /*
     * Output the COFF header.
     */
    if (win64)
        fwriteint16_t(0x8664, coffp);  /* MACHINE_x86-64 */
    else
        fwriteint16_t(0x014C, coffp);  /* MACHINE_i386 */
    fwriteint16_t(nsects, coffp); /* number of sections */
    fwriteint32_t(time(NULL), coffp);      /* time stamp */
    fwriteint32_t(sympos, coffp);
    fwriteint32_t(nsyms + initsym, coffp);
    fwriteint16_t(0, coffp);      /* no optional header */
    /* Flags: 32-bit, no line numbers. Win32 doesn't even bother with them. */
    fwriteint16_t((win32 | win64) ? 0 : 0x104, coffp);

    /*
     * Output the section headers.
     */
    vsize = 0L;
    for (i = 0; i < nsects; i++) {
        coff_section_header(sects[i]->name, vsize, sects[i]->len,
                            sects[i]->pos, sects[i]->relpos,
                            sects[i]->nrelocs, sects[i]->flags);
        vsize += sects[i]->len;
    }

    /*
     * Output the sections and their relocations.
     */
    for (i = 0; i < nsects; i++)
        if (sects[i]->data) {
            saa_fpwrite(sects[i]->data, coffp);
            coff_write_relocs(sects[i]);
        }

    /*
     * Output the symbol and string tables.
     */
    coff_write_symbols();
    fwriteint32_t(strslen + 4, coffp);     /* length includes length count */
    saa_fpwrite(strs, coffp);
}

static void coff_section_header(char *name, int32_t vsize,
                                int32_t datalen, int32_t datapos,
                                int32_t relpos, int nrelocs, int32_t flags)
{
    char padname[8];

    (void)vsize;

    memset(padname, 0, 8);
    strncpy(padname, name, 8);
    fwrite(padname, 8, 1, coffp);
    fwriteint32_t(0, coffp);	/* Virtual size field - set to 0 or vsize */
    fwriteint32_t(0L, coffp);      /* RVA/offset - we ignore */
    fwriteint32_t(datalen, coffp);
    fwriteint32_t(datapos, coffp);
    fwriteint32_t(relpos, coffp);
    fwriteint32_t(0L, coffp);      /* no line numbers - we don't do 'em */
    fwriteint16_t(nrelocs, coffp);
    fwriteint16_t(0, coffp);      /* again, no line numbers */
    fwriteint32_t(flags, coffp);
}

static void coff_write_relocs(struct Section *s)
{
    struct Reloc *r;

    for (r = s->head; r; r = r->next) {
        fwriteint32_t(r->address, coffp);
        fwriteint32_t(r->symbol + (r->symbase == REAL_SYMBOLS ? initsym :
                                r->symbase == ABS_SYMBOL ? initsym - 1 :
                                r->symbase == SECT_SYMBOLS ? 2 : 0),
                   coffp);
        /*
         * Strange: Microsoft's COFF documentation says 0x03 for an
         * absolute relocation, but both Visual C++ and DJGPP agree
         * that in fact it's 0x06. I'll use 0x06 until someone
         * argues. ***** UPDATE: PE/COFF Ver.8 docs confirm this -kkanios *****
         */
        if (win64)
            fwriteint16_t(r->relative ? 0x04 : r->size64 ? 0x01 : 0x02, coffp);
        else
            fwriteint16_t(r->relative ? 0x14 : 0x06, coffp);
    }
}

static void coff_symbol(char *name, int32_t strpos, int32_t value,
                        int section, int type, int aux)
{
    char padname[8];

    if (name) {
        memset(padname, 0, 8);
        strncpy(padname, name, 8);
        fwrite(padname, 8, 1, coffp);
    } else {
        fwriteint32_t(0L, coffp);
        fwriteint32_t(strpos, coffp);
    }
    fwriteint32_t(value, coffp);
    fwriteint16_t(section, coffp);
    fwriteint16_t(0, coffp);
    fputc(type, coffp);
    fputc(aux, coffp);
}

static void coff_write_symbols(void)
{
    char filename[18];
    uint32_t i;

    /*
     * The `.file' record, and the file name auxiliary record.
     */
    coff_symbol(".file", 0L, 0L, -2, 0x67, 1);
    memset(filename, 0, 18);
    strncpy(filename, coff_infile, 18);
    fwrite(filename, 18, 1, coffp);

    /*
     * The section records, with their auxiliaries.
     */
    memset(filename, 0, 18);    /* useful zeroed buffer */

    for (i = 0; i < nsects; i++) {
        coff_symbol(sects[i]->name, 0L, 0L, i + 1, 3, 1);
        fwriteint32_t(sects[i]->len, coffp);
        fwriteint16_t(sects[i]->nrelocs, coffp);
        fwrite(filename, 12, 1, coffp);
    }

    /*
     * The absolute symbol, for relative-to-absolute relocations.
     */
    coff_symbol(".absolut", 0L, 0L, -1, 3, 0);

    /*
     * The real symbols.
     */
    saa_rewind(syms);
    for (i = 0; i < nsyms; i++) {
        struct Symbol *sym = saa_rstruct(syms);
        coff_symbol(sym->strpos == -1 ? sym->name : NULL,
                    sym->strpos, sym->value, sym->section,
                    sym->is_global ? 2 : 3, 0);
    }
}

static int32_t coff_segbase(int32_t segment)
{
    return segment;
}

static void coff_std_filename(char *inname, char *outname, efunc error)
{
    strcpy(coff_infile, inname);
    standard_extension(inname, outname, ".o", error);
}

static void coff_win32_filename(char *inname, char *outname, efunc error)
{
    strcpy(coff_infile, inname);
    standard_extension(inname, outname, ".obj", error);
}

static const char *coff_stdmac[] = {
    "%define __SECT__ [section .text]",
    "%macro __NASM_CDecl__ 1",
    "%endmacro",
    "%imacro export 1+.nolist",
    "[export %1]",
    "%endmacro",
    NULL
};

static int coff_set_info(enum geninfo type, char **val)
{
    (void)type;
    (void)val;
    return 0;
}
#endif                          /* defined(OF_COFF) || defined(OF_WIN32) */

#ifdef OF_COFF

struct ofmt of_coff = {
    "COFF (i386) object files (e.g. DJGPP for DOS)",
    "coff",
    NULL,
    null_debug_arr,
    &null_debug_form,
    coff_stdmac,
    coff_std_init,
    coff_set_info,
    coff_out,
    coff_deflabel,
    coff_section_names,
    coff_segbase,
    coff_directives,
    coff_std_filename,
    coff_cleanup
};

#endif

#ifdef OF_WIN32

struct ofmt of_win32 = {
    "Microsoft Win32 (i386) object files",
    "win32",
    NULL,
    null_debug_arr,
    &null_debug_form,
    coff_stdmac,
    coff_win32_init,
    coff_set_info,
    coff_out,
    coff_deflabel,
    coff_section_names,
    coff_segbase,
    coff_directives,
    coff_win32_filename,
    coff_cleanup
};

#endif

#ifdef OF_WIN64

struct ofmt of_win64 = {
    "Microsoft Win64 (x86-64) object files",
    "win64",
    NULL,
    null_debug_arr,
    &null_debug_form,
    coff_stdmac,
    coff_win64_init,
    coff_set_info,
    coff_out,
    coff_deflabel,
    coff_section_names,
    coff_segbase,
    coff_directives,
    coff_win32_filename,
    coff_cleanup
};

#endif