outcoff.c

汇编编译器的最新版本的源码.买了自己动手写操作系统这本书的人一定要下

        char *q, *name;

        if (pass == 2)
            return 1;           /* ignore in pass two */
        name = q = value;
        while (*q && !nasm_isspace(*q))
            q++;
        if (nasm_isspace(*q)) {
            *q++ = '\0';
            while (*q && nasm_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;
    } else if (win32 && !strcmp(directive,"safeseh")) {
	static int sxseg=-1;
	int i;
	if (sxseg==-1)
	{   for (i = 0; i < nsects; i++)
		if (!strcmp(".sxdata",sects[i]->name))
		    break;
	    if (i == nsects)
		sxseg = coff_make_section(".sxdata",0x200);
	    else
		sxseg = i;
	}
	if (pass==2) {
	    uint32_t n;
	    saa_rewind(syms);
	    for (n = 0; n < nsyms; n++) {
		struct Symbol *sym = saa_rstruct(syms);
		bool equals;

		/* sym->strpos is biased by 4, because symbol
		 * table is prefixed with table length */
		if (sym->strpos >=4) {
		    char *name = nasm_malloc(sym->namlen+1);
		    saa_fread(strs, sym->strpos-4, name, sym->namlen);
		    name[sym->namlen] = '\0';
		    equals = !strcmp(value,name);
		    nasm_free(name);
		}
		else
		    equals = !strcmp(value,sym->name);

		if (equals) {
		    /* this value arithmetics effectively reflects
		     * initsym in coff_write(): 2 for file, 1 for
		     * .absolute and two per each section */
		    unsigned char value[4],*p=value;
		    WRITELONG(p,n + 2 + 1 + nsects*2);
		    coff_sect_write(sects[sxseg],value,4);
		    sym->type = 0x20;
		    break;
		}
	    }
	    if (n == nsyms) {
		error(ERR_NONFATAL,
		      "`safeseh' directive requires valid symbol");
	    }
	}
	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 */

    if (win32) {
	/* add default value for @feat.00, this allows to 'link /safeseh' */
	uint32_t n;

	saa_rewind(syms);
	for (n = 0; n < nsyms; n++) {
            struct Symbol *sym = saa_rstruct(syms);
	    if (sym->strpos == -1 && !strcmp("@feat.00",sym->name))
		break;
	}
	if (n == nsyms)
	    coff_deflabel("@feat.00",NO_SEG,1,0,NULL);
    }

    /*
     * 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);
	fwriteint16_t(r->type, coffp);
    }
}

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

    if (name) {
        memset(padname, 0, 8);
        strncpy(padname, name, 8);
        fwrite(padname, 8, 1, coffp);
    } else {
        fwriteint32_t(0, coffp);
        fwriteint32_t(strpos, coffp);
    }
    fwriteint32_t(value, coffp);
    fwriteint16_t(section, coffp);
    fwriteint16_t(type, coffp);
    fputc(storageclass, 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, 0, 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 < (uint32_t) nsects; i++) {
        coff_symbol(sects[i]->name, 0L, 0L, i + 1, 0, 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, 0, 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->type, 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);
}

extern macros_t coff_stdmac[];

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