ld.c

<B>Digital的Unix操作系统VAX 4.2源码</B>

		sp = xsym(i);
		switch (sp->n_type & (N_TYPE+N_EXT)) {

		case N_EXT+N_UNDF:
			if (arflag == 0)
				errlev |= 01;
			if ((arflag==0 || dflag) && sp->n_value==0) {
				if (sp==p_end || sp==p_etext || sp==p_edata)
					continue;
				if (nund==0)
					printf("Undefined:\n");
				nund++;
				printf("%s\n", sp->n_un.n_name);
			}
			continue;
		case N_EXT+N_ABS:
		default:
			continue;
		case N_EXT+N_TEXT:
			sp->n_value += torigin;
			continue;
		case N_EXT+N_DATA:
			sp->n_value += dorigin;
			continue;
		case N_EXT+N_BSS:
			sp->n_value += borigin;
			continue;
		case N_EXT+N_COMM:
			sp->n_type = (sp->n_type & N_STAB) | (N_EXT+N_BSS);
			sp->n_value += corigin;
			continue;
		}
	}
	if (sflag || xflag)
		ssize = 0;
	bsize += csize;
	nsym = ssize / (sizeof cursym);
	if (Aflag) {
		fixspec(p_etext,torigin);
		fixspec(p_edata,dorigin);
		fixspec(p_end,borigin);
	}
}

fixspec(sym,offset)
	struct nlist *sym;
	long offset;
{

	if(symx(sym) < symx(addsym) && sym!=0)
		sym->n_value += offset;
}

ldrsym(sp, val, type)
	register struct nlist *sp;
	long val;
{

	if (sp == 0)
		return;
	if ((sp->n_type != N_EXT+N_UNDF || sp->n_value) && !Aflag) {
		printf("%s: ", sp->n_un.n_name);
		error(0, "user attempt to redfine loader-defined symbol");
		return;
	}
	sp->n_type = type;
	sp->n_value = val;
}

off_t	wroff;
struct	biobuf toutb;

setupout()
{
	int bss;
	struct stat stbuf;
	extern char *sys_errlist[];
	extern int errno;

	ofilemode = 0777 & ~umask(0);
	biofd = creat(ofilename, 0666 & ofilemode);
	if (biofd < 0) {
		filname = ofilename;		/* kludge */
		archdr.ar_name[0] = 0;		/* kludge */
		error(1, sys_errlist[errno]);	/* kludge */
		/* NOT REACHED */
	}
	fstat(biofd, &stbuf);		/* suppose file exists, wrong*/
	if (stbuf.st_mode & 0111) {	/* mode, ld fails? */
		chmod(ofilename, stbuf.st_mode & 0666);
		ofilemode = stbuf.st_mode;
	}
	filhdr.a_magic = nflag ? NMAGIC : (zflag ? ZMAGIC : OMAGIC);
	filhdr.a_mode = (ex_mode == sys_v) ? A_SYSV : 
		((ex_mode == posix) ? A_POSIX : A_BSD);
	filhdr.a_text = nflag ? tsize :
	    round(tsize, zflag ? pagesize : sizeof (long));
	filhdr.a_data = zflag ? round(dsize, pagesize) : dsize;
	bss = bsize - (filhdr.a_data - dsize);
	if (bss < 0)
		bss = 0;
	filhdr.a_bss = bss;
	filhdr.a_trsize = trsize;
	filhdr.a_drsize = drsize;
	if (sflag) {
	    filhdr.a_syms = 0;
	} else {
	    filhdr.a_syms = ssize + (sizeof cursym)*symx(nextsym);
	    /* There are three extra nlist entries added at the beginning
	     * of the symbol table containing counts (see nsline, nfun)
	     * for dbx, if the program was linked "-lg".  (vjh)
	     */
	    if (gflag) {
	        filhdr.a_syms += (3 * sizeof(struct nlist));
	    }
	}
	if (entrypt) {
		if (entrypt->n_type!=N_EXT+N_TEXT)
			error(0, "entry point not in text");
		else
			filhdr.a_entry = entrypt->n_value;
	} else
		filhdr.a_entry = 0;
	filhdr.a_trsize = (rflag ? trsize:0);
	filhdr.a_drsize = (rflag ? drsize:0);
	tout = &toutb;
	bopen(tout, 0, stbuf.st_blksize);
	bwrite((char *)&filhdr, sizeof (filhdr), tout);
	if (zflag)
		bseek(tout, pagesize);
	wroff = N_TXTOFF(filhdr) + filhdr.a_text;
	outb(&dout, filhdr.a_data, stbuf.st_blksize);
	if (rflag) {
		outb(&trout, filhdr.a_trsize, stbuf.st_blksize);
		outb(&drout, filhdr.a_drsize, stbuf.st_blksize);
	}
	if (sflag==0 || xflag==0) {
		outb(&sout, filhdr.a_syms, stbuf.st_blksize);
		wroff += sizeof (offset);
		outb(&strout, 0, stbuf.st_blksize);
		if (gflag) {
		    outstabcnt();
		}
	}
}

/* Routine to output the number of functions, source lines, and
 * source files.  These records *must* be the first three records in
 * the symbol table, and are used by dbx in estimating the size of
 * some tables that it has to build.  This information is present
 * only if -lg was specified. (vjh)
 */
outstabcnt()
{
    struct nlist stabcnt;

    if (sflag || xflag) return;		/* 005 - vjh */

    stabcnt.n_type = N_NSYMS;
    stabcnt.n_un.n_name = 0;
    stabcnt.n_desc = 0;
    stabcnt.n_other = 0;
    stabcnt.n_value = nsol;

    /* This will be the first record in the symbol table. */
    bwrite(&stabcnt, sizeof(stabcnt), sout);

    stabcnt.n_value = nfun;

    /* This will be the second record in the symbol table. */
    bwrite(&stabcnt, sizeof(stabcnt), sout);

    stabcnt.n_value = nsline;

    /* This will be the third record in the symbol table. */
    bwrite(&stabcnt, sizeof(stabcnt), sout);
}

outb(bp, inc, bufsize)
	register struct biobuf **bp;
{

	*bp = (struct biobuf *)malloc(sizeof (struct biobuf));
	if (*bp == 0)
		error(1, "ran out of memory (outb)");
	bopen(*bp, wroff, bufsize);
	wroff += inc;
}

load2arg(acp)
char *acp;
{
	register char *cp;
	off_t loc;

	cp = acp;
	if (getfile(cp) == 0) {
		while (*cp)
			cp++;
		while (cp >= acp && *--cp != '/');
		mkfsym(++cp);
		load2(0L);
	} else {	/* scan archive members referenced */
		for (;;) {
			if (clibseg->li_used2 == clibseg->li_used) {
				if (clibseg->li_used < NROUT)
					error(1, "libseg botch");
				clibseg++;
			}
			loc = clibseg->li_first[clibseg->li_used2++];
			if (loc == -1)
				break;
			dseek(&text, loc, (long)sizeof(archdr));
			getarhdr();
			mkfsym(archdr.ar_name);
			load2(loc + (long)sizeof(archdr));
		}
	}
	close(infil);
}

load2(loc)
long loc;
{
	int size;
	register struct nlist *sp;
	register struct local *lp;
	register int symno, i;
	int type;

	readhdr(loc);
	if (!funding) {
		ctrel = torigin;
		cdrel += dorigin;
		cbrel += borigin;
	}
	/*
	 * Reread the symbol table, recording the numbering
	 * of symbols for fixing external references.
	 */
	for (i = 0; i < LHSIZ; i++)
		lochash[i] = 0;
	clocseg = locseg;
	clocseg->lo_used = 0;
	symno = -1;
	loc += N_TXTOFF(filhdr);
	dseek(&text, loc+filhdr.a_text+filhdr.a_data+
		filhdr.a_trsize+filhdr.a_drsize+filhdr.a_syms, sizeof(off_t));
	mget(&size, sizeof(size), &text);
	dseek(&text, loc+filhdr.a_text+filhdr.a_data+
		filhdr.a_trsize+filhdr.a_drsize+filhdr.a_syms+sizeof(off_t),
		size - sizeof(off_t));
	curstr = (char *)malloc(size);
	if (curstr == NULL)
		error(1, "out of space reading string table (pass 2)");
	mget(curstr+sizeof(off_t), size-sizeof(off_t), &text);
	dseek(&text, loc+filhdr.a_text+filhdr.a_data+
		filhdr.a_trsize+filhdr.a_drsize, filhdr.a_syms);
	while (text.size > 0) {
		symno++;
		mget((char *)&cursym, sizeof(struct nlist), &text);
		if (cursym.n_un.n_strx) {
			if (cursym.n_un.n_strx<sizeof(size) ||
			    cursym.n_un.n_strx>=size)
				error(1, "bad string table index (pass 2)");
			cursym.n_un.n_name = curstr + cursym.n_un.n_strx;
		}
/* inline expansion of symreloc() */
		switch (cursym.n_type & 017) {

		case N_TEXT:
		case N_EXT+N_TEXT:
			cursym.n_value += ctrel;
			break;
		case N_DATA:
		case N_EXT+N_DATA:
			cursym.n_value += cdrel;
			break;
		case N_BSS:
		case N_EXT+N_BSS:
			cursym.n_value += cbrel;
			break;
		case N_EXT+N_UNDF:
			break;
		default:
			if (cursym.n_type&N_EXT)
				cursym.n_type = N_EXT+N_ABS;
		}
/* end inline expansion of symreloc() */
		type = cursym.n_type;
		if (yflag && cursym.n_un.n_name)
			for (i = 0; i < yflag; i++)
				/* fast check for 2d character! */
				if (ytab[i][1] == cursym.n_un.n_name[1] &&
				    !strcmp(ytab[i], cursym.n_un.n_name)) {
					tracesym();
					break;
				}
		if ((type&N_EXT) == 0) {
			if (!sflag&&!xflag&&		/* SLR001 */
			    (!Xflag||type&N_STAB||cursym.n_un.n_name[0]!='L'))
				symwrite(&cursym, sout);
			continue;
		}
		if (funding)
			continue;
		if ((sp = *lookup()) == 0)
			error(1, "internal error: symbol not found");
		if (cursym.n_type == N_EXT+N_UNDF) {
			if (clocseg->lo_used == NSYMPR) {
				if (++clocseg == &locseg[NSEG])
					error(1, "local symbol overflow");
				clocseg->lo_used = 0;
			}
			if (clocseg->lo_first == 0) {
				clocseg->lo_first = (struct local *)
				    malloc(NSYMPR * sizeof (struct local));
				if (clocseg->lo_first == 0)
					error(1, "out of memory (clocseg)");
			}
			lp = &clocseg->lo_first[clocseg->lo_used++];
			lp->l_index = symno;
			lp->l_symbol = sp;
			lp->l_link = lochash[symno % LHSIZ];
			lochash[symno % LHSIZ] = lp;
			continue;
		}
		if (cursym.n_type & N_STAB)
			continue;
		if (cursym.n_type!=sp->n_type || cursym.n_value!=sp->n_value) {
			printf("%s: ", cursym.n_un.n_name);
			error(0, "multiply defined");
		}
	}
	if (funding)
		return;
	dseek(&text, loc, filhdr.a_text);
	dseek(&reloc, loc+filhdr.a_text+filhdr.a_data, filhdr.a_trsize);
	load2td(ctrel, torigin - textbase, tout, trout);
	dseek(&text, loc+filhdr.a_text, filhdr.a_data);
	dseek(&reloc, loc+filhdr.a_text+filhdr.a_data+filhdr.a_trsize,
	    filhdr.a_drsize);
	load2td(cdrel, dorigin - database, dout, drout);
	while (filhdr.a_data & (sizeof(long)-1)) {
		bputc(0, dout);
		filhdr.a_data++;
	}
	torigin += filhdr.a_text;
	dorigin += round(filhdr.a_data, sizeof (long));
	borigin += round(filhdr.a_bss, sizeof (long));
	free(curstr);
}

struct tynames {
	int	ty_value;
	char	*ty_name;
} tynames[] = {
	N_UNDF,	"undefined",
	N_ABS,	"absolute",
	N_TEXT,	"text",
	N_DATA,	"data",
	N_BSS,	"bss",
	N_COMM,	"common",
	0,	0,
};

tracesym()
{
	register struct tynames *tp;

	if (cursym.n_type & N_STAB)
		return;
	printf("%s", filname);
	if (archdr.ar_name[0])
		printf("(%s)", archdr.ar_name);
	printf(": ");
	if ((cursym.n_type&N_TYPE) == N_UNDF && cursym.n_value) {
		printf("definition of common %s size %d\n",
		    cursym.n_un.n_name, cursym.n_value);
		return;
	}
	for (tp = tynames; tp->ty_name; tp++)
		if (tp->ty_value == (cursym.n_type&N_TYPE))
			break;
	printf((cursym.n_type&N_TYPE) ? "definition of" : "reference to");
	if (cursym.n_type&N_EXT)
		printf(" external");
	if (tp->ty_name)
		printf(" %s", tp->ty_name);
	printf(" %s\n", cursym.n_un.n_name);
}

/*
 * This routine relocates the single text or data segment argument.
 * Offsets from external symbols are resolved by adding the value
 * of the external symbols.  Non-external reference are updated to account
 * for the relative motion of the segments (ctrel, cdrel, ...).  If
 * a relocation was pc-relative, then we update it to reflect the
 * change in the positioning of the segments by adding the displacement
 * of the referenced segment and subtracting the displacement of the
 * current segment (creloc).
 *
 * If we are saving the relocation information, then we increase
 * each relocation datum address by our base position in the new segment.
 */
load2td(creloc, position, b1, b2)
	long creloc, position;					/* DLB002 */
	struct biobuf *b1, *b2;
{
	register struct nlist *sp;
	register struct local *lp;
	long tw;
	register struct relocation_info *rp, *rpend;
	struct relocation_info *relp;
	char *codep;
	register char *cp;
	int relsz, codesz;

	relsz = reloc.size;
	relp = (struct relocation_info *)malloc(relsz);
	codesz = text.size;
	codep = (char *)malloc(codesz);
	if (relp == 0 || codep == 0)
		error(1, "out of memory (load2td)");
	mget((char *)relp, relsz, &reloc);
	rpend = &relp[relsz / sizeof (struct relocation_info)];
	mget(codep, codesz, &text);
	for (rp = relp; rp < rpend; rp++) {
		cp = codep + rp->r_address;
		/*
		 * Pick up previous value at location to be relocated.
		 */
		switch (rp->r_length) {

		case 0:		/* byte */
			tw = *cp;
			break;

		case 1:		/* word */
			tw = *(short *)cp;
			break;

		case 2:		/* long */
			tw = *(long *)cp;
			break;

		default:
			error(1, "load2td botch: bad length");
		}
		/*
		 * If relative to an external which is defined,
		 * resolve to a simpler kind of reference in the
		 * result file.  If the external is undefined, just
		 * convert the symbol number to the number of the
		 * symbol in the result file and leave it undefined.
		 */
		if (rp->r_extern) {
			/*
			 * Search the hash table which maps local
			 * symbol numbers to symbol tables entries
			 * in the new a.out file.
			 */
			lp = lochash[rp->r_symbolnum % LHSIZ];
			while (lp->l_index != rp->r_symbolnum) {
				lp = lp->l_link;
				if (lp == 0)
					error(1, "local symbol botch");
			}
			sp = lp->l_symbol;
			if (sp->n_type == N_EXT+N_UNDF)
				rp->r_symbolnum = nsym+symx(sp);
			else {
				rp->r_symbolnum = sp->n_type & N_TYPE;
				tw += sp->n_value;
				rp->r_extern = 0;
			}
		} else switch (rp->r_symbolnum & N_TYPE) {
		/*
		 * Relocation is relative to the loaded position
		 * of another segment.  Update by the change in position
		 * of that segment.
		 */
		case N_TEXT:
			tw += ctrel;
			break;
		case N_DATA:
			tw += cdrel;
			break;
		case N_BSS:
			tw += cbrel;
			break;
		case N_ABS:
			break;
		default:
			error(1, "relocation format botch (symbol type))");
		}
		/*
		 * Relocation is pc relative, so decrease the relocation
		 * by the amount the current segment is displaced.
		 * (E.g if we are a relative reference to a text location
		 * from data space, we added the increase in the text address
		 * above, and subtract the increase in our (data) address
		 * here, leaving the net change the relative change in the
		 * positioning of our text and data segments.)
		 */
		if (rp->r_pcrel)
			tw -= creloc;
		/*
		 * Put the value back in the segment,
		 * while checking for overflow.
		 */
		switch (rp->r_length) {

		case 0:		/* byte */
			if (tw < -128 || tw > 127)
				error(0, "byte displacement overflow");
			*cp = tw;
			break;
		case 1:		/* word */
			if (tw < -32768 || tw > 32767)
				error(0, "word displacement overflow");
			*(short *)cp = tw;
			break;
		case 2:		/* long */
			*(long *)cp = tw;
			break;
		}
		/*
		 * If we are saving relocation information,
		 * we must convert the address in the segment from
		 * the old .o file into an address in the segment in
		 * the new a.out, by adding the position of our
		 * segment in the new larger segment.
		 */
		if (rflag)
			rp->r_address += position;
	}
	bwrite(codep, codesz, b1);
	if (rflag)
		bwrite(relp, relsz, b2);
	free((char *)relp);
	free(codep);
}

finishout()
{
	register int i;
	int nsymt;

	if (sflag==0) {
		nsymt = symx(nextsym);
		for (i = 0; i < nsymt; i++)
			symwrite(xsym(i), sout);
		bwrite(&offset, sizeof offset, sout);
	}
	if (!ofilfnd) {
		unlink("a.out");
		if (link("l.out", "a.out") < 0)
			error(1, "cannot move l.out to a.out");
		ofilename = "a.out";
	}
	delarg = errlev;
	delexit();
}

mkfsym(s)
char *s;
{

	if (sflag || xflag)
		return;
	cursym.n_un.n_name = s;
	cursym.n_type = N_TEXT;