ld.c

Version 6 Unix 核心源代码 Version 6 Unix 核心源代码

char *acp;
{
	register char *cp;
	register struct liblist *lp;

	cp = acp;
	if (getfile(cp) == 0) {
		while (*cp)
			cp++;
		while (cp >= acp && *--cp != '/');
		mkfsym(++cp);
		load2(0, 0);
		return;
	}
	for (lp = libp; lp->bno != -1; lp++) {
		dseek(&text, lp->bno, lp->off, sizeof archdr);
		mget(&archdr, sizeof archdr);
		mkfsym(archdr.aname);
		load2(lp->bno, lp->off + (sizeof archdr) / 2);
	}
	libp = ++lp;
}

load2(bno, off)
{
	register struct symbol *sp;
	register int *lp, symno;

	readhdr(bno, off);
	ctrel = torigin;
	cdrel =+ dorigin;
	cbrel =+ borigin;
/*
 * Reread the symbol table, recording the numbering
 * of symbols for fixing external references.
 */
	lp = local;
	symno = -1;
	off =+ (sizeof filhdr)/2;
	dseek(&text, bno, off+filhdr.tsize+filhdr.dsize, filhdr.ssize);
	while (text.size > 0) {
		symno++;
		mget(&cursym, sizeof cursym);
		symreloc();
		if ((cursym.stype&EXTERN) == 0) {
			if (!sflag&&!xflag&&(!Xflag||cursym.sname[0]!='L'))
				mput(soutb, &cursym, sizeof cursym);
			continue;
		}
		if ((sp = *lookup()) == 0)
			error(1, "internal error: symbol not found");
		if (cursym.stype == EXTERN+UNDEF) {
			if (lp >= &local[NSYMPR])
				error(1, "Local symbol overflow");
			*lp++ = symno;
			*lp++ = sp;
			continue;
		}
		if (cursym.stype!=sp->stype || cursym.svalue!=sp->svalue) {
			printf("%.8s: ", cursym.sname);
			error(0, "Multiply defined");
		}
	}
	dseek(&text, bno, off, filhdr.tsize);
	dseek(&reloc, bno, off+(filhdr.tsize+filhdr.dsize)/2, filhdr.tsize);
	load2td(lp, ctrel, toutb, troutb);
	dseek(&text, bno, off+(filhdr.tsize/2), filhdr.dsize);
	dseek(&reloc, bno, off+filhdr.tsize+(filhdr.dsize/2), filhdr.dsize);
	load2td(lp, cdrel, doutb, droutb);
	torigin =+ filhdr.tsize;
	dorigin =+ filhdr.dsize;
	borigin =+ filhdr.bsize;
}

load2td(lp, creloc, b1, b2)
int *lp;
{
	register r, t;
	register struct symbol *sp;

	for (;;) {
	/*
	 * The pickup code is copied from "get" for speed.
	 */
		if (--text.size <= 0) {
			if (text.size < 0)
				break;
			text.size++;
			t = get(&text);
		} else if (--text.nibuf < 0) {
			text.nibuf++;
			text.size++;
			t = get(&text);
		} else
			t = *text.ptr++;
		if (--reloc.size <= 0) {
			if (reloc.size < 0)
				error(1, "Relocation error");
			reloc.size++;
			r = get(&reloc);
		} else if (--reloc.nibuf < 0) {
			reloc.nibuf++;
			reloc.size++;
			r = get(&reloc);
		} else
			r = *reloc.ptr++;
		switch (r&016) {

		case RTEXT:
			t =+ ctrel;
			break;

		case RDATA:
			t =+ cdrel;
			break;

		case RBSS:
			t =+ cbrel;
			break;

		case REXT:
			sp = lookloc(lp, r);
			if (sp->stype==EXTERN+UNDEF) {
				r = (r&01) + ((nsym+(sp-symtab))<<4) + REXT;
				break;
			}
			t =+ sp->svalue;
			r = (r&01) + ((sp->stype-(EXTERN+ABS))<<1);
			break;
		}
		if (r&01)
			t =- creloc;
		putw(t, b1);
		if (rflag)
			putw(r, b2);
	}
}

finishout()
{
	register n, *p;

	if (nflag||iflag) {
		n = torigin;
		while (n&077) {
			n =+ 2;
			putw(0, toutb);
			if (rflag)
				putw(0, troutb);
		}
	}
	copy(doutb, 'a');
	if (rflag) {
		copy(troutb, 'c');
		copy(droutb, 'd');
	}
	if (sflag==0) {
		if (xflag==0)
			copy(soutb, 'b');
		for (p=symtab; p < symp;)
			putw(*p++, toutb);
	}
	fflush(toutb);
	close(toutb[0]);
	unlink("a.out");
	link("l.out", "a.out");
	delarg = errlev;
	delexit();
}

delexit()
{
	register c;

	unlink("l.out");
	for (c = 'a'; c <= 'd'; c++) {
		tfname[6] = c;
		unlink(tfname);
	}
	if (delarg==0)
		chmod("a.out", 0777);
	exit(delarg);
}

copy(buf, c)
int *buf;
{
	register f, *p, n;

	fflush(buf);
	close(buf[0]);
	tfname[6] = c;
	f = open(tfname, 0);
	while ((n = read(f, doutb, 512)) > 1) {
		n =>> 1;
		p = doutb;
		do
			putw(*p++, toutb);
		while (--n);
	}
	close(f);
}

mkfsym(s)
char *s;
{

	if (sflag || xflag)
		return;
	cp8c(s, cursym.sname);
	cursym.stype = 037;
	cursym.svalue = torigin;
	mput(soutb, &cursym, sizeof cursym);
}

mget(aloc, an)
int *aloc;
{
	register *loc, n;
	register *p;

	n = an;
	n =>> 1;
	loc = aloc;
	if ((text.nibuf =- n) >= 0) {
		if ((text.size =- n) > 0) {
			p = text.ptr;
			do
				*loc++ = *p++;
			while (--n);
			text.ptr = p;
			return;
		} else
			text.size =+ n;
	}
	text.nibuf =+ n;
	do {
		*loc++ = get(&text);
	} while (--n);
}

mput(buf, aloc, an)
int *aloc;
{
	register *loc;
	register n;

	loc = aloc;
	n = an>>1;
	do {
		putw(*loc++, buf);
	} while (--n);
}

dseek(asp, ab, o, s)
{
	register struct stream *sp;
	register struct page *p;
	register b;
	int n;

	sp = asp;
	b = ab + ((o>>8) & 0377);
	o =& 0377;
	--sp->pno->nuser;
	if ((p = &page[0])->bno!=b && (p = &page[1])->bno!=b)
		if (p->nuser==0 || (p = &page[0])->nuser==0) {
			if (page[0].nuser==0 && page[1].nuser==0)
				if (page[0].bno < page[1].bno)
					p = &page[0];
			p->bno = b;
			seek(infil, b, 3);
			if ((n = read(infil, p->buff, 512)>>1) < 0)
				n = 0;
			p->nibuf = n;
		} else
			error(1, "No pages");
	++p->nuser;
	sp->bno = b;
	sp->pno = p;
	sp->ptr = p->buff + o;
	if (s != -1)
		sp->size = (s>>1) & 077777;
	if ((sp->nibuf = p->nibuf-o) <= 0)
		sp->size = 0;
}

get(asp)
struct stream *asp;
{
	register struct stream *sp;

	sp = asp;
	if (--sp->nibuf < 0) {
		dseek(sp, sp->bno+1, 0, -1);
		--sp->nibuf;
	}
	if (--sp->size <= 0) {
		if (sp->size < 0)
			error(1, premeof);
		++fpage.nuser;
		--sp->pno->nuser;
		sp->pno = &fpage;
	}
	return(*sp->ptr++);
}

getfile(acp)
char *acp;
{
	register char *cp;
	register c;

	cp = acp;
	archdr.aname[0] = '\0';
	if (cp[0]=='-' && cp[1]=='l') {
		if ((c = cp[2]) == '\0')
			c = 'a';
		cp = "/lib/lib?.a";
		cp[8] = c;
	}
	filname = cp;
	if ((infil = open(cp, 0)) < 0)
		error(1, "cannot open");
	page[0].bno = page[1].bno = -1;
	page[0].nuser = page[1].nuser = 0;
	text.pno = reloc.pno = &fpage;
	fpage.nuser = 2;
	dseek(&text, 0, 0, 2);
	if (text.size <= 0)
		error(1, premeof);
	return(get(&text) == ARCMAGIC);
}

struct symbol **lookup()
{
	int i;
	register struct symbol **hp;
	register char *cp, *cp1;

	i = 0;
	for (cp=cursym.sname; cp < &cursym.sname[8];)
		i = (i<<1) + *cp++;
	for (hp = &hshtab[(i&077777)%NSYM+2]; *hp!=0;) {
		cp1 = (*hp)->sname;
		for (cp=cursym.sname; cp < &cursym.sname[8];)
			if (*cp++ != *cp1++)
				goto no;
		break;
	    no:
		if (++hp >= &hshtab[NSYM+2])
			hp = hshtab;
	}
	return(hp);
}

struct symbol **slookup(s)
char *s;
{
	cp8c(s, cursym.sname);
	cursym.stype = EXTERN+UNDEF;
	cursym.svalue = 0;
	return(lookup());
}

enter()
{
	register struct symbol *sp;
	
	if ((sp=symp) >= &symtab[NSYM])
		error(1, "Symbol table overflow");
	cp8c(cursym.sname, sp->sname);
	sp->stype = cursym.stype;
	sp->svalue = cursym.svalue;
	symp++;
	return(sp);
}

symreloc()
{
	switch (cursym.stype) {

	case TEXT:
	case EXTERN+TEXT:
		cursym.svalue =+ ctrel;
		return;

	case DATA:
	case EXTERN+DATA:
		cursym.svalue =+ cdrel;
		return;

	case BSS:
	case EXTERN+BSS:
		cursym.svalue =+ cbrel;
		return;

	case EXTERN+UNDEF:
		return;
	}
	if (cursym.stype&EXTERN)
		cursym.stype = EXTERN+ABS;
}

error(n, s)
char *s;
{
	if (filname) {
		printf("%s", filname);
		if (archdr.aname[0])
			printf("(%.8s)", archdr.aname);
		printf(": ");
	}
	printf("%s\n", s);
	if (n)
		delexit();
	errlev = 2;
}

lookloc(alp, r)
{
	register int *clp, *lp;
	register sn;

	lp = alp;
	sn = (r>>4) & 07777;
	for (clp=local; clp<lp; clp =+ 2)
		if (clp[0] == sn)
			return(clp[1]);
	error(1, "Local symbol botch");
}

readhdr(bno, off)
{
	register st, sd;

	dseek(&text, bno, off, sizeof filhdr);
	mget(&filhdr, sizeof filhdr);
	if (filhdr.fmagic != FMAGIC)
		error(1, "Bad format");
	st = (filhdr.tsize+01) & ~01;
	filhdr.tsize = st;
	cdrel = -st;
	sd = (filhdr.dsize+01) & ~01;
	cbrel = - (st+sd);
	filhdr.bsize = (filhdr.bsize+01) & ~01;
}

cp8c(from, to)
char *from, *to;
{
	register char *f, *t, *te;

	f = from;
	t = to;
	te = t+8;
	while ((*t++ = *f++) && t<te);
	while (t<te)
		*t++ = 0;
}