ld.c

unix v7是最后一个广泛发布的研究型UNIX版本

/*
 *  link editor
 */

#include <signal.h>
#include "sys/types.h"
#include "sys/stat.h"

/*	Layout of a.out file :
 *
 *	header of 8 words	magic number 405, 407, 410, 411
 *				text size	)
 *				data size	) in bytes but even
 *				bss size	)
 *				symbol table size
 *				entry point
 *				{unused}
 *				flag set if no relocation
 *
 *
 *	header:		0
 *	text:		16
 *	data:		16+textsize
 *	relocation:	16+textsize+datasize
 *	symbol table:	16+2*(textsize+datasize) or 16+textsize+datasize
 *
 */
#define TRUE	1
#define FALSE	0


#define	ARCMAGIC 0177545
#define OMAGIC	0405
#define	FMAGIC	0407
#define	NMAGIC	0410
#define	IMAGIC	0411

#define	EXTERN	040
#define	UNDEF	00
#define	ABS	01
#define	TEXT	02
#define	DATA	03
#define	BSS	04
#define	COMM	05	/* internal use only */

#define	RABS	00
#define	RTEXT	02
#define	RDATA	04
#define	RBSS	06
#define	REXT	010

#define NOVLY	16
#define	RELFLG	01
#define	NROUT	256
#define	NSYM	1103
#define	NSYMPR	1000

char	premeof[] = "Premature EOF";
char	goodnm[] = "__.SYMDEF";

/* table of contents stuff */
#define TABSZ	700
struct tab
{	char cname[8];
	long cloc;
} tab[TABSZ];
int tnum;


/* overlay management */
int	vindex;
struct overlay {
	int	argsav;
	int	symsav;
	struct liblist	*libsav;
	char	*vname;
	int	ctsav, cdsav, cbsav;
	int	offt, offd, offb, offs;
} vnodes[NOVLY];

/* input management */
struct page {
	int	nuser;
	int	bno;
	int	nibuf;
	int	buff[256];
} page[2];

struct {
	int	nuser;
	int	bno;
} fpage;

struct stream {
	int	*ptr;
	int	bno;
	int	nibuf;
	int	size;
	struct page	*pno;
};

struct stream text;
struct stream reloc;

struct {
	char	aname[14];
	long	atime;
	char	auid, agid;
	int	amode;
	long	asize;
} archdr;

struct {
	int	fmagic;
	int	tsize;
	int	dsize;
	int	bsize;
	int	ssize;
	int	entry;
	int	pad;
	int	relflg;
} filhdr;


/* one entry for each archive member referenced;
 * set in first pass; needs restoring for overlays
 */
struct liblist {
	long	loc;
};

struct liblist	liblist[NROUT];
struct liblist	*libp = liblist;


/* symbol management */
struct symbol {
	char	sname[8];
	char	stype;
	char	spare;
	int	svalue;
};

struct local {
	int locindex;		/* index to symbol in file */
	struct symbol *locsymbol;	/* ptr to symbol table */
};

struct symbol	cursym;			/* current symbol */
struct symbol	symtab[NSYM];		/* actual symbols */
struct symbol	**symhash[NSYM];	/* ptr to hash table entry */
struct symbol	*lastsym;		/* last symbol entered */
int	symindex;		/* next available symbol table entry */
struct symbol	*hshtab[NSYM+2];	/* hash table for symbols */
struct local	local[NSYMPR];

/* internal symbols */
struct symbol	*p_etext;
struct symbol	*p_edata;
struct symbol	*p_end;
struct symbol	*entrypt;

int	trace;
/* flags */
int	xflag;		/* discard local symbols */
int	Xflag;		/* discard locals starting with 'L' */
int	Sflag;		/* discard all except locals and globals*/
int	rflag;		/* preserve relocation bits, don't define common */
int	arflag;		/* original copy of rflag */
int	sflag;		/* discard all symbols */
int	nflag;		/* pure procedure */
int	Oflag;		/* set magic # to 0405 (overlay) */
int	dflag;		/* define common even with rflag */
int	iflag;		/* I/D space separated */
int	vflag;		/* overlays used */

int	ofilfnd;
char	*ofilename = "l.out";
int	infil;
char	*filname;

/* cumulative sizes set in pass 1 */
int	tsize;
int	dsize;
int	bsize;
int	ssize;

/* symbol relocation; both passes */
int	ctrel;
int	cdrel;
int	cbrel;

int	errlev;
int	delarg	= 4;
char	tfname[] = "/tmp/ldaXXXXX";


/* output management */
struct buf {
	int	fildes;
	int	nleft;
	int	*xnext;
	int	iobuf[256];
};
struct buf	toutb;
struct buf	doutb;
struct buf	troutb;
struct buf	droutb;
struct buf	soutb;

struct symbol	**lookup();
struct symbol	**slookup();
struct symbol	*lookloc();

delexit()
{
	unlink("l.out");
	if (delarg==0)
		chmod(ofilename, 0777 & ~umask(0));
	exit(delarg);
}

main(argc, argv)
char **argv;
{
	register int c, i; 
	int num;
	register char *ap, **p;
	int found; 
	int vscan; 
	char save;

	if (signal(SIGINT, SIG_IGN) != SIG_IGN)
		signal(SIGINT, delexit);
	if (signal(SIGTERM, SIG_IGN) != SIG_IGN)
		signal(SIGTERM, delexit);
	if (argc == 1)
		exit(4);
	p = argv+1;

	/* scan files once to find symdefs */
	for (c=1; c<argc; c++) {
		if (trace) printf("%s:\n", *p);
		filname = 0;
		ap = *p++;

		if (*ap == '-') {
			for (i=1; ap[i]; i++) {
			switch (ap[i]) {
			case 'o':
				if (++c >= argc)
					error(2, "Bad output file");
				ofilename = *p++;
				ofilfnd++;
				continue;

			case 'u':
			case 'e':
				if (++c >= argc)
					error(2, "Bad 'use' or 'entry'");
				enter(slookup(*p++));
				if (ap[i]=='e')
					entrypt = lastsym;
				continue;

			case 'v':
				if (++c >= argc)
					error(2, "-v: arg missing");
				vflag=TRUE;
				vscan = vindex; 
				found=FALSE;
				while (--vscan>=0 && found==FALSE)
					found = eq(vnodes[vscan].vname, *p);
				if (found) {
					endload(c, argv);
					restore(vscan);
				} else
					record(c, *p);
				p++;
				continue;

			case 'D':
				if (++c >= argc)
					error(2, "-D: arg missing");
				num = atoi(*p++);
				if (dsize>num)
					error(2, "-D: too small");
				dsize = num;
				continue;

			case 'l':
				save = ap[--i]; 
				ap[i]='-';
				load1arg(&ap[i]); 
				ap[i]=save;
				break;

			case 'x':
				xflag++;
				continue;

			case 'X':
				Xflag++;
				continue;

			case 'S':
				Sflag++; 
				continue;

			case 'r':
				rflag++;
				arflag++;
				continue;

			case 's':
				sflag++;
				xflag++;
				continue;

			case 'n':
				nflag++;
				continue;

			case 'd':
				dflag++;
				continue;

			case 'i':
				iflag++;
				continue;

			case 'O':
				Oflag++;
				continue;

			case 't':
				trace++;
				continue;

			default:
				error(2, "bad flag");
			} /*endsw*/
			break;
			} /*endfor*/
		} else
			load1arg(ap);
	}
	endload(argc, argv);
}

/* used after pass 1 */
int	nsym;
int	torigin;
int	dorigin;
int	borigin;

endload(argc, argv)
int argc; 
char **argv;
{
	register int c, i; 
	int dnum;
	register char *ap, **p;
	filname = 0;
	middle();
	setupout();
	p = argv+1;
	libp = liblist;
	for (c=1; c<argc; c++) {
		ap = *p++;
		if (trace) printf("%s:\n", ap);
		if (*ap == '-') {
			for (i=1; ap[i]; i++) {
			switch (ap[i]) {
			case 'D':
				for (dnum = atoi(*p); dorigin<dnum; dorigin += 2) {
					putw(0, &doutb);
					if (rflag)
						putw(0, &droutb);
				}
			case 'u':
			case 'e':
			case 'o':
			case 'v':
				++c; 
				++p;

			default:
				continue;

			case 'l':
				ap[--i]='-'; 
				load2arg(&ap[i]);
				break;
			} /*endsw*/
			break;
			} /*endfor*/
		} else
			load2arg(ap);
	}
	finishout();
}

record(c, nam)
int c; 
char *nam;
{
	register struct overlay *v;

	v = &vnodes[vindex++];
	v->argsav = c;
	v->symsav = symindex;
	v->libsav = libp;
	v->vname = nam;
	v->offt = tsize; 
	v->offd = dsize; 
	v->offb = bsize; 
	v->offs = ssize;
	v->ctsav = ctrel; 
	v->cdsav = cdrel; 
	v->cbsav = cbrel;
}

restore(vscan)
int vscan;
{
	register struct overlay *v;
	register int saved;

	v = &vnodes[vscan];
	vindex = vscan+1;
	libp = v->libsav;
	ctrel = v->ctsav; 
	cdrel = v->cdsav; 
	cbrel = v->cbsav;
	tsize = v->offt; 
	dsize = v->offd; 
	bsize = v->offb; 
	ssize = v->offs;
	saved = v->symsav;
	while (symindex>saved)
		*symhash[--symindex]=0;
}

/* scan file to find defined symbols */
load1arg(acp)
char *acp;
{
	register char *cp;
	long nloc;

	cp = acp;
	switch ( getfile(cp)) {
	case 0:
		load1(0, 0L);
		break;

	/* regular archive */
	case 1:
		nloc = 1;
		while ( step(nloc))
			nloc += (archdr.asize + sizeof(archdr) + 1) >> 1;
		break;

	/* table of contents */
	case 2:
		tnum = archdr.asize / sizeof(struct tab);
		if (tnum >= TABSZ) {
			error(2, "fast load buffer too small");
		}
		lseek(infil, (long)(sizeof(filhdr.fmagic)+sizeof(archdr)), 0);
		read(infil, (char *)tab, tnum * sizeof(struct tab));
		while (ldrand());
		libp->loc = -1;
		libp++;
		break;
	/* out of date table of contents */
	case 3:
		error(0, "out of date (warning)");
		for(nloc = 1+((archdr.asize+sizeof(archdr)+1) >> 1); step(nloc);
			nloc += (archdr.asize + sizeof(archdr) + 1) >> 1);
		break;
	}
	close(infil);
}

step(nloc)
long nloc;
{
	dseek(&text, nloc, sizeof archdr);
	if (text.size <= 0) {
		libp->loc = -1;
		libp++;
		return(0);
	}
	mget((int *)&archdr, sizeof archdr);
	if (load1(1, nloc + (sizeof archdr) / 2)) {
		libp->loc = nloc;
		libp++;
	}
	return(1);
}

ldrand()
{
	int i;
	struct symbol *sp, **pp;
	struct liblist *oldp = libp;
	for(i = 0; i<tnum; i++) {
		if ((pp = slookup(tab[i].cname)) == 0)
			continue;
		sp = *pp;
		if (sp->stype != EXTERN+UNDEF)
			continue;
		step(tab[i].cloc >> 1);
	}
	return(oldp != libp);
}

add(a,b,s)
int a, b;
char *s;
{
	long r;

	r = (long)(unsigned)a + (unsigned)b;
	if (r >= 0200000)
		error(1,s);
	return(r);
}


/* single file or archive member */
load1(libflg, loc)
long loc;
{
	register struct symbol *sp;
	int savindex;
	int ndef, nloc, type, mtype;

	readhdr(loc);
	ctrel = tsize;
	cdrel += dsize;
	cbrel += bsize;
	ndef = 0;
	nloc = sizeof cursym;
	savindex = symindex;
	if ((filhdr.relflg&RELFLG)==1) {
		error(1, "No relocation bits");
		return(0);
	}
	loc += (sizeof filhdr)/2 + filhdr.tsize + filhdr.dsize;
	dseek(&text, loc, filhdr.ssize);
	while (text.size > 0) {
		mget((int *)&cursym, sizeof cursym);
		type = cursym.stype;
		if (Sflag) {
			mtype = type&037;
			if (mtype==1 || mtype>4) {
				continue;
			}
		}
		if ((type&EXTERN)==0) {
			if (Xflag==0 || cursym.sname[0]!='L')
				nloc += sizeof cursym;
			continue;
		}
		symreloc();
		if (enter(lookup()))
			continue;
		if ((sp = lastsym)->stype != EXTERN+UNDEF)
			continue;
		if (cursym.stype == EXTERN+UNDEF) {
			if (cursym.svalue > sp->svalue)
				sp->svalue = cursym.svalue;
			continue;
		}
		if (sp->svalue != 0 && cursym.stype == EXTERN+TEXT)
			continue;
		ndef++;
		sp->stype = cursym.stype;
		sp->svalue = cursym.svalue;
	}
	if (libflg==0 || ndef) {
		tsize = add(tsize,filhdr.tsize,"text overflow");
		dsize = add(dsize,filhdr.dsize,"data overflow");
		bsize = add(bsize,filhdr.bsize,"bss overflow");
		ssize = add(ssize,nloc,"symbol table overflow");
		return(1);
	}
	/*
	 * No symbols defined by this library member.
	 * Rip out the hash table entries and reset the symbol table.
	 */
	while (symindex>savindex)
		*symhash[--symindex]=0;
	return(0);
}

middle()
{
	register struct symbol *sp, *symp;
	register t, csize;
	int nund, corigin;

	torigin=0; 
	dorigin=0; 
	borigin=0;

	p_etext = *slookup("_etext");
	p_edata = *slookup("_edata");
	p_end = *slookup("_end");
	/*
	 * If there are any undefined symbols, save the relocation bits.
	 */
	symp = &symtab[symindex];
	if (rflag==0) {
		for (sp = symtab; sp<symp; sp++)
			if (sp->stype==EXTERN+UNDEF && sp->svalue==0
				&& sp!=p_end && sp!=p_edata && sp!=p_etext) {
				rflag++;
				dflag = 0;
				break;
			}
	}
	if (rflag)
		nflag = sflag = iflag = Oflag = 0;
	/*
	 * Assign common locations.
	 */
	csize = 0;
	if (dflag || rflag==0) {
		ldrsym(p_etext, tsize, EXTERN+TEXT);
		ldrsym(p_edata, dsize, EXTERN+DATA);
		ldrsym(p_end, bsize, EXTERN+BSS);
		for (sp = symtab; sp<symp; sp++)
			if (sp->stype==EXTERN+UNDEF && (t = sp->svalue)!=0) {
				t = (t+1) & ~01;
				sp->svalue = csize;
				sp->stype = EXTERN+COMM;
				csize = add(csize, t, "bss overflow");
			}
	}
	/*
	 * Now set symbols to their final value
	 */
	if (nflag || iflag)
		tsize = (tsize + 077) & ~077;
	dorigin = tsize;
	if (nflag)