ld.c

<B>Digital的Unix操作系统VAX 4.2源码</B>

/*
 * Copyright (c) 1980 Regents of the University of California.
 * All rights reserved.  The Berkeley software License Agreement
 * specifies the terms and conditions for redistribution.
 */

#ifndef lint
char copyright[] =
"@(#) Copyright (c) 1980 Regents of the University of California.\n\
 All rights reserved.\n";
#endif

#ifndef lint
static char *sccsid = "@(#)ld.c	4.4	ULTRIX		9/17/90";
#endif

/************************************************************************
 *									*
 *			Copyright (c) 1985, 1987, 1988 by		*
 *		Digital Equipment Corporation, Maynard, MA		*
 *			All rights reserved.				*
 *									*
 *   This software is furnished under a license and may be used and	*
 *   copied  only  in accordance with the terms of such license and	*
 *   with the  inclusion  of  the  above  copyright  notice.   This	*
 *   software  or  any  other copies thereof may not be provided or	*
 *   otherwise made available to any other person.  No title to and	*
 *   ownership of the software is hereby transferred.			*
 *									*
 *   This software is  derived  from  software  received  from  the	*
 *   University    of   California,   Berkeley,   and   from   Bell	*
 *   Laboratories.  Use, duplication, or disclosure is  subject  to	*
 *   restrictions  under  license  agreements  with  University  of	*
 *   California and with AT&T.						*
 *									*
 *   The information in this software is subject to change  without	*
 *   notice  and should not be construed as a commitment by Digital	*
 *   Equipment Corporation.						*
 *									*
 *   Digital assumes no responsibility for the use  or  reliability	*
 *   of its software on equipment which is not supplied by Digital.	*
 *									*
 ************************************************************************/

/************************************************************************
 *									*
 *			Modification History				*
 *									*
 * 014	Ken Lesniak, 05-Dec-89						*
 *	Added Bflag to tell ld to force BSS to start on a 512 byte	*
 *	(hardware page) boundary.					*
 *									*
 * 013	Mark Parenti, 08-Jun-88						*
 *	Changed signal handlers to void.				*
 *									*
 * 012	Jon Reeves, 24-Nov-87						*
 *	Add logic for execution mode (a_mode field).			*
 *									*
 * 011	Jon Reeves, 05-Aug-87						*
 *	Don't scribble on start of string table when the link includes	*
 *	a null file by name.						*
 *									*
 * 010	Jon Reeves, 01-Jun-87						*
 *	Incorporate 4.3 changes (mostly -L option)			*
 *									*
 * 009	Jon Reeves, 01-Jun-87						*
 *	Don't make -r output executable unless -d present.  Avoids	*
 *	user errors and increases X/OPEN compliance.			*
 *									*
 * 008  Victoria Holt, 01-Jul-86					*
 *	Now output 3 N_NSYMS records, using stabcnt.n_value field only,	*
 *	to avoid possible overflow.					*
 *									*
 * 007	Victoria Holt, 23-Dec-85					*
 *	Bug fix:  increment nfun counter for local routines (see	*
 *	vjh007 in source).						*
 *									*
 * 006  Robert Rodriguez, 15-Sep-85                                     *
 *	Add 4.3 speed ups (subsumed in 010)				*
 *									*
 * 005  Victoria Holt, 29-Aug-85					*
 *	Big fix:  ld output N_NSYMS record when -x switch was specified.*
 *	Harmless, but shouldn't have been there by definition of the	*
 *	switch.								*
 *									*
 * 004  Victoria Holt, 14-Jun-85					*
 *	ld will now count the number of functions, source lines, and	*
 *	source files; this information is output in a stab record of	*
 *	type N_NSYMS for use by dbx.  It must be the first stab entry	*
 *	in the symbol table.						*
 *									*
 *	David L Ballenger, 17-May-1985					*
 * 003	Fix for QPR-00078.  The -H option did not work properly.  The	*
 *	size argument was being used to increase the base address for	*
 *	the data section, but the textsize written to the a.out header	*
 *	was not increased accordingly.					*
 *									*
 * 002- David L Ballenger, 07-Sep-84					*
 *	Fix error with definiton of "position" formal parameter for	*
 *	load2td function.						*
 *									*
 *	Stephen Reilly, 15-Feb-84					*
 * 001- Fix some dereferencing of NULL pointers (partially subsumed in	*
 *	010).								*
 *									*
 ************************************************************************/

/*
 * ld - string table version for VAX
 */

#include <sys/param.h>
#include <signal.h>
#include <strings.h>
#include <stdio.h>
#include <ctype.h>
#include <ar.h>
#include <a.out.h>
#include <stab.h>
#include <ranlib.h>
#include <sys/stat.h>
#include <sys/file.h>

/*
 * Basic strategy:
 *
 * The loader takes a number of files and libraries as arguments.
 * A first pass examines each file in turn.  Normal files are
 * unconditionally loaded, and the (external) symbols they define and require
 * are noted in the symbol table.   Libraries are searched, and the
 * library members which define needed symbols are remembered
 * in a special data structure so they can be selected on the second
 * pass.  Symbols defined and required by library members are also
 * recorded.
 *
 * After the first pass, the loader knows the size of the basic text
 * data, and bss segments from the sum of the sizes of the modules which
 * were required.  It has computed, for each ``common'' symbol, the
 * maximum size of any reference to it, and these symbols are then assigned
 * storage locations after their sizes are appropriately rounded.
 * The loader now knows all sizes for the eventual output file, and
 * can determine the final locations of external symbols before it
 * begins a second pass.
 *
 * On the second pass each normal file and required library member
 * is processed again.  The symbol table for each such file is
 * reread and relevant parts of it are placed in the output.  The offsets
 * in the local symbol table for externally defined symbols are recorded
 * since relocation information refers to symbols in this way.
 * Armed with all necessary information, the text and data segments
 * are relocated and the result is placed in the output file, which
 * is pasted together, ``in place'', by writing to it in several
 * different places concurrently.
 */

/*
 * Internal data structures
 *
 * All internal data structures are segmented and dynamically extended.
 * The basic structures hold 1103 (NSYM) symbols, ~~200 (NROUT)
 * referenced library members, and 100 (NSYMPR) private (local) symbols
 * per object module.  For large programs and/or modules, these structures
 * expand to be up to 40 (NSEG) times as large as this as necessary.
 */
#define	NSEG	40		/* Number of segments, each data structure */
#define	NSYM	1103		/* Number of symbols per segment */
#define	NROUT	250		/* Number of library references per segment */
#define	NSYMPR	100		/* Number of private symbols per segment */

/*
 * Structure describing each symbol table segment.
 * Each segment has its own hash table.  We record the first
 * address in and first address beyond both the symbol and hash
 * tables, for use in the routine symx and the lookup routine respectively.
 * The symfree routine also understands this structure well as it used
 * to back out symbols from modules we decide that we don't need in pass 1.
 *
 * Csymseg points to the current symbol table segment;
 * csymseg->sy_first[csymseg->sy_used] is the next symbol slot to be allocated,
 * (unless csymseg->sy_used == NSYM in which case we will allocate another
 * symbol table segment first.)
 */
struct	symseg {
	struct	nlist *sy_first;	/* base of this alloc'ed segment */
	struct	nlist *sy_last;		/* end of this segment, for n_strx */
	int	sy_used;		/* symbols used in this seg */
	struct	nlist **sy_hfirst;	/* base of hash table, this seg */
	struct	nlist **sy_hlast;	/* end of hash table, this seg */
} symseg[NSEG], *csymseg;

/*
 * The lookup routine uses quadratic rehash.  Since a quadratic rehash
 * only probes 1/2 of the buckets in the table, and since the hash
 * table is segmented the same way the symbol table is, we make the
 * hash table have twice as many buckets as there are symbol table slots
 * in the segment.  This guarantees that the quadratic rehash will never
 * fail to find an empty bucket if the segment is not full and the
 * symbol is not there.
 */
#define	HSIZE	(NSYM*2)

/*
 * Xsym converts symbol table indices (ala x) into symbol table pointers.
 * Symx (harder, but never used in loops) inverts pointers into the symbol
 * table into indices using the symseg[] structure.
 */
#define	xsym(x)	(symseg[(x)/NSYM].sy_first+((x)%NSYM))
/* symx() is a function, defined below */

struct	nlist cursym;		/* current symbol */
struct	nlist *lastsym;		/* last symbol entered */
struct	nlist *nextsym;		/* next available symbol table entry */
struct	nlist *addsym;		/* first sym defined during incr load */
int	nsym;			/* pass2: number of local symbols in a.out */
/* nsym + symx(nextsym) is the symbol table size during pass2 */

struct	nlist **lookup(), **slookup();
struct	nlist *p_etext, *p_edata, *p_end, *entrypt;

/*
 * Definitions of segmentation for library member table.
 * For each library we encounter on pass 1 we record pointers to all
 * members which we will load on pass 2.  These are recorded as offsets
 * into the archive in the library member table.  Libraries are
 * separated in the table by the special offset value -1.
 */
off_t	li_init[NROUT];
struct	libseg {
	off_t	*li_first;
	int	li_used;
	int	li_used2;
} libseg[NSEG] = {
	li_init, 0, 0,
}, *clibseg = libseg;

/*
 * In processing each module on pass 2 we must relocate references
 * relative to external symbols.  These references are recorded
 * in the relocation information as relative to local symbol numbers
 * assigned to the external symbols when the module was created.
 * Thus before relocating the module in pass 2 we create a table
 * which maps these internal numbers to symbol table entries.
 * A hash table is constructed, based on the local symbol table indices,
 * for quick lookup of these symbols.
 */
#define	LHSIZ	31
struct	local {
	int	l_index;		/* index to symbol in file */
	struct	nlist *l_symbol;	/* ptr to symbol table */
	struct	local *l_link;		/* hash link */
} *lochash[LHSIZ], lhinit[NSYMPR];
struct	locseg {
	struct	local *lo_first;
	int	lo_used;
} locseg[NSEG] = {
	lhinit, 0
}, *clocseg;

/*
 * Libraries are typically built with a table of contents,
 * which is the first member of a library with special file
 * name __.SYMDEF and contains a list of symbol names
 * and with each symbol the offset of the library member which defines
 * it.  The loader uses this table to quickly tell which library members
 * are (potentially) useful.  The alternative, examining the symbol
 * table of each library member, is painfully slow for large archives.
 *
 * See <ranlib.h> for the definition of the ranlib structure and an
 * explanation of the __.SYMDEF file format.
 */
int	tnum;		/* number of symbols in table of contents */
int	ssiz;		/* size of string table for table of contents */
struct	ranlib *tab;	/* the table of contents (dynamically allocated) */
char	*tabstr;	/* string table for table of contents */

/*
 * We open each input file or library only once, but in pass2 we
 * (historically) read from such a file at 2 different places at the
 * same time.  These structures are remnants from those days,
 * and now serve only to catch ``Premature EOF''.
 * In order to make I/O more efficient, we provide routines which
 * use the optimal block size returned by stat().
 */
#define BLKSIZE 1024
typedef struct {
	short	*fakeptr;
	int	bno;
	int	nibuf;
	int	nuser;
	char	*buff;
	int	bufsize;
} PAGE;

PAGE	page[2];
int	p_blksize;
int	p_blkshift;
int	p_blkmask;

struct {
	short	*fakeptr;
	int	bno;
	int	nibuf;
	int	nuser;
} fpage;

typedef struct {
	char	*ptr;
	int	bno;
	int	nibuf;
	long	size;
	long	pos;
	PAGE	*pno;
} STREAM;

STREAM	text;
STREAM	reloc;

/*
 * Header from the a.out and the archive it is from (if any).
 */
struct	exec filhdr;
struct	ar_hdr archdr;
#define	OARMAG 0177545

/*
 * Options.
 */
int	trace;
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	Mflag;		/* print rudimentary load map */
int	nflag;		/* pure procedure */
int	dflag;		/* define common even with rflag */
int	zflag;		/* demand paged  */
long	hsize;		/* size of hole at beginning of data to be squashed */
int	Bflag;		/* set if want 512 byte alignment on BSS */
int	Aflag;		/* doing incremental load */
int	Nflag;		/* want impure a.out */
int	funding;	/* reading fundamental file for incremental load */
int	yflag;		/* number of symbols to be traced */
int	gflag;		/* link for debugging */
char	**ytab;		/* the symbols */
enum	Mode {
	sys_v, posix, bsd}
	ex_mode = bsd;	/* 012 - execution mode; changed by -Y/PROG_ENV */

/*
 * These are the cumulative sizes, set in pass 1, which
 * appear in the a.out header when the loader is finished.
 */
off_t	tsize, dsize, bsize, trsize, drsize, ssize;

/* Number of functions (estimate), number of source lines, and
 * number of source files.  This information is provided for dbx.
 * and is used when gflag is true (when linking -lg). (vjh)
 */
unsigned long nsline;
unsigned long nfun;
unsigned long nsol;

/*
 * Symbol relocation: c?rel is a scale factor which is
 * added to an old relocation to convert it to new units;
 * i.e. it is the difference between segment origins.
 * (Thus if we are loading from a data segment which began at location
 * 4 in a .o file into an a.out where it will be loaded starting at
 * 1024, cdrel will be 1020.)
 */
long	ctrel, cdrel, cbrel;

/*
 * Textbase is the start address of all text, 0 unless given by -T.
 * Database is the base of all data, computed before and used during pass2.
 */
long	textbase, database;

/*
 * The base addresses for the loaded text, data and bss from the
 * current module during pass2 are given by torigin, dorigin and borigin.
 */
long	torigin, dorigin, borigin;

/*
 * Errlev is nonzero when errors have occured.
 * Delarg is an implicit argument to the routine delexit
 * which is called on error.  We do ``delarg = errlev'' before normal
 * exits, and only if delarg is 0 (i.e. errlev was 0) do we make the
 * result file executable.
 */
int	errlev;
int	delarg	= 4;

/*
 * The biobuf structure and associated routines are used to write
 * into one file at several places concurrently.  Calling bopen
 * with a biobuf structure sets it up to write ``biofd'' starting
 * at the specified offset.  You can then use ``bwrite'' and/or ``bputc''
 * to stuff characters in the stream, much like ``fwrite'' and ``fputc''.
 * Calling bflush drains all the buffers and MUST be done before exit.
 */
struct	biobuf {
	short	b_nleft;		/* Number free spaces left in b_buf */
/* Initialize to be less than b_bufsize initially, to boundary align in file */
	char	*b_ptr;			/* Next place to stuff characters */
	char	*b_buf;			/* Pointer to the buffer */
	int	b_bufsize;		/* Size of the buffer */
	off_t	b_off;			/* Current file offset */
	struct	biobuf *b_link;		/* Link in chain for bflush() */
} *biobufs;
#define	bputc(c,b) ((b)->b_nleft ? (--(b)->b_nleft, *(b)->b_ptr++ = (c)) \
		       : bflushc(b, c))
int	biofd;
off_t	boffset;
struct	biobuf *tout, *dout, *trout, *drout, *sout, *strout;

/*
 * Offset is the current offset in the string file.
 * Its initial value reflects the fact that we will
 * eventually stuff the size of the string table at the
 * beginning of the string table (i.e. offset itself!).
 */
off_t	offset = sizeof (off_t);

int	ofilfnd;		/* -o given; otherwise move l.out to a.out */
char	*ofilename = "l.out";
int	ofilemode;		/* respect umask even for unsucessful ld's */
int	infil;			/* current input file descriptor */
char	*filname;		/* and its name */

#define	NDIRS	25
#define NDEFDIRS 3		/* number of default directories in dirs[] */
char	*dirs[NDIRS];		/* directories for library search */
int	ndir;			/* number of directories */

/*
 * Base of the string table of the current module (pass1 and pass2).
 */
char	*curstr;

/*
 * System software page size, as returned by getpagesize.
 */
int	pagesize;

char 	get();
void	delexit();
char	*savestr();
char	*malloc();
char	*getenv();

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

	if (signal(SIGINT, SIG_IGN) != SIG_IGN) {
		signal(SIGINT, delexit);
		signal(SIGTERM, delexit);
	}
	if (argc == 1)
		exit(4);
	pagesize = getpagesize();

	if ( strcmp("SYSTEM_FIVE",pep=getenv("PROG_ENV")) == 0)
		ex_mode = sys_v;
	else if ( strcmp("POSIX",pep) == 0)
		ex_mode = posix;
	else if ( strcmp("BSD",pep) == 0)
		ex_mode = bsd;

	/* 
	 * Pull out search directories.
	 */
	for (c = 1; c < argc; c++) {
		ap = argv[c];
		if (ap[0] == '-' && ap[1] == 'L') {
			if (ap[2] == 0)
				error(1, "-L: pathname missing");
			if (ndir >= NDIRS - NDEFDIRS)
				error(1, "-L: too many directories");
			dirs[ndir++] = &ap[2];
		}
	}
	/* add default search directories */
	dirs[ndir++] = "/lib";
	dirs[ndir++] = "/usr/lib";
	dirs[ndir++] = "/usr/local/lib";

	p = argv+1;
	/*
	 * Scan files once to find where symbols are defined.
	 */
	for (c=1; c<argc; c++) {
		if (trace)
			printf("%s:\n", *p);
		filname = 0;
		ap = *p++;
		if (*ap != '-') {
			load1arg(ap);
			continue;
		}
		for (i=1; ap[i]; i++) switch (ap[i]) {

		case 'o':
			if (++c >= argc)
				error(1, "-o where?");
			ofilename = *p++;
			ofilfnd++;
			continue;
		case 'u':
		case 'e':
			if (++c >= argc)
				error(1, "-u or -e: arg missing");
			enter(slookup(*p++));
			if (ap[i]=='e')
				entrypt = lastsym;
			continue;
		case 'H':
			if (++c >= argc)
				error(1, "-H: arg missing");
			if (tsize!=0)
				error(1, "-H: too late, some text already loaded");
			hsize = atoi(*p++);
			continue;
		case 'B':
			Bflag++;
			continue;
		case 'A':
			if (++c >= argc)
				error(1, "-A: arg missing");
			if (Aflag) 
				error(1, "-A: only one base file allowed");
			Aflag = 1;
			nflag = 0;
			funding = 1;
			load1arg(*p++);
			trsize = drsize = tsize = dsize = bsize = 0;
			ctrel = cdrel = cbrel = 0;
			funding = 0;
			addsym = nextsym;
			continue;
		case 'D':
			if (++c >= argc)
				error(1, "-D: arg missing");
			num = htoi(*p++);
			if (dsize > num)
				error(1, "-D: too small");
			dsize = num;
			continue;
		case 'T':
			if (++c >= argc)
				error(1, "-T: arg missing");
			if (tsize!=0)
				error(1, "-T: too late, some text already loaded");
			textbase = htoi(*p++);
			continue;
		case 'l':
			save = ap[--i]; 
			ap[i]='-';
			load1arg(&ap[i]); 
			ap[i]=save;
			goto next;
		case 'M':
			Mflag++;
			continue;