freebsd/libexec/rtld-aout/rtld.c

/*
 * Copyright (c) 1993 Paul Kranenburg
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by Paul Kranenburg.
 * 4. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * $FreeBSD$
 */

#include <sys/param.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/file.h>
#include <sys/time.h>
#include <sys/resource.h>
#include <sys/errno.h>
#include <sys/mman.h>
#ifndef MAP_COPY
#define MAP_COPY	MAP_PRIVATE
#endif
#include <dlfcn.h>
#include <err.h>
#include <fcntl.h>
#include <a.out.h>
#include <paths.h>
#include <stab.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <stdarg.h>

#include <link.h>

#include "md.h"
#include "shlib.h"
#include "support.h"
#include "dynamic.h"

#ifndef MAP_ANON
#define MAP_ANON	0
#define anon_open() do {					\
	if ((anon_fd = open(_PATH_DEVZERO, O_RDWR, 0)) == -1)	\
		err("open: %s", _PATH_DEVZERO);			\
} while (0)
#define anon_close() do {	\
	(void)close(anon_fd);	\
	anon_fd = -1;		\
} while (0)
#else
#define anon_open()
#define anon_close()
#endif

/*
 * Structure for building a list of shared objects.
 */
struct so_list {
	struct so_map	*sol_map;	/* Link map for shared object */
	struct so_list	*sol_next;	/* Next entry in the list */
};

/*
 * Loader private data, hung off <so_map>->som_spd
 */
struct somap_private {
	int		spd_version;
	struct so_map	*spd_parent;
	struct so_list	*spd_children;
	struct so_map	*spd_prev;
	dev_t		spd_dev;
	ino_t		spd_ino;
	int		spd_refcount;
	int		spd_flags;
#define RTLD_MAIN	0x01
#define RTLD_RTLD	0x02
#define RTLD_DL		0x04
#define RTLD_INIT	0x08
	unsigned long	a_text;    /* text size, if known     */
	unsigned long	a_data;    /* initialized data size   */
	unsigned long	a_bss;     /* uninitialized data size */

#ifdef SUN_COMPAT
	long		spd_offset;	/* Correction for Sun main programs */
#endif
};

#define LM_PRIVATE(smp)	((struct somap_private *)(smp)->som_spd)

#ifdef SUN_COMPAT
#define LM_OFFSET(smp)	(LM_PRIVATE(smp)->spd_offset)
#else
#define LM_OFFSET(smp)	(0)
#endif

/* Base address for section_dispatch_table entries */
#define LM_LDBASE(smp)	(smp->som_addr + LM_OFFSET(smp))

/* Start of text segment */
#define LM_TXTADDR(smp)	(smp->som_addr == (caddr_t)0 ? PAGSIZ : 0)

/* Start of run-time relocation_info */
#define LM_REL(smp)	((struct relocation_info *) \
	(smp->som_addr + LM_OFFSET(smp) + LD_REL((smp)->som_dynamic)))

/* Start of symbols */
#define LM_SYMBOL(smp, i)	((struct nzlist *) \
	(smp->som_addr + LM_OFFSET(smp) + LD_SYMBOL((smp)->som_dynamic) + \
		i * (LD_VERSION_NZLIST_P(smp->som_dynamic->d_version) ? \
			sizeof(struct nzlist) : sizeof(struct nlist))))

/* Start of hash table */
#define LM_HASH(smp)	((struct rrs_hash *) \
	((smp)->som_addr + LM_OFFSET(smp) + LD_HASH((smp)->som_dynamic)))

/* Start of strings */
#define LM_STRINGS(smp)	((char *) \
	((smp)->som_addr + LM_OFFSET(smp) + LD_STRINGS((smp)->som_dynamic)))

/* Start of search paths */
#define LM_PATHS(smp)	((char *) \
	((smp)->som_addr + LM_OFFSET(smp) + LD_PATHS((smp)->som_dynamic)))

/* End of text */
#define LM_ETEXT(smp)	((char *) \
	((smp)->som_addr + LM_TXTADDR(smp) + LD_TEXTSZ((smp)->som_dynamic)))

/* Needed shared objects */
#define LM_NEED(smp)	((struct sod *) \
	((smp)->som_addr + LM_TXTADDR(smp) + LD_NEED((smp)->som_dynamic)))

/* PLT is in data segment, so don't use LM_OFFSET here */
#define LM_PLT(smp)	((jmpslot_t *) \
	((smp)->som_addr + LD_PLT((smp)->som_dynamic)))

/* Parent of link map */
#define LM_PARENT(smp)	(LM_PRIVATE(smp)->spd_parent)

#ifndef RELOC_EXTERN_P
#define RELOC_EXTERN_P(s) ((s)->r_extern)
#endif

#ifndef RELOC_SYMBOL
#define RELOC_SYMBOL(s) ((s)->r_symbolnum)
#endif

#ifndef RELOC_PCREL_P
#define RELOC_PCREL_P(s) ((s)->r_pcrel)
#endif

#define END_SYM		"_end"

static char		__main_progname[] = "main";
static char		*main_progname = __main_progname;
static char		us[] = "/usr/libexec/ld.so";

char			**environ;
char			*__progname;
int			errno;

static uid_t		uid, euid;
static gid_t		gid, egid;
static int		careful;
static int		anon_fd = -1;

static char		*ld_bind_now;
static char		*ld_ignore_missing_objects;
static char		*ld_library_path;
static char		*ld_preload;
static char		*ld_tracing;
static char		*ld_suppress_warnings;
static char		*ld_warn_non_pure_code;

struct so_map		*link_map_head;
struct so_map		*link_map_tail;
struct rt_symbol	*rt_symbol_head;

static void		*__dlopen __P((const char *, int));
static int		__dlclose __P((void *));
static void		*__dlsym __P((void *, const char *));
static const char	*__dlerror __P((void));
static void		__dlexit __P((void));
static void		*__dlsym3 __P((void *, const char *, void *));
static int		__dladdr __P((const void *, Dl_info *));

static struct ld_entry	ld_entry = {
	__dlopen, __dlclose, __dlsym, __dlerror, __dlexit, __dlsym3, __dladdr
};

       void		xprintf __P((char *, ...));
static struct so_map	*map_object __P((	const char *,
						struct sod *,
						struct so_map *));
static int		map_preload __P((void));
static int		map_sods __P((struct so_map *));
static int		reloc_dag __P((struct so_map *, int));
static void		unmap_object __P((struct so_map	*, int));
static struct so_map	*alloc_link_map __P((	const char *, struct sod *,
						struct so_map *, caddr_t,
						struct _dynamic *));
static void		init_link_map __P((	struct so_map *,
						struct somap_private *,
						const char *, struct sod *,
						struct so_map *, caddr_t,
						struct _dynamic *));
static void		free_link_map __P((struct so_map *));
static inline int	check_text_reloc __P((	struct relocation_info *,
						struct so_map *,
						caddr_t));
static int		reloc_map __P((struct so_map *, int));
static void		reloc_copy __P((struct so_map *));
static void		init_dag __P((struct so_map *));
static void		init_sods __P((struct so_list *));
static void		init_internal_malloc __P((void));
static void		init_external_malloc __P((void));
static int		call_map __P((struct so_map *, char *));
static char		*findhint __P((char *, int, int *));
static char		*rtfindlib __P((char *, int, int, int));
static char		*rtfindfile __P((const char *));
void			binder_entry __P((void));
long			binder __P((jmpslot_t *));
static struct nzlist	*lookup __P((char *, struct so_map **, int));
static inline struct rt_symbol	*lookup_rts __P((char *, unsigned long));
static struct nzlist	*lookup_in_obj __P((char *, unsigned long,
    struct so_map *, int));
static struct rt_symbol	*enter_rts __P((char *, unsigned long, long, int,
    caddr_t, long, struct so_map *));
static void		*sym_addr __P((char *));
static struct nzlist *	lookup_errno_hack(char *, struct so_map	**, int);
static void		die __P((void));
static void		generror __P((char *, ...));
static int		maphints __P((void));
static void		unmaphints __P((void));
static void		ld_trace __P((struct so_map *));
static void		rt_readenv __P((void));
static int		hinthash __P((char *, int));
int			rtld __P((int, struct crt_ldso *, struct _dynamic *));

/*
 * Compute a hash value for symbol tables.  Don't change this -- the
 * algorithm is dictated by the way the linker builds the symbol
 * tables in the shared objects.
 */
static inline unsigned long
sym_hash(s)
	const char	*s;
{
	unsigned long	 h;

	h = 0;
	while (*s != '\0')
		h = (h << 1) + *s++;
	return h & 0x7fffffffUL;
}

static inline int
strcmp (register const char *s1, register const char *s2)
{
	while (*s1 == *s2++)
		if (*s1++ == 0)
			return (0);
	return (*(unsigned char *)s1 - *(unsigned char *)--s2);
}

#include "md-static-funcs.c"

/*
 * Called from assembler stub that has set up crtp (passed from crt0)
 * and dp (our __DYNAMIC).
 */
int
rtld(version, crtp, dp)
int			version;
struct crt_ldso		*crtp;
struct _dynamic		*dp;
{
	struct relocation_info	*reloc;
	struct relocation_info	*reloc_limit;	/* End+1 of relocation */
	struct so_debug		*ddp;
	struct so_map		*main_map;
	struct so_map		*smp;
	char			*add_paths;
	char			*main_path;

	/* Check version */
	if (version != CRT_VERSION_BSD_2 &&
	    version != CRT_VERSION_BSD_3 &&
	    version != CRT_VERSION_BSD_4 &&
	    version != CRT_VERSION_BSD_5 &&
	    version != CRT_VERSION_SUN)
		return -1;

	/* Fixup __DYNAMIC structure */
	(long)dp->d_un.d_sdt += crtp->crt_ba;

	/* Relocate ourselves */
	reloc = (struct relocation_info *) (LD_REL(dp) + crtp->crt_ba);
	reloc_limit =
		(struct relocation_info *) ((char *) reloc + LD_RELSZ(dp));
	while(reloc < reloc_limit) {
		/*
		 * Objects linked with "-Bsymbolic" (in particular, ld.so
		 * itself) can end up having unused relocation entries at
		 * the end.  These can be detected by the fact that they
		 * have an address of 0.
		 */
		if(reloc->r_address == 0)	/* We're done */
		    break;
		md_relocate_simple(reloc, crtp->crt_ba,
			reloc->r_address + crtp->crt_ba);
		++reloc;
	}

	if (version >= CRT_VERSION_BSD_4)
		__progname = crtp->crt_ldso;
	if (version >= CRT_VERSION_BSD_3)
		main_progname = crtp->crt_prog;
	main_path = version >= CRT_VERSION_BSD_5 ? crtp->crt_argv[0] :
	    main_progname;

	/* Some buggy versions of crt0.o have crt_ldso filled in as NULL. */
	if (__progname == NULL)
		__progname = us;

	/* Fill in some fields in _DYNAMIC or crt structure */
	if (version >= CRT_VERSION_BSD_4)
		crtp->crt_ldentry = &ld_entry;		/* crt */
	else
		crtp->crt_dp->d_entry = &ld_entry;	/* _DYNAMIC */

	/* Initialize our internal malloc package. */
	init_internal_malloc();

	/* Setup out (private) environ variable */
	environ = crtp->crt_ep;

	/* Get user and group identifiers */
	uid = getuid(); euid = geteuid();
	gid = getgid(); egid = getegid();

	careful = (uid != euid) || (gid != egid);

	rt_readenv();

	anon_open();

	/* Make a link map entry for the main program */
	main_map = alloc_link_map(main_path,
			     (struct sod *) NULL, (struct so_map *) NULL,
			     (caddr_t) 0, crtp->crt_dp);
	LM_PRIVATE(main_map)->spd_refcount++;
	LM_PRIVATE(main_map)->spd_flags |= RTLD_MAIN;

	/* Make a link map entry for ourselves */
	smp = alloc_link_map(us,
			     (struct sod *) NULL, (struct so_map *) NULL,
                             (caddr_t) crtp->crt_ba, dp);
	LM_PRIVATE(smp)->spd_refcount++;
	LM_PRIVATE(smp)->spd_flags |= RTLD_RTLD;

	/*
	 * Setup the executable's run path
	 */
	if (version >= CRT_VERSION_BSD_4) {
		add_paths = LM_PATHS(main_map);
		if (add_paths)
			add_search_path(add_paths);
	}

	/*
	 * Setup the directory search list for findshlib.  We use only
	 * the standard search path.  Any extra directories from
	 * LD_LIBRARY_PATH are searched explicitly, in rtfindlib.
	 */
	std_search_path();

	/* Map in LD_PRELOADs before the main program's shared objects so we
	   can intercept those calls */
	if (ld_preload != NULL) {
	        if(map_preload() == -1)			/* Failed */
			die();
	}

	/* Map all the shared objects that the main program depends upon */
	if(map_sods(main_map) == -1)
		die();

	if(ld_tracing) {	/* We're done */
		ld_trace(link_map_head);
		exit(0);
	}

	crtp->crt_dp->d_un.d_sdt->sdt_loaded = link_map_head->som_next;

	/* Relocate all mapped objects. */
	if(reloc_dag(main_map, ld_bind_now != NULL) == -1)	/* Failed */
		die();

	/*
         * Switch to the same malloc that the program uses.  We do
         * this before initializing the loaded objects, because their
         * initialization functions may well call malloc, and it won't
         * work right until we have set it up.
	 */
	init_external_malloc();

	/* Initialize all mapped objects. */
	init_dag(main_map);

	ddp = crtp->crt_dp->d_debug;
	ddp->dd_cc = rt_symbol_head;
	if (ddp->dd_in_debugger) {
		caddr_t	addr = (caddr_t)((long)crtp->crt_bp & (~(PAGSIZ - 1)));

		/* Set breakpoint for the benefit of debuggers */
		if (mprotect(addr, PAGSIZ,
				PROT_READ|PROT_WRITE|PROT_EXEC) == -1) {
			err(1, "Cannot set breakpoint (%s)", main_progname);
		}
		md_set_breakpoint((long)crtp->crt_bp, (long *)&ddp->dd_bpt_shadow);
		if (mprotect(addr, PAGSIZ, PROT_READ|PROT_EXEC) == -1) {
			err(1, "Cannot re-protect breakpoint (%s)",
				main_progname);
		}

		ddp->dd_bpt_addr = crtp->crt_bp;
		if (link_map_head)
			ddp->dd_sym_loaded = 1;
	}

	/* Close the hints file */
	unmaphints();

	/* Close our file descriptor */
	(void)close(crtp->crt_ldfd);
	anon_close();

	return LDSO_VERSION_HAS_DLADDR;
}

void
ld_trace(smp)
	struct so_map *smp;
{
	char	*fmt1, *fmt2, *fmt, *main_local;
	int	c;

	if ((main_local = getenv("LD_TRACE_LOADED_OBJECTS_PROGNAME")) == NULL)
		main_local = "";

	if ((fmt1 = getenv("LD_TRACE_LOADED_OBJECTS_FMT1")) == NULL)
		fmt1 = "\t-l%o.%m => %p (%x)\n";

	if ((fmt2 = getenv("LD_TRACE_LOADED_OBJECTS_FMT2")) == NULL)
		fmt2 = "\t%o (%x)\n";

	for (; smp; smp = smp->som_next) {
		struct sod	*sodp;
		char		*name, *path;

		if ((sodp = smp->som_sod) == NULL)
			continue;

		name = (char *)sodp->sod_name;
		if (LM_PARENT(smp))
			name += (long)LM_LDBASE(LM_PARENT(smp));

		if ((path = smp->som_path) == NULL)
			path = "not found";

		fmt = sodp->sod_library ? fmt1 : fmt2;
		while ((c = *fmt++) != '\0') {
			switch (c) {
			default:
				putchar(c);
				continue;
			case '\\':
				switch (c = *fmt) {
				case '\0':
					continue;
				case 'n':
					putchar('\n');
					break;
				case 't':
					putchar('\t');
					break;
				}
				break;
			case '%':
				switch (c = *fmt) {
				case '\0':
					continue;
				case '%':
				default:
					putchar(c);
					break;
				case 'A':
					printf("%s", main_local);
					break;
				case 'a':
					printf("%s", main_progname);
					break;
				case 'o':
					printf("%s", name);
					break;
				case 'm':
					printf("%d", sodp->sod_major);
					break;
				case 'n':
					printf("%d", sodp->sod_minor);
					break;
				case 'p':
					printf("%s", path);
					break;
				case 'x':
					printf("%p", smp->som_addr);
					break;
				}
				break;
			}
			++fmt;
		}
	}
}

/*
 * Allocate a new link map and return a pointer to it.
 *
 * PATH is the pathname of the shared object.
 *
 * SODP is a pointer to the shared object dependency structure responsible
 * for causing the new object to be loaded.  PARENT is the shared object
 * into which SODP points.  Both can be NULL if the new object is not
 * being loaded as a result of a shared object dependency.
 *
 * ADDR is the address at which the object has been mapped.  DP is a pointer
 * to its _dynamic structure.
 */
static struct so_map *
alloc_link_map(path, sodp, parent, addr, dp)
	const char	*path;
	struct sod	*sodp;
	struct so_map	*parent;
	caddr_t		addr;
	struct _dynamic	*dp;
{
	struct so_map		*smp;
	struct somap_private	*smpp;

#ifdef DEBUG /* { */
	xprintf("alloc_link_map: \"%s\" at %p\n", path, addr);
#endif /* } */

	smp = (struct so_map *)xmalloc(sizeof(struct so_map));
	smpp = (struct somap_private *)xmalloc(sizeof(struct somap_private));
	init_link_map(smp, smpp, path, sodp, parent, addr, dp);

	/* Link the new entry into the list of link maps */
	smpp->spd_prev = link_map_tail;
	if(link_map_tail == NULL)	/* First link map entered into list */
		link_map_head = link_map_tail = smp;
	else {				/* Append to end of list */
		link_map_tail->som_next = smp;
		link_map_tail = smp;
	}

	return smp;
}

/*
 * Initialize a link map entry that has already been allocated.
 */
static void
init_link_map(smp, smpp, path, sodp, parent, addr, dp)
	struct so_map		*smp;
	struct somap_private	*smpp;
	const char		*path;
	struct sod		*sodp;
	struct so_map		*parent;
	caddr_t			 addr;
	struct _dynamic		*dp;
{
	memset(smp, 0, sizeof *smp);
	memset(smpp, 0, sizeof *smpp);
	smp->som_spd = (caddr_t)smpp;
	smp->som_addr = addr;
	smp->som_path = path ? strdup(path) : NULL;
	smp->som_sod = sodp;
	smp->som_dynamic = dp;
	smpp->spd_parent = parent;
#ifdef SUN_COMPAT
	smpp->spd_offset =
		(addr==0 && dp && dp->d_version==LD_VERSION_SUN) ? PAGSIZ : 0;
#endif
}

/*
 * Remove the specified link map entry from the list of link maps, and free
 * the associated storage.
 */
static void
free_link_map(smp)
	struct so_map	*smp;
{
	struct somap_private	*smpp = LM_PRIVATE(smp);

#ifdef DEBUG /* { */
	xprintf("free_link_map: \"%s\"\n", smp->som_path);
#endif /* } */

	if(smpp->spd_prev == NULL)	/* Removing first entry in list */
		link_map_head = smp->som_next;
	else				/* Update link of previous entry */
		smpp->spd_prev->som_next = smp->som_next;

	if(smp->som_next == NULL)	/* Removing last entry in list */
		link_map_tail = smpp->spd_prev;
	else				/* Update back link of next entry */
		LM_PRIVATE(smp->som_next)->spd_prev = smpp->spd_prev;

	if (smp->som_path != NULL)
		free(smp->som_path);
	free(smpp);
	free(smp);
}

/*
 * Map the shared object specified by PATH into memory, if it is not
 * already mapped.  Increment the object's reference count, and return a
 * pointer to its link map.
 *
 * As a special case, if PATH is NULL, it is taken to refer to the main
 * program.
 *
 * SODP is a pointer to the shared object dependency structure that caused
 * this object to be requested.  PARENT is a pointer to the link map of
 * the shared object containing that structure.  For a shared object not
 * being mapped as a result of a shared object dependency, these pointers
 * should be NULL.  An example of this is a shared object that is explicitly
 * loaded via dlopen().
 *
 * The return value is a pointer to the link map for the requested object.
 * If the operation failed, the return value is NULL.  In that case, an
 * error message can be retrieved by calling dlerror().
 */
static struct so_map *
map_object(path, sodp, parent)
	const char	*path;
	struct sod	*sodp;
	struct so_map	*parent;
{
	struct so_map	*smp;
	struct stat	statbuf;

	if(path == NULL)	/* Special case for the main program itself */
		smp = link_map_head;
	else {
		/*
		 * Check whether the shared object is already mapped.
		 * We check first for an exact match by pathname.  That
		 * will detect the usual case.  If no match is found by
		 * pathname, then stat the file, and check for a match by
		 * device and inode.  That will detect the less common case
		 * involving multiple links to the same library.
		 */
		for(smp = link_map_head;  smp != NULL;  smp = smp->som_next) {
			if(!(LM_PRIVATE(smp)->spd_flags & (RTLD_MAIN|RTLD_RTLD))
			&& smp->som_path != NULL
			&& strcmp(smp->som_path, path) == 0)
				break;
		}
		if(smp == NULL) {  /* Check for a match by device and inode */
			if (stat(path, &statbuf) == -1) {
				generror ("cannot stat \"%s\" : %s",
					path, strerror(errno));
				return NULL;
			}
			for (smp = link_map_head;  smp != NULL;
			     smp = smp->som_next) {
				struct somap_private *smpp = LM_PRIVATE(smp);

				if (!(smpp->spd_flags & (RTLD_MAIN | RTLD_RTLD))
				&& smpp->spd_ino == statbuf.st_ino
				&& smpp->spd_dev == statbuf.st_dev)
					break;
			}
		}
	}

	if (smp == NULL) {	/* We must map the object */
		struct _dynamic	*dp;
		int		fd;
		caddr_t		addr;
		struct exec	hdr;
		struct somap_private *smpp;

		if ((fd = open(path, O_RDONLY, 0)) == -1) {
			generror ("open failed for \"%s\" : %s",
				  path, strerror (errno));
			return NULL;
		}

		if (read(fd, &hdr, sizeof(hdr)) != sizeof(hdr)) {
			generror ("header read failed for \"%s\"", path);
			(void)close(fd);
			return NULL;
		}

		if (N_BADMAG(hdr)) {
			generror ("bad magic number in \"%s\"", path);
			(void)close(fd);
			return NULL;
		}

		/*
		 * Map the entire address space of the object.  It is
		 * tempting to map just the text segment at first, in
		 * order to avoid having to use mprotect to change the
		 * protections of the data segment.  But that would not
		 * be correct.  Mmap might find a group of free pages
		 * large enough to hold the text segment, but not large
		 * enough for the entire object.  When we then mapped
		 * in the data and BSS segments, they would either be
		 * non-contiguous with the text segment (if we didn't
		 * specify MAP_FIXED), or they would map over some
		 * previously mapped region (if we did use MAP_FIXED).
		 * The only way we can be sure of getting a contigous
		 * region that is large enough is to map the entire
		 * region at once.
		 */
		if ((addr = mmap(0, hdr.a_text + hdr.a_data + hdr.a_bss,
			 PROT_READ|PROT_EXEC,
			 MAP_COPY, fd, 0)) == (caddr_t)-1) {
			generror ("mmap failed for \"%s\" : %s",
				  path, strerror (errno));
			(void)close(fd);
			return NULL;
		}

		(void)close(fd);

		/* Change the data segment to writable */
		if (mprotect(addr + hdr.a_text, hdr.a_data,
		    PROT_READ|PROT_WRITE|PROT_EXEC) != 0) {
			generror ("mprotect failed for \"%s\" : %s",
				  path, strerror (errno));
			(void)munmap(addr, hdr.a_text + hdr.a_data + hdr.a_bss);
			return NULL;
		}

		/* Map in pages of zeros for the BSS segment */
		if (mmap(addr + hdr.a_text + hdr.a_data, hdr.a_bss,
			 PROT_READ|PROT_WRITE|PROT_EXEC,
			 MAP_ANON|MAP_COPY|MAP_FIXED,
			 anon_fd, 0) == (caddr_t)-1) {
			generror ("mmap failed for \"%s\" : %s",
				  path, strerror (errno));
			(void)munmap(addr, hdr.a_text + hdr.a_data + hdr.a_bss);
			return NULL;
		}

		/* Assume _DYNAMIC is the first data item */
		dp = (struct _dynamic *)(addr+hdr.a_text);

		/* Fixup __DYNAMIC structure */
		(long)dp->d_un.d_sdt += (long)addr;

		smp = alloc_link_map(path, sodp, parent, addr, dp);

		/* save segment sizes for unmap. */
		smpp = LM_PRIVATE(smp);
		smpp->a_text = hdr.a_text;
		smpp->a_data = hdr.a_data;
		smpp->a_bss = hdr.a_bss;

		/*
		 * Save the device and inode, so we can detect multiple links
		 * to the same library.  Note, if we reach this point, then
		 * statbuf is guaranteed to have been filled in.
		 */
		smpp->spd_dev = statbuf.st_dev;
		smpp->spd_ino = statbuf.st_ino;
	}

	LM_PRIVATE(smp)->spd_refcount++;
	if(LM_PRIVATE(smp)->spd_refcount == 1) {  /* First use of object */
		/*
		 * Recursively map all of the shared objects that this
		 * one depends upon.
		 */
		if(map_sods(smp) == -1) {		/* Failed */
			unmap_object(smp, 0);		/* Clean up */
			return NULL;
		}
	}

	return smp;
}

/*
 * Map all the shared libraries named in the LD_PRELOAD environment
 * variable.
 *
 * Returns 0 on success, -1 on failure.  On failure, an error message can
 * be gotten via dlerror().
 */
        static int
map_preload __P((void)) {
	char    *ld_name = ld_preload;
	char	*name;

	while ((name = strsep(&ld_name, ":")) != NULL) {
		char		*path = NULL;
		struct so_map	*smp = NULL;

		if (*name != '\0') {
			path = (strchr(name, '/') != NULL) ?  strdup(name) :
				rtfindfile(name);
		}
		if (path == NULL) {
			generror("Can't find LD_PRELOAD shared"
				" library \"%s\"", name);
		} else {
			smp = map_object(path, (struct sod *) NULL,
				(struct so_map *) NULL);
			free(path);
		}
		if (ld_name != NULL)
			*(ld_name - 1) = ':';
		if (smp == NULL) {
			/*
			 * We don't bother to unmap already-loaded libraries
			 * on failure, because in that case the program is
			 * about to die anyway.
			 */
			return -1;
		}
	}
	return 0;
}

/*
 * Map all of the shared objects that a given object depends upon.  PARENT is
 * a pointer to the link map for the shared object whose dependencies are
 * to be mapped.
 *
 * Returns 0 on success.  Returns -1 on failure.  In that case, an error
 * message can be retrieved by calling dlerror().
 */
static int
map_sods(parent)
	struct so_map	*parent;
{
	struct somap_private	*parpp = LM_PRIVATE(parent);
	struct so_list		**soltail = &parpp->spd_children;
	long			next = LD_NEED(parent->som_dynamic);

	while(next != 0) {
		struct sod	*sodp =
			(struct sod *) (LM_LDBASE(parent) + next);
		char		*name =
			(char *) (LM_LDBASE(parent) + sodp->sod_name);
		char		*path = NULL;
		struct so_map	*smp = NULL;

		if(sodp->sod_library) {
			/*
			 * First try for a match with an adequate minor
			 * number.
			 */
			path = rtfindlib(name, sodp->sod_major,
					 sodp->sod_minor, 1);
			/*
			 * If none was found, try for just a major version
			 * match.  A warning is issued by rtfindlib in
			 * this case, since the minor version number isn't
			 * really high enough.
			 */
			if (path == NULL)
				path = rtfindlib(name, sodp->sod_major,
						 sodp->sod_minor, 0);
			if(path == NULL && !ld_tracing) {
				generror ("Can't find shared library"
					  " \"lib%s.so.%d.%d\"", name,
					  sodp->sod_major, sodp->sod_minor);
			}
		} else {
			if(careful && name[0] != '/') {
				generror("Shared library path must start"
					 " with \"/\" for \"%s\"", name);
			} else
				path = strdup(name);
		}

		if(path != NULL) {
			smp = map_object(path, sodp, parent);
			free(path);
		}

		if(smp != NULL) {
			struct so_list	*solp = (struct so_list *)
				xmalloc(sizeof(struct so_list));
			solp->sol_map = smp;
			solp->sol_next = NULL;
			*soltail = solp;
			soltail = &solp->sol_next;
		} else if(ld_tracing) {
			/*
			 * Allocate a dummy map entry so that we will get the
			 * "not found" message.
			 */
			(void)alloc_link_map(NULL, sodp, parent, 0, 0);
		} else if (ld_ignore_missing_objects) {
			const char *msg;
			/*
			 * Call __dlerror() even it we're not going to use
			 * the message, in order to clear the saved message.
			 */
			msg = __dlerror();  /* Should never be NULL */
			if (!ld_suppress_warnings)
				warnx("warning: %s", msg);
		} else  /* Give up */
			break;

		next = sodp->sod_next;
	}

	if(next != 0) {
		/*
		 * Oh drat, we have to clean up a mess.
		 *
		 * We failed to load a shared object that we depend upon.
		 * So now we have to unload any dependencies that we had
		 * already successfully loaded prior to the error.
		 *
		 * Cleaning up doesn't matter so much for the initial
		 * loading of the program, since any failure is going to
		 * terminate the program anyway.  But it is very important
		 * to clean up properly when something is being loaded
		 * via dlopen().
		 */
		struct so_list		*solp;

		while((solp = parpp->spd_children) != NULL) {
			unmap_object(solp->sol_map, 0);
			parpp->spd_children = solp->sol_next;
			free(solp);
		}

		return -1;
	}

	return 0;
}

/*
 * Relocate the DAG of shared objects rooted at the given link map
 * entry.  Returns 0 on success, or -1 on failure.  On failure, an
 * error message can be retrieved via dlerror().
 */
static int
reloc_dag(root, bind_now)
	struct so_map	*root;
	int		bind_now;
{
	struct so_map	*smp;

	/*
	 * Relocate all newly-loaded objects.  We avoid recursion for this
	 * step by taking advantage of a few facts.  This function is called
	 * only when there are in fact some newly-loaded objects to process.
	 * Furthermore, all newly-loaded objects will have their link map
	 * entries at the end of the link map list.  And, the root of the
	 * tree of objects just loaded will have been the first to be loaded
	 * and therefore the first new object in the link map list.  Finally,
	 * we take advantage of the fact that we can relocate the newly-loaded
	 * objects in any order.
	 *
	 * All these facts conspire to let us simply loop over the tail
	 * portion of the link map list, relocating each object so
	 * encountered.
	 */
	for(smp = root;  smp != NULL;  smp = smp->som_next) {
		if(!(LM_PRIVATE(smp)->spd_flags & RTLD_RTLD)) {
			if(reloc_map(smp, bind_now) < 0)
				return -1;
		}
	}

	/*
	 * Copy any relocated initialized data.  Again, we can just loop
	 * over the appropriate portion of the link map list.
	 */
	for(smp = root;  smp != NULL;  smp = smp->som_next) {
		if(!(LM_PRIVATE(smp)->spd_flags & RTLD_RTLD))
			reloc_copy(smp);
	}

	return 0;
}

/*
 * Remove a reference to the shared object specified by SMP.  If no
 * references remain, unmap the object and, recursively, its descendents.
 * This function also takes care of calling the finalization routines for
 * objects that are removed.
 *
 * If KEEP is true, then the actual calls to munmap() are skipped,
 * and the object is kept in memory.  That is used only for finalization,
 * from dlexit(), when the program is exiting.  There are two reasons
 * for it.  First, the program is exiting and there is no point in
 * spending the time to explicitly unmap its shared objects.  Second,
 * even after dlexit() has been called, there are still a couple of
 * calls that are made to functions in libc.  (This is really a bug
 * in crt0.)  So libc and the main program, at least, must remain
 * mapped in that situation.
 *
 * Under no reasonable circumstances should this function fail.  If
 * anything goes wrong, we consider it an internal error, and report
 * it with err().
 */
static void
unmap_object(smp, keep)
	struct so_map	*smp;
	int		keep;
{
	struct somap_private	*smpp = LM_PRIVATE(smp);

	smpp->spd_refcount--;
	if(smpp->spd_refcount == 0) {		/* Finished with this object */
		struct so_list	*solp;

		if(smpp->spd_flags & RTLD_INIT) {	/* Was initialized */
			/*
			 * Call the object's finalization routine.  For
			 * backward compatibility, we first try to call
			 * ".fini".  If that does not exist, we call
			 * "__fini".
			 */
			if(call_map(smp, ".fini") == -1)
				call_map(smp, "__fini");
		}

		/* Recursively unreference the object's descendents */
		while((solp = smpp->spd_children) != NULL) {
			unmap_object(solp->sol_map, keep);
			smpp->spd_children = solp->sol_next;
			free(solp);
		}

		if(!keep) {	/* Unmap the object from memory */
			if(munmap(smp->som_addr,
			smpp->a_text + smpp->a_data + smpp->a_bss) < 0)
				err(1, "internal error 1: munmap failed");

			/* Unlink and free the object's link map entry */
			free_link_map(smp);
		}
	}
}

static inline int
check_text_reloc(r, smp, addr)
struct relocation_info	*r;
struct so_map		*smp;
caddr_t			addr;
{
	char	*sym;

	if (addr >= LM_ETEXT(smp))
		return 0;

	if (RELOC_EXTERN_P(r))
		sym = LM_STRINGS(smp) +
				LM_SYMBOL(smp, RELOC_SYMBOL(r))->nz_strx;
	else
		sym = "";

	if (!ld_suppress_warnings && ld_warn_non_pure_code)
		warnx("warning: non pure code in %s at %x (%s)",
				smp->som_path, r->r_address, sym);

	if (smp->som_write == 0 &&
		mprotect(smp->som_addr + LM_TXTADDR(smp),
				LD_TEXTSZ(smp->som_dynamic),
				PROT_READ|PROT_WRITE|PROT_EXEC) == -1) {
		generror ("mprotect failed for \"%s\" : %s",
			  smp->som_path, strerror (errno));
		return -1;
	}

	smp->som_write = 1;
	return 0;
}

static int
reloc_map(smp, bind_now)
	struct so_map		*smp;
	int			bind_now;
{
	/*
	 * Caching structure for reducing the number of calls to
	 * lookup() during relocation.
	 *
	 * While relocating a given shared object, the dynamic linker
	 * maintains a caching vector that is directly indexed by
	 * the symbol number in the relocation entry.  The first time
	 * a given symbol is looked up, the caching vector is
	 * filled in with a pointer to the symbol table entry, and
	 * a pointer to the so_map of the shared object in which the
	 * symbol was defined.  On subsequent uses of the same symbol,
	 * that information is retrieved directly from the caching
	 * vector, without calling lookup() again.
	 *
	 * A symbol that is referenced in a relocation entry is
	 * typically referenced in many relocation entries, so this
	 * caching reduces the number of calls to lookup()
	 * dramatically.  The overall improvement in the speed of
	 * dynamic linking is also dramatic -- as much as a factor
	 * of three for programs that use many shared libaries.
	 */
	struct cacheent {
		struct nzlist *np;	/* Pointer to symbol entry */
		struct so_map *src_map;	/* Shared object that defined symbol */
	};

	struct _dynamic		*dp = smp->som_dynamic;
	struct relocation_info	*r = LM_REL(smp);
	struct relocation_info	*rend = r + LD_RELSZ(dp)/sizeof(*r);
	long			symbolbase = (long)LM_SYMBOL(smp, 0);
	char			*stringbase = LM_STRINGS(smp);
	int symsize		= LD_VERSION_NZLIST_P(dp->d_version) ?
					sizeof(struct nzlist) :
					sizeof(struct nlist);
	long			numsyms = LD_STABSZ(dp) / symsize;
	size_t			cachebytes = numsyms * sizeof(struct cacheent);
	struct cacheent		*symcache =
					(struct cacheent *) alloca(cachebytes);

	if(symcache == NULL) {
		generror("Cannot allocate symbol caching vector for %s",
			smp->som_path);
		return -1;
	}
	bzero(symcache, cachebytes);

	if (LD_PLTSZ(dp))
		md_fix_jmpslot(LM_PLT(smp),
				(long)LM_PLT(smp), (long)binder_entry);

	for (; r < rend; r++) {
		char	*sym;
		caddr_t	addr;

		/*
		 * Objects linked with "-Bsymbolic" can end up having unused
		 * relocation entries at the end.  These can be detected by
		 * the fact that they have an address of 0.
		 */
		if(r->r_address == 0)	/* Finished relocating this object */
			break;

		addr = smp->som_addr + r->r_address;
		if (check_text_reloc(r, smp, addr) < 0)
			return -1;

		if (RELOC_EXTERN_P(r)) {
			struct so_map	*src_map = NULL;
			struct nzlist	*p, *np;
			long	relocation;

			if (RELOC_JMPTAB_P(r) && !bind_now)
				continue;

			p = (struct nzlist *)
				(symbolbase + symsize * RELOC_SYMBOL(r));

			if (p->nz_type == (N_SETV + N_EXT))
				src_map = smp;

			sym = stringbase + p->nz_strx;

			/*
			 * Look up the symbol, checking the caching
			 * vector first.
			 */
			np = symcache[RELOC_SYMBOL(r)].np;
			if(np != NULL)	/* Symbol already cached */
				src_map = symcache[RELOC_SYMBOL(r)].src_map;
			else {	/* Symbol not cached yet */
				np = lookup(sym, &src_map, RELOC_JMPTAB_P(r));
				/*
				 * Record the needed information about
				 * the symbol in the caching vector,
				 * so that we won't have to call
				 * lookup the next time we encounter
				 * the symbol.
				 */
				symcache[RELOC_SYMBOL(r)].np = np;
				symcache[RELOC_SYMBOL(r)].src_map = src_map;
			}

			if (np == NULL) {
				generror ("Undefined symbol \"%s\" in %s:%s",
					sym, main_progname, smp->som_path);
				return -1;
                        }

			/*
			 * Found symbol definition.
			 * If it's in a link map, adjust value
			 * according to the load address of that map.
			 * Otherwise it's a run-time allocated common
			 * whose value is already up-to-date.
			 */
			relocation = np->nz_value;
			if (src_map)
				relocation += (long)src_map->som_addr;

			if (RELOC_JMPTAB_P(r)) {
				md_bind_jmpslot(relocation, addr);
				continue;
			}

			relocation += md_get_addend(r, addr);

			if (RELOC_PCREL_P(r))
				relocation -= (long)smp->som_addr;

			if (RELOC_COPY_P(r) && src_map) {
				(void)enter_rts(sym, sym_hash(sym),
					(long)addr,
					N_DATA + N_EXT,
					src_map->som_addr + np->nz_value,
					np->nz_size, src_map);
				continue;
			}

			md_relocate(r, relocation, addr, 0);
		} else {
			md_relocate(r,
#ifdef SUN_COMPAT
				md_get_rt_segment_addend(r, addr)
#else
				md_get_addend(r, addr)
#endif
					+ (long)smp->som_addr, addr, 0);
		}

	}

	if (smp->som_write) {
		if (mprotect(smp->som_addr + LM_TXTADDR(smp),
				LD_TEXTSZ(smp->som_dynamic),
				PROT_READ|PROT_EXEC) == -1) {
			generror ("mprotect failed for \"%s\" : %s",
			  	  smp->som_path, strerror (errno));
			return -1;
		}
		smp->som_write = 0;
	}
	return 0;
}

static void
reloc_copy(smp)
	struct so_map		*smp;
{
	struct rt_symbol	*rtsp;

	for (rtsp = rt_symbol_head; rtsp; rtsp = rtsp->rt_next)
		if ((rtsp->rt_smp == NULL || rtsp->rt_smp == smp) &&
				rtsp->rt_sp->nz_type == N_DATA + N_EXT) {
			bcopy(rtsp->rt_srcaddr, (caddr_t)rtsp->rt_sp->nz_value,
							rtsp->rt_sp->nz_size);
		}
}

/*
 * Initialize the DAG of shared objects rooted at the given object.
 */
static void
init_dag(smp)
	struct so_map		*smp;
{
	struct somap_private	*smpp = LM_PRIVATE(smp);

	if(!(smpp->spd_flags & RTLD_INIT)) {	/* Not initialized yet */
		smpp->spd_flags |= RTLD_INIT;

		/* Make sure all the children are initialized */
		if(smpp->spd_children != NULL)
			init_sods(smpp->spd_children);

		if(call_map(smp, ".init") == -1)
			call_map(smp, "__init");
	}
}

static void
init_sods(solp)
	struct so_list	*solp;
{
	/* Recursively initialize the rest of the list */
	if(solp->sol_next != NULL)
		init_sods(solp->sol_next);

	/* Initialize the first element of the list */
	init_dag(solp->sol_map);
}


/*
 * Call a function in a given shared object.  SMP is the shared object, and
 * SYM is the name of the function.
 *
 * Returns 0 on success, or -1 if the symbol was not found.  Failure is not
 * necessarily an error condition, so no error message is generated.
 */
static int
call_map(smp, sym)
	struct so_map		*smp;
	char			*sym;
{
	struct so_map		*src_map = smp;
	struct nzlist		*np;

	np = lookup(sym, &src_map, 1);
	if (np) {
		(*(void (*)())(src_map->som_addr + np->nz_value))();
		return 0;
	}

	return -1;
}

/*
 * Run-time common symbol table.
 */

#define RTC_TABSIZE		57
static struct rt_symbol 	*rt_symtab[RTC_TABSIZE];

/*
 * Look up a symbol in the run-time common symbol table.  For efficiency,
 * the symbol's hash value must be passed in too.
 */
static inline struct rt_symbol *
lookup_rts(name, hash)
	char		*name;
	unsigned long	 hash;
{
	register struct rt_symbol	*rtsp;

	for (rtsp = rt_symtab[hash % RTC_TABSIZE]; rtsp; rtsp = rtsp->rt_link)
		if (strcmp(name, rtsp->rt_sp->nz_name) == 0)
			return rtsp;

	return NULL;
}

/*
 * Enter a symbol into the run-time common symbol table.  For efficiency,
 * the symbol's hash value must be passed in too.
 */
static struct rt_symbol *
enter_rts(name, hash, value, type, srcaddr, size, smp)
	char		*name;
	unsigned long	 hash;
	long		 value;
	int		 type;
	caddr_t		 srcaddr;
	long		 size;
	struct so_map	*smp;
{
	register struct rt_symbol	*rtsp, **rpp;

	/* Find end of bucket */
	for (rpp = &rt_symtab[hash % RTC_TABSIZE]; *rpp; rpp = &(*rpp)->rt_link)
		continue;

	/* Allocate new common symbol */
	rtsp = (struct rt_symbol *)xmalloc(sizeof(struct rt_symbol));
	rtsp->rt_sp = (struct nzlist *)xmalloc(sizeof(struct nzlist));
	rtsp->rt_sp->nz_name = strdup(name);
	rtsp->rt_sp->nz_value = value;
	rtsp->rt_sp->nz_type = type;
	rtsp->rt_sp->nz_size = size;
	rtsp->rt_srcaddr = srcaddr;
	rtsp->rt_smp = smp;
	rtsp->rt_link = NULL;

	/* Link onto linear list as well */
	rtsp->rt_next = rt_symbol_head;
	rt_symbol_head = rtsp;

	*rpp = rtsp;

	return rtsp;
}


/*
 * Lookup NAME in the link maps. The link map producing a definition
 * is returned in SRC_MAP. If SRC_MAP is not NULL on entry the search
 * is confined to that map.
 *
 * REAL_DEF_ONLY is a boolean which specifies whether certain special
 * symbols for functions should satisfy the lookup or not.  The
 * reasons behind it are somewhat complicated.  They are motivated
 * by the scenario in which the address of a single function is
 * taken from several shared objects.  The address should come out
 * the same in all cases, because the application code might decide
 * to use it in comparisons.  To make this work, the linker creates
 * a symbol entry for the function in the main executable, with a
 * type of N_UNDF+N_EXT, an N_AUX of AUX_FUNC, and a value that
 * refers to the PLT entry for the function in the main executable.
 * If REAL_DEF_ONLY is false, then this kind of special symbol is
 * considered a "definition" when lookup up the symbol.  Since the
 * main executable is at the beginning of the shared object search
 * list, the result is that references from all shared objects will
 * resolve to the main program's PLT entry, and thus the function
 * addresses will compare equal as they should.
 *
 * When relocating the PLT entry itself, we obviously must match
 * only the true defining symbol for the function.  In that case, we
 * set REAL_DEF_ONLY to true, which disables matching the special
 * N_UNDF+N_EXT entries.
 *
 * It is not so clear how to set this flag for a lookup done from
 * dlsym.  If the lookup specifies a particular shared object other
 * than the main executable, the flag makes no difference -- only the
 * true definition will be matched.  (That is because the special
 * symbols are only present in the main executable, which will not
 * be searched.)  But when the lookup is over all the shared objects
 * (i.e., dlsym's "fd" parameter is NULL), then the flag does have an
 * effect.  We elect to match only the true definition even in that
 * case.
 *
 * The upshot of all this is the following rule of thumb: Set
 * REAL_DEF_ONLY in all cases except when processing a non-PLT
 * relocation.
 */
static struct nzlist *
lookup(name, src_map, real_def_only)
	char		*name;
	struct so_map	**src_map;	/* IN/OUT */
	int		real_def_only;
{
	unsigned long		 hash;

	hash = sym_hash(name);

	if (*src_map != NULL)	/* Look in just one specific object */
		return lookup_in_obj(name, hash, *src_map, real_def_only);
	else {	/* Search runtime symbols and all loaded objects */
		unsigned long		 common_size;
		struct so_map		*smp;
		struct rt_symbol	*rtsp;
		struct nzlist		*np;

		if ((rtsp = lookup_rts(name, hash)) != NULL)
			return rtsp->rt_sp;

		common_size = 0;
		for (smp = link_map_head; smp; smp = smp->som_next) {
			if (LM_PRIVATE(smp)->spd_flags & RTLD_RTLD)
				continue;
			np = lookup_in_obj(name, hash, smp, real_def_only);
			if (np == NULL)
				continue;
			/* We know that np->nz_value > 0 at this point. */
			if (np->nz_type == N_UNDF+N_EXT &&
			    N_AUX(&np->nlist) != AUX_FUNC) {	/* Common */
				if (common_size < np->nz_value)
					common_size = np->nz_value;
				continue;
			}

			/* We found the symbol definition. */
			*src_map = smp;
			return np;
		}
		if (common_size > 0) {	/* It is a common symbol. */
			void	*mem;

			mem = memset(xmalloc(common_size), 0, common_size);
			rtsp = enter_rts(name, hash, (long)mem, N_UNDF + N_EXT,
			    0, common_size, NULL);
			return rtsp->rt_sp;
		}

		/*
		 * Just before giving up, check for the __error() hack.
		 */
		np = lookup_errno_hack(name, src_map, real_def_only);
		if (np != NULL)
			return np;

		/* No definition was found for the symbol. */
		return NULL;
	}
}

/*
 * Lookup a symbol in one specific shared object.  The hash
 * value is passed in for efficiency.  For an explanation of the
 * "real_def_only" flag, see the comment preceding the "lookup"
 * function.
 */
static struct nzlist *
lookup_in_obj(name, hash, smp, real_def_only)
	char		*name;
	unsigned long	 hash;
	struct so_map	*smp;
	int		 real_def_only;
{
	unsigned long	 buckets;
	struct rrs_hash	*hp;
	char		*cp;
	struct nzlist	*np;
	char		*symbolbase;
	struct rrs_hash	*hashbase;
	char		*stringbase;
	size_t		symsize;

	if ((buckets = LD_BUCKETS(smp->som_dynamic)) == 0)
		return NULL;

	hashbase = LM_HASH(smp);

restart:
	hp = &hashbase[hash % buckets];
	if (hp->rh_symbolnum == -1)
		return NULL;

	symbolbase = (char *)LM_SYMBOL(smp, 0);
	stringbase = LM_STRINGS(smp);
	symsize	= LD_VERSION_NZLIST_P(smp->som_dynamic->d_version)?
	    sizeof(struct nzlist) : sizeof(struct nlist);
	for ( ; ; ) {
		np = (struct nzlist *)(symbolbase + hp->rh_symbolnum*symsize);
		cp = stringbase + np->nz_strx;
		if (strcmp(cp, name) == 0)
			break;
		if (hp->rh_next == 0)	/* End of hash chain */
			return NULL;
		hp = hashbase + hp->rh_next;
	}

	/*
	 * We have a symbol with the name we're looking for.
	 */
	if (np->nz_type == N_INDR+N_EXT) {
		/*
		 * Next symbol gives the aliased name. Restart
		 * search with new name.
		 */
		name = stringbase + (++np)->nz_strx;
		hash = sym_hash(name);
		goto restart;
	}

	if (np->nz_value == 0)	/* It's not a definition */
		return NULL;

	if (real_def_only)	/* Don't match special function symbols. */
		if (np->nz_type == N_UNDF+N_EXT &&
		    N_AUX(&np->nlist) == AUX_FUNC)
			return NULL;

	return np;
}

/*
 * Return the value of a symbol in the user's program.  This is used
 * internally for a few symbols which must exist.  If the requested
 * symbol is not found, this simply exits with a fatal error.
 */
static void *
sym_addr(name)
	char		*name;
{
	struct so_map	*smp;
	struct nzlist	*np;

	smp = NULL;
	np = lookup(name, &smp, 1);
	if (np == NULL)
		errx(1, "Program has no symbol \"%s\"", name);
	return ((smp == NULL) ? NULL : smp->som_addr) + np->nz_value;
}


static int *p_errno;	/* Pointer to errno variable in main program. */

/*
 * Help old a.out binaries that are broken by the new errno macro.  They
 * can be missing __error() through no fault of their own.  In particular,
 * old a.out binaries can link against an old libc that does not contain
 * __error(), yet still require __error() because of other libraries that
 * have been recompiled since the errno change.  This locates the backward
 * compatible work-alike we have hidden here in ld.so.
 */
static struct nzlist *
lookup_errno_hack(sym, src_map, real_def_only)
	char		*sym;
	struct so_map	**src_map;
	int		 real_def_only;
{
	struct so_map	*smp;
	struct nzlist	*np;

	if (strcmp(sym, "___error") != 0)
		return NULL;

	/*
	 * Locate errno in the main program.  If it's not there, NULL
	 * will be returned by our __error() substitute, and a core dump
	 * will follow.  That's impossible, of course, since crt0.o always
	 * supplies errno.
	 */
	smp = NULL;
	np = lookup("_errno", &smp, 1);
	if (np != NULL && smp != NULL) {
		p_errno = (int *)(smp->som_addr + np->nz_value);
#ifdef DEBUG
		xprintf(" HACK: _errno at %p in %s\n", p_errno, smp->som_path);
#endif
	}

	/*
	 * Specifically find the ld.so link map because most routines
	 * skip over it during normal operation.
	 */
	for (smp = link_map_head; ; smp = smp->som_next)
		if (LM_PRIVATE(smp)->spd_flags & RTLD_RTLD)
			break;

	/*
	 * Find our __error() substitute stashed here in ld.so.
	 */
	np = lookup("___error_unthreaded_hack", &smp, real_def_only);
	if (np != NULL)
		*src_map = smp;

#ifdef DEBUG
	if (np == NULL)
		xprintf(" HACK: %s fudge not found, oops\n", sym);
	else
		xprintf(" HACK: %s fudge in %s\n", sym, smp->som_path);
#endif

	return np;
}


/*
 * Just like __error_unthreaded(), but for those poor orphaned a.out
 * binaries from way back that are bamboozled by the new errno macro.
 */
int *
__error_unthreaded_hack()
{
	return p_errno;
}


/*
 * This routine is called from the jumptable to resolve
 * procedure calls to shared objects.
 */
long
binder(jsp)
	jmpslot_t	*jsp;
{
	struct so_map	*smp, *src_map = NULL;
	long		addr;
	char		*sym;
	struct nzlist	*np;
	int		index;

	/*
	 * Find the PLT map that contains JSP.
	 */
	for (smp = link_map_head; smp; smp = smp->som_next) {
		if (LM_PLT(smp) < jsp &&
			jsp < LM_PLT(smp) + LD_PLTSZ(smp->som_dynamic)/sizeof(*jsp))
			break;
	}

	if (smp == NULL)
		errx(1, "Call to binder from unknown location: %p\n", jsp);

	index = jsp->reloc_index & JMPSLOT_RELOC_MASK;

	/* Get the local symbol this jmpslot refers to */
	sym = LM_STRINGS(smp) +
		LM_SYMBOL(smp,RELOC_SYMBOL(&LM_REL(smp)[index]))->nz_strx;

	np = lookup(sym, &src_map, 1);
	if (np == NULL)
		errx(1, "Undefined symbol \"%s\" called from %s:%s at %p",
				sym, main_progname, smp->som_path, jsp);

	/* Fixup jmpslot so future calls transfer directly to target */
	addr = np->nz_value;
	if (src_map)
		addr += (long)src_map->som_addr;

	md_fix_jmpslot(jsp, (long)jsp, addr);

#if DEBUG
        xprintf(" BINDER: %s located at = %#x in %s\n", sym, addr,
                src_map->som_path);
#endif
	return addr;
}

static struct hints_header	*hheader;	/* NULL means not mapped */
static struct hints_bucket	*hbuckets;
static char			*hstrtab;

/*
 * Map the hints file into memory, if it is not already mapped.  Returns
 * 0 on success, or -1 on failure.
 */
static int
maphints __P((void))
{
	static int		hints_bad;	/* TRUE if hints are unusable */
	static int		paths_added;
	int			hfd;
	struct hints_header	hdr;
	caddr_t			addr;

	if (hheader != NULL)	/* Already mapped */
		return 0;

	if (hints_bad)		/* Known to be corrupt or unavailable */
		return -1;

	if ((hfd = open(_PATH_LD_HINTS, O_RDONLY, 0)) == -1) {
		hints_bad = 1;
		return -1;
	}

	/* Read the header and check it */

	if (read(hfd, &hdr, sizeof hdr) != sizeof hdr ||
	    HH_BADMAG(hdr) ||
	    (hdr.hh_version != LD_HINTS_VERSION_1 &&
	     hdr.hh_version != LD_HINTS_VERSION_2)) {
		close(hfd);
		hints_bad = 1;
		return -1;
	}

	/* Map the hints into memory */

	addr = mmap(0, hdr.hh_ehints, PROT_READ, MAP_SHARED, hfd, 0);
	if (addr == (caddr_t)-1) {
		close(hfd);
		hints_bad = 1;
		return -1;
	}

	close(hfd);

	hheader = (struct hints_header *)addr;
	hbuckets = (struct hints_bucket *)(addr + hheader->hh_hashtab);
	hstrtab = (char *)(addr + hheader->hh_strtab);
	/* pluck out the system ldconfig path */
	if (hheader->hh_version >= LD_HINTS_VERSION_2 && !paths_added) {
		add_search_path(hstrtab + hheader->hh_dirlist);
		paths_added = 1;
	}

	return 0;
}

/*
 * Unmap the hints file, if it is currently mapped.
 */
static void
unmaphints()
{
	if (hheader != NULL) {
		munmap((caddr_t)hheader, hheader->hh_ehints);
		hheader = NULL;
	}
}

int
hinthash(cp, vmajor)
	char	*cp;
	int	vmajor;
{
	int	k = 0;

	while (*cp)
		k = (((k << 1) + (k >> 14)) ^ (*cp++)) & 0x3fff;

	k = (((k << 1) + (k >> 14)) ^ (vmajor*257)) & 0x3fff;

	return k;
}

#undef major
#undef minor

/*
 * Search for a library in the hints generated by ldconfig.  On success,
 * returns the full pathname of the matching library.  This string is
 * always dynamically allocated on the heap.
 *
 * MINORP is an in/out parameter.  If the incoming value of *MINORP is
 * >= 0, then no library will be considered a match unless its minor
 * version number is at least that large.  Otherwise, only the major
 * version number is checked.  In any case, the minor number of the
 * matching library is stored into *MINORP.
 *
 * Returns NULL if the library cannot be found.
 */
static char *
findhint(name, major, minorp)
	char	*name;
	int	major;
	int	*minorp;
{
	struct hints_bucket	*bp =
		hbuckets + (hinthash(name, major) % hheader->hh_nbucket);

	while (1) {
		/* Sanity check */
		if (bp->hi_namex >= hheader->hh_strtab_sz) {
			warnx("Bad name index: %#x\n", bp->hi_namex);
			break;
		}
		if (bp->hi_pathx >= hheader->hh_strtab_sz) {
			warnx("Bad path index: %#x\n", bp->hi_pathx);
			break;
		}
		/*
		 * For a given major number, the hints file has only one
		 * entry -- namely, the one with the highest minor number.
		 * If we find an entry with a matching major number, we
		 * know it is the best one.
		 */
		if (strcmp(name, hstrtab + bp->hi_namex) == 0 &&
		    bp->hi_major == major) {
			struct stat s;
			int realminor;

			realminor = bp->hi_ndewey >= 2 ? bp->hi_minor : 0;
			if (realminor < *minorp)	/* Not good enough */
				return NULL;
			if (stat(hstrtab + bp->hi_pathx, &s) == -1)
				return NULL;  /* Doesn't actually exist */
			*minorp = realminor;
			return strdup(hstrtab + bp->hi_pathx);
		}

		if (bp->hi_next == -1)
			break;

		/* Move on to next in bucket */
		bp = &hbuckets[bp->hi_next];
	}

	/* No hints available for name */
	return NULL;
}

/*
 * Search for the given shared library.  On success, returns a string
 * containing the full pathname for the library.  This string is always
 * dynamically allocated on the heap.
 *
 * Returns NULL if the library cannot be found.
 */
static char *
rtfindlib(name, major, minor, strictminor)
	char	*name;
	int	major, minor;
	int	strictminor;
{
	char	*ld_path = ld_library_path;
	char	*path = NULL;
	int	realminor;

	realminor = strictminor ? minor : -1;
	if (ld_path != NULL) {	/* First, search the directories in ld_path */
		/*
		 * There is no point in trying to use the hints file for this.
		 */
		char	*dir;

		while (path == NULL && (dir = strsep(&ld_path, ":")) != NULL) {
			path = search_lib_dir(dir, name, &major, &realminor, 0);
			if (ld_path != NULL)
				*(ld_path - 1) = ':';
		}
	}

	if (path == NULL && maphints() == 0)	/* Search the hints file */
		path = findhint(name, major, &realminor);

	if (path == NULL)	/* Search the standard directories */
		path = findshlib(name, &major, &realminor, 0);

	if (path != NULL && realminor < minor && !ld_suppress_warnings) {
		warnx("warning: %s: minor version %d"
		      " older than expected %d, using it anyway",
		      path, realminor, minor);
	}

	return path;
}

/*
 * Search for the given shared library file.  This is similar to rtfindlib,
 * except that the argument is the actual name of the desired library file.
 * Thus there is no need to worry about version numbers.  The return value
 * is a string containing the full pathname for the library.  This string
 * is always dynamically allocated on the heap.
 *
 * Returns NULL if the library cannot be found.
 */
static char *
rtfindfile(name)
	const char	*name;
{
	char	*ld_path = ld_library_path;
	char	*path = NULL;

	if (ld_path != NULL) {	/* First, search the directories in ld_path */
		char	*dir;

		while (path == NULL && (dir = strsep(&ld_path, ":")) != NULL) {
			struct stat	sb;

			path = concat(dir, "/", name);
			if (lstat(path, &sb) == -1) {	/* Does not exist */
				free(path);
				path = NULL;
			}
			if (ld_path != NULL)
				*(ld_path - 1) = ':';
		}
	}

	/*
	 * We don't search the hints file.  It is organized around major
	 * and minor version numbers, so it is not suitable for finding
	 * a specific file name.
	 */

	if (path == NULL)	/* Search the standard directories */
		path = find_lib_file(name);

	return path;
}

/*
 * Buffer for error messages and a pointer that is set to point to the buffer
 * when an error occurs.  It acts as a last error flag, being set to NULL
 * after an error is returned.
 */
#define DLERROR_BUF_SIZE 512
static char  dlerror_buf [DLERROR_BUF_SIZE];
static char *dlerror_msg = NULL;


static void *
__dlopen(path, mode)
	const char	*path;
	int		 mode;
{
	struct so_map	*old_tail = link_map_tail;
	struct so_map	*smp;
	int		bind_now = mode == RTLD_NOW;
	char		*name;

	/*
	 * path == NULL is handled by map_object()
	 */

	anon_open();

	name = (path && strchr(path, '/') == NULL) ? rtfindfile(path) : (char *)path;

	/* Map the object, and the objects on which it depends */
	smp = map_object(name, (struct sod *) NULL, (struct so_map *) NULL);
	if (name != path)
		free(name);
	if(smp == NULL)		/* Failed */
		return NULL;
	LM_PRIVATE(smp)->spd_flags |= RTLD_DL;

	/* Relocate and initialize all newly-mapped objects */
	if(link_map_tail != old_tail) {  /* We have mapped some new objects */
		if(reloc_dag(smp, bind_now) == -1)	/* Failed */
			return NULL;
		init_dag(smp);
	}

	unmaphints();
	anon_close();

	return smp;
}

static int
__dlclose(fd)
	void	*fd;
{
	struct so_map	*smp = (struct so_map *)fd;
	struct so_map	*scanp;

#ifdef DEBUG
        xprintf("dlclose(%s): refcount = %d\n", smp->som_path,
                LM_PRIVATE(smp)->spd_refcount);
#endif
	/* Check the argument for validity */
	for(scanp = link_map_head;  scanp != NULL;  scanp = scanp->som_next)
		if(scanp == smp)	/* We found the map in the list */
			break;
	if(scanp == NULL || !(LM_PRIVATE(smp)->spd_flags & RTLD_DL)) {
		generror("Invalid argument to dlclose");
		return -1;
	}

        unmap_object(smp, 0);

	return 0;
}

/*
 * This form of dlsym is obsolete.  Current versions of crt0 don't call
 * it.  It can still be called by old executables that were linked with
 * old versions of crt0.
 */
static void *
__dlsym(fd, sym)
	void		*fd;
	const char	*sym;
{
	if (fd == RTLD_NEXT) {
		generror("RTLD_NEXT not supported by this version of"
		    " crt0.o");
		return NULL;
	}
	return __dlsym3(fd, sym, NULL);
}

static void *
resolvesym(fd, sym, retaddr)
	void	*fd;
	char	*sym;
	void	*retaddr;
{
	struct so_map	*smp;
	struct so_map	*src_map;
	struct nzlist	*np;
	long		addr;

	if (fd == RTLD_NEXT) {
		/* Find the shared object that contains the caller. */
		for (smp = link_map_head;  smp != NULL;  smp = smp->som_next) {
			void *textbase = smp->som_addr + LM_TXTADDR(smp);
			void *textlimit = LM_ETEXT(smp);

			if (textbase <= retaddr && retaddr < textlimit)
				break;
		}
		if (smp == NULL) {
			generror("Cannot determine caller's shared object");
			return NULL;
		}
		smp = smp->som_next;
		if (smp != NULL && LM_PRIVATE(smp)->spd_flags & RTLD_RTLD)
			smp = smp->som_next;
		if (smp == NULL) {
			generror("No next shared object for RTLD_NEXT");
			return NULL;
		}
		do {
			src_map = smp;
			np = lookup(sym, &src_map, 1);
		} while (np == NULL && (smp = smp->som_next) != NULL);
	} else {
		smp = (struct so_map *)fd;
		src_map = NULL;

		/*
		 * Restrict search to passed map if dlopen()ed.
		 */
		if (smp != NULL && LM_PRIVATE(smp)->spd_flags & RTLD_DL)
			src_map = smp;

		np = lookup(sym, &src_map, 1);
	}

	if (np == NULL) {
		generror("Undefined symbol");
		return NULL;
	}

	addr = np->nz_value;
	if (src_map)
		addr += (long)src_map->som_addr;

	return (void *)addr;
}

static int
__dladdr(addr, dlip)
	const void	*addr;
	Dl_info		*dlip;
{
	struct _dynamic	*dp;
	struct so_map	*smp;
	char		*stringbase;
	long		 numsyms;
	int		 symsize;
	int		 i;

	/* Find the shared object that contains the address. */
	for (smp = link_map_head;  smp != NULL;  smp = smp->som_next) {
		struct so_map		*src_map;
		struct somap_private	*smpp;
		struct nzlist		*np;

		smpp = LM_PRIVATE(smp);
		if (smpp->spd_flags & RTLD_RTLD)
			continue;

		if ((void *)smp->som_addr > addr)
			continue;

		src_map = smp;
		if ((np = lookup(END_SYM, &src_map, 1)) == NULL)
			continue;	/* No "_end" symbol?! */
		if (addr < (void *)(smp->som_addr + np->nz_value))
			break;
	}
	if (smp == NULL) {
		generror("No shared object contains address");
		return 0;
	}
	dlip->dli_fname = smp->som_path;
	dlip->dli_fbase = smp->som_addr;
	dlip->dli_saddr = (void *) 0;
	dlip->dli_sname = NULL;

	dp = smp->som_dynamic;
	symsize	= LD_VERSION_NZLIST_P(dp->d_version) ?
	    sizeof(struct nzlist) : sizeof(struct nlist);
	numsyms = LD_STABSZ(dp) / symsize;
	stringbase = LM_STRINGS(smp);

	for (i = 0;  i < numsyms;  i++) {
		struct nzlist	*symp = LM_SYMBOL(smp, i);
		unsigned long	 value;

		/* Reject all except definitions. */
		if (symp->nz_type != N_EXT + N_ABS &&
		    symp->nz_type != N_EXT + N_TEXT &&
		    symp->nz_type != N_EXT + N_DATA &&
		    symp->nz_type != N_EXT + N_BSS)
			continue;

		/*
		 * If the symbol is greater than the specified address, or
		 * if it is further away from addr than the current nearest
		 * symbol, then reject it.
		 */
		value = (unsigned long) (smp->som_addr + symp->nz_value);
		if (value > (unsigned long) addr ||
		    value < (unsigned long) dlip->dli_saddr)
			continue;

		/* Update our idea of the nearest symbol. */
		dlip->dli_sname = stringbase + symp->nz_strx;
		dlip->dli_saddr = (void *) value;

		if (dlip->dli_saddr == addr)	/* Can't get any closer. */
		    break;
	}
	/*
	 * Remove any leading underscore from the symbol name, to hide
	 * our a.out-ness.
	 */
	if (dlip->dli_sname != NULL && dlip->dli_sname[0] == '_')
		dlip->dli_sname++;
	return 1;
}

static void *
__dlsym3(fd, sym, retaddr)
	void		*fd;
	const char	*sym;
	void		*retaddr;
{
	void *result;

	result = resolvesym(fd, sym, retaddr);
	/*
	 * XXX - Ugly, but it makes the least impact on the run-time loader
	 * sources.  We assume that most of the time the error is a
	 * undefined symbol error from above, so we try again.  If it's
	 * not an undefined symbol we end up getting the same error twice,
	 * but that's acceptable.
	 */
	if (result == NULL) {
		/* Prepend an underscore and try again */
		char *newsym = xmalloc(strlen(sym) + 2);

		newsym[0] = '_';
		strcpy(&newsym[1], sym);
		result = resolvesym(fd, newsym, retaddr);
		free(newsym);
	}
	return result;
}

static const char *
__dlerror __P((void))
{
        const char	*err;

        err = dlerror_msg;
        dlerror_msg = NULL;  /* Next call will return NULL */

        return err;
}

static void
__dlexit __P((void))
{
#ifdef DEBUG
xprintf("__dlexit called\n");
#endif

	unmap_object(link_map_head, 1);
}

/*
 * Print the current error message and exit with failure status.
 */
static void
die __P((void))
{
	const char	*msg;

	fprintf(stderr, "ld.so failed");
	if ((msg = __dlerror()) != NULL)
		fprintf(stderr, ": %s", msg);
	putc('\n', stderr);
	_exit(1);
}


/*
 * Generate an error message that can be later be retrieved via dlerror.
 */
static void
generror(char *fmt, ...)
{
	va_list	ap;

	va_start(ap, fmt);
        vsnprintf (dlerror_buf, DLERROR_BUF_SIZE, fmt, ap);
        dlerror_msg = dlerror_buf;

	va_end(ap);
}

void
xprintf(char *fmt, ...)
{
	char buf[256];
	va_list	ap;

	va_start(ap, fmt);
	vsnprintf(buf, sizeof(buf), fmt, ap);
	(void)write(STDOUT_FILENO, buf, strlen(buf));
	va_end(ap);
}

/*
 * rt_readenv() etc.
 *
 * Do a sweep over the environment once only, pick up what
 * looks interesting.
 *
 * This is pretty obscure, but is relatively simple.  Simply
 * look at each environment variable, if it starts with "LD_" then
 * look closer at it.  If it's in our table, set the variable
 * listed.  effectively, this is like:
 *    ld_preload = careful ? NULL : getenv("LD_PRELOAD");
 * except that the environment is scanned once only to pick up all
 * known variables, rather than scanned multiple times for each
 * variable.
 *
 * If an environment variable of interest is set to the empty string, we
 * treat it as if it were unset.
 */

#define L(n, u, v) { n, sizeof(n) - 1, u, v },
struct env_scan_tab {
	char	*name;
	int	len;
	int	unsafe;
	char	**value;
} scan_tab[] = {
	L("LD_LIBRARY_PATH=",		1, &ld_library_path)
	L("LD_PRELOAD=",		1, &ld_preload)
	L("LD_IGNORE_MISSING_OBJECTS=",	1, &ld_ignore_missing_objects)
	L("LD_TRACE_LOADED_OBJECTS=",	0, &ld_tracing)
	L("LD_BIND_NOW=",		0, &ld_bind_now)
	L("LD_SUPPRESS_WARNINGS=",	0, &ld_suppress_warnings)
	L("LD_WARN_NON_PURE_CODE=",	0, &ld_warn_non_pure_code)
	{ NULL, 0, 0, NULL }
};
#undef L

static void
rt_readenv()
{
	char **p = environ;
	char *v;
	struct env_scan_tab *t;

	/* for each string in the environment... */
	while ((v = *p++)) {

		/* check for LD_xxx */
		if (v[0] != 'L' || v[1] != 'D' || v[2] != '_')
			continue;

		for (t = scan_tab; t->name; t++) {
			if (careful && t->unsafe)
				continue;	/* skip for set[ug]id */
			if (strncmp(t->name, v, t->len) == 0) {
				if (*(v + t->len) != '\0')	/* Not empty */
					*t->value = v + t->len;
				break;
			}
		}
	}
}

/*
 * Malloc implementation for use within the dynamic linker.  At first
 * we do a simple allocation using sbrk.  After the user's program
 * has been loaded, we switch to using whatever malloc functions are
 * defined there.
 */

/* Symbols related to the sbrk and brk implementations. */
#define CURBRK_SYM	"curbrk"
#define MINBRK_SYM	"minbrk"
#define END_SYM		"_end"

/* Symbols related to malloc. */
#define FREE_SYM	"_free"
#define MALLOC_SYM	"_malloc"
#define REALLOC_SYM	"_realloc"

/* Hooks into the implementation of sbrk and brk. */
extern char *curbrk __asm__(CURBRK_SYM);
extern char *minbrk __asm__(MINBRK_SYM);

/* Pointers to the user program's malloc functions. */
static void	*(*p_malloc) __P((size_t));
static void	*(*p_realloc) __P((void *, size_t));
static void	 (*p_free) __P((void *));

/* Upper limit of the memory allocated by our internal malloc. */
static char	*rtld_alloc_lev;

/*
 * Set up the internal malloc so that it will take its memory from the
 * main program's sbrk arena.
 */
static void
init_internal_malloc __P((void))
{
	const struct exec *hdr;

	/*
         * Before anything calls sbrk or brk, we have to initialize
         * its idea of the current break level to just beyond the main
         * program's address space.  Strictly speaking, the right
         * way to do that is to look up the value of "_end" in the
         * application's run time symbol table.
         *
         * That is what we used to do, and it works correctly for
         * every valid program.  Unfortunately, it doesn't work right
         * for "unexec"ed versions of emacs.  They are incorrectly
         * generated with a wrong value for "_end".  (xemacs gets it
         * right.)
         *
         * To work around this, we peek at the exec header to get the
         * sizes of the text, data, and bss segments.  Luckily, the
         * header is in memory at the start of the first mapped page.
         * From the segment sizes, we can calculate a proper initial
         * value for the break level.
	 */
	hdr = (const struct exec *)PAGSIZ;
	if (N_BADMAG(*hdr))	/* Sanity check */
		errx(1, "Cannot find program's a.out header");
	rtld_alloc_lev = curbrk = minbrk =
		(char *)hdr + hdr->a_text + hdr->a_data + hdr->a_bss;
}

/*
 * Set things up so that the dynamic linker can use the program's
 * malloc functions.
 */
static void
init_external_malloc __P((void))
{
	/*
         * Patch the program's idea of the current break address to
         * what it really is as a result of the allocations we have
         * already done.
	 */
	*(char **)(sym_addr(CURBRK_SYM)) = curbrk;

	/*
         * Set the minimum break level too.  Otherwise, "unexec"ed
         * emacs sets the break too low and wipes out our tables of
         * shared objects.
	 */
	*(char **)(sym_addr(MINBRK_SYM)) = curbrk;

	/*
	 * Set up pointers to the program's allocation functions, so
	 * that we can use them from now on.
	 */
	p_malloc = (void *(*)(size_t))(sym_addr(MALLOC_SYM));
	p_free = (void (*)(void *))(sym_addr(FREE_SYM));
	p_realloc = (void *(*)(void *, size_t))(sym_addr(REALLOC_SYM));
}

void *
malloc(size)
	size_t	 size;
{
	char		*p;

	/* If we are far enough along, we can use the system malloc. */
	if (p_malloc != NULL)
		return (*p_malloc)(size);

	/*
         * Otherwise we use our simple built-in malloc.  We get the
         * memory from brk() in increments of one page.  We store the
         * allocated size in the first word, so that realloc can be
         * made to work.
	 */
	if (rtld_alloc_lev == NULL)
		errx(1, "Internal error: internal malloc called before"
		    " being initialized");

	p = (char *)ALIGN(rtld_alloc_lev);
	rtld_alloc_lev = p + sizeof(size_t) + size;

	if (rtld_alloc_lev > curbrk) {	/* Get memory from system */
		char	*newbrk;

		newbrk = (char *)
		    roundup2((unsigned long)rtld_alloc_lev, PAGSIZ);
		if (brk(newbrk) == -1)
			return NULL;
	}

	*(size_t *)p = size;
	return p + sizeof(size_t);
}

void *
realloc(ptr, size)
	void	*ptr;
	size_t	 size;
{
	size_t	 old_size;
	void	*new_ptr;

	if (ptr == NULL)
		return malloc(size);

	/*
	 * If we are far enough along, and if the memory originally came
	 * from the system malloc, we can use the system realloc.
	 */
	if (p_realloc != NULL && (char *)ptr >= rtld_alloc_lev)
		return (*p_realloc)(ptr, size);

	old_size = *((size_t *)ptr - 1);
	if (old_size >= size)	/* Not expanding the region */
		return ptr;

	new_ptr = malloc(size);
	if (new_ptr != NULL)
		memcpy(new_ptr, ptr, old_size);
	return new_ptr;
}

void
free(ptr)
	void	*ptr;
{
	if (ptr == NULL)
		return;

	/*
	 * If we are far enough along, and if the memory originally came
	 * from the system malloc, we can use the system free.  Otherwise
	 * we can't free the memory and we just let it go to waste.
	 */
	if (p_free != NULL && (char *)ptr >= rtld_alloc_lev)
		(*p_free)(ptr);
}