Patrick Welche <prlw1@cam.ac.uk>

[netbsd-mini2440.git] / libexec / ld.elf_so / rtld.c

/*      $NetBSD: rtld.c,v 1.126 2009/11/17 18:44:33 skrll Exp $  */

/*
 * Copyright 1996 John D. Polstra.
 * Copyright 1996 Matt Thomas <matt@3am-software.com>
 * Copyright 2002 Charles M. Hannum <root@ihack.net>
 * 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 John Polstra.
 * 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.
 */

/*
 * Dynamic linker for ELF.
 *
 * John Polstra <jdp@polstra.com>.
 */

#include <sys/cdefs.h>
#ifndef lint
__RCSID("$NetBSD: rtld.c,v 1.126 2009/11/17 18:44:33 skrll Exp $");
#endif /* not lint */

#include <err.h>
#include <errno.h>
#include <fcntl.h>
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/param.h>
#include <sys/mman.h>
#include <dirent.h>

#include <ctype.h>

#include <dlfcn.h>
#include "debug.h"
#include "rtld.h"

#if !defined(lint)
#include "sysident.h"
#endif

/*
 * Function declarations.
 */
static void     _rtld_init(caddr_t, caddr_t, const char *);
static void     _rtld_exit(void);

Elf_Addr        _rtld(Elf_Addr *, Elf_Addr);


/*
 * Data declarations.
 */
static char    *error_message;  /* Message for dlopen(), or NULL */

struct r_debug  _rtld_debug;    /* for GDB; */
bool            _rtld_trust;    /* False for setuid and setgid programs */
Obj_Entry      *_rtld_objlist;  /* Head of linked list of shared objects */
Obj_Entry     **_rtld_objtail;  /* Link field of last object in list */
Obj_Entry      *_rtld_objmain;  /* The main program shared object */
Obj_Entry       _rtld_objself;  /* The dynamic linker shared object */
const char      _rtld_path[] = _PATH_RTLD;

/* Initialize a fake symbol for resolving undefined weak references. */
Elf_Sym         _rtld_sym_zero = {
    .st_info    = ELF_ST_INFO(STB_GLOBAL, STT_NOTYPE),
    .st_shndx   = SHN_ABS,
};
size_t  _rtld_pagesz;   /* Page size, as provided by kernel */

Search_Path    *_rtld_default_paths;
Search_Path    *_rtld_paths;

Library_Xform  *_rtld_xforms;

/*
 * Global declarations normally provided by crt0.
 */
char           *__progname;
char          **environ;

#if defined(RTLD_DEBUG)
#ifndef __sh__
extern Elf_Addr _GLOBAL_OFFSET_TABLE_[];
#else  /* 32-bit SuperH */
register Elf_Addr *_GLOBAL_OFFSET_TABLE_ asm("r12");
#endif
#endif /* RTLD_DEBUG */
extern Elf_Dyn  _DYNAMIC;

static void _rtld_call_fini_functions(int);
static void _rtld_call_init_functions(void);
static void _rtld_initlist_visit(Objlist *, Obj_Entry *, int);
static void _rtld_initlist_tsort(Objlist *, int);
static Obj_Entry *_rtld_dlcheck(void *);
static void _rtld_init_dag(Obj_Entry *);
static void _rtld_init_dag1(Obj_Entry *, Obj_Entry *);
static void _rtld_objlist_remove(Objlist *, Obj_Entry *);
static void _rtld_objlist_clear(Objlist *);
static void _rtld_unload_object(Obj_Entry *, bool);
static void _rtld_unref_dag(Obj_Entry *);
static Obj_Entry *_rtld_obj_from_addr(const void *);

static void
_rtld_call_fini_functions(int force)
{
        Objlist_Entry *elm;
        Objlist finilist;
        Obj_Entry *obj;

        dbg(("_rtld_call_fini_functions(%d)", force));

        SIMPLEQ_INIT(&finilist);
        _rtld_initlist_tsort(&finilist, 1);

        /* First pass: objects _not_ marked with DF_1_INITFIRST. */
        SIMPLEQ_FOREACH(elm, &finilist, link) {
                obj = elm->obj;
                if (obj->refcount > 0 && !force) {
                        continue;
                }
                if (obj->fini == NULL || obj->fini_called || obj->initfirst) {
                        continue;
                }
                dbg (("calling fini function %s at %p",  obj->path,
                    (void *)obj->fini));
                obj->fini_called = 1;
                (*obj->fini)();
        }

        /* Second pass: objects marked with DF_1_INITFIRST. */
        SIMPLEQ_FOREACH(elm, &finilist, link) {
                obj = elm->obj;
                if (obj->refcount > 0 && !force) {
                        continue;
                }
                if (obj->fini == NULL || obj->fini_called) {
                        continue;
                }
                dbg (("calling fini function %s at %p (DF_1_INITFIRST)",
                    obj->path, (void *)obj->fini));
                obj->fini_called = 1;
                (*obj->fini)();
        }

        _rtld_objlist_clear(&finilist);
}

static void
_rtld_call_init_functions()
{
        Objlist_Entry *elm;
        Objlist initlist;
        Obj_Entry *obj;

        dbg(("_rtld_call_init_functions()"));
        SIMPLEQ_INIT(&initlist);
        _rtld_initlist_tsort(&initlist, 0);

        /* First pass: objects marked with DF_1_INITFIRST. */
        SIMPLEQ_FOREACH(elm, &initlist, link) {
                obj = elm->obj;
                if (obj->init == NULL || obj->init_called || !obj->initfirst) {
                        continue;
                }
                dbg (("calling init function %s at %p (DF_1_INITFIRST)",
                    obj->path, (void *)obj->init));
                obj->init_called = 1;
                (*obj->init)();
        }

        /* Second pass: all other objects. */
        SIMPLEQ_FOREACH(elm, &initlist, link) {
                obj = elm->obj;
                if (obj->init == NULL || obj->init_called) {
                        continue;
                }
                dbg (("calling init function %s at %p",  obj->path,
                    (void *)obj->init));
                obj->init_called = 1;
                (*obj->init)();
        }

        _rtld_objlist_clear(&initlist);
}

/*
 * Initialize the dynamic linker.  The argument is the address at which
 * the dynamic linker has been mapped into memory.  The primary task of
 * this function is to create an Obj_Entry for the dynamic linker and
 * to resolve the PLT relocation for platforms that need it (those that
 * define __HAVE_FUNCTION_DESCRIPTORS
 */
static void
_rtld_init(caddr_t mapbase, caddr_t relocbase, const char *execname)
{

        /* Conjure up an Obj_Entry structure for the dynamic linker. */
        _rtld_objself.path = __UNCONST(_rtld_path);
        _rtld_objself.pathlen = sizeof(_rtld_path)-1;
        _rtld_objself.rtld = true;
        _rtld_objself.mapbase = mapbase;
        _rtld_objself.relocbase = relocbase;
        _rtld_objself.dynamic = (Elf_Dyn *) &_DYNAMIC;
        _rtld_objself.strtab = "_rtld_sym_zero";

        /*
         * Set value to -relocabase so that
         * _rtld_objself.relocbase + _rtld_smy_zero.st_value == 0
         * This allows unresolved references to weak symbols to be computed
         * to value a value of 0.
         */
        _rtld_sym_zero.st_value = -(uintptr_t)relocbase;

        _rtld_digest_dynamic(_rtld_path, &_rtld_objself);
        assert(!_rtld_objself.needed);
#if !defined(__hppa__)
        assert(!_rtld_objself.pltrel && !_rtld_objself.pltrela);
#else
        _rtld_relocate_plt_objects(&_rtld_objself);
#endif
#if !defined(__mips__) && !defined(__hppa__)
        assert(!_rtld_objself.pltgot);
#endif
#if !defined(__arm__) && !defined(__mips__) && !defined(__sh__)
        /* ARM, MIPS and SH{3,5} have a bogus DT_TEXTREL. */
        assert(!_rtld_objself.textrel);
#endif

        _rtld_add_paths(execname, &_rtld_default_paths,
            RTLD_DEFAULT_LIBRARY_PATH);

#ifdef RTLD_ARCH_SUBDIR
        _rtld_add_paths(execname, &_rtld_default_paths,
            RTLD_DEFAULT_LIBRARY_PATH "/" RTLD_ARCH_SUBDIR);
#endif

        /*
         * Set up the _rtld_objlist pointer, so that rtld symbols can be found.
         */
        _rtld_objlist = &_rtld_objself;

        /* Make the object list empty again. */
        _rtld_objlist = NULL;
        _rtld_objtail = &_rtld_objlist;

        _rtld_debug.r_brk = _rtld_debug_state;
        _rtld_debug.r_state = RT_CONSISTENT;
}

/*
 * Cleanup procedure.  It will be called (by the atexit() mechanism) just
 * before the process exits.
 */
static void
_rtld_exit(void)
{
        dbg(("rtld_exit()"));

        _rtld_call_fini_functions(1);
}

/*
 * Main entry point for dynamic linking.  The argument is the stack
 * pointer.  The stack is expected to be laid out as described in the
 * SVR4 ABI specification, Intel 386 Processor Supplement.  Specifically,
 * the stack pointer points to a word containing ARGC.  Following that
 * in the stack is a null-terminated sequence of pointers to argument
 * strings.  Then comes a null-terminated sequence of pointers to
 * environment strings.  Finally, there is a sequence of "auxiliary
 * vector" entries.
 *
 * This function returns the entry point for the main program, the dynamic
 * linker's exit procedure in sp[0], and a pointer to the main object in
 * sp[1].
 */
Elf_Addr
_rtld(Elf_Addr *sp, Elf_Addr relocbase)
{
        const AuxInfo  *pAUX_base, *pAUX_entry, *pAUX_execfd, *pAUX_phdr,
                       *pAUX_phent, *pAUX_phnum, *pAUX_euid, *pAUX_egid,
                       *pAUX_ruid, *pAUX_rgid;
        const AuxInfo  *pAUX_pagesz;
        char          **env;
        const AuxInfo  *aux;
        const AuxInfo  *auxp;
        Elf_Addr       *const osp = sp;
        bool            bind_now = 0;
        const char     *ld_bind_now;
        const char    **argv;
        const char     *execname;
        long            argc;
        const char **real___progname;
        const Obj_Entry **real___mainprog_obj;
        char ***real_environ;
#if defined(RTLD_DEBUG)
        int i = 0;
#endif

        /*
         * On entry, the dynamic linker itself has not been relocated yet.
         * Be very careful not to reference any global data until after
         * _rtld_init has returned.  It is OK to reference file-scope statics
         * and string constants, and to call static and global functions.
         */
        /* Find the auxiliary vector on the stack. */
        /* first Elf_Word reserved to address of exit routine */
#if defined(RTLD_DEBUG)
        debug = 1;
        dbg(("sp = %p, argc = %ld, argv = %p <%s> relocbase %p", sp,
            (long)sp[2], &sp[3], (char *) sp[3], (void *)relocbase));
        dbg(("got is at %p, dynamic is at %p", _GLOBAL_OFFSET_TABLE_,
            &_DYNAMIC));
        dbg(("_ctype_ is %p", _ctype_));
#endif

        sp += 2;                /* skip over return argument space */
        argv = (const char **) &sp[1];
        argc = *(long *)sp;
        sp += 2 + argc;         /* Skip over argc, arguments, and NULL
                                 * terminator */
        env = (char **) sp;
        while (*sp++ != 0) {    /* Skip over environment, and NULL terminator */
#if defined(RTLD_DEBUG)
                dbg(("env[%d] = %p %s", i++, (void *)sp[-1], (char *)sp[-1]));
#endif
        }
        aux = (const AuxInfo *) sp;

        pAUX_base = pAUX_entry = pAUX_execfd = NULL;
        pAUX_phdr = pAUX_phent = pAUX_phnum = NULL;
        pAUX_euid = pAUX_ruid = pAUX_egid = pAUX_rgid = NULL;
        pAUX_pagesz = NULL;

        execname = NULL;

        /* Digest the auxiliary vector. */
        for (auxp = aux; auxp->a_type != AT_NULL; ++auxp) {
                switch (auxp->a_type) {
                case AT_BASE:
                        pAUX_base = auxp;
                        break;
                case AT_ENTRY:
                        pAUX_entry = auxp;
                        break;
                case AT_EXECFD:
                        pAUX_execfd = auxp;
                        break;
                case AT_PHDR:
                        pAUX_phdr = auxp;
                        break;
                case AT_PHENT:
                        pAUX_phent = auxp;
                        break;
                case AT_PHNUM:
                        pAUX_phnum = auxp;
                        break;
#ifdef AT_EUID
                case AT_EUID:
                        pAUX_euid = auxp;
                        break;
                case AT_RUID:
                        pAUX_ruid = auxp;
                        break;
                case AT_EGID:
                        pAUX_egid = auxp;
                        break;
                case AT_RGID:
                        pAUX_rgid = auxp;
                        break;
#endif
#ifdef AT_SUN_EXECNAME
                case AT_SUN_EXECNAME:
                        execname = (const char *)(const void *)auxp->a_v;
                        break;
#endif
                case AT_PAGESZ:
                        pAUX_pagesz = auxp;
                        break;
                }
        }

        /* Initialize and relocate ourselves. */
        if (pAUX_base == NULL) {
                _rtld_error("Bad pAUX_base");
                _rtld_die();
        }
        assert(pAUX_pagesz != NULL);
        _rtld_pagesz = (int)pAUX_pagesz->a_v;
        _rtld_init((caddr_t)pAUX_base->a_v, (caddr_t)relocbase, execname);

        __progname = _rtld_objself.path;
        environ = env;

        _rtld_trust = ((pAUX_euid ? (uid_t)pAUX_euid->a_v : geteuid()) ==
            (pAUX_ruid ? (uid_t)pAUX_ruid->a_v : getuid())) &&
            ((pAUX_egid ? (gid_t)pAUX_egid->a_v : getegid()) ==
            (pAUX_rgid ? (gid_t)pAUX_rgid->a_v : getgid()));

        ld_bind_now = getenv("LD_BIND_NOW");
        if (ld_bind_now != NULL && *ld_bind_now != '\0')
                bind_now = true;
        if (_rtld_trust) {
#ifdef DEBUG
                const char     *ld_debug = getenv("LD_DEBUG");
#ifdef RTLD_DEBUG
                debug = 0;
#endif
                if (ld_debug != NULL && *ld_debug != '\0')
                        debug = 1;
#endif
                _rtld_add_paths(execname, &_rtld_paths,
                    getenv("LD_LIBRARY_PATH"));
        } else {
                execname = NULL;
                if (unsetenv("LD_DEBUG") || unsetenv("LD_LIBRARY_PATH"))
                        _rtld_die();
        }
        _rtld_process_hints(execname, &_rtld_paths, &_rtld_xforms,
            _PATH_LD_HINTS);
        dbg(("dynamic linker is initialized, mapbase=%p, relocbase=%p",
             _rtld_objself.mapbase, _rtld_objself.relocbase));

        /*
         * Load the main program, or process its program header if it is
         * already loaded.
         */
        if (pAUX_execfd != NULL) {      /* Load the main program. */
                int             fd = pAUX_execfd->a_v;
                const char *obj_name = argv[0] ? argv[0] : "main program";
                dbg(("loading main program"));
                _rtld_objmain = _rtld_map_object(obj_name, fd, NULL);
                close(fd);
                if (_rtld_objmain == NULL)
                        _rtld_die();
        } else {                /* Main program already loaded. */
                const Elf_Phdr *phdr;
                int             phnum;
                caddr_t         entry;

                dbg(("processing main program's program header"));
                assert(pAUX_phdr != NULL);
                phdr = (const Elf_Phdr *) pAUX_phdr->a_v;
                assert(pAUX_phnum != NULL);
                phnum = pAUX_phnum->a_v;
                assert(pAUX_phent != NULL);
                assert(pAUX_phent->a_v == sizeof(Elf_Phdr));
                assert(pAUX_entry != NULL);
                entry = (caddr_t) pAUX_entry->a_v;
                _rtld_objmain = _rtld_digest_phdr(phdr, phnum, entry);
                _rtld_objmain->path = xstrdup(argv[0] ? argv[0] :
                    "main program");
                _rtld_objmain->pathlen = strlen(_rtld_objmain->path);
        }

        _rtld_objmain->mainprog = true;
        
        /*
         * Get the actual dynamic linker pathname from the executable if
         * possible.  (It should always be possible.)  That ensures that
         * gdb will find the right dynamic linker even if a non-standard
         * one is being used.
         */
        if (_rtld_objmain->interp != NULL &&
            strcmp(_rtld_objmain->interp, _rtld_objself.path) != 0)
                _rtld_objself.path = xstrdup(_rtld_objmain->interp);
        dbg(("actual dynamic linker is %s", _rtld_objself.path));
        
        _rtld_digest_dynamic(execname, _rtld_objmain);

        /* Link the main program into the list of objects. */
        *_rtld_objtail = _rtld_objmain;
        _rtld_objtail = &_rtld_objmain->next;

        _rtld_linkmap_add(_rtld_objmain);
        _rtld_linkmap_add(&_rtld_objself);

        ++_rtld_objmain->refcount;
        _rtld_objmain->mainref = 1;
        _rtld_objlist_push_tail(&_rtld_list_main, _rtld_objmain);

        if (_rtld_trust) {
                /*
                 * Pre-load user-specified objects after the main program
                 * but before any shared object dependencies.
                 */
                dbg(("preloading objects"));
                if (_rtld_preload(getenv("LD_PRELOAD")) == -1)
                        _rtld_die();
        } else
                if (unsetenv("LD_PRELOAD"))
                        _rtld_die();

        dbg(("loading needed objects"));
        if (_rtld_load_needed_objects(_rtld_objmain, RTLD_MAIN) == -1)
                _rtld_die();

        dbg(("relocating objects"));
        if (_rtld_relocate_objects(_rtld_objmain, bind_now) == -1)
                _rtld_die();

        dbg(("doing copy relocations"));
        if (_rtld_do_copy_relocations(_rtld_objmain) == -1)
                _rtld_die();

        /*
         * Set the __progname,  environ and, __mainprog_obj before
         * calling anything that might use them.
         */
        real___progname = _rtld_objmain_sym("__progname");
        if (real___progname) {
                if (argv[0] != NULL) {
                        if ((*real___progname = strrchr(argv[0], '/')) == NULL)
                                (*real___progname) = argv[0];
                        else
                                (*real___progname)++;
                } else {
                        (*real___progname) = NULL;
                }
        }
        real_environ = _rtld_objmain_sym("environ");
        if (real_environ)
                *real_environ = environ;
        /*
         * Set __mainprog_obj for old binaries.
         */
        real___mainprog_obj = _rtld_objmain_sym("__mainprog_obj");
        if (real___mainprog_obj)
                *real___mainprog_obj = _rtld_objmain;

        dbg(("calling _init functions"));
        _rtld_call_init_functions();

        dbg(("control at program entry point = %p, obj = %p, exit = %p",
             _rtld_objmain->entry, _rtld_objmain, _rtld_exit));

        /*
         * Return with the entry point and the exit procedure in at the top
         * of stack.
         */

        _rtld_debug_state();    /* say hello to gdb! */

        ((void **) osp)[0] = _rtld_exit;
        ((void **) osp)[1] = _rtld_objmain;
        return (Elf_Addr) _rtld_objmain->entry;
}

void
_rtld_die(void)
{
        const char *msg = dlerror();

        if (msg == NULL)
                msg = "Fatal error";
        xerrx(1, "%s", msg);
}

static Obj_Entry *
_rtld_dlcheck(void *handle)
{
        Obj_Entry *obj;

        for (obj = _rtld_objlist; obj != NULL; obj = obj->next)
                if (obj == (Obj_Entry *) handle)
                        break;

        if (obj == NULL || obj->dl_refcount == 0) {
                xwarnx("Invalid shared object handle %p", handle);
                return NULL;
        }
        return obj;
}

static void
_rtld_initlist_visit(Objlist* list, Obj_Entry *obj, int rev)
{
        Needed_Entry* elm;

        /* dbg(("_rtld_initlist_visit(%s)", obj->path)); */

        if (obj->init_done)
                return;
        obj->init_done = 1;

        for (elm = obj->needed; elm != NULL; elm = elm->next) {
                if (elm->obj != NULL) {
                        _rtld_initlist_visit(list, elm->obj, rev);
                }
        }

        if (rev) {
                _rtld_objlist_push_head(list, obj);
        } else {
                _rtld_objlist_push_tail(list, obj);
        }
}

static void
_rtld_initlist_tsort(Objlist* list, int rev)
{
        dbg(("_rtld_initlist_tsort"));

        Obj_Entry* obj;

        for (obj = _rtld_objlist->next; obj; obj = obj->next) {
                obj->init_done = 0;
        }

        for (obj = _rtld_objlist->next; obj; obj = obj->next) {
                _rtld_initlist_visit(list, obj, rev);
        }
}

static void
_rtld_init_dag(Obj_Entry *root)
{

        _rtld_init_dag1(root, root);
}

static void
_rtld_init_dag1(Obj_Entry *root, Obj_Entry *obj)
{
        const Needed_Entry *needed;

        if (!obj->mainref) {
                if (_rtld_objlist_find(&obj->dldags, root))
                        return;
                rdbg(("add %p (%s) to %p (%s) DAG", obj, obj->path, root,
                    root->path));
                _rtld_objlist_push_tail(&obj->dldags, root);
                _rtld_objlist_push_tail(&root->dagmembers, obj);
        }
        for (needed = obj->needed; needed != NULL; needed = needed->next)
                if (needed->obj != NULL)
                        _rtld_init_dag1(root, needed->obj);
}

/*
 * Note, this is called only for objects loaded by dlopen().
 */
static void
_rtld_unload_object(Obj_Entry *root, bool do_fini_funcs)
{

        _rtld_unref_dag(root);
        if (root->refcount == 0) { /* We are finished with some objects. */
                Obj_Entry *obj;
                Obj_Entry **linkp;
                Objlist_Entry *elm;

                /* Finalize objects that are about to be unmapped. */
                if (do_fini_funcs)
                        _rtld_call_fini_functions(0);

                /* Remove the DAG from all objects' DAG lists. */
                SIMPLEQ_FOREACH(elm, &root->dagmembers, link)
                        _rtld_objlist_remove(&elm->obj->dldags, root);

                /* Remove the DAG from the RTLD_GLOBAL list. */
                if (root->globalref) {
                        root->globalref = 0;
                        _rtld_objlist_remove(&_rtld_list_global, root);
                }

                /* Unmap all objects that are no longer referenced. */
                linkp = &_rtld_objlist->next;
                while ((obj = *linkp) != NULL) {
                        if (obj->refcount == 0) {
#ifdef RTLD_DEBUG
                                dbg(("unloading \"%s\"", obj->path));
#endif
                                if (obj->ehdr != MAP_FAILED)
                                        munmap(obj->ehdr, _rtld_pagesz);
                                munmap(obj->mapbase, obj->mapsize);
                                _rtld_objlist_remove(&_rtld_list_global, obj);
                                _rtld_linkmap_delete(obj);
                                *linkp = obj->next;
                                _rtld_obj_free(obj);
                        } else
                                linkp = &obj->next;
                }
                _rtld_objtail = linkp;
        }
}

static void
_rtld_unref_dag(Obj_Entry *root)
{

        assert(root);
        assert(root->refcount != 0);
        --root->refcount;
        if (root->refcount == 0) {
                const Needed_Entry *needed;

                for (needed = root->needed; needed != NULL;
                     needed = needed->next) {
                        if (needed->obj != NULL)
                                _rtld_unref_dag(needed->obj);
                }
        }
}

__strong_alias(__dlclose,dlclose)
int
dlclose(void *handle)
{
        Obj_Entry *root = _rtld_dlcheck(handle);

        if (root == NULL)
                return -1;

        _rtld_debug.r_state = RT_DELETE;
        _rtld_debug_state();

        --root->dl_refcount;
        _rtld_unload_object(root, true);

        _rtld_debug.r_state = RT_CONSISTENT;
        _rtld_debug_state();

        return 0;
}

__strong_alias(__dlerror,dlerror)
char *
dlerror(void)
{
        char *msg = error_message;

        error_message = NULL;
        return msg;
}

__strong_alias(__dlopen,dlopen)
void *
dlopen(const char *name, int mode)
{
        Obj_Entry **old_obj_tail = _rtld_objtail;
        Obj_Entry *obj = NULL;

        _rtld_debug.r_state = RT_ADD;
        _rtld_debug_state();

        if (name == NULL) {
                obj = _rtld_objmain;
                obj->refcount++;
        } else
                obj = _rtld_load_library(name, _rtld_objmain, mode);

        if (obj != NULL) {
                ++obj->dl_refcount;
                if (*old_obj_tail != NULL) {    /* We loaded something new. */
                        assert(*old_obj_tail == obj);

                        if (_rtld_load_needed_objects(obj, mode) == -1 ||
                            (_rtld_init_dag(obj),
                            _rtld_relocate_objects(obj,
                            ((mode & 3) == RTLD_NOW))) == -1) {
                                _rtld_unload_object(obj, false);
                                obj->dl_refcount--;
                                obj = NULL;
                        } else {
                                _rtld_call_init_functions();
                        }
                }
        }
        _rtld_debug.r_state = RT_CONSISTENT;
        _rtld_debug_state();

        return obj;
}

/*
 * Find a symbol in the main program.
 */
void *
_rtld_objmain_sym(const char *name)
{
        unsigned long hash;
        const Elf_Sym *def;
        const Obj_Entry *obj;

        hash = _rtld_elf_hash(name);
        obj = _rtld_objmain;

        def = _rtld_symlook_list(name, hash, &_rtld_list_main, &obj, false);

        if (def != NULL)
                return obj->relocbase + def->st_value;
        return(NULL);
}

#ifdef __powerpc__
static void *
hackish_return_address(void)
{
        return __builtin_return_address(1);
}
#endif

__strong_alias(__dlsym,dlsym)
void *
dlsym(void *handle, const char *name)
{
        const Obj_Entry *obj;
        unsigned long hash;
        const Elf_Sym *def;
        const Obj_Entry *defobj;
        void *retaddr;
        
        hash = _rtld_elf_hash(name);
        def = NULL;
        defobj = NULL;
        
        switch ((intptr_t)handle) {
        case (intptr_t)NULL:
        case (intptr_t)RTLD_NEXT:
        case (intptr_t)RTLD_DEFAULT:
        case (intptr_t)RTLD_SELF:
#ifdef __powerpc__
                retaddr = hackish_return_address();
#else
                retaddr = __builtin_return_address(0);
#endif
                if ((obj = _rtld_obj_from_addr(retaddr)) == NULL) {
                        _rtld_error("Cannot determine caller's shared object");
                        return NULL;
                }

                switch ((intptr_t)handle) {
                case (intptr_t)NULL:     /* Just the caller's shared object. */
                        def = _rtld_symlook_obj(name, hash, obj, false);
                        defobj = obj;
                        break;

                case (intptr_t)RTLD_NEXT:       /* Objects after callers */
                        obj = obj->next;
                        /*FALLTHROUGH*/

                case (intptr_t)RTLD_SELF:       /* Caller included */
                        for (; obj; obj = obj->next) {
                                if ((def = _rtld_symlook_obj(name, hash, obj,
                                    false)) != NULL) {
                                        defobj = obj;
                                        break;
                                }
                        }
                        break;

                case (intptr_t)RTLD_DEFAULT:
                        def = _rtld_symlook_default(name, hash, obj, &defobj,
                            false);
                        break;

                default:
                        abort();
                }
                break;

        default:
                if ((obj = _rtld_dlcheck(handle)) == NULL)
                        return NULL;
                
                if (obj->mainprog) {
                        /* Search main program and all libraries loaded by it */
                        def = _rtld_symlook_list(name, hash, &_rtld_list_main,
                            &defobj, false);
                } else {
                        Needed_Entry fake;

                        /* Search the object and all the libraries loaded by it. */
                        fake.next = NULL;
                        fake.obj = __UNCONST(obj);
                        fake.name = 0;
                        def = _rtld_symlook_needed(name, hash, &fake, &defobj,
                            false);
                }
                break;
        }
        
        if (def != NULL) {
#ifdef __HAVE_FUNCTION_DESCRIPTORS
                if (ELF_ST_TYPE(def->st_info) == STT_FUNC)
                        return (void *)_rtld_function_descriptor_alloc(defobj, 
                            def, 0);
#endif /* __HAVE_FUNCTION_DESCRIPTORS */
                return defobj->relocbase + def->st_value;
        }
        
        _rtld_error("Undefined symbol \"%s\"", name);
        return NULL;
}

__strong_alias(__dladdr,dladdr)
int
dladdr(const void *addr, Dl_info *info)
{
        const Obj_Entry *obj;
        const Elf_Sym *def, *best_def;
        void *symbol_addr;
        unsigned long symoffset;
        
#ifdef __HAVE_FUNCTION_DESCRIPTORS
        addr = _rtld_function_descriptor_function(addr);
#endif /* __HAVE_FUNCTION_DESCRIPTORS */

        obj = _rtld_obj_from_addr(addr);
        if (obj == NULL) {
                _rtld_error("No shared object contains address");
                return 0;
        }
        info->dli_fname = obj->path;
        info->dli_fbase = obj->mapbase;
        info->dli_saddr = (void *)0;
        info->dli_sname = NULL;
        
        /*
         * Walk the symbol list looking for the symbol whose address is
         * closest to the address sent in.
         */
        best_def = NULL;
        for (symoffset = 0; symoffset < obj->nchains; symoffset++) {
                def = obj->symtab + symoffset;

                /*
                 * For skip the symbol if st_shndx is either SHN_UNDEF or
                 * SHN_COMMON.
                 */
                if (def->st_shndx == SHN_UNDEF || def->st_shndx == SHN_COMMON)
                        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.
                 */
                symbol_addr = obj->relocbase + def->st_value;
                if (symbol_addr > addr || symbol_addr < info->dli_saddr)
                        continue;

                /* Update our idea of the nearest symbol. */
                info->dli_sname = obj->strtab + def->st_name;
                info->dli_saddr = symbol_addr;
                best_def = def;

                /* Exact match? */
                if (info->dli_saddr == addr)
                        break;
        }

#ifdef __HAVE_FUNCTION_DESCRIPTORS
        if (best_def != NULL && ELF_ST_TYPE(best_def->st_info) == STT_FUNC)
                info->dli_saddr = (void *)_rtld_function_descriptor_alloc(obj, 
                    best_def, 0);
#endif /* __HAVE_FUNCTION_DESCRIPTORS */

        return 1;
}

__strong_alias(__dlinfo,dlinfo)
int
dlinfo(void *handle, int req, void *v)
{
        const Obj_Entry *obj;
        void *retaddr;

        if (handle == RTLD_SELF) {
#ifdef __powerpc__
                retaddr = hackish_return_address();
#else
                retaddr = __builtin_return_address(0);
#endif
                if ((obj = _rtld_obj_from_addr(retaddr)) == NULL) {
                        _rtld_error("Cannot determine caller's shared object");
                        return -1;
                }
        } else {
                if ((obj = _rtld_dlcheck(handle)) == NULL) {
                        _rtld_error("Invalid handle");
                        return -1;
                }
        }

        switch (req) {
        case RTLD_DI_LINKMAP:
                {
                const struct link_map **map = v;

                *map = &obj->linkmap;
                break;
                }

        default:
                _rtld_error("Invalid request");
                return -1;
        }

        return 0;
}

/*
 * Error reporting function.  Use it like printf.  If formats the message
 * into a buffer, and sets things up so that the next call to dlerror()
 * will return the message.
 */
void
_rtld_error(const char *fmt,...)
{
        static char     buf[512];
        va_list         ap;

        va_start(ap, fmt);
        xvsnprintf(buf, sizeof buf, fmt, ap);
        error_message = buf;
        va_end(ap);
}

void
_rtld_debug_state(void)
{

        /* do nothing */
}

void
_rtld_linkmap_add(Obj_Entry *obj)
{
        struct link_map *l = &obj->linkmap;
        struct link_map *prev;

        obj->linkmap.l_name = obj->path;
        obj->linkmap.l_addr = obj->relocbase;
        obj->linkmap.l_ld = obj->dynamic;
#ifdef __mips__
        /* XXX This field is not standard and will be removed eventually. */
        obj->linkmap.l_offs = obj->relocbase;
#endif

        if (_rtld_debug.r_map == NULL) {
                _rtld_debug.r_map = l;
                return;
        }

        /*
         * Scan to the end of the list, but not past the entry for the
         * dynamic linker, which we want to keep at the very end.
         */
        for (prev = _rtld_debug.r_map;
            prev->l_next != NULL && prev->l_next != &_rtld_objself.linkmap;
            prev = prev->l_next);

        l->l_prev = prev;
        l->l_next = prev->l_next;
        if (l->l_next != NULL)
                l->l_next->l_prev = l;
        prev->l_next = l;
}

void
_rtld_linkmap_delete(Obj_Entry *obj)
{
        struct link_map *l = &obj->linkmap;

        if (l->l_prev == NULL) {
                if ((_rtld_debug.r_map = l->l_next) != NULL)
                        l->l_next->l_prev = NULL;
                return;
        }
        if ((l->l_prev->l_next = l->l_next) != NULL)
                l->l_next->l_prev = l->l_prev;
}

static Obj_Entry *
_rtld_obj_from_addr(const void *addr)
{
        Obj_Entry *obj;
        
        for (obj = _rtld_objlist;  obj != NULL;  obj = obj->next) {
                if (addr < (void *) obj->mapbase)
                        continue;
                if (addr < (void *) (obj->mapbase + obj->mapsize))
                        return obj;
        }
        return NULL;
}

static void
_rtld_objlist_clear(Objlist *list)
{
        while (!SIMPLEQ_EMPTY(list)) {
                Objlist_Entry* elm = SIMPLEQ_FIRST(list);
                SIMPLEQ_REMOVE_HEAD(list, link);
                xfree(elm);
        }
}

static void
_rtld_objlist_remove(Objlist *list, Obj_Entry *obj)
{
        Objlist_Entry *elm;
        
        if ((elm = _rtld_objlist_find(list, obj)) != NULL) {
                SIMPLEQ_REMOVE(list, elm, Struct_Objlist_Entry, link);
                xfree(elm);
        }
}