/*      $NetBSD: load.c,v 1.52 2026/07/07 14:10:23 riastradh 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: load.c,v 1.52 2026/07/07 14:10:23 riastradh Exp $");
#endif /* not lint */

#include <sys/types.h>
#include <sys/param.h>
#include <sys/mman.h>
#include <sys/sysctl.h>
#include <sys/stat.h>

#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 <dirent.h>

#include "debug.h"
#include "rtld.h"

static bool _rtld_load_by_name(const char *, Obj_Entry *, Needed_Entry **,
    int, sigset_t *);

#ifdef RTLD_LOADER
Objlist _rtld_list_main =       /* Objects loaded at program startup */
  SIMPLEQ_HEAD_INITIALIZER(_rtld_list_main);
Objlist _rtld_list_global =     /* Objects dlopened with RTLD_GLOBAL */
  SIMPLEQ_HEAD_INITIALIZER(_rtld_list_global);

void
_rtld_objlist_push_head(Objlist *list, Obj_Entry *obj)
{
        Objlist_Entry *elm;

        elm = NEW(Objlist_Entry);
        elm->obj = obj;
        SIMPLEQ_INSERT_HEAD(list, elm, link);
}

void
_rtld_objlist_push_tail(Objlist *list, Obj_Entry *obj)
{
        Objlist_Entry *elm;

        elm = NEW(Objlist_Entry);
        elm->obj = obj;
        SIMPLEQ_INSERT_TAIL(list, elm, link);
}

Objlist_Entry *
_rtld_objlist_find(Objlist *list, const Obj_Entry *obj)
{
        Objlist_Entry *elm;

        SIMPLEQ_FOREACH(elm, list, link) {
                if (elm->obj == obj)
                        return elm;
        }
        return NULL;
}
#endif

/*
 * Load a shared object into memory, if it is not already loaded.
 *
 * Returns a pointer to the Obj_Entry for the object.  Returns NULL
 * on failure.
 */
Obj_Entry *
_rtld_load_object(const char *filepath, int flags, sigset_t *mask)
{
        Obj_Entry *obj;
        int fd = -1;
        struct stat sb;
        size_t pathlen = strlen(filepath);

restart:
        /*
         * Search the list of objects for a matching path.  If we find
         * a match, but it's concurrently running destructors, wait for
         * it with the rtld exclusive lock dropped and start over.
         */
        for (obj = _rtld_objlist->next; obj != NULL; obj = obj->next) {
                if (pathlen == obj->pathlen && !strcmp(obj->path, filepath)) {
                        if (__predict_false(_rtld_wait_for_fini(&obj, mask)))
                                goto restart;
                        assert(obj->refcount > 0);
                        break;
                }
        }

        /*
         * If we didn't find a match by pathname, open the file and check
         * again by device and inode.  This avoids false mismatches caused
         * by multiple links or ".." in pathnames.
         *
         * To avoid a race, we open the file and use fstat() rather than
         * using stat().
         */
        if (obj == NULL) {
                if ((fd = open(filepath, O_RDONLY)) == -1) {
                        _rtld_error("Cannot open \"%s\"", filepath);
                        return NULL;
                }
                if (fstat(fd, &sb) == -1) {
                        _rtld_error("Cannot fstat \"%s\"", filepath);
                        close(fd);
                        return NULL;
                }
                for (obj = _rtld_objlist->next; obj != NULL; obj = obj->next) {
                        if (obj->ino == sb.st_ino && obj->dev == sb.st_dev) {
                                close(fd);
                                if (__predict_false(_rtld_wait_for_fini(&obj,
                                            mask)))
                                        goto restart;
                                assert(obj->refcount > 0);
                                break;
                        }
                }
        }

#ifdef RTLD_LOADER
        if (pathlen == _rtld_objself.pathlen &&
            strcmp(_rtld_objself.path, filepath) == 0) {
                close(fd);
                assert(_rtld_objself.refcount > 0);
                return &_rtld_objself;
        }
#endif

        if (obj == NULL) { /* First use of this object, so we must map it in */
                obj = _rtld_map_object(filepath, fd, &sb);
                (void)close(fd);
                if (obj == NULL)
                        return NULL;
                _rtld_digest_dynamic(filepath, obj);

                if (flags & _RTLD_DLOPEN) {
                        if (obj->z_noopen || (flags & _RTLD_NOLOAD)) {
                                dbg(("refusing to load non-loadable \"%s\"",
                                    obj->path));
                                _rtld_error("Cannot dlopen non-loadable %s",
                                    obj->path);
                                munmap(obj->mapbase, obj->mapsize);
                                _rtld_obj_free(obj);
                                return OBJ_ERR;
                        }
                }

                *_rtld_objtail = obj;
                _rtld_objtail = &obj->next;
                _rtld_objgen++;
                _rtld_objcount++;
                _rtld_objloads++;
                _rtld_objrelocpending++;
#ifdef RTLD_LOADER
                _rtld_linkmap_add(obj); /* for the debugger */
#endif
                dbg(("  %p .. %p: %s", obj->mapbase,
                    obj->mapbase + obj->mapsize - 1, obj->path));
                if (obj->textrel)
                        dbg(("  WARNING: %s has impure text", obj->path));
        } else {
                assert(obj->refcount > 0);
        }

        ++obj->refcount;
#ifdef RTLD_LOADER
        if (flags & _RTLD_MAIN && !obj->mainref) {
                obj->mainref = 1;
                dbg(("adding %p (%s) to _rtld_list_main", obj, obj->path));
                _rtld_objlist_push_tail(&_rtld_list_main, obj);
        }
        if (flags & _RTLD_GLOBAL && !obj->globalref) {
                obj->globalref = 1;
                dbg(("adding %p (%s) to _rtld_list_global", obj, obj->path));
                _rtld_objlist_push_tail(&_rtld_list_global, obj);
        }
#endif
        assert(obj->refcount > 0);
        return obj;
}

static bool
_rtld_load_by_name(const char *name, Obj_Entry *obj, Needed_Entry **needed,
    int flags, sigset_t *mask)
{
        Library_Xform *x = _rtld_xforms;
        Obj_Entry *o;
        size_t j;
        ssize_t i;
        bool got = false;
        union {
                int i;
                u_quad_t q;
                char s[16];
        } val;

        /*
         * Caller must hold a reference to prevent concurrent dlclose
         * from unloading obj until we're done, even if we
         * unlock/wait/relock to wait for a dependency that is being
         * concurrently unloaded.
         */
        assert(obj->neededrefcount);

        dbg(("load by name %s %p", name, x));
restart:
        /*
         * Search the list of objects for a matching path.  If we find
         * a match, but it's concurrently running destructors, wait for
         * it with the rtld exclusive lock dropped and start over.
         */
        for (o = _rtld_objlist->next; o != NULL; o = o->next) {
                if (_rtld_object_match_name(o, name)) {
                        if (__predict_false(_rtld_wait_for_fini(&o, mask)))
                                goto restart;
                        assert(o->refcount > 0);
                        ++o->refcount;
                        (*needed)->obj = o;
                        return true;
                }
        }

        for (; x; x = x->next) {
                if (strcmp(x->name, name) != 0)
                        continue;

                j = sizeof(val);
                if ((i = _rtld_sysctl(x->ctlname, &val, &j)) == -1) {
                        xwarnx(_PATH_LD_HINTS ": invalid/unknown sysctl for %s (%d)",
                            name, errno);
                        break;
                }

                switch (i) {
                case CTLTYPE_QUAD:
                        xsnprintf(val.s, sizeof(val.s), "%" PRIu64, val.q);
                        break;
                case CTLTYPE_INT:
                        xsnprintf(val.s, sizeof(val.s), "%d", val.i);
                        break;
                case CTLTYPE_STRING:
                        break;
                default:
                        xwarnx("unsupported sysctl type %d", (int)i);
                        break;
                }

                dbg(("sysctl returns %s", val.s));

                for (i = 0; i < RTLD_MAX_ENTRY && x->entry[i].value != NULL;
                    i++) {
                        dbg(("entry %ld", (unsigned long)i));
                        if (strcmp(x->entry[i].value, val.s) == 0)
                                break;
                }

                if (i == RTLD_MAX_ENTRY) {
                        xwarnx("sysctl value %s not found for lib%s",
                            val.s, name);
                        break;
                }

                for (j = 0; j < RTLD_MAX_LIBRARY &&
                    x->entry[i].library[j] != NULL; j++) {
                        o = _rtld_load_library(x->entry[i].library[j], obj,
                            flags, mask);
                        if (o == NULL) {
                                xwarnx("could not load %s for %s",
                                    x->entry[i].library[j], name);
                                continue;
                        }
                        assert(o->refcount > 0);
                        got = true;
                        if (j == 0)
                                (*needed)->obj = o;
                        else {
                                /* make a new one and put it in the chain */
                                Needed_Entry *ne = xmalloc(sizeof(*ne));
                                ne->name = (*needed)->name;
                                ne->obj = o;
                                ne->next = (*needed)->next;
                                (*needed)->next = ne;
                                *needed = ne;
                        }

                }

        }

        if (got)
                return true;

        assert((*needed)->obj == NULL);
        (*needed)->obj = _rtld_load_library(name, obj, flags, mask);
        assert((*needed)->obj == NULL || (*needed)->obj->refcount > 0);
        return ((*needed)->obj != NULL);
}


/*
 * Given a shared object, traverse its list of needed objects, and load
 * each of them.  Returns 0 on success.  Generates an error message and
 * returns -1 on failure.
 */
int
_rtld_load_needed_objects(Obj_Entry *first, int flags, sigset_t *mask)
{
        Obj_Entry *obj;
        int status = 0;

        for (obj = first; obj != NULL; obj = obj->next) {
                Needed_Entry *needed;

                /*
                 * If obj is already being unloaded, there is no need
                 * to load its dependencies, so just skip it.
                 */
                if (__predict_false(obj->refcount == 0))
                        continue;

                /*
                 * Prevent obj from being concurrently unloaded until
                 * we're done.  We hold the rtld exclusive lock right
                 * now, but _rtld_load_by_name may drop it.
                 */
                _rtld_load_needed_enter(obj);

                for (needed = obj->needed; needed != NULL;
                    needed = needed->next) {
                        const char *name = obj->strtab + needed->name;
#ifdef RTLD_LOADER
                        Obj_Entry *nobj;
#endif
                        if (__predict_false(needed->obj != NULL))
                                continue;
                        if (!_rtld_load_by_name(name, obj, &needed,
                            flags & ~_RTLD_NOLOAD, mask))
                                status = -1;    /* FIXME - cleanup */
#ifdef RTLD_LOADER
                        if (status == -1)
                                break;

                        if (flags & _RTLD_MAIN)
                                continue;

                        nobj = needed->obj;
                        if (nobj->z_nodelete && !obj->ref_nodel) {
                                dbg(("obj %s nodelete", nobj->path));
                                _rtld_ref_dag(nobj);
                                nobj->ref_nodel = true;
                        }
#endif
                }

                /*
                 * Allow obj to be concurrently unloaded now that we're
                 * done loading its dependencies.
                 */
                _rtld_load_needed_exit(obj);

#ifdef RTLD_LOADER
                if (status == -1)
                        break;
#endif
        }

        return status;
}

#ifdef RTLD_LOADER
int
_rtld_preload(const char *preload_path, sigset_t *mask)
{
        const char *path;
        char *cp, *buf;
        int status = 0;

        if (preload_path != NULL && *preload_path != '\0') {
                cp = buf = xstrdup(preload_path);
                while ((path = strsep(&cp, " :")) != NULL && status == 0) {
                        if (!_rtld_load_object(path, _RTLD_MAIN, mask))
                                status = -1;
                        else
                                dbg((" preloaded \"%s\"", path));
                }
                xfree(buf);
        }

        return status;
}
#endif