OpenGrok

/*	$NetBSD: load.c,v 1.52 2026/07/07 14:10:23 riastradh Exp $	 */

/*
 * Copyright 1996 John D. Polstra.
 * Copyright 1996 Matt Thomas <matt (at) 3am-software.com>
 * Copyright 2002 Charles M. Hannum <root (at) 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 (at) 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