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      1 /*	$NetBSD: load.c,v 1.49 2020/09/21 16:08:57 kamil Exp $	 */
      2 
      3 /*
      4  * Copyright 1996 John D. Polstra.
      5  * Copyright 1996 Matt Thomas <matt (at) 3am-software.com>
      6  * Copyright 2002 Charles M. Hannum <root (at) ihack.net>
      7  * All rights reserved.
      8  *
      9  * Redistribution and use in source and binary forms, with or without
     10  * modification, are permitted provided that the following conditions
     11  * are met:
     12  * 1. Redistributions of source code must retain the above copyright
     13  *    notice, this list of conditions and the following disclaimer.
     14  * 2. Redistributions in binary form must reproduce the above copyright
     15  *    notice, this list of conditions and the following disclaimer in the
     16  *    documentation and/or other materials provided with the distribution.
     17  * 3. All advertising materials mentioning features or use of this software
     18  *    must display the following acknowledgement:
     19  *      This product includes software developed by John Polstra.
     20  * 4. The name of the author may not be used to endorse or promote products
     21  *    derived from this software without specific prior written permission.
     22  *
     23  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
     24  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
     25  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
     26  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
     27  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
     28  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
     29  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
     30  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     31  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
     32  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     33  */
     34 
     35 /*
     36  * Dynamic linker for ELF.
     37  *
     38  * John Polstra <jdp (at) polstra.com>.
     39  */
     40 
     41 #include <sys/cdefs.h>
     42 #ifndef lint
     43 __RCSID("$NetBSD: load.c,v 1.49 2020/09/21 16:08:57 kamil Exp $");
     44 #endif /* not lint */
     45 
     46 #include <sys/types.h>
     47 #include <sys/param.h>
     48 #include <sys/mman.h>
     49 #include <sys/sysctl.h>
     50 #include <sys/stat.h>
     51 
     52 #include <err.h>
     53 #include <errno.h>
     54 #include <fcntl.h>
     55 #include <stdarg.h>
     56 #include <stdio.h>
     57 #include <stdlib.h>
     58 #include <string.h>
     59 #include <unistd.h>
     60 #include <dirent.h>
     61 
     62 #include "debug.h"
     63 #include "rtld.h"
     64 
     65 static bool _rtld_load_by_name(const char *, Obj_Entry *, Needed_Entry **,
     66     int);
     67 
     68 #ifdef RTLD_LOADER
     69 Objlist _rtld_list_main =	/* Objects loaded at program startup */
     70   SIMPLEQ_HEAD_INITIALIZER(_rtld_list_main);
     71 Objlist _rtld_list_global =	/* Objects dlopened with RTLD_GLOBAL */
     72   SIMPLEQ_HEAD_INITIALIZER(_rtld_list_global);
     73 
     74 void
     75 _rtld_objlist_push_head(Objlist *list, Obj_Entry *obj)
     76 {
     77 	Objlist_Entry *elm;
     78 
     79 	elm = NEW(Objlist_Entry);
     80 	elm->obj = obj;
     81 	SIMPLEQ_INSERT_HEAD(list, elm, link);
     82 }
     83 
     84 void
     85 _rtld_objlist_push_tail(Objlist *list, Obj_Entry *obj)
     86 {
     87 	Objlist_Entry *elm;
     88 
     89 	elm = NEW(Objlist_Entry);
     90 	elm->obj = obj;
     91 	SIMPLEQ_INSERT_TAIL(list, elm, link);
     92 }
     93 
     94 Objlist_Entry *
     95 _rtld_objlist_find(Objlist *list, const Obj_Entry *obj)
     96 {
     97 	Objlist_Entry *elm;
     98 
     99 	SIMPLEQ_FOREACH(elm, list, link) {
    100 		if (elm->obj == obj)
    101 			return elm;
    102 	}
    103 	return NULL;
    104 }
    105 #endif
    106 
    107 /*
    108  * Load a shared object into memory, if it is not already loaded.
    109  *
    110  * Returns a pointer to the Obj_Entry for the object.  Returns NULL
    111  * on failure.
    112  */
    113 Obj_Entry *
    114 _rtld_load_object(const char *filepath, int flags)
    115 {
    116 	Obj_Entry *obj;
    117 	int fd = -1;
    118 	struct stat sb;
    119 	size_t pathlen = strlen(filepath);
    120 
    121 	for (obj = _rtld_objlist->next; obj != NULL; obj = obj->next)
    122 		if (pathlen == obj->pathlen && !strcmp(obj->path, filepath))
    123 			break;
    124 
    125 	/*
    126 	 * If we didn't find a match by pathname, open the file and check
    127 	 * again by device and inode.  This avoids false mismatches caused
    128 	 * by multiple links or ".." in pathnames.
    129 	 *
    130 	 * To avoid a race, we open the file and use fstat() rather than
    131 	 * using stat().
    132 	 */
    133 	if (obj == NULL) {
    134 		if ((fd = open(filepath, O_RDONLY)) == -1) {
    135 			_rtld_error("Cannot open \"%s\"", filepath);
    136 			return NULL;
    137 		}
    138 		if (fstat(fd, &sb) == -1) {
    139 			_rtld_error("Cannot fstat \"%s\"", filepath);
    140 			close(fd);
    141 			return NULL;
    142 		}
    143 		for (obj = _rtld_objlist->next; obj != NULL; obj = obj->next) {
    144 			if (obj->ino == sb.st_ino && obj->dev == sb.st_dev) {
    145 				close(fd);
    146 				break;
    147 			}
    148 		}
    149 	}
    150 
    151 #ifdef RTLD_LOADER
    152 	if (pathlen == _rtld_objself.pathlen &&
    153 	    strcmp(_rtld_objself.path, filepath) == 0) {
    154 		close(fd);
    155 		return &_rtld_objself;
    156 	}
    157 #endif
    158 
    159 	if (obj == NULL) { /* First use of this object, so we must map it in */
    160 		obj = _rtld_map_object(filepath, fd, &sb);
    161 		(void)close(fd);
    162 		if (obj == NULL)
    163 			return NULL;
    164 		_rtld_digest_dynamic(filepath, obj);
    165 
    166 		if (flags & _RTLD_DLOPEN) {
    167 			if (obj->z_noopen || (flags & _RTLD_NOLOAD)) {
    168 				dbg(("refusing to load non-loadable \"%s\"",
    169 				    obj->path));
    170 				_rtld_error("Cannot dlopen non-loadable %s",
    171 				    obj->path);
    172 				munmap(obj->mapbase, obj->mapsize);
    173 				_rtld_obj_free(obj);
    174 				return OBJ_ERR;
    175 			}
    176 		}
    177 
    178 		*_rtld_objtail = obj;
    179 		_rtld_objtail = &obj->next;
    180 		_rtld_objcount++;
    181 		_rtld_objloads++;
    182 #ifdef RTLD_LOADER
    183 		_rtld_linkmap_add(obj);	/* for the debugger */
    184 #endif
    185 		dbg(("  %p .. %p: %s", obj->mapbase,
    186 		    obj->mapbase + obj->mapsize - 1, obj->path));
    187 		if (obj->textrel)
    188 			dbg(("  WARNING: %s has impure text", obj->path));
    189 	}
    190 
    191 	++obj->refcount;
    192 #ifdef RTLD_LOADER
    193 	if (flags & _RTLD_MAIN && !obj->mainref) {
    194 		obj->mainref = 1;
    195 		dbg(("adding %p (%s) to _rtld_list_main", obj, obj->path));
    196 		_rtld_objlist_push_tail(&_rtld_list_main, obj);
    197 	}
    198 	if (flags & _RTLD_GLOBAL && !obj->globalref) {
    199 		obj->globalref = 1;
    200 		dbg(("adding %p (%s) to _rtld_list_global", obj, obj->path));
    201 		_rtld_objlist_push_tail(&_rtld_list_global, obj);
    202 	}
    203 #endif
    204 	return obj;
    205 }
    206 
    207 static bool
    208 _rtld_load_by_name(const char *name, Obj_Entry *obj, Needed_Entry **needed,
    209     int flags)
    210 {
    211 	Library_Xform *x = _rtld_xforms;
    212 	Obj_Entry *o;
    213 	size_t j;
    214 	ssize_t i;
    215 	bool got = false;
    216 	union {
    217 		int i;
    218 		u_quad_t q;
    219 		char s[16];
    220 	} val;
    221 
    222 	dbg(("load by name %s %p", name, x));
    223 	for (o = _rtld_objlist->next; o != NULL; o = o->next)
    224 		if (_rtld_object_match_name(o, name)) {
    225 			++o->refcount;
    226 			(*needed)->obj = o;
    227 			return true;
    228 		}
    229 
    230 	for (; x; x = x->next) {
    231 		if (strcmp(x->name, name) != 0)
    232 			continue;
    233 
    234 		j = sizeof(val);
    235 		if ((i = _rtld_sysctl(x->ctlname, &val, &j)) == -1) {
    236 			xwarnx(_PATH_LD_HINTS ": invalid/unknown sysctl for %s (%d)",
    237 			    name, errno);
    238 			break;
    239 		}
    240 
    241 		switch (i) {
    242 		case CTLTYPE_QUAD:
    243 			xsnprintf(val.s, sizeof(val.s), "%" PRIu64, val.q);
    244 			break;
    245 		case CTLTYPE_INT:
    246 			xsnprintf(val.s, sizeof(val.s), "%d", val.i);
    247 			break;
    248 		case CTLTYPE_STRING:
    249 			break;
    250 		default:
    251 			xwarnx("unsupported sysctl type %d", (int)i);
    252 			break;
    253 		}
    254 
    255 		dbg(("sysctl returns %s", val.s));
    256 
    257 		for (i = 0; i < RTLD_MAX_ENTRY && x->entry[i].value != NULL;
    258 		    i++) {
    259 			dbg(("entry %ld", (unsigned long)i));
    260 			if (strcmp(x->entry[i].value, val.s) == 0)
    261 				break;
    262 		}
    263 
    264 		if (i == RTLD_MAX_ENTRY) {
    265 			xwarnx("sysctl value %s not found for lib%s",
    266 			    val.s, name);
    267 			break;
    268 		}
    269 
    270 		for (j = 0; j < RTLD_MAX_LIBRARY &&
    271 		    x->entry[i].library[j] != NULL; j++) {
    272 			o = _rtld_load_library(x->entry[i].library[j], obj,
    273 			    flags);
    274 			if (o == NULL) {
    275 				xwarnx("could not load %s for %s",
    276 				    x->entry[i].library[j], name);
    277 				continue;
    278 			}
    279 			got = true;
    280 			if (j == 0)
    281 				(*needed)->obj = o;
    282 			else {
    283 				/* make a new one and put it in the chain */
    284 				Needed_Entry *ne = xmalloc(sizeof(*ne));
    285 				ne->name = (*needed)->name;
    286 				ne->obj = o;
    287 				ne->next = (*needed)->next;
    288 				(*needed)->next = ne;
    289 				*needed = ne;
    290 			}
    291 
    292 		}
    293 
    294 	}
    295 
    296 	if (got)
    297 		return true;
    298 
    299 	return ((*needed)->obj = _rtld_load_library(name, obj, flags)) != NULL;
    300 }
    301 
    302 
    303 /*
    304  * Given a shared object, traverse its list of needed objects, and load
    305  * each of them.  Returns 0 on success.  Generates an error message and
    306  * returns -1 on failure.
    307  */
    308 int
    309 _rtld_load_needed_objects(Obj_Entry *first, int flags)
    310 {
    311 	Obj_Entry *obj;
    312 	int status = 0;
    313 
    314 	for (obj = first; obj != NULL; obj = obj->next) {
    315 		Needed_Entry *needed;
    316 
    317 		for (needed = obj->needed; needed != NULL;
    318 		    needed = needed->next) {
    319 			const char *name = obj->strtab + needed->name;
    320 #ifdef RTLD_LOADER
    321 			Obj_Entry *nobj;
    322 #endif
    323 			if (!_rtld_load_by_name(name, obj, &needed,
    324 			    flags & ~_RTLD_NOLOAD))
    325 				status = -1;	/* FIXME - cleanup */
    326 #ifdef RTLD_LOADER
    327 			if (status == -1)
    328 				return status;
    329 
    330 			if (flags & _RTLD_MAIN)
    331 				continue;
    332 
    333 			nobj = needed->obj;
    334 			if (nobj->z_nodelete && !obj->ref_nodel) {
    335 				dbg(("obj %s nodelete", nobj->path));
    336 				_rtld_ref_dag(nobj);
    337 				nobj->ref_nodel = true;
    338 			}
    339 #endif
    340 		}
    341 	}
    342 
    343 	return status;
    344 }
    345 
    346 #ifdef RTLD_LOADER
    347 int
    348 _rtld_preload(const char *preload_path)
    349 {
    350 	const char *path;
    351 	char *cp, *buf;
    352 	int status = 0;
    353 
    354 	if (preload_path != NULL && *preload_path != '\0') {
    355 		cp = buf = xstrdup(preload_path);
    356 		while ((path = strsep(&cp, " :")) != NULL && status == 0) {
    357 			if (!_rtld_load_object(path, _RTLD_MAIN))
    358 				status = -1;
    359 			else
    360 				dbg((" preloaded \"%s\"", path));
    361 		}
    362 		xfree(buf);
    363 	}
    364 
    365 	return status;
    366 }
    367 #endif
    368