resolve.c revision 1.29 
1/*	$OpenBSD: resolve.c,v 1.29 2005/09/16 23:41:05 drahn Exp $ */
2
3/*
4 * Copyright (c) 1998 Per Fogelstrom, Opsycon AB
5 *
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
8 * are met:
9 * 1. Redistributions of source code must retain the above copyright
10 *    notice, this list of conditions and the following disclaimer.
11 * 2. Redistributions in binary form must reproduce the above copyright
12 *    notice, this list of conditions and the following disclaimer in the
13 *    documentation and/or other materials provided with the distribution.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS
16 * OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
17 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
18 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
19 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
20 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
21 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
22 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
23 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
24 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
25 * SUCH DAMAGE.
26 *
27 */
28
29#define _DYN_LOADER
30
31#include <sys/types.h>
32
33#include <nlist.h>
34#include <link.h>
35#include "syscall.h"
36#include "archdep.h"
37#include "resolve.h"
38
39elf_object_t *_dl_objects;
40elf_object_t *_dl_last_object;
41elf_object_t *_dl_loading_object;
42
43/*
44 * Add a new dynamic object to the object list.
45 */
46void
47_dl_add_object(elf_object_t *object)
48{
49
50	/*
51	 * if this is a new object, prev will be NULL
52	 * != NULL if an object already in the list
53	 * prev == NULL for the first item in the list, but that will
54	 * be the executable.
55	 */
56	if (object->prev != NULL)
57		return;
58
59	if (_dl_objects == NULL) {			/* First object ? */
60		_dl_last_object = _dl_objects = object;
61	} else {
62		_dl_last_object->next = object;
63		object->prev = _dl_last_object;
64		_dl_last_object = object;
65	}
66}
67
68/*
69 * Initialize a new dynamic object.
70 */
71elf_object_t *
72_dl_finalize_object(const char *objname, Elf_Dyn *dynp, const long *dl_data,
73    const int objtype, const long laddr, const long loff)
74{
75	elf_object_t *object;
76#if 0
77	_dl_printf("objname [%s], dynp %p, dl_data %p, objtype %x laddr %lx, loff %lx\n",
78	    objname, dynp, dl_data, objtype, laddr, loff);
79#endif
80	object = _dl_malloc(sizeof(elf_object_t));
81	object->prev = object->next = NULL;
82
83	object->load_dyn = dynp;
84	while (dynp->d_tag != DT_NULL) {
85		if (dynp->d_tag < DT_NUM)
86			object->Dyn.info[dynp->d_tag] = dynp->d_un.d_val;
87		else if (dynp->d_tag >= DT_LOPROC &&
88		    dynp->d_tag < DT_LOPROC + DT_NUM)
89			object->Dyn.info[dynp->d_tag + DT_NUM - DT_LOPROC] =
90			    dynp->d_un.d_val;
91		if (dynp->d_tag == DT_TEXTREL)
92			object->dyn.textrel = 1;
93		if (dynp->d_tag == DT_SYMBOLIC)
94			object->dyn.symbolic = 1;
95		if (dynp->d_tag == DT_BIND_NOW)
96			object->dyn.bind_now = 1;
97		dynp++;
98	}
99
100	/*
101	 *  Now relocate all pointer to dynamic info, but only
102	 *  the ones which have pointer values.
103	 */
104	if (object->Dyn.info[DT_PLTGOT])
105		object->Dyn.info[DT_PLTGOT] += loff;
106	if (object->Dyn.info[DT_HASH])
107		object->Dyn.info[DT_HASH] += loff;
108	if (object->Dyn.info[DT_STRTAB])
109		object->Dyn.info[DT_STRTAB] += loff;
110	if (object->Dyn.info[DT_SYMTAB])
111		object->Dyn.info[DT_SYMTAB] += loff;
112	if (object->Dyn.info[DT_RELA])
113		object->Dyn.info[DT_RELA] += loff;
114	if (object->Dyn.info[DT_SONAME])
115		object->Dyn.info[DT_SONAME] += loff;
116	if (object->Dyn.info[DT_RPATH])
117		object->Dyn.info[DT_RPATH] += object->Dyn.info[DT_STRTAB];
118	if (object->Dyn.info[DT_REL])
119		object->Dyn.info[DT_REL] += loff;
120	if (object->Dyn.info[DT_INIT])
121		object->Dyn.info[DT_INIT] += loff;
122	if (object->Dyn.info[DT_FINI])
123		object->Dyn.info[DT_FINI] += loff;
124	if (object->Dyn.info[DT_JMPREL])
125		object->Dyn.info[DT_JMPREL] += loff;
126
127	if (object->Dyn.info[DT_HASH] != 0) {
128		Elf_Word *hashtab = (Elf_Word *)object->Dyn.info[DT_HASH];
129
130		object->nbuckets = hashtab[0];
131		object->nchains = hashtab[1];
132		object->buckets = hashtab + 2;
133		object->chains = object->buckets + object->nbuckets;
134	}
135
136	if (dl_data) {
137		object->phdrp = (Elf_Phdr *) dl_data[AUX_phdr];
138		object->phdrc = dl_data[AUX_phnum];
139	}
140	object->obj_type = objtype;
141	object->load_addr = laddr;
142	object->load_offs = loff;
143	object->load_name = _dl_strdup(objname);
144	if (_dl_loading_object == NULL) {
145		/*
146		 * no loading object, object is the loading object,
147		 * as it is either executable, or dlopened()
148		 */
149		_dl_loading_object = object->load_object = object;
150		DL_DEB(("head %s\n", object->load_name ));
151	} else {
152		object->load_object = _dl_loading_object;
153	}
154	DL_DEB(("obj %s has %s as head\n", object->load_name,
155	    _dl_loading_object->load_name ));
156	object->refcount = 1;
157	TAILQ_INIT(&object->child_list);
158	/* default dev, inode for dlopen-able objects. */
159	object->dev = 0;
160	object->inode = 0;
161	TAILQ_INIT(&object->dload_list);
162
163	return(object);
164}
165
166void
167_dl_remove_object(elf_object_t *object)
168{
169	elf_object_t *depobj;
170
171	object->prev->next = object->next;
172	if (object->next)
173		object->next->prev = object->prev;
174
175	if (_dl_last_object == object)
176		_dl_last_object = object->prev;
177
178	if (object->load_name)
179		_dl_free(object->load_name);
180
181	while ((depobj = object->dep_next)) {
182		object->dep_next = object->dep_next->dep_next;
183		_dl_free(depobj);
184	}
185	_dl_free(object);
186}
187
188
189elf_object_t *
190_dl_lookup_object(const char *name)
191{
192	elf_object_t *object;
193
194	object = _dl_objects;
195	while (object) {
196		if (_dl_strcmp(name, object->load_name) == 0)
197			return(object);
198		object = object->next;
199	}
200	return(0);
201}
202
203int _dl_find_symbol_obj(elf_object_t *object, const char *name,
204    unsigned long hash, int flags, const Elf_Sym **ref,
205    const Elf_Sym **weak_sym,
206    elf_object_t **weak_object);
207
208sym_cache *_dl_symcache;
209int _dl_symcachestat_hits;
210int _dl_symcachestat_lookups;
211
212Elf_Addr
213_dl_find_symbol_bysym(elf_object_t *req_obj, unsigned int symidx,
214    const Elf_Sym **ref, int flags, int req_size, const elf_object_t **pobj)
215{
216	Elf_Addr ret;
217	const Elf_Sym *sym;
218	const char *symn;
219	const elf_object_t *sobj;
220
221	_dl_symcachestat_lookups ++;
222	if ((_dl_symcache != NULL) &&
223	     (symidx < req_obj->nchains) &&
224	     (_dl_symcache[symidx].obj != NULL) &&
225	     (_dl_symcache[symidx].sym != NULL) &&
226	     (_dl_symcache[symidx].flags == flags)) {
227
228		_dl_symcachestat_hits++;
229		sobj = _dl_symcache[symidx].obj;
230		*ref = _dl_symcache[symidx].sym;
231		if (pobj)
232			*pobj = sobj;
233		return sobj->load_offs;
234	}
235
236	sym = req_obj->dyn.symtab;
237	sym += symidx;
238	symn = req_obj->dyn.strtab + sym->st_name;
239
240	ret = _dl_find_symbol(symn, ref, flags, req_size, req_obj, &sobj);
241
242	if (pobj)
243		*pobj = sobj;
244
245	if ((_dl_symcache != NULL) &&
246	     (symidx < req_obj->nchains)) {
247		_dl_symcache[symidx].sym = *ref;
248		_dl_symcache[symidx].obj = sobj;
249		_dl_symcache[symidx].flags = flags;
250	}
251
252	return ret;
253}
254
255Elf_Addr
256_dl_find_symbol(const char *name, const Elf_Sym **ref,
257    int flags, int req_size, elf_object_t *req_obj, const elf_object_t **pobj)
258{
259	const Elf_Sym *weak_sym = NULL;
260	unsigned long h = 0;
261	const char *p = name;
262	elf_object_t *object = NULL, *weak_object = NULL;
263	int found = 0;
264	struct dep_node *n, *m;
265
266
267	while (*p) {
268		unsigned long g;
269		h = (h << 4) + *p++;
270		if ((g = h & 0xf0000000))
271			h ^= g >> 24;
272		h &= ~g;
273	}
274
275	if (req_obj->dyn.symbolic)
276		if (_dl_find_symbol_obj(req_obj, name, h, flags, ref, &weak_sym,
277		    &weak_object)) {
278			object = req_obj;
279			found = 1;
280			goto found;
281		}
282
283	if (flags & SYM_SEARCH_OBJ) {
284		if (_dl_find_symbol_obj(req_obj, name, h, flags, ref,
285		    &weak_sym, &weak_object)) {
286			object = req_obj;
287			found = 1;
288		}
289	} else if ((flags & SYM_SEARCH_SELF) || (flags & SYM_SEARCH_NEXT)) {
290		/* search after req_obj in the objects's load group */
291		int skip = 1;
292
293		TAILQ_FOREACH(n, &req_obj->load_object->dload_list, next_sib) {
294
295			if (n->data == req_obj && skip == 1) {
296				skip = 0;
297				if (flags & SYM_SEARCH_NEXT)
298					continue;
299			}
300			if (skip == 1)
301				continue;
302			if (_dl_find_symbol_obj(n->data, name, h, flags, ref,
303			    &weak_sym, &weak_object)) {
304				object = n->data;
305				found = 1;
306				break;
307			}
308		}
309	} else if (flags & SYM_DLSYM) {
310		if (_dl_find_symbol_obj(req_obj, name, h, flags, ref,
311		    &weak_sym, &weak_object)) {
312			object = req_obj;
313			found = 1;
314		}
315		if (weak_object != NULL && found == 0) {
316			object=weak_object;
317			*ref = weak_sym;
318			found = 1;
319		}
320		/* search dlopened obj and all children */
321
322		if (found == 0) {
323			TAILQ_FOREACH(n, &req_obj->load_object->dload_list,
324			    next_sib) {
325				if (_dl_find_symbol_obj(n->data, name, h,
326				    flags, ref,
327				    &weak_sym, &weak_object)) {
328					object = n->data;
329					found = 1;
330					break;
331				}
332			}
333		}
334	} else {
335		/* search main program and it's libs */
336		TAILQ_FOREACH(n, &_dl_objects->dload_list, next_sib) {
337			if ((flags & SYM_SEARCH_OTHER) &&
338			    (n->data == req_obj)) {
339				continue;
340			}
341
342			if (_dl_find_symbol_obj(n->data, name, h, flags,
343			    ref, &weak_sym, &weak_object)) {
344				object = n->data;
345				found = 1;
346				goto found;
347			}
348		}
349
350		/*
351		 * search dlopened objects: global or req_obj == dlopened_obj
352		 * and and it's children
353		 */
354		TAILQ_FOREACH(n, &_dlopened_child_list, next_sib) {
355			if (((n->data->obj_flags & RTLD_GLOBAL) == 0) &&
356			    (n->data != req_obj->load_object))
357				continue;
358
359			TAILQ_FOREACH(m, &n->data->dload_list, next_sib) {
360				if ((flags & SYM_SEARCH_OTHER) &&
361				    (m->data == req_obj))
362					continue;
363				if (_dl_find_symbol_obj(m->data, name, h, flags,
364				    ref, &weak_sym, &weak_object)) {
365					object = m->data;
366					found = 1;
367					break;
368				}
369			}
370		}
371	}
372
373found:
374	if (weak_object != NULL && found == 0) {
375		object=weak_object;
376		*ref = weak_sym;
377		found = 1;
378	}
379
380
381	if (found == 0) {
382		if (flags & SYM_WARNNOTFOUND)
383			_dl_printf("%s:%s: undefined symbol '%s'\n",
384			    _dl_progname, req_obj->load_name, name);
385		return (0);
386	}
387
388	if (req_size != (*ref)->st_size && req_size != 0 &&
389	    (ELF_ST_TYPE((*ref)->st_info) != STT_FUNC)) {
390		_dl_printf("%s:%s: %s : WARNING: "
391		    "symbol(%s) size mismatch, relink your program\n",
392		    _dl_progname, req_obj->load_name,
393		    object->load_name, name);
394	}
395
396	if (pobj)
397		*pobj = object;
398
399	return (object->load_offs);
400}
401
402int
403_dl_find_symbol_obj(elf_object_t *object, const char *name, unsigned long hash,
404    int flags, const Elf_Sym **ref, const Elf_Sym **weak_sym,
405    elf_object_t **weak_object)
406{
407	const Elf_Sym	*symt = object->dyn.symtab;
408	const char	*strt = object->dyn.strtab;
409	long	si;
410	const char *symn;
411
412	for (si = object->buckets[hash % object->nbuckets];
413	    si != STN_UNDEF; si = object->chains[si]) {
414		const Elf_Sym *sym = symt + si;
415
416		if (sym->st_value == 0)
417			continue;
418
419		if (ELF_ST_TYPE(sym->st_info) != STT_NOTYPE &&
420		    ELF_ST_TYPE(sym->st_info) != STT_OBJECT &&
421		    ELF_ST_TYPE(sym->st_info) != STT_FUNC)
422			continue;
423
424		symn = strt + sym->st_name;
425		if (sym != *ref && _dl_strcmp(symn, name))
426			continue;
427
428		/* allow this symbol if we are referring to a function
429		 * which has a value, even if section is UNDEF.
430		 * this allows &func to refer to PLT as per the
431		 * ELF spec. st_value is checked above.
432		 * if flags has SYM_PLT set, we must have actual
433		 * symbol, so this symbol is skipped.
434		 */
435		if (sym->st_shndx == SHN_UNDEF) {
436			if ((flags & SYM_PLT) || sym->st_value == 0 ||
437			    ELF_ST_TYPE(sym->st_info) != STT_FUNC)
438				continue;
439		}
440
441		if (ELF_ST_BIND(sym->st_info) == STB_GLOBAL) {
442			*ref = sym;
443			return 1;
444		} else if (ELF_ST_BIND(sym->st_info) == STB_WEAK) {
445			if (!*weak_sym) {
446				*weak_sym = sym;
447				*weak_object = object;
448			}
449		}
450	}
451	return 0;
452}
453