resolve.c revision 1.39 
1/*	$OpenBSD: resolve.c,v 1.39 2005/10/06 21:53:10 kurt 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	/* refcount handled in _dl_link_sub & _dl_boot */
157	object->refcount = 0;
158	TAILQ_INIT(&object->child_list);
159	object->opencount = 0;	/* # dlopen() & exe */
160	object->grprefcount = 0;
161	/* default dev, inode for dlopen-able objects. */
162	object->dev = 0;
163	object->inode = 0;
164	TAILQ_INIT(&object->dload_list);
165	TAILQ_INIT(&object->grpref_list);
166
167	return(object);
168}
169
170void
171_dl_tailq_free(struct dep_node *n)
172{
173	struct dep_node *next;
174
175	while (n != NULL) {
176		next = TAILQ_NEXT(n, next_sib);
177		_dl_free(n);
178		n = next;
179	}
180}
181
182elf_object_t *free_objects;
183
184void _dl_cleanup_objects(void);
185void
186_dl_cleanup_objects()
187{
188	elf_object_t *nobj, *head;
189	struct dep_node *n, *next;
190
191	n = TAILQ_FIRST(&_dlopened_child_list);
192	while (n != NULL) {
193		next = TAILQ_NEXT(n, next_sib);
194		if (n->data->opencount + n->data->grprefcount == 0) {
195			TAILQ_REMOVE(&_dlopened_child_list, n, next_sib);
196			_dl_free(n);
197		}
198		n = next;
199	}
200
201	head = free_objects;
202	free_objects = NULL;
203	while (head != NULL) {
204		if (head->load_name)
205			_dl_free(head->load_name);
206		_dl_tailq_free(TAILQ_FIRST(&head->dload_list));
207		_dl_tailq_free(TAILQ_FIRST(&head->child_list));
208		_dl_tailq_free(TAILQ_FIRST(&head->grpref_list));
209		nobj = head->next;
210		_dl_free(head);
211		head = nobj;
212	}
213}
214
215void
216_dl_remove_object(elf_object_t *object)
217{
218	elf_object_t *depobj;
219
220	object->prev->next = object->next;
221	if (object->next)
222		object->next->prev = object->prev;
223
224	if (_dl_last_object == object)
225		_dl_last_object = object->prev;
226
227	while ((depobj = object->dep_next)) {
228		object->dep_next = object->dep_next->dep_next;
229		_dl_free(depobj);
230	}
231
232	object->next = free_objects;
233	free_objects = object;
234}
235
236
237elf_object_t *
238_dl_lookup_object(const char *name)
239{
240	elf_object_t *object;
241
242	object = _dl_objects;
243	while (object) {
244		if (_dl_strcmp(name, object->load_name) == 0)
245			return(object);
246		object = object->next;
247	}
248	return(0);
249}
250
251int _dl_find_symbol_obj(elf_object_t *object, const char *name,
252    unsigned long hash, int flags, const Elf_Sym **ref,
253    const Elf_Sym **weak_sym,
254    elf_object_t **weak_object);
255
256sym_cache *_dl_symcache;
257int _dl_symcachestat_hits;
258int _dl_symcachestat_lookups;
259
260Elf_Addr
261_dl_find_symbol_bysym(elf_object_t *req_obj, unsigned int symidx,
262    const Elf_Sym **this, int flags, const Elf_Sym *ref_sym, const elf_object_t **pobj)
263{
264	Elf_Addr ret;
265	const Elf_Sym *sym;
266	const char *symn;
267	const elf_object_t *sobj;
268
269	_dl_symcachestat_lookups ++;
270	if (_dl_symcache != NULL &&
271	    symidx < req_obj->nchains &&
272	    _dl_symcache[symidx].obj != NULL &&
273	    _dl_symcache[symidx].sym != NULL &&
274	    _dl_symcache[symidx].flags == flags) {
275
276		_dl_symcachestat_hits++;
277		sobj = _dl_symcache[symidx].obj;
278		*this = _dl_symcache[symidx].sym;
279		if (pobj)
280			*pobj = sobj;
281		return sobj->load_offs;
282	}
283
284	sym = req_obj->dyn.symtab;
285	sym += symidx;
286	symn = req_obj->dyn.strtab + sym->st_name;
287
288	ret = _dl_find_symbol(symn, this, flags, ref_sym, req_obj, &sobj);
289
290	if (pobj)
291		*pobj = sobj;
292
293	if (_dl_symcache != NULL && symidx < req_obj->nchains) {
294		_dl_symcache[symidx].sym = *this;
295		_dl_symcache[symidx].obj = sobj;
296		_dl_symcache[symidx].flags = flags;
297	}
298
299	return ret;
300}
301
302Elf_Addr
303_dl_find_symbol(const char *name, const Elf_Sym **this,
304    int flags, const Elf_Sym *ref_sym, elf_object_t *req_obj,
305    const elf_object_t **pobj)
306{
307	const Elf_Sym *weak_sym = NULL;
308	unsigned long h = 0;
309	const char *p = name;
310	elf_object_t *object = NULL, *weak_object = NULL;
311	int found = 0;
312	struct dep_node *n, *m;
313
314
315	while (*p) {
316		unsigned long g;
317		h = (h << 4) + *p++;
318		if ((g = h & 0xf0000000))
319			h ^= g >> 24;
320		h &= ~g;
321	}
322
323	if (req_obj->dyn.symbolic)
324		if (_dl_find_symbol_obj(req_obj, name, h, flags, this, &weak_sym,
325		    &weak_object)) {
326			object = req_obj;
327			found = 1;
328			goto found;
329		}
330
331	if (flags & SYM_SEARCH_OBJ) {
332		if (_dl_find_symbol_obj(req_obj, name, h, flags, this,
333		    &weak_sym, &weak_object)) {
334			object = req_obj;
335			found = 1;
336		}
337	} else if (flags & SYM_DLSYM) {
338		if (_dl_find_symbol_obj(req_obj, name, h, flags, this,
339		    &weak_sym, &weak_object)) {
340			object = req_obj;
341			found = 1;
342		}
343		if (weak_object != NULL && found == 0) {
344			object=weak_object;
345			*this = weak_sym;
346			found = 1;
347		}
348		/* search dlopened obj and all children */
349
350		if (found == 0) {
351			TAILQ_FOREACH(n, &req_obj->load_object->dload_list,
352			    next_sib) {
353				if (_dl_find_symbol_obj(n->data, name, h,
354				    flags, this,
355				    &weak_sym, &weak_object)) {
356					object = n->data;
357					found = 1;
358					break;
359				}
360			}
361		}
362	} else {
363		int skip = 0;
364
365		if ((flags & SYM_SEARCH_SELF) || (flags & SYM_SEARCH_NEXT))
366			skip = 1;
367
368		/*
369		 * search dlopened objects: global or req_obj == dlopened_obj
370		 * and and it's children
371		 */
372		TAILQ_FOREACH(n, &_dlopened_child_list, next_sib) {
373			if (((n->data->obj_flags & RTLD_GLOBAL) == 0) &&
374			    (n->data != req_obj->load_object))
375				continue;
376
377			TAILQ_FOREACH(m, &n->data->dload_list, next_sib) {
378				if (skip == 1) {
379					if (m->data == req_obj) {
380						skip = 0;
381						if (flags & SYM_SEARCH_NEXT)
382							continue;
383					} else
384						continue;
385				}
386				if ((flags & SYM_SEARCH_OTHER) &&
387				    (m->data == req_obj))
388					continue;
389				if (_dl_find_symbol_obj(m->data, name, h, flags,
390				    this, &weak_sym, &weak_object)) {
391					object = m->data;
392					found = 1;
393					goto found;
394				}
395			}
396		}
397	}
398
399found:
400	if (weak_object != NULL && found == 0) {
401		object=weak_object;
402		*this = weak_sym;
403		found = 1;
404	}
405
406
407	if (found == 0) {
408		if ((ref_sym == NULL ||
409		    (ELF_ST_BIND(ref_sym->st_info) != STB_WEAK)) &&
410		    (flags & SYM_WARNNOTFOUND))
411			_dl_printf("%s:%s: undefined symbol '%s'\n",
412			    _dl_progname, req_obj->load_name, name);
413		return (0);
414	}
415
416	if (ref_sym != NULL && ref_sym->st_size != 0 &&
417	    (ref_sym->st_size != (*this)->st_size)  &&
418	    (ELF_ST_TYPE((*this)->st_info) != STT_FUNC) ) {
419		_dl_printf("%s:%s: %s : WARNING: "
420		    "symbol(%s) size mismatch, relink your program\n",
421		    _dl_progname, req_obj->load_name,
422		    object->load_name, name);
423	}
424
425	if (pobj)
426		*pobj = object;
427
428	return (object->load_offs);
429}
430
431int
432_dl_find_symbol_obj(elf_object_t *object, const char *name, unsigned long hash,
433    int flags, const Elf_Sym **this, const Elf_Sym **weak_sym,
434    elf_object_t **weak_object)
435{
436	const Elf_Sym	*symt = object->dyn.symtab;
437	const char	*strt = object->dyn.strtab;
438	long	si;
439	const char *symn;
440
441	for (si = object->buckets[hash % object->nbuckets];
442	    si != STN_UNDEF; si = object->chains[si]) {
443		const Elf_Sym *sym = symt + si;
444
445		if (sym->st_value == 0)
446			continue;
447
448		if (ELF_ST_TYPE(sym->st_info) != STT_NOTYPE &&
449		    ELF_ST_TYPE(sym->st_info) != STT_OBJECT &&
450		    ELF_ST_TYPE(sym->st_info) != STT_FUNC)
451			continue;
452
453		symn = strt + sym->st_name;
454		if (sym != *this && _dl_strcmp(symn, name))
455			continue;
456
457		/* allow this symbol if we are referring to a function
458		 * which has a value, even if section is UNDEF.
459		 * this allows &func to refer to PLT as per the
460		 * ELF spec. st_value is checked above.
461		 * if flags has SYM_PLT set, we must have actual
462		 * symbol, so this symbol is skipped.
463		 */
464		if (sym->st_shndx == SHN_UNDEF) {
465			if ((flags & SYM_PLT) || sym->st_value == 0 ||
466			    ELF_ST_TYPE(sym->st_info) != STT_FUNC)
467				continue;
468		}
469
470		if (ELF_ST_BIND(sym->st_info) == STB_GLOBAL) {
471			*this = sym;
472			return 1;
473		} else if (ELF_ST_BIND(sym->st_info) == STB_WEAK) {
474			if (!*weak_sym) {
475				*weak_sym = sym;
476				*weak_object = object;
477			}
478		}
479	}
480	return 0;
481}
482