resolve.c revision 1.49 
1/*	$OpenBSD: resolve.c,v 1.49 2008/05/05 02:29:02 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#include "dl_prebind.h"
39
40elf_object_t *_dl_objects;
41elf_object_t *_dl_last_object;
42elf_object_t *_dl_loading_object;
43
44/*
45 * Add a new dynamic object to the object list.
46 */
47void
48_dl_add_object(elf_object_t *object)
49{
50
51	/*
52	 * if this is a new object, prev will be NULL
53	 * != NULL if an object already in the list
54	 * prev == NULL for the first item in the list, but that will
55	 * be the executable.
56	 */
57	if (object->prev != NULL)
58		return;
59
60	if (_dl_objects == NULL) {			/* First object ? */
61		_dl_last_object = _dl_objects = object;
62	} else {
63		_dl_last_object->next = object;
64		object->prev = _dl_last_object;
65		_dl_last_object = object;
66	}
67}
68
69/*
70 * Initialize a new dynamic object.
71 */
72elf_object_t *
73_dl_finalize_object(const char *objname, Elf_Dyn *dynp, Elf_Phdr *phdrp,
74    int phdrc, const int objtype, const long lbase, const long obase)
75{
76	elf_object_t *object;
77#if 0
78	_dl_printf("objname [%s], dynp %p, objtype %x lbase %lx, obase %lx\n",
79	    objname, dynp, objtype, lbase, obase);
80#endif
81	object = _dl_malloc(sizeof(elf_object_t));
82	object->prev = object->next = NULL;
83
84	object->load_dyn = dynp;
85	while (dynp->d_tag != DT_NULL) {
86		if (dynp->d_tag < DT_NUM)
87			object->Dyn.info[dynp->d_tag] = dynp->d_un.d_val;
88		else if (dynp->d_tag >= DT_LOPROC &&
89		    dynp->d_tag < DT_LOPROC + DT_PROCNUM)
90			object->Dyn.info[dynp->d_tag + DT_NUM - DT_LOPROC] =
91			    dynp->d_un.d_val;
92		if (dynp->d_tag == DT_TEXTREL)
93			object->dyn.textrel = 1;
94		if (dynp->d_tag == DT_SYMBOLIC)
95			object->dyn.symbolic = 1;
96		if (dynp->d_tag == DT_BIND_NOW)
97			object->obj_flags = RTLD_NOW;
98		dynp++;
99	}
100
101	/*
102	 *  Now relocate all pointer to dynamic info, but only
103	 *  the ones which have pointer values.
104	 */
105	if (object->Dyn.info[DT_PLTGOT])
106		object->Dyn.info[DT_PLTGOT] += obase;
107	if (object->Dyn.info[DT_HASH])
108		object->Dyn.info[DT_HASH] += obase;
109	if (object->Dyn.info[DT_STRTAB])
110		object->Dyn.info[DT_STRTAB] += obase;
111	if (object->Dyn.info[DT_SYMTAB])
112		object->Dyn.info[DT_SYMTAB] += obase;
113	if (object->Dyn.info[DT_RELA])
114		object->Dyn.info[DT_RELA] += obase;
115	if (object->Dyn.info[DT_SONAME])
116		object->Dyn.info[DT_SONAME] += obase;
117	if (object->Dyn.info[DT_RPATH])
118		object->Dyn.info[DT_RPATH] += object->Dyn.info[DT_STRTAB];
119	if (object->Dyn.info[DT_REL])
120		object->Dyn.info[DT_REL] += obase;
121	if (object->Dyn.info[DT_INIT])
122		object->Dyn.info[DT_INIT] += obase;
123	if (object->Dyn.info[DT_FINI])
124		object->Dyn.info[DT_FINI] += obase;
125	if (object->Dyn.info[DT_JMPREL])
126		object->Dyn.info[DT_JMPREL] += obase;
127
128	if (object->Dyn.info[DT_HASH] != 0) {
129		Elf_Word *hashtab = (Elf_Word *)object->Dyn.info[DT_HASH];
130
131		object->nbuckets = hashtab[0];
132		object->nchains = hashtab[1];
133		object->buckets = hashtab + 2;
134		object->chains = object->buckets + object->nbuckets;
135	}
136
137	object->phdrp = phdrp;
138	object->phdrc = phdrc;
139	object->obj_type = objtype;
140	object->load_base = lbase;
141	object->obj_base = obase;
142	object->load_name = _dl_strdup(objname);
143	if (_dl_loading_object == NULL) {
144		/*
145		 * no loading object, object is the loading object,
146		 * as it is either executable, or dlopened()
147		 */
148		_dl_loading_object = object->load_object = object;
149		DL_DEB(("head %s\n", object->load_name ));
150	} else {
151		object->load_object = _dl_loading_object;
152	}
153	DL_DEB(("obj %s has %s as head\n", object->load_name,
154	    _dl_loading_object->load_name ));
155	object->refcount = 0;
156	TAILQ_INIT(&object->child_list);
157	object->opencount = 0;	/* # dlopen() & exe */
158	object->grprefcount = 0;
159	/* default dev, inode for dlopen-able objects. */
160	object->dev = 0;
161	object->inode = 0;
162	TAILQ_INIT(&object->grpsym_list);
163	TAILQ_INIT(&object->grpref_list);
164
165	return(object);
166}
167
168void
169_dl_tailq_free(struct dep_node *n)
170{
171	struct dep_node *next;
172
173	while (n != NULL) {
174		next = TAILQ_NEXT(n, next_sib);
175		_dl_free(n);
176		n = next;
177	}
178}
179
180elf_object_t *free_objects;
181
182void _dl_cleanup_objects(void);
183void
184_dl_cleanup_objects()
185{
186	elf_object_t *nobj, *head;
187	struct dep_node *n, *next;
188
189	n = TAILQ_FIRST(&_dlopened_child_list);
190	while (n != NULL) {
191		next = TAILQ_NEXT(n, next_sib);
192		if (OBJECT_DLREF_CNT(n->data) == 0) {
193			TAILQ_REMOVE(&_dlopened_child_list, n, next_sib);
194			_dl_free(n);
195		}
196		n = next;
197	}
198
199	head = free_objects;
200	free_objects = NULL;
201	while (head != NULL) {
202		if (head->load_name)
203			_dl_free(head->load_name);
204		_dl_tailq_free(TAILQ_FIRST(&head->grpsym_list));
205		_dl_tailq_free(TAILQ_FIRST(&head->child_list));
206		_dl_tailq_free(TAILQ_FIRST(&head->grpref_list));
207		nobj = head->next;
208		_dl_free(head);
209		head = nobj;
210	}
211}
212
213void
214_dl_remove_object(elf_object_t *object)
215{
216	object->prev->next = object->next;
217	if (object->next)
218		object->next->prev = object->prev;
219
220	if (_dl_last_object == object)
221		_dl_last_object = object->prev;
222
223	object->next = free_objects;
224	free_objects = object;
225}
226
227
228elf_object_t *
229_dl_lookup_object(const char *name)
230{
231	elf_object_t *object;
232
233	object = _dl_objects;
234	while (object) {
235		if (_dl_strcmp(name, object->load_name) == 0)
236			return(object);
237		object = object->next;
238	}
239	return(0);
240}
241
242int _dl_find_symbol_obj(elf_object_t *object, const char *name,
243    unsigned long hash, int flags, const Elf_Sym **ref,
244    const Elf_Sym **weak_sym,
245    elf_object_t **weak_object);
246
247sym_cache *_dl_symcache;
248int _dl_symcachestat_hits;
249int _dl_symcachestat_lookups;
250
251
252Elf_Addr
253_dl_find_symbol_bysym(elf_object_t *req_obj, unsigned int symidx,
254    const Elf_Sym **this, int flags, const Elf_Sym *ref_sym, const elf_object_t **pobj)
255{
256	Elf_Addr ret;
257	const Elf_Sym *sym;
258	const char *symn;
259	const elf_object_t *sobj;
260
261	_dl_symcachestat_lookups ++;
262	if (_dl_symcache != NULL &&
263	    symidx < req_obj->nchains &&
264	    _dl_symcache[symidx].obj != NULL &&
265	    _dl_symcache[symidx].sym != NULL &&
266	    _dl_symcache[symidx].flags == flags) {
267
268		_dl_symcachestat_hits++;
269		sobj = _dl_symcache[symidx].obj;
270		*this = _dl_symcache[symidx].sym;
271		if (pobj)
272			*pobj = sobj;
273		if (_dl_prebind_validate) /* XXX */
274			prebind_validate(req_obj, symidx, flags, ref_sym);
275		return sobj->obj_base;
276	}
277
278	sym = req_obj->dyn.symtab;
279	sym += symidx;
280	symn = req_obj->dyn.strtab + sym->st_name;
281
282	ret = _dl_find_symbol(symn, this, flags, ref_sym, req_obj, &sobj);
283
284	if (pobj)
285		*pobj = sobj;
286
287	if (_dl_symcache != NULL && symidx < req_obj->nchains) {
288#if 0
289		DL_DEB(("cache miss %d %p %p, %p %p %s %s %d %d %s\n",
290		    symidx,
291		    _dl_symcache[symidx].sym, *this,
292		    _dl_symcache[symidx].obj, sobj, sobj->load_name,
293		    sobj->dyn.strtab + (*this)->st_name,
294		    _dl_symcache[symidx].flags, flags, req_obj->load_name));
295#endif
296
297		_dl_symcache[symidx].sym = *this;
298		_dl_symcache[symidx].obj = sobj;
299		_dl_symcache[symidx].flags = flags;
300	}
301
302	return ret;
303}
304
305Elf_Addr
306_dl_find_symbol(const char *name, const Elf_Sym **this,
307    int flags, const Elf_Sym *ref_sym, elf_object_t *req_obj,
308    const elf_object_t **pobj)
309{
310	const Elf_Sym *weak_sym = NULL;
311	unsigned long h = 0;
312	const char *p = name;
313	elf_object_t *object = NULL, *weak_object = NULL;
314	int found = 0;
315	struct dep_node *n, *m;
316
317
318	while (*p) {
319		unsigned long g;
320		h = (h << 4) + *p++;
321		if ((g = h & 0xf0000000))
322			h ^= g >> 24;
323		h &= ~g;
324	}
325
326	if (req_obj->dyn.symbolic)
327		if (_dl_find_symbol_obj(req_obj, name, h, flags, this, &weak_sym,
328		    &weak_object)) {
329			object = req_obj;
330			found = 1;
331			goto found;
332		}
333
334	if (flags & SYM_SEARCH_OBJ) {
335		if (_dl_find_symbol_obj(req_obj, name, h, flags, this,
336		    &weak_sym, &weak_object)) {
337			object = req_obj;
338			found = 1;
339		}
340	} else if (flags & SYM_DLSYM) {
341		if (_dl_find_symbol_obj(req_obj, name, h, flags, this,
342		    &weak_sym, &weak_object)) {
343			object = req_obj;
344			found = 1;
345		}
346		if (weak_object != NULL && found == 0) {
347			object=weak_object;
348			*this = weak_sym;
349			found = 1;
350		}
351		/* search dlopened obj and all children */
352
353		if (found == 0) {
354			TAILQ_FOREACH(n, &req_obj->load_object->grpsym_list,
355			    next_sib) {
356				if (_dl_find_symbol_obj(n->data, name, h,
357				    flags, this,
358				    &weak_sym, &weak_object)) {
359					object = n->data;
360					found = 1;
361					break;
362				}
363			}
364		}
365	} else {
366		int skip = 0;
367
368		if ((flags & SYM_SEARCH_SELF) || (flags & SYM_SEARCH_NEXT))
369			skip = 1;
370
371		/*
372		 * search dlopened objects: global or req_obj == dlopened_obj
373		 * and and it's children
374		 */
375		TAILQ_FOREACH(n, &_dlopened_child_list, next_sib) {
376			if (((n->data->obj_flags & RTLD_GLOBAL) == 0) &&
377			    (n->data != req_obj->load_object))
378				continue;
379
380			TAILQ_FOREACH(m, &n->data->grpsym_list, next_sib) {
381				if (skip == 1) {
382					if (m->data == req_obj) {
383						skip = 0;
384						if (flags & SYM_SEARCH_NEXT)
385							continue;
386					} else
387						continue;
388				}
389				if ((flags & SYM_SEARCH_OTHER) &&
390				    (m->data == req_obj))
391					continue;
392				if (_dl_find_symbol_obj(m->data, name, h, flags,
393				    this, &weak_sym, &weak_object)) {
394					object = m->data;
395					found = 1;
396					goto found;
397				}
398			}
399		}
400	}
401
402found:
403	if (weak_object != NULL && found == 0) {
404		object=weak_object;
405		*this = weak_sym;
406		found = 1;
407	}
408
409
410	if (found == 0) {
411		if ((ref_sym == NULL ||
412		    (ELF_ST_BIND(ref_sym->st_info) != STB_WEAK)) &&
413		    (flags & SYM_WARNNOTFOUND))
414			_dl_printf("%s:%s: undefined symbol '%s'\n",
415			    _dl_progname, req_obj->load_name, name);
416		return (0);
417	}
418
419	if (ref_sym != NULL && ref_sym->st_size != 0 &&
420	    (ref_sym->st_size != (*this)->st_size)  &&
421	    (ELF_ST_TYPE((*this)->st_info) != STT_FUNC) ) {
422		_dl_printf("%s:%s: %s : WARNING: "
423		    "symbol(%s) size mismatch, relink your program\n",
424		    _dl_progname, req_obj->load_name,
425		    object->load_name, name);
426	}
427
428	if (pobj)
429		*pobj = object;
430
431	return (object->obj_base);
432}
433
434int
435_dl_find_symbol_obj(elf_object_t *object, const char *name, unsigned long hash,
436    int flags, const Elf_Sym **this, const Elf_Sym **weak_sym,
437    elf_object_t **weak_object)
438{
439	const Elf_Sym	*symt = object->dyn.symtab;
440	const char	*strt = object->dyn.strtab;
441	long	si;
442	const char *symn;
443
444	for (si = object->buckets[hash % object->nbuckets];
445	    si != STN_UNDEF; si = object->chains[si]) {
446		const Elf_Sym *sym = symt + si;
447
448		if (sym->st_value == 0)
449			continue;
450
451		if (ELF_ST_TYPE(sym->st_info) != STT_NOTYPE &&
452		    ELF_ST_TYPE(sym->st_info) != STT_OBJECT &&
453		    ELF_ST_TYPE(sym->st_info) != STT_FUNC)
454			continue;
455
456		symn = strt + sym->st_name;
457		if (sym != *this && _dl_strcmp(symn, name))
458			continue;
459
460		/* allow this symbol if we are referring to a function
461		 * which has a value, even if section is UNDEF.
462		 * this allows &func to refer to PLT as per the
463		 * ELF spec. st_value is checked above.
464		 * if flags has SYM_PLT set, we must have actual
465		 * symbol, so this symbol is skipped.
466		 */
467		if (sym->st_shndx == SHN_UNDEF) {
468			if ((flags & SYM_PLT) || sym->st_value == 0 ||
469			    ELF_ST_TYPE(sym->st_info) != STT_FUNC)
470				continue;
471		}
472
473		if (ELF_ST_BIND(sym->st_info) == STB_GLOBAL) {
474			*this = sym;
475			return 1;
476		} else if (ELF_ST_BIND(sym->st_info) == STB_WEAK) {
477			if (!*weak_sym) {
478				*weak_sym = sym;
479				*weak_object = object;
480			}
481		}
482	}
483	return 0;
484}
485