resolve.c revision 1.33 
1/*	$OpenBSD: resolve.c,v 1.33 2005/09/22 01:33:07 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 **this, int flags, const Elf_Sym *ref_sym, 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		*this = _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, this, flags, ref_sym, 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 = *this;
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 **this,
257    int flags, const Elf_Sym *ref_sym, elf_object_t *req_obj,
258    const elf_object_t **pobj)
259{
260	const Elf_Sym *weak_sym = NULL;
261	unsigned long h = 0;
262	const char *p = name;
263	elf_object_t *object = NULL, *weak_object = NULL;
264	int found = 0;
265	struct dep_node *n, *m;
266
267
268	while (*p) {
269		unsigned long g;
270		h = (h << 4) + *p++;
271		if ((g = h & 0xf0000000))
272			h ^= g >> 24;
273		h &= ~g;
274	}
275
276	if (req_obj->dyn.symbolic)
277		if (_dl_find_symbol_obj(req_obj, name, h, flags, this, &weak_sym,
278		    &weak_object)) {
279			object = req_obj;
280			found = 1;
281			goto found;
282		}
283
284	if (flags & SYM_SEARCH_OBJ) {
285		if (_dl_find_symbol_obj(req_obj, name, h, flags, this,
286		    &weak_sym, &weak_object)) {
287			object = req_obj;
288			found = 1;
289		}
290	} else if (flags & SYM_DLSYM) {
291		if (_dl_find_symbol_obj(req_obj, name, h, flags, this,
292		    &weak_sym, &weak_object)) {
293			object = req_obj;
294			found = 1;
295		}
296		if (weak_object != NULL && found == 0) {
297			object=weak_object;
298			*this = weak_sym;
299			found = 1;
300		}
301		/* search dlopened obj and all children */
302
303		if (found == 0) {
304			TAILQ_FOREACH(n, &req_obj->load_object->dload_list,
305			    next_sib) {
306				if (_dl_find_symbol_obj(n->data, name, h,
307				    flags, this,
308				    &weak_sym, &weak_object)) {
309					object = n->data;
310					found = 1;
311					break;
312				}
313			}
314		}
315	} else {
316		int skip = 0;
317
318		if ((flags & SYM_SEARCH_SELF) || (flags & SYM_SEARCH_NEXT))
319			skip = 1;
320
321		/*
322		 * search dlopened objects: global or req_obj == dlopened_obj
323		 * and and it's children
324		 */
325		TAILQ_FOREACH(n, &_dlopened_child_list, next_sib) {
326			if (((n->data->obj_flags & RTLD_GLOBAL) == 0) &&
327			    (n->data != req_obj->load_object))
328				continue;
329
330			TAILQ_FOREACH(m, &n->data->dload_list, next_sib) {
331				if (skip == 1) {
332					if (m->data == req_obj) {
333						skip = 0;
334						if (flags & SYM_SEARCH_NEXT)
335							continue;
336					} else
337						continue;
338				}
339				if ((flags & SYM_SEARCH_OTHER) &&
340				    (m->data == req_obj))
341					continue;
342				if (_dl_find_symbol_obj(m->data, name, h, flags,
343				    this, &weak_sym, &weak_object)) {
344					object = m->data;
345					found = 1;
346					goto found;
347				}
348			}
349		}
350	}
351
352found:
353	if (weak_object != NULL && found == 0) {
354		object=weak_object;
355		*this = weak_sym;
356		found = 1;
357	}
358
359
360	if (found == 0) {
361		if ((ref_sym == NULL ||
362		    (ELF_ST_BIND(ref_sym->st_info) != STB_WEAK)) &&
363		    (flags & SYM_WARNNOTFOUND))
364			_dl_printf("%s:%s: undefined symbol '%s'\n",
365			    _dl_progname, req_obj->load_name, name);
366		return (0);
367	}
368
369	if (ref_sym != NULL && ref_sym->st_size != 0 &&
370	    (ref_sym->st_size != (*this)->st_size)  &&
371	    (ELF_ST_TYPE((*this)->st_info) != STT_FUNC) ) {
372		_dl_printf("%s:%s: %s : WARNING: "
373		    "symbol(%s) size mismatch, relink your program\n",
374		    _dl_progname, req_obj->load_name,
375		    object->load_name, name);
376	}
377
378	if (pobj)
379		*pobj = object;
380
381	return (object->load_offs);
382}
383
384int
385_dl_find_symbol_obj(elf_object_t *object, const char *name, unsigned long hash,
386    int flags, const Elf_Sym **this, const Elf_Sym **weak_sym,
387    elf_object_t **weak_object)
388{
389	const Elf_Sym	*symt = object->dyn.symtab;
390	const char	*strt = object->dyn.strtab;
391	long	si;
392	const char *symn;
393
394	for (si = object->buckets[hash % object->nbuckets];
395	    si != STN_UNDEF; si = object->chains[si]) {
396		const Elf_Sym *sym = symt + si;
397
398		if (sym->st_value == 0)
399			continue;
400
401		if (ELF_ST_TYPE(sym->st_info) != STT_NOTYPE &&
402		    ELF_ST_TYPE(sym->st_info) != STT_OBJECT &&
403		    ELF_ST_TYPE(sym->st_info) != STT_FUNC)
404			continue;
405
406		symn = strt + sym->st_name;
407		if (sym != *this && _dl_strcmp(symn, name))
408			continue;
409
410		/* allow this symbol if we are referring to a function
411		 * which has a value, even if section is UNDEF.
412		 * this allows &func to refer to PLT as per the
413		 * ELF spec. st_value is checked above.
414		 * if flags has SYM_PLT set, we must have actual
415		 * symbol, so this symbol is skipped.
416		 */
417		if (sym->st_shndx == SHN_UNDEF) {
418			if ((flags & SYM_PLT) || sym->st_value == 0 ||
419			    ELF_ST_TYPE(sym->st_info) != STT_FUNC)
420				continue;
421		}
422
423		if (ELF_ST_BIND(sym->st_info) == STB_GLOBAL) {
424			*this = sym;
425			return 1;
426		} else if (ELF_ST_BIND(sym->st_info) == STB_WEAK) {
427			if (!*weak_sym) {
428				*weak_sym = sym;
429				*weak_object = object;
430			}
431		}
432	}
433	return 0;
434}
435