resolve.c revision 1.57 
1/*	$OpenBSD: resolve.c,v 1.57 2011/11/28 20:59:03 guenther 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	/* if a .so is marked nodelete, then add a reference */
51	if (object->obj_flags & DF_1_NODELETE &&
52	    (object->status & STAT_NODELETE) == 0) {
53		DL_DEB(("objname %s is nodelete\n", object->load_name));
54		object->refcount++;
55		object->status |= STAT_NODELETE;
56	}
57
58	/*
59	 * if this is a new object, prev will be NULL
60	 * != NULL if an object already in the list
61	 * prev == NULL for the first item in the list, but that will
62	 * be the executable.
63	 */
64	if (object->prev != NULL)
65		return;
66
67	if (_dl_objects == NULL) {			/* First object ? */
68		_dl_last_object = _dl_objects = object;
69	} else {
70		_dl_last_object->next = object;
71		object->prev = _dl_last_object;
72		_dl_last_object = object;
73	}
74}
75
76/*
77 * Initialize a new dynamic object.
78 */
79elf_object_t *
80_dl_finalize_object(const char *objname, Elf_Dyn *dynp, Elf_Phdr *phdrp,
81    int phdrc, const int objtype, const long lbase, const long obase)
82{
83	elf_object_t *object;
84#if 0
85	_dl_printf("objname [%s], dynp %p, objtype %x lbase %lx, obase %lx\n",
86	    objname, dynp, objtype, lbase, obase);
87#endif
88	object = _dl_malloc(sizeof(elf_object_t));
89	object->prev = object->next = NULL;
90
91	object->load_dyn = dynp;
92	while (dynp->d_tag != DT_NULL) {
93		if (dynp->d_tag < DT_NUM)
94			object->Dyn.info[dynp->d_tag] = dynp->d_un.d_val;
95		else if (dynp->d_tag >= DT_LOPROC &&
96		    dynp->d_tag < DT_LOPROC + DT_PROCNUM)
97			object->Dyn.info[dynp->d_tag + DT_NUM - DT_LOPROC] =
98			    dynp->d_un.d_val;
99		if (dynp->d_tag == DT_TEXTREL)
100			object->dyn.textrel = 1;
101		if (dynp->d_tag == DT_SYMBOLIC)
102			object->dyn.symbolic = 1;
103		if (dynp->d_tag == DT_BIND_NOW)
104			object->obj_flags |= DF_1_NOW;
105		if (dynp->d_tag == DT_FLAGS_1)
106			object->obj_flags |= dynp->d_un.d_val;
107		dynp++;
108	}
109	DL_DEB((" flags %s = 0x%x\n", objname, object->obj_flags ));
110
111	/*
112	 *  Now relocate all pointer to dynamic info, but only
113	 *  the ones which have pointer values.
114	 */
115	if (object->Dyn.info[DT_PLTGOT])
116		object->Dyn.info[DT_PLTGOT] += obase;
117	if (object->Dyn.info[DT_HASH])
118		object->Dyn.info[DT_HASH] += obase;
119	if (object->Dyn.info[DT_STRTAB])
120		object->Dyn.info[DT_STRTAB] += obase;
121	if (object->Dyn.info[DT_SYMTAB])
122		object->Dyn.info[DT_SYMTAB] += obase;
123	if (object->Dyn.info[DT_RELA])
124		object->Dyn.info[DT_RELA] += obase;
125	if (object->Dyn.info[DT_SONAME])
126		object->Dyn.info[DT_SONAME] += object->Dyn.info[DT_STRTAB];
127	if (object->Dyn.info[DT_RPATH])
128		object->Dyn.info[DT_RPATH] += object->Dyn.info[DT_STRTAB];
129	if (object->Dyn.info[DT_REL])
130		object->Dyn.info[DT_REL] += obase;
131	if (object->Dyn.info[DT_INIT])
132		object->Dyn.info[DT_INIT] += obase;
133	if (object->Dyn.info[DT_FINI])
134		object->Dyn.info[DT_FINI] += obase;
135	if (object->Dyn.info[DT_JMPREL])
136		object->Dyn.info[DT_JMPREL] += obase;
137
138	if (object->Dyn.info[DT_HASH] != 0) {
139		Elf_Word *hashtab = (Elf_Word *)object->Dyn.info[DT_HASH];
140
141		object->nbuckets = hashtab[0];
142		object->nchains = hashtab[1];
143		object->buckets = hashtab + 2;
144		object->chains = object->buckets + object->nbuckets;
145	}
146
147	object->phdrp = phdrp;
148	object->phdrc = phdrc;
149	object->obj_type = objtype;
150	object->load_base = lbase;
151	object->obj_base = obase;
152	object->load_name = _dl_strdup(objname);
153	if (_dl_loading_object == NULL) {
154		/*
155		 * no loading object, object is the loading object,
156		 * as it is either executable, or dlopened()
157		 */
158		_dl_loading_object = object->load_object = object;
159		DL_DEB(("head %s\n", object->load_name ));
160	} else {
161		object->load_object = _dl_loading_object;
162	}
163	DL_DEB(("obj %s has %s as head\n", object->load_name,
164	    _dl_loading_object->load_name ));
165	object->refcount = 0;
166	TAILQ_INIT(&object->child_list);
167	object->opencount = 0;	/* # dlopen() & exe */
168	object->grprefcount = 0;
169	/* default dev, inode for dlopen-able objects. */
170	object->dev = 0;
171	object->inode = 0;
172	object->lastlookup = 0;
173	TAILQ_INIT(&object->grpsym_list);
174	TAILQ_INIT(&object->grpref_list);
175
176	return(object);
177}
178
179void
180_dl_tailq_free(struct dep_node *n)
181{
182	struct dep_node *next;
183
184	while (n != NULL) {
185		next = TAILQ_NEXT(n, next_sib);
186		_dl_free(n);
187		n = next;
188	}
189}
190
191elf_object_t *free_objects;
192
193void _dl_cleanup_objects(void);
194void
195_dl_cleanup_objects()
196{
197	elf_object_t *nobj, *head;
198	struct dep_node *n, *next;
199
200	n = TAILQ_FIRST(&_dlopened_child_list);
201	while (n != NULL) {
202		next = TAILQ_NEXT(n, next_sib);
203		if (OBJECT_DLREF_CNT(n->data) == 0) {
204			TAILQ_REMOVE(&_dlopened_child_list, n, next_sib);
205			_dl_free(n);
206		}
207		n = next;
208	}
209
210	head = free_objects;
211	free_objects = NULL;
212	while (head != NULL) {
213		if (head->load_name)
214			_dl_free(head->load_name);
215		if (head->sod.sod_name)
216			_dl_free((char *)head->sod.sod_name);
217		_dl_tailq_free(TAILQ_FIRST(&head->grpsym_list));
218		_dl_tailq_free(TAILQ_FIRST(&head->child_list));
219		_dl_tailq_free(TAILQ_FIRST(&head->grpref_list));
220		nobj = head->next;
221		_dl_free(head);
222		head = nobj;
223	}
224}
225
226void
227_dl_remove_object(elf_object_t *object)
228{
229	object->prev->next = object->next;
230	if (object->next)
231		object->next->prev = object->prev;
232
233	if (_dl_last_object == object)
234		_dl_last_object = object->prev;
235
236	object->next = free_objects;
237	free_objects = object;
238}
239
240
241int _dl_find_symbol_obj(elf_object_t *object, const char *name,
242    unsigned long hash, int flags, const Elf_Sym **ref,
243    const Elf_Sym **weak_sym,
244    elf_object_t **weak_object);
245
246sym_cache *_dl_symcache;
247int _dl_symcachestat_hits;
248int _dl_symcachestat_lookups;
249
250
251Elf_Addr
252_dl_find_symbol_bysym(elf_object_t *req_obj, unsigned int symidx,
253    const Elf_Sym **this, int flags, const Elf_Sym *ref_sym, const elf_object_t **pobj)
254{
255	Elf_Addr ret;
256	const Elf_Sym *sym;
257	const char *symn;
258	const elf_object_t *sobj;
259
260	_dl_symcachestat_lookups ++;
261	if (_dl_symcache != NULL &&
262	    symidx < req_obj->nchains &&
263	    _dl_symcache[symidx].obj != NULL &&
264	    _dl_symcache[symidx].sym != NULL &&
265	    _dl_symcache[symidx].flags == flags) {
266
267		_dl_symcachestat_hits++;
268		sobj = _dl_symcache[symidx].obj;
269		*this = _dl_symcache[symidx].sym;
270		if (pobj)
271			*pobj = sobj;
272		if (_dl_prebind_validate) /* XXX */
273			prebind_validate(req_obj, symidx, flags, ref_sym);
274		return sobj->obj_base;
275	}
276
277	sym = req_obj->dyn.symtab;
278	sym += symidx;
279	symn = req_obj->dyn.strtab + sym->st_name;
280
281	ret = _dl_find_symbol(symn, this, flags, ref_sym, req_obj, &sobj);
282
283	if (pobj)
284		*pobj = sobj;
285
286	if (_dl_symcache != NULL && symidx < req_obj->nchains) {
287#if 0
288		DL_DEB(("cache miss %d %p %p, %p %p %s %s %d %d %s\n",
289		    symidx,
290		    _dl_symcache[symidx].sym, *this,
291		    _dl_symcache[symidx].obj, sobj, sobj->load_name,
292		    sobj->dyn.strtab + (*this)->st_name,
293		    _dl_symcache[symidx].flags, flags, req_obj->load_name));
294#endif
295
296		_dl_symcache[symidx].sym = *this;
297		_dl_symcache[symidx].obj = sobj;
298		_dl_symcache[symidx].flags = flags;
299	}
300
301	return ret;
302}
303
304int _dl_searchnum = 0;
305void
306_dl_newsymsearch(void)
307{
308	_dl_searchnum += 1;
309
310	if (_dl_searchnum < 0) {
311		/*
312		 * If the signed number rolls over, reset all counters so
313		 * we dont get accidental collision.
314		 */
315		elf_object_t *walkobj;
316		for (walkobj = _dl_objects;
317		    walkobj != NULL;
318		    walkobj = walkobj->next) {
319			walkobj->lastlookup = 0;
320		}
321		_dl_searchnum = 1;
322	}
323}
324
325Elf_Addr
326_dl_find_symbol(const char *name, const Elf_Sym **this,
327    int flags, const Elf_Sym *ref_sym, elf_object_t *req_obj,
328    const elf_object_t **pobj)
329{
330	const Elf_Sym *weak_sym = NULL;
331	unsigned long h = 0;
332	const char *p = name;
333	elf_object_t *object = NULL, *weak_object = NULL;
334	int found = 0;
335	struct dep_node *n, *m;
336
337
338	while (*p) {
339		unsigned long g;
340		h = (h << 4) + *p++;
341		if ((g = h & 0xf0000000))
342			h ^= g >> 24;
343		h &= ~g;
344	}
345
346	if (req_obj->dyn.symbolic)
347		if (_dl_find_symbol_obj(req_obj, name, h, flags, this, &weak_sym,
348		    &weak_object)) {
349			object = req_obj;
350			found = 1;
351			goto found;
352		}
353
354	if (flags & SYM_SEARCH_OBJ) {
355		if (_dl_find_symbol_obj(req_obj, name, h, flags, this,
356		    &weak_sym, &weak_object)) {
357			object = req_obj;
358			found = 1;
359		}
360	} else if (flags & SYM_DLSYM) {
361		if (_dl_find_symbol_obj(req_obj, name, h, flags, this,
362		    &weak_sym, &weak_object)) {
363			object = req_obj;
364			found = 1;
365		}
366		if (weak_object != NULL && found == 0) {
367			object=weak_object;
368			*this = weak_sym;
369			found = 1;
370		}
371		/* search dlopened obj and all children */
372
373		if (found == 0) {
374			TAILQ_FOREACH(n, &req_obj->load_object->grpsym_list,
375			    next_sib) {
376				if (_dl_find_symbol_obj(n->data, name, h,
377				    flags, this,
378				    &weak_sym, &weak_object)) {
379					object = n->data;
380					found = 1;
381					break;
382				}
383			}
384		}
385	} else {
386		int skip = 0;
387
388		if ((flags & SYM_SEARCH_SELF) || (flags & SYM_SEARCH_NEXT))
389			skip = 1;
390
391		_dl_newsymsearch();
392
393		/*
394		 * search dlopened objects: global or req_obj == dlopened_obj
395		 * and and it's children
396		 */
397		TAILQ_FOREACH(n, &_dlopened_child_list, next_sib) {
398			if (((n->data->obj_flags & DF_1_GLOBAL) == 0) &&
399			    (n->data != req_obj->load_object))
400				continue;
401
402			n->data->lastlookup_head = _dl_searchnum;
403			TAILQ_FOREACH(m, &n->data->grpsym_list, next_sib) {
404				if (skip == 1) {
405					if (m->data == req_obj) {
406						skip = 0;
407						if (flags & SYM_SEARCH_NEXT)
408							continue;
409					} else
410						continue;
411				}
412				if ((flags & SYM_SEARCH_OTHER) &&
413				    (m->data == req_obj))
414					continue;
415				m->data->lastlookup = _dl_searchnum;
416				if (_dl_find_symbol_obj(m->data, name, h, flags,
417				    this, &weak_sym, &weak_object)) {
418					object = m->data;
419					found = 1;
420					goto found;
421				}
422			}
423		}
424	}
425
426found:
427	if (weak_object != NULL && found == 0) {
428		object=weak_object;
429		*this = weak_sym;
430		found = 1;
431	}
432
433
434	if (found == 0) {
435		if ((ref_sym == NULL ||
436		    (ELF_ST_BIND(ref_sym->st_info) != STB_WEAK)) &&
437		    (flags & SYM_WARNNOTFOUND))
438			_dl_printf("%s:%s: undefined symbol '%s'\n",
439			    _dl_progname, req_obj->load_name, name);
440		return (0);
441	}
442
443	if (ref_sym != NULL && ref_sym->st_size != 0 &&
444	    (ref_sym->st_size != (*this)->st_size)  &&
445	    (ELF_ST_TYPE((*this)->st_info) != STT_FUNC) ) {
446		_dl_printf("%s:%s: %s : WARNING: "
447		    "symbol(%s) size mismatch, relink your program\n",
448		    _dl_progname, req_obj->load_name,
449		    object->load_name, name);
450	}
451
452	if (pobj)
453		*pobj = object;
454
455	return (object->obj_base);
456}
457
458int
459_dl_find_symbol_obj(elf_object_t *object, const char *name, unsigned long hash,
460    int flags, const Elf_Sym **this, const Elf_Sym **weak_sym,
461    elf_object_t **weak_object)
462{
463	const Elf_Sym	*symt = object->dyn.symtab;
464	const char	*strt = object->dyn.strtab;
465	long	si;
466	const char *symn;
467
468	for (si = object->buckets[hash % object->nbuckets];
469	    si != STN_UNDEF; si = object->chains[si]) {
470		const Elf_Sym *sym = symt + si;
471
472		if (sym->st_value == 0)
473			continue;
474
475		if (ELF_ST_TYPE(sym->st_info) != STT_NOTYPE &&
476		    ELF_ST_TYPE(sym->st_info) != STT_OBJECT &&
477		    ELF_ST_TYPE(sym->st_info) != STT_FUNC)
478			continue;
479
480		symn = strt + sym->st_name;
481		if (sym != *this && _dl_strcmp(symn, name))
482			continue;
483
484		/* allow this symbol if we are referring to a function
485		 * which has a value, even if section is UNDEF.
486		 * this allows &func to refer to PLT as per the
487		 * ELF spec. st_value is checked above.
488		 * if flags has SYM_PLT set, we must have actual
489		 * symbol, so this symbol is skipped.
490		 */
491		if (sym->st_shndx == SHN_UNDEF) {
492			if ((flags & SYM_PLT) || sym->st_value == 0 ||
493			    ELF_ST_TYPE(sym->st_info) != STT_FUNC)
494				continue;
495		}
496
497		if (ELF_ST_BIND(sym->st_info) == STB_GLOBAL) {
498			*this = sym;
499			return 1;
500		} else if (ELF_ST_BIND(sym->st_info) == STB_WEAK) {
501			if (!*weak_sym) {
502				*weak_sym = sym;
503				*weak_object = object;
504			}
505		}
506	}
507	return 0;
508}
509
510void
511_dl_debug_state(void)
512{
513        /* Debugger stub */
514}
515