resolve.c revision 1.58 
1/*	$OpenBSD: resolve.c,v 1.58 2012/06/14 21:30:50 kettenis 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	object->obj_type = objtype;
111
112	if (_dl_loading_object == NULL) {
113		/*
114		 * no loading object, object is the loading object,
115		 * as it is either executable, or dlopened()
116		 */
117		_dl_loading_object = object;
118		DL_DEB(("head %s\n", object->load_name));
119	}
120
121	if ((object->obj_flags & DF_1_NOOPEN) != 0 &&
122	    _dl_loading_object->obj_type == OBJTYPE_DLO &&
123	    _dl_traceld == NULL) {
124		_dl_free(object);
125		_dl_errno = DL_CANT_LOAD_OBJ;
126		return(NULL);
127	}
128
129	/*
130	 *  Now relocate all pointer to dynamic info, but only
131	 *  the ones which have pointer values.
132	 */
133	if (object->Dyn.info[DT_PLTGOT])
134		object->Dyn.info[DT_PLTGOT] += obase;
135	if (object->Dyn.info[DT_HASH])
136		object->Dyn.info[DT_HASH] += obase;
137	if (object->Dyn.info[DT_STRTAB])
138		object->Dyn.info[DT_STRTAB] += obase;
139	if (object->Dyn.info[DT_SYMTAB])
140		object->Dyn.info[DT_SYMTAB] += obase;
141	if (object->Dyn.info[DT_RELA])
142		object->Dyn.info[DT_RELA] += obase;
143	if (object->Dyn.info[DT_SONAME])
144		object->Dyn.info[DT_SONAME] += object->Dyn.info[DT_STRTAB];
145	if (object->Dyn.info[DT_RPATH])
146		object->Dyn.info[DT_RPATH] += object->Dyn.info[DT_STRTAB];
147	if (object->Dyn.info[DT_REL])
148		object->Dyn.info[DT_REL] += obase;
149	if (object->Dyn.info[DT_INIT])
150		object->Dyn.info[DT_INIT] += obase;
151	if (object->Dyn.info[DT_FINI])
152		object->Dyn.info[DT_FINI] += obase;
153	if (object->Dyn.info[DT_JMPREL])
154		object->Dyn.info[DT_JMPREL] += obase;
155
156	if (object->Dyn.info[DT_HASH] != 0) {
157		Elf_Word *hashtab = (Elf_Word *)object->Dyn.info[DT_HASH];
158
159		object->nbuckets = hashtab[0];
160		object->nchains = hashtab[1];
161		object->buckets = hashtab + 2;
162		object->chains = object->buckets + object->nbuckets;
163	}
164
165	object->phdrp = phdrp;
166	object->phdrc = phdrc;
167	object->load_base = lbase;
168	object->obj_base = obase;
169	object->load_name = _dl_strdup(objname);
170	object->load_object = _dl_loading_object;
171	DL_DEB(("obj %s has %s as head\n", object->load_name,
172	    _dl_loading_object->load_name ));
173	object->refcount = 0;
174	TAILQ_INIT(&object->child_list);
175	object->opencount = 0;	/* # dlopen() & exe */
176	object->grprefcount = 0;
177	/* default dev, inode for dlopen-able objects. */
178	object->dev = 0;
179	object->inode = 0;
180	object->lastlookup = 0;
181	TAILQ_INIT(&object->grpsym_list);
182	TAILQ_INIT(&object->grpref_list);
183
184	return(object);
185}
186
187void
188_dl_tailq_free(struct dep_node *n)
189{
190	struct dep_node *next;
191
192	while (n != NULL) {
193		next = TAILQ_NEXT(n, next_sib);
194		_dl_free(n);
195		n = next;
196	}
197}
198
199elf_object_t *free_objects;
200
201void _dl_cleanup_objects(void);
202void
203_dl_cleanup_objects()
204{
205	elf_object_t *nobj, *head;
206	struct dep_node *n, *next;
207
208	n = TAILQ_FIRST(&_dlopened_child_list);
209	while (n != NULL) {
210		next = TAILQ_NEXT(n, next_sib);
211		if (OBJECT_DLREF_CNT(n->data) == 0) {
212			TAILQ_REMOVE(&_dlopened_child_list, n, next_sib);
213			_dl_free(n);
214		}
215		n = next;
216	}
217
218	head = free_objects;
219	free_objects = NULL;
220	while (head != NULL) {
221		if (head->load_name)
222			_dl_free(head->load_name);
223		if (head->sod.sod_name)
224			_dl_free((char *)head->sod.sod_name);
225		_dl_tailq_free(TAILQ_FIRST(&head->grpsym_list));
226		_dl_tailq_free(TAILQ_FIRST(&head->child_list));
227		_dl_tailq_free(TAILQ_FIRST(&head->grpref_list));
228		nobj = head->next;
229		_dl_free(head);
230		head = nobj;
231	}
232}
233
234void
235_dl_remove_object(elf_object_t *object)
236{
237	object->prev->next = object->next;
238	if (object->next)
239		object->next->prev = object->prev;
240
241	if (_dl_last_object == object)
242		_dl_last_object = object->prev;
243
244	object->next = free_objects;
245	free_objects = object;
246}
247
248
249int _dl_find_symbol_obj(elf_object_t *object, const char *name,
250    unsigned long hash, int flags, const Elf_Sym **ref,
251    const Elf_Sym **weak_sym,
252    elf_object_t **weak_object);
253
254sym_cache *_dl_symcache;
255int _dl_symcachestat_hits;
256int _dl_symcachestat_lookups;
257
258
259Elf_Addr
260_dl_find_symbol_bysym(elf_object_t *req_obj, unsigned int symidx,
261    const Elf_Sym **this, int flags, const Elf_Sym *ref_sym, const elf_object_t **pobj)
262{
263	Elf_Addr ret;
264	const Elf_Sym *sym;
265	const char *symn;
266	const elf_object_t *sobj;
267
268	_dl_symcachestat_lookups ++;
269	if (_dl_symcache != NULL &&
270	    symidx < req_obj->nchains &&
271	    _dl_symcache[symidx].obj != NULL &&
272	    _dl_symcache[symidx].sym != NULL &&
273	    _dl_symcache[symidx].flags == flags) {
274
275		_dl_symcachestat_hits++;
276		sobj = _dl_symcache[symidx].obj;
277		*this = _dl_symcache[symidx].sym;
278		if (pobj)
279			*pobj = sobj;
280		if (_dl_prebind_validate) /* XXX */
281			prebind_validate(req_obj, symidx, flags, ref_sym);
282		return sobj->obj_base;
283	}
284
285	sym = req_obj->dyn.symtab;
286	sym += symidx;
287	symn = req_obj->dyn.strtab + sym->st_name;
288
289	ret = _dl_find_symbol(symn, this, flags, ref_sym, req_obj, &sobj);
290
291	if (pobj)
292		*pobj = sobj;
293
294	if (_dl_symcache != NULL && symidx < req_obj->nchains) {
295#if 0
296		DL_DEB(("cache miss %d %p %p, %p %p %s %s %d %d %s\n",
297		    symidx,
298		    _dl_symcache[symidx].sym, *this,
299		    _dl_symcache[symidx].obj, sobj, sobj->load_name,
300		    sobj->dyn.strtab + (*this)->st_name,
301		    _dl_symcache[symidx].flags, flags, req_obj->load_name));
302#endif
303
304		_dl_symcache[symidx].sym = *this;
305		_dl_symcache[symidx].obj = sobj;
306		_dl_symcache[symidx].flags = flags;
307	}
308
309	return ret;
310}
311
312int _dl_searchnum = 0;
313void
314_dl_newsymsearch(void)
315{
316	_dl_searchnum += 1;
317
318	if (_dl_searchnum < 0) {
319		/*
320		 * If the signed number rolls over, reset all counters so
321		 * we dont get accidental collision.
322		 */
323		elf_object_t *walkobj;
324		for (walkobj = _dl_objects;
325		    walkobj != NULL;
326		    walkobj = walkobj->next) {
327			walkobj->lastlookup = 0;
328		}
329		_dl_searchnum = 1;
330	}
331}
332
333Elf_Addr
334_dl_find_symbol(const char *name, const Elf_Sym **this,
335    int flags, const Elf_Sym *ref_sym, elf_object_t *req_obj,
336    const elf_object_t **pobj)
337{
338	const Elf_Sym *weak_sym = NULL;
339	unsigned long h = 0;
340	const char *p = name;
341	elf_object_t *object = NULL, *weak_object = NULL;
342	int found = 0;
343	struct dep_node *n, *m;
344
345
346	while (*p) {
347		unsigned long g;
348		h = (h << 4) + *p++;
349		if ((g = h & 0xf0000000))
350			h ^= g >> 24;
351		h &= ~g;
352	}
353
354	if (req_obj->dyn.symbolic)
355		if (_dl_find_symbol_obj(req_obj, name, h, flags, this, &weak_sym,
356		    &weak_object)) {
357			object = req_obj;
358			found = 1;
359			goto found;
360		}
361
362	if (flags & SYM_SEARCH_OBJ) {
363		if (_dl_find_symbol_obj(req_obj, name, h, flags, this,
364		    &weak_sym, &weak_object)) {
365			object = req_obj;
366			found = 1;
367		}
368	} else if (flags & SYM_DLSYM) {
369		if (_dl_find_symbol_obj(req_obj, name, h, flags, this,
370		    &weak_sym, &weak_object)) {
371			object = req_obj;
372			found = 1;
373		}
374		if (weak_object != NULL && found == 0) {
375			object=weak_object;
376			*this = weak_sym;
377			found = 1;
378		}
379		/* search dlopened obj and all children */
380
381		if (found == 0) {
382			TAILQ_FOREACH(n, &req_obj->load_object->grpsym_list,
383			    next_sib) {
384				if (_dl_find_symbol_obj(n->data, name, h,
385				    flags, this,
386				    &weak_sym, &weak_object)) {
387					object = n->data;
388					found = 1;
389					break;
390				}
391			}
392		}
393	} else {
394		int skip = 0;
395
396		if ((flags & SYM_SEARCH_SELF) || (flags & SYM_SEARCH_NEXT))
397			skip = 1;
398
399		_dl_newsymsearch();
400
401		/*
402		 * search dlopened objects: global or req_obj == dlopened_obj
403		 * and and it's children
404		 */
405		TAILQ_FOREACH(n, &_dlopened_child_list, next_sib) {
406			if (((n->data->obj_flags & DF_1_GLOBAL) == 0) &&
407			    (n->data != req_obj->load_object))
408				continue;
409
410			n->data->lastlookup_head = _dl_searchnum;
411			TAILQ_FOREACH(m, &n->data->grpsym_list, next_sib) {
412				if (skip == 1) {
413					if (m->data == req_obj) {
414						skip = 0;
415						if (flags & SYM_SEARCH_NEXT)
416							continue;
417					} else
418						continue;
419				}
420				if ((flags & SYM_SEARCH_OTHER) &&
421				    (m->data == req_obj))
422					continue;
423				m->data->lastlookup = _dl_searchnum;
424				if (_dl_find_symbol_obj(m->data, name, h, flags,
425				    this, &weak_sym, &weak_object)) {
426					object = m->data;
427					found = 1;
428					goto found;
429				}
430			}
431		}
432	}
433
434found:
435	if (weak_object != NULL && found == 0) {
436		object=weak_object;
437		*this = weak_sym;
438		found = 1;
439	}
440
441
442	if (found == 0) {
443		if ((ref_sym == NULL ||
444		    (ELF_ST_BIND(ref_sym->st_info) != STB_WEAK)) &&
445		    (flags & SYM_WARNNOTFOUND))
446			_dl_printf("%s:%s: undefined symbol '%s'\n",
447			    _dl_progname, req_obj->load_name, name);
448		return (0);
449	}
450
451	if (ref_sym != NULL && ref_sym->st_size != 0 &&
452	    (ref_sym->st_size != (*this)->st_size)  &&
453	    (ELF_ST_TYPE((*this)->st_info) != STT_FUNC) ) {
454		_dl_printf("%s:%s: %s : WARNING: "
455		    "symbol(%s) size mismatch, relink your program\n",
456		    _dl_progname, req_obj->load_name,
457		    object->load_name, name);
458	}
459
460	if (pobj)
461		*pobj = object;
462
463	return (object->obj_base);
464}
465
466int
467_dl_find_symbol_obj(elf_object_t *object, const char *name, unsigned long hash,
468    int flags, const Elf_Sym **this, const Elf_Sym **weak_sym,
469    elf_object_t **weak_object)
470{
471	const Elf_Sym	*symt = object->dyn.symtab;
472	const char	*strt = object->dyn.strtab;
473	long	si;
474	const char *symn;
475
476	for (si = object->buckets[hash % object->nbuckets];
477	    si != STN_UNDEF; si = object->chains[si]) {
478		const Elf_Sym *sym = symt + si;
479
480		if (sym->st_value == 0)
481			continue;
482
483		if (ELF_ST_TYPE(sym->st_info) != STT_NOTYPE &&
484		    ELF_ST_TYPE(sym->st_info) != STT_OBJECT &&
485		    ELF_ST_TYPE(sym->st_info) != STT_FUNC)
486			continue;
487
488		symn = strt + sym->st_name;
489		if (sym != *this && _dl_strcmp(symn, name))
490			continue;
491
492		/* allow this symbol if we are referring to a function
493		 * which has a value, even if section is UNDEF.
494		 * this allows &func to refer to PLT as per the
495		 * ELF spec. st_value is checked above.
496		 * if flags has SYM_PLT set, we must have actual
497		 * symbol, so this symbol is skipped.
498		 */
499		if (sym->st_shndx == SHN_UNDEF) {
500			if ((flags & SYM_PLT) || sym->st_value == 0 ||
501			    ELF_ST_TYPE(sym->st_info) != STT_FUNC)
502				continue;
503		}
504
505		if (ELF_ST_BIND(sym->st_info) == STB_GLOBAL) {
506			*this = sym;
507			return 1;
508		} else if (ELF_ST_BIND(sym->st_info) == STB_WEAK) {
509			if (!*weak_sym) {
510				*weak_sym = sym;
511				*weak_object = object;
512			}
513		}
514	}
515	return 0;
516}
517
518void
519_dl_debug_state(void)
520{
521        /* Debugger stub */
522}
523