summaryrefslogtreecommitdiff
path: root/ldso/libdl/libdl.c
blob: fbb19223aba5ef7c8acaeee18922fffa065dbb99 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
/*
 * libdl.c
 * 
 * Functions required for dlopen et. al.
 */

#include <stdlib.h>
#include <features.h>
#include "dlfcn.h"
#include "linuxelf.h"
#include "ld_syscall.h"
#include "ld_hash.h"
#include "ld_string.h"

extern int _dl_error_number;
extern struct r_debug *_dl_debug_addr;

extern void *(*_dl_malloc_function) (size_t size);

static int do_fixup(struct elf_resolve *tpnt, int flag);
static int do_dlclose(void *, int need_fini);

void *dlopen(const char *, int) __attribute__ ((__weak__, __alias__ ("_dlopen")));
const char *dlerror(void) __attribute__ ((__weak__, __alias__ ("_dlerror")));
void *dlsym(void *, const char *) __attribute__ ((__weak__, __alias__ ("_dlsym")));
int dlclose(void *) __attribute__ ((__weak__, __alias__ ("_dlclose")));
int dladdr(void *, Dl_info *) __attribute__ ((__weak__, __alias__ ("_dladdr")));

/* This is a real hack.  We need access to the dynamic linker, but we
also need to make it possible to link against this library without any
unresolved externals.  We provide these weak symbols to make the link
possible, but at run time the normal symbols are accessed. */
static void __attribute__ ((unused)) foobar(void)
{
	const char msg[]="libdl library not correctly linked\n";
	_dl_write(2, msg, _dl_strlen(msg));
	_dl_exit(1);
}

static int __attribute__ ((unused)) foobar1 = (int) foobar;	/* Use as pointer */
extern void _dl_dprintf(int, const char *, ...) __attribute__ ((__weak__, __alias__ ("foobar")));
extern char *_dl_find_hash(const char *, struct dyn_elf *, struct elf_resolve *, enum caller_type)
	__attribute__ ((__weak__, __alias__ ("foobar")));
extern struct elf_resolve * _dl_load_shared_library(int, struct dyn_elf **, struct elf_resolve *, char *)
	__attribute__ ((__weak__, __alias__ ("foobar")));
extern int _dl_parse_relocation_information(struct elf_resolve *, unsigned long, unsigned long, int)
	__attribute__ ((__weak__, __alias__ ("foobar")));
extern void _dl_parse_lazy_relocation_information(struct elf_resolve *, unsigned long, unsigned long, int)
	__attribute__ ((__weak__, __alias__ ("foobar")));
#ifdef __mips__
extern void _dl_perform_mips_global_got_relocations(struct elf_resolve *tpnt)
	__attribute__ ((__weak__, __alias__ ("foobar")));
#endif
#ifdef USE_CACHE
int _dl_map_cache(void) __attribute__ ((__weak__, __alias__ ("foobar")));
int _dl_unmap_cache(void) __attribute__ ((__weak__, __alias__ ("foobar")));
#endif	

extern struct dyn_elf *_dl_symbol_tables __attribute__ ((__weak__, __alias__ ("foobar1")));
extern struct dyn_elf *_dl_handles __attribute__ ((__weak__, __alias__ ("foobar1")));
extern struct elf_resolve *_dl_loaded_modules __attribute__ ((__weak__, __alias__ ("foobar1")));
extern struct r_debug *_dl_debug_addr __attribute__ ((__weak__, __alias__ ("foobar1")));
extern int _dl_error_number __attribute__ ((__weak__, __alias__ ("foobar1")));
extern void *(*_dl_malloc_function)(size_t) __attribute__ ((__weak__, __alias__ ("foobar1")));

static const char *dl_error_names[] = {
	"",
	"File not found",
	"Unable to open /dev/zero",
	"Not an ELF file",
#if defined (__i386__)
	"Not i386 binary",
#elif defined (__sparc__)
	"Not sparc binary",
#elif defined (__mc68000__)
	"Not m68k binary",
#else
	"Unrecognized binary type",
#endif
	"Not an ELF shared library",
	"Unable to mmap file",
	"No dynamic section",
#ifdef ELF_USES_RELOCA
	"Unable to process REL relocs",
#else
	"Unable to process RELA relocs",
#endif
	"Bad handle",
	"Unable to resolve symbol"
};

static void __attribute__ ((destructor)) dl_cleanup(void)
{
	struct dyn_elf *d;

	for (d = _dl_handles; d; d = d->next_handle)
		if (d->dyn->libtype == loaded_file && d->dyn->dynamic_info[DT_FINI]) {
			(* ((int (*)(void)) (d->dyn->loadaddr + d->dyn->dynamic_info[DT_FINI]))) ();
			d->dyn->dynamic_info[DT_FINI] = 0;
		}
}

void *_dlopen(const char *libname, int flag)
{
	struct elf_resolve *tpnt, *tfrom;
	struct dyn_elf *rpnt = NULL;
	struct dyn_elf *dyn_chain;
	struct dyn_elf *dpnt;
	static int dl_init = 0;
	char *from;
	void (*dl_brk) (void);
	int (*dl_elf_init) (void);

	from = __builtin_return_address(0);

	/* Have the dynamic linker use the regular malloc function now */
	if (!dl_init) {
		dl_init++;
		_dl_malloc_function = malloc;
	}

	/* Cover the trivial case first */
	if (!libname)
		return _dl_symbol_tables;

#ifdef USE_CACHE
	_dl_map_cache();
#endif

	/*
	 * Try and locate the module we were called from - we
	 * need this so that we get the correct RPATH.  Note that
	 * this is the current behavior under Solaris, but the
	 * ABI+ specifies that we should only use the RPATH from
	 * the application.  Thus this may go away at some time
	 * in the future.
	 */
	tfrom = NULL;
	for (dpnt = _dl_symbol_tables; dpnt; dpnt = dpnt->next) {
		tpnt = dpnt->dyn;
		if (tpnt->loadaddr < from
			&& (tfrom == NULL || tfrom->loadaddr < tpnt->loadaddr))
			tfrom = tpnt;
	}

	if (!(tpnt = _dl_load_shared_library(0, &rpnt, tfrom, (char*)libname))) {
#ifdef USE_CACHE
		_dl_unmap_cache();
#endif
		return NULL;
	}

	dyn_chain = rpnt = (struct dyn_elf *) malloc(sizeof(struct dyn_elf));
	_dl_memset(rpnt, 0, sizeof(*rpnt));
	rpnt->dyn = tpnt;
	rpnt->flags = flag;
	if (!tpnt->symbol_scope)
		tpnt->symbol_scope = dyn_chain;

	rpnt->next_handle = _dl_handles;
	_dl_handles = rpnt;

	/*
	 * OK, we have the requested file in memory.  Now check for
	 * any other requested files that may also be required.
	 */
	  {
	    struct elf_resolve *tcurr;
	    struct elf_resolve * tpnt1;
	    Elf32_Dyn * dpnt;
	    char * lpnt;

	    tcurr = tpnt;
	    do{
	      for(dpnt = (Elf32_Dyn *) tcurr->dynamic_addr; dpnt->d_tag; dpnt++)
		{
	  
		  if(dpnt->d_tag == DT_NEEDED)
		    {
		      lpnt = tcurr->loadaddr + tcurr->dynamic_info[DT_STRTAB] + 
			dpnt->d_un.d_val;
		      if(!(tpnt1 = _dl_load_shared_library(0, &rpnt, tcurr, lpnt)))
			goto oops;

		      rpnt->next = (struct dyn_elf *) malloc(sizeof(struct dyn_elf));
		      _dl_memset (rpnt->next, 0, sizeof (*(rpnt->next)));
		      rpnt = rpnt->next;
		      if (!tpnt1->symbol_scope) tpnt1->symbol_scope = dyn_chain;
		      rpnt->dyn = tpnt1;
		    };
		}
	      
	      tcurr = tcurr->next;
	    } while(tcurr);
	  }
	 
	/*
	 * OK, now attach the entire chain at the end
	 */

	rpnt->next = _dl_symbol_tables;

	/*
	 * MIPS is special *sigh*
	 */
#ifdef __mips__
	_dl_perform_mips_global_got_relocations(tpnt);
#endif

	if (do_fixup(tpnt, flag)) {
		_dl_error_number = LD_NO_SYMBOL;
		goto oops;
	}

	dl_brk = (void (*)(void)) _dl_debug_addr->r_brk;
	if (dl_brk != NULL) {
		_dl_debug_addr->r_state = RT_ADD;
		(*dl_brk) ();

		_dl_debug_addr->r_state = RT_CONSISTENT;
		(*dl_brk) ();
	}

	for (rpnt = dyn_chain; rpnt; rpnt = rpnt->next) {
		tpnt = rpnt->dyn;
		/* Apparently crt1 for the application is responsible for handling this.
		 * We only need to run the init/fini for shared libraries
		 */
		if (tpnt->libtype == program_interpreter)
			continue;
		if (tpnt->libtype == elf_executable)
			continue;
		if (tpnt->init_flag & INIT_FUNCS_CALLED)
			continue;
		tpnt->init_flag |= INIT_FUNCS_CALLED;

		if (tpnt->dynamic_info[DT_INIT]) {
			dl_elf_init = (int (*)(void)) (tpnt->loadaddr + tpnt->dynamic_info[DT_INIT]);
			(*dl_elf_init) ();
		}
		if (tpnt->dynamic_info[DT_FINI]) {
			atexit((void (*)(void)) (tpnt->loadaddr + tpnt->dynamic_info[DT_FINI]));
		}

	}

#ifdef USE_CACHE
	_dl_unmap_cache();
#endif
	return (void *) dyn_chain;

  oops:
	/* Something went wrong.  Clean up and return NULL. */
#ifdef USE_CACHE
	_dl_unmap_cache();
#endif
	do_dlclose(dyn_chain, 0);
	return NULL;
}

static int do_fixup(struct elf_resolve *tpnt, int flag)
{
	int goof = 0;

	if (tpnt->next)
		goof += do_fixup(tpnt->next, flag);

	if (tpnt->dynamic_info[DT_REL]) {
#ifdef ELF_USES_RELOCA
		goof++;
#else
		if (tpnt->init_flag & RELOCS_DONE)
			return goof;
		tpnt->init_flag |= RELOCS_DONE;

		goof += _dl_parse_relocation_information(tpnt, 
			tpnt->dynamic_info[DT_REL], tpnt->dynamic_info[DT_RELSZ], 0);
#endif
	}
	if (tpnt->dynamic_info[DT_RELA]) {
#ifdef ELF_USES_RELOCA
		if (tpnt->init_flag & RELOCS_DONE)
			return goof;
		tpnt->init_flag |= RELOCS_DONE;

		goof += _dl_parse_relocation_information(tpnt, 
			tpnt->dynamic_info[DT_RELA], tpnt->dynamic_info[DT_RELASZ], 0);
#else
		goof++;
#endif
	}
	if (tpnt->dynamic_info[DT_JMPREL]) {
		if (tpnt->init_flag & JMP_RELOCS_DONE)
			return goof;
		tpnt->init_flag |= JMP_RELOCS_DONE;

		if (flag == RTLD_LAZY)
			_dl_parse_lazy_relocation_information(tpnt, 
				tpnt->dynamic_info[DT_JMPREL], 
				tpnt->dynamic_info[DT_PLTRELSZ], 0);
		else
			goof += _dl_parse_relocation_information(tpnt, 
				tpnt->dynamic_info[DT_JMPREL], 
				tpnt->dynamic_info[DT_PLTRELSZ], 0);
	};
	return goof;
}

void *_dlsym(void *vhandle, const char *name)
{
	struct elf_resolve *tpnt, *tfrom;
	struct dyn_elf *handle;
	char *from;
	struct dyn_elf *rpnt;
	void *ret;

	handle = (struct dyn_elf *) vhandle;

	/* First of all verify that we have a real handle
	   of some kind.  Return NULL if not a valid handle. */

	if (handle == NULL)
		handle = _dl_symbol_tables;
	else if (handle != RTLD_NEXT && handle != _dl_symbol_tables) {
		for (rpnt = _dl_handles; rpnt; rpnt = rpnt->next_handle)
			if (rpnt == handle)
				break;
		if (!rpnt) {
			_dl_error_number = LD_BAD_HANDLE;
			return NULL;
		}
	} else if (handle == RTLD_NEXT) {
		/*
		 * Try and locate the module we were called from - we
		 * need this so that we know where to start searching
		 * from.  We never pass RTLD_NEXT down into the actual
		 * dynamic loader itself, as it doesn't know
		 * how to properly treat it.
		 */
		from = __builtin_return_address(0);

		tfrom = NULL;
		for (rpnt = _dl_symbol_tables; rpnt; rpnt = rpnt->next) {
			tpnt = rpnt->dyn;
			if (tpnt->loadaddr < from
				&& (tfrom == NULL || tfrom->loadaddr < tpnt->loadaddr)) {
				tfrom = tpnt;
				handle = rpnt->next;
			}
		}
	}

	ret = _dl_find_hash((char*)name, handle, NULL, copyrel);

	/*
	 * Nothing found.
	 */
	if (!ret)
		_dl_error_number = LD_NO_SYMBOL;
	return ret;
}

int _dlclose(void *vhandle)
{
	return do_dlclose(vhandle, 1);
}

static int do_dlclose(void *vhandle, int need_fini)
{
	struct dyn_elf *rpnt, *rpnt1;
	struct dyn_elf *spnt, *spnt1;
	elf_phdr *ppnt;
	struct elf_resolve *tpnt;
	int (*dl_elf_fini) (void);
	void (*dl_brk) (void);
	struct dyn_elf *handle;
	unsigned int end;
	int i = 0;

	handle = (struct dyn_elf *) vhandle;
	rpnt1 = NULL;
	for (rpnt = _dl_handles; rpnt; rpnt = rpnt->next_handle) {
		if (rpnt == handle) {
			break;
		}
		rpnt1 = rpnt;
	}

	if (!rpnt) {
		_dl_error_number = LD_BAD_HANDLE;
		return 1;
	}

	/* OK, this is a valid handle - now close out the file.
	 * We check if we need to call fini () on the handle. */
	spnt = need_fini ? handle : handle->next;
	for (; spnt; spnt = spnt1) {
		spnt1 = spnt->next;

		/* We appended the module list to the end - when we get back here, 
		   quit. The access counts were not adjusted to account for being here. */
		if (spnt == _dl_symbol_tables)
			break;
		if (spnt->dyn->usage_count == 1
			&& spnt->dyn->libtype == loaded_file) {
			tpnt = spnt->dyn;
			/* Apparently crt1 for the application is responsible for handling this.
			 * We only need to run the init/fini for shared libraries
			 */

			if (tpnt->dynamic_info[DT_FINI]) {
				dl_elf_fini = (int (*)(void)) (tpnt->loadaddr + 
					tpnt->dynamic_info[DT_FINI]);
				(*dl_elf_fini) ();
			}
		}
	}
	if (rpnt1)
		rpnt1->next_handle = rpnt->next_handle;
	else
		_dl_handles = rpnt->next_handle;

	/* OK, this is a valid handle - now close out the file */
	for (rpnt = handle; rpnt; rpnt = rpnt1) {
		rpnt1 = rpnt->next;

		/* We appended the module list to the end - when we get back here, 
		   quit. The access counts were not adjusted to account for being here. */
		if (rpnt == _dl_symbol_tables)
			break;

		rpnt->dyn->usage_count--;
		if (rpnt->dyn->usage_count == 0
			&& rpnt->dyn->libtype == loaded_file) {
			tpnt = rpnt->dyn;
			/* Apparently crt1 for the application is responsible for handling this.
			 * We only need to run the init/fini for shared libraries
			 */
#if 0

			/* We have to do this above, before we start closing objects.  
			 * Otherwise when the needed symbols for _fini handling are 
			 * resolved a coredump would occur. Rob Ryan (robr@cmu.edu)*/ 
			if (tpnt->dynamic_info[DT_FINI]) { 
			    dl_elf_fini = (int (*)(void)) (tpnt->loadaddr + tpnt->dynamic_info[DT_FINI]);
				(*dl_elf_fini) ();
			}
#endif
			end = 0;
			for (i = 0, ppnt = rpnt->dyn->ppnt;
				 i < rpnt->dyn->n_phent; ppnt++, i++) {
				if (ppnt->p_type != PT_LOAD)
					continue;
				if (end < ppnt->p_vaddr + ppnt->p_memsz)
					end = ppnt->p_vaddr + ppnt->p_memsz;
			}
			_dl_munmap(rpnt->dyn->loadaddr, end);
			/* Next, remove rpnt->dyn from the loaded_module list */
			if (_dl_loaded_modules == rpnt->dyn) {
				_dl_loaded_modules = rpnt->dyn->next;
				if (_dl_loaded_modules)
					_dl_loaded_modules->prev = 0;
			} else
				for (tpnt = _dl_loaded_modules; tpnt; tpnt = tpnt->next)
					if (tpnt->next == rpnt->dyn) {
						tpnt->next = tpnt->next->next;
						if (tpnt->next)
							tpnt->next->prev = tpnt;
						break;
					}
			free(rpnt->dyn->libname);
			free(rpnt->dyn);
		}
		free(rpnt);
	}


	dl_brk = (void (*)(void)) _dl_debug_addr->r_brk;
	if (dl_brk != NULL) {
		_dl_debug_addr->r_state = RT_DELETE;
		(*dl_brk) ();

		_dl_debug_addr->r_state = RT_CONSISTENT;
		(*dl_brk) ();
	}

	return 0;
}

const char *_dlerror(void)
{
	const char *retval;

	if (!_dl_error_number)
		return NULL;
	retval = dl_error_names[_dl_error_number];
	_dl_error_number = 0;
	return retval;
}

/*
 * Dump information to stderrr about the current loaded modules
 */
static char *type[] = { "Lib", "Exe", "Int", "Mod" };

void _dlinfo(void)
{
	struct elf_resolve *tpnt;
	struct dyn_elf *rpnt, *hpnt;

	_dl_dprintf(2, "List of loaded modules\n");
	/* First start with a complete list of all of the loaded files. */
	for (tpnt = _dl_loaded_modules; tpnt; tpnt = tpnt->next) { 
		_dl_dprintf(2, "\t%x %x %x %s %d %s\n", 
			(unsigned) tpnt->loadaddr, (unsigned) tpnt,
			(unsigned) tpnt->symbol_scope,
			type[tpnt->libtype],
			tpnt->usage_count, tpnt->libname);
	}

	/* Next dump the module list for the application itself */
	_dl_dprintf(2, "\nModules for application (%x):\n",
				 (unsigned) _dl_symbol_tables);
	for (rpnt = _dl_symbol_tables; rpnt; rpnt = rpnt->next)
		_dl_dprintf(2, "\t%x %s\n", (unsigned) rpnt->dyn, rpnt->dyn->libname);

	for (hpnt = _dl_handles; hpnt; hpnt = hpnt->next_handle) {
		_dl_dprintf(2, "Modules for handle %x\n", (unsigned) hpnt);
		for (rpnt = hpnt; rpnt; rpnt = rpnt->next)
			_dl_dprintf(2, "\t%x %s\n", (unsigned) rpnt->dyn, 
				rpnt->dyn->libname);
	}
}

int _dladdr(void *__address, Dl_info * __dlip)
{
	struct elf_resolve *pelf;
	struct elf_resolve *rpnt;

#ifdef USE_CACHE
	_dl_map_cache();
#endif

	/*
	 * Try and locate the module address is in
	 */
	pelf = NULL;

#if 0
	_dl_dprintf(2, "dladdr( 0x%p, 0x%p )\n", __address, __dlip);
#endif

	for (rpnt = _dl_loaded_modules; rpnt; rpnt = rpnt->next) {
		struct elf_resolve *tpnt;

		tpnt = rpnt;
#if 0
		_dl_dprintf(2, "Module \"%s\" at 0x%p\n", 
			tpnt->libname, tpnt->loadaddr);
#endif
		if (tpnt->loadaddr < (char *) __address
			&& (pelf == NULL || pelf->loadaddr < tpnt->loadaddr)) {
		    pelf = tpnt;
		}
	}

	if (!pelf) {
		return 0;
	}

	/*
	 * Try and locate the symbol of address
	 */

	{
		char *strtab;
		Elf32_Sym *symtab;
		int hn, si;
		int sf;
		int sn = 0;
		void *sa = 0;

		symtab = (Elf32_Sym *) (pelf->dynamic_info[DT_SYMTAB] + pelf->loadaddr);
		strtab = (char *) (pelf->dynamic_info[DT_STRTAB] + pelf->loadaddr);

		sf = 0;
		for (hn = 0; hn < pelf->nbucket; hn++) {
			for (si = pelf->elf_buckets[hn]; si; si = pelf->chains[si]) {
				void *symbol_addr;

				symbol_addr = pelf->loadaddr + symtab[si].st_value;
				if (symbol_addr <= __address && (!sf || sa < symbol_addr)) {
					sa = symbol_addr;
					sn = si;
					sf = 1;
				}
#if 0
				_dl_dprintf(2, "Symbol \"%s\" at 0x%p\n", 
					strtab + symtab[si].st_name, symbol_addr);
#endif
			}
		}

		if (sf) {
			__dlip->dli_fname = pelf->libname;
			__dlip->dli_fbase = pelf->loadaddr;
			__dlip->dli_sname = strtab + symtab[sn].st_name;
			__dlip->dli_saddr = sa;
		}
		return 1;
	}
}