summaryrefslogtreecommitdiff
path: root/elf/dl-runtime.c
blob: afc99f6150a351f143f39069dc1e58d78354ca5d (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
/* On-demand PLT fixup for shared objects.
   Copyright (C) 1995-2002,2003,2004,2005,2006 Free Software Foundation, Inc.
   This file is part of the GNU C Library.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 of the License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with the GNU C Library; if not, write to the Free
   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
   02111-1307 USA.  */

#define IN_DL_RUNTIME 1		/* This can be tested in dl-machine.h.  */

#include <alloca.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/param.h>
#include <ldsodefs.h>
#include <sysdep-cancel.h>
#include "dynamic-link.h"

#if (!defined ELF_MACHINE_NO_RELA && !defined ELF_MACHINE_PLT_REL) \
    || ELF_MACHINE_NO_REL
# define PLTREL  ElfW(Rela)
#else
# define PLTREL  ElfW(Rel)
#endif

#ifndef VERSYMIDX
# define VERSYMIDX(sym)	(DT_NUM + DT_THISPROCNUM + DT_VERSIONTAGIDX (sym))
#endif

/* The fixup functions might have need special attributes.  If none
   are provided define the macro as empty.  */
#ifndef ARCH_FIXUP_ATTRIBUTE
# define ARCH_FIXUP_ATTRIBUTE
#endif


/* This function is called through a special trampoline from the PLT the
   first time each PLT entry is called.  We must perform the relocation
   specified in the PLT of the given shared object, and return the resolved
   function address to the trampoline, which will restart the original call
   to that address.  Future calls will bounce directly from the PLT to the
   function.  */

#ifndef ELF_MACHINE_NO_PLT
DL_FIXUP_VALUE_TYPE
__attribute ((noinline)) ARCH_FIXUP_ATTRIBUTE
_dl_fixup (
# ifdef ELF_MACHINE_RUNTIME_FIXUP_ARGS
	   ELF_MACHINE_RUNTIME_FIXUP_ARGS,
# endif
	   /* GKM FIXME: Fix trampoline to pass bounds so we can do
	      without the `__unbounded' qualifier.  */
	   struct link_map *__unbounded l, ElfW(Word) reloc_offset)
{
  const ElfW(Sym) *const symtab
    = (const void *) D_PTR (l, l_info[DT_SYMTAB]);
  const char *strtab = (const void *) D_PTR (l, l_info[DT_STRTAB]);

  const PLTREL *const reloc
    = (const void *) (D_PTR (l, l_info[DT_JMPREL]) + reloc_offset);
  const ElfW(Sym) *sym = &symtab[ELFW(R_SYM) (reloc->r_info)];
  void *const rel_addr = (void *)(l->l_addr + reloc->r_offset);
  lookup_t result;
  DL_FIXUP_VALUE_TYPE value;

  /* Sanity check that we're really looking at a PLT relocation.  */
  assert (ELFW(R_TYPE)(reloc->r_info) == ELF_MACHINE_JMP_SLOT);

   /* Look up the target symbol.  If the normal lookup rules are not
      used don't look in the global scope.  */
  if (__builtin_expect (ELFW(ST_VISIBILITY) (sym->st_other), 0) == 0)
    {
      const struct r_found_version *version = NULL;

      if (l->l_info[VERSYMIDX (DT_VERSYM)] != NULL)
	{
	  const ElfW(Half) *vernum =
	    (const void *) D_PTR (l, l_info[VERSYMIDX (DT_VERSYM)]);
	  ElfW(Half) ndx = vernum[ELFW(R_SYM) (reloc->r_info)] & 0x7fff;
	  version = &l->l_versions[ndx];
	  if (version->hash == 0)
	    version = NULL;
	}

      if (l->l_type == lt_loaded && !RTLD_SINGLE_THREAD_P)
	__rtld_mrlock_lock (l->l_scope_lock);

      result = _dl_lookup_symbol_x (strtab + sym->st_name, l, &sym,
				    l->l_scope, version, ELF_RTYPE_CLASS_PLT,
				    DL_LOOKUP_ADD_DEPENDENCY, NULL);

      if (l->l_type == lt_loaded && !RTLD_SINGLE_THREAD_P)
	__rtld_mrlock_unlock (l->l_scope_lock);

      /* Currently result contains the base load address (or link map)
	 of the object that defines sym.  Now add in the symbol
	 offset.  */
      value = DL_FIXUP_MAKE_VALUE (result,
				   sym ? (LOOKUP_VALUE_ADDRESS (result)
					  + sym->st_value) : 0);
    }
  else
    {
      /* We already found the symbol.  The module (and therefore its load
	 address) is also known.  */
      value = DL_FIXUP_MAKE_VALUE (l, l->l_addr + sym->st_value);
      result = l;
    }

  /* And now perhaps the relocation addend.  */
  value = elf_machine_plt_value (l, reloc, value);

  /* Finally, fix up the plt itself.  */
  if (__builtin_expect (GLRO(dl_bind_not), 0))
    return value;

  return elf_machine_fixup_plt (l, result, reloc, rel_addr, value);
}
#endif

#if !defined PROF && !defined ELF_MACHINE_NO_PLT && !__BOUNDED_POINTERS__

DL_FIXUP_VALUE_TYPE
__attribute ((noinline)) ARCH_FIXUP_ATTRIBUTE
_dl_profile_fixup (
#ifdef ELF_MACHINE_RUNTIME_FIXUP_ARGS
		   ELF_MACHINE_RUNTIME_FIXUP_ARGS,
#endif
		   struct link_map *l, ElfW(Word) reloc_offset,
		   ElfW(Addr) retaddr, void *regs, long int *framesizep)
{
  void (*mcount_fct) (ElfW(Addr), ElfW(Addr)) = INTUSE(_dl_mcount);

  /* This is the address in the array where we store the result of previous
     relocations.  */
  struct reloc_result *reloc_result
    = &l->l_reloc_result[reloc_offset / sizeof (PLTREL)];
  DL_FIXUP_VALUE_TYPE *resultp = &reloc_result->addr;

  DL_FIXUP_VALUE_TYPE value = *resultp;
  if (DL_FIXUP_VALUE_CODE_ADDR (value) == 0)
    {
      /* This is the first time we have to relocate this object.  */
      const ElfW(Sym) *const symtab
	= (const void *) D_PTR (l, l_info[DT_SYMTAB]);
      const char *strtab = (const char *) D_PTR (l, l_info[DT_STRTAB]);

      const PLTREL *const reloc
	= (const void *) (D_PTR (l, l_info[DT_JMPREL]) + reloc_offset);
      const ElfW(Sym) *refsym = &symtab[ELFW(R_SYM) (reloc->r_info)];
      const ElfW(Sym) *defsym = refsym;
      lookup_t result;

      /* Sanity check that we're really looking at a PLT relocation.  */
      assert (ELFW(R_TYPE)(reloc->r_info) == ELF_MACHINE_JMP_SLOT);

      /* Look up the target symbol.  If the symbol is marked STV_PROTECTED
	 don't look in the global scope.  */
      if (__builtin_expect (ELFW(ST_VISIBILITY) (refsym->st_other), 0) == 0)
	{
	  const struct r_found_version *version = NULL;

	  if (l->l_info[VERSYMIDX (DT_VERSYM)] != NULL)
	    {
	      const ElfW(Half) *vernum =
		(const void *) D_PTR (l, l_info[VERSYMIDX (DT_VERSYM)]);
	      ElfW(Half) ndx = vernum[ELFW(R_SYM) (reloc->r_info)] & 0x7fff;
	      version = &l->l_versions[ndx];
	      if (version->hash == 0)
		version = NULL;
	    }

	  if (l->l_type == lt_loaded && !RTLD_SINGLE_THREAD_P)
	    __rtld_mrlock_lock (l->l_scope_lock);

	  result = _dl_lookup_symbol_x (strtab + refsym->st_name, l, &defsym,
					l->l_scope, version,
					ELF_RTYPE_CLASS_PLT,
					DL_LOOKUP_ADD_DEPENDENCY, NULL);

	  if (l->l_type == lt_loaded && !RTLD_SINGLE_THREAD_P)
	    __rtld_mrlock_unlock (l->l_scope_lock);

	  /* Currently result contains the base load address (or link map)
	     of the object that defines sym.  Now add in the symbol
	     offset.  */
	  value = DL_FIXUP_MAKE_VALUE (result,
				       defsym != NULL
				       ? LOOKUP_VALUE_ADDRESS (result)
					 + defsym->st_value : 0);
	}
      else
	{
	  /* We already found the symbol.  The module (and therefore its load
	     address) is also known.  */
	  value = DL_FIXUP_MAKE_VALUE (l, l->l_addr + refsym->st_value);
	  result = l;
	}
      /* And now perhaps the relocation addend.  */
      value = elf_machine_plt_value (l, reloc, value);

#ifdef SHARED
      /* Auditing checkpoint: we have a new binding.  Provide the
	 auditing libraries the possibility to change the value and
	 tell us whether further auditing is wanted.  */
      if (defsym != NULL && GLRO(dl_naudit) > 0)
	{
	  reloc_result->bound = result;
	  /* Compute index of the symbol entry in the symbol table of
	     the DSO with the definition.  */
	  reloc_result->boundndx = (defsym
				    - (ElfW(Sym) *) D_PTR (result,
							   l_info[DT_SYMTAB]));

	  /* Determine whether any of the two participating DSOs is
	     interested in auditing.  */
	  if ((l->l_audit_any_plt | result->l_audit_any_plt) != 0)
	    {
	      unsigned int altvalue = 0;
	      struct audit_ifaces *afct = GLRO(dl_audit);
	      /* Synthesize a symbol record where the st_value field is
		 the result.  */
	      ElfW(Sym) sym = *defsym;
	      sym.st_value = DL_FIXUP_VALUE_ADDR (value);

	      /* Keep track whether there is any interest in tracing
		 the call in the lower two bits.  */
	      assert (DL_NNS * 2 <= sizeof (reloc_result->flags) * 8);
	      assert ((LA_SYMB_NOPLTENTER | LA_SYMB_NOPLTEXIT) == 3);
	      reloc_result->enterexit = LA_SYMB_NOPLTENTER | LA_SYMB_NOPLTEXIT;

	      const char *strtab2 = (const void *) D_PTR (result,
							  l_info[DT_STRTAB]);

	      for (unsigned int cnt = 0; cnt < GLRO(dl_naudit); ++cnt)
		{
		  /* XXX Check whether both DSOs must request action or
		     only one */
		  if ((l->l_audit[cnt].bindflags & LA_FLG_BINDFROM) != 0
		      && (result->l_audit[cnt].bindflags & LA_FLG_BINDTO) != 0)
		    {
		      unsigned int flags = altvalue;
		      if (afct->symbind != NULL)
			{
			  uintptr_t new_value
			    = afct->symbind (&sym, reloc_result->boundndx,
					     &l->l_audit[cnt].cookie,
					     &result->l_audit[cnt].cookie,
					     &flags,
					     strtab2 + defsym->st_name);
			  if (new_value != (uintptr_t) sym.st_value)
			    {
			      altvalue = LA_SYMB_ALTVALUE;
			      sym.st_value = new_value;
			    }
			}

		      /* Remember the results for every audit library and
			 store a summary in the first two bits.  */
		      reloc_result->enterexit
			&= flags & (LA_SYMB_NOPLTENTER | LA_SYMB_NOPLTEXIT);
		      reloc_result->enterexit
			|= ((flags & (LA_SYMB_NOPLTENTER | LA_SYMB_NOPLTEXIT))
			    << ((cnt + 1) * 2));
		    }
		  else
		    /* If the bind flags say this auditor is not interested,
		       set the bits manually.  */
		    reloc_result->enterexit
		      |= ((LA_SYMB_NOPLTENTER | LA_SYMB_NOPLTEXIT)
			  << ((cnt + 1) * 2));

		  afct = afct->next;
		}

	      reloc_result->flags = altvalue;
	      value = DL_FIXUP_ADDR_VALUE (sym.st_value);
	    }
	  else
	    /* Set all bits since this symbol binding is not interesting.  */
	    reloc_result->enterexit = (1u << DL_NNS) - 1;
	}
#endif

      /* Store the result for later runs.  */
      if (__builtin_expect (! GLRO(dl_bind_not), 1))
	*resultp = value;
    }

  /* By default we do not call the pltexit function.  */
  long int framesize = -1;

#ifdef SHARED
  /* Auditing checkpoint: report the PLT entering and allow the
     auditors to change the value.  */
  if (DL_FIXUP_VALUE_CODE_ADDR (value) != 0 && GLRO(dl_naudit) > 0
      /* Don't do anything if no auditor wants to intercept this call.  */
      && (reloc_result->enterexit & LA_SYMB_NOPLTENTER) == 0)
    {
      ElfW(Sym) *defsym = ((ElfW(Sym) *) D_PTR (reloc_result->bound,
						l_info[DT_SYMTAB])
			   + reloc_result->boundndx);

      /* Set up the sym parameter.  */
      ElfW(Sym) sym = *defsym;
      sym.st_value = DL_FIXUP_VALUE_ADDR (value);

      /* Get the symbol name.  */
      const char *strtab = (const void *) D_PTR (reloc_result->bound,
						 l_info[DT_STRTAB]);
      const char *symname = strtab + sym.st_name;

      /* Keep track of overwritten addresses.  */
      unsigned int altvalue = reloc_result->flags;

      struct audit_ifaces *afct = GLRO(dl_audit);
      for (unsigned int cnt = 0; cnt < GLRO(dl_naudit); ++cnt)
	{
 	  if (afct->ARCH_LA_PLTENTER != NULL
	      && (reloc_result->enterexit
		  & (LA_SYMB_NOPLTENTER << (2 * (cnt + 1)))) == 0)
	    {
	      unsigned int flags = altvalue;
	      long int new_framesize = -1;
	      uintptr_t new_value
		= afct->ARCH_LA_PLTENTER (&sym, reloc_result->boundndx,
					  &l->l_audit[cnt].cookie,
					  &reloc_result->bound->l_audit[cnt].cookie,
					  regs, &flags, symname,
					  &new_framesize);
	      if (new_value != (uintptr_t) sym.st_value)
		{
		  altvalue = LA_SYMB_ALTVALUE;
		  sym.st_value = new_value;
		}

	      /* Remember the results for every audit library and
		 store a summary in the first two bits.  */
	      reloc_result->enterexit
		|= ((flags & (LA_SYMB_NOPLTENTER | LA_SYMB_NOPLTEXIT))
		    << (2 * (cnt + 1)));

	      if ((reloc_result->enterexit & (LA_SYMB_NOPLTEXIT
					      << (2 * (cnt + 1))))
		  == 0 && new_framesize != -1 && framesize != -2)
		{
		  /* If this is the first call providing information,
		     use it.  */
		  if (framesize == -1)
		    framesize = new_framesize;
		  /* If two pltenter calls provide conflicting information,
		     use the larger value.  */
		  else if (new_framesize != framesize)
		    framesize = MAX (new_framesize, framesize);
		}
	    }

	  afct = afct->next;
	}

      value = DL_FIXUP_ADDR_VALUE (sym.st_value);
    }
#endif

  /* Store the frame size information.  */
  *framesizep = framesize;

  (*mcount_fct) (retaddr, DL_FIXUP_VALUE_CODE_ADDR (value));

  return value;
}

#endif /* PROF && ELF_MACHINE_NO_PLT */


#include <stdio.h>
void
ARCH_FIXUP_ATTRIBUTE
_dl_call_pltexit (struct link_map *l, ElfW(Word) reloc_offset,
		  const void *inregs, void *outregs)
{
#ifdef SHARED
  /* This is the address in the array where we store the result of previous
     relocations.  */
  // XXX Maybe the bound information must be stored on the stack since
  // XXX with bind_not a new value could have been stored in the meantime.
  struct reloc_result *reloc_result
    = &l->l_reloc_result[reloc_offset / sizeof (PLTREL)];
  ElfW(Sym) *defsym = ((ElfW(Sym) *) D_PTR (reloc_result->bound,
					    l_info[DT_SYMTAB])
		       + reloc_result->boundndx);

  /* Set up the sym parameter.  */
  ElfW(Sym) sym = *defsym;

  /* Get the symbol name.  */
  const char *strtab = (const void *) D_PTR (reloc_result->bound,
					     l_info[DT_STRTAB]);
  const char *symname = strtab + sym.st_name;

  struct audit_ifaces *afct = GLRO(dl_audit);
  for (unsigned int cnt = 0; cnt < GLRO(dl_naudit); ++cnt)
    {
      if (afct->ARCH_LA_PLTEXIT != NULL
	  && (reloc_result->enterexit
	      & (LA_SYMB_NOPLTEXIT >> (2 * cnt))) == 0)
	{
	  afct->ARCH_LA_PLTEXIT (&sym, reloc_result->boundndx,
				 &l->l_audit[cnt].cookie,
				 &reloc_result->bound->l_audit[cnt].cookie,
				 inregs, outregs, symname);
	}

      afct = afct->next;
    }
#endif
}