1 /* $NetBSD: headers.c,v 1.59 2014/08/26 21:20:05 joerg Exp $ */
2
3 /*
4 * Copyright 1996 John D. Polstra.
5 * Copyright 1996 Matt Thomas <matt@3am-software.com>
6 * Copyright 2002 Charles M. Hannum <root@ihack.net>
7 * All rights reserved.
8 *
9 * Redistribution and use in source and binary forms, with or without
10 * modification, are permitted provided that the following conditions
11 * are met:
12 * 1. Redistributions of source code must retain the above copyright
13 * notice, this list of conditions and the following disclaimer.
14 * 2. Redistributions in binary form must reproduce the above copyright
15 * notice, this list of conditions and the following disclaimer in the
16 * documentation and/or other materials provided with the distribution.
17 * 3. All advertising materials mentioning features or use of this software
18 * must display the following acknowledgement:
19 * This product includes software developed by John Polstra.
20 * 4. The name of the author may not be used to endorse or promote products
21 * derived from this software without specific prior written permission.
22 *
23 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
24 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
25 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
26 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
27 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
28 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
29 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
30 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
31 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
32 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
33 */
34
35 /*
36 * Dynamic linker for ELF.
37 *
38 * John Polstra <jdp@polstra.com>.
39 */
40
41 #include <sys/cdefs.h>
42 #ifndef lint
43 __RCSID("$NetBSD: headers.c,v 1.59 2014/08/26 21:20:05 joerg Exp $");
44 #endif /* not lint */
45
46 #include <err.h>
47 #include <errno.h>
48 #include <fcntl.h>
49 #include <stdarg.h>
50 #include <stdio.h>
51 #include <stdlib.h>
52 #include <string.h>
53 #include <unistd.h>
54 #include <sys/types.h>
55 #include <sys/mman.h>
56 #include <sys/bitops.h>
57 #include <dirent.h>
58
59 #include "debug.h"
60 #include "rtld.h"
61
62 /*
63 * Process a shared object's DYNAMIC section, and save the important
64 * information in its Obj_Entry structure.
65 */
66 void
_rtld_digest_dynamic(const char * execname,Obj_Entry * obj)67 _rtld_digest_dynamic(const char *execname, Obj_Entry *obj)
68 {
69 Elf_Dyn *dynp;
70 Needed_Entry **needed_tail = &obj->needed;
71 const Elf_Dyn *dyn_soname = NULL;
72 const Elf_Dyn *dyn_rpath = NULL;
73 bool use_pltrel = false;
74 bool use_pltrela = false;
75 Elf_Addr relsz = 0, relasz = 0;
76 Elf_Addr pltrel = 0, pltrelsz = 0;
77 #ifdef RTLD_LOADER
78 Elf_Addr init = 0, fini = 0;
79 #endif
80
81 dbg(("headers: digesting PT_DYNAMIC at %p", obj->dynamic));
82 for (dynp = obj->dynamic; dynp->d_tag != DT_NULL; ++dynp) {
83 dbg((" d_tag %ld at %p", (long)dynp->d_tag, dynp));
84 switch (dynp->d_tag) {
85
86 case DT_REL:
87 obj->rel = (const Elf_Rel *)
88 (obj->relocbase + dynp->d_un.d_ptr);
89 break;
90
91 case DT_RELSZ:
92 relsz = dynp->d_un.d_val;
93 break;
94
95 case DT_RELENT:
96 assert(dynp->d_un.d_val == sizeof(Elf_Rel));
97 break;
98
99 case DT_JMPREL:
100 pltrel = dynp->d_un.d_ptr;
101 break;
102
103 case DT_PLTRELSZ:
104 pltrelsz = dynp->d_un.d_val;
105 break;
106
107 case DT_RELA:
108 obj->rela = (const Elf_Rela *)
109 (obj->relocbase + dynp->d_un.d_ptr);
110 break;
111
112 case DT_RELASZ:
113 relasz = dynp->d_un.d_val;
114 break;
115
116 case DT_RELAENT:
117 assert(dynp->d_un.d_val == sizeof(Elf_Rela));
118 break;
119
120 case DT_PLTREL:
121 use_pltrel = dynp->d_un.d_val == DT_REL;
122 use_pltrela = dynp->d_un.d_val == DT_RELA;
123 assert(use_pltrel || use_pltrela);
124 break;
125
126 case DT_SYMTAB:
127 obj->symtab = (const Elf_Sym *)
128 (obj->relocbase + dynp->d_un.d_ptr);
129 break;
130
131 case DT_SYMENT:
132 assert(dynp->d_un.d_val == sizeof(Elf_Sym));
133 break;
134
135 case DT_STRTAB:
136 obj->strtab = (const char *)
137 (obj->relocbase + dynp->d_un.d_ptr);
138 break;
139
140 case DT_STRSZ:
141 obj->strsize = dynp->d_un.d_val;
142 break;
143
144 case DT_VERNEED:
145 obj->verneed = (const Elf_Verneed *)
146 (obj->relocbase + dynp->d_un.d_ptr);
147 break;
148
149 case DT_VERNEEDNUM:
150 obj->verneednum = dynp->d_un.d_val;
151 break;
152
153 case DT_VERDEF:
154 obj->verdef = (const Elf_Verdef *)
155 (obj->relocbase + dynp->d_un.d_ptr);
156 break;
157
158 case DT_VERDEFNUM:
159 obj->verdefnum = dynp->d_un.d_val;
160 break;
161
162 case DT_VERSYM:
163 obj->versyms = (const Elf_Versym *)
164 (obj->relocbase + dynp->d_un.d_ptr);
165 break;
166
167 case DT_HASH:
168 {
169 const Elf_Symindx *hashtab = (const Elf_Symindx *)
170 (obj->relocbase + dynp->d_un.d_ptr);
171
172 if (hashtab[0] > UINT32_MAX)
173 obj->nbuckets = UINT32_MAX;
174 else
175 obj->nbuckets = hashtab[0];
176 obj->nchains = hashtab[1];
177 obj->buckets = hashtab + 2;
178 obj->chains = obj->buckets + obj->nbuckets;
179 /*
180 * Should really be in _rtld_relocate_objects,
181 * but _rtld_symlook_obj might be used before.
182 */
183 if (obj->nbuckets) {
184 fast_divide32_prepare(obj->nbuckets,
185 &obj->nbuckets_m,
186 &obj->nbuckets_s1,
187 &obj->nbuckets_s2);
188 }
189 }
190 break;
191
192 case DT_NEEDED:
193 {
194 Needed_Entry *nep = NEW(Needed_Entry);
195
196 nep->name = dynp->d_un.d_val;
197 nep->obj = NULL;
198 nep->next = NULL;
199
200 *needed_tail = nep;
201 needed_tail = &nep->next;
202 }
203 break;
204
205 case DT_PLTGOT:
206 obj->pltgot = (Elf_Addr *)
207 (obj->relocbase + dynp->d_un.d_ptr);
208 break;
209
210 case DT_TEXTREL:
211 obj->textrel = true;
212 break;
213
214 case DT_SYMBOLIC:
215 obj->symbolic = true;
216 break;
217
218 case DT_RPATH:
219 /*
220 * We have to wait until later to process this, because
221 * we might not have gotten the address of the string
222 * table yet.
223 */
224 dyn_rpath = dynp;
225 break;
226
227 case DT_SONAME:
228 dyn_soname = dynp;
229 break;
230
231 case DT_INIT:
232 #ifdef RTLD_LOADER
233 init = dynp->d_un.d_ptr;
234 #endif
235 break;
236
237 #ifdef HAVE_INITFINI_ARRAY
238 case DT_INIT_ARRAY:
239 obj->init_array =
240 (Elf_Addr *)(obj->relocbase + dynp->d_un.d_ptr);
241 dbg(("headers: DT_INIT_ARRAY at %p",
242 obj->init_array));
243 break;
244
245 case DT_INIT_ARRAYSZ:
246 obj->init_arraysz = dynp->d_un.d_val / sizeof(fptr_t);
247 dbg(("headers: DT_INIT_ARRAYZ %zu",
248 obj->init_arraysz));
249 break;
250 #endif
251
252 case DT_FINI:
253 #ifdef RTLD_LOADER
254 fini = dynp->d_un.d_ptr;
255 #endif
256 break;
257
258 #ifdef HAVE_INITFINI_ARRAY
259 case DT_FINI_ARRAY:
260 obj->fini_array =
261 (Elf_Addr *)(obj->relocbase + dynp->d_un.d_ptr);
262 dbg(("headers: DT_FINI_ARRAY at %p",
263 obj->fini_array));
264 break;
265
266 case DT_FINI_ARRAYSZ:
267 obj->fini_arraysz = dynp->d_un.d_val / sizeof(fptr_t);
268 dbg(("headers: DT_FINI_ARRAYZ %zu",
269 obj->fini_arraysz));
270 break;
271 #endif
272
273 /*
274 * Don't process DT_DEBUG on MIPS as the dynamic section
275 * is mapped read-only. DT_MIPS_RLD_MAP is used instead.
276 * XXX: n32/n64 may use DT_DEBUG, not sure yet.
277 */
278 #ifndef __mips__
279 case DT_DEBUG:
280 #ifdef RTLD_LOADER
281 dynp->d_un.d_ptr = (Elf_Addr)&_rtld_debug;
282 #endif
283 break;
284 #endif
285
286 #ifdef __mips__
287 case DT_MIPS_LOCAL_GOTNO:
288 obj->local_gotno = dynp->d_un.d_val;
289 break;
290
291 case DT_MIPS_SYMTABNO:
292 obj->symtabno = dynp->d_un.d_val;
293 break;
294
295 case DT_MIPS_GOTSYM:
296 obj->gotsym = dynp->d_un.d_val;
297 break;
298
299 case DT_MIPS_RLD_MAP:
300 #ifdef RTLD_LOADER
301 *((Elf_Addr *)(dynp->d_un.d_ptr)) = (Elf_Addr)
302 &_rtld_debug;
303 #endif
304 break;
305 #endif
306 #ifdef __powerpc__
307 #ifdef _LP64
308 case DT_PPC64_GLINK:
309 obj->glink = (Elf_Addr)(uintptr_t)obj->relocbase + dynp->d_un.d_ptr;
310 break;
311 #else
312 case DT_PPC_GOT:
313 obj->gotptr = (Elf_Addr *)(obj->relocbase + dynp->d_un.d_ptr);
314 break;
315 #endif
316 #endif
317 case DT_FLAGS_1:
318 obj->z_now =
319 ((dynp->d_un.d_val & DF_1_BIND_NOW) != 0);
320 obj->z_nodelete =
321 ((dynp->d_un.d_val & DF_1_NODELETE) != 0);
322 obj->z_initfirst =
323 ((dynp->d_un.d_val & DF_1_INITFIRST) != 0);
324 obj->z_noopen =
325 ((dynp->d_un.d_val & DF_1_NOOPEN) != 0);
326 break;
327 }
328 }
329
330 obj->rellim = (const Elf_Rel *)((const uint8_t *)obj->rel + relsz);
331 obj->relalim = (const Elf_Rela *)((const uint8_t *)obj->rela + relasz);
332 if (use_pltrel) {
333 obj->pltrel = (const Elf_Rel *)(obj->relocbase + pltrel);
334 obj->pltrellim = (const Elf_Rel *)(obj->relocbase + pltrel + pltrelsz);
335 obj->pltrelalim = 0;
336 /* On PPC and SPARC, at least, REL(A)SZ may include JMPREL.
337 Trim rel(a)lim to save time later. */
338 if (obj->rellim && obj->pltrel &&
339 obj->rellim > obj->pltrel &&
340 obj->rellim <= obj->pltrellim)
341 obj->rellim = obj->pltrel;
342 } else if (use_pltrela) {
343 obj->pltrela = (const Elf_Rela *)(obj->relocbase + pltrel);
344 obj->pltrellim = 0;
345 obj->pltrelalim = (const Elf_Rela *)(obj->relocbase + pltrel + pltrelsz);
346 /* On PPC and SPARC, at least, REL(A)SZ may include JMPREL.
347 Trim rel(a)lim to save time later. */
348 if (obj->relalim && obj->pltrela &&
349 obj->relalim > obj->pltrela &&
350 obj->relalim <= obj->pltrelalim)
351 obj->relalim = obj->pltrela;
352 }
353
354 #ifdef RTLD_LOADER
355 if (init != 0)
356 obj->init = (Elf_Addr) obj->relocbase + init;
357 if (fini != 0)
358 obj->fini = (Elf_Addr) obj->relocbase + fini;
359 #endif
360
361 if (dyn_rpath != NULL) {
362 _rtld_add_paths(execname, &obj->rpaths, obj->strtab +
363 dyn_rpath->d_un.d_val);
364 }
365 if (dyn_soname != NULL) {
366 _rtld_object_add_name(obj, obj->strtab +
367 dyn_soname->d_un.d_val);
368 }
369 }
370
371 /*
372 * Process a shared object's program header. This is used only for the
373 * main program, when the kernel has already loaded the main program
374 * into memory before calling the dynamic linker. It creates and
375 * returns an Obj_Entry structure.
376 */
377 Obj_Entry *
_rtld_digest_phdr(const Elf_Phdr * phdr,int phnum,caddr_t entry)378 _rtld_digest_phdr(const Elf_Phdr *phdr, int phnum, caddr_t entry)
379 {
380 Obj_Entry *obj;
381 const Elf_Phdr *phlimit = phdr + phnum;
382 const Elf_Phdr *ph;
383 int nsegs = 0;
384 Elf_Addr vaddr;
385
386 obj = _rtld_obj_new();
387
388 for (ph = phdr; ph < phlimit; ++ph) {
389 if (ph->p_type != PT_PHDR)
390 continue;
391
392 obj->phdr = (void *)(uintptr_t)ph->p_vaddr;
393 obj->phsize = ph->p_memsz;
394 obj->relocbase = (caddr_t)((uintptr_t)phdr - (uintptr_t)ph->p_vaddr);
395 dbg(("headers: phdr %p (%p) phsize %zu relocbase %p",
396 obj->phdr, phdr, obj->phsize, obj->relocbase));
397 break;
398 }
399
400 for (ph = phdr; ph < phlimit; ++ph) {
401 vaddr = (Elf_Addr)(uintptr_t)(obj->relocbase + ph->p_vaddr);
402 switch (ph->p_type) {
403
404 case PT_INTERP:
405 obj->interp = (const char *)(uintptr_t)vaddr;
406 dbg(("headers: %s %p phsize %" PRImemsz,
407 "PT_INTERP", (void *)(uintptr_t)vaddr,
408 ph->p_memsz));
409 break;
410
411 case PT_LOAD:
412 assert(nsegs < 2);
413 if (nsegs == 0) { /* First load segment */
414 obj->vaddrbase = round_down(vaddr);
415 obj->mapbase = (caddr_t)(uintptr_t)obj->vaddrbase;
416 obj->textsize = round_up(vaddr + ph->p_memsz) -
417 obj->vaddrbase;
418 } else { /* Last load segment */
419 obj->mapsize = round_up(vaddr + ph->p_memsz) -
420 obj->vaddrbase;
421 }
422 ++nsegs;
423 dbg(("headers: %s %p phsize %" PRImemsz,
424 "PT_LOAD", (void *)(uintptr_t)vaddr,
425 ph->p_memsz));
426 break;
427
428 case PT_DYNAMIC:
429 obj->dynamic = (Elf_Dyn *)(uintptr_t)vaddr;
430 dbg(("headers: %s %p phsize %" PRImemsz,
431 "PT_DYNAMIC", (void *)(uintptr_t)vaddr,
432 ph->p_memsz));
433 break;
434
435 #if defined(__HAVE_TLS_VARIANT_I) || defined(__HAVE_TLS_VARIANT_II)
436 case PT_TLS:
437 obj->tlsindex = 1;
438 obj->tlssize = ph->p_memsz;
439 obj->tlsalign = ph->p_align;
440 obj->tlsinitsize = ph->p_filesz;
441 obj->tlsinit = (void *)(uintptr_t)ph->p_vaddr;
442 dbg(("headers: %s %p phsize %" PRImemsz,
443 "PT_TLS", (void *)(uintptr_t)vaddr,
444 ph->p_memsz));
445 break;
446 #endif
447 #ifdef __ARM_EABI__
448 case PT_ARM_EXIDX:
449 obj->exidx_start = (void *)(uintptr_t)vaddr;
450 obj->exidx_sz = ph->p_memsz;
451 dbg(("headers: %s %p phsize %" PRImemsz,
452 "PT_ARM_EXIDX", (void *)(uintptr_t)vaddr,
453 ph->p_memsz));
454 break;
455 #endif
456 }
457 }
458 assert(nsegs == 2);
459
460 obj->entry = entry;
461 return obj;
462 }
463