1 /*-
2 * Copyright 1996, 1997, 1998, 1999 John D. Polstra.
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in the
12 * documentation and/or other materials provided with the distribution.
13 *
14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
15 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
16 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
17 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
18 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
19 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
20 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
21 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
22 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
23 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
24 *
25 * $FreeBSD$
26 */
27
28 /*
29 * Dynamic linker for ELF.
30 *
31 * John Polstra <jdp@polstra.com>.
32 */
33
34 #include <sys/param.h>
35 #include <sys/mman.h>
36 #include <sys/tls.h>
37
38 #include <machine/sysarch.h>
39 #include <machine/tls.h>
40
41 #include <dlfcn.h>
42 #include <err.h>
43 #include <errno.h>
44 #include <fcntl.h>
45 #include <stdarg.h>
46 #include <stdio.h>
47 #include <stdlib.h>
48 #include <string.h>
49 #include <unistd.h>
50
51 #include "debug.h"
52 #include "rtld.h"
53
54 /*
55 * Process the special R_X86_64_COPY relocations in the main program. These
56 * copy data from a shared object into a region in the main program's BSS
57 * segment.
58 *
59 * Returns 0 on success, -1 on failure.
60 */
61 int
do_copy_relocations(Obj_Entry * dstobj)62 do_copy_relocations(Obj_Entry *dstobj)
63 {
64 const Elf_Rela *relalim;
65 const Elf_Rela *rela;
66 int error = 0;
67
68 assert(dstobj->mainprog); /* COPY relocations are invalid elsewhere */
69
70 if (dstobj->relro_protected)
71 mprotect(dstobj->relro_page, dstobj->relro_size, PROT_READ | PROT_WRITE);
72
73 relalim = (const Elf_Rela *) ((caddr_t) dstobj->rela + dstobj->relasize);
74 for (rela = dstobj->rela; rela < relalim; rela++) {
75 if (ELF_R_TYPE(rela->r_info) == R_X86_64_COPY) {
76 void *dstaddr;
77 const Elf_Sym *dstsym;
78 const char *name;
79 size_t size;
80 const void *srcaddr;
81 const Elf_Sym *srcsym;
82 const Obj_Entry *srcobj, *defobj;
83 SymLook req;
84 int res;
85
86 dstaddr = (void *) (dstobj->relocbase + rela->r_offset);
87 dstsym = dstobj->symtab + ELF_R_SYM(rela->r_info);
88 name = dstobj->strtab + dstsym->st_name;
89 size = dstsym->st_size;
90 symlook_init(&req, name);
91 req.ventry = fetch_ventry(dstobj, ELF_R_SYM(rela->r_info));
92 req.flags = SYMLOOK_EARLY;
93
94 for (srcobj = dstobj->next; srcobj != NULL; srcobj = srcobj->next) {
95 res = symlook_obj(&req, srcobj);
96 if (res == 0) {
97 srcsym = req.sym_out;
98 defobj = req.defobj_out;
99 break;
100 }
101 }
102
103 if (srcobj == NULL) {
104 _rtld_error("Undefined symbol \"%s\" referenced from COPY"
105 " relocation in %s", name, dstobj->path);
106 error = -1;
107 break;
108 }
109
110 srcaddr = (const void *) (defobj->relocbase + srcsym->st_value);
111 memcpy(dstaddr, srcaddr, size);
112 }
113 }
114
115 if (dstobj->relro_protected)
116 mprotect(dstobj->relro_page, dstobj->relro_size, PROT_READ);
117
118 return error;
119 }
120
121 /* Initialize the special GOT entries. */
122 void
init_pltgot(Obj_Entry * obj)123 init_pltgot(Obj_Entry *obj)
124 {
125 if (obj->pltgot != NULL) {
126 obj->pltgot[1] = (Elf_Addr) obj;
127 obj->pltgot[2] = (Elf_Addr) &_rtld_bind_start;
128 }
129 }
130
131 /* Process the non-PLT relocations. */
132 int
reloc_non_plt(Obj_Entry * obj,Obj_Entry * obj_rtld,int flags,RtldLockState * lockstate)133 reloc_non_plt(Obj_Entry *obj, Obj_Entry *obj_rtld, int flags,
134 RtldLockState *lockstate)
135 {
136 const Elf_Rela *relalim;
137 const Elf_Rela *rela;
138 SymCache *cache;
139 const Elf_Sym *def;
140 const Obj_Entry *defobj;
141 Elf_Addr *where, symval;
142 Elf32_Addr *where32;
143 int r;
144
145 r = -1;
146 /*
147 * The dynamic loader may be called from a thread, we have
148 * limited amounts of stack available so we cannot use alloca().
149 */
150 if (obj != obj_rtld) {
151 cache = calloc(obj->dynsymcount, sizeof(SymCache));
152 /* No need to check for NULL here */
153 } else
154 cache = NULL;
155
156 relalim = (const Elf_Rela *)((caddr_t)obj->rela + obj->relasize);
157 for (rela = obj->rela; rela < relalim; rela++) {
158 /*
159 * First, resolve symbol for relocations which
160 * reference symbols.
161 */
162 switch (ELF_R_TYPE(rela->r_info)) {
163 case R_X86_64_64:
164 case R_X86_64_PC32:
165 case R_X86_64_GLOB_DAT:
166 case R_X86_64_TPOFF64:
167 case R_X86_64_TPOFF32:
168 case R_X86_64_DTPMOD64:
169 case R_X86_64_DTPOFF64:
170 case R_X86_64_DTPOFF32:
171 def = find_symdef(ELF_R_SYM(rela->r_info), obj,
172 &defobj, flags, cache, lockstate);
173 if (def == NULL)
174 goto done;
175 /*
176 * If symbol is IFUNC, only perform relocation
177 * when caller allowed it by passing
178 * SYMLOOK_IFUNC flag. Skip the relocations
179 * otherwise.
180 *
181 * Also error out in case IFUNC relocations
182 * are specified for TLS, which cannot be
183 * usefully interpreted.
184 */
185 if (ELF_ST_TYPE(def->st_info) == STT_GNU_IFUNC) {
186 switch (ELF_R_TYPE(rela->r_info)) {
187 case R_X86_64_64:
188 case R_X86_64_PC32:
189 case R_X86_64_GLOB_DAT:
190 if ((flags & SYMLOOK_IFUNC) == 0) {
191 obj->non_plt_gnu_ifunc = true;
192 continue;
193 }
194 symval = (Elf_Addr)rtld_resolve_ifunc(
195 defobj, def);
196 break;
197 case R_X86_64_TPOFF64:
198 case R_X86_64_TPOFF32:
199 case R_X86_64_DTPMOD64:
200 case R_X86_64_DTPOFF64:
201 case R_X86_64_DTPOFF32:
202 _rtld_error("%s: IFUNC for TLS reloc",
203 obj->path);
204 goto done;
205 }
206 } else {
207 if ((flags & SYMLOOK_IFUNC) != 0)
208 continue;
209 symval = (Elf_Addr)defobj->relocbase +
210 def->st_value;
211 }
212 break;
213 default:
214 if ((flags & SYMLOOK_IFUNC) != 0)
215 continue;
216 break;
217 }
218 where = (Elf_Addr *)(obj->relocbase + rela->r_offset);
219 where32 = (Elf32_Addr *)where;
220
221 switch (ELF_R_TYPE(rela->r_info)) {
222 case R_X86_64_NONE:
223 break;
224 case R_X86_64_64:
225 *where = symval + rela->r_addend;
226 break;
227 case R_X86_64_PC32:
228 /*
229 * I don't think the dynamic linker should
230 * ever see this type of relocation. But the
231 * binutils-2.6 tools sometimes generate it.
232 */
233 *where32 = (Elf32_Addr)(unsigned long)(symval +
234 rela->r_addend - (Elf_Addr)where);
235 break;
236 /* missing: R_X86_64_GOT32 R_X86_64_PLT32 */
237 case R_X86_64_COPY:
238 /*
239 * These are deferred until all other relocations have
240 * been done. All we do here is make sure that the COPY
241 * relocation is not in a shared library. They are allowed
242 * only in executable files.
243 */
244 if (!obj->mainprog) {
245 _rtld_error("%s: Unexpected R_X86_64_COPY "
246 "relocation in shared library", obj->path);
247 goto done;
248 }
249 break;
250 case R_X86_64_GLOB_DAT:
251 *where = symval;
252 break;
253 case R_X86_64_TPOFF64:
254 /*
255 * We lazily allocate offsets for static TLS
256 * as we see the first relocation that
257 * references the TLS block. This allows us to
258 * support (small amounts of) static TLS in
259 * dynamically loaded modules. If we run out
260 * of space, we generate an error.
261 */
262 if (!defobj->tls_static) {
263 if (!allocate_tls_offset((Obj_Entry*) defobj)) {
264 _rtld_error("%s: No space available "
265 "for static Thread Local Storage",
266 obj->path);
267 goto done;
268 }
269 }
270 *where = (Elf_Addr)(def->st_value - defobj->tlsoffset +
271 rela->r_addend);
272 break;
273 case R_X86_64_TPOFF32:
274 /*
275 * We lazily allocate offsets for static TLS
276 * as we see the first relocation that
277 * references the TLS block. This allows us to
278 * support (small amounts of) static TLS in
279 * dynamically loaded modules. If we run out
280 * of space, we generate an error.
281 */
282 if (!defobj->tls_static) {
283 if (!allocate_tls_offset((Obj_Entry*) defobj)) {
284 _rtld_error("%s: No space available "
285 "for static Thread Local Storage",
286 obj->path);
287 goto done;
288 }
289 }
290 *where32 = (Elf32_Addr)(def->st_value -
291 defobj->tlsoffset + rela->r_addend);
292 break;
293 case R_X86_64_DTPMOD64:
294 *where += (Elf_Addr)defobj->tlsindex;
295 break;
296 case R_X86_64_DTPOFF64:
297 *where += (Elf_Addr)(def->st_value + rela->r_addend);
298 break;
299 case R_X86_64_DTPOFF32:
300 *where32 += (Elf32_Addr)(def->st_value +
301 rela->r_addend);
302 break;
303 case R_X86_64_RELATIVE:
304 *where = (Elf_Addr)(obj->relocbase + rela->r_addend);
305 break;
306 case R_X86_64_IRELATIVE:
307 obj->irelative_nonplt = true;
308 break;
309 /*
310 * missing:
311 * R_X86_64_GOTPCREL, R_X86_64_32, R_X86_64_32S, R_X86_64_16,
312 * R_X86_64_PC16, R_X86_64_8, R_X86_64_PC8
313 */
314 default:
315 _rtld_error("%s: Unsupported relocation type %u"
316 " in non-PLT relocations\n", obj->path,
317 (unsigned int)ELF_R_TYPE(rela->r_info));
318 goto done;
319 }
320 }
321 r = 0;
322 done:
323 free(cache);
324 return (r);
325 }
326
327 /* Process the PLT relocations. */
328 int
reloc_plt(Obj_Entry * obj)329 reloc_plt(Obj_Entry *obj)
330 {
331 const Elf_Rela *relalim;
332 const Elf_Rela *rela;
333
334 relalim = (const Elf_Rela *)((char *)obj->pltrela + obj->pltrelasize);
335 for (rela = obj->pltrela; rela < relalim; rela++) {
336 Elf_Addr *where;
337
338 switch(ELF_R_TYPE(rela->r_info)) {
339 case R_X86_64_JMP_SLOT:
340 /* Relocate the GOT slot pointing into the PLT. */
341 where = (Elf_Addr *)(obj->relocbase + rela->r_offset);
342 *where += (Elf_Addr)obj->relocbase;
343 break;
344
345 case R_X86_64_IRELATIVE:
346 obj->irelative = true;
347 break;
348
349 default:
350 _rtld_error("Unknown relocation type 0x%02x in PLT (%s)",
351 (unsigned int)ELF_R_TYPE(rela->r_info), obj->path);
352 return (-1);
353 }
354 }
355 return 0;
356 }
357
358 /* Relocate the jump slots in an object. */
359 int
reloc_jmpslots(Obj_Entry * obj,int flags,RtldLockState * lockstate)360 reloc_jmpslots(Obj_Entry *obj, int flags, RtldLockState *lockstate)
361 {
362 const Elf_Rela *relalim;
363 const Elf_Rela *rela;
364
365 if (obj->jmpslots_done)
366 return 0;
367 relalim = (const Elf_Rela *)((char *)obj->pltrela + obj->pltrelasize);
368 for (rela = obj->pltrela; rela < relalim; rela++) {
369 Elf_Addr *where, target;
370 const Elf_Sym *def;
371 const Obj_Entry *defobj;
372
373 switch (ELF_R_TYPE(rela->r_info)) {
374 case R_X86_64_JMP_SLOT:
375 where = (Elf_Addr *)(obj->relocbase + rela->r_offset);
376 def = find_symdef(ELF_R_SYM(rela->r_info), obj, &defobj,
377 SYMLOOK_IN_PLT | flags, NULL, lockstate);
378 if (def == NULL)
379 return (-1);
380 if (ELF_ST_TYPE(def->st_info) == STT_GNU_IFUNC) {
381 obj->gnu_ifunc = true;
382 continue;
383 }
384 target = (Elf_Addr)(defobj->relocbase + def->st_value + rela->r_addend);
385 reloc_jmpslot(where, target, defobj, obj, (const Elf_Rel *)rela);
386 break;
387
388 case R_X86_64_IRELATIVE:
389 break;
390
391 default:
392 _rtld_error("Unknown relocation type 0x%02x in PLT (%s)",
393 (unsigned int)ELF_R_TYPE(rela->r_info), obj->path);
394 return (-1);
395 }
396 }
397 obj->jmpslots_done = true;
398 return 0;
399 }
400
401 static void
reloc_iresolve_one(Obj_Entry * obj,const Elf_Rela * rela,RtldLockState * lockstate)402 reloc_iresolve_one(Obj_Entry *obj, const Elf_Rela *rela,
403 RtldLockState *lockstate)
404 {
405 Elf_Addr *where, target, *ptr;
406
407 ptr = (Elf_Addr *)(obj->relocbase + rela->r_addend);
408 where = (Elf_Addr *)(obj->relocbase + rela->r_offset);
409 lock_release(rtld_bind_lock, lockstate);
410 target = ((Elf_Addr (*)(void))ptr)();
411 wlock_acquire(rtld_bind_lock, lockstate);
412 *where = target;
413 }
414
415 int
reloc_iresolve(Obj_Entry * obj,RtldLockState * lockstate)416 reloc_iresolve(Obj_Entry *obj, RtldLockState *lockstate)
417 {
418 const Elf_Rela *relalim;
419 const Elf_Rela *rela;
420
421 if (!obj->irelative)
422 return (0);
423 obj->irelative = false;
424 relalim = (const Elf_Rela *)((char *)obj->pltrela + obj->pltrelasize);
425 for (rela = obj->pltrela; rela < relalim; rela++) {
426 switch (ELF_R_TYPE(rela->r_info)) {
427 case R_X86_64_JMP_SLOT:
428 break;
429
430 case R_X86_64_IRELATIVE:
431 reloc_iresolve_one(obj, rela, lockstate);
432 break;
433 }
434 }
435 return (0);
436 }
437
438 int
reloc_iresolve_nonplt(Obj_Entry * obj,RtldLockState * lockstate)439 reloc_iresolve_nonplt(Obj_Entry *obj, RtldLockState *lockstate)
440 {
441 const Elf_Rela *relalim;
442 const Elf_Rela *rela;
443
444 if (!obj->irelative_nonplt)
445 return (0);
446 obj->irelative_nonplt = false;
447 relalim = (const Elf_Rela *)((char *)obj->rela + obj->relasize);
448 for (rela = obj->rela; rela < relalim; rela++) {
449 if (ELF_R_TYPE(rela->r_info) == R_X86_64_IRELATIVE)
450 reloc_iresolve_one(obj, rela, lockstate);
451 }
452 return (0);
453 }
454
455 int
reloc_gnu_ifunc(Obj_Entry * obj,int flags,RtldLockState * lockstate)456 reloc_gnu_ifunc(Obj_Entry *obj, int flags, RtldLockState *lockstate)
457 {
458 const Elf_Rela *relalim;
459 const Elf_Rela *rela;
460
461 if (!obj->gnu_ifunc)
462 return (0);
463 relalim = (const Elf_Rela *)((char *)obj->pltrela + obj->pltrelasize);
464 for (rela = obj->pltrela; rela < relalim; rela++) {
465 Elf_Addr *where, target;
466 const Elf_Sym *def;
467 const Obj_Entry *defobj;
468
469 switch (ELF_R_TYPE(rela->r_info)) {
470 case R_X86_64_JMP_SLOT:
471 where = (Elf_Addr *)(obj->relocbase + rela->r_offset);
472 def = find_symdef(ELF_R_SYM(rela->r_info), obj, &defobj,
473 SYMLOOK_IN_PLT | flags, NULL, lockstate);
474 if (def == NULL)
475 return (-1);
476 if (ELF_ST_TYPE(def->st_info) != STT_GNU_IFUNC)
477 continue;
478 lock_release(rtld_bind_lock, lockstate);
479 target = (Elf_Addr)rtld_resolve_ifunc(defobj, def);
480 wlock_acquire(rtld_bind_lock, lockstate);
481 reloc_jmpslot(where, target, defobj, obj, (const Elf_Rel *)rela);
482 break;
483 }
484 }
485 obj->gnu_ifunc = false;
486 return (0);
487 }
488
__tls_get_addr(tls_index * ti)489 void *__tls_get_addr(tls_index *ti)
490 {
491 struct tls_tcb *tcb;
492
493 tcb = tls_get_tcb();
494 return tls_get_addr_common((Elf_Addr **)&tcb->tcb_dtv, ti->ti_module, ti->ti_offset);
495 }
496
497 void *
__tls_get_addr_tcb(struct tls_tcb * tcb,tls_index * ti)498 __tls_get_addr_tcb(struct tls_tcb *tcb, tls_index *ti)
499 {
500 return tls_get_addr_common((Elf_Addr **)&tcb->tcb_dtv, ti->ti_module, ti->ti_offset);
501 }
502