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 <machine/sysarch.h>
37
38 #include <dlfcn.h>
39 #include <err.h>
40 #include <errno.h>
41 #include <fcntl.h>
42 #include <stdarg.h>
43 #include <stdio.h>
44 #include <stdlib.h>
45 #include <string.h>
46 #include <unistd.h>
47
48 #include "debug.h"
49 #include "rtld.h"
50 #include "rtld_tls.h"
51
52 /*
53 * Process the special R_X86_64_COPY relocations in the main program. These
54 * copy data from a shared object into a region in the main program's BSS
55 * segment.
56 *
57 * Returns 0 on success, -1 on failure.
58 */
59 int
do_copy_relocations(Obj_Entry * dstobj)60 do_copy_relocations(Obj_Entry *dstobj)
61 {
62 const Elf_Rela *relalim;
63 const Elf_Rela *rela;
64
65 assert(dstobj->mainprog); /* COPY relocations are invalid elsewhere */
66
67 relalim = (const Elf_Rela *) ((caddr_t) dstobj->rela + dstobj->relasize);
68 for (rela = dstobj->rela; rela < relalim; rela++) {
69 if (ELF_R_TYPE(rela->r_info) == R_X86_64_COPY) {
70 void *dstaddr;
71 const Elf_Sym *dstsym;
72 const char *name;
73 size_t size;
74 const void *srcaddr;
75 const Elf_Sym *srcsym;
76 const Obj_Entry *srcobj, *defobj;
77 SymLook req;
78 int res;
79
80 dstaddr = (void *) (dstobj->relocbase + rela->r_offset);
81 dstsym = dstobj->symtab + ELF_R_SYM(rela->r_info);
82 name = dstobj->strtab + dstsym->st_name;
83 size = dstsym->st_size;
84 symlook_init(&req, name);
85 req.ventry = fetch_ventry(dstobj, ELF_R_SYM(rela->r_info));
86 req.flags = SYMLOOK_EARLY;
87
88 for (srcobj = dstobj->next; srcobj != NULL; srcobj = srcobj->next) {
89 res = symlook_obj(&req, srcobj);
90 if (res == 0) {
91 srcsym = req.sym_out;
92 defobj = req.defobj_out;
93 break;
94 }
95 }
96
97 if (srcobj == NULL) {
98 _rtld_error("Undefined symbol \"%s\" referenced from COPY"
99 " relocation in %s", name, dstobj->path);
100 return -1;
101 }
102
103 srcaddr = (const void *) (defobj->relocbase + srcsym->st_value);
104 memcpy(dstaddr, srcaddr, size);
105 }
106 }
107
108 return 0;
109 }
110
111 /* Initialize the special GOT entries. */
112 void
init_pltgot(Obj_Entry * obj)113 init_pltgot(Obj_Entry *obj)
114 {
115 if (obj->pltgot != NULL) {
116 obj->pltgot[1] = (Elf_Addr) obj;
117 obj->pltgot[2] = (Elf_Addr) &_rtld_bind_start;
118 }
119 }
120
121 /* Process the non-PLT relocations. */
122 int
reloc_non_plt(Obj_Entry * obj,Obj_Entry * obj_rtld,int flags,RtldLockState * lockstate)123 reloc_non_plt(Obj_Entry *obj, Obj_Entry *obj_rtld, int flags,
124 RtldLockState *lockstate)
125 {
126 const Elf_Rela *relalim;
127 const Elf_Rela *rela;
128 SymCache *cache;
129 const Elf_Sym *def;
130 const Obj_Entry *defobj;
131 Elf_Addr *where, symval;
132 Elf32_Addr *where32;
133 int r;
134
135 r = -1;
136 /*
137 * The dynamic loader may be called from a thread, we have
138 * limited amounts of stack available so we cannot use alloca().
139 */
140 if (obj != obj_rtld) {
141 cache = calloc(obj->dynsymcount, sizeof(SymCache));
142 /* No need to check for NULL here */
143 } else
144 cache = NULL;
145
146 relalim = (const Elf_Rela *)((caddr_t)obj->rela + obj->relasize);
147 for (rela = obj->rela; rela < relalim; rela++) {
148 /*
149 * First, resolve symbol for relocations which
150 * reference symbols.
151 */
152 switch (ELF_R_TYPE(rela->r_info)) {
153 case R_X86_64_64:
154 case R_X86_64_PC32:
155 case R_X86_64_GLOB_DAT:
156 case R_X86_64_TPOFF64:
157 case R_X86_64_TPOFF32:
158 case R_X86_64_DTPMOD64:
159 case R_X86_64_DTPOFF64:
160 case R_X86_64_DTPOFF32:
161 def = find_symdef(ELF_R_SYM(rela->r_info), obj,
162 &defobj, flags, cache, lockstate);
163 if (def == NULL)
164 goto done;
165 /*
166 * If symbol is IFUNC, only perform relocation
167 * when caller allowed it by passing
168 * SYMLOOK_IFUNC flag. Skip the relocations
169 * otherwise.
170 *
171 * Also error out in case IFUNC relocations
172 * are specified for TLS, which cannot be
173 * usefully interpreted.
174 */
175 if (ELF_ST_TYPE(def->st_info) == STT_GNU_IFUNC) {
176 switch (ELF_R_TYPE(rela->r_info)) {
177 case R_X86_64_64:
178 case R_X86_64_PC32:
179 case R_X86_64_GLOB_DAT:
180 if ((flags & SYMLOOK_IFUNC) == 0) {
181 obj->non_plt_gnu_ifunc = true;
182 continue;
183 }
184 symval = (Elf_Addr)rtld_resolve_ifunc(
185 defobj, def);
186 break;
187 case R_X86_64_TPOFF64:
188 case R_X86_64_TPOFF32:
189 case R_X86_64_DTPMOD64:
190 case R_X86_64_DTPOFF64:
191 case R_X86_64_DTPOFF32:
192 _rtld_error("%s: IFUNC for TLS reloc",
193 obj->path);
194 goto done;
195 }
196 } else {
197 if ((flags & SYMLOOK_IFUNC) != 0)
198 continue;
199 symval = (Elf_Addr)defobj->relocbase +
200 def->st_value;
201 }
202 break;
203 default:
204 if ((flags & SYMLOOK_IFUNC) != 0)
205 continue;
206 break;
207 }
208 where = (Elf_Addr *)(obj->relocbase + rela->r_offset);
209 where32 = (Elf32_Addr *)where;
210
211 switch (ELF_R_TYPE(rela->r_info)) {
212 case R_X86_64_NONE:
213 break;
214 case R_X86_64_64:
215 *where = symval + rela->r_addend;
216 break;
217 case R_X86_64_PC32:
218 /*
219 * I don't think the dynamic linker should
220 * ever see this type of relocation. But the
221 * binutils-2.6 tools sometimes generate it.
222 */
223 *where32 = (Elf32_Addr)(unsigned long)(symval +
224 rela->r_addend - (Elf_Addr)where);
225 break;
226 /* missing: R_X86_64_GOT32 R_X86_64_PLT32 */
227 case R_X86_64_COPY:
228 /*
229 * These are deferred until all other relocations have
230 * been done. All we do here is make sure that the COPY
231 * relocation is not in a shared library. They are allowed
232 * only in executable files.
233 */
234 if (!obj->mainprog) {
235 _rtld_error("%s: Unexpected R_X86_64_COPY "
236 "relocation in shared library", obj->path);
237 goto done;
238 }
239 break;
240 case R_X86_64_GLOB_DAT:
241 *where = symval;
242 break;
243 case R_X86_64_TPOFF64:
244 /*
245 * We lazily allocate offsets for static TLS
246 * as we see the first relocation that
247 * references the TLS block. This allows us to
248 * support (small amounts of) static TLS in
249 * dynamically loaded modules. If we run out
250 * of space, we generate an error.
251 */
252 if (!defobj->tls_done) {
253 if (!allocate_tls_offset((Obj_Entry*) defobj)) {
254 _rtld_error("%s: No space available "
255 "for static Thread Local Storage",
256 obj->path);
257 goto done;
258 }
259 }
260 *where = (Elf_Addr)(def->st_value - defobj->tlsoffset +
261 rela->r_addend);
262 break;
263 case R_X86_64_TPOFF32:
264 /*
265 * We lazily allocate offsets for static TLS
266 * as we see the first relocation that
267 * references the TLS block. This allows us to
268 * support (small amounts of) static TLS in
269 * dynamically loaded modules. If we run out
270 * of space, we generate an error.
271 */
272 if (!defobj->tls_done) {
273 if (!allocate_tls_offset((Obj_Entry*) defobj)) {
274 _rtld_error("%s: No space available "
275 "for static Thread Local Storage",
276 obj->path);
277 goto done;
278 }
279 }
280 *where32 = (Elf32_Addr)(def->st_value -
281 defobj->tlsoffset + rela->r_addend);
282 break;
283 case R_X86_64_DTPMOD64:
284 *where += (Elf_Addr)defobj->tlsindex;
285 break;
286 case R_X86_64_DTPOFF64:
287 *where += (Elf_Addr)(def->st_value + rela->r_addend);
288 break;
289 case R_X86_64_DTPOFF32:
290 *where32 += (Elf32_Addr)(def->st_value +
291 rela->r_addend);
292 break;
293 case R_X86_64_RELATIVE:
294 *where = (Elf_Addr)(obj->relocbase + rela->r_addend);
295 break;
296 /*
297 * missing:
298 * R_X86_64_GOTPCREL, R_X86_64_32, R_X86_64_32S, R_X86_64_16,
299 * R_X86_64_PC16, R_X86_64_8, R_X86_64_PC8
300 */
301 default:
302 _rtld_error("%s: Unsupported relocation type %u"
303 " in non-PLT relocations\n", obj->path,
304 (unsigned int)ELF_R_TYPE(rela->r_info));
305 goto done;
306 }
307 }
308 r = 0;
309 done:
310 free(cache);
311 return (r);
312 }
313
314 /* Process the PLT relocations. */
315 int
reloc_plt(Obj_Entry * obj)316 reloc_plt(Obj_Entry *obj)
317 {
318 const Elf_Rela *relalim;
319 const Elf_Rela *rela;
320
321 relalim = (const Elf_Rela *)((char *)obj->pltrela + obj->pltrelasize);
322 for (rela = obj->pltrela; rela < relalim; rela++) {
323 Elf_Addr *where;
324
325 switch(ELF_R_TYPE(rela->r_info)) {
326 case R_X86_64_JMP_SLOT:
327 /* Relocate the GOT slot pointing into the PLT. */
328 where = (Elf_Addr *)(obj->relocbase + rela->r_offset);
329 *where += (Elf_Addr)obj->relocbase;
330 break;
331
332 case R_X86_64_IRELATIVE:
333 obj->irelative = true;
334 break;
335
336 default:
337 _rtld_error("Unknown relocation type %x in PLT",
338 (unsigned int)ELF_R_TYPE(rela->r_info));
339 return (-1);
340 }
341 }
342 return 0;
343 }
344
345 /* Relocate the jump slots in an object. */
346 int
reloc_jmpslots(Obj_Entry * obj,int flags,RtldLockState * lockstate)347 reloc_jmpslots(Obj_Entry *obj, int flags, RtldLockState *lockstate)
348 {
349 const Elf_Rela *relalim;
350 const Elf_Rela *rela;
351
352 if (obj->jmpslots_done)
353 return 0;
354 relalim = (const Elf_Rela *)((char *)obj->pltrela + obj->pltrelasize);
355 for (rela = obj->pltrela; rela < relalim; rela++) {
356 Elf_Addr *where, target;
357 const Elf_Sym *def;
358 const Obj_Entry *defobj;
359
360 switch (ELF_R_TYPE(rela->r_info)) {
361 case R_X86_64_JMP_SLOT:
362 where = (Elf_Addr *)(obj->relocbase + rela->r_offset);
363 def = find_symdef(ELF_R_SYM(rela->r_info), obj, &defobj,
364 SYMLOOK_IN_PLT | flags, NULL, lockstate);
365 if (def == NULL)
366 return (-1);
367 if (ELF_ST_TYPE(def->st_info) == STT_GNU_IFUNC) {
368 obj->gnu_ifunc = true;
369 continue;
370 }
371 target = (Elf_Addr)(defobj->relocbase + def->st_value + rela->r_addend);
372 reloc_jmpslot(where, target, defobj, obj, (const Elf_Rel *)rela);
373 break;
374
375 case R_X86_64_IRELATIVE:
376 break;
377
378 default:
379 _rtld_error("Unknown relocation type %x in PLT",
380 (unsigned int)ELF_R_TYPE(rela->r_info));
381 return (-1);
382 }
383 }
384 obj->jmpslots_done = true;
385 return 0;
386 }
387
388 int
reloc_iresolve(Obj_Entry * obj,RtldLockState * lockstate)389 reloc_iresolve(Obj_Entry *obj, RtldLockState *lockstate)
390 {
391 const Elf_Rela *relalim;
392 const Elf_Rela *rela;
393
394 if (!obj->irelative)
395 return (0);
396 relalim = (const Elf_Rela *)((char *)obj->pltrela + obj->pltrelasize);
397 for (rela = obj->pltrela; rela < relalim; rela++) {
398 Elf_Addr *where, target, *ptr;
399
400 switch (ELF_R_TYPE(rela->r_info)) {
401 case R_X86_64_JMP_SLOT:
402 break;
403
404 case R_X86_64_IRELATIVE:
405 ptr = (Elf_Addr *)(obj->relocbase + rela->r_addend);
406 where = (Elf_Addr *)(obj->relocbase + rela->r_offset);
407 lock_release(rtld_bind_lock, lockstate);
408 target = ((Elf_Addr (*)(void))ptr)();
409 wlock_acquire(rtld_bind_lock, lockstate);
410 *where = target;
411 break;
412 }
413 }
414 obj->irelative = false;
415 return (0);
416 }
417
418 int
reloc_gnu_ifunc(Obj_Entry * obj,int flags,RtldLockState * lockstate)419 reloc_gnu_ifunc(Obj_Entry *obj, int flags, RtldLockState *lockstate)
420 {
421 const Elf_Rela *relalim;
422 const Elf_Rela *rela;
423
424 if (!obj->gnu_ifunc)
425 return (0);
426 relalim = (const Elf_Rela *)((char *)obj->pltrela + obj->pltrelasize);
427 for (rela = obj->pltrela; rela < relalim; rela++) {
428 Elf_Addr *where, target;
429 const Elf_Sym *def;
430 const Obj_Entry *defobj;
431
432 switch (ELF_R_TYPE(rela->r_info)) {
433 case R_X86_64_JMP_SLOT:
434 where = (Elf_Addr *)(obj->relocbase + rela->r_offset);
435 def = find_symdef(ELF_R_SYM(rela->r_info), obj, &defobj,
436 SYMLOOK_IN_PLT | flags, NULL, lockstate);
437 if (def == NULL)
438 return (-1);
439 if (ELF_ST_TYPE(def->st_info) != STT_GNU_IFUNC)
440 continue;
441 lock_release(rtld_bind_lock, lockstate);
442 target = (Elf_Addr)rtld_resolve_ifunc(defobj, def);
443 wlock_acquire(rtld_bind_lock, lockstate);
444 reloc_jmpslot(where, target, defobj, obj, (const Elf_Rel *)rela);
445 break;
446 }
447 }
448 obj->gnu_ifunc = false;
449 return (0);
450 }
451
452 void
allocate_initial_tls(Obj_Entry * objs)453 allocate_initial_tls(Obj_Entry *objs)
454 {
455 /*
456 * Fix the size of the static TLS block by using the maximum
457 * offset allocated so far and adding a bit for dynamic modules to
458 * use.
459 */
460 tls_static_space = tls_last_offset + RTLD_STATIC_TLS_EXTRA;
461 amd64_set_fsbase(allocate_tls(objs, 0,
462 3*sizeof(Elf_Addr), sizeof(Elf_Addr)));
463 }
464
__tls_get_addr(tls_index * ti)465 void *__tls_get_addr(tls_index *ti)
466 {
467 Elf_Addr** segbase;
468
469 __asm __volatile("movq %%fs:0, %0" : "=r" (segbase));
470
471 return tls_get_addr_common(&segbase[1], ti->ti_module, ti->ti_offset);
472 }
473