1 /* $NetBSD: headers.c,v 1.52 2013/08/03 13:17:05 skrll 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 1.52 2013/08/03 13:17:05 skrll 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 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 Elf_Addr init = 0, fini = 0; 78 79 dbg(("headers: digesting PT_DYNAMIC at %p", obj->dynamic)); 80 for (dynp = obj->dynamic; dynp->d_tag != DT_NULL; ++dynp) { 81 dbg((" d_tag %ld at %p", (long)dynp->d_tag, dynp)); 82 switch (dynp->d_tag) { 83 84 case DT_REL: 85 obj->rel = (const Elf_Rel *) 86 (obj->relocbase + dynp->d_un.d_ptr); 87 break; 88 89 case DT_RELSZ: 90 relsz = dynp->d_un.d_val; 91 break; 92 93 case DT_RELENT: 94 assert(dynp->d_un.d_val == sizeof(Elf_Rel)); 95 break; 96 97 case DT_JMPREL: 98 pltrel = dynp->d_un.d_ptr; 99 break; 100 101 case DT_PLTRELSZ: 102 pltrelsz = dynp->d_un.d_val; 103 break; 104 105 case DT_RELA: 106 obj->rela = (const Elf_Rela *) 107 (obj->relocbase + dynp->d_un.d_ptr); 108 break; 109 110 case DT_RELASZ: 111 relasz = dynp->d_un.d_val; 112 break; 113 114 case DT_RELAENT: 115 assert(dynp->d_un.d_val == sizeof(Elf_Rela)); 116 break; 117 118 case DT_PLTREL: 119 use_pltrel = dynp->d_un.d_val == DT_REL; 120 use_pltrela = dynp->d_un.d_val == DT_RELA; 121 assert(use_pltrel || use_pltrela); 122 break; 123 124 case DT_SYMTAB: 125 obj->symtab = (const Elf_Sym *) 126 (obj->relocbase + dynp->d_un.d_ptr); 127 break; 128 129 case DT_SYMENT: 130 assert(dynp->d_un.d_val == sizeof(Elf_Sym)); 131 break; 132 133 case DT_STRTAB: 134 obj->strtab = (const char *) 135 (obj->relocbase + dynp->d_un.d_ptr); 136 break; 137 138 case DT_STRSZ: 139 obj->strsize = dynp->d_un.d_val; 140 break; 141 142 case DT_VERNEED: 143 obj->verneed = (const Elf_Verneed *) 144 (obj->relocbase + dynp->d_un.d_ptr); 145 break; 146 147 case DT_VERNEEDNUM: 148 obj->verneednum = dynp->d_un.d_val; 149 break; 150 151 case DT_VERDEF: 152 obj->verdef = (const Elf_Verdef *) 153 (obj->relocbase + dynp->d_un.d_ptr); 154 break; 155 156 case DT_VERDEFNUM: 157 obj->verdefnum = dynp->d_un.d_val; 158 break; 159 160 case DT_VERSYM: 161 obj->versyms = (const Elf_Versym *) 162 (obj->relocbase + dynp->d_un.d_ptr); 163 break; 164 165 case DT_HASH: 166 { 167 const Elf_Symindx *hashtab = (const Elf_Symindx *) 168 (obj->relocbase + dynp->d_un.d_ptr); 169 170 if (hashtab[0] > UINT32_MAX) 171 obj->nbuckets = UINT32_MAX; 172 else 173 obj->nbuckets = hashtab[0]; 174 obj->nchains = hashtab[1]; 175 obj->buckets = hashtab + 2; 176 obj->chains = obj->buckets + obj->nbuckets; 177 /* 178 * Should really be in _rtld_relocate_objects, 179 * but _rtld_symlook_obj might be used before. 180 */ 181 if (obj->nbuckets) { 182 fast_divide32_prepare(obj->nbuckets, 183 &obj->nbuckets_m, 184 &obj->nbuckets_s1, 185 &obj->nbuckets_s2); 186 } 187 } 188 break; 189 190 case DT_NEEDED: 191 { 192 Needed_Entry *nep = NEW(Needed_Entry); 193 194 nep->name = dynp->d_un.d_val; 195 nep->obj = NULL; 196 nep->next = NULL; 197 198 *needed_tail = nep; 199 needed_tail = &nep->next; 200 } 201 break; 202 203 case DT_PLTGOT: 204 obj->pltgot = (Elf_Addr *) 205 (obj->relocbase + dynp->d_un.d_ptr); 206 break; 207 208 case DT_TEXTREL: 209 obj->textrel = true; 210 break; 211 212 case DT_SYMBOLIC: 213 obj->symbolic = true; 214 break; 215 216 case DT_RPATH: 217 /* 218 * We have to wait until later to process this, because 219 * we might not have gotten the address of the string 220 * table yet. 221 */ 222 dyn_rpath = dynp; 223 break; 224 225 case DT_SONAME: 226 dyn_soname = dynp; 227 break; 228 229 case DT_INIT: 230 init = dynp->d_un.d_ptr; 231 break; 232 233 #ifdef HAVE_INITFINI_ARRAY 234 case DT_INIT_ARRAY: 235 obj->init_array = 236 (fptr_t *)(obj->relocbase + dynp->d_un.d_ptr); 237 dbg(("headers: DT_INIT_ARRAY at %p", 238 obj->init_array)); 239 break; 240 241 case DT_INIT_ARRAYSZ: 242 obj->init_arraysz = dynp->d_un.d_val / sizeof(fptr_t); 243 dbg(("headers: DT_INIT_ARRAYZ %zu", 244 obj->init_arraysz)); 245 break; 246 #endif 247 248 case DT_FINI: 249 fini = dynp->d_un.d_ptr; 250 break; 251 252 #ifdef HAVE_INITFINI_ARRAY 253 case DT_FINI_ARRAY: 254 obj->fini_array = 255 (fptr_t *)(obj->relocbase + dynp->d_un.d_ptr); 256 dbg(("headers: DT_FINI_ARRAY at %p", 257 obj->fini_array)); 258 break; 259 260 case DT_FINI_ARRAYSZ: 261 obj->fini_arraysz = dynp->d_un.d_val / sizeof(fptr_t); 262 dbg(("headers: DT_FINI_ARRAYZ %zu", 263 obj->fini_arraysz)); 264 break; 265 #endif 266 267 /* 268 * Don't process DT_DEBUG on MIPS as the dynamic section 269 * is mapped read-only. DT_MIPS_RLD_MAP is used instead. 270 * XXX: n32/n64 may use DT_DEBUG, not sure yet. 271 */ 272 #ifndef __mips__ 273 case DT_DEBUG: 274 #ifdef RTLD_LOADER 275 dynp->d_un.d_ptr = (Elf_Addr)&_rtld_debug; 276 #endif 277 break; 278 #endif 279 280 #ifdef __mips__ 281 case DT_MIPS_LOCAL_GOTNO: 282 obj->local_gotno = dynp->d_un.d_val; 283 break; 284 285 case DT_MIPS_SYMTABNO: 286 obj->symtabno = dynp->d_un.d_val; 287 break; 288 289 case DT_MIPS_GOTSYM: 290 obj->gotsym = dynp->d_un.d_val; 291 break; 292 293 case DT_MIPS_RLD_MAP: 294 #ifdef RTLD_LOADER 295 *((Elf_Addr *)(dynp->d_un.d_ptr)) = (Elf_Addr) 296 &_rtld_debug; 297 #endif 298 break; 299 #endif 300 #ifdef __powerpc__ 301 case DT_PPC_GOT: 302 obj->gotptr = (Elf_Addr *)(obj->relocbase + dynp->d_un.d_ptr); 303 break; 304 #endif 305 case DT_FLAGS_1: 306 obj->z_now = 307 ((dynp->d_un.d_val & DF_1_BIND_NOW) != 0); 308 obj->z_nodelete = 309 ((dynp->d_un.d_val & DF_1_NODELETE) != 0); 310 obj->z_initfirst = 311 ((dynp->d_un.d_val & DF_1_INITFIRST) != 0); 312 obj->z_noopen = 313 ((dynp->d_un.d_val & DF_1_NOOPEN) != 0); 314 break; 315 } 316 } 317 318 obj->rellim = (const Elf_Rel *)((const uint8_t *)obj->rel + relsz); 319 obj->relalim = (const Elf_Rela *)((const uint8_t *)obj->rela + relasz); 320 if (use_pltrel) { 321 obj->pltrel = (const Elf_Rel *)(obj->relocbase + pltrel); 322 obj->pltrellim = (const Elf_Rel *)(obj->relocbase + pltrel + pltrelsz); 323 obj->pltrelalim = 0; 324 /* On PPC and SPARC, at least, REL(A)SZ may include JMPREL. 325 Trim rel(a)lim to save time later. */ 326 if (obj->rellim && obj->pltrel && 327 obj->rellim > obj->pltrel && 328 obj->rellim <= obj->pltrellim) 329 obj->rellim = obj->pltrel; 330 } else if (use_pltrela) { 331 obj->pltrela = (const Elf_Rela *)(obj->relocbase + pltrel); 332 obj->pltrellim = 0; 333 obj->pltrelalim = (const Elf_Rela *)(obj->relocbase + pltrel + pltrelsz); 334 /* On PPC and SPARC, at least, REL(A)SZ may include JMPREL. 335 Trim rel(a)lim to save time later. */ 336 if (obj->relalim && obj->pltrela && 337 obj->relalim > obj->pltrela && 338 obj->relalim <= obj->pltrelalim) 339 obj->relalim = obj->pltrela; 340 } 341 342 #if defined(RTLD_LOADER) && defined(__HAVE_FUNCTION_DESCRIPTORS) 343 if (init != 0) 344 obj->init = (void (*)(void)) 345 _rtld_function_descriptor_alloc(obj, NULL, init); 346 if (fini != 0) 347 obj->fini = (void (*)(void)) 348 _rtld_function_descriptor_alloc(obj, NULL, fini); 349 #else 350 if (init != 0) 351 obj->init = (void (*)(void)) 352 (obj->relocbase + init); 353 if (fini != 0) 354 obj->fini = (void (*)(void)) 355 (obj->relocbase + fini); 356 #endif 357 358 if (dyn_rpath != NULL) { 359 _rtld_add_paths(execname, &obj->rpaths, obj->strtab + 360 dyn_rpath->d_un.d_val); 361 } 362 if (dyn_soname != NULL) { 363 _rtld_object_add_name(obj, obj->strtab + 364 dyn_soname->d_un.d_val); 365 } 366 } 367 368 /* 369 * Process a shared object's program header. This is used only for the 370 * main program, when the kernel has already loaded the main program 371 * into memory before calling the dynamic linker. It creates and 372 * returns an Obj_Entry structure. 373 */ 374 Obj_Entry * 375 _rtld_digest_phdr(const Elf_Phdr *phdr, int phnum, caddr_t entry) 376 { 377 Obj_Entry *obj; 378 const Elf_Phdr *phlimit = phdr + phnum; 379 const Elf_Phdr *ph; 380 int nsegs = 0; 381 Elf_Addr vaddr; 382 383 obj = _rtld_obj_new(); 384 385 for (ph = phdr; ph < phlimit; ++ph) { 386 if (ph->p_type != PT_PHDR) 387 continue; 388 389 obj->phdr = (void *)(uintptr_t)ph->p_vaddr; 390 obj->phsize = ph->p_memsz; 391 obj->relocbase = (caddr_t)((uintptr_t)phdr - (uintptr_t)ph->p_vaddr); 392 dbg(("headers: phdr %p (%p) phsize %zu relocbase %p", 393 obj->phdr, phdr, obj->phsize, obj->relocbase)); 394 break; 395 } 396 397 for (ph = phdr; ph < phlimit; ++ph) { 398 vaddr = (Elf_Addr)(uintptr_t)(obj->relocbase + ph->p_vaddr); 399 switch (ph->p_type) { 400 401 case PT_INTERP: 402 obj->interp = (const char *)(uintptr_t)vaddr; 403 dbg(("headers: %s %p phsize %" PRImemsz, 404 "PT_INTERP", (void *)(uintptr_t)vaddr, 405 ph->p_memsz)); 406 break; 407 408 case PT_LOAD: 409 assert(nsegs < 2); 410 if (nsegs == 0) { /* First load segment */ 411 obj->vaddrbase = round_down(vaddr); 412 obj->mapbase = (caddr_t)(uintptr_t)obj->vaddrbase; 413 obj->textsize = round_up(vaddr + ph->p_memsz) - 414 obj->vaddrbase; 415 } else { /* Last load segment */ 416 obj->mapsize = round_up(vaddr + ph->p_memsz) - 417 obj->vaddrbase; 418 } 419 ++nsegs; 420 dbg(("headers: %s %p phsize %" PRImemsz, 421 "PT_LOAD", (void *)(uintptr_t)vaddr, 422 ph->p_memsz)); 423 break; 424 425 case PT_DYNAMIC: 426 obj->dynamic = (Elf_Dyn *)(uintptr_t)vaddr; 427 dbg(("headers: %s %p phsize %" PRImemsz, 428 "PT_DYNAMIC", (void *)(uintptr_t)vaddr, 429 ph->p_memsz)); 430 break; 431 432 #if defined(__HAVE_TLS_VARIANT_I) || defined(__HAVE_TLS_VARIANT_II) 433 case PT_TLS: 434 obj->tlsindex = 1; 435 obj->tlssize = ph->p_memsz; 436 obj->tlsalign = ph->p_align; 437 obj->tlsinitsize = ph->p_filesz; 438 obj->tlsinit = (void *)(uintptr_t)ph->p_vaddr; 439 dbg(("headers: %s %p phsize %" PRImemsz, 440 "PT_TLS", (void *)(uintptr_t)vaddr, 441 ph->p_memsz)); 442 break; 443 #endif 444 #ifdef __ARM_EABI__ 445 case PT_ARM_EXIDX: 446 obj->exidx_start = (void *)(uintptr_t)vaddr; 447 obj->exidx_sz = ph->p_memsz; 448 dbg(("headers: %s %p phsize %" PRImemsz, 449 "PT_ARM_EXIDX", (void *)(uintptr_t)vaddr, 450 ph->p_memsz)); 451 break; 452 #endif 453 } 454 } 455 assert(nsegs == 2); 456 457 obj->entry = entry; 458 return obj; 459 } 460