headers.c revision 1.50
1 /* $NetBSD: headers.c,v 1.50 2013/05/06 08:02:20 skrll Exp $ */ 2 3 /* 4 * Copyright 1996 John D. Polstra. 5 * Copyright 1996 Matt Thomas <matt (at) 3am-software.com> 6 * Copyright 2002 Charles M. Hannum <root (at) 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 (at) polstra.com>. 39 */ 40 41 #include <sys/cdefs.h> 42 #ifndef lint 43 __RCSID("$NetBSD: headers.c,v 1.50 2013/05/06 08:02:20 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_rpath = NULL; 72 bool use_pltrel = false; 73 bool use_pltrela = false; 74 Elf_Addr relsz = 0, relasz = 0; 75 Elf_Addr pltrel = 0, pltrelsz = 0; 76 Elf_Addr init = 0, fini = 0; 77 78 dbg(("headers: digesting PT_DYNAMIC at %p", obj->dynamic)); 79 for (dynp = obj->dynamic; dynp->d_tag != DT_NULL; ++dynp) { 80 dbg((" d_tag %ld at %p", (long)dynp->d_tag, dynp)); 81 switch (dynp->d_tag) { 82 83 case DT_REL: 84 obj->rel = (const Elf_Rel *) 85 (obj->relocbase + dynp->d_un.d_ptr); 86 break; 87 88 case DT_RELSZ: 89 relsz = dynp->d_un.d_val; 90 break; 91 92 case DT_RELENT: 93 assert(dynp->d_un.d_val == sizeof(Elf_Rel)); 94 break; 95 96 case DT_JMPREL: 97 pltrel = dynp->d_un.d_ptr; 98 break; 99 100 case DT_PLTRELSZ: 101 pltrelsz = dynp->d_un.d_val; 102 break; 103 104 case DT_RELA: 105 obj->rela = (const Elf_Rela *) 106 (obj->relocbase + dynp->d_un.d_ptr); 107 break; 108 109 case DT_RELASZ: 110 relasz = dynp->d_un.d_val; 111 break; 112 113 case DT_RELAENT: 114 assert(dynp->d_un.d_val == sizeof(Elf_Rela)); 115 break; 116 117 case DT_PLTREL: 118 use_pltrel = dynp->d_un.d_val == DT_REL; 119 use_pltrela = dynp->d_un.d_val == DT_RELA; 120 assert(use_pltrel || use_pltrela); 121 break; 122 123 case DT_SYMTAB: 124 obj->symtab = (const Elf_Sym *) 125 (obj->relocbase + dynp->d_un.d_ptr); 126 break; 127 128 case DT_SYMENT: 129 assert(dynp->d_un.d_val == sizeof(Elf_Sym)); 130 break; 131 132 case DT_STRTAB: 133 obj->strtab = (const char *) 134 (obj->relocbase + dynp->d_un.d_ptr); 135 break; 136 137 case DT_STRSZ: 138 obj->strsize = dynp->d_un.d_val; 139 break; 140 141 case DT_VERNEED: 142 obj->verneed = (const Elf_Verneed *) 143 (obj->relocbase + dynp->d_un.d_ptr); 144 break; 145 146 case DT_VERNEEDNUM: 147 obj->verneednum = dynp->d_un.d_val; 148 break; 149 150 case DT_VERDEF: 151 obj->verdef = (const Elf_Verdef *) 152 (obj->relocbase + dynp->d_un.d_ptr); 153 break; 154 155 case DT_VERDEFNUM: 156 obj->verdefnum = dynp->d_un.d_val; 157 break; 158 159 case DT_VERSYM: 160 obj->versyms = (const Elf_Versym *) 161 (obj->relocbase + dynp->d_un.d_ptr); 162 break; 163 164 case DT_HASH: 165 { 166 const Elf_Symindx *hashtab = (const Elf_Symindx *) 167 (obj->relocbase + dynp->d_un.d_ptr); 168 169 if (hashtab[0] > UINT32_MAX) 170 obj->nbuckets = UINT32_MAX; 171 else 172 obj->nbuckets = hashtab[0]; 173 obj->nchains = hashtab[1]; 174 obj->buckets = hashtab + 2; 175 obj->chains = obj->buckets + obj->nbuckets; 176 /* 177 * Should really be in _rtld_relocate_objects, 178 * but _rtld_symlook_obj might be used before. 179 */ 180 if (obj->nbuckets) { 181 fast_divide32_prepare(obj->nbuckets, 182 &obj->nbuckets_m, 183 &obj->nbuckets_s1, 184 &obj->nbuckets_s2); 185 } 186 } 187 break; 188 189 case DT_NEEDED: 190 { 191 Needed_Entry *nep = NEW(Needed_Entry); 192 193 nep->name = dynp->d_un.d_val; 194 nep->obj = NULL; 195 nep->next = NULL; 196 197 *needed_tail = nep; 198 needed_tail = &nep->next; 199 } 200 break; 201 202 case DT_PLTGOT: 203 obj->pltgot = (Elf_Addr *) 204 (obj->relocbase + dynp->d_un.d_ptr); 205 break; 206 207 case DT_TEXTREL: 208 obj->textrel = true; 209 break; 210 211 case DT_SYMBOLIC: 212 obj->symbolic = true; 213 break; 214 215 case DT_RPATH: 216 /* 217 * We have to wait until later to process this, because 218 * we might not have gotten the address of the string 219 * table yet. 220 */ 221 dyn_rpath = dynp; 222 break; 223 224 case DT_SONAME: 225 /* Not used by the dynamic linker. */ 226 break; 227 228 case DT_INIT: 229 init = dynp->d_un.d_ptr; 230 break; 231 232 #ifdef HAVE_INITFINI_ARRAY 233 case DT_INIT_ARRAY: 234 obj->init_array = 235 (fptr_t *)(obj->relocbase + dynp->d_un.d_ptr); 236 dbg(("headers: DT_INIT_ARRAY at %p", 237 obj->init_array)); 238 break; 239 240 case DT_INIT_ARRAYSZ: 241 obj->init_arraysz = dynp->d_un.d_val / sizeof(fptr_t); 242 dbg(("headers: DT_INIT_ARRAYZ %zu", 243 obj->init_arraysz)); 244 break; 245 #endif 246 247 case DT_FINI: 248 fini = dynp->d_un.d_ptr; 249 break; 250 251 #ifdef HAVE_INITFINI_ARRAY 252 case DT_FINI_ARRAY: 253 obj->fini_array = 254 (fptr_t *)(obj->relocbase + dynp->d_un.d_ptr); 255 dbg(("headers: DT_FINI_ARRAY at %p", 256 obj->fini_array)); 257 break; 258 259 case DT_FINI_ARRAYSZ: 260 obj->fini_arraysz = dynp->d_un.d_val / sizeof(fptr_t); 261 dbg(("headers: DT_FINI_ARRAYZ %zu", 262 obj->fini_arraysz)); 263 break; 264 #endif 265 266 /* 267 * Don't process DT_DEBUG on MIPS as the dynamic section 268 * is mapped read-only. DT_MIPS_RLD_MAP is used instead. 269 * XXX: n32/n64 may use DT_DEBUG, not sure yet. 270 */ 271 #ifndef __mips__ 272 case DT_DEBUG: 273 #ifdef RTLD_LOADER 274 dynp->d_un.d_ptr = (Elf_Addr)&_rtld_debug; 275 #endif 276 break; 277 #endif 278 279 #ifdef __mips__ 280 case DT_MIPS_LOCAL_GOTNO: 281 obj->local_gotno = dynp->d_un.d_val; 282 break; 283 284 case DT_MIPS_SYMTABNO: 285 obj->symtabno = dynp->d_un.d_val; 286 break; 287 288 case DT_MIPS_GOTSYM: 289 obj->gotsym = dynp->d_un.d_val; 290 break; 291 292 case DT_MIPS_RLD_MAP: 293 #ifdef RTLD_LOADER 294 *((Elf_Addr *)(dynp->d_un.d_ptr)) = (Elf_Addr) 295 &_rtld_debug; 296 #endif 297 break; 298 #endif 299 #ifdef __powerpc__ 300 case DT_PPC_GOT: 301 obj->gotptr = (Elf_Addr *)(obj->relocbase + dynp->d_un.d_ptr); 302 break; 303 #endif 304 case DT_FLAGS_1: 305 obj->z_now = 306 ((dynp->d_un.d_val & DF_1_BIND_NOW) != 0); 307 obj->z_nodelete = 308 ((dynp->d_un.d_val & DF_1_NODELETE) != 0); 309 obj->z_initfirst = 310 ((dynp->d_un.d_val & DF_1_INITFIRST) != 0); 311 obj->z_noopen = 312 ((dynp->d_un.d_val & DF_1_NOOPEN) != 0); 313 break; 314 } 315 } 316 317 obj->rellim = (const Elf_Rel *)((const uint8_t *)obj->rel + relsz); 318 obj->relalim = (const Elf_Rela *)((const uint8_t *)obj->rela + relasz); 319 if (use_pltrel) { 320 obj->pltrel = (const Elf_Rel *)(obj->relocbase + pltrel); 321 obj->pltrellim = (const Elf_Rel *)(obj->relocbase + pltrel + pltrelsz); 322 obj->pltrelalim = 0; 323 /* On PPC and SPARC, at least, REL(A)SZ may include JMPREL. 324 Trim rel(a)lim to save time later. */ 325 if (obj->rellim && obj->pltrel && 326 obj->rellim > obj->pltrel && 327 obj->rellim <= obj->pltrellim) 328 obj->rellim = obj->pltrel; 329 } else if (use_pltrela) { 330 obj->pltrela = (const Elf_Rela *)(obj->relocbase + pltrel); 331 obj->pltrellim = 0; 332 obj->pltrelalim = (const Elf_Rela *)(obj->relocbase + pltrel + pltrelsz); 333 /* On PPC and SPARC, at least, REL(A)SZ may include JMPREL. 334 Trim rel(a)lim to save time later. */ 335 if (obj->relalim && obj->pltrela && 336 obj->relalim > obj->pltrela && 337 obj->relalim <= obj->pltrelalim) 338 obj->relalim = obj->pltrela; 339 } 340 341 #if defined(RTLD_LOADER) && defined(__HAVE_FUNCTION_DESCRIPTORS) 342 if (init != 0) 343 obj->init = (void (*)(void)) 344 _rtld_function_descriptor_alloc(obj, NULL, init); 345 if (fini != 0) 346 obj->fini = (void (*)(void)) 347 _rtld_function_descriptor_alloc(obj, NULL, fini); 348 #else 349 if (init != 0) 350 obj->init = (void (*)(void)) 351 (obj->relocbase + init); 352 if (fini != 0) 353 obj->fini = (void (*)(void)) 354 (obj->relocbase + fini); 355 #endif 356 357 if (dyn_rpath != NULL) { 358 _rtld_add_paths(execname, &obj->rpaths, obj->strtab + 359 dyn_rpath->d_un.d_val); 360 } 361 } 362 363 /* 364 * Process a shared object's program header. This is used only for the 365 * main program, when the kernel has already loaded the main program 366 * into memory before calling the dynamic linker. It creates and 367 * returns an Obj_Entry structure. 368 */ 369 Obj_Entry * 370 _rtld_digest_phdr(const Elf_Phdr *phdr, int phnum, caddr_t entry) 371 { 372 Obj_Entry *obj; 373 const Elf_Phdr *phlimit = phdr + phnum; 374 const Elf_Phdr *ph; 375 int nsegs = 0; 376 Elf_Addr vaddr; 377 378 obj = _rtld_obj_new(); 379 380 for (ph = phdr; ph < phlimit; ++ph) { 381 if (ph->p_type != PT_PHDR) 382 continue; 383 384 obj->phdr = (void *)(uintptr_t)ph->p_vaddr; 385 obj->phsize = ph->p_memsz; 386 obj->relocbase = (caddr_t)((uintptr_t)phdr - (uintptr_t)ph->p_vaddr); 387 dbg(("headers: phdr %p (%p) phsize %zu relocbase %p", 388 obj->phdr, phdr, obj->phsize, obj->relocbase)); 389 break; 390 } 391 392 for (ph = phdr; ph < phlimit; ++ph) { 393 vaddr = (Elf_Addr)(uintptr_t)(obj->relocbase + ph->p_vaddr); 394 switch (ph->p_type) { 395 396 case PT_INTERP: 397 obj->interp = (const char *)(uintptr_t)vaddr; 398 dbg(("headers: %s %p phsize %zu", 399 "PT_INTERP", (void *)(uintptr_t)vaddr, 400 ph->p_memsz)); 401 break; 402 403 case PT_LOAD: 404 assert(nsegs < 2); 405 if (nsegs == 0) { /* First load segment */ 406 obj->vaddrbase = round_down(vaddr); 407 obj->mapbase = (caddr_t)(uintptr_t)obj->vaddrbase; 408 obj->textsize = round_up(vaddr + ph->p_memsz) - 409 obj->vaddrbase; 410 } else { /* Last load segment */ 411 obj->mapsize = round_up(vaddr + ph->p_memsz) - 412 obj->vaddrbase; 413 } 414 ++nsegs; 415 dbg(("headers: %s %p phsize %zu", 416 "PT_LOAD", (void *)(uintptr_t)vaddr, 417 ph->p_memsz)); 418 break; 419 420 case PT_DYNAMIC: 421 obj->dynamic = (Elf_Dyn *)(uintptr_t)vaddr; 422 dbg(("headers: %s %p phsize %zu", 423 "PT_DYNAMIC", (void *)(uintptr_t)vaddr, 424 ph->p_memsz)); 425 break; 426 427 #if defined(__HAVE_TLS_VARIANT_I) || defined(__HAVE_TLS_VARIANT_II) 428 case PT_TLS: 429 obj->tlsindex = 1; 430 obj->tlssize = ph->p_memsz; 431 obj->tlsalign = ph->p_align; 432 obj->tlsinitsize = ph->p_filesz; 433 obj->tlsinit = (void *)(uintptr_t)ph->p_vaddr; 434 dbg(("headers: %s %p phsize %zu", 435 "PT_TLS", (void *)(uintptr_t)vaddr, 436 ph->p_memsz)); 437 break; 438 #endif 439 #ifdef __ARM_EABI__ 440 case PT_ARM_EXIDX: 441 obj->exidx_start = (void *)(uintptr_t)vaddr; 442 obj->exidx_sz = ph->p_memsz; 443 dbg(("headers: %s %p phsize %zu", 444 "PT_ARM_EXIDX", (void *)(uintptr_t)vaddr, 445 ph->p_memsz)); 446 break; 447 #endif 448 } 449 } 450 assert(nsegs == 2); 451 452 obj->entry = entry; 453 return obj; 454 } 455
Indexes created Wed Oct 15 16:09:53 GMT 2025