headers.c revision 1.48
1 /* $NetBSD: headers.c,v 1.48 2013/05/02 21:11:03 matt 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 1.48 2013/05/02 21:11:03 matt 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 for (dynp = obj->dynamic; dynp->d_tag != DT_NULL; ++dynp) { 79 switch (dynp->d_tag) { 80 81 case DT_REL: 82 obj->rel = (const Elf_Rel *) 83 (obj->relocbase + dynp->d_un.d_ptr); 84 break; 85 86 case DT_RELSZ: 87 relsz = dynp->d_un.d_val; 88 break; 89 90 case DT_RELENT: 91 assert(dynp->d_un.d_val == sizeof(Elf_Rel)); 92 break; 93 94 case DT_JMPREL: 95 pltrel = dynp->d_un.d_ptr; 96 break; 97 98 case DT_PLTRELSZ: 99 pltrelsz = dynp->d_un.d_val; 100 break; 101 102 case DT_RELA: 103 obj->rela = (const Elf_Rela *) 104 (obj->relocbase + dynp->d_un.d_ptr); 105 break; 106 107 case DT_RELASZ: 108 relasz = dynp->d_un.d_val; 109 break; 110 111 case DT_RELAENT: 112 assert(dynp->d_un.d_val == sizeof(Elf_Rela)); 113 break; 114 115 case DT_PLTREL: 116 use_pltrel = dynp->d_un.d_val == DT_REL; 117 use_pltrela = dynp->d_un.d_val == DT_RELA; 118 assert(use_pltrel || use_pltrela); 119 break; 120 121 case DT_SYMTAB: 122 obj->symtab = (const Elf_Sym *) 123 (obj->relocbase + dynp->d_un.d_ptr); 124 break; 125 126 case DT_SYMENT: 127 assert(dynp->d_un.d_val == sizeof(Elf_Sym)); 128 break; 129 130 case DT_STRTAB: 131 obj->strtab = (const char *) 132 (obj->relocbase + dynp->d_un.d_ptr); 133 break; 134 135 case DT_STRSZ: 136 obj->strsize = dynp->d_un.d_val; 137 break; 138 139 case DT_VERNEED: 140 obj->verneed = (const Elf_Verneed *) 141 (obj->relocbase + dynp->d_un.d_ptr); 142 break; 143 144 case DT_VERNEEDNUM: 145 obj->verneednum = dynp->d_un.d_val; 146 break; 147 148 case DT_VERDEF: 149 obj->verdef = (const Elf_Verdef *) 150 (obj->relocbase + dynp->d_un.d_ptr); 151 break; 152 153 case DT_VERDEFNUM: 154 obj->verdefnum = dynp->d_un.d_val; 155 break; 156 157 case DT_VERSYM: 158 obj->versyms = (const Elf_Versym *) 159 (obj->relocbase + dynp->d_un.d_ptr); 160 break; 161 162 case DT_HASH: 163 { 164 const Elf_Symindx *hashtab = (const Elf_Symindx *) 165 (obj->relocbase + dynp->d_un.d_ptr); 166 167 if (hashtab[0] > UINT32_MAX) 168 obj->nbuckets = UINT32_MAX; 169 else 170 obj->nbuckets = hashtab[0]; 171 obj->nchains = hashtab[1]; 172 obj->buckets = hashtab + 2; 173 obj->chains = obj->buckets + obj->nbuckets; 174 /* 175 * Should really be in _rtld_relocate_objects, 176 * but _rtld_symlook_obj might be used before. 177 */ 178 if (obj->nbuckets) { 179 fast_divide32_prepare(obj->nbuckets, 180 &obj->nbuckets_m, 181 &obj->nbuckets_s1, 182 &obj->nbuckets_s2); 183 } 184 } 185 break; 186 187 case DT_NEEDED: 188 { 189 Needed_Entry *nep = NEW(Needed_Entry); 190 191 nep->name = dynp->d_un.d_val; 192 nep->obj = NULL; 193 nep->next = NULL; 194 195 *needed_tail = nep; 196 needed_tail = &nep->next; 197 } 198 break; 199 200 case DT_PLTGOT: 201 obj->pltgot = (Elf_Addr *) 202 (obj->relocbase + dynp->d_un.d_ptr); 203 break; 204 205 case DT_TEXTREL: 206 obj->textrel = true; 207 break; 208 209 case DT_SYMBOLIC: 210 obj->symbolic = true; 211 break; 212 213 case DT_RPATH: 214 /* 215 * We have to wait until later to process this, because 216 * we might not have gotten the address of the string 217 * table yet. 218 */ 219 dyn_rpath = dynp; 220 break; 221 222 case DT_SONAME: 223 /* Not used by the dynamic linker. */ 224 break; 225 226 case DT_INIT: 227 init = dynp->d_un.d_ptr; 228 break; 229 230 #ifdef HAVE_INITFINI_ARRAY 231 case DT_INIT_ARRAY: 232 obj->init_array = 233 (fptr_t *)(obj->relocbase + dynp->d_un.d_ptr); 234 break; 235 236 case DT_INIT_ARRAYSZ: 237 obj->init_arraysz = dynp->d_un.d_val / sizeof(fptr_t); 238 break; 239 #endif 240 241 case DT_FINI: 242 fini = dynp->d_un.d_ptr; 243 break; 244 245 #ifdef HAVE_INITFINI_ARRAY 246 case DT_FINI_ARRAY: 247 obj->fini_array = 248 (fptr_t *)(obj->relocbase + dynp->d_un.d_ptr); 249 break; 250 251 case DT_FINI_ARRAYSZ: 252 obj->fini_arraysz = dynp->d_un.d_val / sizeof(fptr_t); 253 break; 254 #endif 255 256 /* 257 * Don't process DT_DEBUG on MIPS as the dynamic section 258 * is mapped read-only. DT_MIPS_RLD_MAP is used instead. 259 * XXX: n32/n64 may use DT_DEBUG, not sure yet. 260 */ 261 #ifndef __mips__ 262 case DT_DEBUG: 263 #ifdef RTLD_LOADER 264 dynp->d_un.d_ptr = (Elf_Addr)&_rtld_debug; 265 #endif 266 break; 267 #endif 268 269 #ifdef __mips__ 270 case DT_MIPS_LOCAL_GOTNO: 271 obj->local_gotno = dynp->d_un.d_val; 272 break; 273 274 case DT_MIPS_SYMTABNO: 275 obj->symtabno = dynp->d_un.d_val; 276 break; 277 278 case DT_MIPS_GOTSYM: 279 obj->gotsym = dynp->d_un.d_val; 280 break; 281 282 case DT_MIPS_RLD_MAP: 283 #ifdef RTLD_LOADER 284 *((Elf_Addr *)(dynp->d_un.d_ptr)) = (Elf_Addr) 285 &_rtld_debug; 286 #endif 287 break; 288 #endif 289 #ifdef __powerpc__ 290 case DT_PPC_GOT: 291 obj->gotptr = (Elf_Addr *)(obj->relocbase + dynp->d_un.d_ptr); 292 break; 293 #endif 294 case DT_FLAGS_1: 295 obj->z_now = 296 ((dynp->d_un.d_val & DF_1_BIND_NOW) != 0); 297 obj->z_nodelete = 298 ((dynp->d_un.d_val & DF_1_NODELETE) != 0); 299 obj->z_initfirst = 300 ((dynp->d_un.d_val & DF_1_INITFIRST) != 0); 301 obj->z_noopen = 302 ((dynp->d_un.d_val & DF_1_NOOPEN) != 0); 303 break; 304 } 305 } 306 307 obj->rellim = (const Elf_Rel *)((const uint8_t *)obj->rel + relsz); 308 obj->relalim = (const Elf_Rela *)((const uint8_t *)obj->rela + relasz); 309 if (use_pltrel) { 310 obj->pltrel = (const Elf_Rel *)(obj->relocbase + pltrel); 311 obj->pltrellim = (const Elf_Rel *)(obj->relocbase + pltrel + pltrelsz); 312 obj->pltrelalim = 0; 313 /* On PPC and SPARC, at least, REL(A)SZ may include JMPREL. 314 Trim rel(a)lim to save time later. */ 315 if (obj->rellim && obj->pltrel && 316 obj->rellim > obj->pltrel && 317 obj->rellim <= obj->pltrellim) 318 obj->rellim = obj->pltrel; 319 } else if (use_pltrela) { 320 obj->pltrela = (const Elf_Rela *)(obj->relocbase + pltrel); 321 obj->pltrellim = 0; 322 obj->pltrelalim = (const Elf_Rela *)(obj->relocbase + pltrel + pltrelsz); 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->relalim && obj->pltrela && 326 obj->relalim > obj->pltrela && 327 obj->relalim <= obj->pltrelalim) 328 obj->relalim = obj->pltrela; 329 } 330 331 #if defined(RTLD_LOADER) && defined(__HAVE_FUNCTION_DESCRIPTORS) 332 if (init != 0) 333 obj->init = (void (*)(void)) 334 _rtld_function_descriptor_alloc(obj, NULL, init); 335 if (fini != 0) 336 obj->fini = (void (*)(void)) 337 _rtld_function_descriptor_alloc(obj, NULL, fini); 338 #else 339 if (init != 0) 340 obj->init = (void (*)(void)) 341 (obj->relocbase + init); 342 if (fini != 0) 343 obj->fini = (void (*)(void)) 344 (obj->relocbase + fini); 345 #endif 346 347 if (dyn_rpath != NULL) { 348 _rtld_add_paths(execname, &obj->rpaths, obj->strtab + 349 dyn_rpath->d_un.d_val); 350 } 351 } 352 353 /* 354 * Process a shared object's program header. This is used only for the 355 * main program, when the kernel has already loaded the main program 356 * into memory before calling the dynamic linker. It creates and 357 * returns an Obj_Entry structure. 358 */ 359 Obj_Entry * 360 _rtld_digest_phdr(const Elf_Phdr *phdr, int phnum, caddr_t entry) 361 { 362 Obj_Entry *obj; 363 const Elf_Phdr *phlimit = phdr + phnum; 364 const Elf_Phdr *ph; 365 int nsegs = 0; 366 Elf_Addr vaddr; 367 368 obj = _rtld_obj_new(); 369 370 for (ph = phdr; ph < phlimit; ++ph) { 371 if (ph->p_type != PT_PHDR) 372 continue; 373 374 obj->phdr = (void *)(uintptr_t)ph->p_vaddr; 375 obj->phsize = ph->p_memsz; 376 obj->relocbase = (caddr_t)((uintptr_t)phdr - (uintptr_t)ph->p_vaddr); 377 dbg(("headers: phdr %p (%p) phsize %zu relocbase %lx", 378 obj->phdr, phdr, obj->phsize, (long)obj->relocbase)); 379 break; 380 } 381 382 for (ph = phdr; ph < phlimit; ++ph) { 383 vaddr = (Elf_Addr)(uintptr_t)(obj->relocbase + ph->p_vaddr); 384 switch (ph->p_type) { 385 386 case PT_INTERP: 387 obj->interp = (const char *)(uintptr_t)vaddr; 388 break; 389 390 case PT_LOAD: 391 assert(nsegs < 2); 392 if (nsegs == 0) { /* First load segment */ 393 obj->vaddrbase = round_down(vaddr); 394 obj->mapbase = (caddr_t)(uintptr_t)obj->vaddrbase; 395 obj->textsize = round_up(vaddr + ph->p_memsz) - 396 obj->vaddrbase; 397 } else { /* Last load segment */ 398 obj->mapsize = round_up(vaddr + ph->p_memsz) - 399 obj->vaddrbase; 400 } 401 ++nsegs; 402 break; 403 404 case PT_DYNAMIC: 405 obj->dynamic = (Elf_Dyn *)(uintptr_t)vaddr; 406 dbg(("headers: PT_DYNAMIC %p phsize %zu", 407 obj->dynamic, (size_t)ph->p_memsz)); 408 break; 409 410 #if defined(__HAVE_TLS_VARIANT_I) || defined(__HAVE_TLS_VARIANT_II) 411 case PT_TLS: 412 obj->tlsindex = 1; 413 obj->tlssize = ph->p_memsz; 414 obj->tlsalign = ph->p_align; 415 obj->tlsinitsize = ph->p_filesz; 416 obj->tlsinit = (void *)(uintptr_t)ph->p_vaddr; 417 break; 418 #endif 419 #ifdef __ARM_EABI__ 420 case PT_ARM_EXIDX: 421 obj->exidx_start = (void *)(uintptr_t)vaddr; 422 obj->exidx_sz = ph->p_memsz; 423 break; 424 #endif 425 } 426 } 427 assert(nsegs == 2); 428 429 obj->entry = entry; 430 return obj; 431 } 432
Indexes created Tue Oct 21 12:09:54 GMT 2025