headers.c revision 1.63.2.1
1 /* $NetBSD: headers.c,v 1.63.2.1 2019/06/10 22:05:29 christos 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 1.63.2.1 2019/06/10 22:05:29 christos 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 #ifdef RTLD_LOADER 78 Elf_Addr init = 0, fini = 0; 79 #endif 80 81 dbg(("headers: digesting PT_DYNAMIC at %p", obj->dynamic)); 82 for (dynp = obj->dynamic; dynp->d_tag != DT_NULL; ++dynp) { 83 dbg((" d_tag %ld at %p", (long)dynp->d_tag, dynp)); 84 switch (dynp->d_tag) { 85 86 case DT_REL: 87 obj->rel = (const Elf_Rel *) 88 (obj->relocbase + dynp->d_un.d_ptr); 89 break; 90 91 case DT_RELSZ: 92 relsz = dynp->d_un.d_val; 93 break; 94 95 case DT_RELENT: 96 assert(dynp->d_un.d_val == sizeof(Elf_Rel)); 97 break; 98 99 case DT_JMPREL: 100 pltrel = dynp->d_un.d_ptr; 101 break; 102 103 case DT_PLTRELSZ: 104 pltrelsz = dynp->d_un.d_val; 105 break; 106 107 case DT_RELA: 108 obj->rela = (const Elf_Rela *) 109 (obj->relocbase + dynp->d_un.d_ptr); 110 break; 111 112 case DT_RELASZ: 113 relasz = dynp->d_un.d_val; 114 break; 115 116 case DT_RELAENT: 117 assert(dynp->d_un.d_val == sizeof(Elf_Rela)); 118 break; 119 120 case DT_PLTREL: 121 use_pltrel = dynp->d_un.d_val == DT_REL; 122 use_pltrela = dynp->d_un.d_val == DT_RELA; 123 assert(use_pltrel || use_pltrela); 124 break; 125 126 case DT_SYMTAB: 127 obj->symtab = (const Elf_Sym *) 128 (obj->relocbase + dynp->d_un.d_ptr); 129 break; 130 131 case DT_SYMENT: 132 assert(dynp->d_un.d_val == sizeof(Elf_Sym)); 133 break; 134 135 case DT_STRTAB: 136 obj->strtab = (const char *) 137 (obj->relocbase + dynp->d_un.d_ptr); 138 break; 139 140 case DT_STRSZ: 141 obj->strsize = dynp->d_un.d_val; 142 break; 143 144 case DT_VERNEED: 145 obj->verneed = (const Elf_Verneed *) 146 (obj->relocbase + dynp->d_un.d_ptr); 147 break; 148 149 case DT_VERNEEDNUM: 150 obj->verneednum = dynp->d_un.d_val; 151 break; 152 153 case DT_VERDEF: 154 obj->verdef = (const Elf_Verdef *) 155 (obj->relocbase + dynp->d_un.d_ptr); 156 break; 157 158 case DT_VERDEFNUM: 159 obj->verdefnum = dynp->d_un.d_val; 160 break; 161 162 case DT_VERSYM: 163 obj->versyms = (const Elf_Versym *) 164 (obj->relocbase + dynp->d_un.d_ptr); 165 break; 166 167 case DT_HASH: 168 { 169 const Elf_Symindx *hashtab = (const Elf_Symindx *) 170 (obj->relocbase + dynp->d_un.d_ptr); 171 172 if (hashtab[0] > UINT32_MAX) 173 obj->nbuckets = UINT32_MAX; 174 else 175 obj->nbuckets = hashtab[0]; 176 obj->nchains = hashtab[1]; 177 obj->buckets = hashtab + 2; 178 obj->chains = obj->buckets + obj->nbuckets; 179 /* 180 * Should really be in _rtld_relocate_objects, 181 * but _rtld_symlook_obj might be used before. 182 */ 183 if (obj->nbuckets) { 184 fast_divide32_prepare(obj->nbuckets, 185 &obj->nbuckets_m, 186 &obj->nbuckets_s1, 187 &obj->nbuckets_s2); 188 } 189 } 190 break; 191 192 case DT_NEEDED: 193 { 194 Needed_Entry *nep = NEW(Needed_Entry); 195 196 nep->name = dynp->d_un.d_val; 197 nep->obj = NULL; 198 nep->next = NULL; 199 200 *needed_tail = nep; 201 needed_tail = &nep->next; 202 } 203 break; 204 205 case DT_PLTGOT: 206 obj->pltgot = (Elf_Addr *) 207 (obj->relocbase + dynp->d_un.d_ptr); 208 break; 209 210 case DT_TEXTREL: 211 obj->textrel = true; 212 break; 213 214 case DT_SYMBOLIC: 215 obj->symbolic = true; 216 break; 217 218 case DT_RPATH: 219 case DT_RUNPATH: 220 /* 221 * We have to wait until later to process this, because 222 * we might not have gotten the address of the string 223 * table yet. 224 */ 225 dyn_rpath = dynp; 226 break; 227 228 case DT_SONAME: 229 dyn_soname = dynp; 230 break; 231 232 case DT_INIT: 233 #ifdef RTLD_LOADER 234 init = dynp->d_un.d_ptr; 235 #endif 236 break; 237 238 #ifdef HAVE_INITFINI_ARRAY 239 case DT_INIT_ARRAY: 240 obj->init_array = 241 (Elf_Addr *)(obj->relocbase + dynp->d_un.d_ptr); 242 dbg(("headers: DT_INIT_ARRAY at %p", 243 obj->init_array)); 244 break; 245 246 case DT_INIT_ARRAYSZ: 247 obj->init_arraysz = dynp->d_un.d_val / sizeof(fptr_t); 248 dbg(("headers: DT_INIT_ARRAYZ %zu", 249 obj->init_arraysz)); 250 break; 251 #endif 252 253 case DT_FINI: 254 #ifdef RTLD_LOADER 255 fini = dynp->d_un.d_ptr; 256 #endif 257 break; 258 259 #ifdef HAVE_INITFINI_ARRAY 260 case DT_FINI_ARRAY: 261 obj->fini_array = 262 (Elf_Addr *)(obj->relocbase + dynp->d_un.d_ptr); 263 dbg(("headers: DT_FINI_ARRAY at %p", 264 obj->fini_array)); 265 break; 266 267 case DT_FINI_ARRAYSZ: 268 obj->fini_arraysz = dynp->d_un.d_val / sizeof(fptr_t); 269 dbg(("headers: DT_FINI_ARRAYZ %zu", 270 obj->fini_arraysz)); 271 break; 272 #endif 273 274 /* 275 * Don't process DT_DEBUG on MIPS as the dynamic section 276 * is mapped read-only. DT_MIPS_RLD_MAP is used instead. 277 * XXX: n32/n64 may use DT_DEBUG, not sure yet. 278 */ 279 #ifndef __mips__ 280 case DT_DEBUG: 281 #ifdef RTLD_LOADER 282 dynp->d_un.d_ptr = (Elf_Addr)&_rtld_debug; 283 #endif 284 break; 285 #endif 286 287 #ifdef __mips__ 288 case DT_MIPS_LOCAL_GOTNO: 289 obj->local_gotno = dynp->d_un.d_val; 290 break; 291 292 case DT_MIPS_SYMTABNO: 293 obj->symtabno = dynp->d_un.d_val; 294 break; 295 296 case DT_MIPS_GOTSYM: 297 obj->gotsym = dynp->d_un.d_val; 298 break; 299 300 case DT_MIPS_RLD_MAP: 301 #ifdef RTLD_LOADER 302 *((Elf_Addr *)(dynp->d_un.d_ptr)) = (Elf_Addr) 303 &_rtld_debug; 304 #endif 305 break; 306 #endif 307 #ifdef __powerpc__ 308 #ifdef _LP64 309 case DT_PPC64_GLINK: 310 obj->glink = (Elf_Addr)(uintptr_t)obj->relocbase + dynp->d_un.d_ptr; 311 break; 312 #else 313 case DT_PPC_GOT: 314 obj->gotptr = (Elf_Addr *)(obj->relocbase + dynp->d_un.d_ptr); 315 break; 316 #endif 317 #endif 318 case DT_FLAGS_1: 319 obj->z_now = 320 ((dynp->d_un.d_val & DF_1_NOW) != 0); 321 obj->z_nodelete = 322 ((dynp->d_un.d_val & DF_1_NODELETE) != 0); 323 obj->z_initfirst = 324 ((dynp->d_un.d_val & DF_1_INITFIRST) != 0); 325 obj->z_noopen = 326 ((dynp->d_un.d_val & DF_1_NOOPEN) != 0); 327 break; 328 } 329 } 330 331 obj->rellim = (const Elf_Rel *)((const uint8_t *)obj->rel + relsz); 332 obj->relalim = (const Elf_Rela *)((const uint8_t *)obj->rela + relasz); 333 if (use_pltrel) { 334 obj->pltrel = (const Elf_Rel *)(obj->relocbase + pltrel); 335 obj->pltrellim = (const Elf_Rel *)(obj->relocbase + pltrel + pltrelsz); 336 obj->pltrelalim = 0; 337 /* On PPC and SPARC, at least, REL(A)SZ may include JMPREL. 338 Trim rel(a)lim to save time later. */ 339 if (obj->rellim && obj->pltrel && 340 obj->rellim > obj->pltrel && 341 obj->rellim <= obj->pltrellim) 342 obj->rellim = obj->pltrel; 343 } else if (use_pltrela) { 344 obj->pltrela = (const Elf_Rela *)(obj->relocbase + pltrel); 345 obj->pltrellim = 0; 346 obj->pltrelalim = (const Elf_Rela *)(obj->relocbase + pltrel + pltrelsz); 347 /* On PPC and SPARC, at least, REL(A)SZ may include JMPREL. 348 Trim rel(a)lim to save time later. */ 349 if (obj->relalim && obj->pltrela && 350 obj->relalim > obj->pltrela && 351 obj->relalim <= obj->pltrelalim) 352 obj->relalim = obj->pltrela; 353 } 354 355 #ifdef RTLD_LOADER 356 if (init != 0) 357 obj->init = (Elf_Addr) obj->relocbase + init; 358 if (fini != 0) 359 obj->fini = (Elf_Addr) obj->relocbase + fini; 360 #endif 361 362 if (dyn_rpath != NULL) { 363 _rtld_add_paths(execname, &obj->rpaths, obj->strtab + 364 dyn_rpath->d_un.d_val); 365 } 366 if (dyn_soname != NULL) { 367 _rtld_object_add_name(obj, obj->strtab + 368 dyn_soname->d_un.d_val); 369 } 370 } 371 372 /* 373 * Process a shared object's program header. This is used only for the 374 * main program, when the kernel has already loaded the main program 375 * into memory before calling the dynamic linker. It creates and 376 * returns an Obj_Entry structure. 377 */ 378 Obj_Entry * 379 _rtld_digest_phdr(const Elf_Phdr *phdr, int phnum, caddr_t entry) 380 { 381 Obj_Entry *obj; 382 const Elf_Phdr *phlimit = phdr + phnum; 383 const Elf_Phdr *ph; 384 bool first_seg = true; 385 Elf_Addr vaddr; 386 size_t size; 387 388 obj = _rtld_obj_new(); 389 390 for (ph = phdr; ph < phlimit; ++ph) { 391 if (ph->p_type != PT_PHDR) 392 continue; 393 394 obj->relocbase = (caddr_t)((uintptr_t)phdr - (uintptr_t)ph->p_vaddr); 395 obj->phdr = phdr; /* Equivalent to relocbase + p_vaddr. */ 396 obj->phsize = ph->p_memsz; 397 dbg(("headers: phdr %p (%p) phsize %zu relocbase %p", 398 obj->phdr, phdr, obj->phsize, obj->relocbase)); 399 break; 400 } 401 402 for (ph = phdr; ph < phlimit; ++ph) { 403 vaddr = (Elf_Addr)(uintptr_t)(obj->relocbase + ph->p_vaddr); 404 switch (ph->p_type) { 405 406 case PT_INTERP: 407 obj->interp = (const char *)(uintptr_t)vaddr; 408 dbg(("headers: %s %p phsize %" PRImemsz, 409 "PT_INTERP", (void *)(uintptr_t)vaddr, 410 ph->p_memsz)); 411 break; 412 413 case PT_LOAD: 414 size = round_up(vaddr + ph->p_memsz) - obj->vaddrbase; 415 if (first_seg) { /* First load segment */ 416 obj->vaddrbase = round_down(vaddr); 417 obj->mapbase = (caddr_t)(uintptr_t)obj->vaddrbase; 418 obj->textsize = size; 419 obj->mapsize = size; 420 first_seg = false; 421 } else { /* Last load segment */ 422 obj->mapsize = MAX(obj->mapsize, size); 423 } 424 dbg(("headers: %s %p phsize %" PRImemsz, 425 "PT_LOAD", (void *)(uintptr_t)vaddr, 426 ph->p_memsz)); 427 break; 428 429 case PT_DYNAMIC: 430 obj->dynamic = (Elf_Dyn *)(uintptr_t)vaddr; 431 dbg(("headers: %s %p phsize %" PRImemsz, 432 "PT_DYNAMIC", (void *)(uintptr_t)vaddr, 433 ph->p_memsz)); 434 break; 435 436 #ifdef GNU_RELRO 437 case PT_GNU_RELRO: 438 obj->relro_page = obj->relocbase 439 + round_down(ph->p_vaddr); 440 obj->relro_size = round_up(ph->p_memsz); 441 dbg(("headers: %s %p phsize %" PRImemsz, 442 "PT_GNU_RELRO", (void *)(uintptr_t)vaddr, 443 ph->p_memsz)); 444 break; 445 #endif 446 447 #if defined(__HAVE_TLS_VARIANT_I) || defined(__HAVE_TLS_VARIANT_II) 448 case PT_TLS: 449 obj->tlsindex = 1; 450 obj->tlssize = ph->p_memsz; 451 obj->tlsalign = ph->p_align; 452 obj->tlsinitsize = ph->p_filesz; 453 obj->tlsinit = (void *)(obj->relocbase + 454 (uintptr_t)ph->p_vaddr); 455 dbg(("headers: %s %p phsize %" PRImemsz, 456 "PT_TLS", (void *)(uintptr_t)vaddr, 457 ph->p_memsz)); 458 break; 459 #endif 460 #ifdef __ARM_EABI__ 461 case PT_ARM_EXIDX: 462 obj->exidx_start = (void *)(uintptr_t)vaddr; 463 obj->exidx_sz = ph->p_memsz; 464 dbg(("headers: %s %p phsize %" PRImemsz, 465 "PT_ARM_EXIDX", (void *)(uintptr_t)vaddr, 466 ph->p_memsz)); 467 break; 468 #endif 469 } 470 } 471 472 obj->entry = entry; 473 return obj; 474 } 475
Indexes created Wed Oct 15 16:09:53 GMT 2025