1 /*- 2 * SPDX-License-Identifier: BSD-2-Clause 3 * 4 * Copyright 1996-1998 John D. Polstra. 5 * All rights reserved. 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 1. Redistributions of source code must retain the above copyright 11 * notice, this list of conditions and the following disclaimer. 12 * 2. Redistributions in binary form must reproduce the above copyright 13 * notice, this list of conditions and the following disclaimer in the 14 * documentation and/or other materials provided with the distribution. 15 * 16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 17 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 18 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 19 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 20 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 21 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 22 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 23 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 24 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 25 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 26 */ 27 28 #include <sys/param.h> 29 #include <sys/mman.h> 30 #include <sys/stat.h> 31 32 #include <errno.h> 33 #include <stddef.h> 34 #include <stdlib.h> 35 #include <string.h> 36 #include <unistd.h> 37 38 #include "debug.h" 39 #include "rtld.h" 40 41 static Elf_Ehdr *get_elf_header(int, const char *, const struct stat *, 42 Elf_Phdr **phdr); 43 static int convert_flags(int); /* Elf flags -> mmap flags */ 44 45 static bool 46 phdr_in_zero_page(const Elf_Ehdr *hdr) 47 { 48 return (hdr->e_phoff + hdr->e_phnum * sizeof(Elf_Phdr) <= page_size); 49 } 50 51 /* 52 * Map a shared object into memory. The "fd" argument is a file descriptor, 53 * which must be open on the object and positioned at its beginning. 54 * The "path" argument is a pathname that is used only for error messages. 55 * 56 * The return value is a pointer to a newly-allocated Obj_Entry structure 57 * for the shared object. Returns NULL on failure. 58 */ 59 Obj_Entry * 60 map_object(int fd, const char *path, const struct stat *sb, bool ismain) 61 { 62 Obj_Entry *obj; 63 Elf_Ehdr *hdr; 64 int i; 65 Elf_Phdr *phdr; 66 Elf_Phdr *phlimit; 67 Elf_Phdr **segs; 68 int nsegs; 69 Elf_Phdr *phdyn; 70 Elf_Phdr *phinterp; 71 Elf_Phdr *phtls; 72 caddr_t mapbase; 73 size_t mapsize; 74 Elf_Addr base_vaddr; 75 Elf_Addr base_vlimit; 76 caddr_t base_addr; 77 int base_flags; 78 Elf_Off data_offset; 79 Elf_Addr data_vaddr; 80 Elf_Addr data_vlimit; 81 caddr_t data_addr; 82 int data_prot; 83 int data_flags; 84 Elf_Addr clear_vaddr; 85 caddr_t clear_addr; 86 caddr_t clear_page; 87 Elf_Addr phdr_vaddr; 88 size_t nclear, phsize; 89 Elf_Addr bss_vaddr; 90 Elf_Addr bss_vlimit; 91 caddr_t bss_addr; 92 Elf_Word stack_flags; 93 Elf_Addr note_start; 94 Elf_Addr note_end; 95 char *note_map; 96 size_t note_map_len; 97 98 hdr = get_elf_header(fd, path, sb, &phdr); 99 if (hdr == NULL) 100 return (NULL); 101 102 /* 103 * Scan the program header entries, and save key information. 104 * We expect that the loadable segments are ordered by load address. 105 */ 106 phsize = hdr->e_phnum * sizeof(phdr[0]); 107 phlimit = phdr + hdr->e_phnum; 108 nsegs = -1; 109 phdyn = phinterp = phtls = NULL; 110 phdr_vaddr = 0; 111 note_start = 0; 112 note_end = 0; 113 note_map = NULL; 114 note_map_len = 0; 115 segs = xcalloc(hdr->e_phnum, sizeof(segs[0])); 116 stack_flags = PF_X | PF_R | PF_W; 117 while (phdr < phlimit) { 118 switch (phdr->p_type) { 119 case PT_INTERP: 120 phinterp = phdr; 121 break; 122 123 case PT_LOAD: 124 if (phdr->p_memsz < phdr->p_filesz) { 125 _rtld_error("%s: invalid PT_LOAD segment", 126 path); 127 goto error; 128 } 129 130 segs[++nsegs] = phdr; 131 if ((segs[nsegs]->p_align & (page_size - 1)) != 0) { 132 _rtld_error( 133 "%s: PT_LOAD segment %d not page-aligned", 134 path, nsegs); 135 goto error; 136 } 137 break; 138 139 case PT_PHDR: 140 phdr_vaddr = phdr->p_vaddr; 141 phsize = phdr->p_memsz; 142 break; 143 144 case PT_DYNAMIC: 145 phdyn = phdr; 146 break; 147 148 case PT_TLS: 149 if (phdr->p_memsz < phdr->p_filesz) { 150 _rtld_error("%s: invalid PT_TLS segment", 151 path); 152 goto error; 153 } 154 155 phtls = phdr; 156 break; 157 158 case PT_GNU_STACK: 159 stack_flags = phdr->p_flags; 160 break; 161 162 case PT_NOTE: 163 if (phdr->p_offset > page_size || 164 phdr->p_offset + phdr->p_filesz > page_size) { 165 note_map_len = rtld_round_page(phdr->p_offset + 166 phdr->p_filesz) - 167 rtld_trunc_page(phdr->p_offset); 168 note_map = mmap(NULL, note_map_len, PROT_READ, 169 MAP_PRIVATE, fd, 170 rtld_trunc_page(phdr->p_offset)); 171 if (note_map == MAP_FAILED) { 172 _rtld_error( 173 "%s: error mapping PT_NOTE (%d)", 174 path, errno); 175 goto error; 176 } 177 note_start = (Elf_Addr)(note_map + 178 phdr->p_offset - 179 rtld_trunc_page(phdr->p_offset)); 180 } else { 181 note_start = (Elf_Addr)(char *)hdr + 182 phdr->p_offset; 183 } 184 note_end = note_start + phdr->p_filesz; 185 break; 186 } 187 188 ++phdr; 189 } 190 if (phdyn == NULL) { 191 _rtld_error("%s: object is not dynamically-linked", path); 192 goto error; 193 } 194 195 if (nsegs < 0) { 196 _rtld_error("%s: too few PT_LOAD segments", path); 197 goto error; 198 } 199 200 /* 201 * Map the entire address space of the object, to stake out our 202 * contiguous region, and to establish the base address for relocation. 203 */ 204 base_vaddr = rtld_trunc_page(segs[0]->p_vaddr); 205 base_vlimit = rtld_round_page(segs[nsegs]->p_vaddr + 206 segs[nsegs]->p_memsz); 207 mapsize = base_vlimit - base_vaddr; 208 base_addr = (caddr_t)base_vaddr; 209 base_flags = MAP_GUARD; 210 if (npagesizes > 1 && rtld_round_page(segs[0]->p_filesz) >= 211 pagesizes[1]) 212 base_flags |= MAP_ALIGNED_SUPER; 213 if (base_vaddr != 0) 214 base_flags |= MAP_FIXED | MAP_EXCL; 215 216 mapbase = mmap(base_addr, mapsize, PROT_NONE, base_flags, -1, 0); 217 if (mapbase == MAP_FAILED) { 218 _rtld_error("%s: mmap of entire address space failed: %s", 219 path, rtld_strerror(errno)); 220 goto error; 221 } 222 if (base_addr != NULL && mapbase != base_addr) { 223 _rtld_error( 224 "%s: mmap returned wrong address: wanted %p, got %p", 225 path, base_addr, mapbase); 226 goto error1; 227 } 228 229 for (i = 0; i <= nsegs; i++) { 230 /* Overlay the segment onto the proper region. */ 231 data_offset = rtld_trunc_page(segs[i]->p_offset); 232 data_vaddr = rtld_trunc_page(segs[i]->p_vaddr); 233 data_vlimit = rtld_round_page(segs[i]->p_vaddr + 234 segs[i]->p_filesz); 235 data_addr = mapbase + (data_vaddr - base_vaddr); 236 data_prot = convert_prot(segs[i]->p_flags); 237 data_flags = convert_flags(segs[i]->p_flags) | MAP_FIXED; 238 if (data_vlimit != data_vaddr && mmap(data_addr, 239 data_vlimit - data_vaddr, data_prot, data_flags | 240 MAP_PREFAULT_READ, fd, data_offset) == MAP_FAILED) { 241 _rtld_error("%s: mmap of data failed: %s", 242 path, rtld_strerror(errno)); 243 goto error1; 244 } 245 246 /* Do BSS setup */ 247 if (segs[i]->p_filesz != segs[i]->p_memsz) { 248 /* Clear any BSS in the last page of the segment. */ 249 clear_vaddr = segs[i]->p_vaddr + segs[i]->p_filesz; 250 clear_addr = mapbase + (clear_vaddr - base_vaddr); 251 clear_page = mapbase + (rtld_trunc_page(clear_vaddr) - 252 base_vaddr); 253 254 if ((nclear = data_vlimit - clear_vaddr) > 0) { 255 /* 256 * Make sure the end of the segment is 257 * writable. 258 */ 259 if ((data_prot & PROT_WRITE) == 0 && 260 mprotect(clear_page, page_size, 261 data_prot | PROT_WRITE) == -1) { 262 _rtld_error("%s: mprotect failed: %s", 263 path, rtld_strerror(errno)); 264 goto error1; 265 } 266 267 memset(clear_addr, 0, nclear); 268 269 /* Reset the data protection back */ 270 if ((data_prot & PROT_WRITE) == 0) 271 mprotect(clear_page, page_size, 272 data_prot); 273 } 274 275 /* Overlay the BSS segment onto the proper region. */ 276 bss_vaddr = data_vlimit; 277 bss_vlimit = rtld_round_page(segs[i]->p_vaddr + 278 segs[i]->p_memsz); 279 bss_addr = mapbase + (bss_vaddr - base_vaddr); 280 if (bss_vlimit > bss_vaddr) { 281 /* There is something to do */ 282 if (mmap(bss_addr, bss_vlimit - bss_vaddr, 283 data_prot, data_flags | MAP_ANON, -1, 284 0) == MAP_FAILED) { 285 _rtld_error( 286 "%s: mmap of bss failed: %s", 287 path, rtld_strerror(errno)); 288 goto error1; 289 } 290 } 291 } 292 293 if (phdr_vaddr == 0 && data_offset <= hdr->e_phoff && 294 data_vlimit - data_vaddr + data_offset >= 295 hdr->e_phoff + hdr->e_phnum * sizeof(Elf_Phdr)) { 296 phdr_vaddr = data_vaddr + hdr->e_phoff - data_offset; 297 } 298 } 299 300 obj = obj_new(); 301 if (sb != NULL) { 302 obj->dev = sb->st_dev; 303 obj->ino = sb->st_ino; 304 } 305 obj->mapbase = mapbase; 306 obj->mapsize = mapsize; 307 obj->vaddrbase = base_vaddr; 308 obj->relocbase = mapbase - base_vaddr; 309 obj->dynamic = (const Elf_Dyn *)(obj->relocbase + phdyn->p_vaddr); 310 if (hdr->e_entry != 0) 311 obj->entry = (caddr_t)(obj->relocbase + hdr->e_entry); 312 if (phdr_vaddr != 0) { 313 obj->phdr = (const Elf_Phdr *)(obj->relocbase + phdr_vaddr); 314 } else { 315 obj->phdr = malloc(phsize); 316 if (obj->phdr == NULL) { 317 obj_free(obj); 318 _rtld_error("%s: cannot allocate program header", 319 path); 320 goto error1; 321 } 322 memcpy(__DECONST(char *, obj->phdr), (char *)hdr + hdr->e_phoff, 323 phsize); 324 obj->phdr_alloc = true; 325 } 326 obj->phnum = phsize / sizeof(*phdr); 327 if (phinterp != NULL) 328 obj->interp = (const char *)(obj->relocbase + 329 phinterp->p_vaddr); 330 if (phtls != NULL) { 331 if (ismain) 332 obj->tlsindex = 1; 333 else { 334 tls_dtv_generation++; 335 obj->tlsindex = ++tls_max_index; 336 } 337 obj->tlssize = phtls->p_memsz; 338 obj->tlsalign = phtls->p_align; 339 obj->tlspoffset = phtls->p_offset; 340 obj->tlsinitsize = phtls->p_filesz; 341 obj->tlsinit = obj->relocbase + phtls->p_vaddr; 342 } 343 obj->stack_flags = stack_flags; 344 if (note_start < note_end) 345 digest_notes(obj, note_start, note_end); 346 finish: 347 if (note_map != NULL && note_map != MAP_FAILED) 348 munmap(note_map, note_map_len); 349 munmap(hdr, page_size); 350 free(segs); 351 return (obj); 352 353 error1: 354 munmap(mapbase, mapsize); 355 error: 356 if (!phdr_in_zero_page(hdr)) 357 munmap(phdr, hdr->e_phnum * sizeof(phdr[0])); 358 obj = NULL; 359 goto finish; 360 } 361 362 bool 363 check_elf_headers(const Elf_Ehdr *hdr, const char *path) 364 { 365 if (!IS_ELF(*hdr)) { 366 _rtld_error("%s: invalid file format", path); 367 return (false); 368 } 369 if (hdr->e_ident[EI_CLASS] != ELF_TARG_CLASS || 370 hdr->e_ident[EI_DATA] != ELF_TARG_DATA) { 371 _rtld_error("%s: unsupported file layout", path); 372 return (false); 373 } 374 if (hdr->e_ident[EI_VERSION] != EV_CURRENT || 375 hdr->e_version != EV_CURRENT) { 376 _rtld_error("%s: unsupported file version", path); 377 return (false); 378 } 379 if (hdr->e_type != ET_EXEC && hdr->e_type != ET_DYN) { 380 _rtld_error("%s: unsupported file type", path); 381 return (false); 382 } 383 if (hdr->e_machine != ELF_TARG_MACH) { 384 _rtld_error("%s: unsupported machine", path); 385 return (false); 386 } 387 if (hdr->e_phentsize != sizeof(Elf_Phdr)) { 388 _rtld_error( 389 "%s: invalid shared object: e_phentsize != sizeof(Elf_Phdr)", 390 path); 391 return (false); 392 } 393 return (true); 394 } 395 396 static Elf_Ehdr * 397 get_elf_header(int fd, const char *path, const struct stat *sbp, 398 Elf_Phdr **phdr_p) 399 { 400 Elf_Ehdr *hdr; 401 Elf_Phdr *phdr; 402 403 /* Make sure file has enough data for the ELF header */ 404 if (sbp != NULL && sbp->st_size < (off_t)sizeof(Elf_Ehdr)) { 405 _rtld_error("%s: invalid file format", path); 406 return (NULL); 407 } 408 409 hdr = mmap(NULL, page_size, PROT_READ, MAP_PRIVATE | MAP_PREFAULT_READ, 410 fd, 0); 411 if (hdr == MAP_FAILED) { 412 _rtld_error("%s: read error: %s", path, rtld_strerror(errno)); 413 return (NULL); 414 } 415 416 /* Make sure the file is valid */ 417 if (!check_elf_headers(hdr, path)) 418 goto error; 419 420 /* 421 * We rely on the program header being in the first page. This is 422 * not strictly required by the ABI specification, but it seems to 423 * always true in practice. And, it simplifies things considerably. 424 */ 425 if (phdr_in_zero_page(hdr)) { 426 phdr = (Elf_Phdr *)((char *)hdr + hdr->e_phoff); 427 } else { 428 phdr = mmap(NULL, hdr->e_phnum * sizeof(phdr[0]), PROT_READ, 429 MAP_PRIVATE | MAP_PREFAULT_READ, fd, hdr->e_phoff); 430 if (phdr == MAP_FAILED) { 431 _rtld_error("%s: error mapping phdr: %s", path, 432 rtld_strerror(errno)); 433 goto error; 434 } 435 } 436 *phdr_p = phdr; 437 return (hdr); 438 439 error: 440 munmap(hdr, page_size); 441 return (NULL); 442 } 443 444 void 445 obj_free(Obj_Entry *obj) 446 { 447 Objlist_Entry *elm; 448 449 if (obj->tls_static) 450 free_tls_offset(obj); 451 while (obj->needed != NULL) { 452 Needed_Entry *needed = obj->needed; 453 454 obj->needed = needed->next; 455 free(needed); 456 } 457 while (!STAILQ_EMPTY(&obj->names)) { 458 Name_Entry *entry = STAILQ_FIRST(&obj->names); 459 460 STAILQ_REMOVE_HEAD(&obj->names, link); 461 free(entry); 462 } 463 while (!STAILQ_EMPTY(&obj->dldags)) { 464 elm = STAILQ_FIRST(&obj->dldags); 465 STAILQ_REMOVE_HEAD(&obj->dldags, link); 466 free(elm); 467 } 468 while (!STAILQ_EMPTY(&obj->dagmembers)) { 469 elm = STAILQ_FIRST(&obj->dagmembers); 470 STAILQ_REMOVE_HEAD(&obj->dagmembers, link); 471 free(elm); 472 } 473 if (obj->vertab) 474 free(obj->vertab); 475 if (obj->origin_path) 476 free(obj->origin_path); 477 if (obj->z_origin) 478 free(__DECONST(void *, obj->rpath)); 479 if (obj->priv) 480 free(obj->priv); 481 if (obj->path) 482 free(obj->path); 483 if (obj->phdr_alloc) 484 free(__DECONST(void *, obj->phdr)); 485 free(obj); 486 } 487 488 Obj_Entry * 489 obj_new(void) 490 { 491 Obj_Entry *obj; 492 493 obj = CNEW(Obj_Entry); 494 STAILQ_INIT(&obj->dldags); 495 STAILQ_INIT(&obj->dagmembers); 496 STAILQ_INIT(&obj->names); 497 return (obj); 498 } 499 500 /* 501 * Given a set of ELF protection flags, return the corresponding protection 502 * flags for MMAP. 503 */ 504 int 505 convert_prot(int elfflags) 506 { 507 int prot = 0; 508 509 if ((elfflags & PF_R) != 0) 510 prot |= PROT_READ; 511 if ((elfflags & PF_W) != 0) 512 prot |= PROT_WRITE; 513 if ((elfflags & PF_X) != 0) 514 prot |= PROT_EXEC; 515 return (prot); 516 } 517 518 static int 519 convert_flags(int elfflags) 520 { 521 int flags = MAP_PRIVATE; /* All mappings are private */ 522 523 /* 524 * Readonly mappings are marked "MAP_NOCORE", because they can be 525 * reconstructed by a debugger. 526 */ 527 if ((elfflags & PF_W) == 0) 528 flags |= MAP_NOCORE; 529 return (flags); 530 } 531