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 Elf_Addr text_end; 98 99 hdr = get_elf_header(fd, path, sb, &phdr); 100 if (hdr == NULL) 101 return (NULL); 102 103 /* 104 * Scan the program header entries, and save key information. 105 * We expect that the loadable segments are ordered by load address. 106 */ 107 phsize = hdr->e_phnum * sizeof(phdr[0]); 108 phlimit = phdr + hdr->e_phnum; 109 nsegs = -1; 110 phdyn = phinterp = phtls = NULL; 111 phdr_vaddr = 0; 112 note_start = 0; 113 note_end = 0; 114 note_map = NULL; 115 note_map_len = 0; 116 segs = alloca(sizeof(segs[0]) * hdr->e_phnum); 117 stack_flags = PF_X | PF_R | PF_W; 118 text_end = 0; 119 while (phdr < phlimit) { 120 switch (phdr->p_type) { 121 case PT_INTERP: 122 phinterp = phdr; 123 break; 124 125 case PT_LOAD: 126 segs[++nsegs] = phdr; 127 if ((segs[nsegs]->p_align & (page_size - 1)) != 0) { 128 _rtld_error( 129 "%s: PT_LOAD segment %d not page-aligned", 130 path, nsegs); 131 goto error; 132 } 133 if ((segs[nsegs]->p_flags & PF_X) == PF_X) { 134 text_end = MAX(text_end, 135 rtld_round_page(segs[nsegs]->p_vaddr + 136 segs[nsegs]->p_memsz)); 137 } 138 break; 139 140 case PT_PHDR: 141 phdr_vaddr = phdr->p_vaddr; 142 phsize = phdr->p_memsz; 143 break; 144 145 case PT_DYNAMIC: 146 phdyn = phdr; 147 break; 148 149 case PT_TLS: 150 phtls = phdr; 151 break; 152 153 case PT_GNU_STACK: 154 stack_flags = phdr->p_flags; 155 break; 156 157 case PT_NOTE: 158 if (phdr->p_offset > page_size || 159 phdr->p_offset + phdr->p_filesz > page_size) { 160 note_map_len = rtld_round_page(phdr->p_offset + 161 phdr->p_filesz) - 162 rtld_trunc_page(phdr->p_offset); 163 note_map = mmap(NULL, note_map_len, PROT_READ, 164 MAP_PRIVATE, fd, 165 rtld_trunc_page(phdr->p_offset)); 166 if (note_map == MAP_FAILED) { 167 _rtld_error( 168 "%s: error mapping PT_NOTE (%d)", 169 path, errno); 170 goto error; 171 } 172 note_start = (Elf_Addr)(note_map + 173 phdr->p_offset - 174 rtld_trunc_page(phdr->p_offset)); 175 } else { 176 note_start = (Elf_Addr)(char *)hdr + 177 phdr->p_offset; 178 } 179 note_end = note_start + phdr->p_filesz; 180 break; 181 } 182 183 ++phdr; 184 } 185 if (phdyn == NULL) { 186 _rtld_error("%s: object is not dynamically-linked", path); 187 goto error; 188 } 189 190 if (nsegs < 0) { 191 _rtld_error("%s: too few PT_LOAD segments", path); 192 goto error; 193 } 194 195 /* 196 * Map the entire address space of the object, to stake out our 197 * contiguous region, and to establish the base address for relocation. 198 */ 199 base_vaddr = rtld_trunc_page(segs[0]->p_vaddr); 200 base_vlimit = rtld_round_page(segs[nsegs]->p_vaddr + 201 segs[nsegs]->p_memsz); 202 mapsize = base_vlimit - base_vaddr; 203 base_addr = (caddr_t)base_vaddr; 204 base_flags = MAP_GUARD; 205 if (npagesizes > 1 && rtld_round_page(segs[0]->p_filesz) >= 206 pagesizes[1]) 207 base_flags |= MAP_ALIGNED_SUPER; 208 if (base_vaddr != 0) 209 base_flags |= MAP_FIXED | MAP_EXCL; 210 211 mapbase = mmap(base_addr, mapsize, PROT_NONE, base_flags, -1, 0); 212 if (mapbase == MAP_FAILED) { 213 _rtld_error("%s: mmap of entire address space failed: %s", 214 path, rtld_strerror(errno)); 215 goto error; 216 } 217 if (base_addr != NULL && mapbase != base_addr) { 218 _rtld_error( 219 "%s: mmap returned wrong address: wanted %p, got %p", 220 path, base_addr, mapbase); 221 goto error1; 222 } 223 224 for (i = 0; i <= nsegs; i++) { 225 /* Overlay the segment onto the proper region. */ 226 data_offset = rtld_trunc_page(segs[i]->p_offset); 227 data_vaddr = rtld_trunc_page(segs[i]->p_vaddr); 228 data_vlimit = rtld_round_page(segs[i]->p_vaddr + 229 segs[i]->p_filesz); 230 data_addr = mapbase + (data_vaddr - base_vaddr); 231 data_prot = convert_prot(segs[i]->p_flags); 232 data_flags = convert_flags(segs[i]->p_flags) | MAP_FIXED; 233 if (data_vlimit != data_vaddr && mmap(data_addr, 234 data_vlimit - data_vaddr, data_prot, data_flags | 235 MAP_PREFAULT_READ, fd, data_offset) == MAP_FAILED) { 236 _rtld_error("%s: mmap of data failed: %s", 237 path, rtld_strerror(errno)); 238 goto error1; 239 } 240 241 /* Do BSS setup */ 242 if (segs[i]->p_filesz != segs[i]->p_memsz) { 243 /* Clear any BSS in the last page of the segment. */ 244 clear_vaddr = segs[i]->p_vaddr + segs[i]->p_filesz; 245 clear_addr = mapbase + (clear_vaddr - base_vaddr); 246 clear_page = mapbase + (rtld_trunc_page(clear_vaddr) - 247 base_vaddr); 248 249 if ((nclear = data_vlimit - clear_vaddr) > 0) { 250 /* 251 * Make sure the end of the segment is 252 * writable. 253 */ 254 if ((data_prot & PROT_WRITE) == 0 && 255 mprotect(clear_page, page_size, 256 data_prot | PROT_WRITE) == -1) { 257 _rtld_error("%s: mprotect failed: %s", 258 path, rtld_strerror(errno)); 259 goto error1; 260 } 261 262 memset(clear_addr, 0, nclear); 263 264 /* Reset the data protection back */ 265 if ((data_prot & PROT_WRITE) == 0) 266 mprotect(clear_page, page_size, 267 data_prot); 268 } 269 270 /* Overlay the BSS segment onto the proper region. */ 271 bss_vaddr = data_vlimit; 272 bss_vlimit = rtld_round_page(segs[i]->p_vaddr + 273 segs[i]->p_memsz); 274 bss_addr = mapbase + (bss_vaddr - base_vaddr); 275 if (bss_vlimit > bss_vaddr) { 276 /* There is something to do */ 277 if (mmap(bss_addr, bss_vlimit - bss_vaddr, 278 data_prot, data_flags | MAP_ANON, -1, 279 0) == MAP_FAILED) { 280 _rtld_error( 281 "%s: mmap of bss failed: %s", 282 path, rtld_strerror(errno)); 283 goto error1; 284 } 285 } 286 } 287 288 if (phdr_vaddr == 0 && data_offset <= hdr->e_phoff && 289 data_vlimit - data_vaddr + data_offset >= 290 hdr->e_phoff + hdr->e_phnum * sizeof(Elf_Phdr)) { 291 phdr_vaddr = data_vaddr + hdr->e_phoff - data_offset; 292 } 293 } 294 295 obj = obj_new(); 296 if (sb != NULL) { 297 obj->dev = sb->st_dev; 298 obj->ino = sb->st_ino; 299 } 300 obj->mapbase = mapbase; 301 obj->mapsize = mapsize; 302 obj->vaddrbase = base_vaddr; 303 obj->relocbase = mapbase - base_vaddr; 304 obj->dynamic = (const Elf_Dyn *)(obj->relocbase + phdyn->p_vaddr); 305 if (hdr->e_entry != 0) 306 obj->entry = (caddr_t)(obj->relocbase + hdr->e_entry); 307 if (phdr_vaddr != 0) { 308 obj->phdr = (const Elf_Phdr *)(obj->relocbase + phdr_vaddr); 309 } else { 310 obj->phdr = malloc(phsize); 311 if (obj->phdr == NULL) { 312 obj_free(obj); 313 _rtld_error("%s: cannot allocate program header", 314 path); 315 goto error1; 316 } 317 memcpy(__DECONST(char *, obj->phdr), (char *)hdr + hdr->e_phoff, 318 phsize); 319 obj->phdr_alloc = true; 320 } 321 obj->phsize = phsize; 322 if (phinterp != NULL) 323 obj->interp = (const char *)(obj->relocbase + 324 phinterp->p_vaddr); 325 if (phtls != NULL) { 326 if (ismain) 327 obj->tlsindex = 1; 328 else { 329 tls_dtv_generation++; 330 obj->tlsindex = ++tls_max_index; 331 } 332 obj->tlssize = phtls->p_memsz; 333 obj->tlsalign = phtls->p_align; 334 obj->tlspoffset = phtls->p_offset; 335 obj->tlsinitsize = phtls->p_filesz; 336 obj->tlsinit = obj->relocbase + phtls->p_vaddr; 337 } 338 obj->stack_flags = stack_flags; 339 if (note_start < note_end) 340 digest_notes(obj, note_start, note_end); 341 if (note_map != NULL) 342 munmap(note_map, note_map_len); 343 munmap(hdr, page_size); 344 return (obj); 345 346 error1: 347 munmap(mapbase, mapsize); 348 error: 349 if (note_map != NULL && note_map != MAP_FAILED) 350 munmap(note_map, note_map_len); 351 if (!phdr_in_zero_page(hdr)) 352 munmap(phdr, hdr->e_phnum * sizeof(phdr[0])); 353 munmap(hdr, page_size); 354 return (NULL); 355 } 356 357 bool 358 check_elf_headers(const Elf_Ehdr *hdr, const char *path) 359 { 360 if (!IS_ELF(*hdr)) { 361 _rtld_error("%s: invalid file format", path); 362 return (false); 363 } 364 if (hdr->e_ident[EI_CLASS] != ELF_TARG_CLASS || 365 hdr->e_ident[EI_DATA] != ELF_TARG_DATA) { 366 _rtld_error("%s: unsupported file layout", path); 367 return (false); 368 } 369 if (hdr->e_ident[EI_VERSION] != EV_CURRENT || 370 hdr->e_version != EV_CURRENT) { 371 _rtld_error("%s: unsupported file version", path); 372 return (false); 373 } 374 if (hdr->e_type != ET_EXEC && hdr->e_type != ET_DYN) { 375 _rtld_error("%s: unsupported file type", path); 376 return (false); 377 } 378 if (hdr->e_machine != ELF_TARG_MACH) { 379 _rtld_error("%s: unsupported machine", path); 380 return (false); 381 } 382 if (hdr->e_phentsize != sizeof(Elf_Phdr)) { 383 _rtld_error( 384 "%s: invalid shared object: e_phentsize != sizeof(Elf_Phdr)", 385 path); 386 return (false); 387 } 388 return (true); 389 } 390 391 static Elf_Ehdr * 392 get_elf_header(int fd, const char *path, const struct stat *sbp, 393 Elf_Phdr **phdr_p) 394 { 395 Elf_Ehdr *hdr; 396 Elf_Phdr *phdr; 397 398 /* Make sure file has enough data for the ELF header */ 399 if (sbp != NULL && sbp->st_size < (off_t)sizeof(Elf_Ehdr)) { 400 _rtld_error("%s: invalid file format", path); 401 return (NULL); 402 } 403 404 hdr = mmap(NULL, page_size, PROT_READ, MAP_PRIVATE | MAP_PREFAULT_READ, 405 fd, 0); 406 if (hdr == MAP_FAILED) { 407 _rtld_error("%s: read error: %s", path, rtld_strerror(errno)); 408 return (NULL); 409 } 410 411 /* Make sure the file is valid */ 412 if (!check_elf_headers(hdr, path)) 413 goto error; 414 415 /* 416 * We rely on the program header being in the first page. This is 417 * not strictly required by the ABI specification, but it seems to 418 * always true in practice. And, it simplifies things considerably. 419 */ 420 if (phdr_in_zero_page(hdr)) { 421 phdr = (Elf_Phdr *)((char *)hdr + hdr->e_phoff); 422 } else { 423 phdr = mmap(NULL, hdr->e_phnum * sizeof(phdr[0]), PROT_READ, 424 MAP_PRIVATE | MAP_PREFAULT_READ, fd, hdr->e_phoff); 425 if (phdr == MAP_FAILED) { 426 _rtld_error("%s: error mapping phdr: %s", path, 427 rtld_strerror(errno)); 428 goto error; 429 } 430 } 431 *phdr_p = phdr; 432 return (hdr); 433 434 error: 435 munmap(hdr, page_size); 436 return (NULL); 437 } 438 439 void 440 obj_free(Obj_Entry *obj) 441 { 442 Objlist_Entry *elm; 443 444 if (obj->tls_static) 445 free_tls_offset(obj); 446 while (obj->needed != NULL) { 447 Needed_Entry *needed = obj->needed; 448 449 obj->needed = needed->next; 450 free(needed); 451 } 452 while (!STAILQ_EMPTY(&obj->names)) { 453 Name_Entry *entry = STAILQ_FIRST(&obj->names); 454 455 STAILQ_REMOVE_HEAD(&obj->names, link); 456 free(entry); 457 } 458 while (!STAILQ_EMPTY(&obj->dldags)) { 459 elm = STAILQ_FIRST(&obj->dldags); 460 STAILQ_REMOVE_HEAD(&obj->dldags, link); 461 free(elm); 462 } 463 while (!STAILQ_EMPTY(&obj->dagmembers)) { 464 elm = STAILQ_FIRST(&obj->dagmembers); 465 STAILQ_REMOVE_HEAD(&obj->dagmembers, link); 466 free(elm); 467 } 468 if (obj->vertab) 469 free(obj->vertab); 470 if (obj->origin_path) 471 free(obj->origin_path); 472 if (obj->z_origin) 473 free(__DECONST(void *, obj->rpath)); 474 if (obj->priv) 475 free(obj->priv); 476 if (obj->path) 477 free(obj->path); 478 if (obj->phdr_alloc) 479 free(__DECONST(void *, obj->phdr)); 480 free(obj); 481 } 482 483 Obj_Entry * 484 obj_new(void) 485 { 486 Obj_Entry *obj; 487 488 obj = CNEW(Obj_Entry); 489 STAILQ_INIT(&obj->dldags); 490 STAILQ_INIT(&obj->dagmembers); 491 STAILQ_INIT(&obj->names); 492 return (obj); 493 } 494 495 /* 496 * Given a set of ELF protection flags, return the corresponding protection 497 * flags for MMAP. 498 */ 499 int 500 convert_prot(int elfflags) 501 { 502 int prot = 0; 503 504 if ((elfflags & PF_R) != 0) 505 prot |= PROT_READ; 506 if ((elfflags & PF_W) != 0) 507 prot |= PROT_WRITE; 508 if ((elfflags & PF_X) != 0) 509 prot |= PROT_EXEC; 510 return (prot); 511 } 512 513 static int 514 convert_flags(int elfflags) 515 { 516 int flags = MAP_PRIVATE; /* All mappings are private */ 517 518 /* 519 * Readonly mappings are marked "MAP_NOCORE", because they can be 520 * reconstructed by a debugger. 521 */ 522 if ((elfflags & PF_W) == 0) 523 flags |= MAP_NOCORE; 524 return (flags); 525 } 526