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