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