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