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 note_start; 97 Elf_Addr note_end; 98 char *note_map; 99 size_t note_map_len; 100 Elf_Addr text_end; 101 102 hdr = get_elf_header(fd, path, sb, &phdr); 103 if (hdr == NULL) 104 return (NULL); 105 106 /* 107 * Scan the program header entries, and save key information. 108 * We expect that the loadable segments are ordered by load address. 109 */ 110 phsize = hdr->e_phnum * sizeof(phdr[0]); 111 phlimit = phdr + hdr->e_phnum; 112 nsegs = -1; 113 phdyn = phinterp = phtls = NULL; 114 phdr_vaddr = 0; 115 note_start = 0; 116 note_end = 0; 117 note_map = NULL; 118 note_map_len = 0; 119 segs = alloca(sizeof(segs[0]) * hdr->e_phnum); 120 stack_flags = PF_X | PF_R | PF_W; 121 text_end = 0; 122 while (phdr < phlimit) { 123 switch (phdr->p_type) { 124 125 case PT_INTERP: 126 phinterp = phdr; 127 break; 128 129 case PT_LOAD: 130 segs[++nsegs] = phdr; 131 if ((segs[nsegs]->p_align & (page_size - 1)) != 0) { 132 _rtld_error("%s: PT_LOAD segment %d not page-aligned", 133 path, nsegs); 134 goto error; 135 } 136 if ((segs[nsegs]->p_flags & PF_X) == PF_X) { 137 text_end = MAX(text_end, 138 rtld_round_page(segs[nsegs]->p_vaddr + 139 segs[nsegs]->p_memsz)); 140 } 141 break; 142 143 case PT_PHDR: 144 phdr_vaddr = phdr->p_vaddr; 145 phsize = phdr->p_memsz; 146 break; 147 148 case PT_DYNAMIC: 149 phdyn = phdr; 150 break; 151 152 case PT_TLS: 153 phtls = phdr; 154 break; 155 156 case PT_GNU_STACK: 157 stack_flags = phdr->p_flags; 158 break; 159 160 case PT_NOTE: 161 if (phdr->p_offset > page_size || 162 phdr->p_offset + phdr->p_filesz > page_size) { 163 note_map_len = rtld_round_page(phdr->p_offset + 164 phdr->p_filesz) - rtld_trunc_page(phdr->p_offset); 165 note_map = mmap(NULL, note_map_len, PROT_READ, 166 MAP_PRIVATE, fd, rtld_trunc_page(phdr->p_offset)); 167 if (note_map == MAP_FAILED) { 168 _rtld_error("%s: error mapping PT_NOTE (%d)", path, errno); 169 goto error; 170 } 171 note_start = (Elf_Addr)(note_map + phdr->p_offset - 172 rtld_trunc_page(phdr->p_offset)); 173 } else { 174 note_start = (Elf_Addr)(char *)hdr + phdr->p_offset; 175 } 176 note_end = note_start + phdr->p_filesz; 177 break; 178 } 179 180 ++phdr; 181 } 182 if (phdyn == NULL) { 183 _rtld_error("%s: object is not dynamically-linked", path); 184 goto error; 185 } 186 187 if (nsegs < 0) { 188 _rtld_error("%s: too few PT_LOAD segments", path); 189 goto error; 190 } 191 192 /* 193 * Map the entire address space of the object, to stake out our 194 * contiguous region, and to establish the base address for relocation. 195 */ 196 base_vaddr = rtld_trunc_page(segs[0]->p_vaddr); 197 base_vlimit = rtld_round_page(segs[nsegs]->p_vaddr + segs[nsegs]->p_memsz); 198 mapsize = base_vlimit - base_vaddr; 199 base_addr = (caddr_t) base_vaddr; 200 base_flags = __getosreldate() >= P_OSREL_MAP_GUARD ? MAP_GUARD : 201 MAP_PRIVATE | MAP_ANON | MAP_NOCORE; 202 if (npagesizes > 1 && rtld_round_page(segs[0]->p_filesz) >= pagesizes[1]) 203 base_flags |= MAP_ALIGNED_SUPER; 204 if (base_vaddr != 0) 205 base_flags |= MAP_FIXED | MAP_EXCL; 206 207 mapbase = mmap(base_addr, mapsize, PROT_NONE, base_flags, -1, 0); 208 if (mapbase == MAP_FAILED) { 209 _rtld_error("%s: mmap of entire address space failed: %s", 210 path, rtld_strerror(errno)); 211 goto error; 212 } 213 if (base_addr != NULL && mapbase != base_addr) { 214 _rtld_error("%s: mmap returned wrong address: wanted %p, got %p", 215 path, base_addr, mapbase); 216 goto error1; 217 } 218 219 for (i = 0; i <= nsegs; i++) { 220 /* Overlay the segment onto the proper region. */ 221 data_offset = rtld_trunc_page(segs[i]->p_offset); 222 data_vaddr = rtld_trunc_page(segs[i]->p_vaddr); 223 data_vlimit = rtld_round_page(segs[i]->p_vaddr + segs[i]->p_filesz); 224 data_addr = mapbase + (data_vaddr - base_vaddr); 225 data_prot = convert_prot(segs[i]->p_flags); 226 data_flags = convert_flags(segs[i]->p_flags) | MAP_FIXED; 227 if (data_vlimit != data_vaddr && 228 mmap(data_addr, data_vlimit - data_vaddr, data_prot, 229 data_flags | MAP_PREFAULT_READ, fd, data_offset) == MAP_FAILED) { 230 _rtld_error("%s: mmap of data failed: %s", path, 231 rtld_strerror(errno)); 232 goto error1; 233 } 234 235 /* Do BSS setup */ 236 if (segs[i]->p_filesz != segs[i]->p_memsz) { 237 238 /* Clear any BSS in the last page of the segment. */ 239 clear_vaddr = segs[i]->p_vaddr + segs[i]->p_filesz; 240 clear_addr = mapbase + (clear_vaddr - base_vaddr); 241 clear_page = mapbase + (rtld_trunc_page(clear_vaddr) - base_vaddr); 242 243 if ((nclear = data_vlimit - clear_vaddr) > 0) { 244 /* Make sure the end of the segment is writable */ 245 if ((data_prot & PROT_WRITE) == 0 && -1 == 246 mprotect(clear_page, page_size, data_prot|PROT_WRITE)) { 247 _rtld_error("%s: mprotect failed: %s", path, 248 rtld_strerror(errno)); 249 goto error1; 250 } 251 252 memset(clear_addr, 0, nclear); 253 254 /* Reset the data protection back */ 255 if ((data_prot & PROT_WRITE) == 0) 256 mprotect(clear_page, page_size, data_prot); 257 } 258 259 /* Overlay the BSS segment onto the proper region. */ 260 bss_vaddr = data_vlimit; 261 bss_vlimit = rtld_round_page(segs[i]->p_vaddr + segs[i]->p_memsz); 262 bss_addr = mapbase + (bss_vaddr - base_vaddr); 263 if (bss_vlimit > bss_vaddr) { /* There is something to do */ 264 if (mmap(bss_addr, bss_vlimit - bss_vaddr, data_prot, 265 data_flags | MAP_ANON, -1, 0) == MAP_FAILED) { 266 _rtld_error("%s: mmap of bss failed: %s", path, 267 rtld_strerror(errno)); 268 goto error1; 269 } 270 } 271 } 272 273 if (phdr_vaddr == 0 && data_offset <= hdr->e_phoff && 274 (data_vlimit - data_vaddr + data_offset) >= 275 (hdr->e_phoff + hdr->e_phnum * sizeof (Elf_Phdr))) { 276 phdr_vaddr = data_vaddr + hdr->e_phoff - data_offset; 277 } 278 } 279 280 obj = obj_new(); 281 if (sb != NULL) { 282 obj->dev = sb->st_dev; 283 obj->ino = sb->st_ino; 284 } 285 obj->mapbase = mapbase; 286 obj->mapsize = mapsize; 287 obj->vaddrbase = base_vaddr; 288 obj->relocbase = mapbase - base_vaddr; 289 obj->dynamic = (const Elf_Dyn *)(obj->relocbase + phdyn->p_vaddr); 290 if (hdr->e_entry != 0) 291 obj->entry = (caddr_t)(obj->relocbase + hdr->e_entry); 292 if (phdr_vaddr != 0) { 293 obj->phdr = (const Elf_Phdr *)(obj->relocbase + phdr_vaddr); 294 } else { 295 obj->phdr = malloc(phsize); 296 if (obj->phdr == NULL) { 297 obj_free(obj); 298 _rtld_error("%s: cannot allocate program header", path); 299 goto error1; 300 } 301 memcpy(__DECONST(char *, obj->phdr), (char *)hdr + hdr->e_phoff, phsize); 302 obj->phdr_alloc = true; 303 } 304 obj->phsize = phsize; 305 if (phinterp != NULL) 306 obj->interp = (const char *)(obj->relocbase + phinterp->p_vaddr); 307 if (phtls != NULL) { 308 tls_dtv_generation++; 309 obj->tlsindex = ++tls_max_index; 310 obj->tlssize = phtls->p_memsz; 311 obj->tlsalign = phtls->p_align; 312 obj->tlspoffset = phtls->p_offset; 313 obj->tlsinitsize = phtls->p_filesz; 314 obj->tlsinit = mapbase + phtls->p_vaddr; 315 } 316 obj->stack_flags = stack_flags; 317 if (note_start < note_end) 318 digest_notes(obj, note_start, note_end); 319 if (note_map != NULL) 320 munmap(note_map, note_map_len); 321 munmap(hdr, page_size); 322 return (obj); 323 324 error1: 325 munmap(mapbase, mapsize); 326 error: 327 if (note_map != NULL && note_map != MAP_FAILED) 328 munmap(note_map, note_map_len); 329 if (!phdr_in_zero_page(hdr)) 330 munmap(phdr, hdr->e_phnum * sizeof(phdr[0])); 331 munmap(hdr, page_size); 332 return (NULL); 333 } 334 335 bool 336 check_elf_headers(const Elf_Ehdr *hdr, const char *path) 337 { 338 if (!IS_ELF(*hdr)) { 339 _rtld_error("%s: invalid file format", path); 340 return (false); 341 } 342 if (hdr->e_ident[EI_CLASS] != ELF_TARG_CLASS || 343 hdr->e_ident[EI_DATA] != ELF_TARG_DATA) { 344 _rtld_error("%s: unsupported file layout", path); 345 return (false); 346 } 347 if (hdr->e_ident[EI_VERSION] != EV_CURRENT || 348 hdr->e_version != EV_CURRENT) { 349 _rtld_error("%s: unsupported file version", path); 350 return (false); 351 } 352 if (hdr->e_type != ET_EXEC && hdr->e_type != ET_DYN) { 353 _rtld_error("%s: unsupported file type", path); 354 return (false); 355 } 356 if (hdr->e_machine != ELF_TARG_MACH) { 357 _rtld_error("%s: unsupported machine", path); 358 return (false); 359 } 360 if (hdr->e_phentsize != sizeof(Elf_Phdr)) { 361 _rtld_error( 362 "%s: invalid shared object: e_phentsize != sizeof(Elf_Phdr)", path); 363 return (false); 364 } 365 return (true); 366 } 367 368 static Elf_Ehdr * 369 get_elf_header(int fd, const char *path, const struct stat *sbp, 370 Elf_Phdr **phdr_p) 371 { 372 Elf_Ehdr *hdr; 373 Elf_Phdr *phdr; 374 375 /* Make sure file has enough data for the ELF header */ 376 if (sbp != NULL && sbp->st_size < (off_t)sizeof(Elf_Ehdr)) { 377 _rtld_error("%s: invalid file format", path); 378 return (NULL); 379 } 380 381 hdr = mmap(NULL, page_size, PROT_READ, MAP_PRIVATE | MAP_PREFAULT_READ, 382 fd, 0); 383 if (hdr == MAP_FAILED) { 384 _rtld_error("%s: read error: %s", path, rtld_strerror(errno)); 385 return (NULL); 386 } 387 388 /* Make sure the file is valid */ 389 if (!check_elf_headers(hdr, path)) 390 goto error; 391 392 /* 393 * We rely on the program header being in the first page. This is 394 * not strictly required by the ABI specification, but it seems to 395 * always true in practice. And, it simplifies things considerably. 396 */ 397 if (phdr_in_zero_page(hdr)) { 398 phdr = (Elf_Phdr *)((char *)hdr + hdr->e_phoff); 399 } else { 400 phdr = mmap(NULL, hdr->e_phnum * sizeof(phdr[0]), 401 PROT_READ, MAP_PRIVATE | MAP_PREFAULT_READ, fd, 402 hdr->e_phoff); 403 if (phdr == MAP_FAILED) { 404 _rtld_error("%s: error mapping phdr: %s", path, 405 rtld_strerror(errno)); 406 goto error; 407 } 408 } 409 *phdr_p = phdr; 410 return (hdr); 411 412 error: 413 munmap(hdr, page_size); 414 return (NULL); 415 } 416 417 void 418 obj_free(Obj_Entry *obj) 419 { 420 Objlist_Entry *elm; 421 422 if (obj->tls_static) 423 free_tls_offset(obj); 424 while (obj->needed != NULL) { 425 Needed_Entry *needed = obj->needed; 426 obj->needed = needed->next; 427 free(needed); 428 } 429 while (!STAILQ_EMPTY(&obj->names)) { 430 Name_Entry *entry = STAILQ_FIRST(&obj->names); 431 STAILQ_REMOVE_HEAD(&obj->names, link); 432 free(entry); 433 } 434 while (!STAILQ_EMPTY(&obj->dldags)) { 435 elm = STAILQ_FIRST(&obj->dldags); 436 STAILQ_REMOVE_HEAD(&obj->dldags, link); 437 free(elm); 438 } 439 while (!STAILQ_EMPTY(&obj->dagmembers)) { 440 elm = STAILQ_FIRST(&obj->dagmembers); 441 STAILQ_REMOVE_HEAD(&obj->dagmembers, link); 442 free(elm); 443 } 444 if (obj->vertab) 445 free(obj->vertab); 446 if (obj->origin_path) 447 free(obj->origin_path); 448 if (obj->z_origin) 449 free(__DECONST(void*, obj->rpath)); 450 if (obj->priv) 451 free(obj->priv); 452 if (obj->path) 453 free(obj->path); 454 if (obj->phdr_alloc) 455 free(__DECONST(void *, obj->phdr)); 456 free(obj); 457 } 458 459 Obj_Entry * 460 obj_new(void) 461 { 462 Obj_Entry *obj; 463 464 obj = CNEW(Obj_Entry); 465 STAILQ_INIT(&obj->dldags); 466 STAILQ_INIT(&obj->dagmembers); 467 STAILQ_INIT(&obj->names); 468 return obj; 469 } 470 471 /* 472 * Given a set of ELF protection flags, return the corresponding protection 473 * flags for MMAP. 474 */ 475 int 476 convert_prot(int elfflags) 477 { 478 int prot = 0; 479 if (elfflags & PF_R) 480 prot |= PROT_READ; 481 if (elfflags & PF_W) 482 prot |= PROT_WRITE; 483 if (elfflags & PF_X) 484 prot |= PROT_EXEC; 485 return prot; 486 } 487 488 static int 489 convert_flags(int elfflags) 490 { 491 int flags = MAP_PRIVATE; /* All mappings are private */ 492 493 /* 494 * Readonly mappings are marked "MAP_NOCORE", because they can be 495 * reconstructed by a debugger. 496 */ 497 if (!(elfflags & PF_W)) 498 flags |= MAP_NOCORE; 499 return flags; 500 } 501