1 /*- 2 * Copyright 1996-1998 John D. Polstra. 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 15 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 16 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 17 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 18 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 19 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 20 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 21 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 22 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 23 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 24 * 25 * $FreeBSD$ 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 static int convert_flags(int); /* Elf flags -> mmap flags */ 43 44 int __getosreldate(void); 45 46 /* 47 * Map a shared object into memory. The "fd" argument is a file descriptor, 48 * which must be open on the object and positioned at its beginning. 49 * The "path" argument is a pathname that is used only for error messages. 50 * 51 * The return value is a pointer to a newly-allocated Obj_Entry structure 52 * for the shared object. Returns NULL on failure. 53 */ 54 Obj_Entry * 55 map_object(int fd, const char *path, const struct stat *sb) 56 { 57 Obj_Entry *obj; 58 Elf_Ehdr *hdr; 59 int i; 60 Elf_Phdr *phdr; 61 Elf_Phdr *phlimit; 62 Elf_Phdr **segs; 63 int nsegs; 64 Elf_Phdr *phdyn; 65 Elf_Phdr *phinterp; 66 Elf_Phdr *phtls; 67 caddr_t mapbase; 68 size_t mapsize; 69 Elf_Addr base_vaddr; 70 Elf_Addr base_vlimit; 71 caddr_t base_addr; 72 int base_flags; 73 Elf_Off data_offset; 74 Elf_Addr data_vaddr; 75 Elf_Addr data_vlimit; 76 caddr_t data_addr; 77 int data_prot; 78 int data_flags; 79 Elf_Addr clear_vaddr; 80 caddr_t clear_addr; 81 caddr_t clear_page; 82 Elf_Addr phdr_vaddr; 83 size_t nclear, phsize; 84 Elf_Addr bss_vaddr; 85 Elf_Addr bss_vlimit; 86 caddr_t bss_addr; 87 Elf_Word stack_flags; 88 Elf_Addr relro_page; 89 size_t relro_size; 90 Elf_Addr note_start; 91 Elf_Addr note_end; 92 char *note_map; 93 size_t note_map_len; 94 95 hdr = get_elf_header(fd, path, sb); 96 if (hdr == NULL) 97 return (NULL); 98 99 /* 100 * Scan the program header entries, and save key information. 101 * 102 * We expect that the loadable segments are ordered by load address. 103 */ 104 phdr = (Elf_Phdr *) ((char *)hdr + hdr->e_phoff); 105 phsize = hdr->e_phnum * sizeof (phdr[0]); 106 phlimit = phdr + hdr->e_phnum; 107 nsegs = -1; 108 phdyn = phinterp = phtls = NULL; 109 phdr_vaddr = 0; 110 relro_page = 0; 111 relro_size = 0; 112 note_start = 0; 113 note_end = 0; 114 note_map = NULL; 115 segs = alloca(sizeof(segs[0]) * hdr->e_phnum); 116 stack_flags = RTLD_DEFAULT_STACK_PF_EXEC | PF_R | PF_W; 117 while (phdr < phlimit) { 118 switch (phdr->p_type) { 119 120 case PT_INTERP: 121 phinterp = phdr; 122 break; 123 124 case PT_LOAD: 125 segs[++nsegs] = phdr; 126 if ((segs[nsegs]->p_align & (PAGE_SIZE - 1)) != 0) { 127 _rtld_error("%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_GNU_RELRO: 151 relro_page = phdr->p_vaddr; 152 relro_size = phdr->p_memsz; 153 break; 154 155 case PT_NOTE: 156 if (phdr->p_offset > PAGE_SIZE || 157 phdr->p_offset + phdr->p_filesz > PAGE_SIZE) { 158 note_map_len = round_page(phdr->p_offset + 159 phdr->p_filesz) - trunc_page(phdr->p_offset); 160 note_map = mmap(NULL, note_map_len, PROT_READ, 161 MAP_PRIVATE, fd, trunc_page(phdr->p_offset)); 162 if (note_map == MAP_FAILED) { 163 _rtld_error("%s: error mapping PT_NOTE (%d)", path, errno); 164 goto error; 165 } 166 note_start = (Elf_Addr)(note_map + phdr->p_offset - 167 trunc_page(phdr->p_offset)); 168 } else { 169 note_start = (Elf_Addr)(char *)hdr + phdr->p_offset; 170 } 171 note_end = note_start + phdr->p_filesz; 172 break; 173 } 174 175 ++phdr; 176 } 177 if (phdyn == NULL) { 178 _rtld_error("%s: object is not dynamically-linked", path); 179 goto error; 180 } 181 182 if (nsegs < 0) { 183 _rtld_error("%s: too few PT_LOAD segments", path); 184 goto error; 185 } 186 187 /* 188 * Map the entire address space of the object, to stake out our 189 * contiguous region, and to establish the base address for relocation. 190 */ 191 base_vaddr = trunc_page(segs[0]->p_vaddr); 192 base_vlimit = round_page(segs[nsegs]->p_vaddr + segs[nsegs]->p_memsz); 193 mapsize = base_vlimit - base_vaddr; 194 base_addr = (caddr_t) base_vaddr; 195 base_flags = __getosreldate() >= P_OSREL_MAP_GUARD ? MAP_GUARD : 196 MAP_PRIVATE | MAP_ANON | MAP_NOCORE; 197 if (npagesizes > 1 && round_page(segs[0]->p_filesz) >= pagesizes[1]) 198 base_flags |= MAP_ALIGNED_SUPER; 199 if (base_vaddr != 0) 200 base_flags |= MAP_FIXED | MAP_EXCL; 201 202 mapbase = mmap(base_addr, mapsize, PROT_NONE, base_flags, -1, 0); 203 if (mapbase == (caddr_t) -1) { 204 _rtld_error("%s: mmap of entire address space failed: %s", 205 path, rtld_strerror(errno)); 206 goto error; 207 } 208 if (base_addr != NULL && mapbase != base_addr) { 209 _rtld_error("%s: mmap returned wrong address: wanted %p, got %p", 210 path, base_addr, mapbase); 211 goto error1; 212 } 213 214 for (i = 0; i <= nsegs; i++) { 215 /* Overlay the segment onto the proper region. */ 216 data_offset = trunc_page(segs[i]->p_offset); 217 data_vaddr = trunc_page(segs[i]->p_vaddr); 218 data_vlimit = round_page(segs[i]->p_vaddr + segs[i]->p_filesz); 219 data_addr = mapbase + (data_vaddr - base_vaddr); 220 data_prot = convert_prot(segs[i]->p_flags); 221 data_flags = convert_flags(segs[i]->p_flags) | MAP_FIXED; 222 if (mmap(data_addr, data_vlimit - data_vaddr, data_prot, 223 data_flags | MAP_PREFAULT_READ, fd, data_offset) == (caddr_t) -1) { 224 _rtld_error("%s: mmap of data failed: %s", path, 225 rtld_strerror(errno)); 226 goto error1; 227 } 228 229 /* Do BSS setup */ 230 if (segs[i]->p_filesz != segs[i]->p_memsz) { 231 232 /* Clear any BSS in the last page of the segment. */ 233 clear_vaddr = segs[i]->p_vaddr + segs[i]->p_filesz; 234 clear_addr = mapbase + (clear_vaddr - base_vaddr); 235 clear_page = mapbase + (trunc_page(clear_vaddr) - base_vaddr); 236 237 if ((nclear = data_vlimit - clear_vaddr) > 0) { 238 /* Make sure the end of the segment is writable */ 239 if ((data_prot & PROT_WRITE) == 0 && -1 == 240 mprotect(clear_page, PAGE_SIZE, data_prot|PROT_WRITE)) { 241 _rtld_error("%s: mprotect failed: %s", path, 242 rtld_strerror(errno)); 243 goto error1; 244 } 245 246 memset(clear_addr, 0, nclear); 247 248 /* Reset the data protection back */ 249 if ((data_prot & PROT_WRITE) == 0) 250 mprotect(clear_page, PAGE_SIZE, data_prot); 251 } 252 253 /* Overlay the BSS segment onto the proper region. */ 254 bss_vaddr = data_vlimit; 255 bss_vlimit = round_page(segs[i]->p_vaddr + segs[i]->p_memsz); 256 bss_addr = mapbase + (bss_vaddr - base_vaddr); 257 if (bss_vlimit > bss_vaddr) { /* There is something to do */ 258 if (mmap(bss_addr, bss_vlimit - bss_vaddr, data_prot, 259 data_flags | MAP_ANON, -1, 0) == (caddr_t)-1) { 260 _rtld_error("%s: mmap of bss failed: %s", path, 261 rtld_strerror(errno)); 262 goto error1; 263 } 264 } 265 } 266 267 if (phdr_vaddr == 0 && data_offset <= hdr->e_phoff && 268 (data_vlimit - data_vaddr + data_offset) >= 269 (hdr->e_phoff + hdr->e_phnum * sizeof (Elf_Phdr))) { 270 phdr_vaddr = data_vaddr + hdr->e_phoff - data_offset; 271 } 272 } 273 274 obj = obj_new(); 275 if (sb != NULL) { 276 obj->dev = sb->st_dev; 277 obj->ino = sb->st_ino; 278 } 279 obj->mapbase = mapbase; 280 obj->mapsize = mapsize; 281 obj->textsize = round_page(segs[0]->p_vaddr + segs[0]->p_memsz) - 282 base_vaddr; 283 obj->vaddrbase = base_vaddr; 284 obj->relocbase = mapbase - base_vaddr; 285 obj->dynamic = (const Elf_Dyn *) (obj->relocbase + phdyn->p_vaddr); 286 if (hdr->e_entry != 0) 287 obj->entry = (caddr_t) (obj->relocbase + hdr->e_entry); 288 if (phdr_vaddr != 0) { 289 obj->phdr = (const Elf_Phdr *) (obj->relocbase + phdr_vaddr); 290 } else { 291 obj->phdr = malloc(phsize); 292 if (obj->phdr == NULL) { 293 obj_free(obj); 294 _rtld_error("%s: cannot allocate program header", path); 295 goto error1; 296 } 297 memcpy((char *)obj->phdr, (char *)hdr + hdr->e_phoff, phsize); 298 obj->phdr_alloc = true; 299 } 300 obj->phsize = phsize; 301 if (phinterp != NULL) 302 obj->interp = (const char *) (obj->relocbase + phinterp->p_vaddr); 303 if (phtls != NULL) { 304 tls_dtv_generation++; 305 obj->tlsindex = ++tls_max_index; 306 obj->tlssize = phtls->p_memsz; 307 obj->tlsalign = phtls->p_align; 308 obj->tlsinitsize = phtls->p_filesz; 309 obj->tlsinit = mapbase + phtls->p_vaddr; 310 } 311 obj->stack_flags = stack_flags; 312 obj->relro_page = obj->relocbase + trunc_page(relro_page); 313 obj->relro_size = round_page(relro_size); 314 if (note_start < note_end) 315 digest_notes(obj, note_start, note_end); 316 if (note_map != NULL) 317 munmap(note_map, note_map_len); 318 munmap(hdr, PAGE_SIZE); 319 return (obj); 320 321 error1: 322 munmap(mapbase, mapsize); 323 error: 324 if (note_map != NULL && note_map != MAP_FAILED) 325 munmap(note_map, note_map_len); 326 munmap(hdr, PAGE_SIZE); 327 return (NULL); 328 } 329 330 static Elf_Ehdr * 331 get_elf_header(int fd, const char *path, const struct stat *sbp) 332 { 333 Elf_Ehdr *hdr; 334 335 /* Make sure file has enough data for the ELF header */ 336 if (sbp != NULL && sbp->st_size < sizeof(Elf_Ehdr)) { 337 _rtld_error("%s: invalid file format", path); 338 return (NULL); 339 } 340 341 hdr = mmap(NULL, PAGE_SIZE, PROT_READ, MAP_PRIVATE | MAP_PREFAULT_READ, 342 fd, 0); 343 if (hdr == (Elf_Ehdr *)MAP_FAILED) { 344 _rtld_error("%s: read error: %s", path, rtld_strerror(errno)); 345 return (NULL); 346 } 347 348 /* Make sure the file is valid */ 349 if (!IS_ELF(*hdr)) { 350 _rtld_error("%s: invalid file format", path); 351 goto error; 352 } 353 if (hdr->e_ident[EI_CLASS] != ELF_TARG_CLASS || 354 hdr->e_ident[EI_DATA] != ELF_TARG_DATA) { 355 _rtld_error("%s: unsupported file layout", path); 356 goto error; 357 } 358 if (hdr->e_ident[EI_VERSION] != EV_CURRENT || 359 hdr->e_version != EV_CURRENT) { 360 _rtld_error("%s: unsupported file version", path); 361 goto error; 362 } 363 if (hdr->e_type != ET_EXEC && hdr->e_type != ET_DYN) { 364 _rtld_error("%s: unsupported file type", path); 365 goto error; 366 } 367 if (hdr->e_machine != ELF_TARG_MACH) { 368 _rtld_error("%s: unsupported machine", path); 369 goto error; 370 } 371 372 /* 373 * We rely on the program header being in the first page. This is 374 * not strictly required by the ABI specification, but it seems to 375 * always true in practice. And, it simplifies things considerably. 376 */ 377 if (hdr->e_phentsize != sizeof(Elf_Phdr)) { 378 _rtld_error( 379 "%s: invalid shared object: e_phentsize != sizeof(Elf_Phdr)", path); 380 goto error; 381 } 382 if (hdr->e_phoff + hdr->e_phnum * sizeof(Elf_Phdr) > 383 (size_t)PAGE_SIZE) { 384 _rtld_error("%s: program header too large", path); 385 goto error; 386 } 387 return (hdr); 388 389 error: 390 munmap(hdr, PAGE_SIZE); 391 return (NULL); 392 } 393 394 void 395 obj_free(Obj_Entry *obj) 396 { 397 Objlist_Entry *elm; 398 399 if (obj->tls_done) 400 free_tls_offset(obj); 401 while (obj->needed != NULL) { 402 Needed_Entry *needed = obj->needed; 403 obj->needed = needed->next; 404 free(needed); 405 } 406 while (!STAILQ_EMPTY(&obj->names)) { 407 Name_Entry *entry = STAILQ_FIRST(&obj->names); 408 STAILQ_REMOVE_HEAD(&obj->names, link); 409 free(entry); 410 } 411 while (!STAILQ_EMPTY(&obj->dldags)) { 412 elm = STAILQ_FIRST(&obj->dldags); 413 STAILQ_REMOVE_HEAD(&obj->dldags, link); 414 free(elm); 415 } 416 while (!STAILQ_EMPTY(&obj->dagmembers)) { 417 elm = STAILQ_FIRST(&obj->dagmembers); 418 STAILQ_REMOVE_HEAD(&obj->dagmembers, link); 419 free(elm); 420 } 421 if (obj->vertab) 422 free(obj->vertab); 423 if (obj->origin_path) 424 free(obj->origin_path); 425 if (obj->z_origin) 426 free(obj->rpath); 427 if (obj->priv) 428 free(obj->priv); 429 if (obj->path) 430 free(obj->path); 431 if (obj->phdr_alloc) 432 free((void *)obj->phdr); 433 free(obj); 434 } 435 436 Obj_Entry * 437 obj_new(void) 438 { 439 Obj_Entry *obj; 440 441 obj = CNEW(Obj_Entry); 442 STAILQ_INIT(&obj->dldags); 443 STAILQ_INIT(&obj->dagmembers); 444 STAILQ_INIT(&obj->names); 445 return obj; 446 } 447 448 /* 449 * Given a set of ELF protection flags, return the corresponding protection 450 * flags for MMAP. 451 */ 452 int 453 convert_prot(int elfflags) 454 { 455 int prot = 0; 456 if (elfflags & PF_R) 457 prot |= PROT_READ; 458 if (elfflags & PF_W) 459 prot |= PROT_WRITE; 460 if (elfflags & PF_X) 461 prot |= PROT_EXEC; 462 return prot; 463 } 464 465 static int 466 convert_flags(int elfflags) 467 { 468 int flags = MAP_PRIVATE; /* All mappings are private */ 469 470 /* 471 * Readonly mappings are marked "MAP_NOCORE", because they can be 472 * reconstructed by a debugger. 473 */ 474 if (!(elfflags & PF_W)) 475 flags |= MAP_NOCORE; 476 return flags; 477 } 478