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 static int convert_flags(int); /* Elf flags -> mmap flags */ 45 46 int __getosreldate(void); 47 48 /* 49 * Map a shared object into memory. The "fd" argument is a file descriptor, 50 * which must be open on the object and positioned at its beginning. 51 * The "path" argument is a pathname that is used only for error messages. 52 * 53 * The return value is a pointer to a newly-allocated Obj_Entry structure 54 * for the shared object. Returns NULL on failure. 55 */ 56 Obj_Entry * 57 map_object(int fd, const char *path, const struct stat *sb) 58 { 59 Obj_Entry *obj; 60 Elf_Ehdr *hdr; 61 int i; 62 Elf_Phdr *phdr; 63 Elf_Phdr *phlimit; 64 Elf_Phdr **segs; 65 int nsegs; 66 Elf_Phdr *phdyn; 67 Elf_Phdr *phinterp; 68 Elf_Phdr *phtls; 69 caddr_t mapbase; 70 size_t mapsize; 71 Elf_Addr base_vaddr; 72 Elf_Addr base_vlimit; 73 caddr_t base_addr; 74 int base_flags; 75 Elf_Off data_offset; 76 Elf_Addr data_vaddr; 77 Elf_Addr data_vlimit; 78 caddr_t data_addr; 79 int data_prot; 80 int data_flags; 81 Elf_Addr clear_vaddr; 82 caddr_t clear_addr; 83 caddr_t clear_page; 84 Elf_Addr phdr_vaddr; 85 size_t nclear, phsize; 86 Elf_Addr bss_vaddr; 87 Elf_Addr bss_vlimit; 88 caddr_t bss_addr; 89 Elf_Word stack_flags; 90 Elf_Addr relro_page; 91 size_t relro_size; 92 Elf_Addr note_start; 93 Elf_Addr note_end; 94 char *note_map; 95 size_t note_map_len; 96 Elf_Addr text_end; 97 98 hdr = get_elf_header(fd, path, sb); 99 if (hdr == NULL) 100 return (NULL); 101 102 /* 103 * Scan the program header entries, and save key information. 104 * 105 * We expect that the loadable segments are ordered by load address. 106 */ 107 phdr = (Elf_Phdr *)((char *)hdr + hdr->e_phoff); 108 phsize = hdr->e_phnum * sizeof (phdr[0]); 109 phlimit = phdr + hdr->e_phnum; 110 nsegs = -1; 111 phdyn = phinterp = phtls = NULL; 112 phdr_vaddr = 0; 113 relro_page = 0; 114 relro_size = 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 = RTLD_DEFAULT_STACK_PF_EXEC | 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 round_page(segs[nsegs]->p_vaddr + segs[nsegs]->p_memsz)); 139 } 140 break; 141 142 case PT_PHDR: 143 phdr_vaddr = phdr->p_vaddr; 144 phsize = phdr->p_memsz; 145 break; 146 147 case PT_DYNAMIC: 148 phdyn = phdr; 149 break; 150 151 case PT_TLS: 152 phtls = phdr; 153 break; 154 155 case PT_GNU_STACK: 156 stack_flags = phdr->p_flags; 157 break; 158 159 case PT_GNU_RELRO: 160 relro_page = phdr->p_vaddr; 161 relro_size = phdr->p_memsz; 162 break; 163 164 case PT_NOTE: 165 if (phdr->p_offset > PAGE_SIZE || 166 phdr->p_offset + phdr->p_filesz > PAGE_SIZE) { 167 note_map_len = round_page(phdr->p_offset + 168 phdr->p_filesz) - trunc_page(phdr->p_offset); 169 note_map = mmap(NULL, note_map_len, PROT_READ, 170 MAP_PRIVATE, fd, trunc_page(phdr->p_offset)); 171 if (note_map == MAP_FAILED) { 172 _rtld_error("%s: error mapping PT_NOTE (%d)", path, errno); 173 goto error; 174 } 175 note_start = (Elf_Addr)(note_map + phdr->p_offset - 176 trunc_page(phdr->p_offset)); 177 } else { 178 note_start = (Elf_Addr)(char *)hdr + phdr->p_offset; 179 } 180 note_end = note_start + phdr->p_filesz; 181 break; 182 } 183 184 ++phdr; 185 } 186 if (phdyn == NULL) { 187 _rtld_error("%s: object is not dynamically-linked", path); 188 goto error; 189 } 190 191 if (nsegs < 0) { 192 _rtld_error("%s: too few PT_LOAD segments", path); 193 goto error; 194 } 195 196 /* 197 * Map the entire address space of the object, to stake out our 198 * contiguous region, and to establish the base address for relocation. 199 */ 200 base_vaddr = trunc_page(segs[0]->p_vaddr); 201 base_vlimit = round_page(segs[nsegs]->p_vaddr + segs[nsegs]->p_memsz); 202 mapsize = base_vlimit - base_vaddr; 203 base_addr = (caddr_t) base_vaddr; 204 base_flags = __getosreldate() >= P_OSREL_MAP_GUARD ? MAP_GUARD : 205 MAP_PRIVATE | MAP_ANON | MAP_NOCORE; 206 if (npagesizes > 1 && round_page(segs[0]->p_filesz) >= pagesizes[1]) 207 base_flags |= MAP_ALIGNED_SUPER; 208 if (base_vaddr != 0) 209 base_flags |= MAP_FIXED | MAP_EXCL; 210 211 mapbase = mmap(base_addr, mapsize, PROT_NONE, base_flags, -1, 0); 212 if (mapbase == MAP_FAILED) { 213 _rtld_error("%s: mmap of entire address space failed: %s", 214 path, rtld_strerror(errno)); 215 goto error; 216 } 217 if (base_addr != NULL && mapbase != base_addr) { 218 _rtld_error("%s: mmap returned wrong address: wanted %p, got %p", 219 path, base_addr, mapbase); 220 goto error1; 221 } 222 223 for (i = 0; i <= nsegs; i++) { 224 /* Overlay the segment onto the proper region. */ 225 data_offset = trunc_page(segs[i]->p_offset); 226 data_vaddr = trunc_page(segs[i]->p_vaddr); 227 data_vlimit = round_page(segs[i]->p_vaddr + segs[i]->p_filesz); 228 data_addr = mapbase + (data_vaddr - base_vaddr); 229 data_prot = convert_prot(segs[i]->p_flags); 230 data_flags = convert_flags(segs[i]->p_flags) | MAP_FIXED; 231 if (data_vlimit != data_vaddr && 232 mmap(data_addr, data_vlimit - data_vaddr, data_prot, 233 data_flags | MAP_PREFAULT_READ, fd, data_offset) == MAP_FAILED) { 234 _rtld_error("%s: mmap of data failed: %s", path, 235 rtld_strerror(errno)); 236 goto error1; 237 } 238 239 /* Do BSS setup */ 240 if (segs[i]->p_filesz != segs[i]->p_memsz) { 241 242 /* Clear any BSS in the last page of the segment. */ 243 clear_vaddr = segs[i]->p_vaddr + segs[i]->p_filesz; 244 clear_addr = mapbase + (clear_vaddr - base_vaddr); 245 clear_page = mapbase + (trunc_page(clear_vaddr) - base_vaddr); 246 247 if ((nclear = data_vlimit - clear_vaddr) > 0) { 248 /* Make sure the end of the segment is writable */ 249 if ((data_prot & PROT_WRITE) == 0 && -1 == 250 mprotect(clear_page, PAGE_SIZE, data_prot|PROT_WRITE)) { 251 _rtld_error("%s: mprotect failed: %s", path, 252 rtld_strerror(errno)); 253 goto error1; 254 } 255 256 memset(clear_addr, 0, nclear); 257 258 /* Reset the data protection back */ 259 if ((data_prot & PROT_WRITE) == 0) 260 mprotect(clear_page, PAGE_SIZE, data_prot); 261 } 262 263 /* Overlay the BSS segment onto the proper region. */ 264 bss_vaddr = data_vlimit; 265 bss_vlimit = round_page(segs[i]->p_vaddr + segs[i]->p_memsz); 266 bss_addr = mapbase + (bss_vaddr - base_vaddr); 267 if (bss_vlimit > bss_vaddr) { /* There is something to do */ 268 if (mmap(bss_addr, bss_vlimit - bss_vaddr, data_prot, 269 data_flags | MAP_ANON, -1, 0) == MAP_FAILED) { 270 _rtld_error("%s: mmap of bss failed: %s", path, 271 rtld_strerror(errno)); 272 goto error1; 273 } 274 } 275 } 276 277 if (phdr_vaddr == 0 && data_offset <= hdr->e_phoff && 278 (data_vlimit - data_vaddr + data_offset) >= 279 (hdr->e_phoff + hdr->e_phnum * sizeof (Elf_Phdr))) { 280 phdr_vaddr = data_vaddr + hdr->e_phoff - data_offset; 281 } 282 } 283 284 obj = obj_new(); 285 if (sb != NULL) { 286 obj->dev = sb->st_dev; 287 obj->ino = sb->st_ino; 288 } 289 obj->mapbase = mapbase; 290 obj->mapsize = mapsize; 291 obj->vaddrbase = base_vaddr; 292 obj->relocbase = mapbase - base_vaddr; 293 obj->dynamic = (const Elf_Dyn *)(obj->relocbase + phdyn->p_vaddr); 294 if (hdr->e_entry != 0) 295 obj->entry = (caddr_t)(obj->relocbase + hdr->e_entry); 296 if (phdr_vaddr != 0) { 297 obj->phdr = (const Elf_Phdr *)(obj->relocbase + phdr_vaddr); 298 } else { 299 obj->phdr = malloc(phsize); 300 if (obj->phdr == NULL) { 301 obj_free(obj); 302 _rtld_error("%s: cannot allocate program header", path); 303 goto error1; 304 } 305 memcpy(__DECONST(char *, obj->phdr), (char *)hdr + hdr->e_phoff, phsize); 306 obj->phdr_alloc = true; 307 } 308 obj->phsize = phsize; 309 if (phinterp != NULL) 310 obj->interp = (const char *)(obj->relocbase + phinterp->p_vaddr); 311 if (phtls != NULL) { 312 tls_dtv_generation++; 313 obj->tlsindex = ++tls_max_index; 314 obj->tlssize = phtls->p_memsz; 315 obj->tlsalign = phtls->p_align; 316 obj->tlsinitsize = phtls->p_filesz; 317 obj->tlsinit = mapbase + phtls->p_vaddr; 318 } 319 obj->stack_flags = stack_flags; 320 obj->relro_page = obj->relocbase + trunc_page(relro_page); 321 obj->relro_size = round_page(relro_size); 322 if (note_start < note_end) 323 digest_notes(obj, note_start, note_end); 324 if (note_map != NULL) 325 munmap(note_map, note_map_len); 326 munmap(hdr, PAGE_SIZE); 327 return (obj); 328 329 error1: 330 munmap(mapbase, mapsize); 331 error: 332 if (note_map != NULL && note_map != MAP_FAILED) 333 munmap(note_map, note_map_len); 334 munmap(hdr, PAGE_SIZE); 335 return (NULL); 336 } 337 338 static Elf_Ehdr * 339 get_elf_header(int fd, const char *path, const struct stat *sbp) 340 { 341 Elf_Ehdr *hdr; 342 343 /* Make sure file has enough data for the ELF header */ 344 if (sbp != NULL && sbp->st_size < (off_t)sizeof(Elf_Ehdr)) { 345 _rtld_error("%s: invalid file format", path); 346 return (NULL); 347 } 348 349 hdr = mmap(NULL, PAGE_SIZE, PROT_READ, MAP_PRIVATE | MAP_PREFAULT_READ, 350 fd, 0); 351 if (hdr == MAP_FAILED) { 352 _rtld_error("%s: read error: %s", path, rtld_strerror(errno)); 353 return (NULL); 354 } 355 356 /* Make sure the file is valid */ 357 if (!IS_ELF(*hdr)) { 358 _rtld_error("%s: invalid file format", path); 359 goto error; 360 } 361 if (hdr->e_ident[EI_CLASS] != ELF_TARG_CLASS || 362 hdr->e_ident[EI_DATA] != ELF_TARG_DATA) { 363 _rtld_error("%s: unsupported file layout", path); 364 goto error; 365 } 366 if (hdr->e_ident[EI_VERSION] != EV_CURRENT || 367 hdr->e_version != EV_CURRENT) { 368 _rtld_error("%s: unsupported file version", path); 369 goto error; 370 } 371 if (hdr->e_type != ET_EXEC && hdr->e_type != ET_DYN) { 372 _rtld_error("%s: unsupported file type", path); 373 goto error; 374 } 375 if (hdr->e_machine != ELF_TARG_MACH) { 376 _rtld_error("%s: unsupported machine", path); 377 goto error; 378 } 379 380 /* 381 * We rely on the program header being in the first page. This is 382 * not strictly required by the ABI specification, but it seems to 383 * always true in practice. And, it simplifies things considerably. 384 */ 385 if (hdr->e_phentsize != sizeof(Elf_Phdr)) { 386 _rtld_error( 387 "%s: invalid shared object: e_phentsize != sizeof(Elf_Phdr)", path); 388 goto error; 389 } 390 if (hdr->e_phoff + hdr->e_phnum * sizeof(Elf_Phdr) > 391 (size_t)PAGE_SIZE) { 392 _rtld_error("%s: program header too large", path); 393 goto error; 394 } 395 return (hdr); 396 397 error: 398 munmap(hdr, PAGE_SIZE); 399 return (NULL); 400 } 401 402 void 403 obj_free(Obj_Entry *obj) 404 { 405 Objlist_Entry *elm; 406 407 if (obj->tls_done) 408 free_tls_offset(obj); 409 while (obj->needed != NULL) { 410 Needed_Entry *needed = obj->needed; 411 obj->needed = needed->next; 412 free(needed); 413 } 414 while (!STAILQ_EMPTY(&obj->names)) { 415 Name_Entry *entry = STAILQ_FIRST(&obj->names); 416 STAILQ_REMOVE_HEAD(&obj->names, link); 417 free(entry); 418 } 419 while (!STAILQ_EMPTY(&obj->dldags)) { 420 elm = STAILQ_FIRST(&obj->dldags); 421 STAILQ_REMOVE_HEAD(&obj->dldags, link); 422 free(elm); 423 } 424 while (!STAILQ_EMPTY(&obj->dagmembers)) { 425 elm = STAILQ_FIRST(&obj->dagmembers); 426 STAILQ_REMOVE_HEAD(&obj->dagmembers, link); 427 free(elm); 428 } 429 if (obj->vertab) 430 free(obj->vertab); 431 if (obj->origin_path) 432 free(obj->origin_path); 433 if (obj->z_origin) 434 free(__DECONST(void*, obj->rpath)); 435 if (obj->priv) 436 free(obj->priv); 437 if (obj->path) 438 free(obj->path); 439 if (obj->phdr_alloc) 440 free(__DECONST(void *, obj->phdr)); 441 free(obj); 442 } 443 444 Obj_Entry * 445 obj_new(void) 446 { 447 Obj_Entry *obj; 448 449 obj = CNEW(Obj_Entry); 450 STAILQ_INIT(&obj->dldags); 451 STAILQ_INIT(&obj->dagmembers); 452 STAILQ_INIT(&obj->names); 453 return obj; 454 } 455 456 /* 457 * Given a set of ELF protection flags, return the corresponding protection 458 * flags for MMAP. 459 */ 460 int 461 convert_prot(int elfflags) 462 { 463 int prot = 0; 464 if (elfflags & PF_R) 465 prot |= PROT_READ; 466 if (elfflags & PF_W) 467 prot |= PROT_WRITE; 468 if (elfflags & PF_X) 469 prot |= PROT_EXEC; 470 return prot; 471 } 472 473 static int 474 convert_flags(int elfflags) 475 { 476 int flags = MAP_PRIVATE; /* All mappings are private */ 477 478 /* 479 * Readonly mappings are marked "MAP_NOCORE", because they can be 480 * reconstructed by a debugger. 481 */ 482 if (!(elfflags & PF_W)) 483 flags |= MAP_NOCORE; 484 return flags; 485 } 486