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