map_object.c revision 296939
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: stable/10/libexec/rtld-elf/map_object.c 296939 2016-03-16 15:34:16Z kib $ 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 41static Elf_Ehdr *get_elf_header(int, const char *); 42static int convert_flags(int); /* Elf flags -> mmap flags */ 43 44/* 45 * Map a shared object into memory. The "fd" argument is a file descriptor, 46 * which must be open on the object and positioned at its beginning. 47 * The "path" argument is a pathname that is used only for error messages. 48 * 49 * The return value is a pointer to a newly-allocated Obj_Entry structure 50 * for the shared object. Returns NULL on failure. 51 */ 52Obj_Entry * 53map_object(int fd, const char *path, const struct stat *sb) 54{ 55 Obj_Entry *obj; 56 Elf_Ehdr *hdr; 57 int i; 58 Elf_Phdr *phdr; 59 Elf_Phdr *phlimit; 60 Elf_Phdr **segs; 61 int nsegs; 62 Elf_Phdr *phdyn; 63 Elf_Phdr *phinterp; 64 Elf_Phdr *phtls; 65 caddr_t mapbase; 66 size_t mapsize; 67 Elf_Addr base_vaddr; 68 Elf_Addr base_vlimit; 69 caddr_t base_addr; 70 int base_flags; 71 Elf_Off data_offset; 72 Elf_Addr data_vaddr; 73 Elf_Addr data_vlimit; 74 caddr_t data_addr; 75 int data_prot; 76 int data_flags; 77 Elf_Addr clear_vaddr; 78 caddr_t clear_addr; 79 caddr_t clear_page; 80 Elf_Addr phdr_vaddr; 81 size_t nclear, phsize; 82 Elf_Addr bss_vaddr; 83 Elf_Addr bss_vlimit; 84 caddr_t bss_addr; 85 Elf_Word stack_flags; 86 Elf_Addr relro_page; 87 size_t relro_size; 88 Elf_Addr note_start; 89 Elf_Addr note_end; 90 char *note_map; 91 size_t note_map_len; 92 93 hdr = get_elf_header(fd, path); 94 if (hdr == NULL) 95 return (NULL); 96 97 /* 98 * Scan the program header entries, and save key information. 99 * 100 * We expect that the loadable segments are ordered by load address. 101 */ 102 phdr = (Elf_Phdr *) ((char *)hdr + hdr->e_phoff); 103 phsize = hdr->e_phnum * sizeof (phdr[0]); 104 phlimit = phdr + hdr->e_phnum; 105 nsegs = -1; 106 phdyn = phinterp = phtls = NULL; 107 phdr_vaddr = 0; 108 relro_page = 0; 109 relro_size = 0; 110 note_start = 0; 111 note_end = 0; 112 note_map = NULL; 113 segs = alloca(sizeof(segs[0]) * hdr->e_phnum); 114 stack_flags = RTLD_DEFAULT_STACK_PF_EXEC | PF_R | PF_W; 115 while (phdr < phlimit) { 116 switch (phdr->p_type) { 117 118 case PT_INTERP: 119 phinterp = phdr; 120 break; 121 122 case PT_LOAD: 123 segs[++nsegs] = phdr; 124 if ((segs[nsegs]->p_align & (PAGE_SIZE - 1)) != 0) { 125 _rtld_error("%s: PT_LOAD segment %d not page-aligned", 126 path, nsegs); 127 goto error; 128 } 129 break; 130 131 case PT_PHDR: 132 phdr_vaddr = phdr->p_vaddr; 133 phsize = phdr->p_memsz; 134 break; 135 136 case PT_DYNAMIC: 137 phdyn = phdr; 138 break; 139 140 case PT_TLS: 141 phtls = phdr; 142 break; 143 144 case PT_GNU_STACK: 145 stack_flags = phdr->p_flags; 146 break; 147 148 case PT_GNU_RELRO: 149 relro_page = phdr->p_vaddr; 150 relro_size = phdr->p_memsz; 151 break; 152 153 case PT_NOTE: 154 if (phdr->p_offset > PAGE_SIZE || 155 phdr->p_offset + phdr->p_filesz > PAGE_SIZE) { 156 note_map_len = round_page(phdr->p_offset + 157 phdr->p_filesz) - trunc_page(phdr->p_offset); 158 note_map = mmap(NULL, note_map_len, PROT_READ, 159 MAP_PRIVATE, fd, trunc_page(phdr->p_offset)); 160 if (note_map == MAP_FAILED) { 161 _rtld_error("%s: error mapping PT_NOTE (%d)", path, errno); 162 goto error; 163 } 164 note_start = (Elf_Addr)(note_map + phdr->p_offset - 165 trunc_page(phdr->p_offset)); 166 } else { 167 note_start = (Elf_Addr)(char *)hdr + phdr->p_offset; 168 } 169 note_end = note_start + phdr->p_filesz; 170 break; 171 } 172 173 ++phdr; 174 } 175 if (phdyn == NULL) { 176 _rtld_error("%s: object is not dynamically-linked", path); 177 goto error; 178 } 179 180 if (nsegs < 0) { 181 _rtld_error("%s: too few PT_LOAD segments", path); 182 goto error; 183 } 184 185 /* 186 * Map the entire address space of the object, to stake out our 187 * contiguous region, and to establish the base address for relocation. 188 */ 189 base_vaddr = trunc_page(segs[0]->p_vaddr); 190 base_vlimit = round_page(segs[nsegs]->p_vaddr + segs[nsegs]->p_memsz); 191 mapsize = base_vlimit - base_vaddr; 192 base_addr = (caddr_t) base_vaddr; 193 base_flags = MAP_PRIVATE | MAP_ANON | MAP_NOCORE; 194 if (npagesizes > 1 && round_page(segs[0]->p_filesz) >= pagesizes[1]) 195 base_flags |= MAP_ALIGNED_SUPER; 196 197 mapbase = mmap(base_addr, mapsize, PROT_NONE, base_flags, -1, 0); 198 if (mapbase == (caddr_t) -1) { 199 _rtld_error("%s: mmap of entire address space failed: %s", 200 path, rtld_strerror(errno)); 201 goto error; 202 } 203 if (base_addr != NULL && mapbase != base_addr) { 204 _rtld_error("%s: mmap returned wrong address: wanted %p, got %p", 205 path, base_addr, mapbase); 206 goto error1; 207 } 208 209 for (i = 0; i <= nsegs; i++) { 210 /* Overlay the segment onto the proper region. */ 211 data_offset = trunc_page(segs[i]->p_offset); 212 data_vaddr = trunc_page(segs[i]->p_vaddr); 213 data_vlimit = round_page(segs[i]->p_vaddr + segs[i]->p_filesz); 214 data_addr = mapbase + (data_vaddr - base_vaddr); 215 data_prot = convert_prot(segs[i]->p_flags); 216 data_flags = convert_flags(segs[i]->p_flags) | MAP_FIXED; 217 if (mmap(data_addr, data_vlimit - data_vaddr, data_prot, 218 data_flags | MAP_PREFAULT_READ, fd, data_offset) == (caddr_t) -1) { 219 _rtld_error("%s: mmap of data failed: %s", path, 220 rtld_strerror(errno)); 221 goto error1; 222 } 223 224 /* Do BSS setup */ 225 if (segs[i]->p_filesz != segs[i]->p_memsz) { 226 227 /* Clear any BSS in the last page of the segment. */ 228 clear_vaddr = segs[i]->p_vaddr + segs[i]->p_filesz; 229 clear_addr = mapbase + (clear_vaddr - base_vaddr); 230 clear_page = mapbase + (trunc_page(clear_vaddr) - base_vaddr); 231 232 if ((nclear = data_vlimit - clear_vaddr) > 0) { 233 /* Make sure the end of the segment is writable */ 234 if ((data_prot & PROT_WRITE) == 0 && -1 == 235 mprotect(clear_page, PAGE_SIZE, data_prot|PROT_WRITE)) { 236 _rtld_error("%s: mprotect failed: %s", path, 237 rtld_strerror(errno)); 238 goto error1; 239 } 240 241 memset(clear_addr, 0, nclear); 242 243 /* Reset the data protection back */ 244 if ((data_prot & PROT_WRITE) == 0) 245 mprotect(clear_page, PAGE_SIZE, data_prot); 246 } 247 248 /* Overlay the BSS segment onto the proper region. */ 249 bss_vaddr = data_vlimit; 250 bss_vlimit = round_page(segs[i]->p_vaddr + segs[i]->p_memsz); 251 bss_addr = mapbase + (bss_vaddr - base_vaddr); 252 if (bss_vlimit > bss_vaddr) { /* There is something to do */ 253 if (mmap(bss_addr, bss_vlimit - bss_vaddr, data_prot, 254 data_flags | MAP_ANON, -1, 0) == (caddr_t)-1) { 255 _rtld_error("%s: mmap of bss failed: %s", path, 256 rtld_strerror(errno)); 257 goto error1; 258 } 259 } 260 } 261 262 if (phdr_vaddr == 0 && data_offset <= hdr->e_phoff && 263 (data_vlimit - data_vaddr + data_offset) >= 264 (hdr->e_phoff + hdr->e_phnum * sizeof (Elf_Phdr))) { 265 phdr_vaddr = data_vaddr + hdr->e_phoff - data_offset; 266 } 267 } 268 269 obj = obj_new(); 270 if (sb != NULL) { 271 obj->dev = sb->st_dev; 272 obj->ino = sb->st_ino; 273 } 274 obj->mapbase = mapbase; 275 obj->mapsize = mapsize; 276 obj->textsize = round_page(segs[0]->p_vaddr + segs[0]->p_memsz) - 277 base_vaddr; 278 obj->vaddrbase = base_vaddr; 279 obj->relocbase = mapbase - base_vaddr; 280 obj->dynamic = (const Elf_Dyn *) (obj->relocbase + phdyn->p_vaddr); 281 if (hdr->e_entry != 0) 282 obj->entry = (caddr_t) (obj->relocbase + hdr->e_entry); 283 if (phdr_vaddr != 0) { 284 obj->phdr = (const Elf_Phdr *) (obj->relocbase + phdr_vaddr); 285 } else { 286 obj->phdr = malloc(phsize); 287 if (obj->phdr == NULL) { 288 obj_free(obj); 289 _rtld_error("%s: cannot allocate program header", path); 290 goto error1; 291 } 292 memcpy((char *)obj->phdr, (char *)hdr + hdr->e_phoff, phsize); 293 obj->phdr_alloc = true; 294 } 295 obj->phsize = phsize; 296 if (phinterp != NULL) 297 obj->interp = (const char *) (obj->relocbase + phinterp->p_vaddr); 298 if (phtls != NULL) { 299 tls_dtv_generation++; 300 obj->tlsindex = ++tls_max_index; 301 obj->tlssize = phtls->p_memsz; 302 obj->tlsalign = phtls->p_align; 303 obj->tlsinitsize = phtls->p_filesz; 304 obj->tlsinit = mapbase + phtls->p_vaddr; 305 } 306 obj->stack_flags = stack_flags; 307 obj->relro_page = obj->relocbase + trunc_page(relro_page); 308 obj->relro_size = round_page(relro_size); 309 if (note_start < note_end) 310 digest_notes(obj, note_start, note_end); 311 if (note_map != NULL) 312 munmap(note_map, note_map_len); 313 munmap(hdr, PAGE_SIZE); 314 return (obj); 315 316error1: 317 munmap(mapbase, mapsize); 318error: 319 if (note_map != NULL && note_map != MAP_FAILED) 320 munmap(note_map, note_map_len); 321 munmap(hdr, PAGE_SIZE); 322 return (NULL); 323} 324 325static Elf_Ehdr * 326get_elf_header(int fd, const char *path) 327{ 328 Elf_Ehdr *hdr; 329 330 hdr = mmap(NULL, PAGE_SIZE, PROT_READ, MAP_PRIVATE | MAP_PREFAULT_READ, 331 fd, 0); 332 if (hdr == (Elf_Ehdr *)MAP_FAILED) { 333 _rtld_error("%s: read error: %s", path, rtld_strerror(errno)); 334 return (NULL); 335 } 336 337 /* Make sure the file is valid */ 338 if (!IS_ELF(*hdr)) { 339 _rtld_error("%s: invalid file format", path); 340 goto error; 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 goto error; 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 goto error; 351 } 352 if (hdr->e_type != ET_EXEC && hdr->e_type != ET_DYN) { 353 _rtld_error("%s: unsupported file type", path); 354 goto error; 355 } 356 if (hdr->e_machine != ELF_TARG_MACH) { 357 _rtld_error("%s: unsupported machine", path); 358 goto error; 359 } 360 361 /* 362 * We rely on the program header being in the first page. This is 363 * not strictly required by the ABI specification, but it seems to 364 * always true in practice. And, it simplifies things considerably. 365 */ 366 if (hdr->e_phentsize != sizeof(Elf_Phdr)) { 367 _rtld_error( 368 "%s: invalid shared object: e_phentsize != sizeof(Elf_Phdr)", path); 369 goto error; 370 } 371 if (hdr->e_phoff + hdr->e_phnum * sizeof(Elf_Phdr) > 372 (size_t)PAGE_SIZE) { 373 _rtld_error("%s: program header too large", path); 374 goto error; 375 } 376 return (hdr); 377 378error: 379 munmap(hdr, PAGE_SIZE); 380 return (NULL); 381} 382 383void 384obj_free(Obj_Entry *obj) 385{ 386 Objlist_Entry *elm; 387 388 if (obj->tls_done) 389 free_tls_offset(obj); 390 while (obj->needed != NULL) { 391 Needed_Entry *needed = obj->needed; 392 obj->needed = needed->next; 393 free(needed); 394 } 395 while (!STAILQ_EMPTY(&obj->names)) { 396 Name_Entry *entry = STAILQ_FIRST(&obj->names); 397 STAILQ_REMOVE_HEAD(&obj->names, link); 398 free(entry); 399 } 400 while (!STAILQ_EMPTY(&obj->dldags)) { 401 elm = STAILQ_FIRST(&obj->dldags); 402 STAILQ_REMOVE_HEAD(&obj->dldags, link); 403 free(elm); 404 } 405 while (!STAILQ_EMPTY(&obj->dagmembers)) { 406 elm = STAILQ_FIRST(&obj->dagmembers); 407 STAILQ_REMOVE_HEAD(&obj->dagmembers, link); 408 free(elm); 409 } 410 if (obj->vertab) 411 free(obj->vertab); 412 if (obj->origin_path) 413 free(obj->origin_path); 414 if (obj->z_origin) 415 free(obj->rpath); 416 if (obj->priv) 417 free(obj->priv); 418 if (obj->path) 419 free(obj->path); 420 if (obj->phdr_alloc) 421 free((void *)obj->phdr); 422 free(obj); 423} 424 425Obj_Entry * 426obj_new(void) 427{ 428 Obj_Entry *obj; 429 430 obj = CNEW(Obj_Entry); 431 STAILQ_INIT(&obj->dldags); 432 STAILQ_INIT(&obj->dagmembers); 433 STAILQ_INIT(&obj->names); 434 return obj; 435} 436 437/* 438 * Given a set of ELF protection flags, return the corresponding protection 439 * flags for MMAP. 440 */ 441int 442convert_prot(int elfflags) 443{ 444 int prot = 0; 445 if (elfflags & PF_R) 446 prot |= PROT_READ; 447 if (elfflags & PF_W) 448 prot |= PROT_WRITE; 449 if (elfflags & PF_X) 450 prot |= PROT_EXEC; 451 return prot; 452} 453 454static int 455convert_flags(int elfflags) 456{ 457 int flags = MAP_PRIVATE; /* All mappings are private */ 458 459 /* 460 * Readonly mappings are marked "MAP_NOCORE", because they can be 461 * reconstructed by a debugger. 462 */ 463 if (!(elfflags & PF_W)) 464 flags |= MAP_NOCORE; 465 return flags; 466} 467