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 *); 42 static int convert_prot(int); /* Elf flags -> mmap protection */ 43 static int convert_flags(int); /* Elf flags -> mmap flags */ 44 45 /* 46 * Map a shared object into memory. The "fd" argument is a file descriptor, 47 * which must be open on the object and positioned at its beginning. 48 * The "path" argument is a pathname that is used only for error messages. 49 * 50 * The return value is a pointer to a newly-allocated Obj_Entry structure 51 * for the shared object. Returns NULL on failure. 52 */ 53 Obj_Entry * 54 map_object(int fd, const char *path, const struct stat *sb) 55 { 56 Obj_Entry *obj; 57 Elf_Ehdr *hdr; 58 int i; 59 Elf_Phdr *phdr; 60 Elf_Phdr *phlimit; 61 Elf_Phdr **segs; 62 int nsegs; 63 Elf_Phdr *phdyn; 64 Elf_Phdr *phinterp; 65 Elf_Phdr *phtls; 66 caddr_t mapbase; 67 size_t mapsize; 68 Elf_Addr base_vaddr; 69 Elf_Addr base_vlimit; 70 caddr_t base_addr; 71 int base_flags; 72 Elf_Off data_offset; 73 Elf_Addr data_vaddr; 74 Elf_Addr data_vlimit; 75 caddr_t data_addr; 76 int data_prot; 77 int data_flags; 78 Elf_Addr clear_vaddr; 79 caddr_t clear_addr; 80 caddr_t clear_page; 81 Elf_Addr phdr_vaddr; 82 size_t nclear, phsize; 83 Elf_Addr bss_vaddr; 84 Elf_Addr bss_vlimit; 85 caddr_t bss_addr; 86 Elf_Word stack_flags; 87 Elf_Addr relro_page; 88 size_t relro_size; 89 Elf_Addr note_start; 90 Elf_Addr note_end; 91 92 hdr = get_elf_header(fd, path); 93 if (hdr == NULL) 94 return (NULL); 95 96 /* 97 * Scan the program header entries, and save key information. 98 * 99 * We expect that the loadable segments are ordered by load address. 100 */ 101 phdr = (Elf_Phdr *) ((char *)hdr + hdr->e_phoff); 102 phsize = hdr->e_phnum * sizeof (phdr[0]); 103 phlimit = phdr + hdr->e_phnum; 104 nsegs = -1; 105 phdyn = phinterp = phtls = NULL; 106 phdr_vaddr = 0; 107 relro_page = 0; 108 relro_size = 0; 109 note_start = 0; 110 note_end = 0; 111 segs = alloca(sizeof(segs[0]) * hdr->e_phnum); 112 stack_flags = RTLD_DEFAULT_STACK_PF_EXEC | PF_R | PF_W; 113 while (phdr < phlimit) { 114 switch (phdr->p_type) { 115 116 case PT_INTERP: 117 phinterp = phdr; 118 break; 119 120 case PT_LOAD: 121 segs[++nsegs] = phdr; 122 if ((segs[nsegs]->p_align & (PAGE_SIZE - 1)) != 0) { 123 _rtld_error("%s: PT_LOAD segment %d not page-aligned", 124 path, nsegs); 125 goto error; 126 } 127 break; 128 129 case PT_PHDR: 130 phdr_vaddr = phdr->p_vaddr; 131 phsize = phdr->p_memsz; 132 break; 133 134 case PT_DYNAMIC: 135 phdyn = phdr; 136 break; 137 138 case PT_TLS: 139 phtls = phdr; 140 break; 141 142 case PT_GNU_STACK: 143 stack_flags = phdr->p_flags; 144 break; 145 146 case PT_GNU_RELRO: 147 relro_page = phdr->p_vaddr; 148 relro_size = phdr->p_memsz; 149 break; 150 151 case PT_NOTE: 152 if (phdr->p_offset > PAGE_SIZE || 153 phdr->p_offset + phdr->p_filesz > PAGE_SIZE) 154 break; 155 note_start = (Elf_Addr)(char *)hdr + phdr->p_offset; 156 note_end = note_start + phdr->p_filesz; 157 break; 158 } 159 160 ++phdr; 161 } 162 if (phdyn == NULL) { 163 _rtld_error("%s: object is not dynamically-linked", path); 164 goto error; 165 } 166 167 if (nsegs < 0) { 168 _rtld_error("%s: too few PT_LOAD segments", path); 169 goto error; 170 } 171 172 /* 173 * Map the entire address space of the object, to stake out our 174 * contiguous region, and to establish the base address for relocation. 175 */ 176 base_vaddr = trunc_page(segs[0]->p_vaddr); 177 base_vlimit = round_page(segs[nsegs]->p_vaddr + segs[nsegs]->p_memsz); 178 mapsize = base_vlimit - base_vaddr; 179 base_addr = (caddr_t) base_vaddr; 180 base_flags = MAP_PRIVATE | MAP_ANON | MAP_NOCORE; 181 if (npagesizes > 1 && round_page(segs[0]->p_filesz) >= pagesizes[1]) 182 base_flags |= MAP_ALIGNED_SUPER; 183 184 mapbase = mmap(base_addr, mapsize, PROT_NONE, base_flags, -1, 0); 185 if (mapbase == (caddr_t) -1) { 186 _rtld_error("%s: mmap of entire address space failed: %s", 187 path, rtld_strerror(errno)); 188 goto error; 189 } 190 if (base_addr != NULL && mapbase != base_addr) { 191 _rtld_error("%s: mmap returned wrong address: wanted %p, got %p", 192 path, base_addr, mapbase); 193 goto error1; 194 } 195 196 for (i = 0; i <= nsegs; i++) { 197 /* Overlay the segment onto the proper region. */ 198 data_offset = trunc_page(segs[i]->p_offset); 199 data_vaddr = trunc_page(segs[i]->p_vaddr); 200 data_vlimit = round_page(segs[i]->p_vaddr + segs[i]->p_filesz); 201 data_addr = mapbase + (data_vaddr - base_vaddr); 202 data_prot = convert_prot(segs[i]->p_flags); 203 data_flags = convert_flags(segs[i]->p_flags) | MAP_FIXED; 204 if (mmap(data_addr, data_vlimit - data_vaddr, data_prot, 205 data_flags | MAP_PREFAULT_READ, fd, data_offset) == (caddr_t) -1) { 206 _rtld_error("%s: mmap of data failed: %s", path, 207 rtld_strerror(errno)); 208 goto error1; 209 } 210 211 /* Do BSS setup */ 212 if (segs[i]->p_filesz != segs[i]->p_memsz) { 213 214 /* Clear any BSS in the last page of the segment. */ 215 clear_vaddr = segs[i]->p_vaddr + segs[i]->p_filesz; 216 clear_addr = mapbase + (clear_vaddr - base_vaddr); 217 clear_page = mapbase + (trunc_page(clear_vaddr) - base_vaddr); 218 219 if ((nclear = data_vlimit - clear_vaddr) > 0) { 220 /* Make sure the end of the segment is writable */ 221 if ((data_prot & PROT_WRITE) == 0 && -1 == 222 mprotect(clear_page, PAGE_SIZE, data_prot|PROT_WRITE)) { 223 _rtld_error("%s: mprotect failed: %s", path, 224 rtld_strerror(errno)); 225 goto error1; 226 } 227 228 memset(clear_addr, 0, nclear); 229 230 /* Reset the data protection back */ 231 if ((data_prot & PROT_WRITE) == 0) 232 mprotect(clear_page, PAGE_SIZE, data_prot); 233 } 234 235 /* Overlay the BSS segment onto the proper region. */ 236 bss_vaddr = data_vlimit; 237 bss_vlimit = round_page(segs[i]->p_vaddr + segs[i]->p_memsz); 238 bss_addr = mapbase + (bss_vaddr - base_vaddr); 239 if (bss_vlimit > bss_vaddr) { /* There is something to do */ 240 if (mmap(bss_addr, bss_vlimit - bss_vaddr, data_prot, 241 data_flags | MAP_ANON, -1, 0) == (caddr_t)-1) { 242 _rtld_error("%s: mmap of bss failed: %s", path, 243 rtld_strerror(errno)); 244 goto error1; 245 } 246 } 247 } 248 249 if (phdr_vaddr == 0 && data_offset <= hdr->e_phoff && 250 (data_vlimit - data_vaddr + data_offset) >= 251 (hdr->e_phoff + hdr->e_phnum * sizeof (Elf_Phdr))) { 252 phdr_vaddr = data_vaddr + hdr->e_phoff - data_offset; 253 } 254 } 255 256 obj = obj_new(); 257 if (sb != NULL) { 258 obj->dev = sb->st_dev; 259 obj->ino = sb->st_ino; 260 } 261 obj->mapbase = mapbase; 262 obj->mapsize = mapsize; 263 obj->textsize = round_page(segs[0]->p_vaddr + segs[0]->p_memsz) - 264 base_vaddr; 265 obj->vaddrbase = base_vaddr; 266 obj->relocbase = mapbase - base_vaddr; 267 obj->dynamic = (const Elf_Dyn *) (obj->relocbase + phdyn->p_vaddr); 268 if (hdr->e_entry != 0) 269 obj->entry = (caddr_t) (obj->relocbase + hdr->e_entry); 270 if (phdr_vaddr != 0) { 271 obj->phdr = (const Elf_Phdr *) (obj->relocbase + phdr_vaddr); 272 } else { 273 obj->phdr = malloc(phsize); 274 if (obj->phdr == NULL) { 275 obj_free(obj); 276 _rtld_error("%s: cannot allocate program header", path); 277 goto error1; 278 } 279 memcpy((char *)obj->phdr, (char *)hdr + hdr->e_phoff, phsize); 280 obj->phdr_alloc = true; 281 } 282 obj->phsize = phsize; 283 if (phinterp != NULL) 284 obj->interp = (const char *) (obj->relocbase + phinterp->p_vaddr); 285 if (phtls != NULL) { 286 tls_dtv_generation++; 287 obj->tlsindex = ++tls_max_index; 288 obj->tlssize = phtls->p_memsz; 289 obj->tlsalign = phtls->p_align; 290 obj->tlsinitsize = phtls->p_filesz; 291 obj->tlsinit = mapbase + phtls->p_vaddr; 292 } 293 obj->stack_flags = stack_flags; 294 obj->relro_page = obj->relocbase + trunc_page(relro_page); 295 obj->relro_size = round_page(relro_size); 296 if (note_start < note_end) 297 digest_notes(obj, note_start, note_end); 298 munmap(hdr, PAGE_SIZE); 299 return (obj); 300 301 error1: 302 munmap(mapbase, mapsize); 303 error: 304 munmap(hdr, PAGE_SIZE); 305 return (NULL); 306 } 307 308 static Elf_Ehdr * 309 get_elf_header(int fd, const char *path) 310 { 311 Elf_Ehdr *hdr; 312 313 hdr = mmap(NULL, PAGE_SIZE, PROT_READ, MAP_PRIVATE | MAP_PREFAULT_READ, 314 fd, 0); 315 if (hdr == (Elf_Ehdr *)MAP_FAILED) { 316 _rtld_error("%s: read error: %s", path, rtld_strerror(errno)); 317 return (NULL); 318 } 319 320 /* Make sure the file is valid */ 321 if (!IS_ELF(*hdr)) { 322 _rtld_error("%s: invalid file format", path); 323 goto error; 324 } 325 if (hdr->e_ident[EI_CLASS] != ELF_TARG_CLASS || 326 hdr->e_ident[EI_DATA] != ELF_TARG_DATA) { 327 _rtld_error("%s: unsupported file layout", path); 328 goto error; 329 } 330 if (hdr->e_ident[EI_VERSION] != EV_CURRENT || 331 hdr->e_version != EV_CURRENT) { 332 _rtld_error("%s: unsupported file version", path); 333 goto error; 334 } 335 if (hdr->e_type != ET_EXEC && hdr->e_type != ET_DYN) { 336 _rtld_error("%s: unsupported file type", path); 337 goto error; 338 } 339 if (hdr->e_machine != ELF_TARG_MACH) { 340 _rtld_error("%s: unsupported machine", path); 341 goto error; 342 } 343 344 /* 345 * We rely on the program header being in the first page. This is 346 * not strictly required by the ABI specification, but it seems to 347 * always true in practice. And, it simplifies things considerably. 348 */ 349 if (hdr->e_phentsize != sizeof(Elf_Phdr)) { 350 _rtld_error( 351 "%s: invalid shared object: e_phentsize != sizeof(Elf_Phdr)", path); 352 goto error; 353 } 354 if (hdr->e_phoff + hdr->e_phnum * sizeof(Elf_Phdr) > 355 (size_t)PAGE_SIZE) { 356 _rtld_error("%s: program header too large", path); 357 goto error; 358 } 359 return (hdr); 360 361 error: 362 munmap(hdr, PAGE_SIZE); 363 return (NULL); 364 } 365 366 void 367 obj_free(Obj_Entry *obj) 368 { 369 Objlist_Entry *elm; 370 371 if (obj->tls_done) 372 free_tls_offset(obj); 373 while (obj->needed != NULL) { 374 Needed_Entry *needed = obj->needed; 375 obj->needed = needed->next; 376 free(needed); 377 } 378 while (!STAILQ_EMPTY(&obj->names)) { 379 Name_Entry *entry = STAILQ_FIRST(&obj->names); 380 STAILQ_REMOVE_HEAD(&obj->names, link); 381 free(entry); 382 } 383 while (!STAILQ_EMPTY(&obj->dldags)) { 384 elm = STAILQ_FIRST(&obj->dldags); 385 STAILQ_REMOVE_HEAD(&obj->dldags, link); 386 free(elm); 387 } 388 while (!STAILQ_EMPTY(&obj->dagmembers)) { 389 elm = STAILQ_FIRST(&obj->dagmembers); 390 STAILQ_REMOVE_HEAD(&obj->dagmembers, link); 391 free(elm); 392 } 393 if (obj->vertab) 394 free(obj->vertab); 395 if (obj->origin_path) 396 free(obj->origin_path); 397 if (obj->z_origin) 398 free(obj->rpath); 399 if (obj->priv) 400 free(obj->priv); 401 if (obj->path) 402 free(obj->path); 403 if (obj->phdr_alloc) 404 free((void *)obj->phdr); 405 free(obj); 406 } 407 408 Obj_Entry * 409 obj_new(void) 410 { 411 Obj_Entry *obj; 412 413 obj = CNEW(Obj_Entry); 414 STAILQ_INIT(&obj->dldags); 415 STAILQ_INIT(&obj->dagmembers); 416 STAILQ_INIT(&obj->names); 417 return obj; 418 } 419 420 /* 421 * Given a set of ELF protection flags, return the corresponding protection 422 * flags for MMAP. 423 */ 424 static int 425 convert_prot(int elfflags) 426 { 427 int prot = 0; 428 if (elfflags & PF_R) 429 prot |= PROT_READ; 430 if (elfflags & PF_W) 431 prot |= PROT_WRITE; 432 if (elfflags & PF_X) 433 prot |= PROT_EXEC; 434 return prot; 435 } 436 437 static int 438 convert_flags(int elfflags) 439 { 440 int flags = MAP_PRIVATE; /* All mappings are private */ 441 442 /* 443 * Readonly mappings are marked "MAP_NOCORE", because they can be 444 * reconstructed by a debugger. 445 */ 446 if (!(elfflags & PF_W)) 447 flags |= MAP_NOCORE; 448 return flags; 449 } 450