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