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_Off base_offset; 69 Elf_Addr base_vaddr; 70 Elf_Addr base_vlimit; 71 caddr_t base_addr; 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 return NULL; 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 digest_notes(obj, note_start, note_end); 158 break; 159 } 160 161 ++phdr; 162 } 163 if (phdyn == NULL) { 164 _rtld_error("%s: object is not dynamically-linked", path); 165 return NULL; 166 } 167 168 if (nsegs < 0) { 169 _rtld_error("%s: too few PT_LOAD segments", path); 170 return NULL; 171 } 172 173 /* 174 * Map the entire address space of the object, to stake out our 175 * contiguous region, and to establish the base address for relocation. 176 */ 177 base_offset = trunc_page(segs[0]->p_offset); 178 base_vaddr = trunc_page(segs[0]->p_vaddr); 179 base_vlimit = round_page(segs[nsegs]->p_vaddr + segs[nsegs]->p_memsz); 180 mapsize = base_vlimit - base_vaddr; 181 base_addr = hdr->e_type == ET_EXEC ? (caddr_t) base_vaddr : NULL; 182 183 mapbase = mmap(base_addr, mapsize, PROT_NONE, MAP_ANON | MAP_PRIVATE | 184 MAP_NOCORE, -1, 0); 185 if (mapbase == (caddr_t) -1) { 186 _rtld_error("%s: mmap of entire address space failed: %s", 187 path, strerror(errno)); 188 return NULL; 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 munmap(mapbase, mapsize); 194 return NULL; 195 } 196 197 for (i = 0; i <= nsegs; i++) { 198 /* Overlay the segment onto the proper region. */ 199 data_offset = trunc_page(segs[i]->p_offset); 200 data_vaddr = trunc_page(segs[i]->p_vaddr); 201 data_vlimit = round_page(segs[i]->p_vaddr + segs[i]->p_filesz); 202 data_addr = mapbase + (data_vaddr - base_vaddr); 203 data_prot = convert_prot(segs[i]->p_flags); 204 data_flags = convert_flags(segs[i]->p_flags) | MAP_FIXED; 205 if (mmap(data_addr, data_vlimit - data_vaddr, data_prot, 206 data_flags, fd, data_offset) == (caddr_t) -1) { 207 _rtld_error("%s: mmap of data failed: %s", path, strerror(errno)); 208 return NULL; 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 strerror(errno)); 225 return NULL; 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 strerror(errno)); 244 return NULL; 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 return NULL; 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); 296 297 return obj; 298 } 299 300 static Elf_Ehdr * 301 get_elf_header (int fd, const char *path) 302 { 303 static union { 304 Elf_Ehdr hdr; 305 char buf[PAGE_SIZE]; 306 } u; 307 ssize_t nbytes; 308 309 if ((nbytes = pread(fd, u.buf, PAGE_SIZE, 0)) == -1) { 310 _rtld_error("%s: read error: %s", path, strerror(errno)); 311 return NULL; 312 } 313 314 /* Make sure the file is valid */ 315 if (nbytes < (ssize_t)sizeof(Elf_Ehdr) || !IS_ELF(u.hdr)) { 316 _rtld_error("%s: invalid file format", path); 317 return NULL; 318 } 319 if (u.hdr.e_ident[EI_CLASS] != ELF_TARG_CLASS 320 || u.hdr.e_ident[EI_DATA] != ELF_TARG_DATA) { 321 _rtld_error("%s: unsupported file layout", path); 322 return NULL; 323 } 324 if (u.hdr.e_ident[EI_VERSION] != EV_CURRENT 325 || u.hdr.e_version != EV_CURRENT) { 326 _rtld_error("%s: unsupported file version", path); 327 return NULL; 328 } 329 if (u.hdr.e_type != ET_EXEC && u.hdr.e_type != ET_DYN) { 330 _rtld_error("%s: unsupported file type", path); 331 return NULL; 332 } 333 if (u.hdr.e_machine != ELF_TARG_MACH) { 334 _rtld_error("%s: unsupported machine", path); 335 return NULL; 336 } 337 338 /* 339 * We rely on the program header being in the first page. This is 340 * not strictly required by the ABI specification, but it seems to 341 * always true in practice. And, it simplifies things considerably. 342 */ 343 if (u.hdr.e_phentsize != sizeof(Elf_Phdr)) { 344 _rtld_error( 345 "%s: invalid shared object: e_phentsize != sizeof(Elf_Phdr)", path); 346 return NULL; 347 } 348 if (u.hdr.e_phoff + u.hdr.e_phnum * sizeof(Elf_Phdr) > (size_t)nbytes) { 349 _rtld_error("%s: program header too large", path); 350 return NULL; 351 } 352 353 return (&u.hdr); 354 } 355 356 void 357 obj_free(Obj_Entry *obj) 358 { 359 Objlist_Entry *elm; 360 361 if (obj->tls_done) 362 free_tls_offset(obj); 363 while (obj->needed != NULL) { 364 Needed_Entry *needed = obj->needed; 365 obj->needed = needed->next; 366 free(needed); 367 } 368 while (!STAILQ_EMPTY(&obj->names)) { 369 Name_Entry *entry = STAILQ_FIRST(&obj->names); 370 STAILQ_REMOVE_HEAD(&obj->names, link); 371 free(entry); 372 } 373 while (!STAILQ_EMPTY(&obj->dldags)) { 374 elm = STAILQ_FIRST(&obj->dldags); 375 STAILQ_REMOVE_HEAD(&obj->dldags, link); 376 free(elm); 377 } 378 while (!STAILQ_EMPTY(&obj->dagmembers)) { 379 elm = STAILQ_FIRST(&obj->dagmembers); 380 STAILQ_REMOVE_HEAD(&obj->dagmembers, link); 381 free(elm); 382 } 383 if (obj->vertab) 384 free(obj->vertab); 385 if (obj->origin_path) 386 free(obj->origin_path); 387 if (obj->z_origin) 388 free(obj->rpath); 389 if (obj->priv) 390 free(obj->priv); 391 if (obj->path) 392 free(obj->path); 393 if (obj->phdr_alloc) 394 free((void *)obj->phdr); 395 free(obj); 396 } 397 398 Obj_Entry * 399 obj_new(void) 400 { 401 Obj_Entry *obj; 402 403 obj = CNEW(Obj_Entry); 404 STAILQ_INIT(&obj->dldags); 405 STAILQ_INIT(&obj->dagmembers); 406 STAILQ_INIT(&obj->names); 407 return obj; 408 } 409 410 /* 411 * Given a set of ELF protection flags, return the corresponding protection 412 * flags for MMAP. 413 */ 414 static int 415 convert_prot(int elfflags) 416 { 417 int prot = 0; 418 if (elfflags & PF_R) 419 prot |= PROT_READ; 420 if (elfflags & PF_W) 421 prot |= PROT_WRITE; 422 if (elfflags & PF_X) 423 prot |= PROT_EXEC; 424 return prot; 425 } 426 427 static int 428 convert_flags(int elfflags) 429 { 430 int flags = MAP_PRIVATE; /* All mappings are private */ 431 432 /* 433 * Readonly mappings are marked "MAP_NOCORE", because they can be 434 * reconstructed by a debugger. 435 */ 436 if (!(elfflags & PF_W)) 437 flags |= MAP_NOCORE; 438 return flags; 439 } 440