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, rtld_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, 208 rtld_strerror(errno)); 209 return NULL; 210 } 211 212 /* Do BSS setup */ 213 if (segs[i]->p_filesz != segs[i]->p_memsz) { 214 215 /* Clear any BSS in the last page of the segment. */ 216 clear_vaddr = segs[i]->p_vaddr + segs[i]->p_filesz; 217 clear_addr = mapbase + (clear_vaddr - base_vaddr); 218 clear_page = mapbase + (trunc_page(clear_vaddr) - base_vaddr); 219 220 if ((nclear = data_vlimit - clear_vaddr) > 0) { 221 /* Make sure the end of the segment is writable */ 222 if ((data_prot & PROT_WRITE) == 0 && -1 == 223 mprotect(clear_page, PAGE_SIZE, data_prot|PROT_WRITE)) { 224 _rtld_error("%s: mprotect failed: %s", path, 225 rtld_strerror(errno)); 226 return NULL; 227 } 228 229 memset(clear_addr, 0, nclear); 230 231 /* Reset the data protection back */ 232 if ((data_prot & PROT_WRITE) == 0) 233 mprotect(clear_page, PAGE_SIZE, data_prot); 234 } 235 236 /* Overlay the BSS segment onto the proper region. */ 237 bss_vaddr = data_vlimit; 238 bss_vlimit = round_page(segs[i]->p_vaddr + segs[i]->p_memsz); 239 bss_addr = mapbase + (bss_vaddr - base_vaddr); 240 if (bss_vlimit > bss_vaddr) { /* There is something to do */ 241 if (mmap(bss_addr, bss_vlimit - bss_vaddr, data_prot, 242 data_flags | MAP_ANON, -1, 0) == (caddr_t)-1) { 243 _rtld_error("%s: mmap of bss failed: %s", path, 244 rtld_strerror(errno)); 245 return NULL; 246 } 247 } 248 } 249 250 if (phdr_vaddr == 0 && data_offset <= hdr->e_phoff && 251 (data_vlimit - data_vaddr + data_offset) >= 252 (hdr->e_phoff + hdr->e_phnum * sizeof (Elf_Phdr))) { 253 phdr_vaddr = data_vaddr + hdr->e_phoff - data_offset; 254 } 255 } 256 257 obj = obj_new(); 258 if (sb != NULL) { 259 obj->dev = sb->st_dev; 260 obj->ino = sb->st_ino; 261 } 262 obj->mapbase = mapbase; 263 obj->mapsize = mapsize; 264 obj->textsize = round_page(segs[0]->p_vaddr + segs[0]->p_memsz) - 265 base_vaddr; 266 obj->vaddrbase = base_vaddr; 267 obj->relocbase = mapbase - base_vaddr; 268 obj->dynamic = (const Elf_Dyn *) (obj->relocbase + phdyn->p_vaddr); 269 if (hdr->e_entry != 0) 270 obj->entry = (caddr_t) (obj->relocbase + hdr->e_entry); 271 if (phdr_vaddr != 0) { 272 obj->phdr = (const Elf_Phdr *) (obj->relocbase + phdr_vaddr); 273 } else { 274 obj->phdr = malloc(phsize); 275 if (obj->phdr == NULL) { 276 obj_free(obj); 277 _rtld_error("%s: cannot allocate program header", path); 278 return NULL; 279 } 280 memcpy((char *)obj->phdr, (char *)hdr + hdr->e_phoff, phsize); 281 obj->phdr_alloc = true; 282 } 283 obj->phsize = phsize; 284 if (phinterp != NULL) 285 obj->interp = (const char *) (obj->relocbase + phinterp->p_vaddr); 286 if (phtls != NULL) { 287 tls_dtv_generation++; 288 obj->tlsindex = ++tls_max_index; 289 obj->tlssize = phtls->p_memsz; 290 obj->tlsalign = phtls->p_align; 291 obj->tlsinitsize = phtls->p_filesz; 292 obj->tlsinit = mapbase + phtls->p_vaddr; 293 } 294 obj->stack_flags = stack_flags; 295 obj->relro_page = obj->relocbase + trunc_page(relro_page); 296 obj->relro_size = round_page(relro_size); 297 298 return obj; 299 } 300 301 static Elf_Ehdr * 302 get_elf_header (int fd, const char *path) 303 { 304 static union { 305 Elf_Ehdr hdr; 306 char buf[PAGE_SIZE]; 307 } u; 308 ssize_t nbytes; 309 310 if ((nbytes = pread(fd, u.buf, PAGE_SIZE, 0)) == -1) { 311 _rtld_error("%s: read error: %s", path, rtld_strerror(errno)); 312 return NULL; 313 } 314 315 /* Make sure the file is valid */ 316 if (nbytes < (ssize_t)sizeof(Elf_Ehdr) || !IS_ELF(u.hdr)) { 317 _rtld_error("%s: invalid file format", path); 318 return NULL; 319 } 320 if (u.hdr.e_ident[EI_CLASS] != ELF_TARG_CLASS 321 || u.hdr.e_ident[EI_DATA] != ELF_TARG_DATA) { 322 _rtld_error("%s: unsupported file layout", path); 323 return NULL; 324 } 325 if (u.hdr.e_ident[EI_VERSION] != EV_CURRENT 326 || u.hdr.e_version != EV_CURRENT) { 327 _rtld_error("%s: unsupported file version", path); 328 return NULL; 329 } 330 if (u.hdr.e_type != ET_EXEC && u.hdr.e_type != ET_DYN) { 331 _rtld_error("%s: unsupported file type", path); 332 return NULL; 333 } 334 if (u.hdr.e_machine != ELF_TARG_MACH) { 335 _rtld_error("%s: unsupported machine", path); 336 return NULL; 337 } 338 339 /* 340 * We rely on the program header being in the first page. This is 341 * not strictly required by the ABI specification, but it seems to 342 * always true in practice. And, it simplifies things considerably. 343 */ 344 if (u.hdr.e_phentsize != sizeof(Elf_Phdr)) { 345 _rtld_error( 346 "%s: invalid shared object: e_phentsize != sizeof(Elf_Phdr)", path); 347 return NULL; 348 } 349 if (u.hdr.e_phoff + u.hdr.e_phnum * sizeof(Elf_Phdr) > (size_t)nbytes) { 350 _rtld_error("%s: program header too large", path); 351 return NULL; 352 } 353 354 return (&u.hdr); 355 } 356 357 void 358 obj_free(Obj_Entry *obj) 359 { 360 Objlist_Entry *elm; 361 362 if (obj->tls_done) 363 free_tls_offset(obj); 364 while (obj->needed != NULL) { 365 Needed_Entry *needed = obj->needed; 366 obj->needed = needed->next; 367 free(needed); 368 } 369 while (!STAILQ_EMPTY(&obj->names)) { 370 Name_Entry *entry = STAILQ_FIRST(&obj->names); 371 STAILQ_REMOVE_HEAD(&obj->names, link); 372 free(entry); 373 } 374 while (!STAILQ_EMPTY(&obj->dldags)) { 375 elm = STAILQ_FIRST(&obj->dldags); 376 STAILQ_REMOVE_HEAD(&obj->dldags, link); 377 free(elm); 378 } 379 while (!STAILQ_EMPTY(&obj->dagmembers)) { 380 elm = STAILQ_FIRST(&obj->dagmembers); 381 STAILQ_REMOVE_HEAD(&obj->dagmembers, link); 382 free(elm); 383 } 384 if (obj->vertab) 385 free(obj->vertab); 386 if (obj->origin_path) 387 free(obj->origin_path); 388 if (obj->z_origin) 389 free(obj->rpath); 390 if (obj->priv) 391 free(obj->priv); 392 if (obj->path) 393 free(obj->path); 394 if (obj->phdr_alloc) 395 free((void *)obj->phdr); 396 free(obj); 397 } 398 399 Obj_Entry * 400 obj_new(void) 401 { 402 Obj_Entry *obj; 403 404 obj = CNEW(Obj_Entry); 405 STAILQ_INIT(&obj->dldags); 406 STAILQ_INIT(&obj->dagmembers); 407 STAILQ_INIT(&obj->names); 408 return obj; 409 } 410 411 /* 412 * Given a set of ELF protection flags, return the corresponding protection 413 * flags for MMAP. 414 */ 415 static int 416 convert_prot(int elfflags) 417 { 418 int prot = 0; 419 if (elfflags & PF_R) 420 prot |= PROT_READ; 421 if (elfflags & PF_W) 422 prot |= PROT_WRITE; 423 if (elfflags & PF_X) 424 prot |= PROT_EXEC; 425 return prot; 426 } 427 428 static int 429 convert_flags(int elfflags) 430 { 431 int flags = MAP_PRIVATE; /* All mappings are private */ 432 433 /* 434 * Readonly mappings are marked "MAP_NOCORE", because they can be 435 * reconstructed by a debugger. 436 */ 437 if (!(elfflags & PF_W)) 438 flags |= MAP_NOCORE; 439 return flags; 440 } 441