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