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 break; 157 } 158 159 ++phdr; 160 } 161 if (phdyn == NULL) { 162 _rtld_error("%s: object is not dynamically-linked", path); 163 return NULL; 164 } 165 166 if (nsegs < 0) { 167 _rtld_error("%s: too few PT_LOAD segments", path); 168 return NULL; 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 = hdr->e_type == ET_EXEC ? (caddr_t) base_vaddr : NULL; 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 return NULL; 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 munmap(mapbase, mapsize); 191 return NULL; 192 } 193 194 for (i = 0; i <= nsegs; i++) { 195 /* Overlay the segment onto the proper region. */ 196 data_offset = trunc_page(segs[i]->p_offset); 197 data_vaddr = trunc_page(segs[i]->p_vaddr); 198 data_vlimit = round_page(segs[i]->p_vaddr + segs[i]->p_filesz); 199 data_addr = mapbase + (data_vaddr - base_vaddr); 200 data_prot = convert_prot(segs[i]->p_flags); 201 data_flags = convert_flags(segs[i]->p_flags) | MAP_FIXED; 202 if (mmap(data_addr, data_vlimit - data_vaddr, data_prot, 203 data_flags, fd, data_offset) == (caddr_t) -1) { 204 _rtld_error("%s: mmap of data failed: %s", path, 205 rtld_strerror(errno)); 206 return NULL; 207 } 208 209 /* Do BSS setup */ 210 if (segs[i]->p_filesz != segs[i]->p_memsz) { 211 212 /* Clear any BSS in the last page of the segment. */ 213 clear_vaddr = segs[i]->p_vaddr + segs[i]->p_filesz; 214 clear_addr = mapbase + (clear_vaddr - base_vaddr); 215 clear_page = mapbase + (trunc_page(clear_vaddr) - base_vaddr); 216 217 if ((nclear = data_vlimit - clear_vaddr) > 0) { 218 /* Make sure the end of the segment is writable */ 219 if ((data_prot & PROT_WRITE) == 0 && -1 == 220 mprotect(clear_page, PAGE_SIZE, data_prot|PROT_WRITE)) { 221 _rtld_error("%s: mprotect failed: %s", path, 222 rtld_strerror(errno)); 223 return NULL; 224 } 225 226 memset(clear_addr, 0, nclear); 227 228 /* 229 * reset the data protection back, enable the segment to be 230 * coredumped since we modified it. 231 */ 232 if ((data_prot & PROT_WRITE) == 0) { 233 madvise(clear_page, PAGE_SIZE, MADV_CORE); 234 mprotect(clear_page, PAGE_SIZE, data_prot); 235 } 236 } 237 238 /* Overlay the BSS segment onto the proper region. */ 239 bss_vaddr = data_vlimit; 240 bss_vlimit = round_page(segs[i]->p_vaddr + segs[i]->p_memsz); 241 bss_addr = mapbase + (bss_vaddr - base_vaddr); 242 if (bss_vlimit > bss_vaddr) { /* There is something to do */ 243 if (mmap(bss_addr, bss_vlimit - bss_vaddr, data_prot, 244 data_flags | MAP_ANON, -1, 0) == (caddr_t)-1) { 245 _rtld_error("%s: mmap of bss failed: %s", path, 246 rtld_strerror(errno)); 247 return NULL; 248 } 249 } 250 } 251 252 if (phdr_vaddr == 0 && data_offset <= hdr->e_phoff && 253 (data_vlimit - data_vaddr + data_offset) >= 254 (hdr->e_phoff + hdr->e_phnum * sizeof (Elf_Phdr))) { 255 phdr_vaddr = data_vaddr + hdr->e_phoff - data_offset; 256 } 257 } 258 259 obj = obj_new(); 260 if (sb != NULL) { 261 obj->dev = sb->st_dev; 262 obj->ino = sb->st_ino; 263 } 264 obj->mapbase = mapbase; 265 obj->mapsize = mapsize; 266 obj->textsize = round_page(segs[0]->p_vaddr + segs[0]->p_memsz) - 267 base_vaddr; 268 obj->vaddrbase = base_vaddr; 269 obj->relocbase = mapbase - base_vaddr; 270 obj->dynamic = (const Elf_Dyn *) (obj->relocbase + phdyn->p_vaddr); 271 if (hdr->e_entry != 0) 272 obj->entry = (caddr_t) (obj->relocbase + hdr->e_entry); 273 if (phdr_vaddr != 0) { 274 obj->phdr = (const Elf_Phdr *) (obj->relocbase + phdr_vaddr); 275 } else { 276 obj->phdr = malloc(phsize); 277 if (obj->phdr == NULL) { 278 obj_free(obj); 279 _rtld_error("%s: cannot allocate program header", path); 280 return NULL; 281 } 282 memcpy((char *)obj->phdr, (char *)hdr + hdr->e_phoff, phsize); 283 obj->phdr_alloc = true; 284 } 285 obj->phsize = phsize; 286 if (phinterp != NULL) 287 obj->interp = (const char *) (obj->relocbase + phinterp->p_vaddr); 288 if (phtls != NULL) { 289 tls_dtv_generation++; 290 obj->tlsindex = ++tls_max_index; 291 obj->tlssize = phtls->p_memsz; 292 obj->tlsalign = phtls->p_align; 293 obj->tlsinitsize = phtls->p_filesz; 294 obj->tlsinit = mapbase + phtls->p_vaddr; 295 } 296 obj->stack_flags = stack_flags; 297 if (relro_size) { 298 obj->relro_page = obj->relocbase + trunc_page(relro_page); 299 obj->relro_size = round_page(relro_size); 300 } 301 if (note_start < note_end) 302 digest_notes(obj, note_start, note_end); 303 return obj; 304 } 305 306 static Elf_Ehdr * 307 get_elf_header (int fd, const char *path) 308 { 309 static union { 310 Elf_Ehdr hdr; 311 char buf[PAGE_SIZE]; 312 } u; 313 ssize_t nbytes; 314 315 if ((nbytes = pread(fd, u.buf, PAGE_SIZE, 0)) == -1) { 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 (nbytes < (ssize_t)sizeof(Elf_Ehdr) || !IS_ELF(u.hdr)) { 322 _rtld_error("%s: invalid file format", path); 323 return NULL; 324 } 325 if (u.hdr.e_ident[EI_CLASS] != ELF_TARG_CLASS 326 || u.hdr.e_ident[EI_DATA] != ELF_TARG_DATA) { 327 _rtld_error("%s: unsupported file layout", path); 328 return NULL; 329 } 330 if (u.hdr.e_ident[EI_VERSION] != EV_CURRENT 331 || u.hdr.e_version != EV_CURRENT) { 332 _rtld_error("%s: unsupported file version", path); 333 return NULL; 334 } 335 if (u.hdr.e_type != ET_EXEC && u.hdr.e_type != ET_DYN) { 336 _rtld_error("%s: unsupported file type", path); 337 return NULL; 338 } 339 if (u.hdr.e_machine != ELF_TARG_MACH) { 340 _rtld_error("%s: unsupported machine", path); 341 return NULL; 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 (u.hdr.e_phentsize != sizeof(Elf_Phdr)) { 350 _rtld_error( 351 "%s: invalid shared object: e_phentsize != sizeof(Elf_Phdr)", path); 352 return NULL; 353 } 354 if (u.hdr.e_phoff + u.hdr.e_phnum * sizeof(Elf_Phdr) > (size_t)nbytes) { 355 _rtld_error("%s: program header too large", path); 356 return NULL; 357 } 358 359 return (&u.hdr); 360 } 361 362 void 363 obj_free(Obj_Entry *obj) 364 { 365 Objlist_Entry *elm; 366 367 if (obj->tls_done) 368 free_tls_offset(obj); 369 while (obj->needed != NULL) { 370 Needed_Entry *needed = obj->needed; 371 obj->needed = needed->next; 372 free(needed); 373 } 374 while (!STAILQ_EMPTY(&obj->names)) { 375 Name_Entry *entry = STAILQ_FIRST(&obj->names); 376 STAILQ_REMOVE_HEAD(&obj->names, link); 377 free(entry); 378 } 379 while (!STAILQ_EMPTY(&obj->dldags)) { 380 elm = STAILQ_FIRST(&obj->dldags); 381 STAILQ_REMOVE_HEAD(&obj->dldags, link); 382 free(elm); 383 } 384 while (!STAILQ_EMPTY(&obj->dagmembers)) { 385 elm = STAILQ_FIRST(&obj->dagmembers); 386 STAILQ_REMOVE_HEAD(&obj->dagmembers, link); 387 free(elm); 388 } 389 if (obj->vertab) 390 free(obj->vertab); 391 if (obj->origin_path) 392 free(obj->origin_path); 393 if (obj->z_origin) 394 free(obj->rpath); 395 if (obj->priv) 396 free(obj->priv); 397 if (obj->path) 398 free(obj->path); 399 if (obj->phdr_alloc) 400 free((void *)obj->phdr); 401 free(obj); 402 } 403 404 Obj_Entry * 405 obj_new(void) 406 { 407 Obj_Entry *obj; 408 409 obj = CNEW(Obj_Entry); 410 STAILQ_INIT(&obj->dldags); 411 STAILQ_INIT(&obj->dagmembers); 412 STAILQ_INIT(&obj->names); 413 return obj; 414 } 415 416 /* 417 * Given a set of ELF protection flags, return the corresponding protection 418 * flags for MMAP. 419 */ 420 static int 421 convert_prot(int elfflags) 422 { 423 int prot = 0; 424 if (elfflags & PF_R) 425 prot |= PROT_READ; 426 if (elfflags & PF_W) 427 prot |= PROT_WRITE; 428 if (elfflags & PF_X) 429 prot |= PROT_EXEC; 430 return prot; 431 } 432 433 static int 434 convert_flags(int elfflags) 435 { 436 int flags = MAP_PRIVATE; /* All mappings are private */ 437 438 /* 439 * Readonly mappings are marked "MAP_NOCORE", because they can be 440 * reconstructed by a debugger. 441 */ 442 if (!(elfflags & PF_W)) 443 flags |= MAP_NOCORE; 444 return flags; 445 } 446