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: src/libexec/rtld-elf/map_object.c,v 1.25 2011/01/25 21:12:31 kib Exp $ 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_Addr relro_page; 87 size_t relro_size; 88 89 hdr = get_elf_header(fd, path); 90 if (hdr == NULL) 91 return (NULL); 92 93 /* 94 * Scan the program header entries, and save key information. 95 * 96 * We expect that the loadable segments are ordered by load address. 97 */ 98 phdr = (Elf_Phdr *) ((char *)hdr + hdr->e_phoff); 99 phsize = hdr->e_phnum * sizeof (phdr[0]); 100 phlimit = phdr + hdr->e_phnum; 101 nsegs = -1; 102 phdyn = phinterp = phtls = NULL; 103 phdr_vaddr = 0; 104 relro_page = 0; 105 relro_size = 0; 106 segs = alloca(sizeof(segs[0]) * hdr->e_phnum); 107 while (phdr < phlimit) { 108 switch (phdr->p_type) { 109 110 case PT_INTERP: 111 phinterp = phdr; 112 break; 113 114 case PT_LOAD: 115 segs[++nsegs] = phdr; 116 if ((segs[nsegs]->p_align & (PAGE_SIZE - 1)) != 0) { 117 _rtld_error("%s: PT_LOAD segment %d not page-aligned", 118 path, nsegs); 119 return NULL; 120 } 121 break; 122 123 case PT_PHDR: 124 phdr_vaddr = phdr->p_vaddr; 125 phsize = phdr->p_memsz; 126 break; 127 128 case PT_DYNAMIC: 129 phdyn = phdr; 130 break; 131 132 case PT_TLS: 133 phtls = phdr; 134 break; 135 136 case PT_GNU_RELRO: 137 relro_page = phdr->p_vaddr; 138 relro_size = phdr->p_memsz; 139 break; 140 } 141 142 ++phdr; 143 } 144 if (phdyn == NULL) { 145 _rtld_error("%s: object is not dynamically-linked", path); 146 return NULL; 147 } 148 149 if (nsegs < 0) { 150 _rtld_error("%s: too few PT_LOAD segments", path); 151 return NULL; 152 } 153 154 /* 155 * Map the entire address space of the object, to stake out our 156 * contiguous region, and to establish the base address for relocation. 157 */ 158 base_offset = trunc_page(segs[0]->p_offset); 159 base_vaddr = trunc_page(segs[0]->p_vaddr); 160 base_vlimit = round_page(segs[nsegs]->p_vaddr + segs[nsegs]->p_memsz); 161 mapsize = base_vlimit - base_vaddr; 162 base_addr = hdr->e_type == ET_EXEC ? (caddr_t) base_vaddr : NULL; 163 164 mapbase = mmap(base_addr, mapsize, PROT_NONE, MAP_ANON | MAP_PRIVATE | 165 MAP_NOCORE, -1, 0); 166 if (mapbase == (caddr_t) -1) { 167 _rtld_error("%s: mmap of entire address space failed: %s", 168 path, strerror(errno)); 169 return NULL; 170 } 171 if (base_addr != NULL && mapbase != base_addr) { 172 _rtld_error("%s: mmap returned wrong address: wanted %p, got %p", 173 path, base_addr, mapbase); 174 munmap(mapbase, mapsize); 175 return NULL; 176 } 177 178 for (i = 0; i <= nsegs; i++) { 179 /* Overlay the segment onto the proper region. */ 180 data_offset = trunc_page(segs[i]->p_offset); 181 data_vaddr = trunc_page(segs[i]->p_vaddr); 182 data_vlimit = round_page(segs[i]->p_vaddr + segs[i]->p_filesz); 183 data_addr = mapbase + (data_vaddr - base_vaddr); 184 data_prot = convert_prot(segs[i]->p_flags); 185 data_flags = convert_flags(segs[i]->p_flags) | MAP_FIXED; 186 if (mmap(data_addr, data_vlimit - data_vaddr, data_prot, 187 data_flags, fd, data_offset) == (caddr_t) -1) { 188 _rtld_error("%s: mmap of data failed: %s", path, strerror(errno)); 189 return NULL; 190 } 191 192 /* Do BSS setup */ 193 if (segs[i]->p_filesz != segs[i]->p_memsz) { 194 195 /* Clear any BSS in the last page of the segment. */ 196 clear_vaddr = segs[i]->p_vaddr + segs[i]->p_filesz; 197 clear_addr = mapbase + (clear_vaddr - base_vaddr); 198 clear_page = mapbase + (trunc_page(clear_vaddr) - base_vaddr); 199 200 if ((nclear = data_vlimit - clear_vaddr) > 0) { 201 /* Make sure the end of the segment is writable */ 202 if ((data_prot & PROT_WRITE) == 0 && -1 == 203 mprotect(clear_page, PAGE_SIZE, data_prot|PROT_WRITE)) { 204 _rtld_error("%s: mprotect failed: %s", path, 205 strerror(errno)); 206 return NULL; 207 } 208 209 memset(clear_addr, 0, nclear); 210 211 /* 212 * reset the data protection back, enable the segment to be 213 * coredumped since we modified it. 214 */ 215 if ((data_prot & PROT_WRITE) == 0) { 216 madvise(clear_page, PAGE_SIZE, MADV_CORE); 217 mprotect(clear_page, PAGE_SIZE, data_prot); 218 } 219 } 220 221 /* Overlay the BSS segment onto the proper region. */ 222 bss_vaddr = data_vlimit; 223 bss_vlimit = round_page(segs[i]->p_vaddr + segs[i]->p_memsz); 224 bss_addr = mapbase + (bss_vaddr - base_vaddr); 225 if (bss_vlimit > bss_vaddr) { /* There is something to do */ 226 if (mmap(bss_addr, bss_vlimit - bss_vaddr, data_prot, 227 data_flags | MAP_ANON, -1, 0) == (caddr_t)-1) { 228 _rtld_error("%s: mmap of bss failed: %s", path, 229 strerror(errno)); 230 return NULL; 231 } 232 } 233 } 234 235 if (phdr_vaddr == 0 && data_offset <= hdr->e_phoff && 236 (data_vlimit - data_vaddr + data_offset) >= 237 (hdr->e_phoff + hdr->e_phnum * sizeof (Elf_Phdr))) { 238 phdr_vaddr = data_vaddr + hdr->e_phoff - data_offset; 239 } 240 } 241 242 obj = obj_new(); 243 if (sb != NULL) { 244 obj->dev = sb->st_dev; 245 obj->ino = sb->st_ino; 246 } 247 obj->mapbase = mapbase; 248 obj->mapsize = mapsize; 249 obj->textsize = round_page(segs[0]->p_vaddr + segs[0]->p_memsz) - 250 base_vaddr; 251 obj->vaddrbase = base_vaddr; 252 obj->relocbase = mapbase - base_vaddr; 253 obj->dynamic = (const Elf_Dyn *) (obj->relocbase + phdyn->p_vaddr); 254 if (hdr->e_entry != 0) 255 obj->entry = (caddr_t) (obj->relocbase + hdr->e_entry); 256 if (phdr_vaddr != 0) { 257 obj->phdr = (const Elf_Phdr *) (obj->relocbase + phdr_vaddr); 258 } else { 259 obj->phdr = malloc(phsize); 260 if (obj->phdr == NULL) { 261 obj_free(obj); 262 _rtld_error("%s: cannot allocate program header", path); 263 return NULL; 264 } 265 memcpy((char *)obj->phdr, (char *)hdr + hdr->e_phoff, phsize); 266 obj->phdr_alloc = true; 267 } 268 obj->phsize = phsize; 269 if (phinterp != NULL) 270 obj->interp = (const char *) (obj->relocbase + phinterp->p_vaddr); 271 if (phtls != NULL) { 272 tls_dtv_generation++; 273 obj->tlsindex = ++tls_max_index; 274 obj->tlssize = phtls->p_memsz; 275 obj->tlsalign = phtls->p_align; 276 obj->tlsinitsize = phtls->p_filesz; 277 obj->tlsinit = mapbase + phtls->p_vaddr; 278 } 279 280 if (relro_size) { 281 obj->relro_page = obj->relocbase + trunc_page(relro_page); 282 obj->relro_size = round_page(relro_size); 283 } 284 return obj; 285 } 286 287 static Elf_Ehdr * 288 get_elf_header (int fd, const char *path) 289 { 290 static union { 291 Elf_Ehdr hdr; 292 char buf[PAGE_SIZE]; 293 } u; 294 ssize_t nbytes; 295 296 if ((nbytes = pread(fd, u.buf, PAGE_SIZE, 0)) == -1) { 297 _rtld_error("%s: read error: %s", path, strerror(errno)); 298 return NULL; 299 } 300 301 /* Make sure the file is valid */ 302 if (nbytes < (ssize_t)sizeof(Elf_Ehdr) || !IS_ELF(u.hdr)) { 303 _rtld_error("%s: invalid file format", path); 304 return NULL; 305 } 306 if (u.hdr.e_ident[EI_CLASS] != ELF_TARG_CLASS 307 || u.hdr.e_ident[EI_DATA] != ELF_TARG_DATA) { 308 _rtld_error("%s: unsupported file layout", path); 309 return NULL; 310 } 311 if (u.hdr.e_ident[EI_VERSION] != EV_CURRENT 312 || u.hdr.e_version != EV_CURRENT) { 313 _rtld_error("%s: unsupported file version", path); 314 return NULL; 315 } 316 if (u.hdr.e_type != ET_EXEC && u.hdr.e_type != ET_DYN) { 317 _rtld_error("%s: unsupported file type", path); 318 return NULL; 319 } 320 if (u.hdr.e_machine != ELF_TARG_MACH) { 321 _rtld_error("%s: unsupported machine", path); 322 return NULL; 323 } 324 325 /* 326 * We rely on the program header being in the first page. This is 327 * not strictly required by the ABI specification, but it seems to 328 * always true in practice. And, it simplifies things considerably. 329 */ 330 if (u.hdr.e_phentsize != sizeof(Elf_Phdr)) { 331 _rtld_error( 332 "%s: invalid shared object: e_phentsize != sizeof(Elf_Phdr)", path); 333 return NULL; 334 } 335 if (u.hdr.e_phoff + u.hdr.e_phnum * sizeof(Elf_Phdr) > (size_t)nbytes) { 336 _rtld_error("%s: program header too large", path); 337 return NULL; 338 } 339 340 return (&u.hdr); 341 } 342 343 void 344 obj_free(Obj_Entry *obj) 345 { 346 Objlist_Entry *elm; 347 348 if (obj->tls_done) 349 free_tls_offset(obj); 350 while (obj->needed != NULL) { 351 Needed_Entry *needed = obj->needed; 352 obj->needed = needed->next; 353 free(needed); 354 } 355 while (!STAILQ_EMPTY(&obj->names)) { 356 Name_Entry *entry = STAILQ_FIRST(&obj->names); 357 STAILQ_REMOVE_HEAD(&obj->names, link); 358 free(entry); 359 } 360 while (!STAILQ_EMPTY(&obj->dldags)) { 361 elm = STAILQ_FIRST(&obj->dldags); 362 STAILQ_REMOVE_HEAD(&obj->dldags, link); 363 free(elm); 364 } 365 while (!STAILQ_EMPTY(&obj->dagmembers)) { 366 elm = STAILQ_FIRST(&obj->dagmembers); 367 STAILQ_REMOVE_HEAD(&obj->dagmembers, link); 368 free(elm); 369 } 370 if (obj->vertab) 371 free(obj->vertab); 372 if (obj->origin_path) 373 free(obj->origin_path); 374 if (obj->z_origin) 375 free(obj->rpath); 376 if (obj->priv) 377 free(obj->priv); 378 if (obj->path) 379 free(obj->path); 380 if (obj->phdr_alloc) 381 free((void *)obj->phdr); 382 free(obj); 383 } 384 385 Obj_Entry * 386 obj_new(void) 387 { 388 Obj_Entry *obj; 389 390 obj = CNEW(Obj_Entry); 391 STAILQ_INIT(&obj->dldags); 392 STAILQ_INIT(&obj->dagmembers); 393 STAILQ_INIT(&obj->names); 394 return obj; 395 } 396 397 /* 398 * Given a set of ELF protection flags, return the corresponding protection 399 * flags for MMAP. 400 */ 401 static int 402 convert_prot(int elfflags) 403 { 404 int prot = 0; 405 if (elfflags & PF_R) 406 prot |= PROT_READ; 407 if (elfflags & PF_W) 408 prot |= PROT_WRITE; 409 if (elfflags & PF_X) 410 prot |= PROT_EXEC; 411 return prot; 412 } 413 414 static int 415 convert_flags(int elfflags) 416 { 417 int flags = MAP_PRIVATE; /* All mappings are private */ 418 419 /* 420 * Readonly mappings are marked "MAP_NOCORE", because they can be 421 * reconstructed by a debugger. 422 */ 423 if (!(elfflags & PF_W)) 424 flags |= MAP_NOCORE; 425 return flags; 426 } 427