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 90 hdr = get_elf_header(fd, path); 91 if (hdr == NULL) 92 return (NULL); 93 94 /* 95 * Scan the program header entries, and save key information. 96 * 97 * We expect that the loadable segments are ordered by load address. 98 */ 99 phdr = (Elf_Phdr *) ((char *)hdr + hdr->e_phoff); 100 phsize = hdr->e_phnum * sizeof (phdr[0]); 101 phlimit = phdr + hdr->e_phnum; 102 nsegs = -1; 103 phdyn = phinterp = phtls = NULL; 104 phdr_vaddr = 0; 105 relro_page = 0; 106 relro_size = 0; 107 segs = alloca(sizeof(segs[0]) * hdr->e_phnum); 108 stack_flags = RTLD_DEFAULT_STACK_PF_EXEC | PF_R | PF_W; 109 while (phdr < phlimit) { 110 switch (phdr->p_type) { 111 112 case PT_INTERP: 113 phinterp = phdr; 114 break; 115 116 case PT_LOAD: 117 segs[++nsegs] = phdr; 118 if ((segs[nsegs]->p_align & (PAGE_SIZE - 1)) != 0) { 119 _rtld_error("%s: PT_LOAD segment %d not page-aligned", 120 path, nsegs); 121 return NULL; 122 } 123 break; 124 125 case PT_PHDR: 126 phdr_vaddr = phdr->p_vaddr; 127 phsize = phdr->p_memsz; 128 break; 129 130 case PT_DYNAMIC: 131 phdyn = phdr; 132 break; 133 134 case PT_TLS: 135 phtls = phdr; 136 break; 137 138 case PT_GNU_STACK: 139 stack_flags = phdr->p_flags; 140 break; 141 142 case PT_GNU_RELRO: 143 relro_page = phdr->p_vaddr; 144 relro_size = phdr->p_memsz; 145 break; 146 } 147 148 ++phdr; 149 } 150 if (phdyn == NULL) { 151 _rtld_error("%s: object is not dynamically-linked", path); 152 return NULL; 153 } 154 155 if (nsegs < 0) { 156 _rtld_error("%s: too few PT_LOAD segments", path); 157 return NULL; 158 } 159 160 /* 161 * Map the entire address space of the object, to stake out our 162 * contiguous region, and to establish the base address for relocation. 163 */ 164 base_offset = trunc_page(segs[0]->p_offset); 165 base_vaddr = trunc_page(segs[0]->p_vaddr); 166 base_vlimit = round_page(segs[nsegs]->p_vaddr + segs[nsegs]->p_memsz); 167 mapsize = base_vlimit - base_vaddr; 168 base_addr = hdr->e_type == ET_EXEC ? (caddr_t) base_vaddr : NULL; 169 170 mapbase = mmap(base_addr, mapsize, PROT_NONE, MAP_ANON | MAP_PRIVATE | 171 MAP_NOCORE, -1, 0); 172 if (mapbase == (caddr_t) -1) { 173 _rtld_error("%s: mmap of entire address space failed: %s", 174 path, strerror(errno)); 175 return NULL; 176 } 177 if (base_addr != NULL && mapbase != base_addr) { 178 _rtld_error("%s: mmap returned wrong address: wanted %p, got %p", 179 path, base_addr, mapbase); 180 munmap(mapbase, mapsize); 181 return NULL; 182 } 183 184 for (i = 0; i <= nsegs; i++) { 185 /* Overlay the segment onto the proper region. */ 186 data_offset = trunc_page(segs[i]->p_offset); 187 data_vaddr = trunc_page(segs[i]->p_vaddr); 188 data_vlimit = round_page(segs[i]->p_vaddr + segs[i]->p_filesz); 189 data_addr = mapbase + (data_vaddr - base_vaddr); 190 data_prot = convert_prot(segs[i]->p_flags); 191 data_flags = convert_flags(segs[i]->p_flags) | MAP_FIXED; 192 if (mmap(data_addr, data_vlimit - data_vaddr, data_prot, 193 data_flags, fd, data_offset) == (caddr_t) -1) { 194 _rtld_error("%s: mmap of data failed: %s", path, strerror(errno)); 195 return NULL; 196 } 197 198 /* Do BSS setup */ 199 if (segs[i]->p_filesz != segs[i]->p_memsz) { 200 201 /* Clear any BSS in the last page of the segment. */ 202 clear_vaddr = segs[i]->p_vaddr + segs[i]->p_filesz; 203 clear_addr = mapbase + (clear_vaddr - base_vaddr); 204 clear_page = mapbase + (trunc_page(clear_vaddr) - base_vaddr); 205 206 if ((nclear = data_vlimit - clear_vaddr) > 0) { 207 /* Make sure the end of the segment is writable */ 208 if ((data_prot & PROT_WRITE) == 0 && -1 == 209 mprotect(clear_page, PAGE_SIZE, data_prot|PROT_WRITE)) { 210 _rtld_error("%s: mprotect failed: %s", path, 211 strerror(errno)); 212 return NULL; 213 } 214 215 memset(clear_addr, 0, nclear); 216 217 /* 218 * reset the data protection back, enable the segment to be 219 * coredumped since we modified it. 220 */ 221 if ((data_prot & PROT_WRITE) == 0) { 222 madvise(clear_page, PAGE_SIZE, MADV_CORE); 223 mprotect(clear_page, PAGE_SIZE, data_prot); 224 } 225 } 226 227 /* Overlay the BSS segment onto the proper region. */ 228 bss_vaddr = data_vlimit; 229 bss_vlimit = round_page(segs[i]->p_vaddr + segs[i]->p_memsz); 230 bss_addr = mapbase + (bss_vaddr - base_vaddr); 231 if (bss_vlimit > bss_vaddr) { /* There is something to do */ 232 if (mmap(bss_addr, bss_vlimit - bss_vaddr, data_prot, 233 data_flags | MAP_ANON, -1, 0) == (caddr_t)-1) { 234 _rtld_error("%s: mmap of bss failed: %s", path, 235 strerror(errno)); 236 return NULL; 237 } 238 } 239 } 240 241 if (phdr_vaddr == 0 && data_offset <= hdr->e_phoff && 242 (data_vlimit - data_vaddr + data_offset) >= 243 (hdr->e_phoff + hdr->e_phnum * sizeof (Elf_Phdr))) { 244 phdr_vaddr = data_vaddr + hdr->e_phoff - data_offset; 245 } 246 } 247 248 obj = obj_new(); 249 if (sb != NULL) { 250 obj->dev = sb->st_dev; 251 obj->ino = sb->st_ino; 252 } 253 obj->mapbase = mapbase; 254 obj->mapsize = mapsize; 255 obj->textsize = round_page(segs[0]->p_vaddr + segs[0]->p_memsz) - 256 base_vaddr; 257 obj->vaddrbase = base_vaddr; 258 obj->relocbase = mapbase - base_vaddr; 259 obj->dynamic = (const Elf_Dyn *) (obj->relocbase + phdyn->p_vaddr); 260 if (hdr->e_entry != 0) 261 obj->entry = (caddr_t) (obj->relocbase + hdr->e_entry); 262 if (phdr_vaddr != 0) { 263 obj->phdr = (const Elf_Phdr *) (obj->relocbase + phdr_vaddr); 264 } else { 265 obj->phdr = malloc(phsize); 266 if (obj->phdr == NULL) { 267 obj_free(obj); 268 _rtld_error("%s: cannot allocate program header", path); 269 return NULL; 270 } 271 memcpy((char *)obj->phdr, (char *)hdr + hdr->e_phoff, phsize); 272 obj->phdr_alloc = true; 273 } 274 obj->phsize = phsize; 275 if (phinterp != NULL) 276 obj->interp = (const char *) (obj->relocbase + phinterp->p_vaddr); 277 if (phtls != NULL) { 278 tls_dtv_generation++; 279 obj->tlsindex = ++tls_max_index; 280 obj->tlssize = phtls->p_memsz; 281 obj->tlsalign = phtls->p_align; 282 obj->tlsinitsize = phtls->p_filesz; 283 obj->tlsinit = mapbase + phtls->p_vaddr; 284 } 285 obj->stack_flags = stack_flags; 286 if (relro_size) { 287 obj->relro_page = obj->relocbase + trunc_page(relro_page); 288 obj->relro_size = round_page(relro_size); 289 } 290 return obj; 291 } 292 293 static Elf_Ehdr * 294 get_elf_header (int fd, const char *path) 295 { 296 static union { 297 Elf_Ehdr hdr; 298 char buf[PAGE_SIZE]; 299 } u; 300 ssize_t nbytes; 301 302 if ((nbytes = pread(fd, u.buf, PAGE_SIZE, 0)) == -1) { 303 _rtld_error("%s: read error: %s", path, strerror(errno)); 304 return NULL; 305 } 306 307 /* Make sure the file is valid */ 308 if (nbytes < (ssize_t)sizeof(Elf_Ehdr) || !IS_ELF(u.hdr)) { 309 _rtld_error("%s: invalid file format", path); 310 return NULL; 311 } 312 if (u.hdr.e_ident[EI_CLASS] != ELF_TARG_CLASS 313 || u.hdr.e_ident[EI_DATA] != ELF_TARG_DATA) { 314 _rtld_error("%s: unsupported file layout", path); 315 return NULL; 316 } 317 if (u.hdr.e_ident[EI_VERSION] != EV_CURRENT 318 || u.hdr.e_version != EV_CURRENT) { 319 _rtld_error("%s: unsupported file version", path); 320 return NULL; 321 } 322 if (u.hdr.e_type != ET_EXEC && u.hdr.e_type != ET_DYN) { 323 _rtld_error("%s: unsupported file type", path); 324 return NULL; 325 } 326 if (u.hdr.e_machine != ELF_TARG_MACH) { 327 _rtld_error("%s: unsupported machine", path); 328 return NULL; 329 } 330 331 /* 332 * We rely on the program header being in the first page. This is 333 * not strictly required by the ABI specification, but it seems to 334 * always true in practice. And, it simplifies things considerably. 335 */ 336 if (u.hdr.e_phentsize != sizeof(Elf_Phdr)) { 337 _rtld_error( 338 "%s: invalid shared object: e_phentsize != sizeof(Elf_Phdr)", path); 339 return NULL; 340 } 341 if (u.hdr.e_phoff + u.hdr.e_phnum * sizeof(Elf_Phdr) > (size_t)nbytes) { 342 _rtld_error("%s: program header too large", path); 343 return NULL; 344 } 345 346 return (&u.hdr); 347 } 348 349 void 350 obj_free(Obj_Entry *obj) 351 { 352 Objlist_Entry *elm; 353 354 if (obj->tls_done) 355 free_tls_offset(obj); 356 while (obj->needed != NULL) { 357 Needed_Entry *needed = obj->needed; 358 obj->needed = needed->next; 359 free(needed); 360 } 361 while (!STAILQ_EMPTY(&obj->names)) { 362 Name_Entry *entry = STAILQ_FIRST(&obj->names); 363 STAILQ_REMOVE_HEAD(&obj->names, link); 364 free(entry); 365 } 366 while (!STAILQ_EMPTY(&obj->dldags)) { 367 elm = STAILQ_FIRST(&obj->dldags); 368 STAILQ_REMOVE_HEAD(&obj->dldags, link); 369 free(elm); 370 } 371 while (!STAILQ_EMPTY(&obj->dagmembers)) { 372 elm = STAILQ_FIRST(&obj->dagmembers); 373 STAILQ_REMOVE_HEAD(&obj->dagmembers, link); 374 free(elm); 375 } 376 if (obj->vertab) 377 free(obj->vertab); 378 if (obj->origin_path) 379 free(obj->origin_path); 380 if (obj->z_origin) 381 free(obj->rpath); 382 if (obj->priv) 383 free(obj->priv); 384 if (obj->path) 385 free(obj->path); 386 if (obj->phdr_alloc) 387 free((void *)obj->phdr); 388 free(obj); 389 } 390 391 Obj_Entry * 392 obj_new(void) 393 { 394 Obj_Entry *obj; 395 396 obj = CNEW(Obj_Entry); 397 STAILQ_INIT(&obj->dldags); 398 STAILQ_INIT(&obj->dagmembers); 399 STAILQ_INIT(&obj->names); 400 return obj; 401 } 402 403 /* 404 * Given a set of ELF protection flags, return the corresponding protection 405 * flags for MMAP. 406 */ 407 static int 408 convert_prot(int elfflags) 409 { 410 int prot = 0; 411 if (elfflags & PF_R) 412 prot |= PROT_READ; 413 if (elfflags & PF_W) 414 prot |= PROT_WRITE; 415 if (elfflags & PF_X) 416 prot |= PROT_EXEC; 417 return prot; 418 } 419 420 static int 421 convert_flags(int elfflags) 422 { 423 int flags = MAP_PRIVATE; /* All mappings are private */ 424 425 /* 426 * Readonly mappings are marked "MAP_NOCORE", because they can be 427 * reconstructed by a debugger. 428 */ 429 if (!(elfflags & PF_W)) 430 flags |= MAP_NOCORE; 431 return flags; 432 } 433