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