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