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 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 /* Clear any BSS in the last page of the segment. */ 184 clear_vaddr = segs[i]->p_vaddr + segs[i]->p_filesz; 185 clear_addr = mapbase + (clear_vaddr - base_vaddr); 186 clear_page = mapbase + (trunc_page(clear_vaddr) - base_vaddr); 187 if ((nclear = data_vlimit - clear_vaddr) > 0) { 188 /* Make sure the end of the segment is writable */ 189 if ((data_prot & PROT_WRITE) == 0 && 190 -1 == mprotect(clear_page, PAGE_SIZE, data_prot|PROT_WRITE)) { 191 _rtld_error("%s: mprotect failed: %s", path, 192 strerror(errno)); 193 return NULL; 194 } 195 196 memset(clear_addr, 0, nclear); 197 198 /* Reset the data protection back */ 199 if ((data_prot & PROT_WRITE) == 0) 200 mprotect(clear_page, PAGE_SIZE, data_prot); 201 } 202 203 /* Overlay the BSS segment onto the proper region. */ 204 bss_vaddr = data_vlimit; 205 bss_vlimit = round_page(segs[i]->p_vaddr + segs[i]->p_memsz); 206 bss_addr = mapbase + (bss_vaddr - base_vaddr); 207 if (bss_vlimit > bss_vaddr) { /* There is something to do */ 208 if (mprotect(bss_addr, bss_vlimit - bss_vaddr, data_prot) == -1) { 209 _rtld_error("%s: mprotect of bss failed: %s", path, 210 strerror(errno)); 211 return NULL; 212 } 213 } 214 if (phdr_vaddr == 0 && data_offset <= hdr->e_phoff && 215 (data_vlimit - data_vaddr + data_offset) >= 216 (hdr->e_phoff + hdr->e_phnum * sizeof (Elf_Phdr))) { 217 phdr_vaddr = data_vaddr + hdr->e_phoff - data_offset; 218 } 219 } 220 221 obj = obj_new(); 222 if (sb != NULL) { 223 obj->dev = sb->st_dev; 224 obj->ino = sb->st_ino; 225 } 226 obj->mapbase = mapbase; 227 obj->mapsize = mapsize; 228 obj->textsize = round_page(segs[0]->p_vaddr + segs[0]->p_memsz) - 229 base_vaddr; 230 obj->vaddrbase = base_vaddr; 231 obj->relocbase = mapbase - base_vaddr; 232 obj->dynamic = (const Elf_Dyn *) (obj->relocbase + phdyn->p_vaddr); 233 if (hdr->e_entry != 0) 234 obj->entry = (caddr_t) (obj->relocbase + hdr->e_entry); 235 if (phdr_vaddr != 0) { 236 obj->phdr = (const Elf_Phdr *) (obj->relocbase + phdr_vaddr); 237 } else { 238 obj->phdr = malloc(phsize); 239 if (obj->phdr == NULL) { 240 obj_free(obj); 241 _rtld_error("%s: cannot allocate program header", path); 242 return NULL; 243 } 244 memcpy((char *)obj->phdr, (char *)hdr + hdr->e_phoff, phsize); 245 obj->phdr_alloc = true; 246 } 247 obj->phsize = phsize; 248 if (phinterp != NULL) 249 obj->interp = (const char *) (obj->relocbase + phinterp->p_vaddr); 250 if (phtls != NULL) { 251 tls_dtv_generation++; 252 obj->tlsindex = ++tls_max_index; 253 obj->tlssize = phtls->p_memsz; 254 obj->tlsalign = phtls->p_align; 255 obj->tlsinitsize = phtls->p_filesz; 256 obj->tlsinit = mapbase + phtls->p_vaddr; 257 } 258 return obj; 259 } 260 261 static Elf_Ehdr * 262 get_elf_header (int fd, const char *path) 263 { 264 static union { 265 Elf_Ehdr hdr; 266 char buf[PAGE_SIZE]; 267 } u; 268 ssize_t nbytes; 269 270 if ((nbytes = read(fd, u.buf, PAGE_SIZE)) == -1) { 271 _rtld_error("%s: read error: %s", path, strerror(errno)); 272 return NULL; 273 } 274 275 /* Make sure the file is valid */ 276 if (nbytes < (ssize_t)sizeof(Elf_Ehdr) || !IS_ELF(u.hdr)) { 277 _rtld_error("%s: invalid file format", path); 278 return NULL; 279 } 280 if (u.hdr.e_ident[EI_CLASS] != ELF_TARG_CLASS 281 || u.hdr.e_ident[EI_DATA] != ELF_TARG_DATA) { 282 _rtld_error("%s: unsupported file layout", path); 283 return NULL; 284 } 285 if (u.hdr.e_ident[EI_VERSION] != EV_CURRENT 286 || u.hdr.e_version != EV_CURRENT) { 287 _rtld_error("%s: unsupported file version", path); 288 return NULL; 289 } 290 if (u.hdr.e_type != ET_EXEC && u.hdr.e_type != ET_DYN) { 291 _rtld_error("%s: unsupported file type", path); 292 return NULL; 293 } 294 if (u.hdr.e_machine != ELF_TARG_MACH) { 295 _rtld_error("%s: unsupported machine", path); 296 return NULL; 297 } 298 299 /* 300 * We rely on the program header being in the first page. This is 301 * not strictly required by the ABI specification, but it seems to 302 * always true in practice. And, it simplifies things considerably. 303 */ 304 if (u.hdr.e_phentsize != sizeof(Elf_Phdr)) { 305 _rtld_error( 306 "%s: invalid shared object: e_phentsize != sizeof(Elf_Phdr)", path); 307 return NULL; 308 } 309 if (u.hdr.e_phoff + u.hdr.e_phnum * sizeof(Elf_Phdr) > (size_t)nbytes) { 310 _rtld_error("%s: program header too large", path); 311 return NULL; 312 } 313 314 return (&u.hdr); 315 } 316 317 void 318 obj_free(Obj_Entry *obj) 319 { 320 Objlist_Entry *elm; 321 322 if (obj->tls_done) 323 free_tls_offset(obj); 324 while (obj->needed != NULL) { 325 Needed_Entry *needed = obj->needed; 326 obj->needed = needed->next; 327 free(needed); 328 } 329 while (!STAILQ_EMPTY(&obj->names)) { 330 Name_Entry *entry = STAILQ_FIRST(&obj->names); 331 STAILQ_REMOVE_HEAD(&obj->names, link); 332 free(entry); 333 } 334 while (!STAILQ_EMPTY(&obj->dldags)) { 335 elm = STAILQ_FIRST(&obj->dldags); 336 STAILQ_REMOVE_HEAD(&obj->dldags, link); 337 free(elm); 338 } 339 while (!STAILQ_EMPTY(&obj->dagmembers)) { 340 elm = STAILQ_FIRST(&obj->dagmembers); 341 STAILQ_REMOVE_HEAD(&obj->dagmembers, link); 342 free(elm); 343 } 344 if (obj->vertab) 345 free(obj->vertab); 346 if (obj->origin_path) 347 free(obj->origin_path); 348 if (obj->z_origin) 349 free(obj->rpath); 350 if (obj->priv) 351 free(obj->priv); 352 if (obj->path) 353 free(obj->path); 354 if (obj->phdr_alloc) 355 free((void *)obj->phdr); 356 free(obj); 357 } 358 359 Obj_Entry * 360 obj_new(void) 361 { 362 Obj_Entry *obj; 363 364 obj = CNEW(Obj_Entry); 365 STAILQ_INIT(&obj->dldags); 366 STAILQ_INIT(&obj->dagmembers); 367 STAILQ_INIT(&obj->names); 368 return obj; 369 } 370 371 /* 372 * Given a set of ELF protection flags, return the corresponding protection 373 * flags for MMAP. 374 */ 375 static int 376 convert_prot(int elfflags) 377 { 378 int prot = 0; 379 if (elfflags & PF_R) 380 prot |= PROT_READ; 381 if (elfflags & PF_W) 382 prot |= PROT_WRITE; 383 if (elfflags & PF_X) 384 prot |= PROT_EXEC; 385 return prot; 386 } 387 388 static int 389 convert_flags(int elfflags) 390 { 391 int flags = MAP_PRIVATE; /* All mappings are private */ 392 393 /* 394 * Readonly mappings are marked "MAP_NOCORE", because they can be 395 * reconstructed by a debugger. 396 */ 397 if (!(elfflags & PF_W)) 398 flags |= MAP_NOCORE; 399 return flags; 400 } 401