1 /* $NetBSD: map_object.c,v 1.42 2011/03/09 23:10:07 joerg Exp $ */ 2 3 /* 4 * Copyright 1996 John D. Polstra. 5 * Copyright 1996 Matt Thomas <matt@3am-software.com> 6 * Copyright 2002 Charles M. Hannum <root@ihack.net> 7 * All rights reserved. 8 * 9 * Redistribution and use in source and binary forms, with or without 10 * modification, are permitted provided that the following conditions 11 * are met: 12 * 1. Redistributions of source code must retain the above copyright 13 * notice, this list of conditions and the following disclaimer. 14 * 2. Redistributions in binary form must reproduce the above copyright 15 * notice, this list of conditions and the following disclaimer in the 16 * documentation and/or other materials provided with the distribution. 17 * 3. All advertising materials mentioning features or use of this software 18 * must display the following acknowledgement: 19 * This product includes software developed by John Polstra. 20 * 4. The name of the author may not be used to endorse or promote products 21 * derived from this software without specific prior written permission. 22 * 23 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 24 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 25 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 26 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 27 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 28 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 29 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 30 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 31 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 32 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 33 */ 34 35 #include <sys/cdefs.h> 36 #ifndef lint 37 __RCSID("$NetBSD: map_object.c,v 1.42 2011/03/09 23:10:07 joerg Exp $"); 38 #endif /* not lint */ 39 40 #include <errno.h> 41 #include <stddef.h> 42 #include <stdlib.h> 43 #include <string.h> 44 #include <unistd.h> 45 #include <sys/stat.h> 46 #include <sys/types.h> 47 #include <sys/mman.h> 48 49 #include "debug.h" 50 #include "rtld.h" 51 52 static int protflags(int); /* Elf flags -> mmap protection */ 53 54 #define EA_UNDEF (~(Elf_Addr)0) 55 56 /* 57 * Map a shared object into memory. The argument is a file descriptor, 58 * which must be open on the object and positioned at its beginning. 59 * 60 * The return value is a pointer to a newly-allocated Obj_Entry structure 61 * for the shared object. Returns NULL on failure. 62 */ 63 Obj_Entry * 64 _rtld_map_object(const char *path, int fd, const struct stat *sb) 65 { 66 Obj_Entry *obj; 67 Elf_Ehdr *ehdr; 68 Elf_Phdr *phdr; 69 #if defined(__HAVE_TLS_VARIANT_I) || defined(__HAVE_TLS_VARIANT_II) 70 Elf_Phdr *phtls; 71 #endif 72 size_t phsize; 73 Elf_Phdr *phlimit; 74 Elf_Phdr *segs[2]; 75 int nsegs; 76 caddr_t mapbase = MAP_FAILED; 77 size_t mapsize = 0; 78 int mapflags; 79 Elf_Off base_offset; 80 #ifdef MAP_ALIGNED 81 Elf_Addr base_alignment; 82 #endif 83 Elf_Addr base_vaddr; 84 Elf_Addr base_vlimit; 85 Elf_Addr text_vlimit; 86 int text_flags; 87 caddr_t base_addr; 88 Elf_Off data_offset; 89 Elf_Addr data_vaddr; 90 Elf_Addr data_vlimit; 91 int data_flags; 92 caddr_t data_addr; 93 #if defined(__HAVE_TLS_VARIANT_I) || defined(__HAVE_TLS_VARIANT_II) 94 Elf_Addr tls_vaddr = 0; /* Noise GCC */ 95 #endif 96 Elf_Addr phdr_vaddr; 97 size_t phdr_memsz; 98 caddr_t gap_addr; 99 size_t gap_size; 100 int i; 101 #ifdef RTLD_LOADER 102 Elf_Addr clear_vaddr; 103 caddr_t clear_addr; 104 size_t nclear; 105 #endif 106 107 if (sb != NULL && sb->st_size < (off_t)sizeof (Elf_Ehdr)) { 108 _rtld_error("%s: unrecognized file format1", path); 109 return NULL; 110 } 111 112 obj = _rtld_obj_new(); 113 obj->path = xstrdup(path); 114 obj->pathlen = strlen(path); 115 if (sb != NULL) { 116 obj->dev = sb->st_dev; 117 obj->ino = sb->st_ino; 118 } 119 120 ehdr = mmap(NULL, _rtld_pagesz, PROT_READ, MAP_FILE | MAP_SHARED, fd, 121 (off_t)0); 122 obj->ehdr = ehdr; 123 if (ehdr == MAP_FAILED) { 124 _rtld_error("%s: read error: %s", path, xstrerror(errno)); 125 goto bad; 126 } 127 /* Make sure the file is valid */ 128 if (memcmp(ELFMAG, ehdr->e_ident, SELFMAG) != 0 || 129 ehdr->e_ident[EI_CLASS] != ELFCLASS) { 130 _rtld_error("%s: unrecognized file format2 [%x != %x]", path, 131 ehdr->e_ident[EI_CLASS], ELFCLASS); 132 goto bad; 133 } 134 /* Elf_e_ident includes class */ 135 if (ehdr->e_ident[EI_VERSION] != EV_CURRENT || 136 ehdr->e_version != EV_CURRENT || 137 ehdr->e_ident[EI_DATA] != ELFDEFNNAME(MACHDEP_ENDIANNESS)) { 138 _rtld_error("%s: unsupported file version", path); 139 goto bad; 140 } 141 if (ehdr->e_type != ET_EXEC && ehdr->e_type != ET_DYN) { 142 _rtld_error("%s: unsupported file type", path); 143 goto bad; 144 } 145 switch (ehdr->e_machine) { 146 ELFDEFNNAME(MACHDEP_ID_CASES) 147 default: 148 _rtld_error("%s: unsupported machine", path); 149 goto bad; 150 } 151 152 /* 153 * We rely on the program header being in the first page. This is 154 * not strictly required by the ABI specification, but it seems to 155 * always true in practice. And, it simplifies things considerably. 156 */ 157 assert(ehdr->e_phentsize == sizeof(Elf_Phdr)); 158 assert(ehdr->e_phoff + ehdr->e_phnum * sizeof(Elf_Phdr) <= 159 _rtld_pagesz); 160 161 /* 162 * Scan the program header entries, and save key information. 163 * 164 * We rely on there being exactly two load segments, text and data, 165 * in that order. 166 */ 167 phdr = (Elf_Phdr *) ((caddr_t)ehdr + ehdr->e_phoff); 168 #if defined(__HAVE_TLS_VARIANT_I) || defined(__HAVE_TLS_VARIANT_II) 169 phtls = NULL; 170 #endif 171 phsize = ehdr->e_phnum * sizeof(phdr[0]); 172 obj->phdr = NULL; 173 phdr_vaddr = EA_UNDEF; 174 phdr_memsz = 0; 175 phlimit = phdr + ehdr->e_phnum; 176 nsegs = 0; 177 while (phdr < phlimit) { 178 switch (phdr->p_type) { 179 case PT_INTERP: 180 obj->interp = (void *)(uintptr_t)phdr->p_vaddr; 181 dbg(("%s: PT_INTERP %p", obj->path, obj->interp)); 182 break; 183 184 case PT_LOAD: 185 if (nsegs < 2) 186 segs[nsegs] = phdr; 187 ++nsegs; 188 dbg(("%s: PT_LOAD %p", obj->path, phdr)); 189 break; 190 191 case PT_PHDR: 192 phdr_vaddr = phdr->p_vaddr; 193 phdr_memsz = phdr->p_memsz; 194 dbg(("%s: PT_PHDR %p phsize %zu", obj->path, 195 (void *)(uintptr_t)phdr_vaddr, phdr_memsz)); 196 break; 197 198 case PT_DYNAMIC: 199 obj->dynamic = (void *)(uintptr_t)phdr->p_vaddr; 200 dbg(("%s: PT_DYNAMIC %p", obj->path, obj->dynamic)); 201 break; 202 203 #if defined(__HAVE_TLS_VARIANT_I) || defined(__HAVE_TLS_VARIANT_II) 204 case PT_TLS: 205 phtls = phdr; 206 break; 207 #endif 208 } 209 210 ++phdr; 211 } 212 phdr = (Elf_Phdr *) ((caddr_t)ehdr + ehdr->e_phoff); 213 obj->entry = (void *)(uintptr_t)ehdr->e_entry; 214 if (!obj->dynamic) { 215 _rtld_error("%s: not dynamically linked", path); 216 goto bad; 217 } 218 if (nsegs != 2) { 219 _rtld_error("%s: wrong number of segments (%d != 2)", path, 220 nsegs); 221 goto bad; 222 } 223 224 /* 225 * Map the entire address space of the object as a file 226 * region to stake out our contiguous region and establish a 227 * base for relocation. We use a file mapping so that 228 * the kernel will give us whatever alignment is appropriate 229 * for the platform we're running on. 230 * 231 * We map it using the text protection, map the data segment 232 * into the right place, then map an anon segment for the bss 233 * and unmap the gaps left by padding to alignment. 234 */ 235 236 #ifdef MAP_ALIGNED 237 base_alignment = segs[0]->p_align; 238 #endif 239 base_offset = round_down(segs[0]->p_offset); 240 base_vaddr = round_down(segs[0]->p_vaddr); 241 base_vlimit = round_up(segs[1]->p_vaddr + segs[1]->p_memsz); 242 text_vlimit = round_up(segs[0]->p_vaddr + segs[0]->p_memsz); 243 text_flags = protflags(segs[0]->p_flags); 244 data_offset = round_down(segs[1]->p_offset); 245 data_vaddr = round_down(segs[1]->p_vaddr); 246 data_vlimit = round_up(segs[1]->p_vaddr + segs[1]->p_filesz); 247 data_flags = protflags(segs[1]->p_flags); 248 #ifdef RTLD_LOADER 249 clear_vaddr = segs[1]->p_vaddr + segs[1]->p_filesz; 250 #endif 251 252 obj->textsize = text_vlimit - base_vaddr; 253 obj->vaddrbase = base_vaddr; 254 obj->isdynamic = ehdr->e_type == ET_DYN; 255 256 #if defined(__HAVE_TLS_VARIANT_I) || defined(__HAVE_TLS_VARIANT_II) 257 if (phtls != NULL) { 258 ++_rtld_tls_dtv_generation; 259 obj->tlsindex = ++_rtld_tls_max_index; 260 obj->tlssize = phtls->p_memsz; 261 obj->tlsalign = phtls->p_align; 262 obj->tlsinitsize = phtls->p_filesz; 263 tls_vaddr = phtls->p_vaddr; 264 } 265 #endif 266 267 obj->phdr_loaded = false; 268 for (i = 0; i < nsegs; i++) { 269 if (phdr_vaddr != EA_UNDEF && 270 segs[i]->p_vaddr <= phdr_vaddr && 271 segs[i]->p_memsz >= phdr_memsz) { 272 obj->phdr_loaded = true; 273 break; 274 } 275 if (segs[i]->p_offset <= ehdr->e_phoff && 276 segs[i]->p_memsz >= phsize) { 277 phdr_vaddr = segs[i]->p_vaddr + ehdr->e_phoff; 278 phdr_memsz = phsize; 279 obj->phdr_loaded = true; 280 break; 281 } 282 } 283 if (obj->phdr_loaded) { 284 obj->phdr = (void *)(uintptr_t)phdr_vaddr; 285 obj->phsize = phdr_memsz; 286 } else { 287 Elf_Phdr *buf; 288 buf = xmalloc(phsize); 289 if (buf == NULL) { 290 _rtld_error("%s: cannot allocate program header", path); 291 goto bad; 292 } 293 memcpy(buf, phdr, phsize); 294 obj->phdr = buf; 295 obj->phsize = phsize; 296 } 297 dbg(("%s: phdr %p phsize %zu (%s)", obj->path, obj->phdr, obj->phsize, 298 obj->phdr_loaded ? "loaded" : "allocated")); 299 300 /* Unmap header if it overlaps the first load section. */ 301 if (base_offset < _rtld_pagesz) { 302 munmap(ehdr, _rtld_pagesz); 303 obj->ehdr = MAP_FAILED; 304 } 305 306 /* 307 * Calculate log2 of the base section alignment. 308 */ 309 mapflags = 0; 310 #ifdef MAP_ALIGNED 311 if (base_alignment > _rtld_pagesz) { 312 unsigned int log2 = 0; 313 for (; base_alignment > 1; base_alignment >>= 1) 314 log2++; 315 mapflags = MAP_ALIGNED(log2); 316 } 317 #endif 318 319 #ifdef RTLD_LOADER 320 base_addr = obj->isdynamic ? NULL : (caddr_t)base_vaddr; 321 #else 322 base_addr = NULL; 323 #endif 324 mapsize = base_vlimit - base_vaddr; 325 mapbase = mmap(base_addr, mapsize, text_flags, 326 mapflags | MAP_FILE | MAP_PRIVATE, fd, base_offset); 327 if (mapbase == MAP_FAILED) { 328 _rtld_error("mmap of entire address space failed: %s", 329 xstrerror(errno)); 330 goto bad; 331 } 332 333 /* Overlay the data segment onto the proper region. */ 334 data_addr = mapbase + (data_vaddr - base_vaddr); 335 if (mmap(data_addr, data_vlimit - data_vaddr, data_flags, 336 MAP_FILE | MAP_PRIVATE | MAP_FIXED, fd, data_offset) == 337 MAP_FAILED) { 338 _rtld_error("mmap of data failed: %s", xstrerror(errno)); 339 goto bad; 340 } 341 342 /* Overlay the bss segment onto the proper region. */ 343 if (mmap(mapbase + data_vlimit - base_vaddr, base_vlimit - data_vlimit, 344 data_flags, MAP_ANON | MAP_PRIVATE | MAP_FIXED, -1, 0) == 345 MAP_FAILED) { 346 _rtld_error("mmap of bss failed: %s", xstrerror(errno)); 347 goto bad; 348 } 349 350 /* Unmap the gap between the text and data. */ 351 gap_addr = mapbase + round_up(text_vlimit - base_vaddr); 352 gap_size = data_addr - gap_addr; 353 if (gap_size != 0 && mprotect(gap_addr, gap_size, PROT_NONE) == -1) { 354 _rtld_error("mprotect of text -> data gap failed: %s", 355 xstrerror(errno)); 356 goto bad; 357 } 358 359 #ifdef RTLD_LOADER 360 /* Clear any BSS in the last page of the data segment. */ 361 clear_addr = mapbase + (clear_vaddr - base_vaddr); 362 if ((nclear = data_vlimit - clear_vaddr) > 0) 363 memset(clear_addr, 0, nclear); 364 365 /* Non-file portion of BSS mapped above. */ 366 #endif 367 368 #if defined(__HAVE_TLS_VARIANT_I) || defined(__HAVE_TLS_VARIANT_II) 369 if (phtls != NULL) 370 obj->tlsinit = mapbase + tls_vaddr; 371 #endif 372 373 obj->mapbase = mapbase; 374 obj->mapsize = mapsize; 375 obj->relocbase = mapbase - base_vaddr; 376 377 if (obj->dynamic) 378 obj->dynamic = (void *)(obj->relocbase + (Elf_Addr)(uintptr_t)obj->dynamic); 379 if (obj->entry) 380 obj->entry = (void *)(obj->relocbase + (Elf_Addr)(uintptr_t)obj->entry); 381 if (obj->interp) 382 obj->interp = (void *)(obj->relocbase + (Elf_Addr)(uintptr_t)obj->interp); 383 if (obj->phdr_loaded) 384 obj->phdr = (void *)(obj->relocbase + (Elf_Addr)(uintptr_t)obj->phdr); 385 386 return obj; 387 388 bad: 389 if (obj->ehdr != MAP_FAILED) 390 munmap(obj->ehdr, _rtld_pagesz); 391 if (mapbase != MAP_FAILED) 392 munmap(mapbase, mapsize); 393 _rtld_obj_free(obj); 394 return NULL; 395 } 396 397 void 398 _rtld_obj_free(Obj_Entry *obj) 399 { 400 Objlist_Entry *elm; 401 402 #if defined(__HAVE_TLS_VARIANT_I) || defined(__HAVE_TLS_VARIANT_II) 403 if (obj->tls_done) 404 _rtld_tls_offset_free(obj); 405 #endif 406 xfree(obj->path); 407 while (obj->needed != NULL) { 408 Needed_Entry *needed = obj->needed; 409 obj->needed = needed->next; 410 xfree(needed); 411 } 412 while ((elm = SIMPLEQ_FIRST(&obj->dldags)) != NULL) { 413 SIMPLEQ_REMOVE_HEAD(&obj->dldags, link); 414 xfree(elm); 415 } 416 while ((elm = SIMPLEQ_FIRST(&obj->dagmembers)) != NULL) { 417 SIMPLEQ_REMOVE_HEAD(&obj->dagmembers, link); 418 xfree(elm); 419 } 420 if (!obj->phdr_loaded) 421 xfree((void *)(uintptr_t)obj->phdr); 422 xfree(obj); 423 #ifdef COMBRELOC 424 _rtld_combreloc_reset(obj); 425 #endif 426 } 427 428 Obj_Entry * 429 _rtld_obj_new(void) 430 { 431 Obj_Entry *obj; 432 433 obj = CNEW(Obj_Entry); 434 SIMPLEQ_INIT(&obj->dldags); 435 SIMPLEQ_INIT(&obj->dagmembers); 436 return obj; 437 } 438 439 /* 440 * Given a set of ELF protection flags, return the corresponding protection 441 * flags for MMAP. 442 */ 443 static int 444 protflags(int elfflags) 445 { 446 int prot = 0; 447 448 if (elfflags & PF_R) 449 prot |= PROT_READ; 450 #ifdef RTLD_LOADER 451 if (elfflags & PF_W) 452 prot |= PROT_WRITE; 453 #endif 454 if (elfflags & PF_X) 455 prot |= PROT_EXEC; 456 return prot; 457 } 458