map_object.c revision 1.49
1 /* $NetBSD: map_object.c,v 1.49 2013/05/06 19:59:30 christos Exp $ */ 2 3 /* 4 * Copyright 1996 John D. Polstra. 5 * Copyright 1996 Matt Thomas <matt (at) 3am-software.com> 6 * Copyright 2002 Charles M. Hannum <root (at) 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 1.49 2013/05/06 19:59:30 christos 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: not ELF file (too short)", 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 _rtld_error("%s: not ELF file (magic number bad)", path); 130 goto bad; 131 } 132 if (ehdr->e_ident[EI_CLASS] != ELFCLASS) { 133 _rtld_error("%s: invalid ELF class %x; expected %x", path, 134 ehdr->e_ident[EI_CLASS], ELFCLASS); 135 goto bad; 136 } 137 /* Elf_e_ident includes class */ 138 if (ehdr->e_ident[EI_VERSION] != EV_CURRENT || 139 ehdr->e_version != EV_CURRENT || 140 ehdr->e_ident[EI_DATA] != ELFDEFNNAME(MACHDEP_ENDIANNESS)) { 141 _rtld_error("%s: unsupported file version", path); 142 goto bad; 143 } 144 if (ehdr->e_type != ET_EXEC && ehdr->e_type != ET_DYN) { 145 _rtld_error("%s: unsupported file type", path); 146 goto bad; 147 } 148 switch (ehdr->e_machine) { 149 ELFDEFNNAME(MACHDEP_ID_CASES) 150 default: 151 _rtld_error("%s: unsupported machine", path); 152 goto bad; 153 } 154 155 /* 156 * We rely on the program header being in the first page. This is 157 * not strictly required by the ABI specification, but it seems to 158 * always true in practice. And, it simplifies things considerably. 159 */ 160 assert(ehdr->e_phentsize == sizeof(Elf_Phdr)); 161 assert(ehdr->e_phoff + ehdr->e_phnum * sizeof(Elf_Phdr) <= 162 _rtld_pagesz); 163 164 /* 165 * Scan the program header entries, and save key information. 166 * 167 * We rely on there being exactly two load segments, text and data, 168 * in that order. 169 */ 170 phdr = (Elf_Phdr *) ((caddr_t)ehdr + ehdr->e_phoff); 171 #if defined(__HAVE_TLS_VARIANT_I) || defined(__HAVE_TLS_VARIANT_II) 172 phtls = NULL; 173 #endif 174 phsize = ehdr->e_phnum * sizeof(phdr[0]); 175 obj->phdr = NULL; 176 phdr_vaddr = EA_UNDEF; 177 phdr_memsz = 0; 178 phlimit = phdr + ehdr->e_phnum; 179 nsegs = 0; 180 while (phdr < phlimit) { 181 switch (phdr->p_type) { 182 case PT_INTERP: 183 obj->interp = (void *)(uintptr_t)phdr->p_vaddr; 184 dbg(("%s: PT_INTERP %p", obj->path, obj->interp)); 185 break; 186 187 case PT_LOAD: 188 if (nsegs < 2) 189 segs[nsegs] = phdr; 190 ++nsegs; 191 192 #if ELFSIZE == 64 193 #define PRImemsz PRIu64 194 #else 195 #define PRImemsz PRIu32 196 #endif 197 dbg(("%s: %s %p phsize %" PRImemsz, obj->path, "PT_LOAD", 198 (void *)(uintptr_t)phdr->p_vaddr, phdr->p_memsz)); 199 break; 200 201 case PT_PHDR: 202 phdr_vaddr = phdr->p_vaddr; 203 phdr_memsz = phdr->p_memsz; 204 dbg(("%s: %s %p phsize %" PRImemsz, obj->path, "PT_PHDR", 205 (void *)(uintptr_t)phdr->p_vaddr, phdr->p_memsz)); 206 break; 207 208 case PT_DYNAMIC: 209 obj->dynamic = (void *)(uintptr_t)phdr->p_vaddr; 210 dbg(("%s: %s %p phsize %" PRImemsz, obj->path, "PT_DYNAMIC", 211 (void *)(uintptr_t)phdr->p_vaddr, phdr->p_memsz)); 212 break; 213 214 #if defined(__HAVE_TLS_VARIANT_I) || defined(__HAVE_TLS_VARIANT_II) 215 case PT_TLS: 216 phtls = phdr; 217 dbg(("%s: %s %p phsize %" PRImemsz, obj->path, "PT_TLS", 218 (void *)(uintptr_t)phdr->p_vaddr, phdr->p_memsz)); 219 break; 220 #endif 221 #ifdef __ARM_EABI__ 222 case PT_ARM_EXIDX: 223 obj->exidx_start = (void *)(uintptr_t)phdr->p_vaddr; 224 obj->exidx_sz = phdr->p_memsz; 225 break; 226 #endif 227 } 228 229 ++phdr; 230 } 231 phdr = (Elf_Phdr *) ((caddr_t)ehdr + ehdr->e_phoff); 232 obj->entry = (void *)(uintptr_t)ehdr->e_entry; 233 if (!obj->dynamic) { 234 _rtld_error("%s: not dynamically linked", path); 235 goto bad; 236 } 237 if (nsegs != 2) { 238 _rtld_error("%s: wrong number of segments (%d != 2)", path, 239 nsegs); 240 goto bad; 241 } 242 243 /* 244 * Map the entire address space of the object as a file 245 * region to stake out our contiguous region and establish a 246 * base for relocation. We use a file mapping so that 247 * the kernel will give us whatever alignment is appropriate 248 * for the platform we're running on. 249 * 250 * We map it using the text protection, map the data segment 251 * into the right place, then map an anon segment for the bss 252 * and unmap the gaps left by padding to alignment. 253 */ 254 255 #ifdef MAP_ALIGNED 256 base_alignment = segs[0]->p_align; 257 #endif 258 base_offset = round_down(segs[0]->p_offset); 259 base_vaddr = round_down(segs[0]->p_vaddr); 260 base_vlimit = round_up(segs[1]->p_vaddr + segs[1]->p_memsz); 261 text_vlimit = round_up(segs[0]->p_vaddr + segs[0]->p_memsz); 262 text_flags = protflags(segs[0]->p_flags); 263 data_offset = round_down(segs[1]->p_offset); 264 data_vaddr = round_down(segs[1]->p_vaddr); 265 data_vlimit = round_up(segs[1]->p_vaddr + segs[1]->p_filesz); 266 data_flags = protflags(segs[1]->p_flags); 267 #ifdef RTLD_LOADER 268 clear_vaddr = segs[1]->p_vaddr + segs[1]->p_filesz; 269 #endif 270 271 obj->textsize = text_vlimit - base_vaddr; 272 obj->vaddrbase = base_vaddr; 273 obj->isdynamic = ehdr->e_type == ET_DYN; 274 275 #if defined(__HAVE_TLS_VARIANT_I) || defined(__HAVE_TLS_VARIANT_II) 276 if (phtls != NULL) { 277 ++_rtld_tls_dtv_generation; 278 obj->tlsindex = ++_rtld_tls_max_index; 279 obj->tlssize = phtls->p_memsz; 280 obj->tlsalign = phtls->p_align; 281 obj->tlsinitsize = phtls->p_filesz; 282 tls_vaddr = phtls->p_vaddr; 283 } 284 #endif 285 286 obj->phdr_loaded = false; 287 for (i = 0; i < nsegs; i++) { 288 if (phdr_vaddr != EA_UNDEF && 289 segs[i]->p_vaddr <= phdr_vaddr && 290 segs[i]->p_memsz >= phdr_memsz) { 291 obj->phdr_loaded = true; 292 break; 293 } 294 if (segs[i]->p_offset <= ehdr->e_phoff && 295 segs[i]->p_memsz >= phsize) { 296 phdr_vaddr = segs[i]->p_vaddr + ehdr->e_phoff; 297 phdr_memsz = phsize; 298 obj->phdr_loaded = true; 299 break; 300 } 301 } 302 if (obj->phdr_loaded) { 303 obj->phdr = (void *)(uintptr_t)phdr_vaddr; 304 obj->phsize = phdr_memsz; 305 } else { 306 Elf_Phdr *buf; 307 buf = xmalloc(phsize); 308 if (buf == NULL) { 309 _rtld_error("%s: cannot allocate program header", path); 310 goto bad; 311 } 312 memcpy(buf, phdr, phsize); 313 obj->phdr = buf; 314 obj->phsize = phsize; 315 } 316 dbg(("%s: phdr %p phsize %zu (%s)", obj->path, obj->phdr, obj->phsize, 317 obj->phdr_loaded ? "loaded" : "allocated")); 318 319 /* Unmap header if it overlaps the first load section. */ 320 if (base_offset < _rtld_pagesz) { 321 munmap(ehdr, _rtld_pagesz); 322 obj->ehdr = MAP_FAILED; 323 } 324 325 /* 326 * Calculate log2 of the base section alignment. 327 */ 328 mapflags = 0; 329 #ifdef MAP_ALIGNED 330 if (base_alignment > _rtld_pagesz) { 331 unsigned int log2 = 0; 332 for (; base_alignment > 1; base_alignment >>= 1) 333 log2++; 334 mapflags = MAP_ALIGNED(log2); 335 } 336 #endif 337 338 #ifdef RTLD_LOADER 339 base_addr = obj->isdynamic ? NULL : (caddr_t)base_vaddr; 340 #else 341 base_addr = NULL; 342 #endif 343 mapsize = base_vlimit - base_vaddr; 344 mapbase = mmap(base_addr, mapsize, text_flags, 345 mapflags | MAP_FILE | MAP_PRIVATE, fd, base_offset); 346 if (mapbase == MAP_FAILED) { 347 _rtld_error("mmap of entire address space failed: %s", 348 xstrerror(errno)); 349 goto bad; 350 } 351 352 /* Overlay the data segment onto the proper region. */ 353 data_addr = mapbase + (data_vaddr - base_vaddr); 354 if (mmap(data_addr, data_vlimit - data_vaddr, data_flags, 355 MAP_FILE | MAP_PRIVATE | MAP_FIXED, fd, data_offset) == 356 MAP_FAILED) { 357 _rtld_error("mmap of data failed: %s", xstrerror(errno)); 358 goto bad; 359 } 360 361 /* Overlay the bss segment onto the proper region. */ 362 if (mmap(mapbase + data_vlimit - base_vaddr, base_vlimit - data_vlimit, 363 data_flags, MAP_ANON | MAP_PRIVATE | MAP_FIXED, -1, 0) == 364 MAP_FAILED) { 365 _rtld_error("mmap of bss failed: %s", xstrerror(errno)); 366 goto bad; 367 } 368 369 /* Unmap the gap between the text and data. */ 370 gap_addr = mapbase + round_up(text_vlimit - base_vaddr); 371 gap_size = data_addr - gap_addr; 372 if (gap_size != 0 && mprotect(gap_addr, gap_size, PROT_NONE) == -1) { 373 _rtld_error("mprotect of text -> data gap failed: %s", 374 xstrerror(errno)); 375 goto bad; 376 } 377 378 #ifdef RTLD_LOADER 379 /* Clear any BSS in the last page of the data segment. */ 380 clear_addr = mapbase + (clear_vaddr - base_vaddr); 381 if ((nclear = data_vlimit - clear_vaddr) > 0) 382 memset(clear_addr, 0, nclear); 383 384 /* Non-file portion of BSS mapped above. */ 385 #endif 386 387 #if defined(__HAVE_TLS_VARIANT_I) || defined(__HAVE_TLS_VARIANT_II) 388 if (phtls != NULL) 389 obj->tlsinit = mapbase + tls_vaddr; 390 #endif 391 392 obj->mapbase = mapbase; 393 obj->mapsize = mapsize; 394 obj->relocbase = mapbase - base_vaddr; 395 396 if (obj->dynamic) 397 obj->dynamic = (void *)(obj->relocbase + (Elf_Addr)(uintptr_t)obj->dynamic); 398 if (obj->entry) 399 obj->entry = (void *)(obj->relocbase + (Elf_Addr)(uintptr_t)obj->entry); 400 if (obj->interp) 401 obj->interp = (void *)(obj->relocbase + (Elf_Addr)(uintptr_t)obj->interp); 402 if (obj->phdr_loaded) 403 obj->phdr = (void *)(obj->relocbase + (Elf_Addr)(uintptr_t)obj->phdr); 404 #ifdef __ARM_EABI__ 405 if (obj->exidx_start) 406 obj->exidx_start = (void *)(obj->relocbase + (Elf_Addr)(uintptr_t)obj->exidx_start); 407 #endif 408 409 return obj; 410 411 bad: 412 if (obj->ehdr != MAP_FAILED) 413 munmap(obj->ehdr, _rtld_pagesz); 414 if (mapbase != MAP_FAILED) 415 munmap(mapbase, mapsize); 416 _rtld_obj_free(obj); 417 return NULL; 418 } 419 420 void 421 _rtld_obj_free(Obj_Entry *obj) 422 { 423 Objlist_Entry *elm; 424 425 #if defined(__HAVE_TLS_VARIANT_I) || defined(__HAVE_TLS_VARIANT_II) 426 if (obj->tls_done) 427 _rtld_tls_offset_free(obj); 428 #endif 429 xfree(obj->path); 430 while (obj->needed != NULL) { 431 Needed_Entry *needed = obj->needed; 432 obj->needed = needed->next; 433 xfree(needed); 434 } 435 while (!STAILQ_EMPTY(&obj->names)) { 436 Name_Entry *entry = STAILQ_FIRST(&obj->names); 437 STAILQ_REMOVE_HEAD(&obj->names, link); 438 free(entry); 439 } 440 while ((elm = SIMPLEQ_FIRST(&obj->dldags)) != NULL) { 441 SIMPLEQ_REMOVE_HEAD(&obj->dldags, link); 442 xfree(elm); 443 } 444 while ((elm = SIMPLEQ_FIRST(&obj->dagmembers)) != NULL) { 445 SIMPLEQ_REMOVE_HEAD(&obj->dagmembers, link); 446 xfree(elm); 447 } 448 if (!obj->phdr_loaded) 449 xfree((void *)(uintptr_t)obj->phdr); 450 xfree(obj); 451 #ifdef COMBRELOC 452 _rtld_combreloc_reset(obj); 453 #endif 454 } 455 456 Obj_Entry * 457 _rtld_obj_new(void) 458 { 459 Obj_Entry *obj; 460 461 obj = CNEW(Obj_Entry); 462 STAILQ_INIT(&obj->names); 463 SIMPLEQ_INIT(&obj->dldags); 464 SIMPLEQ_INIT(&obj->dagmembers); 465 return obj; 466 } 467 468 /* 469 * Given a set of ELF protection flags, return the corresponding protection 470 * flags for MMAP. 471 */ 472 static int 473 protflags(int elfflags) 474 { 475 int prot = 0; 476 477 if (elfflags & PF_R) 478 prot |= PROT_READ; 479 #ifdef RTLD_LOADER 480 if (elfflags & PF_W) 481 prot |= PROT_WRITE; 482 #endif 483 if (elfflags & PF_X) 484 prot |= PROT_EXEC; 485 return prot; 486 } 487
Indexes created Wed Sep 24 05:09:52 GMT 2025