map_object.c revision 1.65
1 /* $NetBSD: map_object.c,v 1.65 2023/01/12 19:17:11 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 1.65 2023/01/12 19:17:11 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 convert_prot(int); /* Elf flags -> mmap protection */ 53 static int convert_flags(int); /* Elf flags -> mmap flags */ 54 55 #define EA_UNDEF (~(Elf_Addr)0) 56 57 /* 58 * Map a shared object into memory. The argument is a file descriptor, 59 * which must be open on the object and positioned at its beginning. 60 * 61 * The return value is a pointer to a newly-allocated Obj_Entry structure 62 * for the shared object. Returns NULL on failure. 63 */ 64 Obj_Entry * 65 _rtld_map_object(const char *path, int fd, const struct stat *sb) 66 { 67 Obj_Entry *obj; 68 Elf_Ehdr *ehdr; 69 Elf_Phdr *phdr; 70 #if defined(__HAVE_TLS_VARIANT_I) || defined(__HAVE_TLS_VARIANT_II) 71 Elf_Phdr *phtls; 72 #endif 73 Elf_Phdr *phlimit; 74 Elf_Phdr **segs = NULL; 75 int nsegs; 76 caddr_t mapbase = MAP_FAILED; 77 size_t mapsize = 0; 78 int mapflags; 79 Elf_Addr base_alignment; 80 Elf_Addr base_vaddr; 81 Elf_Addr base_vlimit; 82 Elf_Addr text_vlimit; 83 Elf_Addr text_end; 84 void *base_addr; 85 Elf_Off data_offset; 86 Elf_Addr data_vaddr; 87 Elf_Addr data_vlimit; 88 int data_flags; 89 int data_prot; 90 caddr_t data_addr; 91 Elf_Addr bss_vaddr; 92 Elf_Addr bss_vlimit; 93 caddr_t bss_addr; 94 #if defined(__HAVE_TLS_VARIANT_I) || defined(__HAVE_TLS_VARIANT_II) 95 Elf_Addr tls_vaddr = 0; /* Noise GCC */ 96 #endif 97 Elf_Addr phdr_vaddr; 98 size_t phdr_memsz, phsize; 99 int i; 100 #ifdef RTLD_LOADER 101 Elf_Addr clear_vaddr; 102 caddr_t clear_page; 103 caddr_t clear_addr; 104 size_t nclear; 105 #endif 106 #ifdef GNU_RELRO 107 Elf_Addr relro_page; 108 size_t relro_size; 109 #endif 110 #ifdef notyet 111 int stack_flags; 112 #endif 113 114 if (sb != NULL && sb->st_size < (off_t)sizeof (Elf_Ehdr)) { 115 _rtld_error("%s: not ELF file (too short)", path); 116 return NULL; 117 } 118 119 obj = _rtld_obj_new(); 120 obj->path = xstrdup(path); 121 obj->pathlen = strlen(path); 122 if (sb != NULL) { 123 obj->dev = sb->st_dev; 124 obj->ino = sb->st_ino; 125 } 126 127 ehdr = mmap(NULL, _rtld_pagesz, PROT_READ, MAP_FILE | MAP_SHARED, fd, 128 (off_t)0); 129 obj->ehdr = ehdr; 130 if (ehdr == MAP_FAILED) { 131 _rtld_error("%s: read error: %s", path, xstrerror(errno)); 132 goto error; 133 } 134 /* Make sure the file is valid */ 135 if (memcmp(ELFMAG, ehdr->e_ident, SELFMAG) != 0) { 136 _rtld_error("%s: not ELF file (magic number bad)", path); 137 goto error; 138 } 139 if (ehdr->e_ident[EI_CLASS] != ELFCLASS) { 140 _rtld_error("%s: invalid ELF class %x; expected %x", path, 141 ehdr->e_ident[EI_CLASS], ELFCLASS); 142 goto error; 143 } 144 /* Elf_e_ident includes class */ 145 if (ehdr->e_ident[EI_VERSION] != EV_CURRENT || 146 ehdr->e_version != EV_CURRENT || 147 ehdr->e_ident[EI_DATA] != ELFDEFNNAME(MACHDEP_ENDIANNESS)) { 148 _rtld_error("%s: unsupported file version", path); 149 goto error; 150 } 151 if (ehdr->e_type != ET_EXEC && ehdr->e_type != ET_DYN) { 152 _rtld_error("%s: unsupported file type", path); 153 goto error; 154 } 155 switch (ehdr->e_machine) { 156 ELFDEFNNAME(MACHDEP_ID_CASES) 157 default: 158 _rtld_error("%s: unsupported machine", path); 159 goto error; 160 } 161 162 /* 163 * We rely on the program header being in the first page. This is 164 * not strictly required by the ABI specification, but it seems to 165 * always true in practice. And, it simplifies things considerably. 166 */ 167 assert(ehdr->e_phentsize == sizeof(Elf_Phdr)); 168 assert(ehdr->e_phoff + ehdr->e_phnum * sizeof(Elf_Phdr) <= 169 _rtld_pagesz); 170 171 /* 172 * Scan the program header entries, and save key information. 173 * 174 * We rely on there being exactly two load segments, text and data, 175 * in that order. 176 */ 177 phdr = (Elf_Phdr *) ((caddr_t)ehdr + ehdr->e_phoff); 178 #if defined(__HAVE_TLS_VARIANT_I) || defined(__HAVE_TLS_VARIANT_II) 179 phtls = NULL; 180 #endif 181 phsize = ehdr->e_phnum * sizeof(phdr[0]); 182 obj->phdr = NULL; 183 #ifdef GNU_RELRO 184 relro_page = 0; 185 relro_size = 0; 186 #endif 187 phdr_vaddr = EA_UNDEF; 188 phdr_memsz = 0; 189 phlimit = phdr + ehdr->e_phnum; 190 segs = xmalloc(sizeof(segs[0]) * ehdr->e_phnum); 191 if (segs == NULL) { 192 _rtld_error("No memory for segs"); 193 goto error; 194 } 195 #ifdef notyet 196 stack_flags = PF_R | PF_W; 197 #endif 198 nsegs = -1; 199 while (phdr < phlimit) { 200 switch (phdr->p_type) { 201 case PT_INTERP: 202 obj->interp = (void *)(uintptr_t)phdr->p_vaddr; 203 dbg(("%s: PT_INTERP %p", obj->path, obj->interp)); 204 break; 205 206 case PT_LOAD: 207 segs[++nsegs] = phdr; 208 if ((segs[nsegs]->p_align & (_rtld_pagesz - 1)) != 0) { 209 _rtld_error( 210 "%s: PT_LOAD segment %d not page-aligned", 211 path, nsegs); 212 goto error; 213 } 214 if ((segs[nsegs]->p_flags & PF_X) == PF_X) { 215 text_end = MAX(text_end, 216 round_up(segs[nsegs]->p_vaddr + 217 segs[nsegs]->p_memsz)); 218 } 219 220 dbg(("%s: %s %p phsize %" PRImemsz, obj->path, 221 "PT_LOAD", 222 (void *)(uintptr_t)phdr->p_vaddr, phdr->p_memsz)); 223 break; 224 225 case PT_PHDR: 226 phdr_vaddr = phdr->p_vaddr; 227 phdr_memsz = phdr->p_memsz; 228 dbg(("%s: %s %p phsize %" PRImemsz, obj->path, 229 "PT_PHDR", 230 (void *)(uintptr_t)phdr->p_vaddr, phdr->p_memsz)); 231 break; 232 233 #ifdef notyet 234 case PT_GNU_STACK: 235 stack_flags = phdr->p_flags; 236 break; 237 #endif 238 239 #ifdef GNU_RELRO 240 case PT_GNU_RELRO: 241 relro_page = phdr->p_vaddr; 242 relro_size = phdr->p_memsz; 243 break; 244 #endif 245 246 case PT_DYNAMIC: 247 obj->dynamic = (void *)(uintptr_t)phdr->p_vaddr; 248 dbg(("%s: %s %p phsize %" PRImemsz, obj->path, 249 "PT_DYNAMIC", 250 (void *)(uintptr_t)phdr->p_vaddr, phdr->p_memsz)); 251 break; 252 253 #if defined(__HAVE_TLS_VARIANT_I) || defined(__HAVE_TLS_VARIANT_II) 254 case PT_TLS: 255 phtls = phdr; 256 dbg(("%s: %s %p phsize %" PRImemsz, obj->path, "PT_TLS", 257 (void *)(uintptr_t)phdr->p_vaddr, phdr->p_memsz)); 258 break; 259 #endif 260 #ifdef __ARM_EABI__ 261 case PT_ARM_EXIDX: 262 obj->exidx_start = (void *)(uintptr_t)phdr->p_vaddr; 263 obj->exidx_sz = phdr->p_memsz; 264 break; 265 #endif 266 } 267 268 ++phdr; 269 } 270 phdr = (Elf_Phdr *) ((caddr_t)ehdr + ehdr->e_phoff); 271 obj->entry = (void *)(uintptr_t)ehdr->e_entry; 272 if (!obj->dynamic) { 273 _rtld_error("%s: not dynamically linked", path); 274 goto error; 275 } 276 277 /* 278 * Map the entire address space of the object as a file 279 * region to stake out our contiguous region and establish a 280 * base for relocation. We use a file mapping so that 281 * the kernel will give us whatever alignment is appropriate 282 * for the platform we're running on. 283 * 284 * We map it using the text protection, map the data segment 285 * into the right place, then map an anon segment for the bss 286 * and unmap the gaps left by padding to alignment. 287 */ 288 289 base_alignment = segs[0]->p_align; 290 base_vaddr = round_down(segs[0]->p_vaddr); 291 base_vlimit = round_up(segs[nsegs]->p_vaddr + segs[nsegs]->p_memsz); 292 text_vlimit = round_up(segs[0]->p_vaddr + segs[0]->p_memsz); 293 data_offset = round_down(segs[nsegs]->p_offset); 294 data_vaddr = round_down(segs[nsegs]->p_vaddr); 295 data_vlimit = round_up(segs[nsegs]->p_vaddr + segs[nsegs]->p_filesz); 296 data_flags = convert_prot(segs[nsegs]->p_flags); 297 #ifdef RTLD_LOADER 298 clear_vaddr = segs[nsegs]->p_vaddr + segs[nsegs]->p_filesz; 299 #endif 300 301 obj->textsize = text_vlimit - base_vaddr; 302 obj->vaddrbase = base_vaddr; 303 obj->isdynamic = ehdr->e_type == ET_DYN; 304 305 #if defined(__HAVE_TLS_VARIANT_I) || defined(__HAVE_TLS_VARIANT_II) 306 if (phtls != NULL) { 307 ++_rtld_tls_dtv_generation; 308 obj->tlsindex = ++_rtld_tls_max_index; 309 obj->tlssize = phtls->p_memsz; 310 obj->tlsalign = phtls->p_align; 311 obj->tlsinitsize = phtls->p_filesz; 312 tls_vaddr = phtls->p_vaddr; 313 } 314 #endif 315 316 /* 317 * Calculate log2 of the base section alignment. 318 */ 319 mapflags = MAP_PRIVATE | MAP_ANON; 320 if (base_alignment > _rtld_pagesz) { 321 unsigned int log2 = 0; 322 for (; base_alignment > 1; base_alignment >>= 1) 323 log2++; 324 mapflags |= MAP_ALIGNED(log2); 325 } 326 327 base_addr = NULL; 328 #ifdef RTLD_LOADER 329 if (!obj->isdynamic) { 330 mapflags |= MAP_TRYFIXED; 331 base_addr = (void *)(uintptr_t)base_vaddr; 332 } 333 #endif 334 mapsize = base_vlimit - base_vaddr; 335 mapbase = mmap(base_addr, mapsize, PROT_NONE, mapflags, -1, 0); 336 if (mapbase == MAP_FAILED) { 337 _rtld_error("mmap of entire address space failed: %s", 338 xstrerror(errno)); 339 goto error; 340 } 341 #ifdef RTLD_LOADER 342 if (!obj->isdynamic && mapbase != base_addr) { 343 _rtld_error("mmap of executable at correct address failed"); 344 goto error; 345 } 346 #endif 347 348 obj->phdr_loaded = false; 349 for (i = 0; i <= nsegs; i++) { 350 /* Overlay the segment onto the proper region. */ 351 data_offset = round_down(segs[i]->p_offset); 352 data_vaddr = round_down(segs[i]->p_vaddr); 353 data_vlimit = round_up(segs[i]->p_vaddr 354 + segs[i]->p_filesz); 355 data_addr = mapbase + (data_vaddr - base_vaddr); 356 data_prot = convert_prot(segs[i]->p_flags); 357 data_flags = convert_flags(segs[i]->p_flags) | MAP_FIXED; 358 if (data_vlimit != data_vaddr && 359 mmap(data_addr, data_vlimit - data_vaddr, data_prot, 360 data_flags, fd, data_offset) == MAP_FAILED) { 361 _rtld_error("%s: mmap of data failed: %s", path, 362 xstrerror(errno)); 363 goto error; 364 } 365 366 /* Do BSS setup */ 367 if (segs[i]->p_filesz != segs[i]->p_memsz) { 368 #ifdef RTLD_LOADER 369 /* Clear any BSS in the last page of the segment. */ 370 clear_vaddr = segs[i]->p_vaddr + segs[i]->p_filesz; 371 clear_addr = mapbase + (clear_vaddr - base_vaddr); 372 clear_page = mapbase + (round_down(clear_vaddr) 373 - base_vaddr); 374 375 if ((nclear = data_vlimit - clear_vaddr) > 0) { 376 /* Make sure the end of the segment is writable 377 */ 378 if ((data_prot & PROT_WRITE) == 0 && -1 == 379 mprotect(clear_page, _rtld_pagesz, 380 data_prot|PROT_WRITE)) { 381 _rtld_error("%s: mprotect failed: %s", 382 path, xstrerror(errno)); 383 goto error; 384 } 385 386 memset(clear_addr, 0, nclear); 387 388 /* Reset the data protection back */ 389 if ((data_prot & PROT_WRITE) == 0) 390 mprotect(clear_page, _rtld_pagesz, 391 data_prot); 392 } 393 #endif 394 395 /* Overlay the BSS segment onto the proper region. */ 396 bss_vaddr = data_vlimit; 397 bss_vlimit = round_up(segs[i]->p_vaddr + 398 segs[i]->p_memsz); 399 bss_addr = mapbase + (bss_vaddr - base_vaddr); 400 if (bss_vlimit > bss_vaddr) { 401 /* There is something to do */ 402 if (mmap(bss_addr, bss_vlimit - bss_vaddr, 403 data_prot, data_flags | MAP_ANON, -1, 0) 404 == MAP_FAILED) { 405 _rtld_error( 406 "%s: mmap of bss failed: %s", 407 path, xstrerror(errno)); 408 goto error; 409 } 410 } 411 } 412 413 if (phdr_vaddr != EA_UNDEF && 414 segs[i]->p_vaddr <= phdr_vaddr && 415 segs[i]->p_memsz >= phdr_memsz) { 416 obj->phdr_loaded = true; 417 } 418 if (segs[i]->p_offset <= ehdr->e_phoff && 419 segs[i]->p_memsz >= phsize) { 420 phdr_vaddr = segs[i]->p_vaddr + ehdr->e_phoff; 421 phdr_memsz = phsize; 422 obj->phdr_loaded = true; 423 } 424 } 425 if (obj->phdr_loaded) { 426 obj->phdr = (void *)(uintptr_t)phdr_vaddr; 427 obj->phsize = phdr_memsz; 428 } else { 429 Elf_Phdr *buf = xmalloc(phsize); 430 if (buf == NULL) { 431 _rtld_error("%s: cannot allocate program header", path); 432 goto error; 433 } 434 memcpy(buf, phdr, phsize); 435 obj->phdr = buf; 436 obj->phsize = phsize; 437 } 438 439 #if defined(__HAVE_TLS_VARIANT_I) || defined(__HAVE_TLS_VARIANT_II) 440 if (phtls != NULL) 441 obj->tlsinit = mapbase + tls_vaddr; 442 #endif 443 444 obj->mapbase = mapbase; 445 obj->mapsize = mapsize; 446 obj->relocbase = mapbase - base_vaddr; 447 448 #ifdef GNU_RELRO 449 /* rounding happens later. */ 450 obj->relro_page = obj->relocbase + relro_page; 451 obj->relro_size = relro_size; 452 #endif 453 454 if (obj->dynamic) 455 obj->dynamic = (void *)(obj->relocbase + (Elf_Addr)(uintptr_t)obj->dynamic); 456 if (obj->entry) 457 obj->entry = (void *)(obj->relocbase + (Elf_Addr)(uintptr_t)obj->entry); 458 if (obj->interp) 459 obj->interp = (void *)(obj->relocbase + (Elf_Addr)(uintptr_t)obj->interp); 460 if (obj->phdr_loaded) 461 obj->phdr = (void *)(obj->relocbase + (Elf_Addr)(uintptr_t)obj->phdr); 462 #ifdef __ARM_EABI__ 463 if (obj->exidx_start) 464 obj->exidx_start = (void *)(obj->relocbase + (Elf_Addr)(uintptr_t)obj->exidx_start); 465 #endif 466 xfree(segs); 467 468 return obj; 469 470 error: 471 if (mapbase != MAP_FAILED) 472 munmap(mapbase, mapsize); 473 if (obj->ehdr != MAP_FAILED) 474 munmap(obj->ehdr, _rtld_pagesz); 475 _rtld_obj_free(obj); 476 xfree(segs); 477 return NULL; 478 } 479 480 void 481 _rtld_obj_free(Obj_Entry *obj) 482 { 483 Objlist_Entry *elm; 484 Name_Entry *entry; 485 486 #if defined(__HAVE_TLS_VARIANT_I) || defined(__HAVE_TLS_VARIANT_II) 487 if (obj->tls_done) 488 _rtld_tls_offset_free(obj); 489 #endif 490 xfree(obj->path); 491 while (obj->needed != NULL) { 492 Needed_Entry *needed = obj->needed; 493 obj->needed = needed->next; 494 xfree(needed); 495 } 496 while ((entry = SIMPLEQ_FIRST(&obj->names)) != NULL) { 497 SIMPLEQ_REMOVE_HEAD(&obj->names, link); 498 xfree(entry); 499 } 500 while ((elm = SIMPLEQ_FIRST(&obj->dldags)) != NULL) { 501 SIMPLEQ_REMOVE_HEAD(&obj->dldags, link); 502 xfree(elm); 503 } 504 while ((elm = SIMPLEQ_FIRST(&obj->dagmembers)) != NULL) { 505 SIMPLEQ_REMOVE_HEAD(&obj->dagmembers, link); 506 xfree(elm); 507 } 508 if (!obj->phdr_loaded) 509 xfree((void *)(uintptr_t)obj->phdr); 510 xfree(obj); 511 } 512 513 Obj_Entry * 514 _rtld_obj_new(void) 515 { 516 Obj_Entry *obj; 517 518 obj = CNEW(Obj_Entry); 519 SIMPLEQ_INIT(&obj->names); 520 SIMPLEQ_INIT(&obj->dldags); 521 SIMPLEQ_INIT(&obj->dagmembers); 522 return obj; 523 } 524 525 /* 526 * Given a set of ELF protection flags, return the corresponding protection 527 * flags for MMAP. 528 */ 529 static int 530 convert_prot(int elfflags) 531 { 532 int prot = 0; 533 534 if (elfflags & PF_R) 535 prot |= PROT_READ; 536 #ifdef RTLD_LOADER 537 if (elfflags & PF_W) 538 prot |= PROT_WRITE; 539 #endif 540 if (elfflags & PF_X) 541 prot |= PROT_EXEC; 542 return prot; 543 } 544 545 static int 546 convert_flags(int elfflags __unused) 547 { 548 int flags = MAP_PRIVATE; /* All mappings are private */ 549 550 #ifdef MAP_NOCORE 551 /* 552 * Readonly mappings are marked "MAP_NOCORE", because they can be 553 * reconstructed by a debugger. 554 */ 555 if (!(elfflags & PF_W)) 556 flags |= MAP_NOCORE; 557 #endif 558 return flags; 559 } 560
Indexes created Fri Sep 26 08:10:20 GMT 2025