1 /*- 2 * Copyright (c) 2006-2011 Joseph Koshy 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 AND CONTRIBUTORS ``AS IS'' AND 15 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 16 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 17 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 18 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 19 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 20 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 21 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 22 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 23 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 24 * SUCH DAMAGE. 25 */ 26 27 #include <sys/param.h> 28 #include <sys/stat.h> 29 30 #include <assert.h> 31 #include <errno.h> 32 #include <gelf.h> 33 #include <libelf.h> 34 #include <stdlib.h> 35 #include <string.h> 36 #include <unistd.h> 37 38 #include "_libelf.h" 39 40 #if ELFTC_HAVE_MMAP 41 #include <sys/mman.h> 42 #endif 43 44 ELFTC_VCSID("$Id: elf_update.c 3013 2014-03-23 06:16:59Z jkoshy $"); 45 46 /* 47 * Layout strategy: 48 * 49 * - Case 1: ELF_F_LAYOUT is asserted 50 * In this case the application has full control over where the 51 * section header table, program header table, and section data 52 * will reside. The library only perform error checks. 53 * 54 * - Case 2: ELF_F_LAYOUT is not asserted 55 * 56 * The library will do the object layout using the following 57 * ordering: 58 * - The executable header is placed first, are required by the 59 * ELF specification. 60 * - The program header table is placed immediately following the 61 * executable header. 62 * - Section data, if any, is placed after the program header 63 * table, aligned appropriately. 64 * - The section header table, if needed, is placed last. 65 * 66 * There are two sub-cases to be taken care of: 67 * 68 * - Case 2a: e->e_cmd == ELF_C_READ or ELF_C_RDWR 69 * 70 * In this sub-case, the underlying ELF object may already have 71 * content in it, which the application may have modified. The 72 * library will retrieve content from the existing object as 73 * needed. 74 * 75 * - Case 2b: e->e_cmd == ELF_C_WRITE 76 * 77 * The ELF object is being created afresh in this sub-case; 78 * there is no pre-existing content in the underlying ELF 79 * object. 80 */ 81 82 /* 83 * The types of extents in an ELF object. 84 */ 85 enum elf_extent { 86 ELF_EXTENT_EHDR, 87 ELF_EXTENT_PHDR, 88 ELF_EXTENT_SECTION, 89 ELF_EXTENT_SHDR 90 }; 91 92 /* 93 * A extent descriptor, used when laying out an ELF object. 94 */ 95 struct _Elf_Extent { 96 SLIST_ENTRY(_Elf_Extent) ex_next; 97 uint64_t ex_start; /* Start of the region. */ 98 uint64_t ex_size; /* The size of the region. */ 99 enum elf_extent ex_type; /* Type of region. */ 100 void *ex_desc; /* Associated descriptor. */ 101 }; 102 103 SLIST_HEAD(_Elf_Extent_List, _Elf_Extent); 104 105 /* 106 * Compute the extents of a section, by looking at the data 107 * descriptors associated with it. The function returns 1 108 * if successful, or zero if an error was detected. 109 */ 110 static int 111 _libelf_compute_section_extents(Elf *e, Elf_Scn *s, off_t rc) 112 { 113 Elf_Data *d; 114 size_t fsz, msz; 115 int ec, elftype; 116 uint32_t sh_type; 117 uint64_t d_align; 118 Elf32_Shdr *shdr32; 119 Elf64_Shdr *shdr64; 120 struct _Libelf_Data *ld; 121 uint64_t scn_size, scn_alignment; 122 uint64_t sh_align, sh_entsize, sh_offset, sh_size; 123 124 ec = e->e_class; 125 126 shdr32 = &s->s_shdr.s_shdr32; 127 shdr64 = &s->s_shdr.s_shdr64; 128 if (ec == ELFCLASS32) { 129 sh_type = shdr32->sh_type; 130 sh_align = (uint64_t) shdr32->sh_addralign; 131 sh_entsize = (uint64_t) shdr32->sh_entsize; 132 sh_offset = (uint64_t) shdr32->sh_offset; 133 sh_size = (uint64_t) shdr32->sh_size; 134 } else { 135 sh_type = shdr64->sh_type; 136 sh_align = shdr64->sh_addralign; 137 sh_entsize = shdr64->sh_entsize; 138 sh_offset = shdr64->sh_offset; 139 sh_size = shdr64->sh_size; 140 } 141 142 assert(sh_type != SHT_NULL && sh_type != SHT_NOBITS); 143 144 elftype = _libelf_xlate_shtype(sh_type); 145 if (elftype > ELF_T_LAST) { 146 LIBELF_SET_ERROR(SECTION, 0); 147 return (0); 148 } 149 150 if (sh_align == 0) 151 sh_align = _libelf_falign(elftype, ec); 152 153 /* 154 * Compute the section's size and alignment using the data 155 * descriptors associated with the section. 156 */ 157 if (STAILQ_EMPTY(&s->s_data)) { 158 /* 159 * The section's content (if any) has not been read in 160 * yet. If section is not dirty marked dirty, we can 161 * reuse the values in the 'sh_size' and 'sh_offset' 162 * fields of the section header. 163 */ 164 if ((s->s_flags & ELF_F_DIRTY) == 0) { 165 /* 166 * If the library is doing the layout, then we 167 * compute the new start offset for the 168 * section based on the current offset and the 169 * section's alignment needs. 170 * 171 * If the application is doing the layout, we 172 * can use the value in the 'sh_offset' field 173 * in the section header directly. 174 */ 175 if (e->e_flags & ELF_F_LAYOUT) 176 goto updatedescriptor; 177 else 178 goto computeoffset; 179 } 180 181 /* 182 * Otherwise, we need to bring in the section's data 183 * from the underlying ELF object. 184 */ 185 if (e->e_cmd != ELF_C_WRITE && elf_getdata(s, NULL) == NULL) 186 return (0); 187 } 188 189 /* 190 * Loop through the section's data descriptors. 191 */ 192 scn_size = 0L; 193 scn_alignment = 0; 194 STAILQ_FOREACH(ld, &s->s_data, d_next) { 195 196 d = &ld->d_data; 197 198 /* 199 * The data buffer's type is known. 200 */ 201 if (d->d_type >= ELF_T_NUM) { 202 LIBELF_SET_ERROR(DATA, 0); 203 return (0); 204 } 205 206 /* 207 * The data buffer's version is supported. 208 */ 209 if (d->d_version != e->e_version) { 210 LIBELF_SET_ERROR(VERSION, 0); 211 return (0); 212 } 213 214 /* 215 * The buffer's alignment is non-zero and a power of 216 * two. 217 */ 218 if ((d_align = d->d_align) == 0 || 219 (d_align & (d_align - 1))) { 220 LIBELF_SET_ERROR(DATA, 0); 221 return (0); 222 } 223 224 /* 225 * The buffer's size should be a multiple of the 226 * memory size of the underlying type. 227 */ 228 msz = _libelf_msize(d->d_type, ec, e->e_version); 229 if (d->d_size % msz) { 230 LIBELF_SET_ERROR(DATA, 0); 231 return (0); 232 } 233 234 /* 235 * If the application is controlling layout, then the 236 * d_offset field should be compatible with the 237 * buffer's specified alignment. 238 */ 239 if ((e->e_flags & ELF_F_LAYOUT) && 240 (d->d_off & (d_align - 1))) { 241 LIBELF_SET_ERROR(LAYOUT, 0); 242 return (0); 243 } 244 245 /* 246 * Compute the section's size. 247 */ 248 if (e->e_flags & ELF_F_LAYOUT) { 249 if ((uint64_t) d->d_off + d->d_size > scn_size) 250 scn_size = d->d_off + d->d_size; 251 } else { 252 scn_size = roundup2(scn_size, d->d_align); 253 d->d_off = scn_size; 254 fsz = _libelf_fsize(d->d_type, ec, d->d_version, 255 (size_t) d->d_size / msz); 256 scn_size += fsz; 257 } 258 259 /* 260 * The section's alignment is the maximum alignment 261 * needed for its data buffers. 262 */ 263 if (d_align > scn_alignment) 264 scn_alignment = d_align; 265 } 266 267 268 /* 269 * If the application is requesting full control over the 270 * layout of the section, check the section's specified size, 271 * offsets and alignment for sanity. 272 */ 273 if (e->e_flags & ELF_F_LAYOUT) { 274 if (scn_alignment > sh_align || sh_offset % sh_align || 275 sh_size < scn_size) { 276 LIBELF_SET_ERROR(LAYOUT, 0); 277 return (0); 278 } 279 goto updatedescriptor; 280 } 281 282 /* 283 * Otherwise, compute the values in the section header. 284 * 285 * The section alignment is the maximum alignment for any of 286 * its contained data descriptors. 287 */ 288 if (scn_alignment > sh_align) 289 sh_align = scn_alignment; 290 291 /* 292 * If the section entry size is zero, try and fill in an 293 * appropriate entry size. Per the elf(5) manual page 294 * sections without fixed-size entries should have their 295 * 'sh_entsize' field set to zero. 296 */ 297 if (sh_entsize == 0 && 298 (sh_entsize = _libelf_fsize(elftype, ec, e->e_version, 299 (size_t) 1)) == 1) 300 sh_entsize = 0; 301 302 sh_size = scn_size; 303 304 computeoffset: 305 /* 306 * Compute the new offset for the section based on 307 * the section's alignment needs. 308 */ 309 sh_offset = roundup((uint64_t) rc, sh_align); 310 311 /* 312 * Update the section header. 313 */ 314 if (ec == ELFCLASS32) { 315 shdr32->sh_addralign = (uint32_t) sh_align; 316 shdr32->sh_entsize = (uint32_t) sh_entsize; 317 shdr32->sh_offset = (uint32_t) sh_offset; 318 shdr32->sh_size = (uint32_t) sh_size; 319 } else { 320 shdr64->sh_addralign = sh_align; 321 shdr64->sh_entsize = sh_entsize; 322 shdr64->sh_offset = sh_offset; 323 shdr64->sh_size = sh_size; 324 } 325 326 updatedescriptor: 327 /* 328 * Update the section descriptor. 329 */ 330 s->s_size = sh_size; 331 s->s_offset = sh_offset; 332 333 return (1); 334 } 335 336 /* 337 * Free a list of extent descriptors. 338 */ 339 340 static void 341 _libelf_release_extents(struct _Elf_Extent_List *extents) 342 { 343 struct _Elf_Extent *ex; 344 345 while ((ex = SLIST_FIRST(extents)) != NULL) { 346 SLIST_REMOVE_HEAD(extents, ex_next); 347 free(ex); 348 } 349 } 350 351 /* 352 * Check if an extent 's' defined by [start..start+size) is free. 353 * This routine assumes that the given extent list is sorted in order 354 * of ascending extent offsets. 355 */ 356 357 static int 358 _libelf_extent_is_unused(struct _Elf_Extent_List *extents, 359 const uint64_t start, const uint64_t size, struct _Elf_Extent **prevt) 360 { 361 uint64_t tmax, tmin; 362 struct _Elf_Extent *t, *pt; 363 const uint64_t smax = start + size; 364 365 /* First, look for overlaps with existing extents. */ 366 pt = NULL; 367 SLIST_FOREACH(t, extents, ex_next) { 368 tmin = t->ex_start; 369 tmax = tmin + t->ex_size; 370 371 if (tmax <= start) { 372 /* 373 * 't' lies entirely before 's': ...| t |...| s |... 374 */ 375 pt = t; 376 continue; 377 } else if (smax <= tmin) { 378 /* 379 * 's' lies entirely before 't', and after 'pt': 380 * ...| pt |...| s |...| t |... 381 */ 382 assert(pt == NULL || 383 pt->ex_start + pt->ex_size <= start); 384 break; 385 } else 386 /* 's' and 't' overlap. */ 387 return (0); 388 } 389 390 if (prevt) 391 *prevt = pt; 392 return (1); 393 } 394 395 /* 396 * Insert an extent into the list of extents. 397 */ 398 399 static int 400 _libelf_insert_extent(struct _Elf_Extent_List *extents, int type, 401 uint64_t start, uint64_t size, void *desc) 402 { 403 struct _Elf_Extent *ex, *prevt; 404 405 assert(type >= ELF_EXTENT_EHDR && type <= ELF_EXTENT_SHDR); 406 407 prevt = NULL; 408 409 /* 410 * If the requested range overlaps with an existing extent, 411 * signal an error. 412 */ 413 if (!_libelf_extent_is_unused(extents, start, size, &prevt)) { 414 LIBELF_SET_ERROR(LAYOUT, 0); 415 return (0); 416 } 417 418 /* Allocate and fill in a new extent descriptor. */ 419 if ((ex = malloc(sizeof(struct _Elf_Extent))) == NULL) { 420 LIBELF_SET_ERROR(RESOURCE, errno); 421 return (0); 422 } 423 ex->ex_start = start; 424 ex->ex_size = size; 425 ex->ex_desc = desc; 426 ex->ex_type = type; 427 428 /* Insert the region descriptor into the list. */ 429 if (prevt) 430 SLIST_INSERT_AFTER(prevt, ex, ex_next); 431 else 432 SLIST_INSERT_HEAD(extents, ex, ex_next); 433 return (1); 434 } 435 436 /* 437 * Recompute section layout. 438 */ 439 440 static off_t 441 _libelf_resync_sections(Elf *e, off_t rc, struct _Elf_Extent_List *extents) 442 { 443 int ec; 444 Elf_Scn *s; 445 size_t sh_type; 446 447 ec = e->e_class; 448 449 /* 450 * Make a pass through sections, computing the extent of each 451 * section. 452 */ 453 STAILQ_FOREACH(s, &e->e_u.e_elf.e_scn, s_next) { 454 if (ec == ELFCLASS32) 455 sh_type = s->s_shdr.s_shdr32.sh_type; 456 else 457 sh_type = s->s_shdr.s_shdr64.sh_type; 458 459 if (sh_type == SHT_NOBITS || sh_type == SHT_NULL) 460 continue; 461 462 if (_libelf_compute_section_extents(e, s, rc) == 0) 463 return ((off_t) -1); 464 465 if (s->s_size == 0) 466 continue; 467 468 if (!_libelf_insert_extent(extents, ELF_EXTENT_SECTION, 469 s->s_offset, s->s_size, s)) 470 return ((off_t) -1); 471 472 if ((size_t) rc < s->s_offset + s->s_size) 473 rc = (off_t) (s->s_offset + s->s_size); 474 } 475 476 return (rc); 477 } 478 479 /* 480 * Recompute the layout of the ELF object and update the internal data 481 * structures associated with the ELF descriptor. 482 * 483 * Returns the size in bytes the ELF object would occupy in its file 484 * representation. 485 * 486 * After a successful call to this function, the following structures 487 * are updated: 488 * 489 * - The ELF header is updated. 490 * - All extents in the ELF object are sorted in order of ascending 491 * addresses. Sections have their section header table entries 492 * updated. An error is signalled if an overlap was detected among 493 * extents. 494 * - Data descriptors associated with sections are checked for valid 495 * types, offsets and alignment. 496 * 497 * After a resync_elf() successfully returns, the ELF descriptor is 498 * ready for being handed over to _libelf_write_elf(). 499 */ 500 501 static off_t 502 _libelf_resync_elf(Elf *e, struct _Elf_Extent_List *extents) 503 { 504 int ec, eh_class; 505 unsigned int eh_byteorder, eh_version; 506 size_t align, fsz; 507 size_t phnum, shnum; 508 off_t rc, phoff, shoff; 509 void *ehdr, *phdr; 510 Elf32_Ehdr *eh32; 511 Elf64_Ehdr *eh64; 512 513 rc = 0; 514 515 ec = e->e_class; 516 517 assert(ec == ELFCLASS32 || ec == ELFCLASS64); 518 519 /* 520 * Prepare the EHDR. 521 */ 522 if ((ehdr = _libelf_ehdr(e, ec, 0)) == NULL) 523 return ((off_t) -1); 524 525 eh32 = ehdr; 526 eh64 = ehdr; 527 528 if (ec == ELFCLASS32) { 529 eh_byteorder = eh32->e_ident[EI_DATA]; 530 eh_class = eh32->e_ident[EI_CLASS]; 531 phoff = (off_t) eh32->e_phoff; 532 shoff = (off_t) eh32->e_shoff; 533 eh_version = eh32->e_version; 534 } else { 535 eh_byteorder = eh64->e_ident[EI_DATA]; 536 eh_class = eh64->e_ident[EI_CLASS]; 537 phoff = (off_t) eh64->e_phoff; 538 shoff = (off_t) eh64->e_shoff; 539 eh_version = eh64->e_version; 540 } 541 542 if (phoff < 0 || shoff < 0) { 543 LIBELF_SET_ERROR(HEADER, 0); 544 return ((off_t) -1); 545 } 546 547 if (eh_version == EV_NONE) 548 eh_version = EV_CURRENT; 549 550 if (eh_version != e->e_version) { /* always EV_CURRENT */ 551 LIBELF_SET_ERROR(VERSION, 0); 552 return ((off_t) -1); 553 } 554 555 if (eh_class != e->e_class) { 556 LIBELF_SET_ERROR(CLASS, 0); 557 return ((off_t) -1); 558 } 559 560 if (e->e_cmd != ELF_C_WRITE && eh_byteorder != e->e_byteorder) { 561 LIBELF_SET_ERROR(HEADER, 0); 562 return ((off_t) -1); 563 } 564 565 shnum = e->e_u.e_elf.e_nscn; 566 phnum = e->e_u.e_elf.e_nphdr; 567 568 e->e_byteorder = eh_byteorder; 569 570 #define INITIALIZE_EHDR(E,EC,V) do { \ 571 unsigned int _version = (unsigned int) (V); \ 572 (E)->e_ident[EI_MAG0] = ELFMAG0; \ 573 (E)->e_ident[EI_MAG1] = ELFMAG1; \ 574 (E)->e_ident[EI_MAG2] = ELFMAG2; \ 575 (E)->e_ident[EI_MAG3] = ELFMAG3; \ 576 (E)->e_ident[EI_CLASS] = (unsigned char) (EC); \ 577 (E)->e_ident[EI_VERSION] = (_version & 0xFFU); \ 578 (E)->e_ehsize = (uint16_t) _libelf_fsize(ELF_T_EHDR, \ 579 (EC), _version, (size_t) 1); \ 580 (E)->e_phentsize = (uint16_t) ((phnum == 0) ? 0 : \ 581 _libelf_fsize(ELF_T_PHDR, (EC), _version, \ 582 (size_t) 1)); \ 583 (E)->e_shentsize = (uint16_t) _libelf_fsize(ELF_T_SHDR, \ 584 (EC), _version, (size_t) 1); \ 585 } while (0) 586 587 if (ec == ELFCLASS32) 588 INITIALIZE_EHDR(eh32, ec, eh_version); 589 else 590 INITIALIZE_EHDR(eh64, ec, eh_version); 591 592 (void) elf_flagehdr(e, ELF_C_SET, ELF_F_DIRTY); 593 594 rc += (off_t) _libelf_fsize(ELF_T_EHDR, ec, eh_version, (size_t) 1); 595 596 if (!_libelf_insert_extent(extents, ELF_EXTENT_EHDR, 0, (uint64_t) rc, 597 ehdr)) 598 return ((off_t) -1); 599 600 /* 601 * Compute the layout the program header table, if one is 602 * present. The program header table needs to be aligned to a 603 * `natural' boundary. 604 */ 605 if (phnum) { 606 fsz = _libelf_fsize(ELF_T_PHDR, ec, eh_version, phnum); 607 align = _libelf_falign(ELF_T_PHDR, ec); 608 609 if (e->e_flags & ELF_F_LAYOUT) { 610 /* 611 * Check offsets for sanity. 612 */ 613 if (rc > phoff) { 614 LIBELF_SET_ERROR(LAYOUT, 0); 615 return ((off_t) -1); 616 } 617 618 if (phoff % (off_t) align) { 619 LIBELF_SET_ERROR(LAYOUT, 0); 620 return ((off_t) -1); 621 } 622 623 } else 624 phoff = roundup(rc, (off_t) align); 625 626 rc = phoff + (off_t) fsz; 627 628 phdr = _libelf_getphdr(e, ec); 629 630 if (!_libelf_insert_extent(extents, ELF_EXTENT_PHDR, 631 (uint64_t) phoff, fsz, phdr)) 632 return ((off_t) -1); 633 } else 634 phoff = 0; 635 636 /* 637 * Compute the layout of the sections associated with the 638 * file. 639 */ 640 641 if (e->e_cmd != ELF_C_WRITE && 642 (e->e_flags & LIBELF_F_SHDRS_LOADED) == 0 && 643 _libelf_load_section_headers(e, ehdr) == 0) 644 return ((off_t) -1); 645 646 if ((rc = _libelf_resync_sections(e, rc, extents)) < 0) 647 return ((off_t) -1); 648 649 /* 650 * Compute the space taken up by the section header table, if 651 * one is needed. 652 * 653 * If ELF_F_LAYOUT has been asserted, the application may have 654 * placed the section header table in between existing 655 * sections, so the net size of the file need not increase due 656 * to the presence of the section header table. 657 * 658 * If the library is responsible for laying out the object, 659 * the section header table is placed after section data. 660 */ 661 if (shnum) { 662 fsz = _libelf_fsize(ELF_T_SHDR, ec, eh_version, shnum); 663 align = _libelf_falign(ELF_T_SHDR, ec); 664 665 if (e->e_flags & ELF_F_LAYOUT) { 666 if (shoff % (off_t) align) { 667 LIBELF_SET_ERROR(LAYOUT, 0); 668 return ((off_t) -1); 669 } 670 } else 671 shoff = roundup(rc, (off_t) align); 672 673 if (shoff + (off_t) fsz > rc) 674 rc = shoff + (off_t) fsz; 675 676 if (!_libelf_insert_extent(extents, ELF_EXTENT_SHDR, 677 (uint64_t) shoff, fsz, NULL)) 678 return ((off_t) -1); 679 } else 680 shoff = 0; 681 682 /* 683 * Set the fields of the Executable Header that could potentially use 684 * extended numbering. 685 */ 686 _libelf_setphnum(e, ehdr, ec, phnum); 687 _libelf_setshnum(e, ehdr, ec, shnum); 688 689 /* 690 * Update the `e_phoff' and `e_shoff' fields if the library is 691 * doing the layout. 692 */ 693 if ((e->e_flags & ELF_F_LAYOUT) == 0) { 694 if (ec == ELFCLASS32) { 695 eh32->e_phoff = (uint32_t) phoff; 696 eh32->e_shoff = (uint32_t) shoff; 697 } else { 698 eh64->e_phoff = (uint64_t) phoff; 699 eh64->e_shoff = (uint64_t) shoff; 700 } 701 } 702 703 return (rc); 704 } 705 706 /* 707 * Write out the contents of an ELF section. 708 */ 709 710 static off_t 711 _libelf_write_scn(Elf *e, unsigned char *nf, struct _Elf_Extent *ex) 712 { 713 int ec; 714 off_t rc; 715 Elf_Scn *s; 716 int elftype; 717 Elf_Data *d, dst; 718 uint32_t sh_type; 719 struct _Libelf_Data *ld; 720 uint64_t sh_off, sh_size; 721 size_t fsz, msz, nobjects; 722 723 assert(ex->ex_type == ELF_EXTENT_SECTION); 724 725 s = ex->ex_desc; 726 rc = (off_t) ex->ex_start; 727 728 if ((ec = e->e_class) == ELFCLASS32) { 729 sh_type = s->s_shdr.s_shdr32.sh_type; 730 sh_size = (uint64_t) s->s_shdr.s_shdr32.sh_size; 731 } else { 732 sh_type = s->s_shdr.s_shdr64.sh_type; 733 sh_size = s->s_shdr.s_shdr64.sh_size; 734 } 735 736 /* 737 * Ignore sections that do not allocate space in the file. 738 */ 739 if (sh_type == SHT_NOBITS || sh_type == SHT_NULL || sh_size == 0) 740 return (rc); 741 742 elftype = _libelf_xlate_shtype(sh_type); 743 assert(elftype >= ELF_T_FIRST && elftype <= ELF_T_LAST); 744 745 sh_off = s->s_offset; 746 assert(sh_off % _libelf_falign(elftype, ec) == 0); 747 748 /* 749 * If the section has a `rawdata' descriptor, and the section 750 * contents have not been modified, use its contents directly. 751 * The `s_rawoff' member contains the offset into the original 752 * file, while `s_offset' contains its new location in the 753 * destination. 754 */ 755 756 if (STAILQ_EMPTY(&s->s_data)) { 757 758 if ((d = elf_rawdata(s, NULL)) == NULL) 759 return ((off_t) -1); 760 761 STAILQ_FOREACH(ld, &s->s_rawdata, d_next) { 762 763 d = &ld->d_data; 764 765 if ((uint64_t) rc < sh_off + d->d_off) 766 (void) memset(nf + rc, 767 LIBELF_PRIVATE(fillchar), 768 (size_t) (sh_off + d->d_off - 769 (uint64_t) rc)); 770 rc = (off_t) (sh_off + d->d_off); 771 772 assert(d->d_buf != NULL); 773 assert(d->d_type == ELF_T_BYTE); 774 assert(d->d_version == e->e_version); 775 776 (void) memcpy(nf + rc, 777 e->e_rawfile + s->s_rawoff + d->d_off, 778 (size_t) d->d_size); 779 780 rc += (off_t) d->d_size; 781 } 782 783 return (rc); 784 } 785 786 /* 787 * Iterate over the set of data descriptors for this section. 788 * The prior call to _libelf_resync_elf() would have setup the 789 * descriptors for this step. 790 */ 791 792 dst.d_version = e->e_version; 793 794 STAILQ_FOREACH(ld, &s->s_data, d_next) { 795 796 d = &ld->d_data; 797 798 msz = _libelf_msize(d->d_type, ec, e->e_version); 799 800 if ((uint64_t) rc < sh_off + d->d_off) 801 (void) memset(nf + rc, 802 LIBELF_PRIVATE(fillchar), 803 (size_t) (sh_off + d->d_off - (uint64_t) rc)); 804 805 rc = (off_t) (sh_off + d->d_off); 806 807 assert(d->d_buf != NULL); 808 assert(d->d_version == e->e_version); 809 assert(d->d_size % msz == 0); 810 811 nobjects = (size_t) (d->d_size / msz); 812 813 fsz = _libelf_fsize(d->d_type, ec, e->e_version, nobjects); 814 815 dst.d_buf = nf + rc; 816 dst.d_size = fsz; 817 818 if (_libelf_xlate(&dst, d, e->e_byteorder, ec, ELF_TOFILE) == 819 NULL) 820 return ((off_t) -1); 821 822 rc += (off_t) fsz; 823 } 824 825 return (rc); 826 } 827 828 /* 829 * Write out an ELF Executable Header. 830 */ 831 832 static off_t 833 _libelf_write_ehdr(Elf *e, unsigned char *nf, struct _Elf_Extent *ex) 834 { 835 int ec; 836 void *ehdr; 837 size_t fsz, msz; 838 Elf_Data dst, src; 839 840 assert(ex->ex_type == ELF_EXTENT_EHDR); 841 assert(ex->ex_start == 0); /* Ehdr always comes first. */ 842 843 ec = e->e_class; 844 845 ehdr = _libelf_ehdr(e, ec, 0); 846 assert(ehdr != NULL); 847 848 fsz = _libelf_fsize(ELF_T_EHDR, ec, e->e_version, (size_t) 1); 849 msz = _libelf_msize(ELF_T_EHDR, ec, e->e_version); 850 851 (void) memset(&dst, 0, sizeof(dst)); 852 (void) memset(&src, 0, sizeof(src)); 853 854 src.d_buf = ehdr; 855 src.d_size = msz; 856 src.d_type = ELF_T_EHDR; 857 src.d_version = dst.d_version = e->e_version; 858 859 dst.d_buf = nf; 860 dst.d_size = fsz; 861 862 if (_libelf_xlate(&dst, &src, e->e_byteorder, ec, ELF_TOFILE) == 863 NULL) 864 return ((off_t) -1); 865 866 return ((off_t) fsz); 867 } 868 869 /* 870 * Write out an ELF program header table. 871 */ 872 873 static off_t 874 _libelf_write_phdr(Elf *e, unsigned char *nf, struct _Elf_Extent *ex) 875 { 876 int ec; 877 void *ehdr; 878 Elf32_Ehdr *eh32; 879 Elf64_Ehdr *eh64; 880 Elf_Data dst, src; 881 size_t fsz, phnum; 882 uint64_t phoff; 883 884 assert(ex->ex_type == ELF_EXTENT_PHDR); 885 886 ec = e->e_class; 887 ehdr = _libelf_ehdr(e, ec, 0); 888 phnum = e->e_u.e_elf.e_nphdr; 889 890 assert(phnum > 0); 891 892 if (ec == ELFCLASS32) { 893 eh32 = (Elf32_Ehdr *) ehdr; 894 phoff = (uint64_t) eh32->e_phoff; 895 } else { 896 eh64 = (Elf64_Ehdr *) ehdr; 897 phoff = eh64->e_phoff; 898 } 899 900 assert(phoff > 0); 901 assert(ex->ex_start == phoff); 902 assert(phoff % _libelf_falign(ELF_T_PHDR, ec) == 0); 903 904 (void) memset(&dst, 0, sizeof(dst)); 905 (void) memset(&src, 0, sizeof(src)); 906 907 fsz = _libelf_fsize(ELF_T_PHDR, ec, e->e_version, phnum); 908 assert(fsz > 0); 909 910 src.d_buf = _libelf_getphdr(e, ec); 911 src.d_version = dst.d_version = e->e_version; 912 src.d_type = ELF_T_PHDR; 913 src.d_size = phnum * _libelf_msize(ELF_T_PHDR, ec, 914 e->e_version); 915 916 dst.d_size = fsz; 917 dst.d_buf = nf + ex->ex_start; 918 919 if (_libelf_xlate(&dst, &src, e->e_byteorder, ec, ELF_TOFILE) == 920 NULL) 921 return ((off_t) -1); 922 923 return ((off_t) (phoff + fsz)); 924 } 925 926 /* 927 * Write out an ELF section header table. 928 */ 929 930 static off_t 931 _libelf_write_shdr(Elf *e, unsigned char *nf, struct _Elf_Extent *ex) 932 { 933 int ec; 934 void *ehdr; 935 Elf_Scn *scn; 936 uint64_t shoff; 937 Elf32_Ehdr *eh32; 938 Elf64_Ehdr *eh64; 939 size_t fsz, nscn; 940 Elf_Data dst, src; 941 942 assert(ex->ex_type == ELF_EXTENT_SHDR); 943 944 ec = e->e_class; 945 ehdr = _libelf_ehdr(e, ec, 0); 946 nscn = e->e_u.e_elf.e_nscn; 947 948 if (ec == ELFCLASS32) { 949 eh32 = (Elf32_Ehdr *) ehdr; 950 shoff = (uint64_t) eh32->e_shoff; 951 } else { 952 eh64 = (Elf64_Ehdr *) ehdr; 953 shoff = eh64->e_shoff; 954 } 955 956 assert(nscn > 0); 957 assert(shoff % _libelf_falign(ELF_T_SHDR, ec) == 0); 958 assert(ex->ex_start == shoff); 959 960 (void) memset(&dst, 0, sizeof(dst)); 961 (void) memset(&src, 0, sizeof(src)); 962 963 src.d_type = ELF_T_SHDR; 964 src.d_size = _libelf_msize(ELF_T_SHDR, ec, e->e_version); 965 src.d_version = dst.d_version = e->e_version; 966 967 fsz = _libelf_fsize(ELF_T_SHDR, ec, e->e_version, (size_t) 1); 968 969 STAILQ_FOREACH(scn, &e->e_u.e_elf.e_scn, s_next) { 970 if (ec == ELFCLASS32) 971 src.d_buf = &scn->s_shdr.s_shdr32; 972 else 973 src.d_buf = &scn->s_shdr.s_shdr64; 974 975 dst.d_size = fsz; 976 dst.d_buf = nf + ex->ex_start + scn->s_ndx * fsz; 977 978 if (_libelf_xlate(&dst, &src, e->e_byteorder, ec, 979 ELF_TOFILE) == NULL) 980 return ((off_t) -1); 981 } 982 983 return ((off_t) (ex->ex_start + nscn * fsz)); 984 } 985 986 /* 987 * Write out the file image. 988 * 989 * The original file could have been mapped in with an ELF_C_RDWR 990 * command and the application could have added new content or 991 * re-arranged its sections before calling elf_update(). Consequently 992 * its not safe to work `in place' on the original file. So we 993 * malloc() the required space for the updated ELF object and build 994 * the object there and write it out to the underlying file at the 995 * end. Note that the application may have opened the underlying file 996 * in ELF_C_RDWR and only retrieved/modified a few sections. We take 997 * care to avoid translating file sections unnecessarily. 998 * 999 * Gaps in the coverage of the file by the file's sections will be 1000 * filled with the fill character set by elf_fill(3). 1001 */ 1002 1003 static off_t 1004 _libelf_write_elf(Elf *e, off_t newsize, struct _Elf_Extent_List *extents) 1005 { 1006 off_t nrc, rc; 1007 Elf_Scn *scn, *tscn; 1008 struct _Elf_Extent *ex; 1009 unsigned char *newfile; 1010 1011 assert(e->e_kind == ELF_K_ELF); 1012 assert(e->e_cmd == ELF_C_RDWR || e->e_cmd == ELF_C_WRITE); 1013 assert(e->e_fd >= 0); 1014 1015 if ((newfile = malloc((size_t) newsize)) == NULL) { 1016 LIBELF_SET_ERROR(RESOURCE, errno); 1017 return ((off_t) -1); 1018 } 1019 1020 nrc = rc = 0; 1021 SLIST_FOREACH(ex, extents, ex_next) { 1022 1023 /* Fill inter-extent gaps. */ 1024 if (ex->ex_start > (size_t) rc) 1025 (void) memset(newfile + rc, LIBELF_PRIVATE(fillchar), 1026 (size_t) (ex->ex_start - (uint64_t) rc)); 1027 1028 switch (ex->ex_type) { 1029 case ELF_EXTENT_EHDR: 1030 if ((nrc = _libelf_write_ehdr(e, newfile, ex)) < 0) 1031 goto error; 1032 break; 1033 1034 case ELF_EXTENT_PHDR: 1035 if ((nrc = _libelf_write_phdr(e, newfile, ex)) < 0) 1036 goto error; 1037 break; 1038 1039 case ELF_EXTENT_SECTION: 1040 if ((nrc = _libelf_write_scn(e, newfile, ex)) < 0) 1041 goto error; 1042 break; 1043 1044 case ELF_EXTENT_SHDR: 1045 if ((nrc = _libelf_write_shdr(e, newfile, ex)) < 0) 1046 goto error; 1047 break; 1048 1049 default: 1050 assert(0); 1051 break; 1052 } 1053 1054 assert(ex->ex_start + ex->ex_size == (size_t) nrc); 1055 assert(rc < nrc); 1056 1057 rc = nrc; 1058 } 1059 1060 assert(rc == newsize); 1061 1062 /* 1063 * For regular files, throw away existing file content and 1064 * unmap any existing mappings. 1065 */ 1066 if ((e->e_flags & LIBELF_F_SPECIAL_FILE) == 0) { 1067 if (ftruncate(e->e_fd, (off_t) 0) < 0 || 1068 lseek(e->e_fd, (off_t) 0, SEEK_SET)) { 1069 LIBELF_SET_ERROR(IO, errno); 1070 goto error; 1071 } 1072 #if ELFTC_HAVE_MMAP 1073 if (e->e_flags & LIBELF_F_RAWFILE_MMAP) { 1074 assert(e->e_rawfile != NULL); 1075 assert(e->e_cmd == ELF_C_RDWR); 1076 if (munmap(e->e_rawfile, e->e_rawsize) < 0) { 1077 LIBELF_SET_ERROR(IO, errno); 1078 goto error; 1079 } 1080 } 1081 #endif 1082 } 1083 1084 /* 1085 * Write out the new contents. 1086 */ 1087 if (write(e->e_fd, newfile, (size_t) newsize) != newsize) { 1088 LIBELF_SET_ERROR(IO, errno); 1089 goto error; 1090 } 1091 1092 /* 1093 * For files opened in ELF_C_RDWR mode, set up the new 'raw' 1094 * contents. 1095 */ 1096 if (e->e_cmd == ELF_C_RDWR) { 1097 assert(e->e_rawfile != NULL); 1098 assert((e->e_flags & LIBELF_F_RAWFILE_MALLOC) || 1099 (e->e_flags & LIBELF_F_RAWFILE_MMAP)); 1100 if (e->e_flags & LIBELF_F_RAWFILE_MALLOC) { 1101 free(e->e_rawfile); 1102 e->e_rawfile = newfile; 1103 newfile = NULL; 1104 } 1105 #if ELFTC_HAVE_MMAP 1106 else if (e->e_flags & LIBELF_F_RAWFILE_MMAP) { 1107 if ((e->e_rawfile = mmap(NULL, (size_t) newsize, 1108 PROT_READ, MAP_PRIVATE, e->e_fd, (off_t) 0)) == 1109 MAP_FAILED) { 1110 LIBELF_SET_ERROR(IO, errno); 1111 goto error; 1112 } 1113 } 1114 #endif /* ELFTC_HAVE_MMAP */ 1115 1116 /* Record the new size of the file. */ 1117 e->e_rawsize = (size_t) newsize; 1118 } else { 1119 /* File opened in ELF_C_WRITE mode. */ 1120 assert(e->e_rawfile == NULL); 1121 } 1122 1123 /* 1124 * Reset flags, remove existing section descriptors and 1125 * {E,P}HDR pointers so that a subsequent elf_get{e,p}hdr() 1126 * and elf_getscn() will function correctly. 1127 */ 1128 1129 e->e_flags &= ~ELF_F_DIRTY; 1130 1131 STAILQ_FOREACH_SAFE(scn, &e->e_u.e_elf.e_scn, s_next, tscn) 1132 _libelf_release_scn(scn); 1133 1134 if (e->e_class == ELFCLASS32) { 1135 free(e->e_u.e_elf.e_ehdr.e_ehdr32); 1136 if (e->e_u.e_elf.e_phdr.e_phdr32) 1137 free(e->e_u.e_elf.e_phdr.e_phdr32); 1138 1139 e->e_u.e_elf.e_ehdr.e_ehdr32 = NULL; 1140 e->e_u.e_elf.e_phdr.e_phdr32 = NULL; 1141 } else { 1142 free(e->e_u.e_elf.e_ehdr.e_ehdr64); 1143 if (e->e_u.e_elf.e_phdr.e_phdr64) 1144 free(e->e_u.e_elf.e_phdr.e_phdr64); 1145 1146 e->e_u.e_elf.e_ehdr.e_ehdr64 = NULL; 1147 e->e_u.e_elf.e_phdr.e_phdr64 = NULL; 1148 } 1149 1150 /* Free the temporary buffer. */ 1151 if (newfile) 1152 free(newfile); 1153 1154 return (rc); 1155 1156 error: 1157 free(newfile); 1158 1159 return ((off_t) -1); 1160 } 1161 1162 /* 1163 * Update an ELF object. 1164 */ 1165 1166 off_t 1167 elf_update(Elf *e, Elf_Cmd c) 1168 { 1169 int ec; 1170 off_t rc; 1171 struct _Elf_Extent_List extents; 1172 1173 rc = (off_t) -1; 1174 1175 if (e == NULL || e->e_kind != ELF_K_ELF || 1176 (c != ELF_C_NULL && c != ELF_C_WRITE)) { 1177 LIBELF_SET_ERROR(ARGUMENT, 0); 1178 return (rc); 1179 } 1180 1181 if ((ec = e->e_class) != ELFCLASS32 && ec != ELFCLASS64) { 1182 LIBELF_SET_ERROR(CLASS, 0); 1183 return (rc); 1184 } 1185 1186 if (e->e_version == EV_NONE) 1187 e->e_version = EV_CURRENT; 1188 1189 if (c == ELF_C_WRITE && e->e_cmd == ELF_C_READ) { 1190 LIBELF_SET_ERROR(MODE, 0); 1191 return (rc); 1192 } 1193 1194 SLIST_INIT(&extents); 1195 1196 if ((rc = _libelf_resync_elf(e, &extents)) < 0) 1197 goto done; 1198 1199 if (c == ELF_C_NULL) 1200 goto done; 1201 1202 if (e->e_fd < 0) { 1203 rc = (off_t) -1; 1204 LIBELF_SET_ERROR(SEQUENCE, 0); 1205 goto done; 1206 } 1207 1208 rc = _libelf_write_elf(e, rc, &extents); 1209 1210 done: 1211 _libelf_release_extents(&extents); 1212 return (rc); 1213 } 1214