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 3763 2019-06-28 21:43:27Z emaste $"); 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_FIRST || 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 data buffer's ELF type, ELF class and ELF version 226 * should be supported. 227 */ 228 if ((msz = _libelf_msize(d->d_type, ec, e->e_version)) == 0) 229 return (0); 230 231 /* 232 * The buffer's size should be a multiple of the 233 * memory size of the underlying type. 234 */ 235 if (d->d_size % msz) { 236 LIBELF_SET_ERROR(DATA, 0); 237 return (0); 238 } 239 240 /* 241 * If the application is controlling layout, then the 242 * d_offset field should be compatible with the 243 * buffer's specified alignment. 244 */ 245 if ((e->e_flags & ELF_F_LAYOUT) && 246 (d->d_off & (d_align - 1))) { 247 LIBELF_SET_ERROR(LAYOUT, 0); 248 return (0); 249 } 250 251 /* 252 * Compute the section's size. 253 */ 254 if (e->e_flags & ELF_F_LAYOUT) { 255 if ((uint64_t) d->d_off + d->d_size > scn_size) 256 scn_size = d->d_off + d->d_size; 257 } else { 258 scn_size = roundup2(scn_size, d->d_align); 259 d->d_off = scn_size; 260 fsz = _libelf_fsize(d->d_type, ec, d->d_version, 261 (size_t) d->d_size / msz); 262 scn_size += fsz; 263 } 264 265 /* 266 * The section's alignment is the maximum alignment 267 * needed for its data buffers. 268 */ 269 if (d_align > scn_alignment) 270 scn_alignment = d_align; 271 } 272 273 274 /* 275 * If the application is requesting full control over the 276 * layout of the section, check the section's specified size, 277 * offsets and alignment for sanity. 278 */ 279 if (e->e_flags & ELF_F_LAYOUT) { 280 if (scn_alignment > sh_align || 281 sh_offset % sh_align || 282 sh_size < scn_size || 283 sh_offset % _libelf_falign(elftype, ec)) { 284 LIBELF_SET_ERROR(LAYOUT, 0); 285 return (0); 286 } 287 goto updatedescriptor; 288 } 289 290 /* 291 * Otherwise, compute the values in the section header. 292 * 293 * The section alignment is the maximum alignment for any of 294 * its contained data descriptors. 295 */ 296 if (scn_alignment > sh_align) 297 sh_align = scn_alignment; 298 299 /* 300 * If the section entry size is zero, try and fill in an 301 * appropriate entry size. Per the elf(5) manual page 302 * sections without fixed-size entries should have their 303 * 'sh_entsize' field set to zero. 304 */ 305 if (sh_entsize == 0 && 306 (sh_entsize = _libelf_fsize(elftype, ec, e->e_version, 307 (size_t) 1)) == 1) 308 sh_entsize = 0; 309 310 sh_size = scn_size; 311 312 computeoffset: 313 /* 314 * Compute the new offset for the section based on 315 * the section's alignment needs. 316 */ 317 sh_offset = roundup((uint64_t) rc, sh_align); 318 319 /* 320 * Update the section header. 321 */ 322 if (ec == ELFCLASS32) { 323 shdr32->sh_addralign = (uint32_t) sh_align; 324 shdr32->sh_entsize = (uint32_t) sh_entsize; 325 shdr32->sh_offset = (uint32_t) sh_offset; 326 shdr32->sh_size = (uint32_t) sh_size; 327 } else { 328 shdr64->sh_addralign = sh_align; 329 shdr64->sh_entsize = sh_entsize; 330 shdr64->sh_offset = sh_offset; 331 shdr64->sh_size = sh_size; 332 } 333 334 updatedescriptor: 335 /* 336 * Update the section descriptor. 337 */ 338 s->s_size = sh_size; 339 s->s_offset = sh_offset; 340 341 return (1); 342 } 343 344 /* 345 * Free a list of extent descriptors. 346 */ 347 348 static void 349 _libelf_release_extents(struct _Elf_Extent_List *extents) 350 { 351 struct _Elf_Extent *ex; 352 353 while ((ex = SLIST_FIRST(extents)) != NULL) { 354 SLIST_REMOVE_HEAD(extents, ex_next); 355 free(ex); 356 } 357 } 358 359 /* 360 * Check if an extent 's' defined by [start..start+size) is free. 361 * This routine assumes that the given extent list is sorted in order 362 * of ascending extent offsets. 363 */ 364 365 static int 366 _libelf_extent_is_unused(struct _Elf_Extent_List *extents, 367 const uint64_t start, const uint64_t size, struct _Elf_Extent **prevt) 368 { 369 uint64_t tmax, tmin; 370 struct _Elf_Extent *t, *pt; 371 const uint64_t smax = start + size; 372 373 /* First, look for overlaps with existing extents. */ 374 pt = NULL; 375 SLIST_FOREACH(t, extents, ex_next) { 376 tmin = t->ex_start; 377 tmax = tmin + t->ex_size; 378 379 if (tmax <= start) { 380 /* 381 * 't' lies entirely before 's': ...| t |...| s |... 382 */ 383 pt = t; 384 continue; 385 } else if (smax <= tmin) { 386 /* 387 * 's' lies entirely before 't', and after 'pt': 388 * ...| pt |...| s |...| t |... 389 */ 390 assert(pt == NULL || 391 pt->ex_start + pt->ex_size <= start); 392 break; 393 } else 394 /* 's' and 't' overlap. */ 395 return (0); 396 } 397 398 if (prevt) 399 *prevt = pt; 400 return (1); 401 } 402 403 /* 404 * Insert an extent into the list of extents. 405 */ 406 407 static int 408 _libelf_insert_extent(struct _Elf_Extent_List *extents, int type, 409 uint64_t start, uint64_t size, void *desc) 410 { 411 struct _Elf_Extent *ex, *prevt; 412 413 assert(type >= ELF_EXTENT_EHDR && type <= ELF_EXTENT_SHDR); 414 415 prevt = NULL; 416 417 /* 418 * If the requested range overlaps with an existing extent, 419 * signal an error. 420 */ 421 if (!_libelf_extent_is_unused(extents, start, size, &prevt)) { 422 LIBELF_SET_ERROR(LAYOUT, 0); 423 return (0); 424 } 425 426 /* Allocate and fill in a new extent descriptor. */ 427 if ((ex = malloc(sizeof(struct _Elf_Extent))) == NULL) { 428 LIBELF_SET_ERROR(RESOURCE, errno); 429 return (0); 430 } 431 ex->ex_start = start; 432 ex->ex_size = size; 433 ex->ex_desc = desc; 434 ex->ex_type = type; 435 436 /* Insert the region descriptor into the list. */ 437 if (prevt) 438 SLIST_INSERT_AFTER(prevt, ex, ex_next); 439 else 440 SLIST_INSERT_HEAD(extents, ex, ex_next); 441 return (1); 442 } 443 444 /* 445 * Recompute section layout. 446 */ 447 448 static off_t 449 _libelf_resync_sections(Elf *e, off_t rc, struct _Elf_Extent_List *extents) 450 { 451 int ec; 452 Elf_Scn *s; 453 size_t sh_type; 454 455 ec = e->e_class; 456 457 /* 458 * Make a pass through sections, computing the extent of each 459 * section. 460 */ 461 RB_FOREACH(s, scntree, &e->e_u.e_elf.e_scn) { 462 if (ec == ELFCLASS32) 463 sh_type = s->s_shdr.s_shdr32.sh_type; 464 else 465 sh_type = s->s_shdr.s_shdr64.sh_type; 466 467 if (sh_type == SHT_NOBITS || sh_type == SHT_NULL) 468 continue; 469 470 if (_libelf_compute_section_extents(e, s, rc) == 0) 471 return ((off_t) -1); 472 473 if (s->s_size == 0) 474 continue; 475 476 if (!_libelf_insert_extent(extents, ELF_EXTENT_SECTION, 477 s->s_offset, s->s_size, s)) 478 return ((off_t) -1); 479 480 if ((size_t) rc < s->s_offset + s->s_size) 481 rc = (off_t) (s->s_offset + s->s_size); 482 } 483 484 return (rc); 485 } 486 487 /* 488 * Recompute the layout of the ELF object and update the internal data 489 * structures associated with the ELF descriptor. 490 * 491 * Returns the size in bytes the ELF object would occupy in its file 492 * representation. 493 * 494 * After a successful call to this function, the following structures 495 * are updated: 496 * 497 * - The ELF header is updated. 498 * - All extents in the ELF object are sorted in order of ascending 499 * addresses. Sections have their section header table entries 500 * updated. An error is signalled if an overlap was detected among 501 * extents. 502 * - Data descriptors associated with sections are checked for valid 503 * types, offsets and alignment. 504 * 505 * After a resync_elf() successfully returns, the ELF descriptor is 506 * ready for being handed over to _libelf_write_elf(). 507 */ 508 509 static off_t 510 _libelf_resync_elf(Elf *e, struct _Elf_Extent_List *extents) 511 { 512 int ec, eh_class; 513 unsigned int eh_byteorder, eh_version; 514 size_t align, fsz; 515 size_t phnum, shnum; 516 off_t rc, phoff, shoff; 517 void *ehdr, *phdr; 518 Elf32_Ehdr *eh32; 519 Elf64_Ehdr *eh64; 520 521 rc = 0; 522 523 ec = e->e_class; 524 525 assert(ec == ELFCLASS32 || ec == ELFCLASS64); 526 527 /* 528 * Prepare the EHDR. 529 */ 530 if ((ehdr = _libelf_ehdr(e, ec, 0)) == NULL) 531 return ((off_t) -1); 532 533 eh32 = ehdr; 534 eh64 = ehdr; 535 536 if (ec == ELFCLASS32) { 537 eh_byteorder = eh32->e_ident[EI_DATA]; 538 eh_class = eh32->e_ident[EI_CLASS]; 539 phoff = (off_t) eh32->e_phoff; 540 shoff = (off_t) eh32->e_shoff; 541 eh_version = eh32->e_version; 542 } else { 543 eh_byteorder = eh64->e_ident[EI_DATA]; 544 eh_class = eh64->e_ident[EI_CLASS]; 545 phoff = (off_t) eh64->e_phoff; 546 shoff = (off_t) eh64->e_shoff; 547 eh_version = eh64->e_version; 548 } 549 550 if (phoff < 0 || shoff < 0) { 551 LIBELF_SET_ERROR(HEADER, 0); 552 return ((off_t) -1); 553 } 554 555 if (eh_version == EV_NONE) 556 eh_version = EV_CURRENT; 557 558 if (eh_version != e->e_version) { /* always EV_CURRENT */ 559 LIBELF_SET_ERROR(VERSION, 0); 560 return ((off_t) -1); 561 } 562 563 if (eh_class != e->e_class) { 564 LIBELF_SET_ERROR(CLASS, 0); 565 return ((off_t) -1); 566 } 567 568 if (e->e_cmd != ELF_C_WRITE && eh_byteorder != e->e_byteorder) { 569 LIBELF_SET_ERROR(HEADER, 0); 570 return ((off_t) -1); 571 } 572 573 shnum = e->e_u.e_elf.e_nscn; 574 phnum = e->e_u.e_elf.e_nphdr; 575 576 e->e_byteorder = eh_byteorder; 577 578 #define INITIALIZE_EHDR(E,EC,V) do { \ 579 unsigned int _version = (unsigned int) (V); \ 580 (E)->e_ident[EI_MAG0] = ELFMAG0; \ 581 (E)->e_ident[EI_MAG1] = ELFMAG1; \ 582 (E)->e_ident[EI_MAG2] = ELFMAG2; \ 583 (E)->e_ident[EI_MAG3] = ELFMAG3; \ 584 (E)->e_ident[EI_CLASS] = (unsigned char) (EC); \ 585 (E)->e_ident[EI_VERSION] = (_version & 0xFFU); \ 586 (E)->e_ehsize = (uint16_t) _libelf_fsize(ELF_T_EHDR, \ 587 (EC), _version, (size_t) 1); \ 588 (E)->e_phentsize = (uint16_t) ((phnum == 0) ? 0 : \ 589 _libelf_fsize(ELF_T_PHDR, (EC), _version, \ 590 (size_t) 1)); \ 591 (E)->e_shentsize = (uint16_t) _libelf_fsize(ELF_T_SHDR, \ 592 (EC), _version, (size_t) 1); \ 593 } while (0) 594 595 if (ec == ELFCLASS32) 596 INITIALIZE_EHDR(eh32, ec, eh_version); 597 else 598 INITIALIZE_EHDR(eh64, ec, eh_version); 599 600 (void) elf_flagehdr(e, ELF_C_SET, ELF_F_DIRTY); 601 602 rc += (off_t) _libelf_fsize(ELF_T_EHDR, ec, eh_version, (size_t) 1); 603 604 if (!_libelf_insert_extent(extents, ELF_EXTENT_EHDR, 0, (uint64_t) rc, 605 ehdr)) 606 return ((off_t) -1); 607 608 /* 609 * Compute the layout the program header table, if one is 610 * present. The program header table needs to be aligned to a 611 * `natural' boundary. 612 */ 613 if (phnum) { 614 fsz = _libelf_fsize(ELF_T_PHDR, ec, eh_version, phnum); 615 align = _libelf_falign(ELF_T_PHDR, ec); 616 617 if (e->e_flags & ELF_F_LAYOUT) { 618 /* 619 * Check offsets for sanity. 620 */ 621 if (rc > phoff) { 622 LIBELF_SET_ERROR(LAYOUT, 0); 623 return ((off_t) -1); 624 } 625 626 if (phoff % (off_t) align) { 627 LIBELF_SET_ERROR(LAYOUT, 0); 628 return ((off_t) -1); 629 } 630 631 } else 632 phoff = roundup(rc, (off_t) align); 633 634 rc = phoff + (off_t) fsz; 635 636 phdr = _libelf_getphdr(e, ec); 637 638 if (!_libelf_insert_extent(extents, ELF_EXTENT_PHDR, 639 (uint64_t) phoff, fsz, phdr)) 640 return ((off_t) -1); 641 } else 642 phoff = 0; 643 644 /* 645 * Compute the layout of the sections associated with the 646 * file. 647 */ 648 649 if (e->e_cmd != ELF_C_WRITE && 650 (e->e_flags & LIBELF_F_SHDRS_LOADED) == 0 && 651 _libelf_load_section_headers(e, ehdr) == 0) 652 return ((off_t) -1); 653 654 if ((rc = _libelf_resync_sections(e, rc, extents)) < 0) 655 return ((off_t) -1); 656 657 /* 658 * Compute the space taken up by the section header table, if 659 * one is needed. 660 * 661 * If ELF_F_LAYOUT has been asserted, the application may have 662 * placed the section header table in between existing 663 * sections, so the net size of the file need not increase due 664 * to the presence of the section header table. 665 * 666 * If the library is responsible for laying out the object, 667 * the section header table is placed after section data. 668 */ 669 if (shnum) { 670 fsz = _libelf_fsize(ELF_T_SHDR, ec, eh_version, shnum); 671 align = _libelf_falign(ELF_T_SHDR, ec); 672 673 if (e->e_flags & ELF_F_LAYOUT) { 674 if (shoff % (off_t) align) { 675 LIBELF_SET_ERROR(LAYOUT, 0); 676 return ((off_t) -1); 677 } 678 } else 679 shoff = roundup(rc, (off_t) align); 680 681 if (shoff + (off_t) fsz > rc) 682 rc = shoff + (off_t) fsz; 683 684 if (!_libelf_insert_extent(extents, ELF_EXTENT_SHDR, 685 (uint64_t) shoff, fsz, NULL)) 686 return ((off_t) -1); 687 } else 688 shoff = 0; 689 690 /* 691 * Set the fields of the Executable Header that could potentially use 692 * extended numbering. 693 */ 694 _libelf_setphnum(e, ehdr, ec, phnum); 695 _libelf_setshnum(e, ehdr, ec, shnum); 696 697 /* 698 * Update the `e_phoff' and `e_shoff' fields if the library is 699 * doing the layout. 700 */ 701 if ((e->e_flags & ELF_F_LAYOUT) == 0) { 702 if (ec == ELFCLASS32) { 703 eh32->e_phoff = (uint32_t) phoff; 704 eh32->e_shoff = (uint32_t) shoff; 705 } else { 706 eh64->e_phoff = (uint64_t) phoff; 707 eh64->e_shoff = (uint64_t) shoff; 708 } 709 } 710 711 return (rc); 712 } 713 714 /* 715 * Write out the contents of an ELF section. 716 */ 717 718 static off_t 719 _libelf_write_scn(Elf *e, unsigned char *nf, struct _Elf_Extent *ex) 720 { 721 off_t rc; 722 int ec, em; 723 Elf_Scn *s; 724 int elftype; 725 Elf_Data *d, dst; 726 uint32_t sh_type; 727 struct _Libelf_Data *ld; 728 uint64_t sh_off, sh_size; 729 size_t fsz, msz, nobjects; 730 731 assert(ex->ex_type == ELF_EXTENT_SECTION); 732 733 s = ex->ex_desc; 734 rc = (off_t) ex->ex_start; 735 736 if ((ec = e->e_class) == ELFCLASS32) { 737 sh_type = s->s_shdr.s_shdr32.sh_type; 738 sh_size = (uint64_t) s->s_shdr.s_shdr32.sh_size; 739 } else { 740 sh_type = s->s_shdr.s_shdr64.sh_type; 741 sh_size = s->s_shdr.s_shdr64.sh_size; 742 } 743 744 /* 745 * Ignore sections that do not allocate space in the file. 746 */ 747 if (sh_type == SHT_NOBITS || sh_type == SHT_NULL || sh_size == 0) 748 return (rc); 749 750 elftype = _libelf_xlate_shtype(sh_type); 751 assert(elftype >= ELF_T_FIRST && elftype <= ELF_T_LAST); 752 753 sh_off = s->s_offset; 754 assert(sh_off % _libelf_falign(elftype, ec) == 0); 755 756 em = _libelf_elfmachine(e); 757 #if 0 758 assert(em >= EM_NONE && em < EM__LAST__); 759 #endif 760 761 /* 762 * If the section has a `rawdata' descriptor, and the section 763 * contents have not been modified, use its contents directly. 764 * The `s_rawoff' member contains the offset into the original 765 * file, while `s_offset' contains its new location in the 766 * destination. 767 */ 768 769 if (STAILQ_EMPTY(&s->s_data)) { 770 771 if ((d = elf_rawdata(s, NULL)) == NULL) 772 return ((off_t) -1); 773 774 STAILQ_FOREACH(ld, &s->s_rawdata, d_next) { 775 776 d = &ld->d_data; 777 778 if ((uint64_t) rc < sh_off + d->d_off) 779 (void) memset(nf + rc, 780 LIBELF_PRIVATE(fillchar), 781 (size_t) (sh_off + d->d_off - 782 (uint64_t) rc)); 783 rc = (off_t) (sh_off + d->d_off); 784 785 assert(d->d_buf != NULL); 786 assert(d->d_type == ELF_T_BYTE); 787 assert(d->d_version == e->e_version); 788 789 (void) memcpy(nf + rc, 790 e->e_rawfile + s->s_rawoff + d->d_off, 791 (size_t) d->d_size); 792 793 rc += (off_t) d->d_size; 794 } 795 796 return (rc); 797 } 798 799 /* 800 * Iterate over the set of data descriptors for this section. 801 * The prior call to _libelf_resync_elf() would have setup the 802 * descriptors for this step. 803 */ 804 805 dst.d_version = e->e_version; 806 807 STAILQ_FOREACH(ld, &s->s_data, d_next) { 808 809 d = &ld->d_data; 810 811 if ((msz = _libelf_msize(d->d_type, ec, e->e_version)) == 0) 812 return ((off_t) -1); 813 814 if ((uint64_t) rc < sh_off + d->d_off) 815 (void) memset(nf + rc, 816 LIBELF_PRIVATE(fillchar), 817 (size_t) (sh_off + d->d_off - (uint64_t) rc)); 818 819 rc = (off_t) (sh_off + d->d_off); 820 821 assert(d->d_buf != NULL); 822 assert(d->d_version == e->e_version); 823 assert(d->d_size % msz == 0); 824 assert(msz != 0); 825 826 nobjects = (size_t) (d->d_size / msz); 827 828 fsz = _libelf_fsize(d->d_type, ec, e->e_version, nobjects); 829 830 dst.d_buf = nf + rc; 831 dst.d_size = fsz; 832 833 if (_libelf_xlate(&dst, d, e->e_byteorder, ec, em, ELF_TOFILE) 834 == NULL) 835 return ((off_t) -1); 836 837 rc += (off_t) fsz; 838 } 839 840 return (rc); 841 } 842 843 /* 844 * Write out an ELF Executable Header. 845 */ 846 847 static off_t 848 _libelf_write_ehdr(Elf *e, unsigned char *nf, struct _Elf_Extent *ex) 849 { 850 int ec, em; 851 void *ehdr; 852 size_t fsz, msz; 853 Elf_Data dst, src; 854 855 assert(ex->ex_type == ELF_EXTENT_EHDR); 856 assert(ex->ex_start == 0); /* Ehdr always comes first. */ 857 858 ec = e->e_class; 859 860 ehdr = _libelf_ehdr(e, ec, 0); 861 assert(ehdr != NULL); 862 863 fsz = _libelf_fsize(ELF_T_EHDR, ec, e->e_version, (size_t) 1); 864 if ((msz = _libelf_msize(ELF_T_EHDR, ec, e->e_version)) == 0) 865 return ((off_t) -1); 866 867 em = _libelf_elfmachine(e); 868 869 (void) memset(&dst, 0, sizeof(dst)); 870 (void) memset(&src, 0, sizeof(src)); 871 872 src.d_buf = ehdr; 873 src.d_size = msz; 874 src.d_type = ELF_T_EHDR; 875 src.d_version = dst.d_version = e->e_version; 876 877 dst.d_buf = nf; 878 dst.d_size = fsz; 879 880 if (_libelf_xlate(&dst, &src, e->e_byteorder, ec, em, ELF_TOFILE) == 881 NULL) 882 return ((off_t) -1); 883 884 return ((off_t) fsz); 885 } 886 887 /* 888 * Write out an ELF program header table. 889 */ 890 891 static off_t 892 _libelf_write_phdr(Elf *e, unsigned char *nf, struct _Elf_Extent *ex) 893 { 894 int ec, em; 895 void *ehdr; 896 Elf32_Ehdr *eh32; 897 Elf64_Ehdr *eh64; 898 Elf_Data dst, src; 899 size_t fsz, msz, phnum; 900 uint64_t phoff; 901 902 assert(ex->ex_type == ELF_EXTENT_PHDR); 903 904 ec = e->e_class; 905 906 ehdr = _libelf_ehdr(e, ec, 0); 907 assert(ehdr != NULL); 908 909 phnum = e->e_u.e_elf.e_nphdr; 910 assert(phnum > 0); 911 912 if (ec == ELFCLASS32) { 913 eh32 = (Elf32_Ehdr *) ehdr; 914 phoff = (uint64_t) eh32->e_phoff; 915 } else { 916 eh64 = (Elf64_Ehdr *) ehdr; 917 phoff = eh64->e_phoff; 918 } 919 920 em = _libelf_elfmachine(e); 921 922 assert(phoff > 0); 923 assert(ex->ex_start == phoff); 924 assert(phoff % _libelf_falign(ELF_T_PHDR, ec) == 0); 925 926 (void) memset(&dst, 0, sizeof(dst)); 927 (void) memset(&src, 0, sizeof(src)); 928 929 if ((msz = _libelf_msize(ELF_T_PHDR, ec, e->e_version)) == 0) 930 return ((off_t) -1); 931 fsz = _libelf_fsize(ELF_T_PHDR, ec, e->e_version, phnum); 932 assert(fsz > 0); 933 934 src.d_buf = _libelf_getphdr(e, ec); 935 src.d_version = dst.d_version = e->e_version; 936 src.d_type = ELF_T_PHDR; 937 src.d_size = phnum * msz; 938 939 dst.d_size = fsz; 940 dst.d_buf = nf + ex->ex_start; 941 942 if (_libelf_xlate(&dst, &src, e->e_byteorder, ec, em, ELF_TOFILE) == 943 NULL) 944 return ((off_t) -1); 945 946 return ((off_t) (phoff + fsz)); 947 } 948 949 /* 950 * Write out an ELF section header table. 951 */ 952 953 static off_t 954 _libelf_write_shdr(Elf *e, unsigned char *nf, struct _Elf_Extent *ex) 955 { 956 int ec, em; 957 void *ehdr; 958 Elf_Scn *scn; 959 uint64_t shoff; 960 Elf32_Ehdr *eh32; 961 Elf64_Ehdr *eh64; 962 size_t fsz, msz, nscn; 963 Elf_Data dst, src; 964 965 assert(ex->ex_type == ELF_EXTENT_SHDR); 966 967 ec = e->e_class; 968 969 ehdr = _libelf_ehdr(e, ec, 0); 970 assert(ehdr != NULL); 971 972 nscn = e->e_u.e_elf.e_nscn; 973 974 if (ec == ELFCLASS32) { 975 eh32 = (Elf32_Ehdr *) ehdr; 976 shoff = (uint64_t) eh32->e_shoff; 977 } else { 978 eh64 = (Elf64_Ehdr *) ehdr; 979 shoff = eh64->e_shoff; 980 } 981 982 em = _libelf_elfmachine(e); 983 984 assert(nscn > 0); 985 assert(shoff % _libelf_falign(ELF_T_SHDR, ec) == 0); 986 assert(ex->ex_start == shoff); 987 988 (void) memset(&dst, 0, sizeof(dst)); 989 (void) memset(&src, 0, sizeof(src)); 990 991 if ((msz = _libelf_msize(ELF_T_SHDR, ec, e->e_version)) == 0) 992 return ((off_t) -1); 993 994 src.d_type = ELF_T_SHDR; 995 src.d_size = msz; 996 src.d_version = dst.d_version = e->e_version; 997 998 fsz = _libelf_fsize(ELF_T_SHDR, ec, e->e_version, (size_t) 1); 999 1000 RB_FOREACH(scn, scntree, &e->e_u.e_elf.e_scn) { 1001 if (ec == ELFCLASS32) 1002 src.d_buf = &scn->s_shdr.s_shdr32; 1003 else 1004 src.d_buf = &scn->s_shdr.s_shdr64; 1005 1006 dst.d_size = fsz; 1007 dst.d_buf = nf + ex->ex_start + scn->s_ndx * fsz; 1008 1009 if (_libelf_xlate(&dst, &src, e->e_byteorder, ec, em, 1010 ELF_TOFILE) == NULL) 1011 return ((off_t) -1); 1012 } 1013 1014 return ((off_t) (ex->ex_start + nscn * fsz)); 1015 } 1016 1017 /* 1018 * Write out the file image. 1019 * 1020 * The original file could have been mapped in with an ELF_C_RDWR 1021 * command and the application could have added new content or 1022 * re-arranged its sections before calling elf_update(). Consequently 1023 * its not safe to work `in place' on the original file. So we 1024 * malloc() the required space for the updated ELF object and build 1025 * the object there and write it out to the underlying file at the 1026 * end. Note that the application may have opened the underlying file 1027 * in ELF_C_RDWR and only retrieved/modified a few sections. We take 1028 * care to avoid translating file sections unnecessarily. 1029 * 1030 * Gaps in the coverage of the file by the file's sections will be 1031 * filled with the fill character set by elf_fill(3). 1032 */ 1033 1034 static off_t 1035 _libelf_write_elf(Elf *e, off_t newsize, struct _Elf_Extent_List *extents) 1036 { 1037 off_t nrc, rc; 1038 Elf_Scn *scn, *tscn; 1039 struct _Elf_Extent *ex; 1040 unsigned char *newfile; 1041 1042 assert(e->e_kind == ELF_K_ELF); 1043 assert(e->e_cmd == ELF_C_RDWR || e->e_cmd == ELF_C_WRITE); 1044 assert(e->e_fd >= 0); 1045 1046 if ((newfile = malloc((size_t) newsize)) == NULL) { 1047 LIBELF_SET_ERROR(RESOURCE, errno); 1048 return ((off_t) -1); 1049 } 1050 1051 nrc = rc = 0; 1052 SLIST_FOREACH(ex, extents, ex_next) { 1053 1054 /* Fill inter-extent gaps. */ 1055 if (ex->ex_start > (size_t) rc) 1056 (void) memset(newfile + rc, LIBELF_PRIVATE(fillchar), 1057 (size_t) (ex->ex_start - (uint64_t) rc)); 1058 1059 switch (ex->ex_type) { 1060 case ELF_EXTENT_EHDR: 1061 if ((nrc = _libelf_write_ehdr(e, newfile, ex)) < 0) 1062 goto error; 1063 break; 1064 1065 case ELF_EXTENT_PHDR: 1066 if ((nrc = _libelf_write_phdr(e, newfile, ex)) < 0) 1067 goto error; 1068 break; 1069 1070 case ELF_EXTENT_SECTION: 1071 if ((nrc = _libelf_write_scn(e, newfile, ex)) < 0) 1072 goto error; 1073 break; 1074 1075 case ELF_EXTENT_SHDR: 1076 if ((nrc = _libelf_write_shdr(e, newfile, ex)) < 0) 1077 goto error; 1078 break; 1079 1080 default: 1081 assert(0); 1082 break; 1083 } 1084 1085 assert(ex->ex_start + ex->ex_size == (size_t) nrc); 1086 assert(rc < nrc); 1087 1088 rc = nrc; 1089 } 1090 1091 assert(rc == newsize); 1092 1093 /* 1094 * For regular files, throw away existing file content and 1095 * unmap any existing mappings. 1096 */ 1097 if ((e->e_flags & LIBELF_F_SPECIAL_FILE) == 0) { 1098 if (ftruncate(e->e_fd, (off_t) 0) < 0 || 1099 lseek(e->e_fd, (off_t) 0, SEEK_SET)) { 1100 LIBELF_SET_ERROR(IO, errno); 1101 goto error; 1102 } 1103 #if ELFTC_HAVE_MMAP 1104 if (e->e_flags & LIBELF_F_RAWFILE_MMAP) { 1105 assert(e->e_rawfile != NULL); 1106 assert(e->e_cmd == ELF_C_RDWR); 1107 if (munmap(e->e_rawfile, (size_t) e->e_rawsize) < 0) { 1108 LIBELF_SET_ERROR(IO, errno); 1109 goto error; 1110 } 1111 } 1112 #endif 1113 } 1114 1115 /* 1116 * Write out the new contents. 1117 */ 1118 if (write(e->e_fd, newfile, (size_t) newsize) != newsize) { 1119 LIBELF_SET_ERROR(IO, errno); 1120 goto error; 1121 } 1122 1123 /* 1124 * For files opened in ELF_C_RDWR mode, set up the new 'raw' 1125 * contents. 1126 */ 1127 if (e->e_cmd == ELF_C_RDWR) { 1128 assert(e->e_rawfile != NULL); 1129 assert((e->e_flags & LIBELF_F_RAWFILE_MALLOC) || 1130 (e->e_flags & LIBELF_F_RAWFILE_MMAP)); 1131 if (e->e_flags & LIBELF_F_RAWFILE_MALLOC) { 1132 assert((e->e_flags & LIBELF_F_RAWFILE_MMAP) == 0); 1133 free(e->e_rawfile); 1134 e->e_rawfile = newfile; 1135 newfile = NULL; 1136 } 1137 #if ELFTC_HAVE_MMAP 1138 else if (e->e_flags & LIBELF_F_RAWFILE_MMAP) { 1139 assert((e->e_flags & LIBELF_F_RAWFILE_MALLOC) == 0); 1140 if ((e->e_rawfile = mmap(NULL, (size_t) newsize, 1141 PROT_READ, MAP_PRIVATE, e->e_fd, (off_t) 0)) == 1142 MAP_FAILED) { 1143 LIBELF_SET_ERROR(IO, errno); 1144 goto error; 1145 } 1146 } 1147 #endif /* ELFTC_HAVE_MMAP */ 1148 1149 /* Record the new size of the file. */ 1150 e->e_rawsize = newsize; 1151 } else { 1152 /* File opened in ELF_C_WRITE mode. */ 1153 assert(e->e_rawfile == NULL); 1154 } 1155 1156 /* 1157 * Reset flags, remove existing section descriptors and 1158 * {E,P}HDR pointers so that a subsequent elf_get{e,p}hdr() 1159 * and elf_getscn() will function correctly. 1160 */ 1161 1162 e->e_flags &= ~ELF_F_DIRTY; 1163 1164 RB_FOREACH_SAFE(scn, scntree, &e->e_u.e_elf.e_scn, tscn) 1165 _libelf_release_scn(scn); 1166 1167 if (e->e_class == ELFCLASS32) { 1168 free(e->e_u.e_elf.e_ehdr.e_ehdr32); 1169 if (e->e_u.e_elf.e_phdr.e_phdr32) 1170 free(e->e_u.e_elf.e_phdr.e_phdr32); 1171 1172 e->e_u.e_elf.e_ehdr.e_ehdr32 = NULL; 1173 e->e_u.e_elf.e_phdr.e_phdr32 = NULL; 1174 } else { 1175 free(e->e_u.e_elf.e_ehdr.e_ehdr64); 1176 if (e->e_u.e_elf.e_phdr.e_phdr64) 1177 free(e->e_u.e_elf.e_phdr.e_phdr64); 1178 1179 e->e_u.e_elf.e_ehdr.e_ehdr64 = NULL; 1180 e->e_u.e_elf.e_phdr.e_phdr64 = NULL; 1181 } 1182 1183 /* Free the temporary buffer. */ 1184 if (newfile) 1185 free(newfile); 1186 1187 return (rc); 1188 1189 error: 1190 free(newfile); 1191 1192 return ((off_t) -1); 1193 } 1194 1195 /* 1196 * Update an ELF object. 1197 */ 1198 1199 off_t 1200 elf_update(Elf *e, Elf_Cmd c) 1201 { 1202 int ec; 1203 off_t rc; 1204 struct _Elf_Extent_List extents; 1205 1206 rc = (off_t) -1; 1207 1208 if (e == NULL || e->e_kind != ELF_K_ELF || 1209 (c != ELF_C_NULL && c != ELF_C_WRITE)) { 1210 LIBELF_SET_ERROR(ARGUMENT, 0); 1211 return (rc); 1212 } 1213 1214 if ((ec = e->e_class) != ELFCLASS32 && ec != ELFCLASS64) { 1215 LIBELF_SET_ERROR(CLASS, 0); 1216 return (rc); 1217 } 1218 1219 if (e->e_version == EV_NONE) 1220 e->e_version = EV_CURRENT; 1221 1222 if (c == ELF_C_WRITE && e->e_cmd == ELF_C_READ) { 1223 LIBELF_SET_ERROR(MODE, 0); 1224 return (rc); 1225 } 1226 1227 SLIST_INIT(&extents); 1228 1229 if ((rc = _libelf_resync_elf(e, &extents)) < 0) 1230 goto done; 1231 1232 if (c == ELF_C_NULL) 1233 goto done; 1234 1235 if (e->e_fd < 0) { 1236 rc = (off_t) -1; 1237 LIBELF_SET_ERROR(SEQUENCE, 0); 1238 goto done; 1239 } 1240 1241 rc = _libelf_write_elf(e, rc, &extents); 1242 1243 done: 1244 _libelf_release_extents(&extents); 1245 e->e_flags &= ~LIBELF_F_SHDRS_LOADED; 1246 return (rc); 1247 } 1248