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 3190 2015-05-04 15:23:08Z 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 || 275 sh_offset % sh_align || 276 sh_size < scn_size || 277 sh_offset % _libelf_falign(elftype, ec)) { 278 LIBELF_SET_ERROR(LAYOUT, 0); 279 return (0); 280 } 281 goto updatedescriptor; 282 } 283 284 /* 285 * Otherwise, compute the values in the section header. 286 * 287 * The section alignment is the maximum alignment for any of 288 * its contained data descriptors. 289 */ 290 if (scn_alignment > sh_align) 291 sh_align = scn_alignment; 292 293 /* 294 * If the section entry size is zero, try and fill in an 295 * appropriate entry size. Per the elf(5) manual page 296 * sections without fixed-size entries should have their 297 * 'sh_entsize' field set to zero. 298 */ 299 if (sh_entsize == 0 && 300 (sh_entsize = _libelf_fsize(elftype, ec, e->e_version, 301 (size_t) 1)) == 1) 302 sh_entsize = 0; 303 304 sh_size = scn_size; 305 306 computeoffset: 307 /* 308 * Compute the new offset for the section based on 309 * the section's alignment needs. 310 */ 311 sh_offset = roundup((uint64_t) rc, sh_align); 312 313 /* 314 * Update the section header. 315 */ 316 if (ec == ELFCLASS32) { 317 shdr32->sh_addralign = (uint32_t) sh_align; 318 shdr32->sh_entsize = (uint32_t) sh_entsize; 319 shdr32->sh_offset = (uint32_t) sh_offset; 320 shdr32->sh_size = (uint32_t) sh_size; 321 } else { 322 shdr64->sh_addralign = sh_align; 323 shdr64->sh_entsize = sh_entsize; 324 shdr64->sh_offset = sh_offset; 325 shdr64->sh_size = sh_size; 326 } 327 328 updatedescriptor: 329 /* 330 * Update the section descriptor. 331 */ 332 s->s_size = sh_size; 333 s->s_offset = sh_offset; 334 335 return (1); 336 } 337 338 /* 339 * Free a list of extent descriptors. 340 */ 341 342 static void 343 _libelf_release_extents(struct _Elf_Extent_List *extents) 344 { 345 struct _Elf_Extent *ex; 346 347 while ((ex = SLIST_FIRST(extents)) != NULL) { 348 SLIST_REMOVE_HEAD(extents, ex_next); 349 free(ex); 350 } 351 } 352 353 /* 354 * Check if an extent 's' defined by [start..start+size) is free. 355 * This routine assumes that the given extent list is sorted in order 356 * of ascending extent offsets. 357 */ 358 359 static int 360 _libelf_extent_is_unused(struct _Elf_Extent_List *extents, 361 const uint64_t start, const uint64_t size, struct _Elf_Extent **prevt) 362 { 363 uint64_t tmax, tmin; 364 struct _Elf_Extent *t, *pt; 365 const uint64_t smax = start + size; 366 367 /* First, look for overlaps with existing extents. */ 368 pt = NULL; 369 SLIST_FOREACH(t, extents, ex_next) { 370 tmin = t->ex_start; 371 tmax = tmin + t->ex_size; 372 373 if (tmax <= start) { 374 /* 375 * 't' lies entirely before 's': ...| t |...| s |... 376 */ 377 pt = t; 378 continue; 379 } else if (smax <= tmin) { 380 /* 381 * 's' lies entirely before 't', and after 'pt': 382 * ...| pt |...| s |...| t |... 383 */ 384 assert(pt == NULL || 385 pt->ex_start + pt->ex_size <= start); 386 break; 387 } else 388 /* 's' and 't' overlap. */ 389 return (0); 390 } 391 392 if (prevt) 393 *prevt = pt; 394 return (1); 395 } 396 397 /* 398 * Insert an extent into the list of extents. 399 */ 400 401 static int 402 _libelf_insert_extent(struct _Elf_Extent_List *extents, int type, 403 uint64_t start, uint64_t size, void *desc) 404 { 405 struct _Elf_Extent *ex, *prevt; 406 407 assert(type >= ELF_EXTENT_EHDR && type <= ELF_EXTENT_SHDR); 408 409 prevt = NULL; 410 411 /* 412 * If the requested range overlaps with an existing extent, 413 * signal an error. 414 */ 415 if (!_libelf_extent_is_unused(extents, start, size, &prevt)) { 416 LIBELF_SET_ERROR(LAYOUT, 0); 417 return (0); 418 } 419 420 /* Allocate and fill in a new extent descriptor. */ 421 if ((ex = malloc(sizeof(struct _Elf_Extent))) == NULL) { 422 LIBELF_SET_ERROR(RESOURCE, errno); 423 return (0); 424 } 425 ex->ex_start = start; 426 ex->ex_size = size; 427 ex->ex_desc = desc; 428 ex->ex_type = type; 429 430 /* Insert the region descriptor into the list. */ 431 if (prevt) 432 SLIST_INSERT_AFTER(prevt, ex, ex_next); 433 else 434 SLIST_INSERT_HEAD(extents, ex, ex_next); 435 return (1); 436 } 437 438 /* 439 * Recompute section layout. 440 */ 441 442 static off_t 443 _libelf_resync_sections(Elf *e, off_t rc, struct _Elf_Extent_List *extents) 444 { 445 int ec; 446 Elf_Scn *s; 447 size_t sh_type; 448 449 ec = e->e_class; 450 451 /* 452 * Make a pass through sections, computing the extent of each 453 * section. 454 */ 455 STAILQ_FOREACH(s, &e->e_u.e_elf.e_scn, s_next) { 456 if (ec == ELFCLASS32) 457 sh_type = s->s_shdr.s_shdr32.sh_type; 458 else 459 sh_type = s->s_shdr.s_shdr64.sh_type; 460 461 if (sh_type == SHT_NOBITS || sh_type == SHT_NULL) 462 continue; 463 464 if (_libelf_compute_section_extents(e, s, rc) == 0) 465 return ((off_t) -1); 466 467 if (s->s_size == 0) 468 continue; 469 470 if (!_libelf_insert_extent(extents, ELF_EXTENT_SECTION, 471 s->s_offset, s->s_size, s)) 472 return ((off_t) -1); 473 474 if ((size_t) rc < s->s_offset + s->s_size) 475 rc = (off_t) (s->s_offset + s->s_size); 476 } 477 478 return (rc); 479 } 480 481 /* 482 * Recompute the layout of the ELF object and update the internal data 483 * structures associated with the ELF descriptor. 484 * 485 * Returns the size in bytes the ELF object would occupy in its file 486 * representation. 487 * 488 * After a successful call to this function, the following structures 489 * are updated: 490 * 491 * - The ELF header is updated. 492 * - All extents in the ELF object are sorted in order of ascending 493 * addresses. Sections have their section header table entries 494 * updated. An error is signalled if an overlap was detected among 495 * extents. 496 * - Data descriptors associated with sections are checked for valid 497 * types, offsets and alignment. 498 * 499 * After a resync_elf() successfully returns, the ELF descriptor is 500 * ready for being handed over to _libelf_write_elf(). 501 */ 502 503 static off_t 504 _libelf_resync_elf(Elf *e, struct _Elf_Extent_List *extents) 505 { 506 int ec, eh_class; 507 unsigned int eh_byteorder, eh_version; 508 size_t align, fsz; 509 size_t phnum, shnum; 510 off_t rc, phoff, shoff; 511 void *ehdr, *phdr; 512 Elf32_Ehdr *eh32; 513 Elf64_Ehdr *eh64; 514 515 rc = 0; 516 517 ec = e->e_class; 518 519 assert(ec == ELFCLASS32 || ec == ELFCLASS64); 520 521 /* 522 * Prepare the EHDR. 523 */ 524 if ((ehdr = _libelf_ehdr(e, ec, 0)) == NULL) 525 return ((off_t) -1); 526 527 eh32 = ehdr; 528 eh64 = ehdr; 529 530 if (ec == ELFCLASS32) { 531 eh_byteorder = eh32->e_ident[EI_DATA]; 532 eh_class = eh32->e_ident[EI_CLASS]; 533 phoff = (off_t) eh32->e_phoff; 534 shoff = (off_t) eh32->e_shoff; 535 eh_version = eh32->e_version; 536 } else { 537 eh_byteorder = eh64->e_ident[EI_DATA]; 538 eh_class = eh64->e_ident[EI_CLASS]; 539 phoff = (off_t) eh64->e_phoff; 540 shoff = (off_t) eh64->e_shoff; 541 eh_version = eh64->e_version; 542 } 543 544 if (phoff < 0 || shoff < 0) { 545 LIBELF_SET_ERROR(HEADER, 0); 546 return ((off_t) -1); 547 } 548 549 if (eh_version == EV_NONE) 550 eh_version = EV_CURRENT; 551 552 if (eh_version != e->e_version) { /* always EV_CURRENT */ 553 LIBELF_SET_ERROR(VERSION, 0); 554 return ((off_t) -1); 555 } 556 557 if (eh_class != e->e_class) { 558 LIBELF_SET_ERROR(CLASS, 0); 559 return ((off_t) -1); 560 } 561 562 if (e->e_cmd != ELF_C_WRITE && eh_byteorder != e->e_byteorder) { 563 LIBELF_SET_ERROR(HEADER, 0); 564 return ((off_t) -1); 565 } 566 567 shnum = e->e_u.e_elf.e_nscn; 568 phnum = e->e_u.e_elf.e_nphdr; 569 570 e->e_byteorder = eh_byteorder; 571 572 #define INITIALIZE_EHDR(E,EC,V) do { \ 573 unsigned int _version = (unsigned int) (V); \ 574 (E)->e_ident[EI_MAG0] = ELFMAG0; \ 575 (E)->e_ident[EI_MAG1] = ELFMAG1; \ 576 (E)->e_ident[EI_MAG2] = ELFMAG2; \ 577 (E)->e_ident[EI_MAG3] = ELFMAG3; \ 578 (E)->e_ident[EI_CLASS] = (unsigned char) (EC); \ 579 (E)->e_ident[EI_VERSION] = (_version & 0xFFU); \ 580 (E)->e_ehsize = (uint16_t) _libelf_fsize(ELF_T_EHDR, \ 581 (EC), _version, (size_t) 1); \ 582 (E)->e_phentsize = (uint16_t) ((phnum == 0) ? 0 : \ 583 _libelf_fsize(ELF_T_PHDR, (EC), _version, \ 584 (size_t) 1)); \ 585 (E)->e_shentsize = (uint16_t) _libelf_fsize(ELF_T_SHDR, \ 586 (EC), _version, (size_t) 1); \ 587 } while (0) 588 589 if (ec == ELFCLASS32) 590 INITIALIZE_EHDR(eh32, ec, eh_version); 591 else 592 INITIALIZE_EHDR(eh64, ec, eh_version); 593 594 (void) elf_flagehdr(e, ELF_C_SET, ELF_F_DIRTY); 595 596 rc += (off_t) _libelf_fsize(ELF_T_EHDR, ec, eh_version, (size_t) 1); 597 598 if (!_libelf_insert_extent(extents, ELF_EXTENT_EHDR, 0, (uint64_t) rc, 599 ehdr)) 600 return ((off_t) -1); 601 602 /* 603 * Compute the layout the program header table, if one is 604 * present. The program header table needs to be aligned to a 605 * `natural' boundary. 606 */ 607 if (phnum) { 608 fsz = _libelf_fsize(ELF_T_PHDR, ec, eh_version, phnum); 609 align = _libelf_falign(ELF_T_PHDR, ec); 610 611 if (e->e_flags & ELF_F_LAYOUT) { 612 /* 613 * Check offsets for sanity. 614 */ 615 if (rc > phoff) { 616 LIBELF_SET_ERROR(LAYOUT, 0); 617 return ((off_t) -1); 618 } 619 620 if (phoff % (off_t) align) { 621 LIBELF_SET_ERROR(LAYOUT, 0); 622 return ((off_t) -1); 623 } 624 625 } else 626 phoff = roundup(rc, (off_t) align); 627 628 rc = phoff + (off_t) fsz; 629 630 phdr = _libelf_getphdr(e, ec); 631 632 if (!_libelf_insert_extent(extents, ELF_EXTENT_PHDR, 633 (uint64_t) phoff, fsz, phdr)) 634 return ((off_t) -1); 635 } else 636 phoff = 0; 637 638 /* 639 * Compute the layout of the sections associated with the 640 * file. 641 */ 642 643 if (e->e_cmd != ELF_C_WRITE && 644 (e->e_flags & LIBELF_F_SHDRS_LOADED) == 0 && 645 _libelf_load_section_headers(e, ehdr) == 0) 646 return ((off_t) -1); 647 648 if ((rc = _libelf_resync_sections(e, rc, extents)) < 0) 649 return ((off_t) -1); 650 651 /* 652 * Compute the space taken up by the section header table, if 653 * one is needed. 654 * 655 * If ELF_F_LAYOUT has been asserted, the application may have 656 * placed the section header table in between existing 657 * sections, so the net size of the file need not increase due 658 * to the presence of the section header table. 659 * 660 * If the library is responsible for laying out the object, 661 * the section header table is placed after section data. 662 */ 663 if (shnum) { 664 fsz = _libelf_fsize(ELF_T_SHDR, ec, eh_version, shnum); 665 align = _libelf_falign(ELF_T_SHDR, ec); 666 667 if (e->e_flags & ELF_F_LAYOUT) { 668 if (shoff % (off_t) align) { 669 LIBELF_SET_ERROR(LAYOUT, 0); 670 return ((off_t) -1); 671 } 672 } else 673 shoff = roundup(rc, (off_t) align); 674 675 if (shoff + (off_t) fsz > rc) 676 rc = shoff + (off_t) fsz; 677 678 if (!_libelf_insert_extent(extents, ELF_EXTENT_SHDR, 679 (uint64_t) shoff, fsz, NULL)) 680 return ((off_t) -1); 681 } else 682 shoff = 0; 683 684 /* 685 * Set the fields of the Executable Header that could potentially use 686 * extended numbering. 687 */ 688 _libelf_setphnum(e, ehdr, ec, phnum); 689 _libelf_setshnum(e, ehdr, ec, shnum); 690 691 /* 692 * Update the `e_phoff' and `e_shoff' fields if the library is 693 * doing the layout. 694 */ 695 if ((e->e_flags & ELF_F_LAYOUT) == 0) { 696 if (ec == ELFCLASS32) { 697 eh32->e_phoff = (uint32_t) phoff; 698 eh32->e_shoff = (uint32_t) shoff; 699 } else { 700 eh64->e_phoff = (uint64_t) phoff; 701 eh64->e_shoff = (uint64_t) shoff; 702 } 703 } 704 705 return (rc); 706 } 707 708 /* 709 * Write out the contents of an ELF section. 710 */ 711 712 static off_t 713 _libelf_write_scn(Elf *e, unsigned char *nf, struct _Elf_Extent *ex) 714 { 715 int ec; 716 off_t rc; 717 Elf_Scn *s; 718 int elftype; 719 Elf_Data *d, dst; 720 uint32_t sh_type; 721 struct _Libelf_Data *ld; 722 uint64_t sh_off, sh_size; 723 size_t fsz, msz, nobjects; 724 725 assert(ex->ex_type == ELF_EXTENT_SECTION); 726 727 s = ex->ex_desc; 728 rc = (off_t) ex->ex_start; 729 730 if ((ec = e->e_class) == ELFCLASS32) { 731 sh_type = s->s_shdr.s_shdr32.sh_type; 732 sh_size = (uint64_t) s->s_shdr.s_shdr32.sh_size; 733 } else { 734 sh_type = s->s_shdr.s_shdr64.sh_type; 735 sh_size = s->s_shdr.s_shdr64.sh_size; 736 } 737 738 /* 739 * Ignore sections that do not allocate space in the file. 740 */ 741 if (sh_type == SHT_NOBITS || sh_type == SHT_NULL || sh_size == 0) 742 return (rc); 743 744 elftype = _libelf_xlate_shtype(sh_type); 745 assert(elftype >= ELF_T_FIRST && elftype <= ELF_T_LAST); 746 747 sh_off = s->s_offset; 748 assert(sh_off % _libelf_falign(elftype, ec) == 0); 749 750 /* 751 * If the section has a `rawdata' descriptor, and the section 752 * contents have not been modified, use its contents directly. 753 * The `s_rawoff' member contains the offset into the original 754 * file, while `s_offset' contains its new location in the 755 * destination. 756 */ 757 758 if (STAILQ_EMPTY(&s->s_data)) { 759 760 if ((d = elf_rawdata(s, NULL)) == NULL) 761 return ((off_t) -1); 762 763 STAILQ_FOREACH(ld, &s->s_rawdata, d_next) { 764 765 d = &ld->d_data; 766 767 if ((uint64_t) rc < sh_off + d->d_off) 768 (void) memset(nf + rc, 769 LIBELF_PRIVATE(fillchar), 770 (size_t) (sh_off + d->d_off - 771 (uint64_t) rc)); 772 rc = (off_t) (sh_off + d->d_off); 773 774 assert(d->d_buf != NULL); 775 assert(d->d_type == ELF_T_BYTE); 776 assert(d->d_version == e->e_version); 777 778 (void) memcpy(nf + rc, 779 e->e_rawfile + s->s_rawoff + d->d_off, 780 (size_t) d->d_size); 781 782 rc += (off_t) d->d_size; 783 } 784 785 return (rc); 786 } 787 788 /* 789 * Iterate over the set of data descriptors for this section. 790 * The prior call to _libelf_resync_elf() would have setup the 791 * descriptors for this step. 792 */ 793 794 dst.d_version = e->e_version; 795 796 STAILQ_FOREACH(ld, &s->s_data, d_next) { 797 798 d = &ld->d_data; 799 800 msz = _libelf_msize(d->d_type, ec, e->e_version); 801 802 if ((uint64_t) rc < sh_off + d->d_off) 803 (void) memset(nf + rc, 804 LIBELF_PRIVATE(fillchar), 805 (size_t) (sh_off + d->d_off - (uint64_t) rc)); 806 807 rc = (off_t) (sh_off + d->d_off); 808 809 assert(d->d_buf != NULL); 810 assert(d->d_version == e->e_version); 811 assert(msz != 0); 812 assert(d->d_size % msz == 0); 813 814 nobjects = (size_t) (d->d_size / msz); 815 816 fsz = _libelf_fsize(d->d_type, ec, e->e_version, nobjects); 817 818 dst.d_buf = nf + rc; 819 dst.d_size = fsz; 820 821 if (_libelf_xlate(&dst, d, e->e_byteorder, ec, ELF_TOFILE) == 822 NULL) 823 return ((off_t) -1); 824 825 rc += (off_t) fsz; 826 } 827 828 return (rc); 829 } 830 831 /* 832 * Write out an ELF Executable Header. 833 */ 834 835 static off_t 836 _libelf_write_ehdr(Elf *e, unsigned char *nf, struct _Elf_Extent *ex) 837 { 838 int ec; 839 void *ehdr; 840 size_t fsz, msz; 841 Elf_Data dst, src; 842 843 assert(ex->ex_type == ELF_EXTENT_EHDR); 844 assert(ex->ex_start == 0); /* Ehdr always comes first. */ 845 846 ec = e->e_class; 847 848 ehdr = _libelf_ehdr(e, ec, 0); 849 assert(ehdr != NULL); 850 851 fsz = _libelf_fsize(ELF_T_EHDR, ec, e->e_version, (size_t) 1); 852 msz = _libelf_msize(ELF_T_EHDR, ec, e->e_version); 853 854 (void) memset(&dst, 0, sizeof(dst)); 855 (void) memset(&src, 0, sizeof(src)); 856 857 src.d_buf = ehdr; 858 src.d_size = msz; 859 src.d_type = ELF_T_EHDR; 860 src.d_version = dst.d_version = e->e_version; 861 862 dst.d_buf = nf; 863 dst.d_size = fsz; 864 865 if (_libelf_xlate(&dst, &src, e->e_byteorder, ec, ELF_TOFILE) == 866 NULL) 867 return ((off_t) -1); 868 869 return ((off_t) fsz); 870 } 871 872 /* 873 * Write out an ELF program header table. 874 */ 875 876 static off_t 877 _libelf_write_phdr(Elf *e, unsigned char *nf, struct _Elf_Extent *ex) 878 { 879 int ec; 880 void *ehdr; 881 Elf32_Ehdr *eh32; 882 Elf64_Ehdr *eh64; 883 Elf_Data dst, src; 884 size_t fsz, phnum; 885 uint64_t phoff; 886 887 assert(ex->ex_type == ELF_EXTENT_PHDR); 888 889 ec = e->e_class; 890 ehdr = _libelf_ehdr(e, ec, 0); 891 phnum = e->e_u.e_elf.e_nphdr; 892 893 assert(phnum > 0); 894 895 if (ec == ELFCLASS32) { 896 eh32 = (Elf32_Ehdr *) ehdr; 897 phoff = (uint64_t) eh32->e_phoff; 898 } else { 899 eh64 = (Elf64_Ehdr *) ehdr; 900 phoff = eh64->e_phoff; 901 } 902 903 assert(phoff > 0); 904 assert(ex->ex_start == phoff); 905 assert(phoff % _libelf_falign(ELF_T_PHDR, ec) == 0); 906 907 (void) memset(&dst, 0, sizeof(dst)); 908 (void) memset(&src, 0, sizeof(src)); 909 910 fsz = _libelf_fsize(ELF_T_PHDR, ec, e->e_version, phnum); 911 assert(fsz > 0); 912 913 src.d_buf = _libelf_getphdr(e, ec); 914 src.d_version = dst.d_version = e->e_version; 915 src.d_type = ELF_T_PHDR; 916 src.d_size = phnum * _libelf_msize(ELF_T_PHDR, ec, 917 e->e_version); 918 919 dst.d_size = fsz; 920 dst.d_buf = nf + ex->ex_start; 921 922 if (_libelf_xlate(&dst, &src, e->e_byteorder, ec, ELF_TOFILE) == 923 NULL) 924 return ((off_t) -1); 925 926 return ((off_t) (phoff + fsz)); 927 } 928 929 /* 930 * Write out an ELF section header table. 931 */ 932 933 static off_t 934 _libelf_write_shdr(Elf *e, unsigned char *nf, struct _Elf_Extent *ex) 935 { 936 int ec; 937 void *ehdr; 938 Elf_Scn *scn; 939 uint64_t shoff; 940 Elf32_Ehdr *eh32; 941 Elf64_Ehdr *eh64; 942 size_t fsz, nscn; 943 Elf_Data dst, src; 944 945 assert(ex->ex_type == ELF_EXTENT_SHDR); 946 947 ec = e->e_class; 948 ehdr = _libelf_ehdr(e, ec, 0); 949 nscn = e->e_u.e_elf.e_nscn; 950 951 if (ec == ELFCLASS32) { 952 eh32 = (Elf32_Ehdr *) ehdr; 953 shoff = (uint64_t) eh32->e_shoff; 954 } else { 955 eh64 = (Elf64_Ehdr *) ehdr; 956 shoff = eh64->e_shoff; 957 } 958 959 assert(nscn > 0); 960 assert(shoff % _libelf_falign(ELF_T_SHDR, ec) == 0); 961 assert(ex->ex_start == shoff); 962 963 (void) memset(&dst, 0, sizeof(dst)); 964 (void) memset(&src, 0, sizeof(src)); 965 966 src.d_type = ELF_T_SHDR; 967 src.d_size = _libelf_msize(ELF_T_SHDR, ec, e->e_version); 968 src.d_version = dst.d_version = e->e_version; 969 970 fsz = _libelf_fsize(ELF_T_SHDR, ec, e->e_version, (size_t) 1); 971 972 STAILQ_FOREACH(scn, &e->e_u.e_elf.e_scn, s_next) { 973 if (ec == ELFCLASS32) 974 src.d_buf = &scn->s_shdr.s_shdr32; 975 else 976 src.d_buf = &scn->s_shdr.s_shdr64; 977 978 dst.d_size = fsz; 979 dst.d_buf = nf + ex->ex_start + scn->s_ndx * fsz; 980 981 if (_libelf_xlate(&dst, &src, e->e_byteorder, ec, 982 ELF_TOFILE) == NULL) 983 return ((off_t) -1); 984 } 985 986 return ((off_t) (ex->ex_start + nscn * fsz)); 987 } 988 989 /* 990 * Write out the file image. 991 * 992 * The original file could have been mapped in with an ELF_C_RDWR 993 * command and the application could have added new content or 994 * re-arranged its sections before calling elf_update(). Consequently 995 * its not safe to work `in place' on the original file. So we 996 * malloc() the required space for the updated ELF object and build 997 * the object there and write it out to the underlying file at the 998 * end. Note that the application may have opened the underlying file 999 * in ELF_C_RDWR and only retrieved/modified a few sections. We take 1000 * care to avoid translating file sections unnecessarily. 1001 * 1002 * Gaps in the coverage of the file by the file's sections will be 1003 * filled with the fill character set by elf_fill(3). 1004 */ 1005 1006 static off_t 1007 _libelf_write_elf(Elf *e, off_t newsize, struct _Elf_Extent_List *extents) 1008 { 1009 off_t nrc, rc; 1010 Elf_Scn *scn, *tscn; 1011 struct _Elf_Extent *ex; 1012 unsigned char *newfile; 1013 1014 assert(e->e_kind == ELF_K_ELF); 1015 assert(e->e_cmd == ELF_C_RDWR || e->e_cmd == ELF_C_WRITE); 1016 assert(e->e_fd >= 0); 1017 1018 if ((newfile = malloc((size_t) newsize)) == NULL) { 1019 LIBELF_SET_ERROR(RESOURCE, errno); 1020 return ((off_t) -1); 1021 } 1022 1023 nrc = rc = 0; 1024 SLIST_FOREACH(ex, extents, ex_next) { 1025 1026 /* Fill inter-extent gaps. */ 1027 if (ex->ex_start > (size_t) rc) 1028 (void) memset(newfile + rc, LIBELF_PRIVATE(fillchar), 1029 (size_t) (ex->ex_start - (uint64_t) rc)); 1030 1031 switch (ex->ex_type) { 1032 case ELF_EXTENT_EHDR: 1033 if ((nrc = _libelf_write_ehdr(e, newfile, ex)) < 0) 1034 goto error; 1035 break; 1036 1037 case ELF_EXTENT_PHDR: 1038 if ((nrc = _libelf_write_phdr(e, newfile, ex)) < 0) 1039 goto error; 1040 break; 1041 1042 case ELF_EXTENT_SECTION: 1043 if ((nrc = _libelf_write_scn(e, newfile, ex)) < 0) 1044 goto error; 1045 break; 1046 1047 case ELF_EXTENT_SHDR: 1048 if ((nrc = _libelf_write_shdr(e, newfile, ex)) < 0) 1049 goto error; 1050 break; 1051 1052 default: 1053 assert(0); 1054 break; 1055 } 1056 1057 assert(ex->ex_start + ex->ex_size == (size_t) nrc); 1058 assert(rc < nrc); 1059 1060 rc = nrc; 1061 } 1062 1063 assert(rc == newsize); 1064 1065 /* 1066 * For regular files, throw away existing file content and 1067 * unmap any existing mappings. 1068 */ 1069 if ((e->e_flags & LIBELF_F_SPECIAL_FILE) == 0) { 1070 if (ftruncate(e->e_fd, (off_t) 0) < 0 || 1071 lseek(e->e_fd, (off_t) 0, SEEK_SET)) { 1072 LIBELF_SET_ERROR(IO, errno); 1073 goto error; 1074 } 1075 #if ELFTC_HAVE_MMAP 1076 if (e->e_flags & LIBELF_F_RAWFILE_MMAP) { 1077 assert(e->e_rawfile != NULL); 1078 assert(e->e_cmd == ELF_C_RDWR); 1079 if (munmap(e->e_rawfile, e->e_rawsize) < 0) { 1080 LIBELF_SET_ERROR(IO, errno); 1081 goto error; 1082 } 1083 } 1084 #endif 1085 } 1086 1087 /* 1088 * Write out the new contents. 1089 */ 1090 if (write(e->e_fd, newfile, (size_t) newsize) != newsize) { 1091 LIBELF_SET_ERROR(IO, errno); 1092 goto error; 1093 } 1094 1095 /* 1096 * For files opened in ELF_C_RDWR mode, set up the new 'raw' 1097 * contents. 1098 */ 1099 if (e->e_cmd == ELF_C_RDWR) { 1100 assert(e->e_rawfile != NULL); 1101 assert((e->e_flags & LIBELF_F_RAWFILE_MALLOC) || 1102 (e->e_flags & LIBELF_F_RAWFILE_MMAP)); 1103 if (e->e_flags & LIBELF_F_RAWFILE_MALLOC) { 1104 free(e->e_rawfile); 1105 e->e_rawfile = newfile; 1106 newfile = NULL; 1107 } 1108 #if ELFTC_HAVE_MMAP 1109 else if (e->e_flags & LIBELF_F_RAWFILE_MMAP) { 1110 if ((e->e_rawfile = mmap(NULL, (size_t) newsize, 1111 PROT_READ, MAP_PRIVATE, e->e_fd, (off_t) 0)) == 1112 MAP_FAILED) { 1113 LIBELF_SET_ERROR(IO, errno); 1114 goto error; 1115 } 1116 } 1117 #endif /* ELFTC_HAVE_MMAP */ 1118 1119 /* Record the new size of the file. */ 1120 e->e_rawsize = (size_t) newsize; 1121 } else { 1122 /* File opened in ELF_C_WRITE mode. */ 1123 assert(e->e_rawfile == NULL); 1124 } 1125 1126 /* 1127 * Reset flags, remove existing section descriptors and 1128 * {E,P}HDR pointers so that a subsequent elf_get{e,p}hdr() 1129 * and elf_getscn() will function correctly. 1130 */ 1131 1132 e->e_flags &= ~ELF_F_DIRTY; 1133 1134 STAILQ_FOREACH_SAFE(scn, &e->e_u.e_elf.e_scn, s_next, tscn) 1135 _libelf_release_scn(scn); 1136 1137 if (e->e_class == ELFCLASS32) { 1138 free(e->e_u.e_elf.e_ehdr.e_ehdr32); 1139 if (e->e_u.e_elf.e_phdr.e_phdr32) 1140 free(e->e_u.e_elf.e_phdr.e_phdr32); 1141 1142 e->e_u.e_elf.e_ehdr.e_ehdr32 = NULL; 1143 e->e_u.e_elf.e_phdr.e_phdr32 = NULL; 1144 } else { 1145 free(e->e_u.e_elf.e_ehdr.e_ehdr64); 1146 if (e->e_u.e_elf.e_phdr.e_phdr64) 1147 free(e->e_u.e_elf.e_phdr.e_phdr64); 1148 1149 e->e_u.e_elf.e_ehdr.e_ehdr64 = NULL; 1150 e->e_u.e_elf.e_phdr.e_phdr64 = NULL; 1151 } 1152 1153 /* Free the temporary buffer. */ 1154 if (newfile) 1155 free(newfile); 1156 1157 return (rc); 1158 1159 error: 1160 free(newfile); 1161 1162 return ((off_t) -1); 1163 } 1164 1165 /* 1166 * Update an ELF object. 1167 */ 1168 1169 off_t 1170 elf_update(Elf *e, Elf_Cmd c) 1171 { 1172 int ec; 1173 off_t rc; 1174 struct _Elf_Extent_List extents; 1175 1176 rc = (off_t) -1; 1177 1178 if (e == NULL || e->e_kind != ELF_K_ELF || 1179 (c != ELF_C_NULL && c != ELF_C_WRITE)) { 1180 LIBELF_SET_ERROR(ARGUMENT, 0); 1181 return (rc); 1182 } 1183 1184 if ((ec = e->e_class) != ELFCLASS32 && ec != ELFCLASS64) { 1185 LIBELF_SET_ERROR(CLASS, 0); 1186 return (rc); 1187 } 1188 1189 if (e->e_version == EV_NONE) 1190 e->e_version = EV_CURRENT; 1191 1192 if (c == ELF_C_WRITE && e->e_cmd == ELF_C_READ) { 1193 LIBELF_SET_ERROR(MODE, 0); 1194 return (rc); 1195 } 1196 1197 SLIST_INIT(&extents); 1198 1199 if ((rc = _libelf_resync_elf(e, &extents)) < 0) 1200 goto done; 1201 1202 if (c == ELF_C_NULL) 1203 goto done; 1204 1205 if (e->e_fd < 0) { 1206 rc = (off_t) -1; 1207 LIBELF_SET_ERROR(SEQUENCE, 0); 1208 goto done; 1209 } 1210 1211 rc = _libelf_write_elf(e, rc, &extents); 1212 1213 done: 1214 _libelf_release_extents(&extents); 1215 return (rc); 1216 } 1217