elf_update.c
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 #ifndef roundup2 45 #define roundup2(x, y) (((x)+((y)-1))&(~((y)-1))) /* if y is powers of two */ 46 #endif 47 48 ELFTC_VCSID("$Id$"); 49 50 /* 51 * Layout strategy: 52 * 53 * - Case 1: ELF_F_LAYOUT is asserted 54 * In this case the application has full control over where the 55 * section header table, program header table, and section data 56 * will reside. The library only perform error checks. 57 * 58 * - Case 2: ELF_F_LAYOUT is not asserted 59 * 60 * The library will do the object layout using the following 61 * ordering: 62 * - The executable header is placed first, are required by the 63 * ELF specification. 64 * - The program header table is placed immediately following the 65 * executable header. 66 * - Section data, if any, is placed after the program header 67 * table, aligned appropriately. 68 * - The section header table, if needed, is placed last. 69 * 70 * There are two sub-cases to be taken care of: 71 * 72 * - Case 2a: e->e_cmd == ELF_C_READ or ELF_C_RDWR 73 * 74 * In this sub-case, the underlying ELF object may already have 75 * content in it, which the application may have modified. The 76 * library will retrieve content from the existing object as 77 * needed. 78 * 79 * - Case 2b: e->e_cmd == ELF_C_WRITE 80 * 81 * The ELF object is being created afresh in this sub-case; 82 * there is no pre-existing content in the underlying ELF 83 * object. 84 */ 85 86 /* 87 * The types of extents in an ELF object. 88 */ 89 enum elf_extent { 90 ELF_EXTENT_EHDR, 91 ELF_EXTENT_PHDR, 92 ELF_EXTENT_SECTION, 93 ELF_EXTENT_SHDR 94 }; 95 96 /* 97 * A extent descriptor, used when laying out an ELF object. 98 */ 99 struct _Elf_Extent { 100 SLIST_ENTRY(_Elf_Extent) ex_next; 101 uint64_t ex_start; /* Start of the region. */ 102 uint64_t ex_size; /* The size of the region. */ 103 enum elf_extent ex_type; /* Type of region. */ 104 void *ex_desc; /* Associated descriptor. */ 105 }; 106 107 SLIST_HEAD(_Elf_Extent_List, _Elf_Extent); 108 109 /* 110 * Compute the extents of a section, by looking at the data 111 * descriptors associated with it. The function returns 1 112 * if successful, or zero if an error was detected. 113 */ 114 static int 115 _libelf_compute_section_extents(Elf *e, Elf_Scn *s, off_t rc) 116 { 117 Elf_Data *d; 118 size_t fsz, msz; 119 int ec, elftype; 120 uint32_t sh_type; 121 uint64_t d_align; 122 Elf32_Shdr *shdr32; 123 Elf64_Shdr *shdr64; 124 struct _Libelf_Data *ld; 125 uint64_t scn_size, scn_alignment; 126 uint64_t sh_align, sh_entsize, sh_offset, sh_size; 127 128 ec = e->e_class; 129 130 shdr32 = &s->s_shdr.s_shdr32; 131 shdr64 = &s->s_shdr.s_shdr64; 132 if (ec == ELFCLASS32) { 133 sh_type = shdr32->sh_type; 134 sh_align = (uint64_t) shdr32->sh_addralign; 135 sh_entsize = (uint64_t) shdr32->sh_entsize; 136 sh_offset = (uint64_t) shdr32->sh_offset; 137 sh_size = (uint64_t) shdr32->sh_size; 138 } else { 139 sh_type = shdr64->sh_type; 140 sh_align = shdr64->sh_addralign; 141 sh_entsize = shdr64->sh_entsize; 142 sh_offset = shdr64->sh_offset; 143 sh_size = shdr64->sh_size; 144 } 145 146 assert(sh_type != SHT_NULL && sh_type != SHT_NOBITS); 147 148 elftype = _libelf_xlate_shtype(sh_type); 149 if (elftype > ELF_T_LAST) { 150 LIBELF_SET_ERROR(SECTION, 0); 151 return (0); 152 } 153 154 if (sh_align == 0) 155 sh_align = _libelf_falign(elftype, ec); 156 157 /* 158 * Compute the section's size and alignment using the data 159 * descriptors associated with the section. 160 */ 161 if (STAILQ_EMPTY(&s->s_data)) { 162 /* 163 * The section's content (if any) has not been read in 164 * yet. If section is not dirty marked dirty, we can 165 * reuse the values in the 'sh_size' and 'sh_offset' 166 * fields of the section header. 167 */ 168 if ((s->s_flags & ELF_F_DIRTY) == 0) { 169 /* 170 * If the library is doing the layout, then we 171 * compute the new start offset for the 172 * section based on the current offset and the 173 * section's alignment needs. 174 * 175 * If the application is doing the layout, we 176 * can use the value in the 'sh_offset' field 177 * in the section header directly. 178 */ 179 if (e->e_flags & ELF_F_LAYOUT) 180 goto updatedescriptor; 181 else 182 goto computeoffset; 183 } 184 185 /* 186 * Otherwise, we need to bring in the section's data 187 * from the underlying ELF object. 188 */ 189 if (e->e_cmd != ELF_C_WRITE && elf_getdata(s, NULL) == NULL) 190 return (0); 191 } 192 193 /* 194 * Loop through the section's data descriptors. 195 */ 196 scn_size = 0L; 197 scn_alignment = 0; 198 STAILQ_FOREACH(ld, &s->s_data, d_next) { 199 200 d = &ld->d_data; 201 202 /* 203 * The data buffer's type is known. 204 */ 205 if (d->d_type >= ELF_T_NUM) { 206 LIBELF_SET_ERROR(DATA, 0); 207 return (0); 208 } 209 210 /* 211 * The data buffer's version is supported. 212 */ 213 if (d->d_version != e->e_version) { 214 LIBELF_SET_ERROR(VERSION, 0); 215 return (0); 216 } 217 218 /* 219 * The buffer's alignment is non-zero and a power of 220 * two. 221 */ 222 if ((d_align = d->d_align) == 0 || 223 (d_align & (d_align - 1))) { 224 LIBELF_SET_ERROR(DATA, 0); 225 return (0); 226 } 227 228 /* 229 * The buffer's size should be a multiple of the 230 * memory size of the underlying type. 231 */ 232 msz = _libelf_msize(d->d_type, ec, e->e_version); 233 if (d->d_size % msz) { 234 LIBELF_SET_ERROR(DATA, 0); 235 return (0); 236 } 237 238 /* 239 * If the application is controlling layout, then the 240 * d_offset field should be compatible with the 241 * buffer's specified alignment. 242 */ 243 if ((e->e_flags & ELF_F_LAYOUT) && 244 (d->d_off & (d_align - 1))) { 245 LIBELF_SET_ERROR(LAYOUT, 0); 246 return (0); 247 } 248 249 /* 250 * Compute the section's size. 251 */ 252 if (e->e_flags & ELF_F_LAYOUT) { 253 if ((uint64_t) d->d_off + d->d_size > scn_size) 254 scn_size = d->d_off + d->d_size; 255 } else { 256 scn_size = roundup2(scn_size, d->d_align); 257 d->d_off = scn_size; 258 fsz = _libelf_fsize(d->d_type, ec, d->d_version, 259 (size_t) d->d_size / msz); 260 scn_size += fsz; 261 } 262 263 /* 264 * The section's alignment is the maximum alignment 265 * needed for its data buffers. 266 */ 267 if (d_align > scn_alignment) 268 scn_alignment = d_align; 269 } 270 271 272 /* 273 * If the application is requesting full control over the 274 * layout of the section, check the section's specified size, 275 * offsets and alignment for sanity. 276 */ 277 if (e->e_flags & ELF_F_LAYOUT) { 278 if (scn_alignment > sh_align || sh_offset % sh_align || 279 sh_size < scn_size) { 280 LIBELF_SET_ERROR(LAYOUT, 0); 281 return (0); 282 } 283 goto updatedescriptor; 284 } 285 286 /* 287 * Otherwise, compute the values in the section header. 288 * 289 * The section alignment is the maximum alignment for any of 290 * its contained data descriptors. 291 */ 292 if (scn_alignment > sh_align) 293 sh_align = scn_alignment; 294 295 /* 296 * If the section entry size is zero, try and fill in an 297 * appropriate entry size. Per the elf(5) manual page 298 * sections without fixed-size entries should have their 299 * 'sh_entsize' field set to zero. 300 */ 301 if (sh_entsize == 0 && 302 (sh_entsize = _libelf_fsize(elftype, ec, e->e_version, 303 (size_t) 1)) == 1) 304 sh_entsize = 0; 305 306 sh_size = scn_size; 307 308 computeoffset: 309 /* 310 * Compute the new offset for the section based on 311 * the section's alignment needs. 312 */ 313 sh_offset = roundup((uint64_t) rc, sh_align); 314 315 /* 316 * Update the section header. 317 */ 318 if (ec == ELFCLASS32) { 319 shdr32->sh_addralign = (uint32_t) sh_align; 320 shdr32->sh_entsize = (uint32_t) sh_entsize; 321 shdr32->sh_offset = (uint32_t) sh_offset; 322 shdr32->sh_size = (uint32_t) sh_size; 323 } else { 324 shdr64->sh_addralign = sh_align; 325 shdr64->sh_entsize = sh_entsize; 326 shdr64->sh_offset = sh_offset; 327 shdr64->sh_size = sh_size; 328 } 329 330 updatedescriptor: 331 /* 332 * Update the section descriptor. 333 */ 334 s->s_size = sh_size; 335 s->s_offset = sh_offset; 336 337 return (1); 338 } 339 340 /* 341 * Free a list of extent descriptors. 342 */ 343 344 static void 345 _libelf_release_extents(struct _Elf_Extent_List *extents) 346 { 347 struct _Elf_Extent *ex; 348 349 while ((ex = SLIST_FIRST(extents)) != NULL) { 350 SLIST_REMOVE_HEAD(extents, ex_next); 351 free(ex); 352 } 353 } 354 355 /* 356 * Check if an extent 's' defined by [start..start+size) is free. 357 * This routine assumes that the given extent list is sorted in order 358 * of ascending extent offsets. 359 */ 360 361 static int 362 _libelf_extent_is_unused(struct _Elf_Extent_List *extents, 363 const uint64_t start, const uint64_t size, struct _Elf_Extent **prevt) 364 { 365 uint64_t tmax, tmin; 366 struct _Elf_Extent *t, *pt; 367 const uint64_t smax = start + size; 368 369 /* First, look for overlaps with existing extents. */ 370 pt = NULL; 371 SLIST_FOREACH(t, extents, ex_next) { 372 tmin = t->ex_start; 373 tmax = tmin + t->ex_size; 374 375 if (tmax <= start) { 376 /* 377 * 't' lies entirely before 's': ...| t |...| s |... 378 */ 379 pt = t; 380 continue; 381 } else if (smax <= tmin) { 382 /* 383 * 's' lies entirely before 't', and after 'pt': 384 * ...| pt |...| s |...| t |... 385 */ 386 assert(pt == NULL || 387 pt->ex_start + pt->ex_size <= start); 388 break; 389 } else 390 /* 's' and 't' overlap. */ 391 return (0); 392 } 393 394 if (prevt) 395 *prevt = pt; 396 return (1); 397 } 398 399 /* 400 * Insert an extent into the list of extents. 401 */ 402 403 static int 404 _libelf_insert_extent(struct _Elf_Extent_List *extents, int type, 405 uint64_t start, uint64_t size, void *desc) 406 { 407 struct _Elf_Extent *ex, *prevt; 408 409 assert(type >= ELF_EXTENT_EHDR && type <= ELF_EXTENT_SHDR); 410 411 prevt = NULL; 412 413 /* 414 * If the requested range overlaps with an existing extent, 415 * signal an error. 416 */ 417 if (!_libelf_extent_is_unused(extents, start, size, &prevt)) { 418 LIBELF_SET_ERROR(LAYOUT, 0); 419 return (0); 420 } 421 422 /* Allocate and fill in a new extent descriptor. */ 423 if ((ex = malloc(sizeof(struct _Elf_Extent))) == NULL) { 424 LIBELF_SET_ERROR(RESOURCE, errno); 425 return (0); 426 } 427 ex->ex_start = start; 428 ex->ex_size = size; 429 ex->ex_desc = desc; 430 ex->ex_type = type; 431 432 /* Insert the region descriptor into the list. */ 433 if (prevt) 434 SLIST_INSERT_AFTER(prevt, ex, ex_next); 435 else 436 SLIST_INSERT_HEAD(extents, ex, ex_next); 437 return (1); 438 } 439 440 /* 441 * Recompute section layout. 442 */ 443 444 static off_t 445 _libelf_resync_sections(Elf *e, off_t rc, struct _Elf_Extent_List *extents) 446 { 447 int ec; 448 Elf_Scn *s; 449 size_t sh_type; 450 451 ec = e->e_class; 452 453 /* 454 * Make a pass through sections, computing the extent of each 455 * section. 456 */ 457 STAILQ_FOREACH(s, &e->e_u.e_elf.e_scn, s_next) { 458 if (ec == ELFCLASS32) 459 sh_type = s->s_shdr.s_shdr32.sh_type; 460 else 461 sh_type = s->s_shdr.s_shdr64.sh_type; 462 463 if (sh_type == SHT_NOBITS || sh_type == SHT_NULL) 464 continue; 465 466 if (_libelf_compute_section_extents(e, s, rc) == 0) 467 return ((off_t) -1); 468 469 if (s->s_size == 0) 470 continue; 471 472 if (!_libelf_insert_extent(extents, ELF_EXTENT_SECTION, 473 s->s_offset, s->s_size, s)) 474 return ((off_t) -1); 475 476 if ((size_t) rc < s->s_offset + s->s_size) 477 rc = (off_t) (s->s_offset + s->s_size); 478 } 479 480 return (rc); 481 } 482 483 /* 484 * Recompute the layout of the ELF object and update the internal data 485 * structures associated with the ELF descriptor. 486 * 487 * Returns the size in bytes the ELF object would occupy in its file 488 * representation. 489 * 490 * After a successful call to this function, the following structures 491 * are updated: 492 * 493 * - The ELF header is updated. 494 * - All extents in the ELF object are sorted in order of ascending 495 * addresses. Sections have their section header table entries 496 * updated. An error is signalled if an overlap was detected among 497 * extents. 498 * - Data descriptors associated with sections are checked for valid 499 * types, offsets and alignment. 500 * 501 * After a resync_elf() successfully returns, the ELF descriptor is 502 * ready for being handed over to _libelf_write_elf(). 503 */ 504 505 static off_t 506 _libelf_resync_elf(Elf *e, struct _Elf_Extent_List *extents) 507 { 508 int ec, eh_class; 509 unsigned int eh_byteorder, eh_version; 510 size_t align, fsz; 511 size_t phnum, shnum; 512 off_t rc, phoff, shoff; 513 void *ehdr, *phdr; 514 Elf32_Ehdr *eh32; 515 Elf64_Ehdr *eh64; 516 517 rc = 0; 518 519 ec = e->e_class; 520 521 assert(ec == ELFCLASS32 || ec == ELFCLASS64); 522 523 /* 524 * Prepare the EHDR. 525 */ 526 if ((ehdr = _libelf_ehdr(e, ec, 0)) == NULL) 527 return ((off_t) -1); 528 529 eh32 = ehdr; 530 eh64 = ehdr; 531 532 if (ec == ELFCLASS32) { 533 eh_byteorder = eh32->e_ident[EI_DATA]; 534 eh_class = eh32->e_ident[EI_CLASS]; 535 phoff = (off_t) eh32->e_phoff; 536 shoff = (off_t) eh32->e_shoff; 537 eh_version = eh32->e_version; 538 } else { 539 eh_byteorder = eh64->e_ident[EI_DATA]; 540 eh_class = eh64->e_ident[EI_CLASS]; 541 phoff = (off_t) eh64->e_phoff; 542 shoff = (off_t) eh64->e_shoff; 543 eh_version = eh64->e_version; 544 } 545 546 if (phoff < 0 || shoff < 0) { 547 LIBELF_SET_ERROR(HEADER, 0); 548 return ((off_t) -1); 549 } 550 551 if (eh_version == EV_NONE) 552 eh_version = EV_CURRENT; 553 554 if (eh_version != e->e_version) { /* always EV_CURRENT */ 555 LIBELF_SET_ERROR(VERSION, 0); 556 return ((off_t) -1); 557 } 558 559 if (eh_class != e->e_class) { 560 LIBELF_SET_ERROR(CLASS, 0); 561 return ((off_t) -1); 562 } 563 564 if (e->e_cmd != ELF_C_WRITE && eh_byteorder != e->e_byteorder) { 565 LIBELF_SET_ERROR(HEADER, 0); 566 return ((off_t) -1); 567 } 568 569 shnum = e->e_u.e_elf.e_nscn; 570 phnum = e->e_u.e_elf.e_nphdr; 571 572 e->e_byteorder = eh_byteorder; 573 574 #define INITIALIZE_EHDR(E,EC,V) do { \ 575 unsigned int _version = (unsigned int) (V); \ 576 (E)->e_ident[EI_MAG0] = ELFMAG0; \ 577 (E)->e_ident[EI_MAG1] = ELFMAG1; \ 578 (E)->e_ident[EI_MAG2] = ELFMAG2; \ 579 (E)->e_ident[EI_MAG3] = ELFMAG3; \ 580 (E)->e_ident[EI_CLASS] = (unsigned char) (EC); \ 581 (E)->e_ident[EI_VERSION] = (_version & 0xFFU); \ 582 (E)->e_ehsize = (uint16_t) _libelf_fsize(ELF_T_EHDR, \ 583 (EC), _version, (size_t) 1); \ 584 (E)->e_phentsize = (uint16_t) ((phnum == 0) ? 0 : \ 585 _libelf_fsize(ELF_T_PHDR, (EC), _version, \ 586 (size_t) 1)); \ 587 (E)->e_shentsize = (uint16_t) _libelf_fsize(ELF_T_SHDR, \ 588 (EC), _version, (size_t) 1); \ 589 } while (0) 590 591 if (ec == ELFCLASS32) 592 INITIALIZE_EHDR(eh32, ec, eh_version); 593 else 594 INITIALIZE_EHDR(eh64, ec, eh_version); 595 596 (void) elf_flagehdr(e, ELF_C_SET, ELF_F_DIRTY); 597 598 rc += (off_t) _libelf_fsize(ELF_T_EHDR, ec, eh_version, (size_t) 1); 599 600 if (!_libelf_insert_extent(extents, ELF_EXTENT_EHDR, 0, (uint64_t) rc, 601 ehdr)) 602 return ((off_t) -1); 603 604 /* 605 * Compute the layout the program header table, if one is 606 * present. The program header table needs to be aligned to a 607 * `natural' boundary. 608 */ 609 if (phnum) { 610 fsz = _libelf_fsize(ELF_T_PHDR, ec, eh_version, phnum); 611 align = _libelf_falign(ELF_T_PHDR, ec); 612 613 if (e->e_flags & ELF_F_LAYOUT) { 614 /* 615 * Check offsets for sanity. 616 */ 617 if (rc > phoff) { 618 LIBELF_SET_ERROR(LAYOUT, 0); 619 return ((off_t) -1); 620 } 621 622 if (phoff % (off_t) align) { 623 LIBELF_SET_ERROR(LAYOUT, 0); 624 return ((off_t) -1); 625 } 626 627 } else 628 phoff = roundup(rc, (off_t) align); 629 630 rc = phoff + (off_t) fsz; 631 632 phdr = _libelf_getphdr(e, ec); 633 634 if (!_libelf_insert_extent(extents, ELF_EXTENT_PHDR, 635 (uint64_t) phoff, fsz, phdr)) 636 return ((off_t) -1); 637 } else 638 phoff = 0; 639 640 /* 641 * Compute the layout of the sections associated with the 642 * file. 643 */ 644 645 if (e->e_cmd != ELF_C_WRITE && 646 (e->e_flags & LIBELF_F_SHDRS_LOADED) == 0 && 647 _libelf_load_section_headers(e, ehdr) == 0) 648 return ((off_t) -1); 649 650 if ((rc = _libelf_resync_sections(e, rc, extents)) < 0) 651 return ((off_t) -1); 652 653 /* 654 * Compute the space taken up by the section header table, if 655 * one is needed. 656 * 657 * If ELF_F_LAYOUT has been asserted, the application may have 658 * placed the section header table in between existing 659 * sections, so the net size of the file need not increase due 660 * to the presence of the section header table. 661 * 662 * If the library is responsible for laying out the object, 663 * the section header table is placed after section data. 664 */ 665 if (shnum) { 666 fsz = _libelf_fsize(ELF_T_SHDR, ec, eh_version, shnum); 667 align = _libelf_falign(ELF_T_SHDR, ec); 668 669 if (e->e_flags & ELF_F_LAYOUT) { 670 if (shoff % (off_t) align) { 671 LIBELF_SET_ERROR(LAYOUT, 0); 672 return ((off_t) -1); 673 } 674 } else 675 shoff = roundup(rc, (off_t) align); 676 677 if (shoff + (off_t) fsz > rc) 678 rc = shoff + (off_t) fsz; 679 680 if (!_libelf_insert_extent(extents, ELF_EXTENT_SHDR, 681 (uint64_t) shoff, fsz, NULL)) 682 return ((off_t) -1); 683 } else 684 shoff = 0; 685 686 /* 687 * Set the fields of the Executable Header that could potentially use 688 * extended numbering. 689 */ 690 _libelf_setphnum(e, ehdr, ec, phnum); 691 _libelf_setshnum(e, ehdr, ec, shnum); 692 693 /* 694 * Update the `e_phoff' and `e_shoff' fields if the library is 695 * doing the layout. 696 */ 697 if ((e->e_flags & ELF_F_LAYOUT) == 0) { 698 if (ec == ELFCLASS32) { 699 eh32->e_phoff = (uint32_t) phoff; 700 eh32->e_shoff = (uint32_t) shoff; 701 } else { 702 eh64->e_phoff = (uint64_t) phoff; 703 eh64->e_shoff = (uint64_t) shoff; 704 } 705 } 706 707 return (rc); 708 } 709 710 /* 711 * Write out the contents of an ELF section. 712 */ 713 714 static off_t 715 _libelf_write_scn(Elf *e, unsigned char *nf, struct _Elf_Extent *ex) 716 { 717 int ec; 718 off_t rc; 719 Elf_Scn *s; 720 int elftype; 721 Elf_Data *d, dst; 722 uint32_t sh_type; 723 struct _Libelf_Data *ld; 724 uint64_t sh_off, sh_size; 725 size_t fsz, msz, nobjects; 726 727 assert(ex->ex_type == ELF_EXTENT_SECTION); 728 729 s = ex->ex_desc; 730 rc = (off_t) ex->ex_start; 731 732 if ((ec = e->e_class) == ELFCLASS32) { 733 sh_type = s->s_shdr.s_shdr32.sh_type; 734 sh_size = (uint64_t) s->s_shdr.s_shdr32.sh_size; 735 } else { 736 sh_type = s->s_shdr.s_shdr64.sh_type; 737 sh_size = s->s_shdr.s_shdr64.sh_size; 738 } 739 740 /* 741 * Ignore sections that do not allocate space in the file. 742 */ 743 if (sh_type == SHT_NOBITS || sh_type == SHT_NULL || sh_size == 0) 744 return (rc); 745 746 elftype = _libelf_xlate_shtype(sh_type); 747 assert(elftype >= ELF_T_FIRST && elftype <= ELF_T_LAST); 748 749 sh_off = s->s_offset; 750 assert(sh_off % _libelf_falign(elftype, ec) == 0); 751 752 /* 753 * If the section has a `rawdata' descriptor, and the section 754 * contents have not been modified, use its contents directly. 755 * The `s_rawoff' member contains the offset into the original 756 * file, while `s_offset' contains its new location in the 757 * destination. 758 */ 759 760 if (STAILQ_EMPTY(&s->s_data)) { 761 762 if ((d = elf_rawdata(s, NULL)) == NULL) 763 return ((off_t) -1); 764 765 STAILQ_FOREACH(ld, &s->s_rawdata, d_next) { 766 767 d = &ld->d_data; 768 769 if ((uint64_t) rc < sh_off + d->d_off) 770 (void) memset(nf + rc, 771 LIBELF_PRIVATE(fillchar), 772 (size_t) (sh_off + d->d_off - 773 (uint64_t) rc)); 774 rc = (off_t) (sh_off + d->d_off); 775 776 assert(d->d_buf != NULL); 777 assert(d->d_type == ELF_T_BYTE); 778 assert(d->d_version == e->e_version); 779 780 (void) memcpy(nf + rc, 781 e->e_rawfile + s->s_rawoff + d->d_off, 782 (size_t) d->d_size); 783 784 rc += (off_t) d->d_size; 785 } 786 787 return (rc); 788 } 789 790 /* 791 * Iterate over the set of data descriptors for this section. 792 * The prior call to _libelf_resync_elf() would have setup the 793 * descriptors for this step. 794 */ 795 796 dst.d_version = e->e_version; 797 798 STAILQ_FOREACH(ld, &s->s_data, d_next) { 799 800 d = &ld->d_data; 801 802 msz = _libelf_msize(d->d_type, ec, e->e_version); 803 804 if ((uint64_t) rc < sh_off + d->d_off) 805 (void) memset(nf + rc, 806 LIBELF_PRIVATE(fillchar), 807 (size_t) (sh_off + d->d_off - (uint64_t) rc)); 808 809 rc = (off_t) (sh_off + d->d_off); 810 811 assert(d->d_buf != NULL); 812 assert(d->d_version == e->e_version); 813 assert(d->d_size % msz == 0); 814 815 nobjects = (size_t) (d->d_size / msz); 816 817 fsz = _libelf_fsize(d->d_type, ec, e->e_version, nobjects); 818 819 dst.d_buf = nf + rc; 820 dst.d_size = fsz; 821 822 if (_libelf_xlate(&dst, d, e->e_byteorder, ec, ELF_TOFILE) == 823 NULL) 824 return ((off_t) -1); 825 826 rc += (off_t) fsz; 827 } 828 829 return (rc); 830 } 831 832 /* 833 * Write out an ELF Executable Header. 834 */ 835 836 static off_t 837 _libelf_write_ehdr(Elf *e, unsigned char *nf, struct _Elf_Extent *ex) 838 { 839 int ec; 840 void *ehdr; 841 size_t fsz, msz; 842 Elf_Data dst, src; 843 844 assert(ex->ex_type == ELF_EXTENT_EHDR); 845 assert(ex->ex_start == 0); /* Ehdr always comes first. */ 846 847 ec = e->e_class; 848 849 ehdr = _libelf_ehdr(e, ec, 0); 850 assert(ehdr != NULL); 851 852 fsz = _libelf_fsize(ELF_T_EHDR, ec, e->e_version, (size_t) 1); 853 msz = _libelf_msize(ELF_T_EHDR, ec, e->e_version); 854 855 (void) memset(&dst, 0, sizeof(dst)); 856 (void) memset(&src, 0, sizeof(src)); 857 858 src.d_buf = ehdr; 859 src.d_size = msz; 860 src.d_type = ELF_T_EHDR; 861 src.d_version = dst.d_version = e->e_version; 862 863 dst.d_buf = nf; 864 dst.d_size = fsz; 865 866 if (_libelf_xlate(&dst, &src, e->e_byteorder, ec, ELF_TOFILE) == 867 NULL) 868 return ((off_t) -1); 869 870 return ((off_t) fsz); 871 } 872 873 /* 874 * Write out an ELF program header table. 875 */ 876 877 static off_t 878 _libelf_write_phdr(Elf *e, unsigned char *nf, struct _Elf_Extent *ex) 879 { 880 int ec; 881 void *ehdr; 882 Elf32_Ehdr *eh32; 883 Elf64_Ehdr *eh64; 884 Elf_Data dst, src; 885 size_t fsz, phnum; 886 uint64_t phoff; 887 888 assert(ex->ex_type == ELF_EXTENT_PHDR); 889 890 ec = e->e_class; 891 ehdr = _libelf_ehdr(e, ec, 0); 892 phnum = e->e_u.e_elf.e_nphdr; 893 894 assert(phnum > 0); 895 896 if (ec == ELFCLASS32) { 897 eh32 = (Elf32_Ehdr *) ehdr; 898 phoff = (uint64_t) eh32->e_phoff; 899 } else { 900 eh64 = (Elf64_Ehdr *) ehdr; 901 phoff = eh64->e_phoff; 902 } 903 904 assert(phoff > 0); 905 assert(ex->ex_start == phoff); 906 assert(phoff % _libelf_falign(ELF_T_PHDR, ec) == 0); 907 908 (void) memset(&dst, 0, sizeof(dst)); 909 (void) memset(&src, 0, sizeof(src)); 910 911 fsz = _libelf_fsize(ELF_T_PHDR, ec, e->e_version, phnum); 912 assert(fsz > 0); 913 914 src.d_buf = _libelf_getphdr(e, ec); 915 src.d_version = dst.d_version = e->e_version; 916 src.d_type = ELF_T_PHDR; 917 src.d_size = phnum * _libelf_msize(ELF_T_PHDR, ec, 918 e->e_version); 919 920 dst.d_size = fsz; 921 dst.d_buf = nf + ex->ex_start; 922 923 if (_libelf_xlate(&dst, &src, e->e_byteorder, ec, ELF_TOFILE) == 924 NULL) 925 return ((off_t) -1); 926 927 return ((off_t) (phoff + fsz)); 928 } 929 930 /* 931 * Write out an ELF section header table. 932 */ 933 934 static off_t 935 _libelf_write_shdr(Elf *e, unsigned char *nf, struct _Elf_Extent *ex) 936 { 937 int ec; 938 void *ehdr; 939 Elf_Scn *scn; 940 uint64_t shoff; 941 Elf32_Ehdr *eh32; 942 Elf64_Ehdr *eh64; 943 size_t fsz, nscn; 944 Elf_Data dst, src; 945 946 assert(ex->ex_type == ELF_EXTENT_SHDR); 947 948 ec = e->e_class; 949 ehdr = _libelf_ehdr(e, ec, 0); 950 nscn = e->e_u.e_elf.e_nscn; 951 952 if (ec == ELFCLASS32) { 953 eh32 = (Elf32_Ehdr *) ehdr; 954 shoff = (uint64_t) eh32->e_shoff; 955 } else { 956 eh64 = (Elf64_Ehdr *) ehdr; 957 shoff = eh64->e_shoff; 958 } 959 960 assert(nscn > 0); 961 assert(shoff % _libelf_falign(ELF_T_SHDR, ec) == 0); 962 assert(ex->ex_start == shoff); 963 964 (void) memset(&dst, 0, sizeof(dst)); 965 (void) memset(&src, 0, sizeof(src)); 966 967 src.d_type = ELF_T_SHDR; 968 src.d_size = _libelf_msize(ELF_T_SHDR, ec, e->e_version); 969 src.d_version = dst.d_version = e->e_version; 970 971 fsz = _libelf_fsize(ELF_T_SHDR, ec, e->e_version, (size_t) 1); 972 973 STAILQ_FOREACH(scn, &e->e_u.e_elf.e_scn, s_next) { 974 if (ec == ELFCLASS32) 975 src.d_buf = &scn->s_shdr.s_shdr32; 976 else 977 src.d_buf = &scn->s_shdr.s_shdr64; 978 979 dst.d_size = fsz; 980 dst.d_buf = nf + ex->ex_start + scn->s_ndx * fsz; 981 982 if (_libelf_xlate(&dst, &src, e->e_byteorder, ec, 983 ELF_TOFILE) == NULL) 984 return ((off_t) -1); 985 } 986 987 return ((off_t) (ex->ex_start + nscn * fsz)); 988 } 989 990 /* 991 * Write out the file image. 992 * 993 * The original file could have been mapped in with an ELF_C_RDWR 994 * command and the application could have added new content or 995 * re-arranged its sections before calling elf_update(). Consequently 996 * its not safe to work `in place' on the original file. So we 997 * malloc() the required space for the updated ELF object and build 998 * the object there and write it out to the underlying file at the 999 * end. Note that the application may have opened the underlying file 1000 * in ELF_C_RDWR and only retrieved/modified a few sections. We take 1001 * care to avoid translating file sections unnecessarily. 1002 * 1003 * Gaps in the coverage of the file by the file's sections will be 1004 * filled with the fill character set by elf_fill(3). 1005 */ 1006 1007 static off_t 1008 _libelf_write_elf(Elf *e, off_t newsize, struct _Elf_Extent_List *extents) 1009 { 1010 off_t nrc, rc; 1011 Elf_Scn *scn, *tscn; 1012 struct _Elf_Extent *ex; 1013 unsigned char *newfile; 1014 1015 assert(e->e_kind == ELF_K_ELF); 1016 assert(e->e_cmd == ELF_C_RDWR || e->e_cmd == ELF_C_WRITE); 1017 assert(e->e_fd >= 0); 1018 1019 if ((newfile = malloc((size_t) newsize)) == NULL) { 1020 LIBELF_SET_ERROR(RESOURCE, errno); 1021 return ((off_t) -1); 1022 } 1023 1024 nrc = rc = 0; 1025 SLIST_FOREACH(ex, extents, ex_next) { 1026 1027 /* Fill inter-extent gaps. */ 1028 if (ex->ex_start > (size_t) rc) 1029 (void) memset(newfile + rc, LIBELF_PRIVATE(fillchar), 1030 (size_t) (ex->ex_start - (uint64_t) rc)); 1031 1032 switch (ex->ex_type) { 1033 case ELF_EXTENT_EHDR: 1034 if ((nrc = _libelf_write_ehdr(e, newfile, ex)) < 0) 1035 goto error; 1036 break; 1037 1038 case ELF_EXTENT_PHDR: 1039 if ((nrc = _libelf_write_phdr(e, newfile, ex)) < 0) 1040 goto error; 1041 break; 1042 1043 case ELF_EXTENT_SECTION: 1044 if ((nrc = _libelf_write_scn(e, newfile, ex)) < 0) 1045 goto error; 1046 break; 1047 1048 case ELF_EXTENT_SHDR: 1049 if ((nrc = _libelf_write_shdr(e, newfile, ex)) < 0) 1050 goto error; 1051 break; 1052 1053 default: 1054 assert(0); 1055 break; 1056 } 1057 1058 assert(ex->ex_start + ex->ex_size == (size_t) nrc); 1059 assert(rc < nrc); 1060 1061 rc = nrc; 1062 } 1063 1064 assert(rc == newsize); 1065 1066 /* 1067 * For regular files, throw away existing file content and 1068 * unmap any existing mappings. 1069 */ 1070 if ((e->e_flags & LIBELF_F_SPECIAL_FILE) == 0) { 1071 if (ftruncate(e->e_fd, (off_t) 0) < 0 || 1072 lseek(e->e_fd, (off_t) 0, SEEK_SET)) { 1073 LIBELF_SET_ERROR(IO, errno); 1074 goto error; 1075 } 1076 #if ELFTC_HAVE_MMAP 1077 if (e->e_flags & LIBELF_F_RAWFILE_MMAP) { 1078 assert(e->e_rawfile != NULL); 1079 assert(e->e_cmd == ELF_C_RDWR); 1080 if (munmap(e->e_rawfile, e->e_rawsize) < 0) { 1081 LIBELF_SET_ERROR(IO, errno); 1082 goto error; 1083 } 1084 } 1085 #endif 1086 } 1087 1088 /* 1089 * Write out the new contents. 1090 */ 1091 if (write(e->e_fd, newfile, (size_t) newsize) != newsize) { 1092 LIBELF_SET_ERROR(IO, errno); 1093 goto error; 1094 } 1095 1096 /* 1097 * For files opened in ELF_C_RDWR mode, set up the new 'raw' 1098 * contents. 1099 */ 1100 if (e->e_cmd == ELF_C_RDWR) { 1101 assert(e->e_rawfile != NULL); 1102 assert((e->e_flags & LIBELF_F_RAWFILE_MALLOC) || 1103 (e->e_flags & LIBELF_F_RAWFILE_MMAP)); 1104 if (e->e_flags & LIBELF_F_RAWFILE_MALLOC) { 1105 free(e->e_rawfile); 1106 e->e_rawfile = newfile; 1107 newfile = NULL; 1108 } 1109 #if ELFTC_HAVE_MMAP 1110 else if (e->e_flags & LIBELF_F_RAWFILE_MMAP) { 1111 if ((e->e_rawfile = mmap(NULL, (size_t) newsize, 1112 PROT_READ, MAP_PRIVATE, e->e_fd, (off_t) 0)) == 1113 MAP_FAILED) { 1114 LIBELF_SET_ERROR(IO, errno); 1115 goto error; 1116 } 1117 } 1118 #endif /* ELFTC_HAVE_MMAP */ 1119 1120 /* Record the new size of the file. */ 1121 e->e_rawsize = (size_t) newsize; 1122 } else { 1123 /* File opened in ELF_C_WRITE mode. */ 1124 assert(e->e_rawfile == NULL); 1125 } 1126 1127 /* 1128 * Reset flags, remove existing section descriptors and 1129 * {E,P}HDR pointers so that a subsequent elf_get{e,p}hdr() 1130 * and elf_getscn() will function correctly. 1131 */ 1132 1133 e->e_flags &= ~ELF_F_DIRTY; 1134 1135 STAILQ_FOREACH_SAFE(scn, &e->e_u.e_elf.e_scn, s_next, tscn) 1136 _libelf_release_scn(scn); 1137 1138 if (e->e_class == ELFCLASS32) { 1139 free(e->e_u.e_elf.e_ehdr.e_ehdr32); 1140 if (e->e_u.e_elf.e_phdr.e_phdr32) 1141 free(e->e_u.e_elf.e_phdr.e_phdr32); 1142 1143 e->e_u.e_elf.e_ehdr.e_ehdr32 = NULL; 1144 e->e_u.e_elf.e_phdr.e_phdr32 = NULL; 1145 } else { 1146 free(e->e_u.e_elf.e_ehdr.e_ehdr64); 1147 if (e->e_u.e_elf.e_phdr.e_phdr64) 1148 free(e->e_u.e_elf.e_phdr.e_phdr64); 1149 1150 e->e_u.e_elf.e_ehdr.e_ehdr64 = NULL; 1151 e->e_u.e_elf.e_phdr.e_phdr64 = NULL; 1152 } 1153 1154 /* Free the temporary buffer. */ 1155 if (newfile) 1156 free(newfile); 1157 1158 return (rc); 1159 1160 error: 1161 free(newfile); 1162 1163 return ((off_t) -1); 1164 } 1165 1166 /* 1167 * Update an ELF object. 1168 */ 1169 1170 off_t 1171 elf_update(Elf *e, Elf_Cmd c) 1172 { 1173 int ec; 1174 off_t rc; 1175 struct _Elf_Extent_List extents; 1176 1177 rc = (off_t) -1; 1178 1179 if (e == NULL || e->e_kind != ELF_K_ELF || 1180 (c != ELF_C_NULL && c != ELF_C_WRITE)) { 1181 LIBELF_SET_ERROR(ARGUMENT, 0); 1182 return (rc); 1183 } 1184 1185 if ((ec = e->e_class) != ELFCLASS32 && ec != ELFCLASS64) { 1186 LIBELF_SET_ERROR(CLASS, 0); 1187 return (rc); 1188 } 1189 1190 if (e->e_version == EV_NONE) 1191 e->e_version = EV_CURRENT; 1192 1193 if (c == ELF_C_WRITE && e->e_cmd == ELF_C_READ) { 1194 LIBELF_SET_ERROR(MODE, 0); 1195 return (rc); 1196 } 1197 1198 SLIST_INIT(&extents); 1199 1200 if ((rc = _libelf_resync_elf(e, &extents)) < 0) 1201 goto done; 1202 1203 if (c == ELF_C_NULL) 1204 goto done; 1205 1206 if (e->e_fd < 0) { 1207 rc = (off_t) -1; 1208 LIBELF_SET_ERROR(SEQUENCE, 0); 1209 goto done; 1210 } 1211 1212 rc = _libelf_write_elf(e, rc, &extents); 1213 1214 done: 1215 _libelf_release_extents(&extents); 1216 return (rc); 1217 }