1 /* $NetBSD: elf_update.c,v 1.2 2014/03/09 16:58:04 christos Exp $ */ 2 3 /*- 4 * Copyright (c) 2006-2011 Joseph Koshy 5 * All rights reserved. 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 1. Redistributions of source code must retain the above copyright 11 * notice, this list of conditions and the following disclaimer. 12 * 2. Redistributions in binary form must reproduce the above copyright 13 * notice, this list of conditions and the following disclaimer in the 14 * documentation and/or other materials provided with the distribution. 15 * 16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 17 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 20 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26 * SUCH DAMAGE. 27 */ 28 29 #if HAVE_NBTOOL_CONFIG_H 30 # include "nbtool_config.h" 31 #endif 32 33 #include <sys/param.h> 34 #include <sys/stat.h> 35 36 #include <assert.h> 37 #include <errno.h> 38 #include <gelf.h> 39 #include <libelf.h> 40 #include <stdlib.h> 41 #include <string.h> 42 #include <unistd.h> 43 44 #include "_libelf.h" 45 46 #if ELFTC_HAVE_MMAP 47 #include <sys/mman.h> 48 #endif 49 50 __RCSID("$NetBSD: elf_update.c,v 1.2 2014/03/09 16:58:04 christos Exp $"); 51 ELFTC_VCSID("Id: elf_update.c 2931 2013-03-23 11:41:07Z jkoshy "); 52 53 /* 54 * Layout strategy: 55 * 56 * - Case 1: ELF_F_LAYOUT is asserted 57 * In this case the application has full control over where the 58 * section header table, program header table, and section data 59 * will reside. The library only perform error checks. 60 * 61 * - Case 2: ELF_F_LAYOUT is not asserted 62 * 63 * The library will do the object layout using the following 64 * ordering: 65 * - The executable header is placed first, are required by the 66 * ELF specification. 67 * - The program header table is placed immediately following the 68 * executable header. 69 * - Section data, if any, is placed after the program header 70 * table, aligned appropriately. 71 * - The section header table, if needed, is placed last. 72 * 73 * There are two sub-cases to be taken care of: 74 * 75 * - Case 2a: e->e_cmd == ELF_C_READ or ELF_C_RDWR 76 * 77 * In this sub-case, the underlying ELF object may already have 78 * content in it, which the application may have modified. The 79 * library will retrieve content from the existing object as 80 * needed. 81 * 82 * - Case 2b: e->e_cmd == ELF_C_WRITE 83 * 84 * The ELF object is being created afresh in this sub-case; 85 * there is no pre-existing content in the underlying ELF 86 * object. 87 */ 88 89 /* 90 * The types of extents in an ELF object. 91 */ 92 enum elf_extent { 93 ELF_EXTENT_EHDR, 94 ELF_EXTENT_PHDR, 95 ELF_EXTENT_SECTION, 96 ELF_EXTENT_SHDR 97 }; 98 99 /* 100 * A extent descriptor, used when laying out an ELF object. 101 */ 102 struct _Elf_Extent { 103 SLIST_ENTRY(_Elf_Extent) ex_next; 104 uint64_t ex_start; /* Start of the region. */ 105 uint64_t ex_size; /* The size of the region. */ 106 enum elf_extent ex_type; /* Type of region. */ 107 void *ex_desc; /* Associated descriptor. */ 108 }; 109 110 SLIST_HEAD(_Elf_Extent_List, _Elf_Extent); 111 112 /* 113 * Compute the extents of a section, by looking at the data 114 * descriptors associated with it. The function returns 1 115 * if successful, or zero if an error was detected. 116 */ 117 static int 118 _libelf_compute_section_extents(Elf *e, Elf_Scn *s, off_t rc) 119 { 120 int ec; 121 Elf_Data *d; 122 size_t fsz, msz; 123 uint32_t sh_type; 124 uint64_t d_align; 125 Elf32_Shdr *shdr32; 126 Elf64_Shdr *shdr64; 127 unsigned int elftype; 128 struct _Libelf_Data *ld; 129 uint64_t scn_size, scn_alignment; 130 uint64_t sh_align, sh_entsize, sh_offset, sh_size; 131 132 ec = e->e_class; 133 134 shdr32 = &s->s_shdr.s_shdr32; 135 shdr64 = &s->s_shdr.s_shdr64; 136 if (ec == ELFCLASS32) { 137 sh_type = shdr32->sh_type; 138 sh_align = (uint64_t) shdr32->sh_addralign; 139 sh_entsize = (uint64_t) shdr32->sh_entsize; 140 sh_offset = (uint64_t) shdr32->sh_offset; 141 sh_size = (uint64_t) shdr32->sh_size; 142 } else { 143 sh_type = shdr64->sh_type; 144 sh_align = shdr64->sh_addralign; 145 sh_entsize = shdr64->sh_entsize; 146 sh_offset = shdr64->sh_offset; 147 sh_size = shdr64->sh_size; 148 } 149 150 assert(sh_type != SHT_NULL && sh_type != SHT_NOBITS); 151 152 elftype = _libelf_xlate_shtype(sh_type); 153 if (elftype > ELF_T_LAST) { 154 LIBELF_SET_ERROR(SECTION, 0); 155 return (0); 156 } 157 158 if (sh_align == 0) 159 sh_align = _libelf_falign(elftype, ec); 160 161 /* 162 * Compute the section's size and alignment using the data 163 * descriptors associated with the section. 164 */ 165 if (STAILQ_EMPTY(&s->s_data)) { 166 /* 167 * The section's content (if any) has not been read in 168 * yet. If section is not dirty marked dirty, we can 169 * reuse the values in the 'sh_size' and 'sh_offset' 170 * fields of the section header. 171 */ 172 if ((s->s_flags & ELF_F_DIRTY) == 0) { 173 /* 174 * If the library is doing the layout, then we 175 * compute the new start offset for the 176 * section based on the current offset and the 177 * section's alignment needs. 178 * 179 * If the application is doing the layout, we 180 * can use the value in the 'sh_offset' field 181 * in the section header directly. 182 */ 183 if (e->e_flags & ELF_F_LAYOUT) 184 goto updatedescriptor; 185 else 186 goto computeoffset; 187 } 188 189 /* 190 * Otherwise, we need to bring in the section's data 191 * from the underlying ELF object. 192 */ 193 if (e->e_cmd != ELF_C_WRITE && elf_getdata(s, NULL) == NULL) 194 return (0); 195 } 196 197 /* 198 * Loop through the section's data descriptors. 199 */ 200 scn_size = 0L; 201 scn_alignment = 0; 202 STAILQ_FOREACH(ld, &s->s_data, d_next) { 203 204 d = &ld->d_data; 205 206 /* 207 * The data buffer's type is known. 208 */ 209 if (d->d_type >= ELF_T_NUM) { 210 LIBELF_SET_ERROR(DATA, 0); 211 return (0); 212 } 213 214 /* 215 * The data buffer's version is supported. 216 */ 217 if (d->d_version != e->e_version) { 218 LIBELF_SET_ERROR(VERSION, 0); 219 return (0); 220 } 221 222 /* 223 * The buffer's alignment is non-zero and a power of 224 * two. 225 */ 226 if ((d_align = d->d_align) == 0 || 227 (d_align & (d_align - 1))) { 228 LIBELF_SET_ERROR(DATA, 0); 229 return (0); 230 } 231 232 /* 233 * The buffer's size should be a multiple of the 234 * memory size of the underlying type. 235 */ 236 msz = _libelf_msize(d->d_type, ec, e->e_version); 237 if (d->d_size % msz) { 238 LIBELF_SET_ERROR(DATA, 0); 239 return (0); 240 } 241 242 /* 243 * If the application is controlling layout, then the 244 * d_offset field should be compatible with the 245 * buffer's specified alignment. 246 */ 247 if ((e->e_flags & ELF_F_LAYOUT) && 248 (d->d_off & (d_align - 1))) { 249 LIBELF_SET_ERROR(LAYOUT, 0); 250 return (0); 251 } 252 253 /* 254 * Compute the section's size. 255 */ 256 if (e->e_flags & ELF_F_LAYOUT) { 257 if ((uint64_t) d->d_off + d->d_size > scn_size) 258 scn_size = d->d_off + d->d_size; 259 } else { 260 scn_size = roundup2(scn_size, d->d_align); 261 d->d_off = scn_size; 262 fsz = _libelf_fsize(d->d_type, ec, d->d_version, 263 d->d_size / msz); 264 scn_size += fsz; 265 } 266 267 /* 268 * The section's alignment is the maximum alignment 269 * needed for its data buffers. 270 */ 271 if (d_align > scn_alignment) 272 scn_alignment = d_align; 273 } 274 275 276 /* 277 * If the application is requesting full control over the 278 * layout of the section, check the section's specified size, 279 * offsets and alignment for sanity. 280 */ 281 if (e->e_flags & ELF_F_LAYOUT) { 282 if (scn_alignment > sh_align || sh_offset % sh_align || 283 sh_size < scn_size) { 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(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 STAILQ_FOREACH(s, &e->e_u.e_elf.e_scn, s_next) { 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 = 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 = (uint64_t) eh32->e_phoff; 540 shoff = (uint64_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 = eh64->e_phoff; 546 shoff = eh64->e_shoff; 547 eh_version = eh64->e_version; 548 } 549 550 if (eh_version == EV_NONE) 551 eh_version = EV_CURRENT; 552 553 if (eh_version != e->e_version) { /* always EV_CURRENT */ 554 LIBELF_SET_ERROR(VERSION, 0); 555 return ((off_t) -1); 556 } 557 558 if (eh_class != e->e_class) { 559 LIBELF_SET_ERROR(CLASS, 0); 560 return ((off_t) -1); 561 } 562 563 if (e->e_cmd != ELF_C_WRITE && eh_byteorder != e->e_byteorder) { 564 LIBELF_SET_ERROR(HEADER, 0); 565 return ((off_t) -1); 566 } 567 568 shnum = e->e_u.e_elf.e_nscn; 569 phnum = e->e_u.e_elf.e_nphdr; 570 571 e->e_byteorder = eh_byteorder; 572 573 #define INITIALIZE_EHDR(E,EC,V) do { \ 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] = (EC); \ 579 (E)->e_ident[EI_VERSION] = (V); \ 580 (E)->e_ehsize = _libelf_fsize(ELF_T_EHDR, (EC), (V), \ 581 (size_t) 1); \ 582 (E)->e_phentsize = (phnum == 0) ? 0 : _libelf_fsize( \ 583 ELF_T_PHDR, (EC), (V), (size_t) 1); \ 584 (E)->e_shentsize = _libelf_fsize(ELF_T_SHDR, (EC), (V), \ 585 (size_t) 1); \ 586 } while (/*CONSTCOND*/0) 587 588 if (ec == ELFCLASS32) 589 INITIALIZE_EHDR(eh32, ec, eh_version); 590 else 591 INITIALIZE_EHDR(eh64, ec, eh_version); 592 593 (void) elf_flagehdr(e, ELF_C_SET, ELF_F_DIRTY); 594 595 rc += _libelf_fsize(ELF_T_EHDR, ec, eh_version, (size_t) 1); 596 597 if (!_libelf_insert_extent(extents, ELF_EXTENT_EHDR, 0, rc, ehdr)) 598 return ((off_t) -1); 599 600 /* 601 * Compute the layout the program header table, if one is 602 * present. The program header table needs to be aligned to a 603 * `natural' boundary. 604 */ 605 if (phnum) { 606 fsz = _libelf_fsize(ELF_T_PHDR, ec, eh_version, phnum); 607 align = _libelf_falign(ELF_T_PHDR, ec); 608 609 if (e->e_flags & ELF_F_LAYOUT) { 610 /* 611 * Check offsets for sanity. 612 */ 613 if (rc > phoff) { 614 LIBELF_SET_ERROR(LAYOUT, 0); 615 return ((off_t) -1); 616 } 617 618 if (phoff % align) { 619 LIBELF_SET_ERROR(LAYOUT, 0); 620 return ((off_t) -1); 621 } 622 623 } else 624 phoff = roundup(rc, align); 625 626 rc = phoff + fsz; 627 628 phdr = _libelf_getphdr(e, ec); 629 630 if (!_libelf_insert_extent(extents, ELF_EXTENT_PHDR, phoff, 631 fsz, phdr)) 632 return ((off_t) -1); 633 } else 634 phoff = 0; 635 636 /* 637 * Compute the layout of the sections associated with the 638 * file. 639 */ 640 641 if (e->e_cmd != ELF_C_WRITE && 642 (e->e_flags & LIBELF_F_SHDRS_LOADED) == 0 && 643 _libelf_load_section_headers(e, ehdr) == 0) 644 return ((off_t) -1); 645 646 if ((rc = _libelf_resync_sections(e, rc, extents)) < 0) 647 return ((off_t) -1); 648 649 /* 650 * Compute the space taken up by the section header table, if 651 * one is needed. 652 * 653 * If ELF_F_LAYOUT has been asserted, the application may have 654 * placed the section header table in between existing 655 * sections, so the net size of the file need not increase due 656 * to the presence of the section header table. 657 * 658 * If the library is responsible for laying out the object, 659 * the section header table is placed after section data. 660 */ 661 if (shnum) { 662 fsz = _libelf_fsize(ELF_T_SHDR, ec, eh_version, shnum); 663 align = _libelf_falign(ELF_T_SHDR, ec); 664 665 if (e->e_flags & ELF_F_LAYOUT) { 666 if (shoff % align) { 667 LIBELF_SET_ERROR(LAYOUT, 0); 668 return ((off_t) -1); 669 } 670 } else 671 shoff = roundup(rc, align); 672 673 if (shoff + fsz > (size_t) rc) 674 rc = shoff + fsz; 675 676 if (!_libelf_insert_extent(extents, ELF_EXTENT_SHDR, shoff, 677 fsz, NULL)) 678 return ((off_t) -1); 679 } else 680 shoff = 0; 681 682 /* 683 * Set the fields of the Executable Header that could potentially use 684 * extended numbering. 685 */ 686 _libelf_setphnum(e, ehdr, ec, phnum); 687 _libelf_setshnum(e, ehdr, ec, shnum); 688 689 /* 690 * Update the `e_phoff' and `e_shoff' fields if the library is 691 * doing the layout. 692 */ 693 if ((e->e_flags & ELF_F_LAYOUT) == 0) { 694 if (ec == ELFCLASS32) { 695 eh32->e_phoff = (uint32_t) phoff; 696 eh32->e_shoff = (uint32_t) shoff; 697 } else { 698 eh64->e_phoff = (uint64_t) phoff; 699 eh64->e_shoff = (uint64_t) shoff; 700 } 701 } 702 703 return (rc); 704 } 705 706 /* 707 * Write out the contents of an ELF section. 708 */ 709 710 static size_t 711 _libelf_write_scn(Elf *e, char *nf, struct _Elf_Extent *ex) 712 { 713 int ec; 714 Elf_Scn *s; 715 int elftype; 716 Elf_Data *d, dst; 717 uint32_t sh_type; 718 struct _Libelf_Data *ld; 719 uint64_t sh_off, sh_size; 720 size_t fsz, msz, nobjects, rc; 721 722 assert(ex->ex_type == ELF_EXTENT_SECTION); 723 724 s = ex->ex_desc; 725 rc = ex->ex_start; 726 727 if ((ec = e->e_class) == ELFCLASS32) { 728 sh_type = s->s_shdr.s_shdr32.sh_type; 729 sh_size = (uint64_t) s->s_shdr.s_shdr32.sh_size; 730 } else { 731 sh_type = s->s_shdr.s_shdr64.sh_type; 732 sh_size = s->s_shdr.s_shdr64.sh_size; 733 } 734 735 /* 736 * Ignore sections that do not allocate space in the file. 737 */ 738 if (sh_type == SHT_NOBITS || sh_type == SHT_NULL || sh_size == 0) 739 return (rc); 740 741 elftype = _libelf_xlate_shtype(sh_type); 742 assert(elftype >= ELF_T_FIRST && elftype <= ELF_T_LAST); 743 744 sh_off = s->s_offset; 745 assert(sh_off % _libelf_falign(elftype, ec) == 0); 746 747 /* 748 * If the section has a `rawdata' descriptor, and the section 749 * contents have not been modified, use its contents directly. 750 * The `s_rawoff' member contains the offset into the original 751 * file, while `s_offset' contains its new location in the 752 * destination. 753 */ 754 755 if (STAILQ_EMPTY(&s->s_data)) { 756 757 if ((d = elf_rawdata(s, NULL)) == NULL) 758 return ((off_t) -1); 759 760 STAILQ_FOREACH(ld, &s->s_rawdata, d_next) { 761 762 d = &ld->d_data; 763 764 if ((uint64_t) rc < sh_off + d->d_off) 765 (void) memset(nf + rc, 766 LIBELF_PRIVATE(fillchar), sh_off + 767 d->d_off - rc); 768 rc = sh_off + d->d_off; 769 770 assert(d->d_buf != NULL); 771 assert(d->d_type == ELF_T_BYTE); 772 assert(d->d_version == e->e_version); 773 774 (void) memcpy(nf + rc, 775 e->e_rawfile + s->s_rawoff + d->d_off, d->d_size); 776 777 rc += d->d_size; 778 } 779 780 return (rc); 781 } 782 783 /* 784 * Iterate over the set of data descriptors for this section. 785 * The prior call to _libelf_resync_elf() would have setup the 786 * descriptors for this step. 787 */ 788 789 dst.d_version = e->e_version; 790 791 STAILQ_FOREACH(ld, &s->s_data, d_next) { 792 793 d = &ld->d_data; 794 795 msz = _libelf_msize(d->d_type, ec, e->e_version); 796 797 if ((uint64_t) rc < sh_off + d->d_off) 798 (void) memset(nf + rc, 799 LIBELF_PRIVATE(fillchar), sh_off + d->d_off - rc); 800 801 rc = sh_off + d->d_off; 802 803 assert(d->d_buf != NULL); 804 assert(d->d_version == e->e_version); 805 assert(d->d_size % msz == 0); 806 807 nobjects = d->d_size / msz; 808 809 fsz = _libelf_fsize(d->d_type, ec, e->e_version, nobjects); 810 811 dst.d_buf = nf + rc; 812 dst.d_size = fsz; 813 814 if (_libelf_xlate(&dst, d, e->e_byteorder, ec, ELF_TOFILE) == 815 NULL) 816 return ((off_t) -1); 817 818 rc += fsz; 819 } 820 821 return ((off_t) rc); 822 } 823 824 /* 825 * Write out an ELF Executable Header. 826 */ 827 828 static off_t 829 _libelf_write_ehdr(Elf *e, char *nf, struct _Elf_Extent *ex) 830 { 831 int ec; 832 void *ehdr; 833 size_t fsz, msz; 834 Elf_Data dst, src; 835 836 assert(ex->ex_type == ELF_EXTENT_EHDR); 837 assert(ex->ex_start == 0); /* Ehdr always comes first. */ 838 839 ec = e->e_class; 840 841 ehdr = _libelf_ehdr(e, ec, 0); 842 assert(ehdr != NULL); 843 844 fsz = _libelf_fsize(ELF_T_EHDR, ec, e->e_version, (size_t) 1); 845 msz = _libelf_msize(ELF_T_EHDR, ec, e->e_version); 846 847 (void) memset(&dst, 0, sizeof(dst)); 848 (void) memset(&src, 0, sizeof(src)); 849 850 src.d_buf = ehdr; 851 src.d_size = msz; 852 src.d_type = ELF_T_EHDR; 853 src.d_version = dst.d_version = e->e_version; 854 855 dst.d_buf = nf; 856 dst.d_size = fsz; 857 858 if (_libelf_xlate(&dst, &src, e->e_byteorder, ec, ELF_TOFILE) == 859 NULL) 860 return ((off_t) -1); 861 862 return ((off_t) fsz); 863 } 864 865 /* 866 * Write out an ELF program header table. 867 */ 868 869 static off_t 870 _libelf_write_phdr(Elf *e, char *nf, struct _Elf_Extent *ex) 871 { 872 int ec; 873 void *ehdr; 874 Elf32_Ehdr *eh32; 875 Elf64_Ehdr *eh64; 876 Elf_Data dst, src; 877 size_t fsz, phnum; 878 uint64_t phoff; 879 880 assert(ex->ex_type == ELF_EXTENT_PHDR); 881 882 ec = e->e_class; 883 ehdr = _libelf_ehdr(e, ec, 0); 884 phnum = e->e_u.e_elf.e_nphdr; 885 886 assert(phnum > 0); 887 888 if (ec == ELFCLASS32) { 889 eh32 = (Elf32_Ehdr *) ehdr; 890 phoff = (uint64_t) eh32->e_phoff; 891 } else { 892 eh64 = (Elf64_Ehdr *) ehdr; 893 phoff = eh64->e_phoff; 894 } 895 896 assert(phoff > 0); 897 assert(ex->ex_start == phoff); 898 assert(phoff % _libelf_falign(ELF_T_PHDR, ec) == 0); 899 900 (void) memset(&dst, 0, sizeof(dst)); 901 (void) memset(&src, 0, sizeof(src)); 902 903 fsz = _libelf_fsize(ELF_T_PHDR, ec, e->e_version, phnum); 904 assert(fsz > 0); 905 906 src.d_buf = _libelf_getphdr(e, ec); 907 src.d_version = dst.d_version = e->e_version; 908 src.d_type = ELF_T_PHDR; 909 src.d_size = phnum * _libelf_msize(ELF_T_PHDR, ec, 910 e->e_version); 911 912 dst.d_size = fsz; 913 dst.d_buf = nf + ex->ex_start; 914 915 if (_libelf_xlate(&dst, &src, e->e_byteorder, ec, ELF_TOFILE) == 916 NULL) 917 return ((off_t) -1); 918 919 return (phoff + fsz); 920 } 921 922 /* 923 * Write out an ELF section header table. 924 */ 925 926 static off_t 927 _libelf_write_shdr(Elf *e, char *nf, struct _Elf_Extent *ex) 928 { 929 int ec; 930 void *ehdr; 931 Elf_Scn *scn; 932 uint64_t shoff; 933 Elf32_Ehdr *eh32; 934 Elf64_Ehdr *eh64; 935 size_t fsz, nscn; 936 Elf_Data dst, src; 937 938 assert(ex->ex_type == ELF_EXTENT_SHDR); 939 940 ec = e->e_class; 941 ehdr = _libelf_ehdr(e, ec, 0); 942 nscn = e->e_u.e_elf.e_nscn; 943 944 if (ec == ELFCLASS32) { 945 eh32 = (Elf32_Ehdr *) ehdr; 946 shoff = (uint64_t) eh32->e_shoff; 947 } else { 948 eh64 = (Elf64_Ehdr *) ehdr; 949 shoff = eh64->e_shoff; 950 } 951 952 assert(nscn > 0); 953 assert(shoff % _libelf_falign(ELF_T_SHDR, ec) == 0); 954 assert(ex->ex_start == shoff); 955 956 (void) memset(&dst, 0, sizeof(dst)); 957 (void) memset(&src, 0, sizeof(src)); 958 959 src.d_type = ELF_T_SHDR; 960 src.d_size = _libelf_msize(ELF_T_SHDR, ec, e->e_version); 961 src.d_version = dst.d_version = e->e_version; 962 963 fsz = _libelf_fsize(ELF_T_SHDR, ec, e->e_version, (size_t) 1); 964 965 STAILQ_FOREACH(scn, &e->e_u.e_elf.e_scn, s_next) { 966 if (ec == ELFCLASS32) 967 src.d_buf = &scn->s_shdr.s_shdr32; 968 else 969 src.d_buf = &scn->s_shdr.s_shdr64; 970 971 dst.d_size = fsz; 972 dst.d_buf = nf + ex->ex_start + scn->s_ndx * fsz; 973 974 if (_libelf_xlate(&dst, &src, e->e_byteorder, ec, 975 ELF_TOFILE) == NULL) 976 return ((off_t) -1); 977 } 978 979 return (ex->ex_start + nscn * fsz); 980 } 981 982 /* 983 * Write out the file image. 984 * 985 * The original file could have been mapped in with an ELF_C_RDWR 986 * command and the application could have added new content or 987 * re-arranged its sections before calling elf_update(). Consequently 988 * its not safe to work `in place' on the original file. So we 989 * malloc() the required space for the updated ELF object and build 990 * the object there and write it out to the underlying file at the 991 * end. Note that the application may have opened the underlying file 992 * in ELF_C_RDWR and only retrieved/modified a few sections. We take 993 * care to avoid translating file sections unnecessarily. 994 * 995 * Gaps in the coverage of the file by the file's sections will be 996 * filled with the fill character set by elf_fill(3). 997 */ 998 999 static off_t 1000 _libelf_write_elf(Elf *e, off_t newsize, struct _Elf_Extent_List *extents) 1001 { 1002 off_t nrc, rc; 1003 char *newfile; 1004 Elf_Scn *scn, *tscn; 1005 struct _Elf_Extent *ex; 1006 1007 assert(e->e_kind == ELF_K_ELF); 1008 assert(e->e_cmd == ELF_C_RDWR || e->e_cmd == ELF_C_WRITE); 1009 assert(e->e_fd >= 0); 1010 1011 if ((newfile = malloc((size_t) newsize)) == NULL) { 1012 LIBELF_SET_ERROR(RESOURCE, errno); 1013 return ((off_t) -1); 1014 } 1015 1016 nrc = rc = 0; 1017 SLIST_FOREACH(ex, extents, ex_next) { 1018 1019 /* Fill inter-extent gaps. */ 1020 if (ex->ex_start > (size_t) rc) 1021 (void) memset(newfile + rc, LIBELF_PRIVATE(fillchar), 1022 ex->ex_start - rc); 1023 1024 switch (ex->ex_type) { 1025 case ELF_EXTENT_EHDR: 1026 if ((nrc = _libelf_write_ehdr(e, newfile, ex)) < 0) 1027 goto error; 1028 break; 1029 1030 case ELF_EXTENT_PHDR: 1031 if ((nrc = _libelf_write_phdr(e, newfile, ex)) < 0) 1032 goto error; 1033 break; 1034 1035 case ELF_EXTENT_SECTION: 1036 if ((nrc = _libelf_write_scn(e, newfile, ex)) < 0) 1037 goto error; 1038 break; 1039 1040 case ELF_EXTENT_SHDR: 1041 if ((nrc = _libelf_write_shdr(e, newfile, ex)) < 0) 1042 goto error; 1043 break; 1044 1045 default: 1046 assert(0); 1047 break; 1048 } 1049 1050 assert(ex->ex_start + ex->ex_size == (size_t) nrc); 1051 assert(rc < nrc); 1052 1053 rc = nrc; 1054 } 1055 1056 assert(rc == newsize); 1057 1058 /* 1059 * For regular files, throw away existing file content and 1060 * unmap any existing mappings. 1061 */ 1062 if ((e->e_flags & LIBELF_F_SPECIAL_FILE) == 0) { 1063 if (ftruncate(e->e_fd, (off_t) 0) < 0 || 1064 lseek(e->e_fd, (off_t) 0, SEEK_SET)) { 1065 LIBELF_SET_ERROR(IO, errno); 1066 goto error; 1067 } 1068 #if ELFTC_HAVE_MMAP 1069 if (e->e_flags & LIBELF_F_RAWFILE_MMAP) { 1070 assert(e->e_rawfile != NULL); 1071 assert(e->e_cmd == ELF_C_RDWR); 1072 if (munmap(e->e_rawfile, e->e_rawsize) < 0) { 1073 LIBELF_SET_ERROR(IO, errno); 1074 goto error; 1075 } 1076 } 1077 #endif 1078 } 1079 1080 /* 1081 * Write out the new contents. 1082 */ 1083 if (write(e->e_fd, newfile, (size_t) newsize) != newsize) { 1084 LIBELF_SET_ERROR(IO, errno); 1085 goto error; 1086 } 1087 1088 /* 1089 * For files opened in ELF_C_RDWR mode, set up the new 'raw' 1090 * contents. 1091 */ 1092 if (e->e_cmd == ELF_C_RDWR) { 1093 assert(e->e_rawfile != NULL); 1094 assert((e->e_flags & LIBELF_F_RAWFILE_MALLOC) || 1095 (e->e_flags & LIBELF_F_RAWFILE_MMAP)); 1096 if (e->e_flags & LIBELF_F_RAWFILE_MALLOC) { 1097 free(e->e_rawfile); 1098 e->e_rawfile = newfile; 1099 newfile = NULL; 1100 } 1101 #if ELFTC_HAVE_MMAP 1102 else if (e->e_flags & LIBELF_F_RAWFILE_MMAP) { 1103 if ((e->e_rawfile = mmap(NULL, (size_t) newsize, 1104 PROT_READ, MAP_PRIVATE, e->e_fd, (off_t) 0)) == 1105 MAP_FAILED) { 1106 LIBELF_SET_ERROR(IO, errno); 1107 goto error; 1108 } 1109 } 1110 #endif /* ELFTC_HAVE_MMAP */ 1111 1112 /* Record the new size of the file. */ 1113 e->e_rawsize = newsize; 1114 } else { 1115 /* File opened in ELF_C_WRITE mode. */ 1116 assert(e->e_rawfile == NULL); 1117 } 1118 1119 /* 1120 * Reset flags, remove existing section descriptors and 1121 * {E,P}HDR pointers so that a subsequent elf_get{e,p}hdr() 1122 * and elf_getscn() will function correctly. 1123 */ 1124 1125 e->e_flags &= ~ELF_F_DIRTY; 1126 1127 STAILQ_FOREACH_SAFE(scn, &e->e_u.e_elf.e_scn, s_next, tscn) 1128 _libelf_release_scn(scn); 1129 1130 if (e->e_class == ELFCLASS32) { 1131 free(e->e_u.e_elf.e_ehdr.e_ehdr32); 1132 if (e->e_u.e_elf.e_phdr.e_phdr32) 1133 free(e->e_u.e_elf.e_phdr.e_phdr32); 1134 1135 e->e_u.e_elf.e_ehdr.e_ehdr32 = NULL; 1136 e->e_u.e_elf.e_phdr.e_phdr32 = NULL; 1137 } else { 1138 free(e->e_u.e_elf.e_ehdr.e_ehdr64); 1139 if (e->e_u.e_elf.e_phdr.e_phdr64) 1140 free(e->e_u.e_elf.e_phdr.e_phdr64); 1141 1142 e->e_u.e_elf.e_ehdr.e_ehdr64 = NULL; 1143 e->e_u.e_elf.e_phdr.e_phdr64 = NULL; 1144 } 1145 1146 /* Free the temporary buffer. */ 1147 if (newfile) 1148 free(newfile); 1149 1150 return (rc); 1151 1152 error: 1153 free(newfile); 1154 1155 return ((off_t) -1); 1156 } 1157 1158 /* 1159 * Update an ELF object. 1160 */ 1161 1162 off_t 1163 elf_update(Elf *e, Elf_Cmd c) 1164 { 1165 int ec; 1166 off_t rc; 1167 struct _Elf_Extent_List extents; 1168 1169 rc = (off_t) -1; 1170 1171 if (e == NULL || e->e_kind != ELF_K_ELF || 1172 (c != ELF_C_NULL && c != ELF_C_WRITE)) { 1173 LIBELF_SET_ERROR(ARGUMENT, 0); 1174 return (rc); 1175 } 1176 1177 if ((ec = e->e_class) != ELFCLASS32 && ec != ELFCLASS64) { 1178 LIBELF_SET_ERROR(CLASS, 0); 1179 return (rc); 1180 } 1181 1182 if (e->e_version == EV_NONE) 1183 e->e_version = EV_CURRENT; 1184 1185 if (c == ELF_C_WRITE && e->e_cmd == ELF_C_READ) { 1186 LIBELF_SET_ERROR(MODE, 0); 1187 return (rc); 1188 } 1189 1190 SLIST_INIT(&extents); 1191 1192 if ((rc = _libelf_resync_elf(e, &extents)) < 0) 1193 goto done; 1194 1195 if (c == ELF_C_NULL) 1196 goto done; 1197 1198 if (e->e_fd < 0) { 1199 rc = (off_t) -1; 1200 LIBELF_SET_ERROR(SEQUENCE, 0); 1201 goto done; 1202 } 1203 1204 rc = _libelf_write_elf(e, rc, &extents); 1205 1206 done: 1207 _libelf_release_extents(&extents); 1208 return (rc); 1209 } 1210