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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 | /* * Copyright (c) 2021 Apple Inc. All rights reserved. * * @APPLE_LICENSE_HEADER_START@ * * This file contains Original Code and/or Modifications of Original Code * as defined in and that are subject to the Apple Public Source License * Version 2.0 (the 'License'). You may not use this file except in * compliance with the License. Please obtain a copy of the License at * http://www.opensource.apple.com/apsl/ and read it before using this * file. * * The Original Code and all software distributed under the License are * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES, * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY, * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT. * Please see the License for the specific language governing rights and * limitations under the License. * * @APPLE_LICENSE_HEADER_END@ */ #include <sys/types.h> #include <assert.h> #include <limits.h> #include <stdlib.h> #include <string.h> #include <mach-o/loader.h> #include <mach-o/nlist.h> #include "Algorithm.h" #include "Array.h" // mach_o #include "Misc.h" #include "Image.h" // mach_o_writer #include "ChainedFixupsWriter.h" using dyld3::Array; namespace mach_o { // // MARK: --- ChainedFixupsWriter inspection methods --- // const uint8_t* ChainedFixupsWriter::bytes(size_t& size) const { size = _fixupsSize; return _bytes.data(); } Error ChainedFixupsWriter::valid(uint64_t preferredLoadAddress, std::span<const MappedSegment> segments, bool startsInSection) const { if ( _buildError.hasError() ) return Error("%s", _buildError.message()); return ChainedFixups::valid(preferredLoadAddress, segments, startsInSection); } template <typename T> static T align8(T value) { return (value + 7) & (-8); } template <typename T> static T align4(T value) { return (value + 3) & (-4); } size_t ChainedFixupsWriter::linkeditSize(std::span<const Fixup::BindTarget> bindTargets, std::span<const SegmentFixupsInfo> segments, const PointerFormat& pointerFormat, uint32_t pageSize) { // scan binds to figure out which imports table format to use uint16_t imFormat; size_t stringPoolSize; if ( Error err = importsFormat(bindTargets, imFormat, stringPoolSize) ) return 0; // allocate space in _bytes for full dyld_chained_fixups data structure size_t maxBytesNeeded = align8(sizeof(dyld_chained_fixups_header)); maxBytesNeeded += offsetof(dyld_chained_starts_in_image,seg_info_offset[segments.size()]); for ( const SegmentFixupsInfo& segment : segments ) { const MappedSegment& seg = segment.mappedSegment; uint32_t extras = segment.numPageExtras; std::span<const Fixup> segFixups = segment.fixups; if ( seg.writable && (seg.runtimeSize != 0) && !segFixups.empty() ) { uint64_t lastFixupSegmentOffset = (uint64_t)segFixups.back().location - (uint64_t)seg.content; uint64_t lastFixupPage = (lastFixupSegmentOffset / pageSize) + 1; maxBytesNeeded = align8(maxBytesNeeded); maxBytesNeeded += offsetof(dyld_chained_starts_in_segment, page_start[lastFixupPage + extras]); } else if ( pointerFormat.value() == DYLD_CHAINED_PTR_ARM64E_SEGMENTED ) { // this format requires an entry for every segment (to get seg's base address) maxBytesNeeded = align8(maxBytesNeeded); maxBytesNeeded += offsetof(dyld_chained_starts_in_segment, page_start[1]); } } if ( imFormat == DYLD_CHAINED_IMPORT_ADDEND64 ) { maxBytesNeeded = align8(maxBytesNeeded); maxBytesNeeded += sizeof(dyld_chained_import_addend64) * bindTargets.size(); } else if ( imFormat == DYLD_CHAINED_IMPORT_ADDEND ) { maxBytesNeeded = align4(maxBytesNeeded); maxBytesNeeded += sizeof(dyld_chained_import_addend) * bindTargets.size(); } else { maxBytesNeeded = align4(maxBytesNeeded); maxBytesNeeded += sizeof(dyld_chained_import) * bindTargets.size(); } maxBytesNeeded += stringPoolSize; return align8(maxBytesNeeded); } size_t ChainedFixupsWriter::startsSectionSize( std::span<const SegmentFixupsInfo> segments, const PointerFormat& pointerFormat) { uint64_t expectedDelta = 0; switch ( pointerFormat.value() ) { case DYLD_CHAINED_PTR_ARM64E_KERNEL: expectedDelta = 0x1FFF; break; case DYLD_CHAINED_PTR_64_OFFSET: case DYLD_CHAINED_PTR_ARM64E_SEGMENTED: expectedDelta = 0x3FFF; break; default: assert(false && "unknown pointer format for chain starts"); break; } // allocate space in _bytes for full dyld_chained_starts_offsets data structure size_t chainsCount = 0; for (const SegmentFixupsInfo& segment : segments) { const MappedSegment& seg = segment.mappedSegment; std::span<const Fixup> segFixups = segment.fixups; if ( !seg.writable || seg.runtimeSize == 0 || segFixups.empty() ) continue; //fprintf(stderr, "seg: %s\n", seg.segName.data()); size_t segChains = 1; uint64_t lastFixupLoc = (uint64_t)segFixups.front().location; for (const Fixup& fixup : segFixups) { uint64_t curFixupLoc = (uint64_t)fixup.location; uint64_t delta = curFixupLoc - lastFixupLoc; if ( delta >= expectedDelta ) segChains++; lastFixupLoc = curFixupLoc; //fprintf(stderr, "fixup: 0x%llx\n", (uint64_t)fixup.location); } chainsCount += segChains; } size_t maxBytesNeeded = offsetof(dyld_chained_starts_offsets,chain_starts[chainsCount]); maxBytesNeeded = align8(maxBytesNeeded); return maxBytesNeeded; } void ChainedFixupsWriter::calculateSegmentPageExtras(std::span<SegmentFixupsInfo> segments, const PointerFormat& pointerFormat, uint32_t pageSize) { for ( SegmentFixupsInfo& segmentFixupInfo : segments ) { const MappedSegment& segment = segmentFixupInfo.mappedSegment; const std::span<const Fixup> fixupsInSegment = segmentFixupInfo.fixups; uint32_t numExtras = 0; // skip segments with no fixups if ( !segment.writable || (segment.runtimeSize == 0) || fixupsInSegment.empty() ) continue; int curPageIndex = -1; const Fixup* prevFixup = nullptr; bool pageHasExtras = false; for ( const Fixup& fixup : fixupsInSegment ) { uint64_t offset = (uint8_t*)fixup.location - (uint8_t*)segment.content; int pageIndex = (int)(offset/pageSize); if ( pageIndex != curPageIndex ) { curPageIndex = pageIndex; prevFixup = nullptr; pageHasExtras = false; } if ( prevFixup != nullptr ) { intptr_t delta = (uint8_t*)fixup.location - (uint8_t*)(prevFixup->location); if ( delta > pointerFormat.maxNext() ) { // prev/next are too far apart for chain to span, instead terminate chain at prevFixup // then start new overflow chain if ( !pageHasExtras ) { // A page with extras needs a start and end of the chain too numExtras += 2; pageHasExtras = true; } ++numExtras; } } prevFixup = &fixup; } segmentFixupInfo.numPageExtras = numExtras; } } Error ChainedFixupsWriter::importsFormat(std::span<const Fixup::BindTarget> bindTargets, uint16_t& importsFormat, size_t& stringPoolSize) { importsFormat = DYLD_CHAINED_IMPORT; stringPoolSize = 0; bool hasLargeOrdinal = false; bool has32bitAddend = false; bool has64bitAddend = false; stringPoolSize = 1; for (const Fixup::BindTarget& bind : bindTargets) { stringPoolSize += (bind.symbolName.size() + 1); if ( bind.libOrdinal < -15 ) { // TODO: currently only -1, -2, and -3 have meaning. Should we error here for < -3 ? return Error("special libOrdinal (%d) too small", bind.libOrdinal); } if ( bind.libOrdinal > 240 ) { hasLargeOrdinal = true; if ( bind.libOrdinal > 65520 ) { return Error("libOrdinal (%d) too large", bind.libOrdinal); } } if ( bind.addend != 0 ) { int32_t addend32 = (int32_t)bind.addend; if ( (int64_t)addend32 == bind.addend ) has32bitAddend = true; else has64bitAddend = true; } } bool hasLargeStringOffsets = dyld_chained_import{.name_offset=(uint32_t)stringPoolSize}.name_offset != stringPoolSize; if ( hasLargeStringOffsets || has64bitAddend || hasLargeOrdinal ) importsFormat = DYLD_CHAINED_IMPORT_ADDEND64; else if ( has32bitAddend ) importsFormat = DYLD_CHAINED_IMPORT_ADDEND; else importsFormat = DYLD_CHAINED_IMPORT; if ( stringPoolSize > 0xFFFFFFFF ) return Error("imports string pool > 4GB"); return Error::none(); } ChainedFixupsWriter::ChainedFixupsWriter(std::span<const Fixup::BindTarget> bindTargets, std::span<const Fixup> fixups, std::span<const MappedSegment> segments, uint64_t preferredLoadAddress, const PointerFormat& pointerFormat, uint32_t pageSize, bool setDataChains, bool startsInSection, bool useFileOffsets) : ChainedFixups() { std::vector<std::vector<Fixup>> fixupsInSegments; fixupsInSegments.resize(segments.size()); { // unify and sort fixups to make chains std::vector<Fixup> sortedFixups(fixups.begin(), fixups.end()); std::sort(sortedFixups.begin(), sortedFixups.end()); // verify there are no locations with multiple fixups if ( sortedFixups.size() > 1 ) { Fixup lastLoc = sortedFixups.back(); for (const Fixup& f : sortedFixups) { if ( f.location == lastLoc.location ) { _buildError = Error("multiple fixups at same location in %.*s at offset=0x%lX", (int)f.segment->segName.size(), f.segment->segName.data(), (uint8_t*)f.location - (uint8_t*)(f.segment->content)); return; } lastLoc = f; } } for ( const Fixup fixup : sortedFixups) { uint64_t segmentIndex = fixup.segment - &segments.front(); fixupsInSegments[segmentIndex].push_back(fixup); } } std::vector<SegmentFixupsInfo> segmentFixupInfos; for ( uint32_t segIndex = 0; segIndex != segments.size(); ++segIndex ) { segmentFixupInfos.push_back({ segments[segIndex], fixupsInSegments[segIndex], 0 }); } calculateSegmentPageExtras(segmentFixupInfos, pointerFormat, pageSize); if ( startsInSection ) { buildStartsSectionFixups(segmentFixupInfos, pointerFormat, useFileOffsets, preferredLoadAddress); } else { buildLinkeditFixups(bindTargets, segmentFixupInfos, preferredLoadAddress, pointerFormat, pageSize, setDataChains); } } ChainedFixupsWriter::ChainedFixupsWriter(std::span<const Fixup::BindTarget> bindTargets, std::span<const SegmentFixupsInfo> segments, uint64_t preferredLoadAddress, const PointerFormat& pointerFormat, uint32_t pageSize, bool setDataChains, bool startsInSection, bool useFileOffsets) { if ( startsInSection ) { buildStartsSectionFixups(segments, pointerFormat, useFileOffsets, preferredLoadAddress); } else { buildLinkeditFixups(bindTargets, segments, preferredLoadAddress, pointerFormat, pageSize, setDataChains); } } template<typename T, typename U> void atomic_min(std::atomic<T>& location, U value, const T defaultValue = nullptr) { // If we manage to swap with the default value, then no other thread had set the value, and we're done T expected = defaultValue; while ( !location.compare_exchange_weak(expected, value, std::memory_order::release, std::memory_order_relaxed) ) { // Value change before the store, if new value is smaller (but not null) then there's no need to store if ( expected != defaultValue && expected <= value ) break; } } template<typename T, typename U> void atomic_max(std::atomic<T>& location, U value) { // If we manage to swap with nullptr, then no other thread had set the value, and we're done T expected = nullptr; while ( !location.compare_exchange_weak(expected, value, std::memory_order::release, std::memory_order_relaxed) ) { // Value change before the store, if new value is larger then there's no need to store if ( expected >= value ) break; } } void ChainedFixupsWriter::buildLinkeditFixups(std::span<const Fixup::BindTarget> bindTargets, std::span<const SegmentFixupsInfo> segments, uint64_t preferredLoadAddress, const PointerFormat& pointerFormat, uint32_t pageSize, bool setDataChains) { // scan binds to figure out which imports table format to use uint16_t imFormat; size_t stringPoolSize; _buildError = importsFormat(bindTargets, imFormat, stringPoolSize); if ( _buildError.hasError() ) return; // build imports table std::vector<char> stringPool; size_t importsTableSize = 0; const void* importsTableStart = nullptr; std::vector<dyld_chained_import> imports ; std::vector<dyld_chained_import_addend> importsAddend; std::vector<dyld_chained_import_addend64> importsAddend64; stringPool.reserve(stringPoolSize); stringPool.push_back('\0'); // so that zero is never a legal string offset if ( imFormat == DYLD_CHAINED_IMPORT_ADDEND64 ) { importsAddend64.reserve(bindTargets.size()); for (const Fixup::BindTarget& bind : bindTargets) { importsAddend64.push_back({(uint16_t)bind.libOrdinal, bind.weakImport, 0, addSymbolString(bind.symbolName, stringPool), (uint64_t)bind.addend}); } importsTableSize = sizeof(dyld_chained_import_addend64) * importsAddend64.size(); if ( !importsAddend64.empty() ) importsTableStart = &importsAddend64[0]; } else if ( imFormat == DYLD_CHAINED_IMPORT_ADDEND ) { importsAddend.reserve(bindTargets.size()); for (const Fixup::BindTarget& bind : bindTargets) { importsAddend.push_back({(uint8_t)bind.libOrdinal, bind.weakImport, addSymbolString(bind.symbolName, stringPool), (int32_t)bind.addend}); } importsTableSize = sizeof(dyld_chained_import_addend) * importsAddend.size(); if ( !importsAddend.empty() ) importsTableStart = &importsAddend[0]; } else { // can use most compact imports encoding imports.reserve(bindTargets.size()); for (const Fixup::BindTarget& bind : bindTargets) { imports.push_back({(uint8_t)bind.libOrdinal, bind.weakImport, addSymbolString(bind.symbolName, stringPool)}); } importsTableSize = sizeof(dyld_chained_import) * imports.size(); if ( !imports.empty() ) importsTableStart = &imports[0]; } // for 32-bit archs, compute max valid pointer value uint64_t maxValidPointer = 0; if ( !pointerFormat.is64() ) { uint64_t lastDataSegmentIndex = segments.size() - (segments.back().mappedSegment.segName == "__LINKEDIT" ? 2 : 1); const MappedSegment& lastDataSegment = segments[lastDataSegmentIndex].mappedSegment; // for 32-bit binaries rebase targets are 0 based, so load address needs to be included in max pointer computation uint64_t lastDataSegmentLastVMAddr = preferredLoadAddress + lastDataSegment.runtimeOffset + lastDataSegment.runtimeSize; maxValidPointer = (lastDataSegmentLastVMAddr + 0x00100000-1) & -0x00100000; // align to 1MB } // allocate space in _bytes for full dyld_chained_fixups data structure size_t maxBytesNeeded = linkeditSize(bindTargets, segments, pointerFormat, pageSize); _bytes.resize(maxBytesNeeded, 0); // ensure alignment padding is zeroed out // build dyld_chained_fixups data structure dyld_chained_fixups_header* header = (dyld_chained_fixups_header*)(&_bytes[0]); header->fixups_version = 0; // version 0 header->starts_offset = (uint32_t)align8(sizeof(dyld_chained_fixups_header)); // 8-byte align dyld_chained_starts_in_image header->imports_offset = 0; // filled in later header->symbols_offset = 0; // filled in later header->imports_count = (uint32_t)bindTargets.size(); header->imports_format = imFormat; header->symbols_format = 0; // raw strings dyld_chained_starts_in_image* startsInfo = (dyld_chained_starts_in_image*)(&_bytes[header->starts_offset]); startsInfo->seg_count = (uint32_t)segments.size(); // create dyld_chained_starts_in_segment for each segment { uint32_t segInfoOffset = (uint32_t)offsetof(dyld_chained_starts_in_image,seg_info_offset[segments.size()]); for ( uint32_t segIndex = 0; segIndex != segments.size(); ++segIndex ) { const MappedSegment& segment = segments[segIndex].mappedSegment; const std::span<const Fixup> fixupsInSegment = segments[segIndex].fixups; // don't make dyld_chained_starts_in_segment for segments with no fixups if ( !segment.writable || (segment.runtimeSize == 0) || fixupsInSegment.empty() ) { // segmented chain format needs seg info for all segments so each base addr is known if ( pointerFormat.value() != DYLD_CHAINED_PTR_ARM64E_SEGMENTED ) { startsInfo->seg_info_offset[segIndex] = 0; continue; } } uint32_t absOffset = header->starts_offset + segInfoOffset; segInfoOffset += align8(absOffset) - absOffset; startsInfo->seg_info_offset[segIndex] = segInfoOffset; dyld_chained_starts_in_segment* segInfo = (dyld_chained_starts_in_segment*)(&_bytes[header->starts_offset+segInfoOffset]); segInfo->size = (uint32_t)offsetof(dyld_chained_starts_in_segment, page_start[1]); segInfo->page_size = pageSize; segInfo->pointer_format = pointerFormat.value(); segInfo->segment_offset = segment.runtimeOffset; segInfo->max_valid_pointer = (uint32_t)maxValidPointer; segInfo->page_count = 0; // fill in later, may be trailing pages with no fixups segInfo->page_start[0] = DYLD_CHAINED_PTR_START_NONE; if ( !fixupsInSegment.empty() ) { uint64_t lastFixupSegmentOffset = (uint64_t)fixupsInSegment.back().location - (uint64_t)segment.content; uint64_t lastFixupPage = (lastFixupSegmentOffset / pageSize) + 1; segInfo->page_count = lastFixupPage; segInfo->size = (uint32_t)offsetof(dyld_chained_starts_in_segment, page_start[segInfo->page_count]); // adjust segment size info to include overflow entries segInfo->size += segments[segIndex].numPageExtras * sizeof(uint16_t); } segInfoOffset += segInfo->size; } if ( imFormat == DYLD_CHAINED_IMPORT_ADDEND64 ) header->imports_offset = align8(header->starts_offset + segInfoOffset); else header->imports_offset = align4(header->starts_offset + segInfoOffset); header->symbols_offset = (uint32_t)(header->imports_offset + importsTableSize); } std::vector<const MappedSegment*> mappedSegmentsBuffer; mappedSegmentsBuffer.reserve(segments.size()); for ( const SegmentFixupsInfo& segInfo : segments ) mappedSegmentsBuffer.push_back(&segInfo.mappedSegment); std::span<const MappedSegment*> mappedSegments = mappedSegmentsBuffer; // For segments, we're going to try do each page in parallel when possible // First this means computing the range of fixups for every page. We can do that in parallel // Then walk those ranges in parallel. // For segments with pageExtras, its too hard to do pages in parallel so we'll go serially for ( uint32_t segIndex = 0; segIndex != segments.size(); ++segIndex ) { uint32_t segInfoOffset = startsInfo->seg_info_offset[segIndex]; if ( segInfoOffset == 0 ) continue; const dyld_chained_starts_in_segment* segInfo = (dyld_chained_starts_in_segment*)(&_bytes[header->starts_offset + segInfoOffset]); const MappedSegment& segment = segments[segIndex].mappedSegment; const std::span<const Fixup> segFixups = segments[segIndex].fixups; uint32_t segExtras = segments[segIndex].numPageExtras; std::span<uint16_t> pageStarts = { (uint16_t*)&segInfo->page_start[0], segInfo->page_count }; const uint32_t minNext = pointerFormat.minNext(); if ( segExtras != 0 ) { // Segment has extras. Take the slow path std::span<uint16_t> extras = { (uint16_t*)&segInfo->page_start[segInfo->page_count], segExtras }; int curPageIndex = -1; int curExtrasIndex = -1; const Fixup* prevFixup = nullptr; for ( const Fixup& fixup : segFixups ) { uint64_t segOffset = (uint8_t*)fixup.location - (uint8_t*)segment.content; int pageIndex = (int)(segOffset/pageSize); if ( pageIndex != curPageIndex ) { // End the previous chain if we have one if ( prevFixup != nullptr ) { if ( (pageStarts[curPageIndex] & DYLD_CHAINED_PTR_START_MULTI) != 0 ) { // Mark the end of this extras chain extras[curExtrasIndex] |= DYLD_CHAINED_PTR_START_LAST; } if ( setDataChains ) { // set end of chain for this page pointerFormat.writeChainEntry(*prevFixup, nullptr, preferredLoadAddress, mappedSegments); } } while (curPageIndex < pageIndex) { ++curPageIndex; pageStarts[curPageIndex] = DYLD_CHAINED_PTR_START_NONE; } pageStarts[curPageIndex] = (segOffset - (curPageIndex*pageSize)); prevFixup = nullptr; } // Found a previous fixup on this page, so make a chain from it to this fixup if ( prevFixup != nullptr ) { uint8_t* chain = (uint8_t*)fixup.location; intptr_t delta = chain - (uint8_t*)(prevFixup->location); if ( delta <= pointerFormat.maxNext() ) { if ( (delta % minNext) != 0 ) { _buildError = Error("pointer not %d-byte aligned at %.*s+0x%llX, fix alignment or disable chained fixups", minNext, (int)segment.segName.size(), segment.segName.data(), segOffset); break; } else if ( setDataChains ) { pointerFormat.writeChainEntry(*prevFixup, chain, preferredLoadAddress, mappedSegments); } } else { // prev/next are too far apart for chain to span, instead terminate chain at prevFixup if ( setDataChains ) pointerFormat.writeChainEntry(*prevFixup, nullptr, preferredLoadAddress, mappedSegments); // then start new overflow chain if ( (pageStarts[curPageIndex] & DYLD_CHAINED_PTR_START_MULTI) == 0 ) { ++curExtrasIndex; // move first start to overflow array extras[curExtrasIndex] = pageStarts[curPageIndex]; // change first page start to point into overflow array pageStarts[curPageIndex] = DYLD_CHAINED_PTR_START_MULTI | (segInfo->page_count + curExtrasIndex); } uint16_t pageOffset = segOffset % pageSize; ++curExtrasIndex; extras[curExtrasIndex] = pageOffset; } } prevFixup = &fixup; } // if this page required multiple starts, mark last one if ( (pageStarts[curPageIndex] & DYLD_CHAINED_PTR_START_MULTI) != 0 ) { extras[curExtrasIndex] |= DYLD_CHAINED_PTR_START_LAST; } if ( setDataChains && (prevFixup != nullptr) ) { // set end of chain pointerFormat.writeChainEntry(*prevFixup, nullptr, preferredLoadAddress, mappedSegments); } } else { // No extras, so use parallelism typedef std::pair<std::atomic<const Fixup*>, std::atomic<const Fixup*>> FixupRange; // use up to 128kb on stack, main thread has 8mb large stack by default STACK_ALLOC_OVERFLOW_SAFE_ARRAY(FixupRange, fixupRangesStorage, 0x2000); fixupRangesStorage.resize(segInfo->page_count); // array ::resize doesn't initialize new elements, so do it here bzero(&fixupRangesStorage[0], sizeof(FixupRange) * segInfo->page_count); std::span<FixupRange> fixupRanges = { &fixupRangesStorage[0], segInfo->page_count }; // Walk all fixups and get the range for each page mapReduce(segFixups, ^(size_t, int&, std::span<const Fixup> fixups) { int curPageIndex = -1; const Fixup* endFixup = nullptr; // The very first fixup we process might be the first on its page, or might be // somewhere in the middle. So it needs as atomic min to make sure its safe with other threads { const Fixup& fixup = fixups[0]; uint64_t segOffset = (uint8_t*)fixup.location - (uint8_t*)segment.content; int pageIndex = (int)(segOffset/pageSize); atomic_min(fixupRanges[pageIndex].first, &fixup); curPageIndex = pageIndex; endFixup = &fixup; } fixups = fixups.subspan(1); for ( const Fixup& fixup : fixups ) { uint64_t segOffset = (uint8_t*)fixup.location - (uint8_t*)segment.content; int pageIndex = (int)(segOffset/pageSize); if ( pageIndex != curPageIndex ) { // Crossing in to a new page. As fixups are sorted, we know for sure the // last fixup we processed must be on the end of its page fixupRanges[curPageIndex].second.store(endFixup, std::memory_order_relaxed); // Also the new fixup we have must be the first on its page fixupRanges[pageIndex].first.store(&fixup, std::memory_order_relaxed); curPageIndex = pageIndex; } endFixup = &fixup; } // The last fixup we have is somewhere in a page, but we don't know if its the end // of that page or not. Try set it as the max atomic_max(fixupRanges[curPageIndex].second, endFixup); }); // If there's an unaligned fixup, this will store if offset in the segment std::atomic<uint64_t> unalignedFixupOffset = ~0ULL; std::atomic<uint64_t>& unalignedFixupOffsetRef = unalignedFixupOffset; // Now process all pages in parallel mapReduce(fixupRanges, std::max(fixupRanges.size() / 64, 32ul), ^(size_t, int&, std::span<FixupRange> ranges) { for ( const FixupRange& fixupRange : ranges ) { size_t pageIndex = &fixupRange - fixupRanges.data(); const Fixup* start = fixupRange.first.load(std::memory_order_relaxed); const Fixup* end = fixupRange.second.load(std::memory_order_relaxed); if ( start == nullptr ) { assert(end == nullptr); pageStarts[pageIndex] = DYLD_CHAINED_PTR_START_NONE; continue; } assert(end != nullptr); assert(start <= end); uint64_t startSegOffset = (uint8_t*)start->location - (uint8_t*)segment.content; pageStarts[pageIndex] = (startSegOffset - (pageIndex * pageSize)); if ( setDataChains ) { const Fixup* fixup = start; while ( fixup != end ) { const Fixup* prev = fixup; ++fixup; uint8_t* chain = (uint8_t*)fixup->location; intptr_t delta = chain - (uint8_t*)(prev->location); if ( (delta % minNext) != 0 ) { uint64_t segOffset = (uint8_t*)fixup->location - (uint8_t*)segment.content; atomic_min(unalignedFixupOffsetRef, segOffset, ~0ULL); break; } pointerFormat.writeChainEntry(*prev, chain, preferredLoadAddress, mappedSegments); } // set end of chain pointerFormat.writeChainEntry(*end, nullptr, preferredLoadAddress, mappedSegments); } } }); uint64_t segOffset = unalignedFixupOffset.load(std::memory_order_relaxed); if ( (segOffset != ~0ULL) && !_buildError.hasError() ) { _buildError = Error("pointer not %d-byte aligned at %.*s+0x%llX, fix alignment or disable chained fixups", minNext, (int)segment.segName.size(), segment.segName.data(), segOffset); } } } // append import table and string pool memcpy(&_bytes[header->imports_offset], importsTableStart, importsTableSize); memcpy(&_bytes[header->symbols_offset], &stringPool[0], stringPool.size()); _fixupsHeader = (dyld_chained_fixups_header*)(&_bytes[0]); _fixupsSize = _bytes.size(); } void ChainedFixupsWriter::buildStartsSectionFixups(std::span<const SegmentFixupsInfo> segments, const PointerFormat& pointerFormat, bool useFileOffsets, uint64_t preferredLoadAddress) { // Allocate space in _bytes for dyld_chained_starts_offsets data structure size_t maxBytesNeeded = startsSectionSize(segments, pointerFormat); _bytes.resize(maxBytesNeeded, 0); // ensure alignment padding is zeroed out // Build dyld_chained_starts_offsets data structure dyld_chained_starts_offsets* header = (dyld_chained_starts_offsets*)(&_bytes[0]); header->pointer_format = pointerFormat.value(); header->starts_count = 0; // filled in later header->chain_starts[0] = 0; // filled in later // make span for use by writeChainEntry() std::vector<const MappedSegment*> mappedSegmentsBuffer; mappedSegmentsBuffer.reserve(segments.size()); for ( const SegmentFixupsInfo& segInfo : segments ) mappedSegmentsBuffer.push_back(&segInfo.mappedSegment); std::span<const MappedSegment*> mappedSegments = mappedSegmentsBuffer; std::vector<uint32_t> startsOffsets; for (const SegmentFixupsInfo& segmentFixups : segments) { const MappedSegment& segment = segmentFixups.mappedSegment; const std::span<const Fixup> fixups = segmentFixups.fixups; // Don't make chain_starts for segments with no fixups if ( !segment.writable || (segment.runtimeSize == 0) || fixups.empty() ) continue; uint64_t maxDelta = 0; switch ( pointerFormat.value() ) { case DYLD_CHAINED_PTR_ARM64E_KERNEL: maxDelta = 0x1FFF; break; case DYLD_CHAINED_PTR_64_OFFSET: maxDelta = 0x3FFF; break; default: assert(false && "unknown pointer format for chain starts"); break; } const Fixup* prevFixup = nullptr; for (const Fixup& fixup : fixups) { // -fixup_chains_section_vm uint64_t segmentOffset = segment.runtimeOffset; if ( useFileOffsets ) { // -fixup_chains_section segmentOffset = segment.fileOffset; } uint64_t offsetInSegment = (uint64_t)fixup.location - (uint64_t)segment.content; uint64_t fixupOffset = segmentOffset + offsetInSegment; assert(fixupOffset == (uint32_t)fixupOffset); if ( prevFixup == nullptr ) { // First fixup startsOffsets.push_back((uint32_t)fixupOffset); prevFixup = &fixup; continue; } uint8_t* chain = (uint8_t*)fixup.location; uint64_t delta = (uint64_t)chain - (uint64_t)(prevFixup->location); if ( delta < maxDelta ) { pointerFormat.writeChainEntry(*prevFixup, chain, 0 /* preferedLoadAddress */, mappedSegments); } else { // prev/next are too far apart for chain to span, instead terminate chain at prevFixup pointerFormat.writeChainEntry(*prevFixup, nullptr /* nextLoc */, 0 /* preferedLoadAddress */, mappedSegments); startsOffsets.push_back((uint32_t)fixupOffset); } prevFixup = &fixup; } // Terminate last chain pointerFormat.writeChainEntry(*prevFixup, nullptr /* nextLoc */, 0 /* preferedLoadAddress */, mappedSegments); uint32_t startsCount = (uint32_t)startsOffsets.size(); assert(startsCount == startsOffsets.size()); header->starts_count = startsCount; for (uint32_t i = 0; i < startsCount; i++) { header->chain_starts[i] = startsOffsets[i]; } } _chainStartsHeader = (dyld_chained_starts_offsets*)(&_bytes[0]); _fixupsSize = _bytes.size(); } uint32_t ChainedFixupsWriter::addSymbolString(CString symbolName, std::vector<char>& pool) { uint32_t symbolOffset = (uint32_t)pool.size(); // end+1 to copy also the null-terminator pool.insert(pool.end(), symbolName.begin(), symbolName.end()+1); return symbolOffset; } } // namespace mach_o |