/* -*- mode: C++; c-basic-offset: 4; tab-width: 4 -*- * * Copyright (c) 2006-2015 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@ */ #ifndef __DYLD_CACHE_FORMAT__ #define __DYLD_CACHE_FORMAT__ #include <stdint.h> #include <uuid/uuid.h> struct dyld_cache_header { char magic[16]; // e.g. "dyld_v0 i386" uint32_t mappingOffset; // file offset to first dyld_cache_mapping_info uint32_t mappingCount; // number of dyld_cache_mapping_info entries uint32_t imagesOffset; // file offset to first dyld_cache_image_info uint32_t imagesCount; // number of dyld_cache_image_info entries uint64_t dyldBaseAddress; // base address of dyld when cache was built uint64_t codeSignatureOffset; // file offset of code signature blob uint64_t codeSignatureSize; // size of code signature blob (zero means to end of file) uint64_t slideInfoOffset; // file offset of kernel slid info uint64_t slideInfoSize; // size of kernel slid info uint64_t localSymbolsOffset; // file offset of where local symbols are stored uint64_t localSymbolsSize; // size of local symbols information uint8_t uuid[16]; // unique value for each shared cache file uint64_t cacheType; // 0 for development, 1 for production uint32_t branchPoolsOffset; // file offset to table of uint64_t pool addresses uint32_t branchPoolsCount; // number of uint64_t entries uint64_t accelerateInfoAddr; // (unslid) address of optimization info uint64_t accelerateInfoSize; // size of optimization info uint64_t imagesTextOffset; // file offset to first dyld_cache_image_text_info uint64_t imagesTextCount; // number of dyld_cache_image_text_info entries uint64_t dylibsImageGroupAddr; // (unslid) address of ImageGroup for dylibs in this cache uint64_t dylibsImageGroupSize; // size of ImageGroup for dylibs in this cache uint64_t otherImageGroupAddr; // (unslid) address of ImageGroup for other OS dylibs uint64_t otherImageGroupSize; // size of oImageGroup for other OS dylibs uint64_t progClosuresAddr; // (unslid) address of list of program launch closures uint64_t progClosuresSize; // size of list of program launch closures uint64_t progClosuresTrieAddr; // (unslid) address of trie of indexes into program launch closures uint64_t progClosuresTrieSize; // size of trie of indexes into program launch closures uint32_t platform; // platform number (macOS=1, etc) uint32_t formatVersion : 8, // launch_cache::binary_format::kFormatVersion dylibsExpectedOnDisk : 1, // dyld should expect the dylib exists on disk and to compare inode/mtime to see if cache is valid simulator : 1; // for simulator of specified platform uint64_t sharedRegionStart; // base load address of cache if not slid uint64_t sharedRegionSize; // overall size of region cache can be mapped into uint64_t maxSlide; // runtime slide of cache can be between zero and this value }; struct dyld_cache_mapping_info { uint64_t address; uint64_t size; uint64_t fileOffset; uint32_t maxProt; uint32_t initProt; }; struct dyld_cache_image_info { uint64_t address; uint64_t modTime; uint64_t inode; uint32_t pathFileOffset; uint32_t pad; }; struct dyld_cache_image_info_extra { uint64_t exportsTrieAddr; // address of trie in unslid cache uint64_t weakBindingsAddr; uint32_t exportsTrieSize; uint32_t weakBindingsSize; uint32_t dependentsStartArrayIndex; uint32_t reExportsStartArrayIndex; }; struct dyld_cache_accelerator_info { uint32_t version; // currently 1 uint32_t imageExtrasCount; // does not include aliases uint32_t imagesExtrasOffset; // offset into this chunk of first dyld_cache_image_info_extra uint32_t bottomUpListOffset; // offset into this chunk to start of 16-bit array of sorted image indexes uint32_t dylibTrieOffset; // offset into this chunk to start of trie containing all dylib paths uint32_t dylibTrieSize; // size of trie containing all dylib paths uint32_t initializersOffset; // offset into this chunk to start of initializers list uint32_t initializersCount; // size of initializers list uint32_t dofSectionsOffset; // offset into this chunk to start of DOF sections list uint32_t dofSectionsCount; // size of initializers list uint32_t reExportListOffset; // offset into this chunk to start of 16-bit array of re-exports uint32_t reExportCount; // size of re-exports uint32_t depListOffset; // offset into this chunk to start of 16-bit array of dependencies (0x8000 bit set if upward) uint32_t depListCount; // size of dependencies uint32_t rangeTableOffset; // offset into this chunk to start of ss uint32_t rangeTableCount; // size of dependencies uint64_t dyldSectionAddr; // address of libdyld's __dyld section in unslid cache }; struct dyld_cache_accelerator_initializer { uint32_t functionOffset; // address offset from start of cache mapping uint32_t imageIndex; }; struct dyld_cache_range_entry { uint64_t startAddress; // unslid address of start of region uint32_t size; uint32_t imageIndex; }; struct dyld_cache_accelerator_dof { uint64_t sectionAddress; // unslid address of start of region uint32_t sectionSize; uint32_t imageIndex; }; struct dyld_cache_image_text_info { uuid_t uuid; uint64_t loadAddress; // unslid address of start of __TEXT uint32_t textSegmentSize; uint32_t pathOffset; // offset from start of cache file }; // The rebasing info is to allow the kernel to lazily rebase DATA pages of the // dyld shared cache. Rebasing is adding the slide to interior pointers. struct dyld_cache_slide_info { uint32_t version; // currently 1 uint32_t toc_offset; uint32_t toc_count; uint32_t entries_offset; uint32_t entries_count; uint32_t entries_size; // currently 128 // uint16_t toc[toc_count]; // entrybitmap entries[entries_count]; }; // The version 2 of the slide info uses a different compression scheme. Since // only interior pointers (pointers that point within the cache) are rebased // (slid), we know the possible range of the pointers and thus know there are // unused bits in each pointer. We use those bits to form a linked list of // locations needing rebasing in each page. // // Definitions: // // pageIndex = (pageAddress - startOfAllDataAddress)/info->page_size // pageStarts[] = info + info->page_starts_offset // pageExtras[] = info + info->page_extras_offset // valueMask = ~(info->delta_mask) // deltaShift = __builtin_ctzll(info->delta_mask) - 2 // // There are three cases: // // 1) pageStarts[pageIndex] == DYLD_CACHE_SLIDE_PAGE_ATTR_NO_REBASE // The page contains no values that need rebasing. // // 2) (pageStarts[pageIndex] & DYLD_CACHE_SLIDE_PAGE_ATTR_EXTRA) == 0 // All rebase locations are in one linked list. The offset of the first // rebase location in the page is pageStarts[pageIndex] * 4. // // 3) pageStarts[pageIndex] & DYLD_CACHE_SLIDE_PAGE_ATTR_EXTRA // Multiple linked lists are needed for all rebase locations in a page. // The pagesExtras array contains 2 or more entries each of which is the // start of a new linked list in the page. The first is at: // extrasStartIndex = (pageStarts[pageIndex] & 0x3FFF) // The next is at extrasStartIndex+1. The last is denoted by // having the high bit (DYLD_CACHE_SLIDE_PAGE_ATTR_END) of the pageExtras[] // set. // // For 64-bit architectures, there is always enough free bits to encode all // possible deltas. The info->delta_mask field shows where the delta is located // in the pointer. That value must be masked off (valueMask) before the slide // is added to the pointer. // // For 32-bit architectures, there are only three bits free (the three most // significant bits). To extract the delta, you must first subtract value_add // from the pointer value, then AND with delta_mask, then shift by deltaShift. // That still leaves a maximum delta to the next rebase location of 28 bytes. // To reduce the number or chains needed, an optimization was added. Turns // out zero is common in the DATA region. A zero can be turned into a // non-rebasing entry in the linked list. The can be done because nothing // in the shared cache should point out of its dylib to the start of the shared // cache. // // The code for processing a linked list (chain) is: // // uint32_t delta = 1; // while ( delta != 0 ) { // uint8_t* loc = pageStart + pageOffset; // uintptr_t rawValue = *((uintptr_t*)loc); // delta = ((rawValue & deltaMask) >> deltaShift); // uintptr_t newValue = (rawValue & valueMask); // if ( newValue != 0 ) { // newValue += valueAdd; // newValue += slideAmount; // } // *((uintptr_t*)loc) = newValue; // pageOffset += delta; // } // // struct dyld_cache_slide_info2 { uint32_t version; // currently 2 uint32_t page_size; // currently 4096 (may also be 16384) uint32_t page_starts_offset; uint32_t page_starts_count; uint32_t page_extras_offset; uint32_t page_extras_count; uint64_t delta_mask; // which (contiguous) set of bits contains the delta to the next rebase location uint64_t value_add; //uint16_t page_starts[page_starts_count]; //uint16_t page_extras[page_extras_count]; }; #define DYLD_CACHE_SLIDE_PAGE_ATTRS 0xC000 // high bits of uint16_t are flags #define DYLD_CACHE_SLIDE_PAGE_ATTR_EXTRA 0x8000 // index is into extras array (not starts array) #define DYLD_CACHE_SLIDE_PAGE_ATTR_NO_REBASE 0x4000 // page has no rebasing #define DYLD_CACHE_SLIDE_PAGE_ATTR_END 0x8000 // last chain entry for page struct dyld_cache_local_symbols_info { uint32_t nlistOffset; // offset into this chunk of nlist entries uint32_t nlistCount; // count of nlist entries uint32_t stringsOffset; // offset into this chunk of string pool uint32_t stringsSize; // byte count of string pool uint32_t entriesOffset; // offset into this chunk of array of dyld_cache_local_symbols_entry uint32_t entriesCount; // number of elements in dyld_cache_local_symbols_entry array }; struct dyld_cache_local_symbols_entry { uint32_t dylibOffset; // offset in cache file of start of dylib uint32_t nlistStartIndex; // start index of locals for this dylib uint32_t nlistCount; // number of local symbols for this dylib }; #define MACOSX_DYLD_SHARED_CACHE_DIR "/private/var/db/dyld/" #define IPHONE_DYLD_SHARED_CACHE_DIR "/System/Library/Caches/com.apple.dyld/" #define DYLD_SHARED_CACHE_BASE_NAME "dyld_shared_cache_" #define DYLD_SHARED_CACHE_DEVELOPMENT_EXT ".development" static const uint64_t kDyldSharedCacheTypeDevelopment = 0; static const uint64_t kDyldSharedCacheTypeProduction = 1; #endif // __DYLD_CACHE_FORMAT__