dyld3/shared-cache/dyld_cache_format.h

   1 /* -*- mode: C++; c-basic-offset: 4; tab-width: 4 -*-
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  24 #ifndef __DYLD_CACHE_FORMAT__
  25 #define __DYLD_CACHE_FORMAT__
  26
  27 #include <stdint.h>
  28 #include <uuid/uuid.h>
  29
  30
  31 struct dyld_cache_header
  32 {
  33     char        magic[16];              // e.g. "dyld_v0    i386"
  34     uint32_t    mappingOffset;          // file offset to first dyld_cache_mapping_info
  35     uint32_t    mappingCount;           // number of dyld_cache_mapping_info entries
  36     uint32_t    imagesOffset;           // file offset to first dyld_cache_image_info
  37     uint32_t    imagesCount;            // number of dyld_cache_image_info entries
  38     uint64_t    dyldBaseAddress;        // base address of dyld when cache was built
  39     uint64_t    codeSignatureOffset;    // file offset of code signature blob
  40     uint64_t    codeSignatureSize;      // size of code signature blob (zero means to end of file)
  41     uint64_t    slideInfoOffset;        // file offset of kernel slid info
  42     uint64_t    slideInfoSize;          // size of kernel slid info
  43     uint64_t    localSymbolsOffset;     // file offset of where local symbols are stored
  44     uint64_t    localSymbolsSize;       // size of local symbols information
  45     uint8_t     uuid[16];               // unique value for each shared cache file
  46     uint64_t    cacheType;              // 0 for development, 1 for production
  47     uint32_t    branchPoolsOffset;      // file offset to table of uint64_t pool addresses
  48     uint32_t    branchPoolsCount;       // number of uint64_t entries
  49     uint64_t    accelerateInfoAddr;     // (unslid) address of optimization info
  50     uint64_t    accelerateInfoSize;     // size of optimization info
  51     uint64_t    imagesTextOffset;       // file offset to first dyld_cache_image_text_info
  52     uint64_t    imagesTextCount;        // number of dyld_cache_image_text_info entries
  53     uint64_t    dylibsImageGroupAddr;   // (unslid) address of ImageGroup for dylibs in this cache
  54     uint64_t    dylibsImageGroupSize;   // size of ImageGroup for dylibs in this cache
  55     uint64_t    otherImageGroupAddr;    // (unslid) address of ImageGroup for other OS dylibs
  56     uint64_t    otherImageGroupSize;    // size of oImageGroup for other OS dylibs
  57     uint64_t    progClosuresAddr;       // (unslid) address of list of program launch closures
  58     uint64_t    progClosuresSize;       // size of list of program launch closures
  59     uint64_t    progClosuresTrieAddr;   // (unslid) address of trie of indexes into program launch closures
  60     uint64_t    progClosuresTrieSize;   // size of trie of indexes into program launch closures
  61     uint32_t    platform;               // platform number (macOS=1, etc)
  62     uint32_t    formatVersion        : 8, // launch_cache::binary_format::kFormatVersion
  63                 dylibsExpectedOnDisk : 1, // dyld should expect the dylib exists on disk and to compare inode/mtime to see if cache is valid
  64                 simulator            : 1; // for simulator of specified platform
  65     uint64_t    sharedRegionStart;      // base load address of cache if not slid
  66     uint64_t    sharedRegionSize;       // overall size of region cache can be mapped into
  67     uint64_t    maxSlide;               // runtime slide of cache can be between zero and this value
  68 };
  69
  70
  71 struct dyld_cache_mapping_info {
  72     uint64_t    address;
  73     uint64_t    size;
  74     uint64_t    fileOffset;
  75     uint32_t    maxProt;
  76     uint32_t    initProt;
  77 };
  78
  79 struct dyld_cache_image_info
  80 {
  81     uint64_t    address;
  82     uint64_t    modTime;
  83     uint64_t    inode;
  84     uint32_t    pathFileOffset;
  85     uint32_t    pad;
  86 };
  87
  88 struct dyld_cache_image_info_extra
  89 {
  90     uint64_t    exportsTrieAddr;        // address of trie in unslid cache
  91     uint64_t    weakBindingsAddr;
  92     uint32_t    exportsTrieSize;
  93     uint32_t    weakBindingsSize;
  94     uint32_t    dependentsStartArrayIndex;
  95     uint32_t    reExportsStartArrayIndex;
  96 };
  97
  98
  99 struct dyld_cache_accelerator_info
 100 {
 101     uint32_t    version;                // currently 1
 102     uint32_t    imageExtrasCount;       // does not include aliases
 103     uint32_t    imagesExtrasOffset;     // offset into this chunk of first dyld_cache_image_info_extra
 104     uint32_t    bottomUpListOffset;     // offset into this chunk to start of 16-bit array of sorted image indexes
 105     uint32_t    dylibTrieOffset;        // offset into this chunk to start of trie containing all dylib paths
 106     uint32_t    dylibTrieSize;          // size of trie containing all dylib paths
 107     uint32_t    initializersOffset;     // offset into this chunk to start of initializers list
 108     uint32_t    initializersCount;      // size of initializers list
 109     uint32_t    dofSectionsOffset;      // offset into this chunk to start of DOF sections list
 110     uint32_t    dofSectionsCount;       // size of initializers list
 111     uint32_t    reExportListOffset;     // offset into this chunk to start of 16-bit array of re-exports
 112     uint32_t    reExportCount;          // size of re-exports
 113     uint32_t    depListOffset;          // offset into this chunk to start of 16-bit array of dependencies (0x8000 bit set if upward)
 114     uint32_t    depListCount;           // size of dependencies
 115     uint32_t    rangeTableOffset;       // offset into this chunk to start of ss
 116     uint32_t    rangeTableCount;        // size of dependencies
 117     uint64_t    dyldSectionAddr;        // address of libdyld's __dyld section in unslid cache
 118 };
 119
 120 struct dyld_cache_accelerator_initializer
 121 {
 122     uint32_t    functionOffset;         // address offset from start of cache mapping
 123     uint32_t    imageIndex;
 124 };
 125
 126 struct dyld_cache_range_entry
 127 {
 128     uint64_t    startAddress;           // unslid address of start of region
 129     uint32_t    size;
 130     uint32_t    imageIndex;
 131 };
 132
 133 struct dyld_cache_accelerator_dof
 134 {
 135     uint64_t    sectionAddress;         // unslid address of start of region
 136     uint32_t    sectionSize;
 137     uint32_t    imageIndex;
 138 };
 139
 140 struct dyld_cache_image_text_info
 141 {
 142     uuid_t      uuid;
 143     uint64_t    loadAddress;            // unslid address of start of __TEXT
 144     uint32_t    textSegmentSize;
 145     uint32_t    pathOffset;             // offset from start of cache file
 146 };
 147
 148
 149 // The rebasing info is to allow the kernel to lazily rebase DATA pages of the
 150 // dyld shared cache.  Rebasing is adding the slide to interior pointers.
 151 struct dyld_cache_slide_info
 152 {
 153     uint32_t    version;        // currently 1
 154     uint32_t    toc_offset;
 155     uint32_t    toc_count;
 156     uint32_t    entries_offset;
 157     uint32_t    entries_count;
 158     uint32_t    entries_size;  // currently 128
 159     // uint16_t toc[toc_count];
 160     // entrybitmap entries[entries_count];
 161 };
 162
 163
 164 // The version 2 of the slide info uses a different compression scheme. Since
 165 // only interior pointers (pointers that point within the cache) are rebased
 166 // (slid), we know the possible range of the pointers and thus know there are
 167 // unused bits in each pointer.  We use those bits to form a linked list of
 168 // locations needing rebasing in each page.
 169 //
 170 // Definitions:
 171 //
 172 //  pageIndex = (pageAddress - startOfAllDataAddress)/info->page_size
 173 //  pageStarts[] = info + info->page_starts_offset
 174 //  pageExtras[] = info + info->page_extras_offset
 175 //  valueMask = ~(info->delta_mask)
 176 //  deltaShift = __builtin_ctzll(info->delta_mask) - 2
 177 //
 178 // There are three cases:
 179 //
 180 // 1) pageStarts[pageIndex] == DYLD_CACHE_SLIDE_PAGE_ATTR_NO_REBASE
 181 //    The page contains no values that need rebasing.
 182 //
 183 // 2) (pageStarts[pageIndex] & DYLD_CACHE_SLIDE_PAGE_ATTR_EXTRA) == 0
 184 //    All rebase locations are in one linked list. The offset of the first
 185 //    rebase location in the page is pageStarts[pageIndex] * 4.
 186 //
 187 // 3) pageStarts[pageIndex] & DYLD_CACHE_SLIDE_PAGE_ATTR_EXTRA
 188 //      Multiple linked lists are needed for all rebase locations in a page.
 189 //    The pagesExtras array contains 2 or more entries each of which is the
 190 //    start of a new linked list in the page. The first is at:
 191 //       extrasStartIndex = (pageStarts[pageIndex] & 0x3FFF)
 192 //      The next is at extrasStartIndex+1.  The last is denoted by
 193 //    having the high bit (DYLD_CACHE_SLIDE_PAGE_ATTR_END) of the pageExtras[]
 194 //    set.
 195 //
 196 // For 64-bit architectures, there is always enough free bits to encode all
 197 // possible deltas.  The info->delta_mask field shows where the delta is located
 198 // in the pointer.  That value must be masked off (valueMask) before the slide
 199 // is added to the pointer.
 200 //
 201 // For 32-bit architectures, there are only three bits free (the three most
 202 // significant bits). To extract the delta, you must first subtract value_add
 203 // from the pointer value, then AND with delta_mask, then shift by deltaShift.
 204 // That still leaves a maximum delta to the next rebase location of 28 bytes.
 205 // To reduce the number or chains needed, an optimization was added.  Turns
 206 // out zero is common in the DATA region.  A zero can be turned into a
 207 // non-rebasing entry in the linked list.  The can be done because nothing
 208 // in the shared cache should point out of its dylib to the start of the shared
 209 // cache.
 210 //
 211 // The code for processing a linked list (chain) is:
 212 //
 213 //    uint32_t delta = 1;
 214 //    while ( delta != 0 ) {
 215 //        uint8_t* loc = pageStart + pageOffset;
 216 //        uintptr_t rawValue = *((uintptr_t*)loc);
 217 //        delta = ((rawValue & deltaMask) >> deltaShift);
 218 //        uintptr_t newValue = (rawValue & valueMask);
 219 //        if ( newValue != 0 ) {
 220 //            newValue += valueAdd;
 221 //            newValue += slideAmount;
 222 //        }
 223 //        *((uintptr_t*)loc) = newValue;
 224 //        pageOffset += delta;
 225 //    }
 226 //
 227 //
 228 struct dyld_cache_slide_info2
 229 {
 230     uint32_t    version;            // currently 2
 231     uint32_t    page_size;          // currently 4096 (may also be 16384)
 232     uint32_t    page_starts_offset;
 233     uint32_t    page_starts_count;
 234     uint32_t    page_extras_offset;
 235     uint32_t    page_extras_count;
 236     uint64_t    delta_mask;         // which (contiguous) set of bits contains the delta to the next rebase location
 237     uint64_t    value_add;
 238     //uint16_t    page_starts[page_starts_count];
 239     //uint16_t    page_extras[page_extras_count];
 240 };
 241 #define DYLD_CACHE_SLIDE_PAGE_ATTRS                0xC000    // high bits of uint16_t are flags
 242 #define DYLD_CACHE_SLIDE_PAGE_ATTR_EXTRA        0x8000  // index is into extras array (not starts array)
 243 #define DYLD_CACHE_SLIDE_PAGE_ATTR_NO_REBASE    0x4000  // page has no rebasing
 244 #define DYLD_CACHE_SLIDE_PAGE_ATTR_END            0x8000  // last chain entry for page
 245
 246
 247 struct dyld_cache_local_symbols_info
 248 {
 249     uint32_t    nlistOffset;        // offset into this chunk of nlist entries
 250     uint32_t    nlistCount;         // count of nlist entries
 251     uint32_t    stringsOffset;      // offset into this chunk of string pool
 252     uint32_t    stringsSize;        // byte count of string pool
 253     uint32_t    entriesOffset;      // offset into this chunk of array of dyld_cache_local_symbols_entry
 254     uint32_t    entriesCount;       // number of elements in dyld_cache_local_symbols_entry array
 255 };
 256
 257 struct dyld_cache_local_symbols_entry
 258 {
 259     uint32_t    dylibOffset;        // offset in cache file of start of dylib
 260     uint32_t    nlistStartIndex;    // start index of locals for this dylib
 261     uint32_t    nlistCount;         // number of local symbols for this dylib
 262 };
 263
 264
 265
 266 #define MACOSX_DYLD_SHARED_CACHE_DIR       "/private/var/db/dyld/"
 267 #define IPHONE_DYLD_SHARED_CACHE_DIR       "/System/Library/Caches/com.apple.dyld/"
 268 #define DYLD_SHARED_CACHE_BASE_NAME        "dyld_shared_cache_"
 269 #define DYLD_SHARED_CACHE_DEVELOPMENT_EXT  ".development"
 270
 271 static const uint64_t kDyldSharedCacheTypeDevelopment = 0;
 272 static const uint64_t kDyldSharedCacheTypeProduction = 1;
 273
 274
 275
 276
 277 #endif // __DYLD_CACHE_FORMAT__
 278
 279