dyld3/SharedCacheRuntime.cpp

   1 /*
   2  * Copyright (c) 2017 Apple Inc. All rights reserved.
   3  *
   4  * @APPLE_LICENSE_HEADER_START@
   5  *
   6  * This file contains Original Code and/or Modifications of Original Code
   7  * as defined in and that are subject to the Apple Public Source License
   8  * Version 2.0 (the 'License'). You may not use this file except in
   9  * compliance with the License. Please obtain a copy of the License at
  10  * http://www.opensource.apple.com/apsl/ and read it before using this
  11  * file.
  12  *
  13  * The Original Code and all software distributed under the License are
  14  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  15  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  16  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  17  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  18  * Please see the License for the specific language governing rights and
  19  * limitations under the License.
  20  *
  21  * @APPLE_LICENSE_HEADER_END@
  22  */
  23
  24
  25
  26 #include <stdint.h>
  27 #include <string.h>
  28 #include <unistd.h>
  29 #include <fcntl.h>
  30 #include <sys/param.h>
  31 #include <sys/types.h>
  32 #include <sys/stat.h>
  33 #include <sys/syscall.h>
  34 #include <sys/syslog.h>
  35 #include <sys/sysctl.h>
  36 #include <sys/mman.h>
  37 #include <mach/mach.h>
  38 #include <mach-o/fat.h>
  39 #include <mach-o/loader.h>
  40 #include <mach-o/ldsyms.h>
  41 #include <mach/shared_region.h>
  42 #include <mach/mach.h>
  43 #include <Availability.h>
  44 #include <TargetConditionals.h>
  45
  46 #include "dyld_cache_format.h"
  47 #include "SharedCacheRuntime.h"
  48 #include "Loading.h"
  49 #include "BootArgs.h"
  50
  51 #define ENABLE_DYLIBS_TO_OVERRIDE_CACHE_SIZE 1024
  52
  53 // should be in mach/shared_region.h
  54 extern "C" int __shared_region_check_np(uint64_t* startaddress);
  55 extern "C" int __shared_region_map_and_slide_np(int fd, uint32_t count, const shared_file_mapping_np mappings[], long slide, const dyld_cache_slide_info2* slideInfo, size_t slideInfoSize);
  56
  57
  58 namespace dyld {
  59     extern int  my_stat(const char* path, struct stat* buf);
  60     extern int  my_open(const char* path, int flag, int other);
  61     extern void log(const char*, ...);
  62 }
  63
  64
  65 namespace dyld3 {
  66
  67
  68 struct CacheInfo
  69 {
  70     int                     fd;
  71     shared_file_mapping_np  mappings[3];
  72     uint64_t                slideInfoAddressUnslid;
  73     size_t                  slideInfoSize;
  74     uint64_t                sharedRegionStart;
  75     uint64_t                sharedRegionSize;
  76     uint64_t                maxSlide;
  77 };
  78
  79
  80
  81
  82 #if __i386__
  83     #define ARCH_NAME            "i386"
  84     #define ARCH_CACHE_MAGIC     "dyld_v1    i386"
  85 #elif __x86_64__
  86     #define ARCH_NAME            "x86_64"
  87     #define ARCH_CACHE_MAGIC     "dyld_v1  x86_64"
  88     #define ARCH_NAME_H          "x86_64h"
  89     #define ARCH_CACHE_MAGIC_H   "dyld_v1 x86_64h"
  90 #elif __ARM_ARCH_7K__
  91     #define ARCH_NAME            "armv7k"
  92     #define ARCH_CACHE_MAGIC     "dyld_v1  armv7k"
  93 #elif __ARM_ARCH_7A__
  94     #define ARCH_NAME            "armv7"
  95     #define ARCH_CACHE_MAGIC     "dyld_v1   armv7"
  96 #elif __ARM_ARCH_7S__
  97     #define ARCH_NAME            "armv7s"
  98     #define ARCH_CACHE_MAGIC     "dyld_v1  armv7s"
  99 #elif __arm64e__
 100     #define ARCH_NAME            "arm64e"
 101     #define ARCH_CACHE_MAGIC     "dyld_v1  arm64e"
 102 #elif __arm64__
 103     #if __LP64__
 104         #define ARCH_NAME            "arm64"
 105         #define ARCH_CACHE_MAGIC     "dyld_v1   arm64"
 106     #else
 107         #define ARCH_NAME            "arm64_32"
 108         #define ARCH_CACHE_MAGIC     "dyld_v1arm64_32"
 109     #endif
 110 #endif
 111
 112
 113 #if !TARGET_OS_SIMULATOR
 114 static void rebaseChainV2(uint8_t* pageContent, uint16_t startOffset, uintptr_t slideAmount, const dyld_cache_slide_info2* slideInfo)
 115 {
 116     const uintptr_t   deltaMask    = (uintptr_t)(slideInfo->delta_mask);
 117     const uintptr_t   valueMask    = ~deltaMask;
 118     const uintptr_t   valueAdd     = (uintptr_t)(slideInfo->value_add);
 119     const unsigned    deltaShift   = __builtin_ctzll(deltaMask) - 2;
 120
 121     uint32_t pageOffset = startOffset;
 122     uint32_t delta = 1;
 123     while ( delta != 0 ) {
 124         uint8_t* loc = pageContent + pageOffset;
 125         uintptr_t rawValue = *((uintptr_t*)loc);
 126         delta = (uint32_t)((rawValue & deltaMask) >> deltaShift);
 127         uintptr_t value = (rawValue & valueMask);
 128         if ( value != 0 ) {
 129             value += valueAdd;
 130             value += slideAmount;
 131         }
 132         *((uintptr_t*)loc) = value;
 133         //dyld::log("         pageOffset=0x%03X, loc=%p, org value=0x%08llX, new value=0x%08llX, delta=0x%X\n", pageOffset, loc, (uint64_t)rawValue, (uint64_t)value, delta);
 134         pageOffset += delta;
 135     }
 136 }
 137 #endif
 138
 139 #if !__LP64__ && !TARGET_OS_SIMULATOR
 140 static void rebaseChainV4(uint8_t* pageContent, uint16_t startOffset, uintptr_t slideAmount, const dyld_cache_slide_info4* slideInfo)
 141 {
 142     const uintptr_t   deltaMask    = (uintptr_t)(slideInfo->delta_mask);
 143     const uintptr_t   valueMask    = ~deltaMask;
 144     const uintptr_t   valueAdd     = (uintptr_t)(slideInfo->value_add);
 145     const unsigned    deltaShift   = __builtin_ctzll(deltaMask) - 2;
 146
 147     uint32_t pageOffset = startOffset;
 148     uint32_t delta = 1;
 149     while ( delta != 0 ) {
 150         uint8_t* loc = pageContent + pageOffset;
 151         uintptr_t rawValue = *((uintptr_t*)loc);
 152         delta = (uint32_t)((rawValue & deltaMask) >> deltaShift);
 153         uintptr_t value = (rawValue & valueMask);
 154         if ( (value & 0xFFFF8000) == 0 ) {
 155            // small positive non-pointer, use as-is
 156         }
 157         else if ( (value & 0x3FFF8000) == 0x3FFF8000 ) {
 158            // small negative non-pointer
 159            value |= 0xC0000000;
 160         }
 161         else {
 162             value += valueAdd;
 163             value += slideAmount;
 164         }
 165         *((uintptr_t*)loc) = value;
 166         //dyld::log("         pageOffset=0x%03X, loc=%p, org value=0x%08llX, new value=0x%08llX, delta=0x%X\n", pageOffset, loc, (uint64_t)rawValue, (uint64_t)value, delta);
 167         pageOffset += delta;
 168     }
 169 }
 170 #endif
 171
 172 static void getCachePath(const SharedCacheOptions& options, size_t pathBufferSize, char pathBuffer[])
 173 {
 174     // set cache dir
 175     if ( options.cacheDirOverride != nullptr ) {
 176         strlcpy(pathBuffer, options.cacheDirOverride, pathBufferSize);
 177     }
 178     else {
 179 #if __IPHONE_OS_VERSION_MIN_REQUIRED
 180         strlcpy(pathBuffer, IPHONE_DYLD_SHARED_CACHE_DIR, sizeof(IPHONE_DYLD_SHARED_CACHE_DIR));
 181 #else
 182         strlcpy(pathBuffer, MACOSX_DYLD_SHARED_CACHE_DIR, sizeof(MACOSX_DYLD_SHARED_CACHE_DIR));
 183 #endif
 184     }
 185
 186     // append file component of cache file
 187     if ( pathBuffer[strlen(pathBuffer)-1] != '/' )
 188         strlcat(pathBuffer, "/", pathBufferSize);
 189 #if __x86_64__ && !__IPHONE_OS_VERSION_MIN_REQUIRED
 190     if ( options.useHaswell ) {
 191         size_t len = strlen(pathBuffer);
 192         struct stat haswellStatBuf;
 193         strlcat(pathBuffer, DYLD_SHARED_CACHE_BASE_NAME ARCH_NAME_H, pathBufferSize);
 194         if ( dyld::my_stat(pathBuffer, &haswellStatBuf) == 0 )
 195             return;
 196         // no haswell cache file, use regular x86_64 cache
 197         pathBuffer[len] = '\0';
 198     }
 199 #endif
 200
 201     strlcat(pathBuffer, DYLD_SHARED_CACHE_BASE_NAME ARCH_NAME, pathBufferSize);
 202
 203 #if __IPHONE_OS_VERSION_MIN_REQUIRED && !TARGET_OS_SIMULATOR
 204     // use .development cache if it exists
 205     struct stat enableStatBuf;
 206     struct stat devCacheStatBuf;
 207     struct stat optCacheStatBuf;
 208     bool developmentDevice = dyld3::internalInstall();
 209     bool enableFileExists = (dyld::my_stat(IPHONE_DYLD_SHARED_CACHE_DIR "enable-dylibs-to-override-cache", &enableStatBuf) == 0);
 210     bool devCacheExists = (dyld::my_stat(IPHONE_DYLD_SHARED_CACHE_DIR DYLD_SHARED_CACHE_BASE_NAME ARCH_NAME DYLD_SHARED_CACHE_DEVELOPMENT_EXT, &devCacheStatBuf) == 0);
 211     bool optCacheExists = (dyld::my_stat(IPHONE_DYLD_SHARED_CACHE_DIR DYLD_SHARED_CACHE_BASE_NAME ARCH_NAME, &optCacheStatBuf) == 0);
 212     if ( !BootArgs::forceCustomerCache() && developmentDevice && ((enableFileExists && (enableStatBuf.st_size < ENABLE_DYLIBS_TO_OVERRIDE_CACHE_SIZE) && devCacheExists) || !optCacheExists) )
 213         strlcat(pathBuffer, DYLD_SHARED_CACHE_DEVELOPMENT_EXT, pathBufferSize);
 214 #endif
 215
 216 }
 217
 218
 219 int openSharedCacheFile(const SharedCacheOptions& options, SharedCacheLoadInfo* results)
 220 {
 221     getCachePath(options, sizeof(results->path), results->path);
 222     return dyld::my_open(results->path, O_RDONLY, 0);
 223 }
 224
 225 static bool validMagic(const SharedCacheOptions& options, const DyldSharedCache* cache)
 226 {
 227     if ( strcmp(cache->header.magic, ARCH_CACHE_MAGIC) == 0 )
 228         return true;
 229
 230 #if __x86_64__
 231     if ( options.useHaswell ) {
 232         if ( strcmp(cache->header.magic, ARCH_CACHE_MAGIC_H) == 0 )
 233             return true;
 234     }
 235 #endif
 236     return false;
 237 }
 238
 239
 240 static bool validPlatform(const SharedCacheOptions& options, const DyldSharedCache* cache)
 241 {
 242     // grandfather in old cache that does not have platform in header
 243     if ( cache->header.mappingOffset < 0xE0 )
 244         return true;
 245
 246     if ( cache->header.platform != (uint32_t)MachOFile::currentPlatform() )
 247         return false;
 248
 249 #if TARGET_OS_SIMULATOR
 250     if ( cache->header.simulator == 0 )
 251         return false;
 252 #else
 253     if ( cache->header.simulator != 0 )
 254         return false;
 255 #endif
 256
 257     return true;
 258 }
 259
 260 #if !TARGET_OS_SIMULATOR
 261 static void verboseSharedCacheMappings(const shared_file_mapping_np mappings[3])
 262 {
 263     for (int i=0; i < 3; ++i) {
 264         dyld::log("        0x%08llX->0x%08llX init=%x, max=%x %s%s%s\n",
 265             mappings[i].sfm_address, mappings[i].sfm_address+mappings[i].sfm_size-1,
 266             mappings[i].sfm_init_prot, mappings[i].sfm_init_prot,
 267             ((mappings[i].sfm_init_prot & VM_PROT_READ) ? "read " : ""),
 268             ((mappings[i].sfm_init_prot & VM_PROT_WRITE) ? "write " : ""),
 269             ((mappings[i].sfm_init_prot & VM_PROT_EXECUTE) ? "execute " : ""));
 270     }
 271 }
 272 #endif
 273
 274 static bool preflightCacheFile(const SharedCacheOptions& options, SharedCacheLoadInfo* results, CacheInfo* info)
 275 {
 276
 277     // find and open shared cache file
 278     int fd = openSharedCacheFile(options, results);
 279     if ( fd == -1 ) {
 280         results->errorMessage = "shared cache file open() failed";
 281         return false;
 282     }
 283
 284     struct stat cacheStatBuf;
 285     if ( dyld::my_stat(results->path, &cacheStatBuf) != 0 ) {
 286         results->errorMessage = "shared cache file stat() failed";
 287         ::close(fd);
 288         return false;
 289     }
 290     size_t cacheFileLength = (size_t)(cacheStatBuf.st_size);
 291
 292     // sanity check header and mappings
 293     uint8_t firstPage[0x4000];
 294     if ( ::pread(fd, firstPage, sizeof(firstPage), 0) != sizeof(firstPage) ) {
 295         results->errorMessage = "shared cache file pread() failed";
 296         ::close(fd);
 297         return false;
 298     }
 299     const DyldSharedCache* cache = (DyldSharedCache*)firstPage;
 300     if ( !validMagic(options, cache) ) {
 301         results->errorMessage = "shared cache file has wrong magic";
 302         ::close(fd);
 303         return false;
 304     }
 305     if ( !validPlatform(options, cache) ) {
 306         results->errorMessage = "shared cache file is for a different platform";
 307         ::close(fd);
 308         return false;
 309     }
 310     if ( (cache->header.mappingCount != 3) || (cache->header.mappingOffset > 0x138) ) {
 311         results->errorMessage = "shared cache file mappings are invalid";
 312         ::close(fd);
 313         return false;
 314     }
 315     const dyld_cache_mapping_info* const fileMappings = (dyld_cache_mapping_info*)&firstPage[cache->header.mappingOffset];
 316     if (  (fileMappings[0].fileOffset != 0)
 317       || ((fileMappings[0].address + fileMappings[0].size) > fileMappings[1].address)
 318       || ((fileMappings[1].address + fileMappings[1].size) > fileMappings[2].address)
 319       || ((fileMappings[0].fileOffset + fileMappings[0].size) != fileMappings[1].fileOffset)
 320       || ((fileMappings[1].fileOffset + fileMappings[1].size) != fileMappings[2].fileOffset)
 321       || ((cache->header.codeSignatureOffset + cache->header.codeSignatureSize) != cacheFileLength)
 322       || (fileMappings[0].maxProt != (VM_PROT_READ|VM_PROT_EXECUTE))
 323       || (fileMappings[1].maxProt != (VM_PROT_READ|VM_PROT_WRITE))
 324       || (fileMappings[2].maxProt != VM_PROT_READ) ) {
 325         results->errorMessage = "shared cache file mappings are invalid";
 326         ::close(fd);
 327         return false;
 328     }
 329
 330     if ( cache->header.mappingOffset >= 0xF8 ) {
 331         if ( (fileMappings[0].address != cache->header.sharedRegionStart) || ((fileMappings[2].address + fileMappings[2].size) > (cache->header.sharedRegionStart+cache->header.sharedRegionSize)) ) {
 332             results->errorMessage = "shared cache file mapping addressses invalid";
 333             ::close(fd);
 334             return false;
 335         }
 336     }
 337     else {
 338         if ( (fileMappings[0].address != SHARED_REGION_BASE) || ((fileMappings[2].address + fileMappings[2].size) > (SHARED_REGION_BASE+SHARED_REGION_SIZE)) ) {
 339             results->errorMessage = "shared cache file mapping addressses invalid";
 340             ::close(fd);
 341             return false;
 342         }
 343     }
 344
 345     // register code signature of cache file
 346     fsignatures_t siginfo;
 347     siginfo.fs_file_start = 0;  // cache always starts at beginning of file
 348     siginfo.fs_blob_start = (void*)cache->header.codeSignatureOffset;
 349     siginfo.fs_blob_size  = (size_t)(cache->header.codeSignatureSize);
 350     int result = fcntl(fd, F_ADDFILESIGS_RETURN, &siginfo);
 351     if ( result == -1 ) {
 352         results->errorMessage = "code signature registration for shared cache failed";
 353         ::close(fd);
 354         return false;
 355     }
 356
 357     // <rdar://problem/23188073> validate code signature covers entire shared cache
 358     uint64_t codeSignedLength = siginfo.fs_file_start;
 359     if ( codeSignedLength < cache->header.codeSignatureOffset ) {
 360         results->errorMessage = "code signature does not cover entire shared cache file";
 361         ::close(fd);
 362         return false;
 363     }
 364     void* mappedData = ::mmap(NULL, sizeof(firstPage), PROT_READ|PROT_EXEC, MAP_PRIVATE, fd, 0);
 365     if ( mappedData == MAP_FAILED ) {
 366         results->errorMessage = "first page of shared cache not mmap()able";
 367         ::close(fd);
 368         return false;
 369     }
 370     if ( memcmp(mappedData, firstPage, sizeof(firstPage)) != 0 ) {
 371         results->errorMessage = "first page of mmap()ed shared cache not valid";
 372         ::close(fd);
 373         return false;
 374     }
 375     ::munmap(mappedData, sizeof(firstPage));
 376
 377     // fill out results
 378     info->fd = fd;
 379     for (int i=0; i < 3; ++i) {
 380         info->mappings[i].sfm_address       = fileMappings[i].address;
 381         info->mappings[i].sfm_size          = fileMappings[i].size;
 382         info->mappings[i].sfm_file_offset   = fileMappings[i].fileOffset;
 383         info->mappings[i].sfm_max_prot      = fileMappings[i].maxProt;
 384         info->mappings[i].sfm_init_prot     = fileMappings[i].initProt;
 385     }
 386     info->mappings[1].sfm_max_prot  |= VM_PROT_SLIDE;
 387     info->mappings[1].sfm_init_prot |= VM_PROT_SLIDE;
 388     info->slideInfoAddressUnslid  = fileMappings[2].address + cache->header.slideInfoOffset - fileMappings[2].fileOffset;
 389     info->slideInfoSize           = (long)cache->header.slideInfoSize;
 390     if ( cache->header.mappingOffset >= 0xf8 ) {
 391         info->sharedRegionStart = cache->header.sharedRegionStart;
 392         info->sharedRegionSize  = cache->header.sharedRegionSize;
 393         info->maxSlide          = cache->header.maxSlide;
 394     }
 395     else {
 396         info->sharedRegionStart = SHARED_REGION_BASE;
 397         info->sharedRegionSize  = SHARED_REGION_SIZE;
 398         info->maxSlide          = SHARED_REGION_SIZE - (fileMappings[2].address + fileMappings[2].size - fileMappings[0].address);
 399     }
 400     return true;
 401 }
 402
 403
 404 #if !TARGET_OS_SIMULATOR
 405
 406 // update all __DATA pages with slide info
 407 static bool rebaseDataPages(bool isVerbose, CacheInfo& info, SharedCacheLoadInfo* results)
 408 {
 409     uint64_t dataPagesStart = info.mappings[1].sfm_address;
 410     const dyld_cache_slide_info* slideInfo = nullptr;
 411     if ( info.slideInfoSize != 0 ) {
 412         slideInfo = (dyld_cache_slide_info*)(info.slideInfoAddressUnslid + results->slide);
 413     }
 414     const dyld_cache_slide_info* slideInfoHeader = (dyld_cache_slide_info*)slideInfo;
 415     if ( slideInfoHeader != nullptr ) {
 416         if ( slideInfoHeader->version == 2 ) {
 417             const dyld_cache_slide_info2* slideHeader = (dyld_cache_slide_info2*)slideInfo;
 418             const uint32_t  page_size = slideHeader->page_size;
 419             const uint16_t* page_starts = (uint16_t*)((long)(slideInfo) + slideHeader->page_starts_offset);
 420             const uint16_t* page_extras = (uint16_t*)((long)(slideInfo) + slideHeader->page_extras_offset);
 421             for (int i=0; i < slideHeader->page_starts_count; ++i) {
 422                 uint8_t* page = (uint8_t*)(long)(dataPagesStart + (page_size*i));
 423                 uint16_t pageEntry = page_starts[i];
 424                 //dyld::log("page[%d]: page_starts[i]=0x%04X\n", i, pageEntry);
 425                 if ( pageEntry == DYLD_CACHE_SLIDE_PAGE_ATTR_NO_REBASE )
 426                     continue;
 427                 if ( pageEntry & DYLD_CACHE_SLIDE_PAGE_ATTR_EXTRA ) {
 428                     uint16_t chainIndex = (pageEntry & 0x3FFF);
 429                     bool done = false;
 430                     while ( !done ) {
 431                         uint16_t pInfo = page_extras[chainIndex];
 432                         uint16_t pageStartOffset = (pInfo & 0x3FFF)*4;
 433                         //dyld::log("     chain[%d] pageOffset=0x%03X\n", chainIndex, pageStartOffset);
 434                         rebaseChainV2(page, pageStartOffset, results->slide, slideHeader);
 435                         done = (pInfo & DYLD_CACHE_SLIDE_PAGE_ATTR_END);
 436                         ++chainIndex;
 437                     }
 438                 }
 439                 else {
 440                     uint32_t pageOffset = pageEntry * 4;
 441                     //dyld::log("     start pageOffset=0x%03X\n", pageOffset);
 442                     rebaseChainV2(page, pageOffset, results->slide, slideHeader);
 443                 }
 444             }
 445         }
 446 #if __LP64__
 447         else if ( slideInfoHeader->version == 3 ) {
 448              const dyld_cache_slide_info3* slideHeader = (dyld_cache_slide_info3*)slideInfo;
 449              const uint32_t                pageSize    = slideHeader->page_size;
 450              for (int i=0; i < slideHeader->page_starts_count; ++i) {
 451                  uint8_t* page = (uint8_t*)(dataPagesStart + (pageSize*i));
 452                  uint64_t delta = slideHeader->page_starts[i];
 453                  if ( delta == DYLD_CACHE_SLIDE_V3_PAGE_ATTR_NO_REBASE )
 454                      continue;
 455                  delta = delta/sizeof(uint64_t); // initial offset is byte based
 456                  dyld_cache_slide_pointer3* loc = (dyld_cache_slide_pointer3*)page;
 457                  do {
 458                      loc += delta;
 459                      delta = loc->plain.offsetToNextPointer;
 460                      if ( loc->auth.authenticated ) {
 461 #if __has_feature(ptrauth_calls)
 462                         uint64_t target = info.sharedRegionStart + loc->auth.offsetFromSharedCacheBase + results->slide;
 463                         MachOLoaded::ChainedFixupPointerOnDisk ptr;
 464                         ptr.raw64 = *((uint64_t*)loc);
 465                         loc->raw = ptr.arm64e.signPointer(loc, target);
 466 #else
 467                         results->errorMessage = "invalid pointer kind in cache file";
 468                         return false;
 469 #endif
 470                      }
 471                      else {
 472                         MachOLoaded::ChainedFixupPointerOnDisk ptr;
 473                         ptr.raw64 = *((uint64_t*)loc);
 474                         loc->raw = ptr.arm64e.unpackTarget() + results->slide;
 475                      }
 476                 } while (delta != 0);
 477             }
 478         }
 479 #else
 480         else if ( slideInfoHeader->version == 4 ) {
 481             const dyld_cache_slide_info4* slideHeader = (dyld_cache_slide_info4*)slideInfo;
 482             const uint32_t  page_size = slideHeader->page_size;
 483             const uint16_t* page_starts = (uint16_t*)((long)(slideInfo) + slideHeader->page_starts_offset);
 484             const uint16_t* page_extras = (uint16_t*)((long)(slideInfo) + slideHeader->page_extras_offset);
 485             for (int i=0; i < slideHeader->page_starts_count; ++i) {
 486                 uint8_t* page = (uint8_t*)(long)(dataPagesStart + (page_size*i));
 487                 uint16_t pageEntry = page_starts[i];
 488                 //dyld::log("page[%d]: page_starts[i]=0x%04X\n", i, pageEntry);
 489                 if ( pageEntry == DYLD_CACHE_SLIDE4_PAGE_NO_REBASE )
 490                     continue;
 491                 if ( pageEntry & DYLD_CACHE_SLIDE4_PAGE_USE_EXTRA ) {
 492                     uint16_t chainIndex = (pageEntry & DYLD_CACHE_SLIDE4_PAGE_INDEX);
 493                     bool done = false;
 494                     while ( !done ) {
 495                         uint16_t pInfo = page_extras[chainIndex];
 496                         uint16_t pageStartOffset = (pInfo & DYLD_CACHE_SLIDE4_PAGE_INDEX)*4;
 497                         //dyld::log("     chain[%d] pageOffset=0x%03X\n", chainIndex, pageStartOffset);
 498                         rebaseChainV4(page, pageStartOffset, results->slide, slideHeader);
 499                         done = (pInfo & DYLD_CACHE_SLIDE4_PAGE_EXTRA_END);
 500                         ++chainIndex;
 501                     }
 502                 }
 503                 else {
 504                     uint32_t pageOffset = pageEntry * 4;
 505                     //dyld::log("     start pageOffset=0x%03X\n", pageOffset);
 506                     rebaseChainV4(page, pageOffset, results->slide, slideHeader);
 507                 }
 508             }
 509         }
 510 #endif // LP64
 511         else {
 512             results->errorMessage = "invalid slide info in cache file";
 513             return false;
 514         }
 515     }
 516     return true;
 517 }
 518
 519 static bool reuseExistingCache(const SharedCacheOptions& options, SharedCacheLoadInfo* results)
 520 {
 521     uint64_t cacheBaseAddress;
 522 #if __i386__
 523     if ( syscall(294, &cacheBaseAddress) == 0 ) {
 524 #else
 525     if ( __shared_region_check_np(&cacheBaseAddress) == 0 ) {
 526 #endif
 527         const DyldSharedCache* existingCache = (DyldSharedCache*)cacheBaseAddress;
 528         if ( validMagic(options, existingCache) ) {
 529             const dyld_cache_mapping_info* const fileMappings = (dyld_cache_mapping_info*)(cacheBaseAddress + existingCache->header.mappingOffset);
 530             results->loadAddress = existingCache;
 531             results->slide = (long)(cacheBaseAddress - fileMappings[0].address);
 532             // we don't know the path this cache was previously loaded from, assume default
 533             getCachePath(options, sizeof(results->path), results->path);
 534             if ( options.verbose ) {
 535                 const shared_file_mapping_np* const mappings = (shared_file_mapping_np*)(cacheBaseAddress + existingCache->header.mappingOffset);
 536                 dyld::log("re-using existing shared cache (%s):\n", results->path);
 537                 shared_file_mapping_np slidMappings[3];
 538                 for (int i=0; i < 3; ++i) {
 539                     slidMappings[i] = mappings[i];
 540                     slidMappings[i].sfm_address += results->slide;
 541                 }
 542                 verboseSharedCacheMappings(slidMappings);
 543             }
 544         }
 545         else {
 546             results->errorMessage = "existing shared cache in memory is not compatible";
 547         }
 548         return true;
 549     }
 550     return false;
 551 }
 552
 553 static long pickCacheASLR(CacheInfo& info)
 554 {
 555     // choose new random slide
 556 #if __IPHONE_OS_VERSION_MIN_REQUIRED
 557     // <rdar://problem/20848977> change shared cache slide for 32-bit arm to always be 16k aligned
 558     long slide = ((arc4random() % info.maxSlide) & (-16384));
 559 #else
 560     long slide = ((arc4random() % info.maxSlide) & (-4096));
 561 #endif
 562
 563     // <rdar://problem/32031197> respect -disable_aslr boot-arg
 564     if ( BootArgs::contains("-disable_aslr") )
 565         slide = 0;
 566
 567     // update mappings
 568     for (uint32_t i=0; i < 3; ++i) {
 569         info.mappings[i].sfm_address += slide;
 570     }
 571
 572     return slide;
 573 }
 574
 575 static bool mapCacheSystemWide(const SharedCacheOptions& options, SharedCacheLoadInfo* results)
 576 {
 577     CacheInfo info;
 578     if ( !preflightCacheFile(options, results, &info) )
 579         return false;
 580
 581     const dyld_cache_slide_info2* slideInfo = nullptr;
 582     if ( info.slideInfoSize != 0 ) {
 583         results->slide = pickCacheASLR(info);
 584         slideInfo = (dyld_cache_slide_info2*)(info.slideInfoAddressUnslid + results->slide);
 585     }
 586
 587     int result = __shared_region_map_and_slide_np(info.fd, 3, info.mappings, results->slide, slideInfo, info.slideInfoSize);
 588     ::close(info.fd);
 589     if ( result == 0 ) {
 590         results->loadAddress = (const DyldSharedCache*)(info.mappings[0].sfm_address);
 591     }
 592     else {
 593         // could be another process beat us to it
 594         if ( reuseExistingCache(options, results) )
 595             return true;
 596         // if cache does not exist, then really is an error
 597         if ( results->errorMessage == nullptr )
 598             results->errorMessage = "syscall to map cache into shared region failed";
 599         return false;
 600     }
 601
 602     if ( options.verbose ) {
 603         dyld::log("mapped dyld cache file system wide: %s\n", results->path);
 604         verboseSharedCacheMappings(info.mappings);
 605     }
 606     return true;
 607 }
 608 #endif // TARGET_OS_SIMULATOR
 609
 610 static bool mapCachePrivate(const SharedCacheOptions& options, SharedCacheLoadInfo* results)
 611 {
 612     // open and validate cache file
 613     CacheInfo info;
 614     if ( !preflightCacheFile(options, results, &info) )
 615         return false;
 616
 617     // compute ALSR slide
 618     results->slide = 0;
 619 #if !TARGET_OS_SIMULATOR // simulator caches do not support sliding
 620     if ( info.slideInfoSize != 0 ) {
 621         results->slide = pickCacheASLR(info);
 622     }
 623 #endif
 624     results->loadAddress = (const DyldSharedCache*)(info.mappings[0].sfm_address);
 625
 626     // deallocate any existing system wide shared cache
 627     deallocateExistingSharedCache();
 628
 629 #if TARGET_OS_SIMULATOR && TARGET_OS_WATCH
 630     // <rdar://problem/50887685> watchOS 32-bit cache does not overlap macOS dyld cache address range
 631     // mmap() of a file needs a vm_allocation behind it, so make one
 632     vm_address_t loadAddress = 0x40000000;
 633     ::vm_allocate(mach_task_self(), &loadAddress, 0x40000000, VM_FLAGS_FIXED);
 634 #endif
 635
 636     // map cache just for this process with mmap()
 637     for (int i=0; i < 3; ++i) {
 638         void* mmapAddress = (void*)(uintptr_t)(info.mappings[i].sfm_address);
 639         size_t size = (size_t)(info.mappings[i].sfm_size);
 640         //dyld::log("dyld: mapping address %p with size 0x%08lX\n", mmapAddress, size);
 641         int protection = 0;
 642         if ( info.mappings[i].sfm_init_prot & VM_PROT_EXECUTE )
 643             protection   |= PROT_EXEC;
 644         if ( info.mappings[i].sfm_init_prot & VM_PROT_READ )
 645             protection   |= PROT_READ;
 646         if ( info.mappings[i].sfm_init_prot & VM_PROT_WRITE )
 647             protection   |= PROT_WRITE;
 648         off_t offset = info.mappings[i].sfm_file_offset;
 649         if ( ::mmap(mmapAddress, size, protection, MAP_FIXED | MAP_PRIVATE, info.fd, offset) != mmapAddress ) {
 650             // failed to map some chunk of this shared cache file
 651             // clear shared region
 652             ::mmap((void*)((long)SHARED_REGION_BASE), SHARED_REGION_SIZE, PROT_NONE, MAP_FIXED | MAP_PRIVATE| MAP_ANON, 0, 0);
 653             // return failure
 654             results->loadAddress        = nullptr;
 655             results->errorMessage       = "could not mmap() part of dyld cache";
 656             ::close(info.fd);
 657             return false;
 658         }
 659     }
 660     ::close(info.fd);
 661
 662 #if TARGET_OS_SIMULATOR // simulator caches do not support sliding
 663     return true;
 664 #else
 665     bool success = rebaseDataPages(options.verbose, info, results);
 666
 667     if ( options.verbose ) {
 668         dyld::log("mapped dyld cache file private to process (%s):\n", results->path);
 669         verboseSharedCacheMappings(info.mappings);
 670     }
 671     return success;
 672 #endif
 673 }
 674
 675
 676
 677 bool loadDyldCache(const SharedCacheOptions& options, SharedCacheLoadInfo* results)
 678 {
 679     results->loadAddress        = 0;
 680     results->slide              = 0;
 681     results->errorMessage       = nullptr;
 682
 683 #if TARGET_OS_SIMULATOR
 684     // simulator only supports mmap()ing cache privately into process
 685     return mapCachePrivate(options, results);
 686 #else
 687     if ( options.forcePrivate ) {
 688         // mmap cache into this process only
 689         return mapCachePrivate(options, results);
 690     }
 691     else {
 692         // fast path: when cache is already mapped into shared region
 693         bool hasError = false;
 694         if ( reuseExistingCache(options, results) ) {
 695             hasError = (results->errorMessage != nullptr);
 696         } else {
 697             // slow path: this is first process to load cache
 698             hasError = mapCacheSystemWide(options, results);
 699         }
 700         return hasError;
 701     }
 702 #endif
 703 }
 704
 705
 706 bool findInSharedCacheImage(const SharedCacheLoadInfo& loadInfo, const char* dylibPathToFind, SharedCacheFindDylibResults* results)
 707 {
 708     if ( loadInfo.loadAddress == nullptr )
 709         return false;
 710
 711     if ( loadInfo.loadAddress->header.formatVersion != dyld3::closure::kFormatVersion ) {
 712         // support for older cache with a different Image* format
 713 #if __IPHONE_OS_VERSION_MIN_REQUIRED
 714         uint64_t hash = 0;
 715         for (const char* s=dylibPathToFind; *s != '\0'; ++s)
 716                 hash += hash*4 + *s;
 717 #endif
 718         const dyld_cache_image_info* const start = (dyld_cache_image_info*)((uint8_t*)loadInfo.loadAddress + loadInfo.loadAddress->header.imagesOffset);
 719         const dyld_cache_image_info* const end = &start[loadInfo.loadAddress->header.imagesCount];
 720         for (const dyld_cache_image_info* p = start; p != end; ++p) {
 721 #if __IPHONE_OS_VERSION_MIN_REQUIRED
 722             // on iOS, inode is used to hold hash of path
 723             if ( (p->modTime == 0) && (p->inode != hash) )
 724                 continue;
 725 #endif
 726             const char* aPath = (char*)loadInfo.loadAddress + p->pathFileOffset;
 727             if ( strcmp(aPath, dylibPathToFind) == 0 ) {
 728                 results->mhInCache    = (const mach_header*)(p->address+loadInfo.slide);
 729                 results->pathInCache  = aPath;
 730                 results->slideInCache = loadInfo.slide;
 731                 results->image        = nullptr;
 732                 return true;
 733             }
 734         }
 735         return false;
 736     }
 737
 738     const dyld3::closure::ImageArray* images = loadInfo.loadAddress->cachedDylibsImageArray();
 739     results->image = nullptr;
 740     uint32_t imageIndex;
 741     if ( loadInfo.loadAddress->hasImagePath(dylibPathToFind, imageIndex) ) {
 742         results->image = images->imageForNum(imageIndex+1);
 743     }
 744  #if __MAC_OS_X_VERSION_MIN_REQUIRED
 745     else {
 746         // <rdar://problem/32740215> handle symlink to cached dylib
 747         if ( loadInfo.loadAddress->header.dylibsExpectedOnDisk ) {
 748             struct stat statBuf;
 749             if ( dyld::my_stat(dylibPathToFind, &statBuf) == 0 ) {
 750                 // on macOS we store the inode and mtime of each dylib in the cache in the dyld_cache_image_info array
 751                 const dyld_cache_image_info* const start = (dyld_cache_image_info*)((uint8_t*)loadInfo.loadAddress + loadInfo.loadAddress->header.imagesOffset);
 752                 const dyld_cache_image_info* const end = &start[loadInfo.loadAddress->header.imagesCount];
 753                 for (const dyld_cache_image_info* p = start; p != end; ++p) {
 754                     if ( (p->inode == statBuf.st_ino) && (p->modTime == statBuf.st_mtime) ) {
 755                         imageIndex = (uint32_t)(p - start);
 756                         results->image = images->imageForNum(imageIndex+1);
 757                         break;
 758                     }
 759                 }
 760             }
 761         }
 762         else {
 763             char resolvedPath[PATH_MAX];
 764             if ( realpath(dylibPathToFind, resolvedPath) != nullptr ) {
 765                 if ( loadInfo.loadAddress->hasImagePath(resolvedPath, imageIndex) ) {
 766                     results->image = images->imageForNum(imageIndex+1);
 767                 }
 768             }
 769         }
 770     }
 771 #endif
 772     if ( results->image == nullptr )
 773         return false;
 774
 775     results->mhInCache    = (const mach_header*)((uintptr_t)loadInfo.loadAddress + results->image->cacheOffset());
 776     results->pathInCache  = results->image->path();
 777     results->slideInCache = loadInfo.slide;
 778     return true;
 779 }
 780
 781
 782 bool pathIsInSharedCacheImage(const SharedCacheLoadInfo& loadInfo, const char* dylibPathToFind)
 783 {
 784     if ( (loadInfo.loadAddress == nullptr) )
 785         return false;
 786
 787     uint32_t imageIndex;
 788     return loadInfo.loadAddress->hasImagePath(dylibPathToFind, imageIndex);
 789 }
 790
 791 void deallocateExistingSharedCache()
 792 {
 793 #if TARGET_OS_SIMULATOR
 794     // dyld deallocated macOS shared cache before jumping into dyld_sim
 795 #else
 796     // <rdar://problem/5077374> remove the shared region sub-map
 797     uint64_t existingCacheAddress = 0;
 798     if ( __shared_region_check_np(&existingCacheAddress) == 0 ) {
 799         ::mmap((void*)((long)SHARED_REGION_BASE), SHARED_REGION_SIZE, PROT_NONE, MAP_FIXED | MAP_PRIVATE| MAP_ANON, 0, 0);
 800     }
 801 #endif
 802
 803 }
 804
 805 } // namespace dyld3
 806