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dyld3/shared-cache/update_dyld_shared_cache.cpp dyld-832.7.3 dyld-655.1
--- dyld/dyld-832.7.3/dyld3/shared-cache/update_dyld_shared_cache.cpp
+++ dyld/dyld-655.1/dyld3/shared-cache/update_dyld_shared_cache.cpp
@@ -25,6 +25,9 @@
 #include <sys/types.h>
 #include <sys/stat.h>
 #include <sys/mman.h>
+#include <mach/mach.h>
+#include <mach/mach_time.h>
+#include <mach-o/dyld.h>
 #include <limits.h>
 #include <stdarg.h>
 #include <stdio.h>
@@ -37,11 +40,855 @@
 #include <assert.h>
 #include <sys/uio.h>
 #include <unistd.h>
-
+#include <sys/param.h>
+#include <sys/sysctl.h>
+#include <sys/resource.h>
+#include <dirent.h>
+#include <rootless.h>
+#include <dscsym.h>
+#include <dispatch/dispatch.h>
+#include <pthread/pthread.h>
+#include <Bom/Bom.h>
+#include <CoreFoundation/CoreFoundation.h>
+
+#include <algorithm>
+#include <vector>
+#include <unordered_set>
+#include <unordered_set>
+#include <iostream>
+#include <fstream>
+
+#include "FileUtils.h"
+#include "StringUtils.h"
+#include "DyldSharedCache.h"
+#include "MachOFile.h"
+#include "MachOAnalyzer.h"
+#include "ClosureFileSystemPhysical.h"
+
+struct MappedMachOsByCategory
+{
+    std::string                                 archName;
+    std::vector<DyldSharedCache::MappedMachO>   dylibsForCache;
+    std::vector<DyldSharedCache::MappedMachO>   otherDylibsAndBundles;
+    std::vector<DyldSharedCache::MappedMachO>   mainExecutables;
+};
+
+static const char* sAllowedPrefixes[] = {
+    "/bin/",
+    "/sbin/",
+    "/usr/",
+    "/System",
+    "/Applications/App Store.app/",
+    "/Applications/Automator.app/",
+    "/Applications/Calculator.app/",
+    "/Applications/Calendar.app/",
+    "/Applications/Chess.app/",
+    "/Applications/Contacts.app/",
+//    "/Applications/DVD Player.app/",
+    "/Applications/Dashboard.app/",
+    "/Applications/Dictionary.app/",
+    "/Applications/FaceTime.app/",
+    "/Applications/Font Book.app/",
+    "/Applications/Image Capture.app/",
+    "/Applications/Launchpad.app/",
+    "/Applications/Mail.app/",
+    "/Applications/Maps.app/",
+    "/Applications/Messages.app/",
+    "/Applications/Mission Control.app/",
+    "/Applications/Notes.app/",
+    "/Applications/Photo Booth.app/",
+//    "/Applications/Photos.app/",
+    "/Applications/Preview.app/",
+    "/Applications/QuickTime Player.app/",
+    "/Applications/Reminders.app/",
+    "/Applications/Safari.app/",
+    "/Applications/Siri.app/",
+    "/Applications/Stickies.app/",
+    "/Applications/System Preferences.app/",
+    "/Applications/TextEdit.app/",
+    "/Applications/Time Machine.app/",
+    "/Applications/iBooks.app/",
+    "/Applications/iTunes.app/",
+    "/Applications/Utilities/Activity Monitor.app",
+    "/Applications/Utilities/AirPort Utility.app",
+    "/Applications/Utilities/Audio MIDI Setup.app",
+    "/Applications/Utilities/Bluetooth File Exchange.app",
+    "/Applications/Utilities/Boot Camp Assistant.app",
+    "/Applications/Utilities/ColorSync Utility.app",
+    "/Applications/Utilities/Console.app",
+    "/Applications/Utilities/Digital Color Meter.app",
+    "/Applications/Utilities/Disk Utility.app",
+    "/Applications/Utilities/Grab.app",
+    "/Applications/Utilities/Grapher.app",
+    "/Applications/Utilities/Keychain Access.app",
+    "/Applications/Utilities/Migration Assistant.app",
+    "/Applications/Utilities/Script Editor.app",
+    "/Applications/Utilities/System Information.app",
+    "/Applications/Utilities/Terminal.app",
+    "/Applications/Utilities/VoiceOver Utility.app",
+    "/Library/CoreMediaIO/Plug-Ins/DAL/"                // temp until plugins moved or closured working
+};
+
+static const char* sDontUsePrefixes[] = {
+    "/usr/share",
+    "/usr/local/",
+    "/System/Library/Assets",
+    "/System/Library/StagedFrameworks",
+    "/System/Library/Kernels/",
+    "/bin/zsh",                             // until <rdar://31026756> is fixed
+    "/System/Library/Frameworks/CoreServices.framework/Versions/A/Frameworks/Metadata.framework/Versions/A/Support/mdworker", // these load third party plugins
+    "/usr/bin/mdimport", // these load third party plugins
+    "/System/Library/Developer/CoreSimulator/",  // ignore Marzipan
+};
+
+
+static bool verbose = false;
+
+
+
+static bool addIfMachO(const dyld3::closure::FileSystem& fileSystem, const std::string& runtimePath, const struct stat& statBuf, bool requireSIP,
+                       dev_t rootFS, std::vector<MappedMachOsByCategory>& files)
+{
+    // don't precompute closure info for any debug or profile dylibs
+    if ( endsWith(runtimePath, "_profile.dylib") || endsWith(runtimePath, "_debug.dylib") || endsWith(runtimePath, "_profile") || endsWith(runtimePath, "_debug") )
+        return false;
+    if ( startsWith(runtimePath, "/usr/lib/system/introspection/") )
+        return false;
+
+    // Only use files on the same volume as the boot volume
+    if (statBuf.st_dev != rootFS) {
+        if ( verbose )
+            fprintf(stderr, "update_dyld_shared_cache: warning: skipping overlay file '%s' which is not on the root volume\n", runtimePath.c_str());
+        return false;
+    }
+
+    auto warningHandler = ^(const char* msg) {
+        if ( verbose )
+            fprintf(stderr, "update_dyld_shared_cache: warning: cannot build dlopen closure for '%s' because %s\n", runtimePath.c_str(), msg);
+    };
+
+    bool result = false;
+    for (MappedMachOsByCategory& file : files) {
+        Diagnostics diag;
+        dyld3::closure::LoadedFileInfo loadedFileInfo = dyld3::MachOAnalyzer::load(diag, fileSystem, runtimePath.c_str(), file.archName.c_str(), dyld3::Platform::macOS);
+        const dyld3::MachOAnalyzer* ma = (const dyld3::MachOAnalyzer*)loadedFileInfo.fileContent;
+        if ( ma != nullptr ) {
+            bool sipProtected = false; // isProtectedBySIP(fd);
+            bool issetuid     = false;
+            if ( ma->isDynamicExecutable() ) {
+                // When SIP enabled, only build closures for SIP protected programs
+                if ( !requireSIP || sipProtected ) {
+                    //fprintf(stderr, "requireSIP=%d, sipProtected=%d, path=%s\n", requireSIP, sipProtected, fullPath.c_str());
+                    issetuid = (statBuf.st_mode & (S_ISUID|S_ISGID));
+                    file.mainExecutables.emplace_back(runtimePath, ma, loadedFileInfo.sliceLen, issetuid, sipProtected, loadedFileInfo.sliceOffset, statBuf.st_mtime, statBuf.st_ino);
+                }
+            }
+            else if ( ma->canBePlacedInDyldCache(runtimePath.c_str(), ^(const char* msg) {}) ) {
+                // when SIP is enabled, only dylib protected by SIP can go in cache
+                if ( !requireSIP || sipProtected )
+                    file.dylibsForCache.emplace_back(runtimePath, ma, loadedFileInfo.sliceLen, issetuid, sipProtected, loadedFileInfo.sliceOffset, statBuf.st_mtime, statBuf.st_ino);
+                else if ( ma->canHavePrecomputedDlopenClosure(runtimePath.c_str(), warningHandler) )
+                    file.otherDylibsAndBundles.emplace_back(runtimePath, ma, loadedFileInfo.sliceLen, issetuid, sipProtected, loadedFileInfo.sliceOffset, statBuf.st_mtime, statBuf.st_ino);
+            }
+            else {
+                if ( ma->isDylib() ) {
+                    std::string installName = ma->installName();
+                    if ( startsWith(installName, "@") && !contains(runtimePath, ".app/") && !contains(runtimePath, ".xpc/") ) {
+                        if ( startsWith(runtimePath, "/usr/lib/") || startsWith(runtimePath, "/System/Library/") )
+                            fprintf(stderr, "update_dyld_shared_cache: warning @rpath install name for system framework: %s\n", runtimePath.c_str());
+                    }
+                }
+                else if ( ma->canHavePrecomputedDlopenClosure(runtimePath.c_str(), warningHandler) ) {
+                    file.otherDylibsAndBundles.emplace_back(runtimePath, ma, loadedFileInfo.sliceLen, issetuid, sipProtected, loadedFileInfo.sliceOffset, statBuf.st_mtime, statBuf.st_ino);
+                }
+            }
+            result = true;
+        }
+    }
+
+    return result;
+}
+
+static void findAllFiles(const std::vector<std::string>& pathPrefixes, bool requireSIP, dev_t rootFS, std::vector<MappedMachOsByCategory>& files)
+{
+    std::unordered_set<std::string> skipDirs;
+    for (const char* s : sDontUsePrefixes)
+        skipDirs.insert(s);
+
+    __block std::unordered_set<std::string> alreadyUsed;
+    bool multiplePrefixes = (pathPrefixes.size() > 1);
+    for (const std::string& prefix : pathPrefixes) {
+        // get all files from overlay for this search dir
+        dyld3::closure::FileSystemPhysical fileSystem(prefix.c_str());
+        for (const char* searchDir : sAllowedPrefixes ) {
+            iterateDirectoryTree(prefix, searchDir, ^(const std::string& dirPath) { return (skipDirs.count(dirPath) != 0); }, ^(const std::string& path, const struct stat& statBuf) {
+                // ignore files that don't have 'x' bit set (all runnable mach-o files do)
+                const bool hasXBit = ((statBuf.st_mode & S_IXOTH) == S_IXOTH);
+                if ( !hasXBit && !endsWith(path, ".dylib") )
+                    return;
+
+                // ignore files too small
+                if ( statBuf.st_size < 0x3000 )
+                    return;
+
+                // don't add paths already found using previous prefix
+                if ( multiplePrefixes && (alreadyUsed.count(path) != 0) )
+                    return;
+
+                // if the file is mach-o, add to list
+                if ( addIfMachO(fileSystem, path, statBuf, requireSIP, rootFS, files) ) {
+                    if ( multiplePrefixes )
+                        alreadyUsed.insert(path);
+                }
+            });
+        }
+    }
+}
+
+
+static void findOSFilesViaBOMS(const std::vector<std::string>& pathPrefixes, bool requireSIP, dev_t rootFS, std::vector<MappedMachOsByCategory>& files)
+{
+    __block std::unordered_set<std::string> runtimePathsFound;
+    for (const std::string& prefix : pathPrefixes) {
+        iterateDirectoryTree(prefix, "/System/Library/Receipts", ^(const std::string&) { return false; }, ^(const std::string& path, const struct stat& statBuf) {
+            if ( !contains(path, "com.apple.pkg.") )
+                return;
+            if ( !endsWith(path, ".bom") )
+                return;
+            std::string fullPath = prefix + path;
+            BOMBom bom = BOMBomOpenWithSys(fullPath.c_str(), false, NULL);
+            if ( bom == nullptr )
+                return;
+            BOMFSObject rootFso = BOMBomGetRootFSObject(bom);
+            if ( rootFso == nullptr ) {
+                BOMBomFree(bom);
+                return;
+            }
+            BOMBomEnumerator e = BOMBomEnumeratorNew(bom, rootFso);
+            if ( e == nullptr ) {
+                fprintf(stderr, "Can't get enumerator for BOM root FSObject\n");
+                return;
+            }
+            BOMFSObjectFree(rootFso);
+            //fprintf(stderr, "using BOM %s\n", path.c_str());
+            while (BOMFSObject fso = BOMBomEnumeratorNext(e)) {
+                if ( BOMFSObjectIsBinaryObject(fso) ) {
+                    const char* runPath = BOMFSObjectPathName(fso);
+                    if ( (runPath[0] == '.') && (runPath[1] == '/') )
+                        ++runPath;
+                    if ( runtimePathsFound.count(runPath) == 0 ) {
+                        // only add files from sAllowedPrefixes and not in sDontUsePrefixes
+                        bool inSearchDir = false;
+                        for (const char* searchDir : sAllowedPrefixes ) {
+                            if ( strncmp(searchDir, runPath, strlen(searchDir)) == 0 )  {
+                                inSearchDir = true;
+                                break;
+                            }
+                        }
+                        if ( inSearchDir ) {
+                            bool inSkipDir = false;
+                            for (const char* skipDir : sDontUsePrefixes) {
+                                if ( strncmp(skipDir, runPath, strlen(skipDir)) == 0 )  {
+                                    inSkipDir = true;
+                                    break;
+                                }
+                            }
+                            if ( !inSkipDir ) {
+                                for (const std::string& prefix2 : pathPrefixes) {
+                                    struct stat statBuf2;
+                                    std::string fullPath2 = prefix2 + runPath;
+                                    if ( stat(fullPath2.c_str(), &statBuf2) == 0 ) {
+                                        dyld3::closure::FileSystemPhysical fileSystem(prefix2.c_str());
+                                        if ( addIfMachO(fileSystem, runPath, statBuf2, requireSIP, rootFS, files) ) {
+                                            runtimePathsFound.insert(runPath);
+                                            break;
+                                        }
+                                    }
+                                }
+                            }
+                        }
+                    }
+                }
+                BOMFSObjectFree(fso);
+            }
+
+            BOMBomEnumeratorFree(e);
+            BOMBomFree(bom);
+        });
+    }
+}
+
+
+static bool dontCache(const std::string& volumePrefix, const std::string& archName,
+                      const std::unordered_set<std::string>& pathsWithDuplicateInstallName,
+                      const DyldSharedCache::MappedMachO& aFile, bool warn,
+                      const std::unordered_set<std::string>& skipDylibs)
+{
+    if ( skipDylibs.count(aFile.runtimePath) )
+        return true;
+    if ( startsWith(aFile.runtimePath, "/usr/lib/system/introspection/") )
+        return true;
+    if ( startsWith(aFile.runtimePath, "/System/Library/QuickTime/") )
+        return true;
+    if ( startsWith(aFile.runtimePath, "/System/Library/Tcl/") )
+        return true;
+    if ( startsWith(aFile.runtimePath, "/System/Library/Perl/") )
+        return true;
+    if ( startsWith(aFile.runtimePath, "/System/Library/MonitorPanels/") )
+        return true;
+    if ( startsWith(aFile.runtimePath, "/System/Library/Accessibility/") )
+        return true;
+    if ( startsWith(aFile.runtimePath, "/usr/local/") )
+        return true;
+
+    // anything inside a .app bundle is specific to app, so should not be in shared cache
+    if ( aFile.runtimePath.find(".app/") != std::string::npos )
+        return true;
+
+    if ( archName == "i386" ) {
+        if ( startsWith(aFile.runtimePath, "/System/Library/CoreServices/") )
+            return true;
+        if ( startsWith(aFile.runtimePath, "/System/Library/Extensions/") )
+            return true;
+    }
+
+    if ( aFile.runtimePath.find("//") != std::string::npos ) {
+        if (warn) fprintf(stderr, "update_dyld_shared_cache: warning: %s skipping because of bad install name %s\n", archName.c_str(), aFile.runtimePath.c_str());
+        return true;
+    }
+
+    const char* installName = aFile.mh->installName();
+    if ( (pathsWithDuplicateInstallName.count(aFile.runtimePath) != 0) && (aFile.runtimePath != installName) ) {
+        // <rdar://problem/46431467> if a dylib moves and a symlink is installed into its place, bom iterator will see both and issue a warning
+        struct stat statBuf;
+        bool isSymLink = ( (lstat(aFile.runtimePath.c_str(), &statBuf) == 0) && S_ISLNK(statBuf.st_mode) );
+        if (!isSymLink && warn) fprintf(stderr, "update_dyld_shared_cache: warning: %s skipping because of duplicate install name %s\n", archName.c_str(), aFile.runtimePath.c_str());
+        return true;
+    }
+
+    if ( aFile.runtimePath != installName ) {
+        // see if install name is a symlink to actual path
+        std::string fullInstall = volumePrefix + installName;
+        char resolvedPath[PATH_MAX];
+        if ( realpath(fullInstall.c_str(), resolvedPath) != NULL ) {
+            std::string resolvedSymlink = resolvedPath;
+            if ( !volumePrefix.empty() ) {
+                resolvedSymlink = resolvedSymlink.substr(volumePrefix.size());
+            }
+            if ( aFile.runtimePath == resolvedSymlink ) {
+                return false;
+            }
+        }
+        // <rdar://problem/38000411> also if runtime path is a symlink to install name
+        std::string fullRuntime = volumePrefix + aFile.runtimePath;
+        if ( realpath(fullRuntime.c_str(), resolvedPath) != NULL ) {
+            std::string resolvedSymlink = resolvedPath;
+            if ( !volumePrefix.empty() ) {
+                resolvedSymlink = resolvedSymlink.substr(volumePrefix.size());
+            }
+            if ( resolvedSymlink == installName ) {
+                return false;
+            }
+        }
+        if (warn) fprintf(stderr, "update_dyld_shared_cache: warning: %s skipping because of bad install name %s\n", archName.c_str(), aFile.runtimePath.c_str());
+        return true;
+    }
+    return false;
+}
+
+static void pruneCachedDylibs(const std::string& volumePrefix, const std::unordered_set<std::string>& skipDylibs, MappedMachOsByCategory& fileSet)
+{
+    std::unordered_set<std::string> pathsWithDuplicateInstallName;
+
+    std::unordered_map<std::string, std::string> installNameToFirstPath;
+    for (DyldSharedCache::MappedMachO& aFile : fileSet.dylibsForCache) {
+        const char* installName = aFile.mh->installName();
+        auto pos = installNameToFirstPath.find(installName);
+        if ( pos == installNameToFirstPath.end() ) {
+            installNameToFirstPath[installName] = aFile.runtimePath;
+        }
+        else {
+            pathsWithDuplicateInstallName.insert(aFile.runtimePath);
+            pathsWithDuplicateInstallName.insert(installNameToFirstPath[installName]);
+        }
+    }
+
+    for (DyldSharedCache::MappedMachO& aFile : fileSet.dylibsForCache) {
+        if ( dontCache(volumePrefix, fileSet.archName, pathsWithDuplicateInstallName, aFile, true, skipDylibs) ) {
+            // <rdar://problem/46423929> don't build dlopen closures for symlinks to something in the dyld cache
+            if ( pathsWithDuplicateInstallName.count(aFile.runtimePath) == 0 )
+                fileSet.otherDylibsAndBundles.push_back(aFile);
+        }
+    }
+    fileSet.dylibsForCache.erase(std::remove_if(fileSet.dylibsForCache.begin(), fileSet.dylibsForCache.end(),
+        [&](const DyldSharedCache::MappedMachO& aFile) { return dontCache(volumePrefix, fileSet.archName, pathsWithDuplicateInstallName, aFile, false, skipDylibs); }),
+        fileSet.dylibsForCache.end());
+}
+
+static void pruneOtherDylibs(const std::string& volumePrefix, MappedMachOsByCategory& fileSet)
+{
+    // other OS dylibs should not contain dylibs that are embedded in some .app bundle
+    fileSet.otherDylibsAndBundles.erase(std::remove_if(fileSet.otherDylibsAndBundles.begin(), fileSet.otherDylibsAndBundles.end(),
+                                                       [&](const DyldSharedCache::MappedMachO& aFile) { return (aFile.runtimePath.find(".app/") != std::string::npos); }),
+                                        fileSet.otherDylibsAndBundles.end());
+}
+static void pruneExecutables(const std::string& volumePrefix, MappedMachOsByCategory& fileSet)
+{
+    // don't build closures for xcode shims in /usr/bin (e.g. /usr/bin/clang) which re-exec themselves to a tool inside Xcode.app
+    fileSet.mainExecutables.erase(std::remove_if(fileSet.mainExecutables.begin(), fileSet.mainExecutables.end(),
+        [&](const DyldSharedCache::MappedMachO& aFile) {
+            if ( !startsWith(aFile.runtimePath, "/usr/bin/") )
+                return false;
+            __block bool isXcodeShim = false;
+            aFile.mh->forEachDependentDylib(^(const char* loadPath, bool, bool, bool, uint32_t, uint32_t, bool &stop) {
+                if ( strcmp(loadPath, "/usr/lib/libxcselect.dylib") == 0 )
+                    isXcodeShim = true;
+            });
+            return isXcodeShim;
+        }), fileSet.mainExecutables.end());
+}
+
+static bool existingCacheUpToDate(const std::string& existingCache, const std::vector<DyldSharedCache::MappedMachO>& currentDylibs)
+{
+    // if no existing cache, it is not up-to-date
+    int fd = ::open(existingCache.c_str(), O_RDONLY);
+    if ( fd < 0 )
+        return false;
+
+    // build map of found dylibs
+    std::unordered_map<std::string, const DyldSharedCache::MappedMachO*> currentDylibMap;
+    for (const DyldSharedCache::MappedMachO& aFile : currentDylibs) {
+        //fprintf(stderr, "0x%0llX 0x%0llX  %s\n", aFile.inode, aFile.modTime, aFile.runtimePath.c_str());
+        currentDylibMap[aFile.runtimePath] = &aFile;
+    }
+
+    // make sure all dylibs in existing cache have same mtime and inode as found dylib
+    __block bool foundMismatch = false;
+    const uint64_t cacheMapLen = 0x40000000;
+    void *p = ::mmap(NULL, cacheMapLen, PROT_READ, MAP_PRIVATE, fd, 0);
+    if ( p != MAP_FAILED ) {
+        const DyldSharedCache* cache = (DyldSharedCache*)p;
+        cache->forEachImageEntry(^(const char* installName, uint64_t mTime, uint64_t inode) {
+            bool foundMatch = false;
+            auto pos = currentDylibMap.find(installName);
+            if ( pos != currentDylibMap.end() ) {
+                const DyldSharedCache::MappedMachO* foundDylib = pos->second;
+                if ( (foundDylib->inode == inode) && (foundDylib->modTime == mTime) ) {
+                    foundMatch = true;
+                }
+            }
+            if ( !foundMatch ) {
+                // use slow path and look for any dylib with a matching inode and mtime
+                bool foundSlow = false;
+                for (const DyldSharedCache::MappedMachO& aFile : currentDylibs) {
+                    if ( (aFile.inode == inode) && (aFile.modTime == mTime) ) {
+                        foundSlow = true;
+                        break;
+                    }
+                }
+                if ( !foundSlow ) {
+                    foundMismatch = true;
+                    if ( verbose )
+                        fprintf(stderr, "rebuilding dyld cache because dylib changed: %s\n", installName);
+                }
+            }
+         });
+        ::munmap(p, cacheMapLen);
+    }
+
+    ::close(fd);
+
+    return !foundMismatch;
+}
+
+
+inline uint32_t absolutetime_to_milliseconds(uint64_t abstime)
+{
+    return (uint32_t)(abstime/1000/1000);
+}
+
+static bool runningOnHaswell()
+{
+    // check system is capable of running x86_64h code
+    struct host_basic_info  info;
+    mach_msg_type_number_t  count    = HOST_BASIC_INFO_COUNT;
+    mach_port_t             hostPort = mach_host_self();
+    kern_return_t           result   = host_info(hostPort, HOST_BASIC_INFO, (host_info_t)&info, &count);
+    mach_port_deallocate(mach_task_self(), hostPort);
+
+    return ( (result == KERN_SUCCESS) && (info.cpu_subtype == CPU_SUBTYPE_X86_64_H) );
+}
+
+
+
+#define TERMINATE_IF_LAST_ARG( s )      \
+    do {                                \
+        if ( i == argc - 1 ) {          \
+            fprintf(stderr, s );        \
+            return 1;                   \
+        }                               \
+    } while ( 0 )
 
 int main(int argc, const char* argv[], const char* envp[])
 {
-    fprintf(stderr, "This tool is deprecated.\n");
-    return 0;
-}
-
+    std::string                     rootPath;
+    std::string                     overlayPath;
+    std::string                     dylibListFile;
+    bool                            universal = false;
+    bool                            force = false;
+    bool                            searchDisk = false;
+    bool                            dylibsRemoved = false;
+    std::string                     cacheDir;
+    std::unordered_set<std::string> archStrs;
+    std::unordered_set<std::string> skipDylibs;
+
+    // parse command line options
+    for (int i = 1; i < argc; ++i) {
+        const char* arg = argv[i];
+        if (strcmp(arg, "-debug") == 0) {
+            verbose = true;
+        }
+        else if (strcmp(arg, "-verbose") == 0) {
+            verbose = true;
+        }
+        else if (strcmp(arg, "-dont_map_local_symbols") == 0) {
+            //We are going to ignore this
+        }
+        else if (strcmp(arg, "-dylib_list") == 0) {
+            TERMINATE_IF_LAST_ARG("-dylib_list missing argument");
+            dylibListFile = argv[++i];
+        }
+        else if ((strcmp(arg, "-root") == 0) || (strcmp(arg, "--root") == 0)) {
+            TERMINATE_IF_LAST_ARG("-root missing path argument\n");
+            rootPath = argv[++i];
+        }
+        else if (strcmp(arg, "-overlay") == 0) {
+            TERMINATE_IF_LAST_ARG("-overlay missing path argument\n");
+            overlayPath = argv[++i];
+        }
+        else if (strcmp(arg, "-cache_dir") == 0) {
+            TERMINATE_IF_LAST_ARG("-cache_dir missing path argument\n");
+            cacheDir = argv[++i];
+        }
+        else if (strcmp(arg, "-arch") == 0) {
+            TERMINATE_IF_LAST_ARG("-arch missing argument\n");
+            archStrs.insert(argv[++i]);
+        }
+        else if (strcmp(arg, "-search_disk") == 0) {
+            searchDisk = true;
+        }
+        else if (strcmp(arg, "-dylibs_removed_in_mastering") == 0) {
+            dylibsRemoved = true;
+        }
+        else if (strcmp(arg, "-force") == 0) {
+            force = true;
+        }
+        else if (strcmp(arg, "-sort_by_name") == 0) {
+            //No-op, we always do this now
+        }
+        else if (strcmp(arg, "-universal_boot") == 0) {
+            universal = true;
+        }
+        else if (strcmp(arg, "-skip") == 0) {
+            TERMINATE_IF_LAST_ARG("-skip missing argument\n");
+            skipDylibs.insert(argv[++i]);
+        }
+        else {
+            //usage();
+            fprintf(stderr, "update_dyld_shared_cache: unknown option: %s\n", arg);
+            return 1;
+        }
+    }
+
+    if ( !rootPath.empty() & !overlayPath.empty() ) {
+        fprintf(stderr, "-root and -overlay cannot be used together\n");
+        return 1;
+    }
+    // canonicalize rootPath
+    if ( !rootPath.empty() ) {
+        char resolvedPath[PATH_MAX];
+        if ( realpath(rootPath.c_str(), resolvedPath) != NULL ) {
+            rootPath = resolvedPath;
+        }
+        // <rdar://problem/33223984> when building closures for boot volume, pathPrefixes should be empty
+        if ( rootPath == "/" ) {
+            rootPath = "";
+        }
+    }
+    // canonicalize overlayPath
+    if ( !overlayPath.empty() ) {
+        char resolvedPath[PATH_MAX];
+        if ( realpath(overlayPath.c_str(), resolvedPath) != NULL ) {
+            overlayPath = resolvedPath;
+        }
+    }
+
+    // <rdar://problem/36362221> update_dyld_shared_cache should re-exec() itself to a newer version
+    std::string newTool;
+    if ( !rootPath.empty() )
+        newTool = rootPath + "/usr/bin/update_dyld_shared_cache";
+    else if ( !overlayPath.empty() )
+        newTool = overlayPath + "/usr/bin/update_dyld_shared_cache";
+    if ( !newTool.empty() ) {
+        struct stat newToolStatBuf;
+        if ( stat(newTool.c_str(), &newToolStatBuf) == 0 ) {
+            char curToolPath[PATH_MAX];
+            uint32_t curToolPathsize = PATH_MAX;
+            int result = _NSGetExecutablePath(curToolPath, &curToolPathsize);
+            if ( result == 0 ) {
+                char resolvedCurToolPath[PATH_MAX];
+                if ( realpath(curToolPath, resolvedCurToolPath) != NULL ) {
+                    // don't re-exec if we are already running that tool
+                    if ( newTool != resolvedCurToolPath ) {
+                        execve(newTool.c_str(), (char**)argv, (char**)envp);
+                    }
+                }
+            }
+        }
+    }
+
+    // Find the boot volume so that we can ensure all overlays are on the same volume
+    struct stat rootStatBuf;
+    if ( stat(rootPath == "" ? "/" : rootPath.c_str(), &rootStatBuf) != 0 ) {
+        fprintf(stderr, "update_dyld_shared_cache: error: could not stat root file system because '%s'\n", strerror(errno));
+        return 1;
+    }
+
+    dev_t rootFS = rootStatBuf.st_dev;
+
+    //
+    // pathPrefixes for three modes:
+    //   1) no options: { "" }           // search only boot volume
+    //   2) -overlay:   { overlay, "" }  // search overlay, then boot volume
+    //   3) -root:      { root }         // search only -root volume
+    //
+    std::vector<std::string> pathPrefixes;
+    if ( !overlayPath.empty() ) {
+        // Only add the overlay path if it exists, and is the same volume as the root
+        struct stat overlayStatBuf;
+        if ( stat(overlayPath.c_str(), &overlayStatBuf) != 0 ) {
+            fprintf(stderr, "update_dyld_shared_cache: warning: ignoring overlay dir '%s' because '%s'\n", overlayPath.c_str(), strerror(errno));
+            overlayPath.clear();
+        } else if (overlayStatBuf.st_dev != rootFS) {
+            fprintf(stderr, "update_dyld_shared_cache: warning: ignoring overlay dir '%s' because it is not the boot volume\n", overlayPath.c_str());
+            overlayPath.clear();
+        } else {
+            pathPrefixes.push_back(overlayPath);
+        }
+    }
+    pathPrefixes.push_back(rootPath);
+
+    if ( cacheDir.empty() ) {
+        // if -cache_dir is not specified, then write() will eventually fail if we are not running as root
+        if ( geteuid() != 0 ) {
+            fprintf(stderr, "update_dyld_shared_cache: must be run as root (sudo)\n");
+            return 1;
+        }
+
+        // write cache file into -root or -overlay directory, if used
+        if ( rootPath != "/" )
+            cacheDir = rootPath +  MACOSX_DYLD_SHARED_CACHE_DIR;
+        else if ( !overlayPath.empty()  )
+            cacheDir = overlayPath +  MACOSX_DYLD_SHARED_CACHE_DIR;
+        else
+            cacheDir = MACOSX_DYLD_SHARED_CACHE_DIR;
+   }
+
+    int err = mkpath_np(cacheDir.c_str(), S_IRWXU | S_IRGRP|S_IXGRP | S_IROTH|S_IXOTH);
+    if ( (err != 0) && (err != EEXIST) ) {
+        fprintf(stderr, "update_dyld_shared_cache: could not access cache dir: mkpath_np(%s) failed errno=%d\n", cacheDir.c_str(), err);
+        return 1;
+    }
+
+    if ( archStrs.empty() ) {
+        if ( universal ) {
+            // <rdar://problem/26182089> -universal_boot should make all possible dyld caches
+            archStrs.insert("i386");
+            archStrs.insert("x86_64");
+            archStrs.insert("x86_64h");
+        }
+        else {
+            // just make caches for this machine
+            archStrs.insert("i386");
+            archStrs.insert(runningOnHaswell() ? "x86_64h" : "x86_64");
+        }
+    }
+
+    uint64_t t1 = mach_absolute_time();
+
+    // find all mach-o files for requested architectures
+    bool requireDylibsBeRootlessProtected = isProtectedBySIP(cacheDir);
+    __block std::vector<MappedMachOsByCategory> allFileSets;
+    if ( archStrs.count("x86_64") )
+        allFileSets.push_back({"x86_64"});
+    if ( archStrs.count("x86_64h") )
+        allFileSets.push_back({"x86_64h"});
+    if ( archStrs.count("i386") )
+        allFileSets.push_back({"i386"});
+    if ( searchDisk )
+        findAllFiles(pathPrefixes, requireDylibsBeRootlessProtected, rootFS, allFileSets);
+    else {
+        std::unordered_set<std::string> runtimePathsFound;
+        findOSFilesViaBOMS(pathPrefixes, requireDylibsBeRootlessProtected, rootFS, allFileSets);
+    }
+
+    // nothing in OS uses i386 dylibs, so only dylibs used by third party apps need to be in cache
+    for (MappedMachOsByCategory& fileSet : allFileSets) {
+        pruneCachedDylibs(rootPath, skipDylibs, fileSet);
+        pruneOtherDylibs(rootPath, fileSet);
+        pruneExecutables(rootPath, fileSet);
+   }
+
+    uint64_t t2 = mach_absolute_time();
+    if ( verbose ) {
+        if ( searchDisk )
+            fprintf(stderr, "time to scan file system and construct lists of mach-o files: %ums\n", absolutetime_to_milliseconds(t2-t1));
+        else
+            fprintf(stderr, "time to read BOM and construct lists of mach-o files: %ums\n", absolutetime_to_milliseconds(t2-t1));
+    }
+
+    // build caches in parallel on machines with at leat 4GB of RAM
+    uint64_t memSize = 0;
+    size_t sz = sizeof(memSize);;
+    bool buildInParallel = false;
+    if ( sysctlbyname("hw.memsize", &memSize, &sz, NULL, 0) == 0 ) {
+        if ( memSize >= 0x100000000ULL )
+            buildInParallel = true;
+    }
+    dispatch_queue_t dqueue = buildInParallel ? dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0)
+                                              : dispatch_queue_create("serial-queue", DISPATCH_QUEUE_SERIAL);
+
+    // build all caches
+    __block bool cacheBuildFailure = false;
+    __block bool wroteSomeCacheFile = false;
+    dispatch_apply(allFileSets.size(), dqueue, ^(size_t index) {
+        MappedMachOsByCategory& fileSet = allFileSets[index];
+        const std::string outFile = cacheDir + "/dyld_shared_cache_" + fileSet.archName;
+
+        DyldSharedCache::MappedMachO (^loader)(const std::string&) = ^DyldSharedCache::MappedMachO(const std::string& runtimePath) {
+            if ( skipDylibs.count(runtimePath) )
+                return DyldSharedCache::MappedMachO();
+            for (const std::string& prefix : pathPrefixes) {
+                std::string fullPath = prefix + runtimePath;
+                struct stat statBuf;
+                if ( stat(fullPath.c_str(), &statBuf) == 0 ) {
+                    dyld3::closure::FileSystemPhysical fileSystem(prefix.c_str());
+                    char resolvedPath[PATH_MAX];
+                    if ( realpath(fullPath.c_str(), resolvedPath) != NULL ) {
+                        std::string resolvedSymlink = resolvedPath;
+                        if ( !rootPath.empty() ) {
+                            resolvedSymlink = resolvedSymlink.substr(rootPath.size());
+                        }
+                        if ( (runtimePath != resolvedSymlink) && !contains(runtimePath, "InputContext") ) {  //HACK remove InputContext when fixed
+                           // path requested is a symlink path, check if real path already loaded
+                            for (const DyldSharedCache::MappedMachO& aDylibMapping : fileSet.dylibsForCache) {
+                                if ( aDylibMapping.runtimePath == resolvedSymlink ) {
+                                    if ( verbose )
+                                        fprintf(stderr, "verifySelfContained, redirect %s to %s\n", runtimePath.c_str(), aDylibMapping.runtimePath.c_str());
+                                    return aDylibMapping;
+                                }
+                            }
+                        }
+                    }
+
+                    std::vector<MappedMachOsByCategory> mappedFiles;
+                    mappedFiles.push_back({fileSet.archName});
+                   if ( addIfMachO(fileSystem, runtimePath, statBuf, requireDylibsBeRootlessProtected, rootFS, mappedFiles) ) {
+                        if ( !mappedFiles.back().dylibsForCache.empty() ) {
+                            if ( verbose )
+                                fprintf(stderr, "verifySelfContained, add %s\n", mappedFiles.back().dylibsForCache.back().runtimePath.c_str());
+                            return mappedFiles.back().dylibsForCache.back();
+                        }
+                    }
+                }
+            }
+            return DyldSharedCache::MappedMachO();
+        };
+        size_t startCount = fileSet.dylibsForCache.size();
+        std::vector<std::pair<DyldSharedCache::MappedMachO, std::set<std::string>>> excludes;
+        DyldSharedCache::verifySelfContained(fileSet.dylibsForCache, loader, excludes);
+        for (size_t i=startCount; i < fileSet.dylibsForCache.size(); ++i) {
+            fprintf(stderr, "update_dyld_shared_cache: warning: %s not in .bom, but adding required dylib %s\n", fileSet.archName.c_str(), fileSet.dylibsForCache[i].runtimePath.c_str());
+        }
+        for (auto& exclude : excludes) {
+            std::string reasons = "(\"";
+            for (auto i = exclude.second.begin(); i != exclude.second.end(); ++i) {
+                reasons += *i;
+                if (i != --exclude.second.end()) {
+                    reasons += "\", \"";
+                }
+            }
+            reasons += "\")";
+            fprintf(stderr, "update_dyld_shared_cache: warning: %s rejected from cached dylibs: %s (%s)\n", fileSet.archName.c_str(), exclude.first.runtimePath.c_str(), reasons.c_str());
+            fileSet.otherDylibsAndBundles.push_back(exclude.first);
+        }
+
+        // check if cache is already up to date
+        if ( !force ) {
+            if ( existingCacheUpToDate(outFile, fileSet.dylibsForCache) )
+                return;
+        }
+
+         // add any extra dylibs needed which were not in .bom
+        fprintf(stderr, "update_dyld_shared_cache: %s incorporating %lu OS dylibs, tracking %lu others, building closures for %lu executables\n",
+                        fileSet.archName.c_str(), fileSet.dylibsForCache.size(), fileSet.otherDylibsAndBundles.size(), fileSet.mainExecutables.size());
+        //for (const DyldSharedCache::MappedMachO& aFile : fileSet.otherDylibsAndBundles) {
+        //    fprintf(stderr, "  %s\n", aFile.runtimePath.c_str());
+        //}
+
+
+        // build cache new cache file
+        DyldSharedCache::CreateOptions options;
+        options.outputFilePath               = outFile;
+        options.outputMapFilePath            = cacheDir + "/dyld_shared_cache_" + fileSet.archName + ".map";
+        options.archName                     = fileSet.archName;
+        options.platform                     = dyld3::Platform::macOS;
+        options.excludeLocalSymbols          = false;
+        options.optimizeStubs                = false;
+        options.optimizeObjC                 = true;
+        options.codeSigningDigestMode        = DyldSharedCache::SHA256only;
+        options.dylibsRemovedDuringMastering = dylibsRemoved;
+        options.inodesAreSameAsRuntime       = true;
+        options.cacheSupportsASLR            = (fileSet.archName != "i386");
+        options.forSimulator                 = false;
+        options.isLocallyBuiltCache          = true;
+        options.verbose                      = verbose;
+        options.evictLeafDylibsOnOverflow    = true;
+        options.pathPrefixes                 = pathPrefixes;
+        DyldSharedCache::CreateResults results = DyldSharedCache::create(options, fileSet.dylibsForCache, fileSet.otherDylibsAndBundles, fileSet.mainExecutables);
+
+        // print any warnings
+        for (const std::string& warn : results.warnings) {
+            fprintf(stderr, "update_dyld_shared_cache: warning: %s %s\n", fileSet.archName.c_str(), warn.c_str());
+        }
+        if ( results.errorMessage.empty() ) {
+            wroteSomeCacheFile = true;
+        }
+        else {
+            fprintf(stderr, "update_dyld_shared_cache: %s\n", results.errorMessage.c_str());
+            cacheBuildFailure = true;
+        }
+    });
+
+
+    // Save off spintrace data
+    if ( wroteSomeCacheFile ) {
+        void* h = dlopen("/usr/lib/libdscsym.dylib", 0);
+        if ( h != nullptr ) {
+            typedef int (*dscym_func)(const char*);
+            dscym_func func = (dscym_func)dlsym(h, "dscsym_save_dscsyms_for_current_caches");
+            std::string nuggetRoot = rootPath;
+            if ( nuggetRoot.empty() )
+                 nuggetRoot = overlayPath;
+            if ( nuggetRoot.empty() )
+                 nuggetRoot = "/";
+            (*func)(nuggetRoot.c_str());
+        }
+    }
+
+
+    // we could unmap all input files, but tool is about to quit
+
+    return (cacheBuildFailure ? 1 : 0);
+}
+