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cache-builder/update_dyld_sim_shared_cache.cpp /dev/null dyld-941.5
--- /dev/null
+++ dyld/dyld-941.5/cache-builder/update_dyld_sim_shared_cache.cpp
@@ -0,0 +1,695 @@
+/* -*- mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*-
+ *
+ * Copyright (c) 2018 Apple Inc. All rights reserved.
+ *
+ * @APPLE_LICENSE_HEADER_START@
+ *
+ * This file contains Original Code and/or Modifications of Original Code
+ * as defined in and that are subject to the Apple Public Source License
+ * Version 2.0 (the 'License'). You may not use this file except in
+ * compliance with the License. Please obtain a copy of the License at
+ * http://www.opensource.apple.com/apsl/ and read it before using this
+ * file.
+ *
+ * The Original Code and all software distributed under the License are
+ * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
+ * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
+ * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
+ * Please see the License for the specific language governing rights and
+ * limitations under the License.
+ *
+ * @APPLE_LICENSE_HEADER_END@
+ */
+
+#include <sys/types.h>
+#include <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>
+#include <stdlib.h>
+#include <math.h>
+#include <fcntl.h>
+#include <dlfcn.h>
+#include <signal.h>
+#include <errno.h>
+#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 <CoreFoundation/CoreFoundation.h>
+
+#include <algorithm>
+#include <vector>
+#include <unordered_set>
+#include <unordered_set>
+#include <iostream>
+#include <fstream>
+#include <sstream>
+
+#include "FileUtils.h"
+#include "StringUtils.h"
+#include "DyldSharedCache.h"
+#include "MachOFile.h"
+#include "MachOAnalyzer.h"
+#include "ClosureFileSystemPhysical.h"
+
+struct MappedMachOsByCategory
+{
+    const dyld3::GradedArchs&                   archs;
+    std::vector<DyldSharedCache::MappedMachO>   dylibsForCache;
+    std::vector<DyldSharedCache::MappedMachO>   otherDylibsAndBundles;
+    std::vector<DyldSharedCache::MappedMachO>   mainExecutables;
+};
+
+static const char* sAllowedPrefixes[] = {
+    "/usr",
+    "/System",
+// don't look at main executables until simulator supports dyld3
+//    "/bin",
+//    "/sbin",
+};
+
+static const char* sDontUsePrefixes[] = {
+    "/usr/share",
+    "/usr/local",
+};
+
+static const char* sMacOSHostLibs[] = {
+    "/usr/lib/system/libsystem_kernel.dylib",
+    "/usr/lib/system/libsystem_platform.dylib",
+    "/usr/lib/system/libsystem_pthread.dylib",
+};
+
+static const char* sMacOSBinaries[] = {
+    "/sbin/launchd_sim_trampoline",
+    "/usr/sbin/iokitsimd",
+    "/usr/lib/system/host/liblaunch_sim.dylib",
+};
+
+static bool verbose = false;
+
+
+static bool addIfMachO(const dyld3::closure::FileSystem& fileSystem, const std::string& runtimePath, const struct stat& statBuf, std::vector<MappedMachOsByCategory>& files, dyld3::Platform platform, Diagnostics& diag)
+{
+    // don't precompute closure info for any debug or profile dylibs
+    if ( endsWith(runtimePath, "_profile.dylib") || endsWith(runtimePath, "_debug.dylib") || endsWith(runtimePath, "_asan.dylib") || endsWith(runtimePath, "_profile") || endsWith(runtimePath, "_debug") )
+        return false;
+    if ( startsWith(runtimePath, "/usr/lib/system/introspection/") )
+        return false;
+
+    bool result = false;
+    for (MappedMachOsByCategory& file : files) {
+        char realerPath[MAXPATHLEN];
+        dyld3::closure::LoadedFileInfo loadedFileInfo = dyld3::MachOAnalyzer::load(diag, fileSystem, runtimePath.c_str(), file.archs, platform, realerPath);
+        const dyld3::MachOAnalyzer* ma = (const dyld3::MachOAnalyzer*)loadedFileInfo.fileContent;
+
+        if ( ma != nullptr ) {
+            bool            sipProtected    = false;
+            bool            issetuid        = false;
+            const uint64_t  sliceLen        = loadedFileInfo.sliceLen;
+            if ( ma->isDynamicExecutable() ) {
+        #if 0 // dyld3 not enabled for simulator yet, so don't collect main executables
+                issetuid = (statBuf.st_mode & (S_ISUID|S_ISGID));
+                file.mainExecutables.emplace_back(runtimePath, ma, sliceLen, issetuid, sipProtected, loadedFileInfo.sliceOffset, statBuf.st_mtime, statBuf.st_ino);
+                result = true;
+        #endif
+            }
+            else if ( ma->canBePlacedInDyldCache(runtimePath.c_str(), ^(const char* msg) {
+                diag.error("Dylib located at '%s' cannot be placed in cache because: '%s'", loadedFileInfo.path, msg);
+            }) ) {
+                file.dylibsForCache.emplace_back(runtimePath, ma, sliceLen, issetuid, sipProtected, loadedFileInfo.sliceOffset, statBuf.st_mtime, statBuf.st_ino);
+                result = true;
+           }
+        }
+    }
+    
+    return result;
+}
+
+static void findAllFiles(const dyld3::closure::FileSystem& fileSystem, const std::vector<std::string>& pathPrefixes, std::vector<MappedMachOsByCategory>& files, dyld3::Platform platform)
+{
+    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
+        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 (must have at least a page of TEXT and LINKEDIT)
+                if ( statBuf.st_size < 0x2000 )
+                    return;
+
+                // don't add paths already found using previous prefix
+                if ( multiplePrefixes && (alreadyUsed.count(path) != 0) )
+                    return;
+                
+                // don't add binaries built for the host Mac OS platform
+                for (std::string s : sMacOSBinaries) {
+                    if (s.compare(path) == 0)
+                        return;
+                }
+                // if the file is mach-o, add to list
+                Diagnostics diag;
+                if ( addIfMachO(fileSystem, path, statBuf, files, platform, diag) ) {
+                    if ( multiplePrefixes )
+                        alreadyUsed.insert(path);
+                }
+            });
+        }
+    }
+}
+
+static void addMacOSHostLibs(std::vector<MappedMachOsByCategory>& allFileSets, dyld3::Platform platform)
+{
+    dyld3::closure::FileSystemPhysical fileSystem;
+    for (const char* path : sMacOSHostLibs) {
+        struct stat statBuf;
+        if ( stat(path, &statBuf) == 0 ) {
+            Diagnostics diag;
+            addIfMachO(fileSystem, path, statBuf, allFileSets, dyld3::Platform::macOS, diag);
+            if ( diag.hasError() )
+                fprintf(stderr, "update_dyld_sim_shared_cache: warning: skipping %s because %s\n", path, diag.errorMessage().c_str());
+        }
+    }
+}
+
+static void addMacOSBinaries(const dyld3::closure::FileSystem& fileSystem, const std::vector<std::string>& pathPrefixes, std::vector<MappedMachOsByCategory>& files)
+{
+    for (const std::string& prefix : pathPrefixes) {
+        for (std::string path : sMacOSBinaries) {
+            std::string fullPath = prefix + path;
+            struct stat statBuf;
+            if ( stat(fullPath.c_str(), &statBuf) == 0 ) {
+                Diagnostics diag;
+                addIfMachO(fileSystem, path, statBuf, files, dyld3::Platform::macOS, diag);
+                if ( diag.hasError() )
+                    fprintf(stderr, "update_dyld_sim_shared_cache: warning: skipping %s because %s\n", fullPath.c_str(), diag.errorMessage().c_str());
+            }
+        }
+    }
+}
+
+static bool dontCache(const std::string& simRuntimeRootPath, 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, "/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 ( aFile.runtimePath.find("//") != std::string::npos ) {
+        if (warn) fprintf(stderr, "update_dyld_sim_shared_cache: warning: %s use 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_sim_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 = simRuntimeRootPath + installName;
+        char resolvedPath[PATH_MAX];
+        if ( realpath(fullInstall.c_str(), resolvedPath) != NULL ) {
+            std::string resolvedSymlink = resolvedPath;
+            if ( !simRuntimeRootPath.empty() ) {
+                resolvedSymlink = resolvedSymlink.substr(simRuntimeRootPath.size());
+            }
+            if ( aFile.runtimePath == resolvedSymlink ) {
+                return false;
+            }
+        }
+        // <rdar://problem/38000411> also if runtime path is a symlink to install name
+        std::string fullRuntime = simRuntimeRootPath + aFile.runtimePath;
+        if ( realpath(fullRuntime.c_str(), resolvedPath) != NULL ) {
+            std::string resolvedSymlink = resolvedPath;
+            if ( !simRuntimeRootPath.empty() ) {
+                resolvedSymlink = resolvedSymlink.substr(simRuntimeRootPath.size());
+            }
+            if ( resolvedSymlink == installName ) {
+                return false;
+            }
+        }
+        if (warn) fprintf(stderr, "update_dyld_sim_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.archs.name(), 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.archs.name(), 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 std::string getOrderFileContent(const std::string& orderFile)
+{
+    std::ifstream fstream(orderFile);
+    std::stringstream stringBuf;
+    stringBuf << fstream.rdbuf();
+    return stringBuf.str();
+}
+
+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;
+    struct stat statbuf;
+    if ( ::fstat(fd, &statbuf) == -1 ) {
+        ::close(fd);
+        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 = statbuf.st_size;
+    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;
+}
+
+static void addFileSets(const std::unordered_set<std::string>& allowedArchs, std::unordered_set<std::string>& requestedArchs, std::vector<MappedMachOsByCategory>& fileSets)
+{
+    if ( requestedArchs.empty() ) {
+#if __arm64__
+        requestedArchs.insert("arm64");
+#elif __x86_64__
+        requestedArchs.insert("x86_64");
+#else
+    #error unknown platform
+#endif
+    }
+
+    for (auto& requested : requestedArchs) {
+        if ( allowedArchs.find(requested) != allowedArchs.end() ) {
+            const dyld3::GradedArchs& archs = dyld3::GradedArchs::forName(requested.c_str(), false);
+            fileSets.push_back({archs});
+        }
+    }
+}
+
+inline uint32_t absolutetime_to_milliseconds(uint64_t abstime)
+{
+    return (uint32_t)(abstime/1000/1000);
+}
+
+
+#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[])
+{
+    std::string                     rootPath;
+    bool                            force = false;
+    bool                            dylibsRemoved = false;
+    std::string                     cacheDir;
+    std::string                     dylibOrderFile;
+    std::string                     dirtyDataOrderFile;
+    dyld3::Platform                 platform = dyld3::Platform::iOS_simulator;
+    std::unordered_set<std::string> skipDylibs;
+    std::unordered_set<std::string> requestedArchs;
+    
+    // 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, "-root") == 0) || (strcmp(arg, "--root") == 0)) {
+            TERMINATE_IF_LAST_ARG("-root missing path argument\n");
+            rootPath = 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, "-iOS") == 0) {
+            platform = dyld3::Platform::iOS_simulator;
+        }
+        else if (strcmp(arg, "-watchOS") == 0) {
+            platform = dyld3::Platform::watchOS_simulator;
+        }
+        else if (strcmp(arg, "-tvOS") == 0) {
+            platform = dyld3::Platform::tvOS_simulator;
+        }
+        else if (strcmp(arg, "-dylibs_removed_in_mastering") == 0) {
+            dylibsRemoved = true;
+        }
+        else if (strcmp(arg, "-dylib_order_file") == 0) {
+            TERMINATE_IF_LAST_ARG("-dylib_order_file missing path argument\n");
+            dylibOrderFile = argv[++i];
+        }
+        else if (strcmp(arg, "-dirty_data_order_file") == 0) {
+            TERMINATE_IF_LAST_ARG("-dirty_data_order_file missing path argument\n");
+            dirtyDataOrderFile = argv[++i];
+        }
+        else if (strcmp(arg, "-arch") == 0) {
+            TERMINATE_IF_LAST_ARG("-arch missing arch argument\n");
+            requestedArchs.insert(argv[++i]);
+        }
+        else if (strcmp(arg, "-force") == 0) {
+            force = 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_sim_shared_cache: unknown option: %s\n", arg);
+            return 1;
+        }
+    }
+    
+    if ( rootPath.empty() ) {
+        fprintf(stderr, "-root should be specified\n");
+        return 1;
+    }
+    if ( cacheDir.empty() ) {
+        fprintf(stderr, "-cache_dir should be specified\n");
+        return 1;
+    }
+    // canonicalize rootPath
+    char resolvedPath[PATH_MAX];
+    if ( realpath(rootPath.c_str(), resolvedPath) != NULL ) {
+        rootPath = resolvedPath;
+    }
+    
+    // canonicalize cacheDir.
+    // Later, path is checked against real path name before writing cache file to avoid TOCTU race condition.
+    if ( realpath(cacheDir.c_str(), resolvedPath) != NULL ) {
+        cacheDir = resolvedPath;
+    }
+
+    // Find the boot volume so that we can ensure all overlays are on the same volume
+    struct stat rootStatBuf;
+    if ( stat(rootPath.c_str(), &rootStatBuf) != 0 ) {
+        fprintf(stderr, "update_dyld_sim_shared_cache: error: could not stat root file system because '%s'\n", strerror(errno));
+        return 1;
+    }
+
+    std::vector<std::string> pathPrefixes;
+
+    pathPrefixes.push_back(rootPath);
+    
+    // build FileSystem object
+    const char* fsRoot = rootPath.empty() ? nullptr : rootPath.c_str();
+    dyld3::closure::FileSystemPhysical fileSystem(fsRoot, nullptr);
+
+    
+    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_sim_shared_cache: could not access cache dir: mkpath_np(%s) failed errno=%d\n", cacheDir.c_str(), err);
+        return 1;
+    }
+
+    std::string dylibOrderFileContent;
+    if ( !dylibOrderFile.empty() ) {
+        dylibOrderFileContent = getOrderFileContent(dylibOrderFile);
+    }
+
+    std::string dirtyDataOrderFileContent;
+    if ( !dirtyDataOrderFile.empty() ) {
+        dirtyDataOrderFileContent = getOrderFileContent(dirtyDataOrderFile);
+    }
+    uint64_t t1 = mach_absolute_time();
+
+    __block std::vector<MappedMachOsByCategory> allFileSets;
+    std::unordered_set<std::string> allowedArchs;
+    switch ( platform ) {
+        case dyld3::Platform::iOS_simulator:
+            allowedArchs.insert("x86_64");
+            allowedArchs.insert("arm64");
+            break;
+        case dyld3::Platform::watchOS_simulator:
+            allowedArchs.insert("x86_64");
+            allowedArchs.insert("arm64");
+
+            break;
+        case dyld3::Platform::tvOS_simulator:
+            allowedArchs.insert("x86_64");
+            allowedArchs.insert("arm64");
+            break;
+        default:
+            assert(0 && "invalid platform");
+            break;
+    }
+
+    addFileSets(allowedArchs, requestedArchs, allFileSets);
+    if ( allFileSets.empty() ) {
+        fprintf(stderr, "update_dyld_sim_shared_cache: error: no valid architecture specified\n");
+        return 1;
+    }
+
+    findAllFiles(fileSystem, pathPrefixes, allFileSets, platform);
+    addMacOSHostLibs(allFileSets, platform);
+    addMacOSBinaries(fileSystem, pathPrefixes, 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);
+    }
+
+    uint64_t t2 = mach_absolute_time();
+    if ( verbose ) {
+        fprintf(stderr, "time to scan file system 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_sim_shared_cache_" + fileSet.archs.name();
+        
+        DyldSharedCache::MappedMachO (^loader)(const std::string&, Diagnostics&) = ^DyldSharedCache::MappedMachO(const std::string& runtimePath, Diagnostics& diag) {
+            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 ) {
+                    char truePath[PATH_MAX];
+                    if ( realpath(fullPath.c_str(), truePath) != NULL ) {
+                        std::string resolvedSymlink = truePath;
+                        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.archs});
+                    if ( addIfMachO(fileSystem, runtimePath, statBuf, mappedFiles, platform, diag) ) {
+                        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;
+        std::unordered_set<std::string> badZippered;
+        DyldSharedCache::verifySelfContained(fileSet.dylibsForCache, badZippered, loader, excludes);
+        for (size_t i=startCount; i < fileSet.dylibsForCache.size(); ++i) {
+            fprintf(stderr, "update_dyld_sim_shared_cache: warning: %s not in initial scan, but adding required dylib %s\n", fileSet.archs.name(), 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_sim_shared_cache: warning: %s rejected from cached dylibs: %s (%s)\n", fileSet.archs.name(), 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;
+        }
+        
+        
+        // build cache new cache file
+        DyldSharedCache::CreateOptions options;
+        options.outputFilePath               = outFile;
+        options.outputMapFilePath            = cacheDir + "/dyld_sim_shared_cache_" + fileSet.archs.name() + ".map";
+        options.archs                        = &fileSet.archs;
+        options.platform                     = platform;
+        options.localSymbolMode              = DyldSharedCache::LocalSymbolsMode::keep;
+        options.optimizeStubs                = false;
+        options.optimizeDyldDlopens          = false;   // don't add dyld3 closures to simulator cache
+        options.optimizeDyldLaunches         = false;   // don't add dyld3 closures to simulator cache
+        options.codeSigningDigestMode        = DyldSharedCache::SHA256only;
+        options.dylibsRemovedDuringMastering = dylibsRemoved;
+        options.inodesAreSameAsRuntime       = true;
+        options.cacheSupportsASLR            = false;
+        options.forSimulator                 = true;
+        options.isLocallyBuiltCache          = true;
+        options.verbose                      = verbose;
+        options.evictLeafDylibsOnOverflow    = true;
+        options.dylibOrdering                = parseOrderFile(dylibOrderFileContent);
+        options.dirtyDataSegmentOrdering     = parseOrderFile(dirtyDataOrderFileContent);
+        DyldSharedCache::CreateResults results = DyldSharedCache::create(options, fileSystem, fileSet.dylibsForCache, fileSet.otherDylibsAndBundles, fileSet.mainExecutables);
+        
+        // print any warnings
+        for (const std::string& warn : results.warnings) {
+            fprintf(stderr, "update_dyld_sim_shared_cache: warning: %s %s\n", fileSet.archs.name(), warn.c_str());
+        }
+        if ( results.errorMessage.empty() ) {
+            wroteSomeCacheFile = true;
+        }
+        else {
+            fprintf(stderr, "update_dyld_sim_shared_cache: %s\n", results.errorMessage.c_str());
+            cacheBuildFailure = true;
+        }
+    });
+    
+    // we could unmap all input files, but tool is about to quit
+
+    return (cacheBuildFailure ? 1 : 0);
+}
+