]> git.saurik.com Git - apple/dyld.git/blobdiff - launch-cache/update_dyld_shared_cache.cpp
dyld-239.4.tar.gz
[apple/dyld.git] / launch-cache / update_dyld_shared_cache.cpp
index f4373307a31db06f30e5328938d80044737137ae..73cb11474a2a83cc4fcda9e68d7ecfbb0daa8bbf 100644 (file)
@@ -1,6 +1,6 @@
 /* -*- mode: C++; c-basic-offset: 4; tab-width: 4 -*- 
  *
- * Copyright (c) 2006-2007 Apple Inc. All rights reserved.
+ * Copyright (c) 2006-2011 Apple Inc. All rights reserved.
  *
  * @APPLE_LICENSE_HEADER_START@
  * 
 #include <sys/stat.h>
 #include <sys/mman.h>
 #include <mach/mach.h>
+#include <mach/mach_time.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 <sys/uio.h>
 #include <servers/bootstrap.h>
 #include <mach-o/loader.h>
 #include <mach-o/fat.h>
+#include <CoreFoundation/CoreFoundation.h>
+#include <Security/Security.h>
+#include <Security/SecCodeSigner.h>
+#include <CommonCrypto/CommonDigest.h>
 
 #include "dyld_cache_format.h"
 
 #include <vector>
 #include <set>
 #include <map>
-#include <ext/hash_map>
+#include <unordered_map>
 
 #include "Architectures.hpp"
 #include "MachOLayout.hpp"
 #include "MachORebaser.hpp"
 #include "MachOBinder.hpp"
 #include "CacheFileAbstraction.hpp"
+#include "dyld_cache_config.h"
 
-extern "C" { 
-       #include "dyld_shared_cache_server.h"
-}
+#define SELOPT_WRITE
+#include "objc-shared-cache.h"
+
+#define FIRST_DYLIB_TEXT_OFFSET 0x8000
 
+#ifndef LC_FUNCTION_STARTS
+    #define LC_FUNCTION_STARTS 0x26
+#endif
 
 static bool                                                    verbose = false;
+static bool                                                    progress = false;
+static bool                                                    iPhoneOS = false;
 static std::vector<const char*>                warnings;
 
 
-static uint64_t pageAlign(uint64_t addr) { return ( (addr + 4095) & (-4096) ); }
+static void warn(const char *arch, const char *format, ...)
+{
+    char *msg;
+
+    va_list args;
+    va_start(args, format);
+    ::vasprintf(&msg, format, args);
+    va_end(args);
+    
+    warnings.push_back(msg);
+    
+    if ( verbose ) {
+        ::fprintf(::stderr, "update_dyld_shared_cache: warning: %s%s%s%s\n", 
+                  arch ? "for arch " : "", 
+                  arch ? arch : "", 
+                  arch ? ", " : "", 
+                  msg);
+    }
+}
+
+
+class CStringHash {
+public:
+       size_t operator()(const char* __s) const {
+               size_t __h = 0;
+               for ( ; *__s; ++__s)
+                       __h = 5 * __h + *__s;
+               return __h;
+       };
+};
+class CStringEquals
+{
+public:
+       bool operator()(const char* left, const char* right) const { return (strcmp(left, right) == 0); }
+};
+
+
 
 class ArchGraph
 {
 public:
-       static void                     addArch(cpu_type_t arch);
-       static void                     addRoot(const char* vpath, const std::set<cpu_type_t>& archs);
-       static void                     findSharedDylibs(cpu_type_t arch);
-       static ArchGraph*       getArch(cpu_type_t arch) { return fgPerArchGraph[arch]; }
+       typedef std::unordered_map<const char*, const char*, CStringHash, CStringEquals> StringToString;
+
+       static void                     addArchPair(ArchPair ap);
+       static void                     addRoot(const char* vpath, const std::set<ArchPair>& archs);
+       static void                     findSharedDylibs(ArchPair ap);
+       static ArchGraph*       graphForArchPair(ArchPair ap) { return fgPerArchGraph[ap]; }
        static void                     setFileSystemRoot(const char* root) { fgFileSystemRoot = root; }
-       static const char*      archName(cpu_type_t arch);
+       static void                     setFileSystemOverlay(const char* overlay) { fgFileSystemOverlay = overlay; }
+       static const char*      archName(ArchPair ap);
        
-       cpu_type_t                                                                                      getArch() { return fArch; }
+       ArchPair                                                                                        getArchPair() { return fArchPair; }
        std::set<const class MachOLayoutAbstraction*>&          getSharedDylibs() { return fSharedDylibs; }
+       StringToString&                                                                         getDylibAliases() { return fAliasesMap; }
+       const char*                                                                                     archName() { return archName(fArchPair); }
        
 private:
        
@@ -103,68 +158,82 @@ private:
                std::set<DependencyNode*>                                       fRootsDependentOnThis;
        };
 
-       struct CStringEquals {
-               bool operator()(const char* left, const char* right) const { return (strcmp(left, right) == 0); }
-       };
-       typedef __gnu_cxx::hash_map<const char*, class DependencyNode*, __gnu_cxx::hash<const char*>, CStringEquals> PathToNode;
+       typedef std::unordered_map<const char*, class DependencyNode*, CStringHash, CStringEquals> PathToNode;
 
 
-                                                               ArchGraph(cpu_type_t arch) : fArch(arch) {}
-       static void                                     addRootForArch(const char* path, const MachOLayoutAbstraction*);
+                                                               ArchGraph(ArchPair ap) : fArchPair(ap) {}
        void                                            addRoot(const char* path, const MachOLayoutAbstraction*);
        DependencyNode*                         getNode(const char* path);
        DependencyNode*                         getNodeForVirtualPath(const char* vpath);
-       static bool                                     canBeShared(const MachOLayoutAbstraction* layout, cpu_type_t arch, const std::set<const MachOLayoutAbstraction*>& possibleLibs, std::map<const MachOLayoutAbstraction*, bool>& shareableMap);
+       static bool                                     canBeShared(const MachOLayoutAbstraction* layout, ArchPair ap, const std::set<const MachOLayoutAbstraction*>& possibleLibs, std::map<const MachOLayoutAbstraction*, bool>& shareableMap);
+       static bool                                     sharable(const MachOLayoutAbstraction* layout, ArchPair ap, char** msg);
 
-       static std::map<cpu_type_t, ArchGraph*> fgPerArchGraph;
+       static std::map<ArchPair, ArchGraph*>   fgPerArchGraph;
        static const char*                                              fgFileSystemRoot;
+       static const char*                                              fgFileSystemOverlay;
        
-       cpu_type_t                                                                      fArch;
+       ArchPair                                                                        fArchPair;
        std::set<DependencyNode*>                                       fRoots;
        PathToNode                                                                      fNodes;
        std::set<const MachOLayoutAbstraction*>         fSharedDylibs;  // use set to avoid duplicates when installname!=realpath
+       StringToString                                                          fAliasesMap;
 };
-std::map<cpu_type_t, ArchGraph*>       ArchGraph::fgPerArchGraph;
+std::map<ArchPair, ArchGraph*>         ArchGraph::fgPerArchGraph;
 const char*                                                    ArchGraph::fgFileSystemRoot = "";
+const char*                                                    ArchGraph::fgFileSystemOverlay = "";
 
-void ArchGraph::addArch(cpu_type_t arch)
+void ArchGraph::addArchPair(ArchPair ap)
 {
-       //fprintf(stderr, "adding arch 0x%08X\n", arch);
-       fgPerArchGraph[arch] = new ArchGraph(arch);
+       //fprintf(stderr, "adding ArchPair 0x%08X,0x%08X\n", ap.arch, ap.subtype);
+       fgPerArchGraph[ap] = new ArchGraph(ap);
 }
 
-void ArchGraph::addRoot(const char* vpath, const std::set<cpu_type_t>& archs)
+void ArchGraph::addRoot(const char* vpath, const std::set<ArchPair>& onlyArchs)
 {
-       char completePath[strlen(fgFileSystemRoot)+strlen(vpath)+2];
-       const char* path;
-       if ( strlen(fgFileSystemRoot) == 0 ) {
-               path = vpath;
+       //fprintf(stderr, "addRoot(%s)\n", vpath);
+       char completePath[MAXPATHLEN];
+       const char* path = NULL;
+       // check -overlay path first
+       if ( fgFileSystemOverlay[0] != '\0' ) {
+               strcpy(completePath, fgFileSystemOverlay);
+               strcat(completePath, vpath);    // assumes vpath starts with '/'
+               struct stat stat_buf;
+               if ( stat(completePath, &stat_buf) == 0 )
+                       path = completePath;
        }
-       else {
+       // if not found in overlay, check for -root
+       if ( (path == NULL) && (fgFileSystemRoot[0] != '\0') ) {
                strcpy(completePath, fgFileSystemRoot);
                strcat(completePath, vpath);    // assumes vpath starts with '/'
-               path = completePath;
+               struct stat stat_buf;
+               if ( stat(completePath, &stat_buf) == 0 )
+                       path = completePath;
        }
+       if ( path == NULL ) 
+               path = vpath;
+       
        try {
-               const UniversalMachOLayout* uni = UniversalMachOLayout::find(path, &archs);
-               const std::vector<MachOLayoutAbstraction*>& layouts = uni->getArchs();
-               for(std::vector<MachOLayoutAbstraction*>::const_iterator it = layouts.begin(); it != layouts.end(); ++it) {
-                       const MachOLayoutAbstraction* layout = *it;
-                       if ( archs.count(layout->getArchitecture()) > 0 )
-                               ArchGraph::addRootForArch(path, layout);
+               //fprintf(stderr, "    UniversalMachOLayout::find(%s)\n", path);
+               const UniversalMachOLayout& uni = UniversalMachOLayout::find(path, &onlyArchs);
+               for(std::set<ArchPair>::iterator ait = onlyArchs.begin(); ait != onlyArchs.end(); ++ait) {
+                       try {
+                               const MachOLayoutAbstraction* layout = uni.getSlice(*ait);
+                               if ( layout != NULL )
+                                       fgPerArchGraph[*ait]->addRoot(path, layout);
+                       }
+                       catch (const char* msg) {
+                               if ( verbose ) 
+                                       fprintf(stderr, "update_dyld_shared_cache: warning for %s can't use root '%s': %s\n", fgPerArchGraph[*ait]->archName(), path, msg);
+                       }
+                       
                }
-               // don't delete uni, it is owned by UniversalMachOLayout cache
        }
        catch (const char* msg) {
-               fprintf(stderr, "update_dyld_shared_cache: warning can't use root %s: %s\n", path, msg);
+               fprintf(stderr, "update_dyld_shared_cache: warning can't use root '%s': %s\n", path, msg);
        }
 }
 
-void ArchGraph::addRootForArch(const char* path, const MachOLayoutAbstraction* layout)
-{
-       ArchGraph* graph = fgPerArchGraph[layout->getArchitecture()];
-       graph->addRoot(path, layout);
-}
+
 
 void ArchGraph::addRoot(const char* path, const MachOLayoutAbstraction* layout)
 {
@@ -184,19 +253,56 @@ void ArchGraph::addRoot(const char* path, const MachOLayoutAbstraction* layout)
 // a virtual path does not have the fgFileSystemRoot prefix
 ArchGraph::DependencyNode* ArchGraph::getNodeForVirtualPath(const char* vpath)
 {
-       if ( fgFileSystemRoot == NULL ) {
-               return this->getNode(vpath);
+       //fprintf(stderr, "getNodeForVirtualPath(%s)\n", vpath);
+       char completePath[MAXPATHLEN];
+       if ( fgFileSystemOverlay[0] != '\0' ) {
+               // using -overlay means if /overlay/path/dylib exists use it, otherwise use /path/dylib
+               strcpy(completePath, fgFileSystemOverlay);
+               strcat(completePath, vpath);    // assumes vpath starts with '/'
+               struct stat stat_buf;
+               if ( stat(completePath, &stat_buf) == 0 )
+                       return this->getNode(completePath);
+               else {
+                       // <rdar://problem/9279770> support when install name is a symlink
+                       const char* pathToSymlink = vpath;
+                       if ( fgFileSystemRoot[0] != '\0' ) {
+                               strcpy(completePath, fgFileSystemRoot);
+                               strcat(completePath, vpath);
+                               pathToSymlink = completePath;
+                       }
+                       if ( (lstat(pathToSymlink, &stat_buf) == 0) && S_ISLNK(stat_buf.st_mode) ) {
+                               // requested path did not exist in /overlay, but leaf of path is a symlink in /
+                               char pathInSymLink[MAXPATHLEN];
+                               size_t res = readlink(pathToSymlink, pathInSymLink, sizeof(pathInSymLink));
+                               if ( res != -1 ) {
+                                       pathInSymLink[res] = '\0';
+                                       if ( pathInSymLink[0] != '/' ) {
+                                               char symFullPath[MAXPATHLEN];
+                                               strcpy(symFullPath, vpath);
+                                               char* lastSlash = strrchr(symFullPath, '/');
+                                               if ( lastSlash != NULL ) {
+                                                       strcpy(lastSlash+1, pathInSymLink);
+                                                       // (re)try looking for what symlink points to, but in /overlay
+                                                       return this->getNodeForVirtualPath(symFullPath);
+                                               }
+                                       } 
+                               }
+                       }
+               }
        }
-       else {
-               char completePath[strlen(fgFileSystemRoot)+strlen(vpath)+2];
+       if ( fgFileSystemRoot[0] != '\0' ) {
+               // using -root means always use /rootpath/usr/lib
                strcpy(completePath, fgFileSystemRoot);
                strcat(completePath, vpath);    // assumes vpath starts with '/'
                return this->getNode(completePath);
        }
+       // not found in -overlay or -root not used
+       return this->getNode(vpath);
 }
 
 ArchGraph::DependencyNode* ArchGraph::getNode(const char* path)
 {
+       //fprintf(stderr, "getNode(%s)\n", path);
        // look up supplied path to see if node already exists
        PathToNode::iterator pos = fNodes.find(path);
        if ( pos != fNodes.end() )
@@ -209,21 +315,71 @@ ArchGraph::DependencyNode* ArchGraph::getNode(const char* path)
        
        // look up real path to see if node already exists
        pos = fNodes.find(realPath);
-       if ( pos != fNodes.end() )
+       if ( pos != fNodes.end() ) {
+               // update fAliasesMap with symlinks found
+               const char* aliasPath = path;
+               if ( (fgFileSystemRoot != NULL) && (strncmp(path, fgFileSystemRoot, strlen(fgFileSystemRoot)) == 0) ) {
+                       aliasPath = &path[strlen(fgFileSystemRoot)];
+               }
+               if ( fAliasesMap.find(aliasPath) == fAliasesMap.end() ) {
+                       if ( strcmp(aliasPath, pos->second->getLayout()->getID().name) != 0 ) {
+                               fAliasesMap[strdup(aliasPath)] = pos->second->getLayout()->getID().name;
+                               //fprintf(stderr, "getNode() %s: added alias %s -> %s\n", archName(fArchPair), aliasPath, fAliasesMap[aliasPath]);
+                       }
+               }
                return pos->second;
+       }
        
        // still does not exist, so create a new node
-       const UniversalMachOLayout* uni = UniversalMachOLayout::find(realPath);
-       DependencyNode* node = new DependencyNode(this, realPath, uni->getArch(fArch));
+       const UniversalMachOLayout& uni = UniversalMachOLayout::find(realPath);
+       DependencyNode* node = new DependencyNode(this, realPath, uni.getSlice(fArchPair));
        if ( node->getLayout() == NULL ) {
-               throwf("%s is missing arch %s", realPath, archName(fArch));
+               throwf("%s is missing arch %s", realPath, archName(fArchPair));
        }
        // add realpath to node map
        fNodes[node->getPath()] = node;
        // if install name is not real path, add install name to node map
        if ( (node->getLayout()->getFileType() == MH_DYLIB) && (strcmp(realPath, node->getLayout()->getID().name) != 0) ) {
-               //fprintf(stderr, "adding node alias 0x%08X %s for %s\n", fArch, node->getLayout()->getID().name, realPath);
-               fNodes[node->getLayout()->getID().name] = node;
+               //fprintf(stderr, "adding %s node alias %s for %s\n", archName(fArchPair), node->getLayout()->getID().name, realPath);
+               pos = fNodes.find(node->getLayout()->getID().name);
+               if ( pos != fNodes.end() ) {
+                       // get uuids of two dylibs to see if this is accidental copy of a dylib or two differnent dylibs with same -install_name
+                       uuid_t uuid1;
+                       uuid_t uuid2;
+                       node->getLayout()->uuid(uuid1);
+                       pos->second->getLayout()->uuid(uuid2);
+                       if ( memcmp(&uuid1, &uuid2, 16) == 0 ) {
+                               // <rdar://problem/8305479> warn if two dylib in cache have same install_name
+                               char* msg;
+                               asprintf(&msg, "update_dyld_shared_cache: warning, found two copies of the same dylib with same install path: %s\n\t%s\n\t%s\n", 
+                                                                               node->getLayout()->getID().name, pos->second->getPath(), node->getPath());
+                               fprintf(stderr, "%s", msg);
+                               warnings.push_back(msg);
+                       }
+                       else {
+                               // <rdar://problem/12763450> update_dyld_shared_cache should fail if two images have same install name
+                               fprintf(stderr, "update_dyld_shared_cache: found two different dylibs with same install path: %s\n\t%s\n\t%s\n", 
+                                                       node->getLayout()->getID().name, pos->second->getPath(), node->getPath());
+                               exit(1);
+                       }
+               }
+               else
+                       fNodes[node->getLayout()->getID().name] = node;
+               // update fAliasesMap with symlinks found
+               const char* aliasPath = realPath;
+               if ( (fgFileSystemRoot != NULL) && (fgFileSystemRoot[0] != '\0') && (strncmp(realPath, fgFileSystemRoot, strlen(fgFileSystemRoot)) == 0) ) {
+                       aliasPath = &realPath[strlen(fgFileSystemRoot)];
+               }
+               // <rdar://problem/11192810> Too many aliases in -overlay mode
+               if ( (fgFileSystemOverlay != NULL) && (fgFileSystemOverlay[0] != '\0') && (strncmp(realPath, fgFileSystemOverlay, strlen(fgFileSystemOverlay)) == 0) ) {
+                       aliasPath = &realPath[strlen(fgFileSystemOverlay)];
+               }
+               if ( fAliasesMap.find(aliasPath) == fAliasesMap.end() ) {
+                       if ( strcmp(aliasPath, node->getLayout()->getID().name) != 0 ) {
+                               fAliasesMap[strdup(aliasPath)] = node->getLayout()->getID().name;
+                               //fprintf(stderr, "getNode() %s: added alias %s -> %s\n", archName(fArchPair), aliasPath, fAliasesMap[aliasPath]);
+                       }
+               }
        }
        return node;
 }
@@ -244,7 +400,13 @@ void ArchGraph::DependencyNode::loadDependencies(const MachOLayoutAbstraction* m
                                        // expand @executable_path path prefix
                                        const char* executablePath = mainExecutableLayout->getFilePath();
                                        char newPath[strlen(executablePath) + strlen(dependentPath)+2];
-                                       strcpy(newPath, executablePath);
+                                       if ( (fgFileSystemRoot != NULL) && (strncmp(executablePath, fgFileSystemRoot, strlen(fgFileSystemRoot)) == 0) ) {
+                                               // executablePath already has rootPath prefix, need to remove that to get to base virtual path
+                                               strcpy(newPath, &executablePath[strlen(fgFileSystemRoot)]);
+                                       }
+                                       else {
+                                               strcpy(newPath, executablePath);
+                                       }
                                        char* addPoint = strrchr(newPath,'/');
                                        if ( addPoint != NULL )
                                                strcpy(&addPoint[1], &dependentPath[17]);
@@ -255,7 +417,13 @@ void ArchGraph::DependencyNode::loadDependencies(const MachOLayoutAbstraction* m
                                else if ( strncmp(dependentPath, "@loader_path/", 13) == 0 ) {
                                        // expand @loader_path path prefix
                                        char newPath[strlen(fPath) + strlen(dependentPath)+2];
-                                       strcpy(newPath, fPath);
+                                       if ( (fgFileSystemRoot != NULL) && (strncmp(fPath, fgFileSystemRoot, strlen(fgFileSystemRoot)) == 0) ) {
+                                               // fPath already has rootPath prefix, need to remove that to get to base virtual path
+                                               strcpy(newPath, &fPath[strlen(fgFileSystemRoot)]);
+                                       }
+                                       else {
+                                               strcpy(newPath, fPath);
+                                       }
                                        char* addPoint = strrchr(newPath,'/');
                                        if ( addPoint != NULL )
                                                strcpy(&addPoint[1], &dependentPath[13]);
@@ -266,11 +434,25 @@ void ArchGraph::DependencyNode::loadDependencies(const MachOLayoutAbstraction* m
                                else if ( strncmp(dependentPath, "@rpath/", 7) == 0 ) {
                                        throw "@rpath not supported in dyld shared cache";
                                }
-                               fDependsOn.insert(fGraph->getNodeForVirtualPath(dependentPath));
+                               // <rdar://problem/9161945> silently ignore dependents from main executables that can't be in shared cache
+                               bool addDependent = true;
+                               if ( fLayout->getFileType() == MH_EXECUTE ) {
+                                       if ( (strncmp(dependentPath, "/usr/lib/", 9) != 0) && (strncmp(dependentPath, "/System/Library/", 16) != 0) ) {
+                                               addDependent = false;
+                                       }
+                               }
+                               if ( addDependent )
+                                       fDependsOn.insert(fGraph->getNodeForVirtualPath(dependentPath));
                        }
                        catch (const char* msg) {
-                               fprintf(stderr, "warning, could not bind %s because %s\n", fPath, msg);
-                               fDependentMissing = true;
+                               if ( it->weakImport || ! fLayout->hasSplitSegInfo() ) {
+                                       // ok to ignore missing weak imported dylibs from things that are
+                                       // not going to be in the dyld shared cache
+                               }
+                               else {
+                                       fprintf(stderr, "warning, could not bind %s because %s\n", fPath, msg);
+                                       fDependentMissing = true;
+                               }
                        }
                }
                // recurse
@@ -297,46 +479,98 @@ ArchGraph::DependencyNode::DependencyNode(ArchGraph* graph, const char* path, co
        //fprintf(stderr, "new DependencyNode(0x%08X, %s)\n", graph->fArch, path);
 }
 
-void ArchGraph::findSharedDylibs(cpu_type_t arch)
+void ArchGraph::findSharedDylibs(ArchPair ap)
 {
-       const PathToNode& nodes = fgPerArchGraph[arch]->fNodes;
+       const PathToNode& nodes = fgPerArchGraph[ap]->fNodes;
        std::set<const MachOLayoutAbstraction*> possibleLibs;
-       //fprintf(stderr, "shared for arch 0x%08X\n", arch);
+       //fprintf(stderr, "shared for arch %s\n", archName(ap));
        for(PathToNode::const_iterator it = nodes.begin(); it != nodes.end(); ++it) {
                DependencyNode* node = it->second;
-               if ( node->allDependentsFound() && (node->useCount() > 1) ) {
-                       if ( node->getLayout()->hasSplitSegInfo() ) 
-                               possibleLibs.insert(node->getLayout());
-                       //fprintf(stderr, "\t%s\n", it->first);
+               // <rdar://problem/6127437> put all dylibs in shared cache - not just ones used by more than one app
+               if ( node->allDependentsFound() /*&& (node->useCount() > 1)*/ ) {
+                       const MachOLayoutAbstraction* layout = node->getLayout();
+                       if ( layout->isDylib() ) {
+                               char* msg;
+                               if ( sharable(layout, ap, &msg) ) {
+                                       possibleLibs.insert(layout);
+                               }
+                               else {
+                                       if ( layout->getID().name[0] == '@' ) {
+                                               // <rdar://problem/7770139> update_dyld_shared_cache should suppress warnings for embedded frameworks
+                                       }
+                                       else {
+                                               warnings.push_back(msg);
+                                               fprintf(stderr, "update_dyld_shared_cache: for arch %s, %s\n", archName(ap), msg);
+                                       }
+                               }
+                       }
                }
        }
        
        // prune so that all shareable libs depend only on other shareable libs
-       std::set<const MachOLayoutAbstraction*>& sharedLibs = fgPerArchGraph[arch]->fSharedDylibs;
+       std::set<const MachOLayoutAbstraction*>& sharedLibs = fgPerArchGraph[ap]->fSharedDylibs;
        std::map<const MachOLayoutAbstraction*,bool> shareableMap;
        for (std::set<const MachOLayoutAbstraction*>::iterator lit = possibleLibs.begin(); lit != possibleLibs.end(); ++lit) {
-               if ( canBeShared(*lit, arch, possibleLibs, shareableMap) )
+               if ( canBeShared(*lit, ap, possibleLibs, shareableMap) )
                        sharedLibs.insert(*lit);
        }
 }
 
-const char*    ArchGraph::archName(cpu_type_t arch)
+const char*    ArchGraph::archName(ArchPair ap)
 {
-       switch ( arch ) {
-               case CPU_TYPE_POWERPC:
-                       return "ppc";
-               case CPU_TYPE_POWERPC64:
-                       return "ppc64";
+       switch ( ap.arch ) {
                case CPU_TYPE_I386:
                        return "i386";
                case CPU_TYPE_X86_64:
                        return "x86_64";
+               case CPU_TYPE_ARM:
+                       switch ( ap.subtype ) {
+                               case CPU_SUBTYPE_ARM_V4T:
+                                       return "armv4t";
+                               case CPU_SUBTYPE_ARM_V6:
+                                       return "armv6";
+                               case CPU_SUBTYPE_ARM_V5TEJ:
+                                       return "armv5";
+                               case CPU_SUBTYPE_ARM_XSCALE:
+                                       return "arm-xscale";
+                               case CPU_SUBTYPE_ARM_V7:
+                                       return "armv7";
+                               case CPU_SUBTYPE_ARM_V7F:
+                                       return "armv7f";
+                               case CPU_SUBTYPE_ARM_V7K:
+                                       return "armv7k";
+                               case CPU_SUBTYPE_ARM_V7S:
+                                       return "armv7s";
+                               default:
+                                       return "arm";
+                       }
                default:
                        return "unknown";
        }
 }
 
-bool ArchGraph::canBeShared(const MachOLayoutAbstraction* layout, cpu_type_t arch, const std::set<const MachOLayoutAbstraction*>& possibleLibs, std::map<const MachOLayoutAbstraction*, bool>& shareableMap)
+bool ArchGraph::sharable(const MachOLayoutAbstraction* layout, ArchPair ap, char** msg)
+{
+       if ( ! layout->isTwoLevelNamespace() ) 
+               asprintf(msg, "can't put %s in shared cache because it was built -flat_namespace", layout->getID().name);
+       else if ( ! layout->hasSplitSegInfo() ) 
+               asprintf(msg, "can't put %s in shared cache because it was not built for %s or later", layout->getID().name, (iPhoneOS ? "iPhoneOS 3.1" : "MacOSX 10.5"));
+       else if ( ! layout->isRootOwned() )
+               asprintf(msg, "can't put %s in shared cache because it is not owned by root", layout->getID().name);
+       else if ( ! layout->inSharableLocation() )
+               asprintf(msg, "can't put %s in shared cache because it is not in /usr/lib or /System/Library", layout->getID().name);
+       else if ( layout->hasDynamicLookupLinkage() )
+               asprintf(msg, "can't put %s in shared cache because it was built with '-undefined dynamic_lookup'", layout->getID().name);
+       else if ( layout->hasMainExecutableLookupLinkage() )
+               asprintf(msg, "can't put %s in shared cache because it was built with '-bundle_loader'", layout->getID().name);
+       //else if ( ! layout->hasDyldInfo() )
+       //      asprintf(msg, "can't put %s in shared cache because it was built for older OS", layout->getID().name);
+       else
+               return true;
+       return false;
+}
+
+bool ArchGraph::canBeShared(const MachOLayoutAbstraction* layout, ArchPair ap, const std::set<const MachOLayoutAbstraction*>& possibleLibs, std::map<const MachOLayoutAbstraction*, bool>& shareableMap)
 {
        // check map which is a cache of results
        std::map<const MachOLayoutAbstraction*, bool>::iterator mapPos = shareableMap.find(layout);
@@ -347,38 +581,45 @@ bool ArchGraph::canBeShared(const MachOLayoutAbstraction* layout, cpu_type_t arc
        if ( possibleLibs.count(layout) == 0 ) {
                shareableMap[layout] = false;
                char* msg;
-               if ( ! layout->hasSplitSegInfo() )
-                       asprintf(&msg, "can't put %s in shared cache because it was not built for 10.5", layout->getID().name);
-               else
-                       asprintf(&msg, "can't put %s in shared cache", layout->getID().name);
+               if ( sharable(layout, ap, &msg) )
+                       asprintf(&msg, "can't put %s in shared cache, unknown reason", layout->getID().name);
                warnings.push_back(msg);
                if ( verbose )
-                       fprintf(stderr, "update_dyld_shared_cache: for arch %s, %s\n", archName(arch), msg);
+                       fprintf(stderr, "update_dyld_shared_cache: for arch %s, %s\n", archName(ap), msg);
                return false;
        }
        // look recursively
        shareableMap[layout] = true; // mark this shareable early in case of circular references
-       const PathToNode& nodes = fgPerArchGraph[arch]->fNodes;
+       const PathToNode& nodes = fgPerArchGraph[ap]->fNodes;
        const std::vector<MachOLayoutAbstraction::Library>&     dependents = layout->getLibraries();
        for (std::vector<MachOLayoutAbstraction::Library>::const_iterator dit = dependents.begin(); dit != dependents.end(); ++dit) {
                PathToNode::const_iterator pos = nodes.find(dit->name);
                if ( pos == nodes.end() ) {
+                       // path from load command does not match any loaded dylibs, maybe there is a temp symlink
+                       char realPath[MAXPATHLEN];
+                       if ( realpath(dit->name, realPath) != NULL ) {
+                               if ( nodes.find(realPath) != nodes.end() )
+                                       continue;
+                       }
+                       // handle weak imported dylibs not found
+                       if ( dit->weakImport )
+                               continue;
                        shareableMap[layout] = false;
                        char* msg;
                        asprintf(&msg, "can't put %s in shared cache because it depends on %s which can't be found", layout->getID().name, dit->name);
                        warnings.push_back(msg);
                        if ( verbose )
-                               fprintf(stderr, "update_dyld_shared_cache: for arch %s, %s\n", archName(arch), msg);
+                               fprintf(stderr, "update_dyld_shared_cache: for arch %s, %s\n", archName(ap), msg);
                        return false;
                }
                else {
-                       if ( ! canBeShared(pos->second->getLayout(), arch, possibleLibs, shareableMap) ) {
+                       if ( ! canBeShared(pos->second->getLayout(), ap, possibleLibs, shareableMap) ) {
                                shareableMap[layout] = false;
                                char* msg;
                                asprintf(&msg, "can't put %s in shared cache because it depends on %s which can't be in shared cache", layout->getID().name, dit->name);
                                warnings.push_back(msg);
                                if ( verbose )
-                                       fprintf(stderr, "update_dyld_shared_cache: for arch %s, %s\n", archName(arch), msg);
+                                       fprintf(stderr, "update_dyld_shared_cache: for arch %s, %s\n", archName(ap), msg);
                                return false;
                        }
                }
@@ -387,36 +628,127 @@ bool ArchGraph::canBeShared(const MachOLayoutAbstraction* layout, cpu_type_t arc
 }
 
 
+
+class StringPool
+{
+public:
+                               StringPool();
+       const char*     getBuffer();
+       uint32_t        size();
+       uint32_t        add(const char* str);
+       uint32_t        addUnique(const char* str);
+       const char* stringAtIndex(uint32_t) const;
+private:
+       typedef std::unordered_map<const char*, uint32_t, CStringHash, CStringEquals> StringToOffset;
+
+       char*                   fBuffer;
+       uint32_t                fBufferAllocated;
+       uint32_t                fBufferUsed;
+       StringToOffset  fUniqueStrings;
+};
+
+
+StringPool::StringPool() 
+       : fBufferUsed(0), fBufferAllocated(48*1024*1024)
+{
+       fBuffer = (char*)malloc(fBufferAllocated);
+}
+
+uint32_t StringPool::add(const char* str)
+{
+       uint32_t len = strlen(str);
+       if ( (fBufferUsed + len + 1) > fBufferAllocated ) {
+               // grow buffer
+               throw "string buffer exhausted";
+       }
+       strcpy(&fBuffer[fBufferUsed], str);
+       uint32_t result = fBufferUsed;
+       fUniqueStrings[&fBuffer[fBufferUsed]] = result;
+       fBufferUsed += len+1;
+       return result;
+}
+
+uint32_t StringPool::addUnique(const char* str)
+{
+       StringToOffset::iterator pos = fUniqueStrings.find(str);
+       if ( pos != fUniqueStrings.end() ) 
+               return pos->second;
+       else {
+               //fprintf(stderr, "StringPool::addUnique() new string: %s\n", str);
+               return this->add(str);
+       }
+}
+
+uint32_t StringPool::size()
+{
+       return fBufferUsed;
+}
+
+const char*    StringPool::getBuffer()
+{
+       return fBuffer;
+}
+
+const char* StringPool::stringAtIndex(uint32_t index) const
+{
+       return &fBuffer[index];
+}
+
+
+
+struct LocalSymbolInfo
+{
+       uint32_t        dylibOffset;
+       uint32_t        nlistStartIndex;
+       uint32_t        nlistCount;
+};
+
+
 template <typename A>
 class SharedCache
 {
 public:
-                                                       SharedCache(ArchGraph* graph, bool alphaSort, uint64_t dyldBaseAddress);
-       bool                                    update(const char* rootPath, const char* cacheDir, bool force, bool optimize, bool deleteExistingFirst, int archIndex, int archCount);
-       static const char*              filename(bool optimized);
+                                                       SharedCache(ArchGraph* graph, const char* rootPath, const char* overlayPath, const char* cacheDir, bool explicitCacheDir,
+                                                                                       bool alphaSort, bool verify, bool optimize, uint64_t dyldBaseAddress);
+       bool                                    update(bool force, bool optimize, bool deleteExistingFirst, int archIndex, 
+                                                                               int archCount, bool keepSignatures, bool dontMapLocalSymbols);
+       static const char*              cacheFileSuffix(bool optimized, const char* archName);
+
+    // vm address = address AS WRITTEN into the cache
+    // mapped address = address AS MAPPED into the update process only
+    // file offset = offset relative to start of cache file
+    void *                                     mappedAddressForVMAddress(uint64_t vmaddr);
+    uint64_t                           VMAddressForMappedAddress(const void *mapaddr);
+       uint64_t                                cacheFileOffsetForVMAddress(uint64_t addr) const;
+       uint64_t                                VMAddressForCacheFileOffset(uint64_t addr) const;
+
+       static const char*              archName();
 
 private:
-       typedef typename A::P::E        E;
+       typedef typename A::P                   P;
+    typedef typename A::P::E           E;
+    typedef typename A::P::uint_t      pint_t;
 
-       bool                                    notUpToDate(const char* cachePath);
-       bool                                    notUpToDate(const void* cache);
-       uint8_t*                                optimizeLINKEDIT();
+       bool                                    notUpToDate(const char* path, unsigned int aliasCount);
+       bool                                    notUpToDate(const void* cache, unsigned int aliasCount);
+       uint8_t*                                optimizeLINKEDIT(bool keepSignatures, bool dontMapLocalSymbols);
+       void                                    optimizeObjC(std::vector<void*>& pointersInData);
 
        static void                             getSharedCacheBasAddresses(cpu_type_t arch, uint64_t* baseReadOnly, uint64_t* baseWritable);
        static cpu_type_t               arch();
-       static const char*              archName();
-       static uint64_t                 sharedRegionReadOnlyStartAddress();
-       static uint64_t                 sharedRegionWritableStartAddress();
-       static uint64_t                 sharedRegionReadOnlySize();
-       static uint64_t                 sharedRegionWritableSize();
+       static uint64_t                 sharedRegionStartAddress();
+       static uint64_t                 sharedRegionSize();
+       static uint64_t                 sharedRegionStartWritableAddress(uint64_t);
+       static uint64_t                 sharedRegionStartReadOnlyAddress(uint64_t, uint64_t);
        static uint64_t                 getWritableSegmentNewAddress(uint64_t proposedNewAddress, uint64_t originalAddress, uint64_t executableSlide);
+       static bool                             addCacheSlideInfo();
        
-       
-       void                                    assignNewBaseAddresses();
-       uint64_t                                cacheFileOffsetForAddress(uint64_t addr);
+       static uint64_t                 pageAlign(uint64_t addr);
+       void                                    assignNewBaseAddresses(bool verify);
 
        struct LayoutInfo {
                const MachOLayoutAbstraction*           layout;
+               std::vector<const char*>                        aliases;
                dyld_cache_image_info                           info;
        };
        
@@ -424,78 +756,231 @@ private:
                bool operator()(const LayoutInfo& left, const LayoutInfo& right) 
                                { return (strcmp(left.layout->getID().name, right.layout->getID().name) < 0); }
        };
-
-       struct RandomSorter {
-               RandomSorter(const std::vector<LayoutInfo>& infos) {
-                       for(typename std::vector<struct LayoutInfo>::const_iterator it = infos.begin(); it != infos.end(); ++it) 
-                               fMap[it->layout] = arc4random();
+       
+       struct ByAddressSorter {
+               bool operator()(const LayoutInfo& left, const LayoutInfo& right) { 
+                       return (left.layout->getSegments()[0].newAddress() < right.layout->getSegments()[0].newAddress()); 
                }
+       };
+
+    struct ByCStringSectionSizeSorter {
+        bool operator()(const LayoutInfo& left, const LayoutInfo& right) {
+            const std::vector<MachOLayoutAbstraction::Segment>& segs_l =
+                left.layout->getSegments();
+            const std::vector<MachOLayoutAbstraction::Segment>& segs_r = 
+                right.layout->getSegments();
+            if (segs_l.size() == 0  ||  segs_r.size() == 0) {
+                // one image has no segments
+                return segs_l.size() > segs_r.size();
+            }
+            const macho_header<P> *mh_l = (macho_header<P>*)segs_l[0].mappedAddress();
+            const macho_header<P> *mh_r = (macho_header<P>*)segs_r[0].mappedAddress();
+            const macho_section<P> *cstring_l = mh_l->getSection("__TEXT", "__cstring");
+            const macho_section<P> *cstring_r = mh_r->getSection("__TEXT", "__cstring");
+            if (!cstring_l  ||  !cstring_r) {
+                // one image has no cstrings
+                return cstring_l && !cstring_r;
+            }
+
+            return cstring_l->size() > cstring_r->size();
+        }
+    };
+
+       struct Sorter {
+               Sorter(std::map<const MachOLayoutAbstraction*, uint32_t>& map): fMap(map) {}
                bool operator()(const LayoutInfo& left, const LayoutInfo& right) {
                        return (fMap[left.layout] < fMap[right.layout]); 
                }
        private:
-               std::map<const MachOLayoutAbstraction*, uint32_t> fMap;
+               std::map<const MachOLayoutAbstraction*, uint32_t>& fMap;
        };
        
-
+       
        ArchGraph*                                                      fArchGraph;
+       const bool                                                      fVerify;
+       bool                                                            fExistingIsNotUpToDate;
+       bool                                                            fCacheFileInFinalLocation;
+       const char*                                                     fCacheFilePath;
+       uint8_t*                                                        fExistingCacheForVerification;
        std::vector<LayoutInfo>                         fDylibs;
+       std::vector<LayoutInfo>                         fDylibAliases;
        std::vector<shared_file_mapping_np>     fMappings;
+       std::vector<macho_nlist<P> >            fUnmappedLocalSymbols;
+       StringPool                                                      fUnmappedLocalsStringPool;
+       std::vector<LocalSymbolInfo>            fLocalSymbolInfos;
        uint32_t                                                        fHeaderSize;
+    uint8_t*                                                   fInMemoryCache;
        uint64_t                                                        fDyldBaseAddress;
        uint64_t                                                        fLinkEditsTotalUnoptimizedSize;
        uint64_t                                                        fLinkEditsStartAddress;
        MachOLayoutAbstraction::Segment*        fFirstLinkEditSegment;
+       uint32_t                                                        fOffsetOfBindInfoInCombinedLinkedit;
+       uint32_t                                                        fOffsetOfWeakBindInfoInCombinedLinkedit;
+       uint32_t                                                        fOffsetOfLazyBindInfoInCombinedLinkedit;
+       uint32_t                                                        fOffsetOfExportInfoInCombinedLinkedit;
+       uint32_t                                                        fOffsetOfOldSymbolTableInfoInCombinedLinkedit;
+       uint32_t                                                        fSizeOfOldSymbolTableInfoInCombinedLinkedit;
+       uint32_t                                                        fOffsetOfOldExternalRelocationsInCombinedLinkedit;
+       uint32_t                                                        fSizeOfOldExternalRelocationsInCombinedLinkedit;
+       uint32_t                                                        fOffsetOfOldIndirectSymbolsInCombinedLinkedit;
+       uint32_t                                                        fSizeOfOldIndirectSymbolsInCombinedLinkedit;
+       uint32_t                                                        fOffsetOfOldStringPoolInCombinedLinkedit;
+       uint32_t                                                        fSizeOfOldStringPoolInCombinedLinkedit;
+       uint32_t                                                        fOffsetOfFunctionStartsInCombinedLinkedit;
+       uint32_t                                                        fSizeOfFunctionStartsInCombinedLinkedit;
+       uint32_t                                                        fOffsetOfDataInCodeInCombinedLinkedit;
+       uint32_t                                                        fSizeOfDataInCodeInCombinedLinkedit;
+       uint32_t                                                        fLinkEditsTotalOptimizedSize;
+       uint32_t                                                        fUnmappedLocalSymbolsSize;
+};
+
+
+// Access a section containing a list of pointers
+template <typename A, typename T>
+class PointerSection 
+{
+    typedef typename A::P P;
+    typedef typename A::P::uint_t pint_t;
+
+    SharedCache<A>* const                      fCache;
+    const macho_section<P>* const      fSection;
+    pint_t * const                                     fBase;
+    uint64_t                                           fCount;
+
+public:
+    PointerSection(SharedCache<A>* cache, const macho_header<P>* header, 
+                   const char *segname, const char *sectname)
+        : fCache(cache)
+        , fSection(header->getSection(segname, sectname))
+        , fBase(fSection ? (pint_t *)cache->mappedAddressForVMAddress(fSection->addr()) : 0)
+        , fCount(fSection ? fSection->size() / sizeof(pint_t) : 0)
+    {
+    }
+
+    uint64_t count() const { return fCount; }
+
+    uint64_t getUnmapped(uint64_t index) const {
+        if (index >= fCount) throwf("index out of range");
+        return P::getP(fBase[index]);
+    }
+
+    T get(uint64_t index) const { 
+        return (T)fCache->mappedAddressForVMAddress(getUnmapped(index));
+    }
+
+    void set(uint64_t index, uint64_t value) {
+        if (index >= fCount) throwf("index out of range");
+        P::setP(fBase[index], value);
+    }
+       
+    void removeNulls() {
+        uint64_t shift = 0;
+        for (uint64_t i = 0; i < fCount; i++) {
+            pint_t value = fBase[i];
+            if (value) {
+                fBase[i-shift] = value;
+            } else {
+                shift++;
+            }
+        }
+        fCount -= shift;
+               const_cast<macho_section<P>*>(fSection)->set_size(fCount * sizeof(pint_t));
+    }
+};
+
+// Access a section containing an array of structures
+template <typename A, typename T>
+class ArraySection 
+{
+    typedef typename A::P P;
+
+    SharedCache<A>* const fCache;
+    const macho_section<P>* const fSection;
+    T * const fBase;
+    uint64_t const fCount;
+
+public:
+    ArraySection(SharedCache<A>* cache, const macho_header<P>* header, 
+                 const char *segname, const char *sectname)
+        : fCache(cache)
+        , fSection(header->getSection(segname, sectname))
+        , fBase(fSection ? (T *)cache->mappedAddressForVMAddress(fSection->addr()) : 0)
+        , fCount(fSection ? fSection->size() / sizeof(T) : 0)
+    {
+    }
+
+    uint64_t count() const { return fCount; }
+
+    T& get(uint64_t index) const { 
+        if (index >= fCount) throwf("index out of range");
+        return fBase[index];
+    }
 };
 
 
+// GrP fixme
+#include "ObjCLegacyAbstraction.hpp"
+#include "ObjCModernAbstraction.hpp"
+
 
        
-template <>     cpu_type_t     SharedCache<ppc>::arch()        { return CPU_TYPE_POWERPC; }
-template <>     cpu_type_t     SharedCache<ppc64>::arch()      { return CPU_TYPE_POWERPC64; }
 template <>     cpu_type_t     SharedCache<x86>::arch()        { return CPU_TYPE_I386; }
 template <>     cpu_type_t     SharedCache<x86_64>::arch()     { return CPU_TYPE_X86_64; }
+template <>     cpu_type_t     SharedCache<arm>::arch()        { return CPU_TYPE_ARM; }
 
-template <>     uint64_t       SharedCache<ppc>::sharedRegionReadOnlyStartAddress()    { return 0x90000000; }
-template <>     uint64_t       SharedCache<ppc64>::sharedRegionReadOnlyStartAddress()  { return 0x7FFF80000000LL; }
-template <>     uint64_t       SharedCache<x86>::sharedRegionReadOnlyStartAddress()    { return 0x90000000; }
-template <>     uint64_t       SharedCache<x86_64>::sharedRegionReadOnlyStartAddress() { return 0x7FFF80000000LL; }
+template <>     uint64_t       SharedCache<x86>::sharedRegionStartAddress()                    { return 0x90000000; }
+template <>     uint64_t       SharedCache<x86_64>::sharedRegionStartAddress()                 { return 0x7FFF80000000LL; }
+template <>     uint64_t       SharedCache<arm>::sharedRegionStartAddress()                    { return ARM_SHARED_REGION_START; }
 
-template <>     uint64_t       SharedCache<ppc>::sharedRegionWritableStartAddress()    { return 0xA0000000; }
-template <>     uint64_t       SharedCache<ppc64>::sharedRegionWritableStartAddress()  { return 0x7FFF70000000LL; }
-template <>     uint64_t       SharedCache<x86>::sharedRegionWritableStartAddress()    { return 0xA0000000; }
-template <>     uint64_t       SharedCache<x86_64>::sharedRegionWritableStartAddress() { return 0x7FFF70000000LL; }
+template <>     uint64_t       SharedCache<x86>::sharedRegionSize()                                    { return 0x20000000; }
+template <>     uint64_t       SharedCache<x86_64>::sharedRegionSize()                                 { return 0x40000000; }
+template <>     uint64_t       SharedCache<arm>::sharedRegionSize()                                    { return ARM_SHARED_REGION_SIZE; }
 
-template <>     uint64_t       SharedCache<ppc>::sharedRegionReadOnlySize()                    { return 0x10000000; }
-template <>     uint64_t       SharedCache<ppc64>::sharedRegionReadOnlySize()                  { return 0x7FE00000; }
-template <>     uint64_t       SharedCache<x86>::sharedRegionReadOnlySize()                    { return 0x10000000; }
-template <>     uint64_t       SharedCache<x86_64>::sharedRegionReadOnlySize()                 { return 0x7FE00000; }
+template <>     uint64_t       SharedCache<x86>::sharedRegionStartWritableAddress(uint64_t exEnd)                      { return exEnd + 0x04000000; }
+template <>     uint64_t       SharedCache<x86_64>::sharedRegionStartWritableAddress(uint64_t exEnd)           { return 0x7FFF70000000LL; }
+template <>     uint64_t       SharedCache<arm>::sharedRegionStartWritableAddress(uint64_t exEnd)                      { return (exEnd + 16383) & (-16384); }
 
-template <>     uint64_t       SharedCache<ppc>::sharedRegionWritableSize()                    { return 0x10000000; }
-template <>     uint64_t       SharedCache<ppc64>::sharedRegionWritableSize()                  { return 0x20000000; }
-template <>     uint64_t       SharedCache<x86>::sharedRegionWritableSize()                    { return 0x10000000; }
-template <>     uint64_t       SharedCache<x86_64>::sharedRegionWritableSize()                 { return 0x20000000; }
+template <>     uint64_t       SharedCache<x86>::sharedRegionStartReadOnlyAddress(uint64_t wrEnd, uint64_t exEnd)       { return wrEnd + 0x04000000; }
+template <>     uint64_t       SharedCache<x86_64>::sharedRegionStartReadOnlyAddress(uint64_t wrEnd, uint64_t exEnd){ return exEnd; }
+template <>     uint64_t       SharedCache<arm>::sharedRegionStartReadOnlyAddress(uint64_t wrEnd, uint64_t exEnd)       { return (wrEnd + 16383) & (-16384); }
 
 
-template <>     const char*    SharedCache<ppc>::archName()    { return "ppc"; }
-template <>     const char*    SharedCache<ppc64>::archName()  { return "ppc64"; }
 template <>     const char*    SharedCache<x86>::archName()    { return "i386"; }
 template <>     const char*    SharedCache<x86_64>::archName() { return "x86_64"; }
+template <>     const char*    SharedCache<arm>::archName()    { return "arm"; }
+
+template <>     const char*    SharedCache<x86>::cacheFileSuffix(bool, const char* archName)   { return archName; }
+template <>     const char*    SharedCache<x86_64>::cacheFileSuffix(bool, const char* archName){ return archName; }
+template <>     const char*    SharedCache<arm>::cacheFileSuffix(bool, const char* archName)   { return archName; }
+
+
+template <>  uint64_t          SharedCache<x86>::pageAlign(uint64_t addr)    { return ( (addr + 4095) & (-4096) ); }
+template <>  uint64_t          SharedCache<x86_64>::pageAlign(uint64_t addr) { return ( (addr + 4095) & (-4096) ); }
+template <>  uint64_t          SharedCache<arm>::pageAlign(uint64_t addr)    { return ( (addr + 4095) & (-4096) ); }
 
-template <>     const char*    SharedCache<ppc>::filename(bool optimized)      { return optimized ? "ppc" : "rosetta"; }
-template <>     const char*    SharedCache<ppc64>::filename(bool)      { return "ppc64"; }
-template <>     const char*    SharedCache<x86>::filename(bool)        { return "i386"; }
-template <>     const char*    SharedCache<x86_64>::filename(bool)     { return "x86_64"; }
 
 template <typename A>
-SharedCache<A>::SharedCache(ArchGraph* graph, bool alphaSort, uint64_t dyldBaseAddress) 
-  : fArchGraph(graph), fDyldBaseAddress(dyldBaseAddress)
+SharedCache<A>::SharedCache(ArchGraph* graph, const char* rootPath, const char* overlayPath, const char* cacheDir, bool explicitCacheDir, bool alphaSort, bool verify, bool optimize, uint64_t dyldBaseAddress) 
+  : fArchGraph(graph), fVerify(verify), fExistingIsNotUpToDate(true), 
+       fCacheFileInFinalLocation(rootPath[0] == '\0'), fCacheFilePath(NULL),
+       fExistingCacheForVerification(NULL), fDyldBaseAddress(dyldBaseAddress),
+       fOffsetOfBindInfoInCombinedLinkedit(0), fOffsetOfWeakBindInfoInCombinedLinkedit(0),
+       fOffsetOfLazyBindInfoInCombinedLinkedit(0), fOffsetOfExportInfoInCombinedLinkedit(0),
+       fOffsetOfOldSymbolTableInfoInCombinedLinkedit(0), fSizeOfOldSymbolTableInfoInCombinedLinkedit(0),
+       fOffsetOfOldExternalRelocationsInCombinedLinkedit(0), fSizeOfOldExternalRelocationsInCombinedLinkedit(0),
+       fOffsetOfOldIndirectSymbolsInCombinedLinkedit(0), fSizeOfOldIndirectSymbolsInCombinedLinkedit(0),
+       fOffsetOfOldStringPoolInCombinedLinkedit(0), fSizeOfOldStringPoolInCombinedLinkedit(0),
+       fOffsetOfFunctionStartsInCombinedLinkedit(0), fSizeOfFunctionStartsInCombinedLinkedit(0),
+       fOffsetOfDataInCodeInCombinedLinkedit(0), fSizeOfDataInCodeInCombinedLinkedit(0),
+       fUnmappedLocalSymbolsSize(0)
 {
-       if ( fArchGraph->getArch() != arch() )
-               throw "wrong architecture";
-       
+       if ( fArchGraph->getArchPair().arch != arch() )
+               throwf("SharedCache object is wrong architecture: 0x%08X vs 0x%08X", fArchGraph->getArchPair().arch, arch());
+               
        // build vector of all shared dylibs
+       unsigned int aliasCount = 0;
        std::set<const MachOLayoutAbstraction*>& dylibs = fArchGraph->getSharedDylibs();
+       ArchGraph::StringToString& aliases = fArchGraph->getDylibAliases();
        for(std::set<const MachOLayoutAbstraction*>::iterator it = dylibs.begin(); it != dylibs.end(); ++it) {
                const MachOLayoutAbstraction* lib = *it;
                LayoutInfo temp;
@@ -503,28 +988,128 @@ SharedCache<A>::SharedCache(ArchGraph* graph, bool alphaSort, uint64_t dyldBaseA
                temp.info.address = 0;
                temp.info.modTime = lib->getLastModTime();
                temp.info.inode = lib->getInode();
-               temp.info.pathFileOffset = lib->getNameFileOffset();
+               temp.info.pathFileOffset = lib->getNameFileOffset();  // for now this is the offset within the dylib
+               for(ArchGraph::StringToString::iterator ait = aliases.begin(); ait != aliases.end(); ++ait) {
+                       if ( strcmp(ait->second, lib->getID().name) == 0 ) {
+                               temp.aliases.push_back(ait->first);
+                               ++aliasCount;
+                       }
+               }
                fDylibs.push_back(temp);
        }
+
+       // create path to cache file
+       char cachePathCanonical[MAXPATHLEN];
+       strcpy(cachePathCanonical, cacheDir);
+       if ( cachePathCanonical[strlen(cachePathCanonical)-1] != '/' )
+               strcat(cachePathCanonical, "/");
+       strcat(cachePathCanonical, DYLD_SHARED_CACHE_BASE_NAME);
+       strcat(cachePathCanonical, cacheFileSuffix(optimize, fArchGraph->archName()));
+       char cachePath[MAXPATHLEN];
+       if ( explicitCacheDir ) {
+               fCacheFilePath = strdup(cachePathCanonical);
+       }
+       else if ( overlayPath[0] != '\0' ) {
+               strcpy(cachePath, overlayPath);
+               strcat(cachePath, "/");
+               strcat(cachePath, cachePathCanonical);
+               fCacheFilePath = strdup(cachePath);
+       }
+       else if ( rootPath[0] != '\0' ) {
+               strcpy(cachePath, rootPath);
+               strcat(cachePath, "/");
+               strcat(cachePath, cachePathCanonical);
+               fCacheFilePath = strdup(cachePath);
+       }
+       else {
+               fCacheFilePath = strdup(cachePathCanonical);
+       }
+       if ( overlayPath[0] != '\0' ) {
+               // in overlay mode if there already is a cache file in the overlay
+               // check if it is up to date.  
+               struct stat stat_buf;
+               if ( stat(fCacheFilePath, &stat_buf) == 0 ) {
+                       fExistingIsNotUpToDate = this->notUpToDate(fCacheFilePath, aliasCount);
+               }
+               else if ( rootPath[0] != '\0' ) {
+                       // using -root and -overlay, but no cache file in overlay, check one in -root
+                       char cachePathRoot[MAXPATHLEN];
+                       strcpy(cachePathRoot, rootPath);
+                       strcat(cachePathRoot, "/");
+                       strcat(cachePathRoot, cachePathCanonical);
+                       fExistingIsNotUpToDate = this->notUpToDate(cachePathRoot, aliasCount);
+               }
+               else {
+                       // uisng -overlay, but no cache file in overlay, check one in boot volume
+                       fExistingIsNotUpToDate = this->notUpToDate(cachePathCanonical, aliasCount);
+               }
+       }
+       else {
+               fExistingIsNotUpToDate = this->notUpToDate(fCacheFilePath, aliasCount);
+       }
        
        // sort shared dylibs
-       if ( alphaSort )
+       if ( verify ) {
+               // already sorted by notUpToDate()
+       }
+       else if ( alphaSort ) {
                std::sort(fDylibs.begin(), fDylibs.end(), ByNameSorter());
-       else
-               std::sort(fDylibs.begin(), fDylibs.end(), RandomSorter(fDylibs));
-               
+       }
+       else {
+               // random sort for Address Space Randomization
+               std::map<const MachOLayoutAbstraction*, uint32_t> map;
+               for(typename std::vector<struct LayoutInfo>::const_iterator it = fDylibs.begin(); it != fDylibs.end(); ++it) 
+                       map[it->layout] = arc4random();
+               std::sort(fDylibs.begin(), fDylibs.end(), Sorter(map));
+       }
        
        // assign segments in each dylib a new address
-       this->assignNewBaseAddresses();
+       this->assignNewBaseAddresses(verify);
        
+       // calculate where string pool offset will start
        // calculate cache file header size
-       fHeaderSize = pageAlign(sizeof(dyld_cache_header) 
+       fHeaderSize = sizeof(dyld_cache_header) 
                                                        + fMappings.size()*sizeof(shared_file_mapping_np) 
-                                                       + fDylibs.size()*sizeof(dyld_cache_image_info) );
-                                                       //+ fDependencyPool.size()*sizeof(uint16_t));
+                                                       + (fDylibs.size()+aliasCount)*sizeof(dyld_cache_image_info);
+       const uint64_t baseHeaderSize = fHeaderSize;
+       //fprintf(stderr, "aliasCount=%d, fHeaderSize=0x%08X\n", aliasCount, fHeaderSize);
+       // build list of aliases and compute where each ones path string will go
+       for(typename std::vector<struct LayoutInfo>::const_iterator it = fDylibs.begin(); it != fDylibs.end(); ++it) {
+               for(std::vector<const char*>::const_iterator ait = it->aliases.begin(); ait != it->aliases.end(); ++ait) {
+                       LayoutInfo temp = *it;
+                       // alias looks just like real dylib, but has a different name string
+                       const char* aliasPath = *ait;
+                       temp.aliases.clear();
+                       temp.aliases.push_back(aliasPath);
+                       temp.info.pathFileOffset = fHeaderSize; 
+                       fDylibAliases.push_back(temp);
+                       fHeaderSize += strlen(aliasPath)+1;
+               }
+       }
+       std::sort(fDylibAliases.begin(), fDylibAliases.end(), ByNameSorter());
+       //fprintf(stderr, "fHeaderSize=0x%08X, fDylibAliases.size()=%lu\n", fHeaderSize, fDylibAliases.size());
+       fHeaderSize = pageAlign(fHeaderSize);
+       
+       // check that cache we are about to create for verification purposes has same layout as existing cache
+       if ( verify ) {
+               // if no existing cache, say so
+               if ( fExistingCacheForVerification == NULL ) {
+                       throwf("update_dyld_shared_cache[%u] for arch=%s, could not verify because cache file does not exist in /var/db/dyld/\n",
+                        getpid(), fArchGraph->archName());
+               }
+               const dyldCacheHeader<E>* header = (dyldCacheHeader<E>*)fExistingCacheForVerification;
+               const dyldCacheImageInfo<E>* cacheEntry = (dyldCacheImageInfo<E>*)(fExistingCacheForVerification + header->imagesOffset());
+               for(typename std::vector<LayoutInfo>::iterator it = fDylibs.begin(); it != fDylibs.end(); ++it, ++cacheEntry) {
+                       if ( cacheEntry->address() != it->layout->getSegments()[0].newAddress() ) {
+                               throwf("update_dyld_shared_cache[%u] warning: for arch=%s, could not verify cache because start address of %s is 0x%llX in cache, but should be 0x%llX\n",
+                                                       getpid(), fArchGraph->archName(), it->layout->getID().name, cacheEntry->address(), it->layout->getSegments()[0].newAddress());
+                       }
+               }
+       }
        
-       if ( fHeaderSize > 0x3000 )
-               throwf("header size miscalculation 0x%08X", fHeaderSize);
+       
+       if ( fHeaderSize > FIRST_DYLIB_TEXT_OFFSET )
+               throwf("header size overflow: allowed=0x%08X, base=0x%08llX, aliases=0x%08llX", FIRST_DYLIB_TEXT_OFFSET, baseHeaderSize, fHeaderSize-baseHeaderSize);
 }
 
 
@@ -534,118 +1119,84 @@ uint64_t SharedCache<A>::getWritableSegmentNewAddress(uint64_t proposedNewAddres
        return proposedNewAddress;
 }
 
-template <>
-uint64_t SharedCache<ppc>::getWritableSegmentNewAddress(uint64_t proposedNewAddress, uint64_t originalAddress, uint64_t executableSlide)
-{
-       // for ppc64 writable segments can only move in increments of 64K (so only hi16 instruction needs to be modified)
-       return (((executableSlide & 0x000000000000F000ULL) - ((proposedNewAddress - originalAddress) & 0x000000000000F000ULL)) & 0x000000000000F000ULL) + proposedNewAddress;
-}
-
-template <>
-uint64_t SharedCache<ppc64>::getWritableSegmentNewAddress(uint64_t proposedNewAddress, uint64_t originalAddress, uint64_t executableSlide)
-{
-       // for ppc64 writable segments can only move in increments of 64K (so only hi16 instruction needs to be modified)
-       return (((executableSlide & 0x000000000000F000ULL) - ((proposedNewAddress - originalAddress) & 0x000000000000F000ULL)) & 0x000000000000F000ULL) + proposedNewAddress;
-}
-
 
 template <typename A>
-void SharedCache<A>::assignNewBaseAddresses()
+void SharedCache<A>::assignNewBaseAddresses(bool verify)
 {
-       // first layout TEXT and DATA for split-seg (or can be split-seg) dylibs
-       uint64_t currentExecuteAddress = sharedRegionReadOnlyStartAddress() + 0x3000;   
-       uint64_t currentWritableAddress = sharedRegionWritableStartAddress();
+       // first layout TEXT for dylibs
+       const uint64_t startExecuteAddress = sharedRegionStartAddress();
+       uint64_t currentExecuteAddress = startExecuteAddress + FIRST_DYLIB_TEXT_OFFSET; 
        for(typename std::vector<LayoutInfo>::iterator it = fDylibs.begin(); it != fDylibs.end(); ++it) {
                std::vector<MachOLayoutAbstraction::Segment>& segs = ((MachOLayoutAbstraction*)(it->layout))->getSegments();
-               MachOLayoutAbstraction::Segment* executableSegment = NULL;
                for (int i=0; i < segs.size(); ++i) {
                        MachOLayoutAbstraction::Segment& seg = segs[i];
-                       if ( seg.writable() ) {
-                               if ( seg.executable() && it->layout->hasSplitSegInfo() ) {
-                                       // skip __IMPORT segments in this pass
-                               }
-                               else {
-                                       // __DATA segment
-                                       // for ppc, writable segments have to move in 64K increments
-                                       if (  it->layout->hasSplitSegInfo() ) {
-                                               if ( executableSegment == NULL )
-                                                       throwf("first segment in dylib is not executable for %s", it->layout->getID().name);
-                                               seg.setNewAddress(getWritableSegmentNewAddress(currentWritableAddress, seg.address(), executableSegment->newAddress() - executableSegment->address()));
-                                       }
-                                       else
-                                               seg.setNewAddress(currentWritableAddress);
-                                       currentWritableAddress = pageAlign(seg.newAddress() + seg.size());
-                               }
+                       seg.reset();
+                       if ( seg.executable() && !seg.writable() ) {
+                               // __TEXT segment
+                               if ( it->info.address == 0 )
+                                       it->info.address = currentExecuteAddress;
+                               seg.setNewAddress(currentExecuteAddress);
+                               currentExecuteAddress += pageAlign(seg.size());
                        }
-                       else {
-                               if ( seg.executable() ) {
-                                       // __TEXT segment
-                                       if ( it->info.address == 0 )
-                                               it->info.address = currentExecuteAddress;
-                                       executableSegment = &seg;
-                                       seg.setNewAddress(currentExecuteAddress);
-                                       currentExecuteAddress += pageAlign(seg.size());
-                               }
-                               else {
-                                       // skip read-only segments in this pass
-                                       // any non-LINKEDIT read-only segments leave a hole so that all R/W segment slide together
-                                       if ( (strcmp(seg.name(), "__LINKEDIT") != 0) && (i < (segs.size()-2)) ) {
-                                               fprintf(stderr, "update_dyld_shared_cache: warning %s segment in %s leaves a hole\n", seg.name(), it->layout->getID().name);
-                                               currentWritableAddress = pageAlign(currentWritableAddress + seg.size());
-                                       }
-                               }
+               }
+       }
+
+       // layout DATA for dylibs
+       const uint64_t startWritableAddress = sharedRegionStartWritableAddress(currentExecuteAddress);
+       uint64_t currentWritableAddress = startWritableAddress;
+       for(typename std::vector<LayoutInfo>::iterator it = fDylibs.begin(); it != fDylibs.end(); ++it) {
+               std::vector<MachOLayoutAbstraction::Segment>& segs = ((MachOLayoutAbstraction*)(it->layout))->getSegments();
+               for (int i=0; i < segs.size(); ++i) {
+                       MachOLayoutAbstraction::Segment& seg = segs[i];
+                       seg.reset();
+                       if ( seg.writable() ) {
+                               if ( seg.executable() ) 
+                                       throw "found writable and executable segment";
+                               // __DATA segment
+                               seg.setNewAddress(currentWritableAddress);
+                               currentWritableAddress = pageAlign(seg.newAddress() + seg.size());
                        }
                }
        }
 
-       // append all read-only (but not LINKEDIT) segments at end of all TEXT segments
-       // append all IMPORT segments at end of all DATA segments rounded to next 2MB 
-       uint64_t currentReadOnlyAddress = currentExecuteAddress;
-       uint64_t startWritableExecutableAddress = (currentWritableAddress + 0x200000 - 1) & (-0x200000);
-       uint64_t currentWritableExecutableAddress = startWritableExecutableAddress;
+       // layout all read-only (but not LINKEDIT) segments
+       const uint64_t startReadOnlyAddress = sharedRegionStartReadOnlyAddress(currentWritableAddress, currentExecuteAddress);
+       uint64_t currentReadOnlyAddress = startReadOnlyAddress;
        for(typename std::vector<LayoutInfo>::iterator it = fDylibs.begin(); it != fDylibs.end(); ++it) {
                std::vector<MachOLayoutAbstraction::Segment>& segs = ((MachOLayoutAbstraction*)(it->layout))->getSegments();
                for(int i=0; i < segs.size(); ++i) {
                        MachOLayoutAbstraction::Segment& seg = segs[i];
-                       if ( !seg.writable() && !seg.executable() && (strcmp(seg.name(), "__LINKEDIT") != 0) ) {
-                               // allocate non-executable,read-only segments from end of read only shared region
+                       if ( seg.readable() && !seg.writable() && !seg.executable() && (strcmp(seg.name(), "__LINKEDIT") != 0) ) {
+                               // __UNICODE segment
                                seg.setNewAddress(currentReadOnlyAddress);
                                currentReadOnlyAddress += pageAlign(seg.size());
                        }
-                       else if ( seg.writable() && seg.executable() && it->layout->hasSplitSegInfo() ) {
-                               // allocate IMPORT segments to end of writable shared region
-                               seg.setNewAddress(currentWritableExecutableAddress);
-                               seg.setWritable(false); // __IMPORT segments are not-writable in shared cache
-                               currentWritableExecutableAddress += pageAlign(seg.size());
-                       }
                }
        }       
 
-       // append all LINKEDIT segments at end of all read-only segments
+       // layout all LINKEDIT segments at end of all read-only segments
        fLinkEditsStartAddress = currentReadOnlyAddress;
        fFirstLinkEditSegment = NULL;
        for(typename std::vector<LayoutInfo>::iterator it = fDylibs.begin(); it != fDylibs.end(); ++it) {
                std::vector<MachOLayoutAbstraction::Segment>& segs = ((MachOLayoutAbstraction*)(it->layout))->getSegments();
                for(int i=0; i < segs.size(); ++i) {
                        MachOLayoutAbstraction::Segment& seg = segs[i];
-                       if ( !seg.writable() && !seg.executable() && (strcmp(seg.name(), "__LINKEDIT") == 0) ) {
+                       if ( seg.readable() && !seg.writable() && !seg.executable() && (strcmp(seg.name(), "__LINKEDIT") == 0) ) {
                                if ( fFirstLinkEditSegment == NULL ) 
                                        fFirstLinkEditSegment = &seg;
-                               // allocate non-executable,read-only segments from end of read only shared region
                                seg.setNewAddress(currentReadOnlyAddress);
                                currentReadOnlyAddress += pageAlign(seg.size());
                        }
                }
        }
-       fLinkEditsTotalUnoptimizedSize = (currentReadOnlyAddress - fLinkEditsStartAddress + 4095) & (-4096);
-
+       fLinkEditsTotalUnoptimizedSize = pageAlign(currentReadOnlyAddress - fLinkEditsStartAddress);
 
        // populate large mappings
        uint64_t cacheFileOffset = 0;
-       if ( currentExecuteAddress > sharedRegionReadOnlyStartAddress() + 0x3000 ) {
+       if ( currentExecuteAddress > startExecuteAddress ) {
                shared_file_mapping_np  executeMapping;
-               executeMapping.sfm_address              = sharedRegionReadOnlyStartAddress();
-               executeMapping.sfm_size                 = currentExecuteAddress - sharedRegionReadOnlyStartAddress();
+               executeMapping.sfm_address              = startExecuteAddress;
+               executeMapping.sfm_size                 = currentExecuteAddress - startExecuteAddress;
                executeMapping.sfm_file_offset  = cacheFileOffset;
                executeMapping.sfm_max_prot             = VM_PROT_READ | VM_PROT_EXECUTE;
                executeMapping.sfm_init_prot    = VM_PROT_READ | VM_PROT_EXECUTE;
@@ -653,30 +1204,18 @@ void SharedCache<A>::assignNewBaseAddresses()
                cacheFileOffset += executeMapping.sfm_size;
                
                shared_file_mapping_np  writableMapping;
-               writableMapping.sfm_address             = sharedRegionWritableStartAddress();
-               writableMapping.sfm_size                = currentWritableAddress - sharedRegionWritableStartAddress();
+               writableMapping.sfm_address             = startWritableAddress;
+               writableMapping.sfm_size                = currentWritableAddress - startWritableAddress;
                writableMapping.sfm_file_offset = cacheFileOffset;
                writableMapping.sfm_max_prot    = VM_PROT_READ | VM_PROT_WRITE;
                writableMapping.sfm_init_prot   = VM_PROT_READ | VM_PROT_WRITE;
                fMappings.push_back(writableMapping);
                cacheFileOffset += writableMapping.sfm_size;
-               
-               if ( currentWritableExecutableAddress > startWritableExecutableAddress ) {
-                       shared_file_mapping_np  writableExecutableMapping;
-                       writableExecutableMapping.sfm_address   = startWritableExecutableAddress;
-                       writableExecutableMapping.sfm_size              = currentWritableExecutableAddress - startWritableExecutableAddress;
-                       writableExecutableMapping.sfm_file_offset= cacheFileOffset;
-                       writableExecutableMapping.sfm_max_prot  = VM_PROT_READ | VM_PROT_WRITE | VM_PROT_EXECUTE;
-                       // __IMPORT segments in shared cache are not writable 
-                       writableExecutableMapping.sfm_init_prot = VM_PROT_READ | VM_PROT_EXECUTE; 
-                       fMappings.push_back(writableExecutableMapping);
-                       cacheFileOffset += writableExecutableMapping.sfm_size;
-               }
-               
+                               
                // make read-only (contains LINKEDIT segments) last, so it can be cut back when optimized
                shared_file_mapping_np  readOnlyMapping;
-               readOnlyMapping.sfm_address             = currentExecuteAddress;
-               readOnlyMapping.sfm_size                = currentReadOnlyAddress - currentExecuteAddress;
+               readOnlyMapping.sfm_address             = startReadOnlyAddress;
+               readOnlyMapping.sfm_size                = currentReadOnlyAddress - startReadOnlyAddress;
                readOnlyMapping.sfm_file_offset = cacheFileOffset;
                readOnlyMapping.sfm_max_prot    = VM_PROT_READ;
                readOnlyMapping.sfm_init_prot   = VM_PROT_READ;
@@ -686,8 +1225,8 @@ void SharedCache<A>::assignNewBaseAddresses()
        else {
                // empty cache
                shared_file_mapping_np  cacheHeaderMapping;
-               cacheHeaderMapping.sfm_address          = sharedRegionWritableStartAddress();
-               cacheHeaderMapping.sfm_size                     = 0x3000;
+               cacheHeaderMapping.sfm_address          = startExecuteAddress;
+               cacheHeaderMapping.sfm_size                     = FIRST_DYLIB_TEXT_OFFSET;
                cacheHeaderMapping.sfm_file_offset      = cacheFileOffset;
                cacheHeaderMapping.sfm_max_prot         = VM_PROT_READ;
                cacheHeaderMapping.sfm_init_prot        = VM_PROT_READ;
@@ -698,163 +1237,202 @@ void SharedCache<A>::assignNewBaseAddresses()
 
 
 template <typename A>
-uint64_t SharedCache<A>::cacheFileOffsetForAddress(uint64_t addr)
+uint64_t SharedCache<A>::cacheFileOffsetForVMAddress(uint64_t vmaddr) const
 {
-       for(std::vector<shared_file_mapping_np>::iterator it = fMappings.begin(); it != fMappings.end(); ++it) {
-               if ( (it->sfm_address <= addr) && (addr < it->sfm_address+it->sfm_size) )
-                       return it->sfm_file_offset + addr - it->sfm_address;
+       for(std::vector<shared_file_mapping_np>::const_iterator it = fMappings.begin(); it != fMappings.end(); ++it) {
+               if ( (it->sfm_address <= vmaddr) && (vmaddr < it->sfm_address+it->sfm_size) )
+                       return it->sfm_file_offset + vmaddr - it->sfm_address;
        }
-       throwf("address 0x%0llX is not in cache", addr);
+       throwf("address 0x%0llX is not in cache", vmaddr);
+}
+
+template <typename A>
+uint64_t SharedCache<A>::VMAddressForCacheFileOffset(uint64_t offset) const
+{
+    for(std::vector<shared_file_mapping_np>::const_iterator it = fMappings.begin(); it != fMappings.end(); ++it) {
+        if ( (it->sfm_file_offset <= offset) && (offset < it->sfm_file_offset+it->sfm_size) )
+            return it->sfm_address + offset - it->sfm_file_offset;
+    }
+    throwf("offset 0x%0llX is not in cache", offset);
+}
+
+template <typename A>
+void *SharedCache<A>::mappedAddressForVMAddress(uint64_t vmaddr)
+{
+    if (!vmaddr) return NULL;
+    else return fInMemoryCache + cacheFileOffsetForVMAddress(vmaddr);
+}
+
+template <typename A>
+uint64_t SharedCache<A>::VMAddressForMappedAddress(const void *mapaddr)
+{
+    if (!mapaddr) return 0;
+    uint64_t offset = (uint8_t *)mapaddr - (uint8_t *)fInMemoryCache;
+    return VMAddressForCacheFileOffset(offset);
 }
 
 
 template <typename A>
-bool SharedCache<A>::notUpToDate(const void* cache)
+bool SharedCache<A>::notUpToDate(const void* cache, unsigned int aliasCount)
 {
        dyldCacheHeader<E>* header = (dyldCacheHeader<E>*)cache;
        // not valid if header signature is wrong
+       const char* archPairName = fArchGraph->archName();
        char temp[16];
        strcpy(temp, "dyld_v1        ");
-       strcpy(&temp[15-strlen(archName())], archName());
-       if ( strcmp(header->magic(), temp) != 0 ) 
-               return true;
+       strcpy(&temp[15-strlen(archPairName)], archPairName);
+       if ( strcmp(header->magic(), temp) != 0 ) {
+               if ( fVerify ) {
+                       fprintf(stderr, "update_dyld_shared_cache[%u] cannot verify %s because current cache file has invalid header\n", getpid(), archName());
+                       return false;
+               }
+               else {
+                       fprintf(stderr, "update_dyld_shared_cache[%u] updating cache because current cache file has invalid header\n", getpid());
+                       return true;
+               }
+       }
        // not valid if count of images does not match current images needed
-       if ( header->imagesCount() != fDylibs.size() )
-               return true;
+       if ( header->imagesCount() != (fDylibs.size()+aliasCount) ) {
+               if ( fVerify ) {
+                       fprintf(stderr, "update_dyld_shared_cache[%u] cannot verify %s because current cache file contains a different set of dylibs\n", getpid(), archName());
+                       return false;
+               }
+               else {
+                       fprintf(stderr, "update_dyld_shared_cache[%u] updating %s cache because current cache file contains a different set of dylibs\n", getpid(), archName());
+                       return true;
+               }
+       }
+       // get end of TEXT region
+       const dyldCacheFileMapping<E>* textMapping = (dyldCacheFileMapping<E>*)((uint8_t*)cache+sizeof(dyldCacheHeader<E>));
+       const uint32_t textSize = textMapping->size();
+       
        // verify every dylib in constructed graph is in existing cache with same inode and modTime     
+       std::map<const MachOLayoutAbstraction*, uint32_t> sortingMap;
        const dyldCacheImageInfo<E>* imagesStart = (dyldCacheImageInfo<E>*)((uint8_t*)cache + header->imagesOffset());
        const dyldCacheImageInfo<E>* imagesEnd = &imagesStart[header->imagesCount()];
        for(typename std::vector<LayoutInfo>::iterator it = fDylibs.begin(); it != fDylibs.end(); ++it) {
                bool found = false;
                //fprintf(stderr, "inode=0x%llX, mTime=0x%llX, path=%s\n", it->info.inode, it->info.modTime, it->layout->getID().name);
                for(const dyldCacheImageInfo<E>* cacheEntry = imagesStart; cacheEntry < imagesEnd; ++cacheEntry) {
-                       if ( (cacheEntry->inode() == it->info.inode) 
-                        && (cacheEntry->modTime() == it->info.modTime) 
-                        && (strcmp((char*)cache+cacheEntry->pathFileOffset(), it->layout->getID().name) == 0) ) {
+                       if ( fVerify ) {
+                               if ( cacheEntry->pathFileOffset() > textSize ) {
+                                       throwf("update_dyld_shared_cache[%u]: for arch=%s, image entries corrupt, bad path offset in %s\n", 
+                                                               getpid(), archName(), it->layout->getID().name);
+                               }
+                               // in -verify mode, just match by path and warn if file looks different
+                               if ( strcmp((char*)cache+cacheEntry->pathFileOffset(), it->layout->getID().name) == 0 ) {
+                                       found = true;
+                                       sortingMap[it->layout] = cacheEntry-imagesStart;
+                                       if ( (cacheEntry->inode() != it->info.inode) || (cacheEntry->modTime() != it->info.modTime) ) {
+                                               fprintf(stderr, "update_dyld_shared_cache[%u] warning: for arch=%s, %s has changed since cache was built\n", 
+                                                               getpid(), archName(), it->layout->getID().name);
+                                       }
+                                       break;
+                               }
+                       }
+                       else {
+                               if ( cacheEntry->pathFileOffset() > textSize ) {
+                                       // cache corrupt, needs to be regenerated
+                                       return true;
+                               }
+                               // in normal update mode, everything has to match for cache to be up-to-date
+                               if ( (cacheEntry->inode() == it->info.inode) 
+                                               && (cacheEntry->modTime() == it->info.modTime) 
+                                               && (strcmp((char*)cache+cacheEntry->pathFileOffset(), it->layout->getID().name) == 0) ) {
                                        found = true;
                                        break;
+                               }
                        }
                }
                if ( !found ) {
-                       fprintf(stderr, "update_dyld_shared_cache[%u] current cache invalid because %s has changed\n", getpid(), it->layout->getID().name);
-                       return true;
+                       if ( fVerify ) {
+                               throwf("update_dyld_shared_cache[%u] can't verify %s cache because %s is not in existing cache\n", getpid(), archName(), it->layout->getID().name);
+                       }
+                       else {
+                               fprintf(stderr, "update_dyld_shared_cache[%u] updating %s cache because dylib at %s has changed\n", getpid(), archName(), it->layout->getID().name);
+                               return true;
+                       }
                }
        }
-       return false;
+       // all dylibs in existing cache file match those determined need to be in shared cache
+       if ( fVerify ) {
+               // sort fDylibs to match existing cache file so we can compare content
+               std::sort(fDylibs.begin(), fDylibs.end(), Sorter(sortingMap));
+               //fprintf(stderr, "dylibs sorted like existing cache:\n");
+               //for(typename std::vector<LayoutInfo>::iterator it = fDylibs.begin(); it != fDylibs.end(); ++it) {
+               //      fprintf(stderr,"   %s\n", it->layout->getID().name);
+               //}
+               // do regenerate a new cache so we can compare content with existing
+               return true;
+       }
+       else {
+               // existing cache file is up-to-date, don't need to regenerate
+               return false;
+       }
 }
 
 
 template <typename A>
-bool SharedCache<A>::notUpToDate(const char* cachePath)
+bool SharedCache<A>::notUpToDate(const char* path, unsigned int aliasCount)
 {
        // mmap existing cache file 
-       int fd = ::open(cachePath, O_RDONLY);   
+       int fd = ::open(path, O_RDONLY);        
        if ( fd == -1 )
                return true;
        struct stat stat_buf;
        ::fstat(fd, &stat_buf);
-       uint8_t* mappingAddr = (uint8_t*)mmap(NULL, stat_buf.st_size, PROT_READ , MAP_FILE | MAP_PRIVATE, fd, 0);
+    uint32_t cacheFileSize = stat_buf.st_size;
+    uint32_t cacheAllocatedSize = pageAlign(cacheFileSize);
+    uint8_t* mappingAddr = NULL;
+       if ( vm_allocate(mach_task_self(), (vm_address_t*)(&mappingAddr), cacheAllocatedSize, VM_FLAGS_ANYWHERE) != KERN_SUCCESS )
+        throwf("can't vm_allocate cache of size %u", cacheFileSize);
+    // <rdar://problem/8960832> update_dyld_shared_cache -verify finds differences
+       (void)fcntl(fd, F_NOCACHE, 1);
+    ssize_t readResult = pread(fd, mappingAddr, cacheFileSize, 0);
+    if ( readResult != cacheFileSize )
+        throwf("can't read all of existing cache file (%lu of %u): %s", readResult, cacheFileSize, path);
        ::close(fd);
-       if ( mappingAddr == (uint8_t*)(-1) )
-               return true;
 
        // validate it
-       bool result = this->notUpToDate(mappingAddr);
-       // unmap
-       ::munmap(mappingAddr, stat_buf.st_size);
-       if ( verbose && !result )
-               fprintf(stderr, "update_dyld_shared_cache: %s is up-to-date\n", cachePath);
-
-       return result;
-}
-
-class CStringEquals
-{
-public:
-       bool operator()(const char* left, const char* right) const { return (strcmp(left, right) == 0); }
-};
-
-class StringPool
-{
-public:
-                               StringPool();
-       const char*     getBuffer();
-       uint32_t        size();
-       uint32_t        add(const char* str);
-       uint32_t        addUnique(const char* str);
-       const char* stringAtIndex(uint32_t) const;
-private:
-       typedef __gnu_cxx::hash_map<const char*, uint32_t, __gnu_cxx::hash<const char*>, CStringEquals> StringToOffset;
-
-       char*                   fBuffer;
-       uint32_t                fBufferAllocated;
-       uint32_t                fBufferUsed;
-       StringToOffset  fUniqueStrings;
-};
-
-
-StringPool::StringPool() 
-       : fBufferUsed(0), fBufferAllocated(4*1024*1024)
-{
-       fBuffer = (char*)malloc(fBufferAllocated);
-}
-
-uint32_t StringPool::add(const char* str)
-{
-       uint32_t len = strlen(str);
-       if ( (fBufferUsed + len + 1) > fBufferAllocated ) {
-               // grow buffer
-               fBufferAllocated = fBufferAllocated*2;
-               fBuffer = (char*)realloc(fBuffer, fBufferAllocated);
+       bool result = this->notUpToDate(mappingAddr, aliasCount);
+       if ( fVerify ) {
+               // don't unmap yet, leave so it can be verified later
+               fExistingCacheForVerification = mappingAddr;
        }
-       strcpy(&fBuffer[fBufferUsed], str);
-       uint32_t result = fBufferUsed;
-       fUniqueStrings[&fBuffer[fBufferUsed]] = result;
-       fBufferUsed += len+1;
-       return result;
-}
-
-uint32_t StringPool::addUnique(const char* str)
-{
-       StringToOffset::iterator pos = fUniqueStrings.find(str);
-       if ( pos != fUniqueStrings.end() ) 
-               return pos->second;
        else {
-               //fprintf(stderr, "StringPool::addUnique() new string: %s\n", str);
-               return this->add(str);
+               // unmap
+        vm_deallocate(mach_task_self(), (vm_address_t)mappingAddr, cacheAllocatedSize);
+               if ( verbose && !result )
+                       fprintf(stderr, "update_dyld_shared_cache: %s is up-to-date\n", path);
        }
+       return result;
 }
 
-uint32_t StringPool::size()
-{
-       return fBufferUsed;
-}
-
-const char*    StringPool::getBuffer()
-{
-       return fBuffer;
-}
-
-const char* StringPool::stringAtIndex(uint32_t index) const
-{
-       return &fBuffer[index];
-}
 
 
 template <typename A>
 class LinkEditOptimizer
 {
 public:
-                                                                                       LinkEditOptimizer(const MachOLayoutAbstraction&, uint8_t*, StringPool&);
+                                                                                       LinkEditOptimizer(const MachOLayoutAbstraction&, const SharedCache<A>&, uint8_t*, StringPool&);
        virtual                                                                 ~LinkEditOptimizer() {}
 
-       static void                                                             makeDummyLocalSymbol(uint32_t&, uint8_t*, StringPool&);
-               void                                                            copyLocalSymbols();
-               void                                                            copyExportedSymbols(uint32_t&);
-               void                                                            copyImportedSymbols(uint32_t&);
-               void                                                            copyExternalRelocations(uint32_t&);
-               void                                                            copyIndirectSymbolTable(uint32_t&);
-               void                                                            updateLoadCommands(uint64_t newVMAddress, uint64_t size, uint32_t stringPoolOffset);
+               void                                                            copyBindInfo(uint32_t&);
+               void                                                            copyWeakBindInfo(uint32_t&);
+               void                                                            copyLazyBindInfo(uint32_t&);
+               void                                                            copyExportInfo(uint32_t&);
+               void                                                            copyLocalSymbols(uint32_t symbolTableOffset, uint32_t&, bool dontMapLocalSymbols,
+                                                                                                                       uint8_t* cacheStart, StringPool& unmappedLocalsStringPool, 
+                                                                                                                       std::vector<macho_nlist<typename A::P> >& unmappedSymbols,
+                                                                                                                       std::vector<LocalSymbolInfo>& info);
+               void                                                            copyExportedSymbols(uint32_t symbolTableOffset, uint32_t&);
+               void                                                            copyImportedSymbols(uint32_t symbolTableOffset, uint32_t&);
+               void                                                            copyExternalRelocations(uint32_t& offset);
+               void                                                            copyIndirectSymbolTable(uint32_t& offset);
+               void                                                            copyFunctionStarts(uint32_t& offset);
+               void                                                            copyDataInCode(uint32_t& offset);
+               void                                                            updateLoadCommands(uint64_t newVMAddress, uint64_t size, uint32_t stringPoolOffset, 
+                                                                                                                               uint32_t linkEditsFileOffset, bool keepSignatures);
        
 
 protected:
@@ -864,16 +1442,29 @@ protected:
                        
 private:
 
+       const SharedCache<A>&                                           fSharedCache;
        const macho_header<P>*                                          fHeader; 
        uint8_t*                                                                        fNewLinkEditStart;      
        uint8_t*                                                                        fLinkEditBase;          
        const MachOLayoutAbstraction&                           fLayout;
+       macho_dyld_info_command<P>*                                     fDyldInfo;
        macho_dysymtab_command<P>*                                      fDynamicSymbolTable;
+       macho_linkedit_data_command<P>*                         fFunctionStarts;
+       macho_linkedit_data_command<P>*                         fDataInCode;
        macho_symtab_command<P>*                                        fSymbolTableLoadCommand;
        const macho_nlist<P>*                                           fSymbolTable;
        const char*                                                                     fStrings;
        StringPool&                                                                     fNewStringPool;
        std::map<uint32_t,uint32_t>                                     fOldToNewSymbolIndexes;
+       uint32_t                                                                        fBindInfoOffsetIntoNewLinkEdit;
+       uint32_t                                                                        fBindInfoSizeInNewLinkEdit;
+       uint32_t                                                                        fWeakBindInfoOffsetIntoNewLinkEdit;
+       uint32_t                                                                        fWeakBindInfoSizeInNewLinkEdit;
+       uint32_t                                                                        fLazyBindInfoOffsetIntoNewLinkEdit;
+       uint32_t                                                                        fLazyBindInfoSizeInNewLinkEdit;
+       uint32_t                                                                        fExportInfoOffsetIntoNewLinkEdit;
+       uint32_t                                                                        fExportInfoSizeInNewLinkEdit;
+       uint32_t                                                                        fSymbolTableStartOffsetInNewLinkEdit;
        uint32_t                                                                        fLocalSymbolsStartIndexInNewLinkEdit;
        uint32_t                                                                        fLocalSymbolsCountInNewLinkEdit;
        uint32_t                                                                        fExportedSymbolsStartIndexInNewLinkEdit;
@@ -882,20 +1473,30 @@ private:
        uint32_t                                                                        fImportedSymbolsCountInNewLinkEdit;
        uint32_t                                                                        fExternalRelocationsOffsetIntoNewLinkEdit;
        uint32_t                                                                        fIndirectSymbolTableOffsetInfoNewLinkEdit;
-       static int32_t                                                          fgLocalSymbolsStartIndexInNewLinkEdit;
+       uint32_t                                                                        fFunctionStartsOffsetInNewLinkEdit;
+       uint32_t                                                                        fDataInCodeOffsetInNewLinkEdit;
+       uint32_t                                                                        fUnmappedLocalSymbolsStartIndexInNewLinkEdit;
+       uint32_t                                                                        fUnmappedLocalSymbolsCountInNewLinkEdit;
 };
 
-template <typename A> int32_t LinkEditOptimizer<A>::fgLocalSymbolsStartIndexInNewLinkEdit = 0;
 
 
 template <typename A>
-LinkEditOptimizer<A>::LinkEditOptimizer(const MachOLayoutAbstraction& layout, uint8_t* newLinkEdit, StringPool& stringPool)
- :     fLayout(layout), fLinkEditBase(NULL), fNewLinkEditStart(newLinkEdit), 
-       fDynamicSymbolTable(NULL), fSymbolTableLoadCommand(NULL), fSymbolTable(NULL), fStrings(NULL), fNewStringPool(stringPool),
+LinkEditOptimizer<A>::LinkEditOptimizer(const MachOLayoutAbstraction& layout, const SharedCache<A>& sharedCache, uint8_t* newLinkEdit, StringPool& stringPool)
+ :     fSharedCache(sharedCache), fLayout(layout), fLinkEditBase(NULL), fNewLinkEditStart(newLinkEdit), fDyldInfo(NULL),
+       fDynamicSymbolTable(NULL), fFunctionStarts(NULL), fDataInCode(NULL), 
+       fSymbolTableLoadCommand(NULL), fSymbolTable(NULL), fStrings(NULL), fNewStringPool(stringPool),
+       fBindInfoOffsetIntoNewLinkEdit(0), fBindInfoSizeInNewLinkEdit(0),
+       fWeakBindInfoOffsetIntoNewLinkEdit(0), fWeakBindInfoSizeInNewLinkEdit(0),
+       fLazyBindInfoOffsetIntoNewLinkEdit(0), fLazyBindInfoSizeInNewLinkEdit(0),
+       fExportInfoOffsetIntoNewLinkEdit(0), fExportInfoSizeInNewLinkEdit(0),
+       fSymbolTableStartOffsetInNewLinkEdit(0), 
        fLocalSymbolsStartIndexInNewLinkEdit(0), fLocalSymbolsCountInNewLinkEdit(0),
        fExportedSymbolsStartIndexInNewLinkEdit(0), fExportedSymbolsCountInNewLinkEdit(0),
        fImportSymbolsStartIndexInNewLinkEdit(0), fImportedSymbolsCountInNewLinkEdit(0),
-       fExternalRelocationsOffsetIntoNewLinkEdit(0), fIndirectSymbolTableOffsetInfoNewLinkEdit(0)
+       fExternalRelocationsOffsetIntoNewLinkEdit(0), fIndirectSymbolTableOffsetInfoNewLinkEdit(0),
+       fFunctionStartsOffsetInNewLinkEdit(0), fDataInCodeOffsetInNewLinkEdit(0),
+       fUnmappedLocalSymbolsStartIndexInNewLinkEdit(0), fUnmappedLocalSymbolsCountInNewLinkEdit(0)
        
 {
        fHeader = (const macho_header<P>*)fLayout.getSegments()[0].mappedAddress();
@@ -924,6 +1525,15 @@ LinkEditOptimizer<A>::LinkEditOptimizer(const MachOLayoutAbstraction& layout, ui
                        case LC_DYSYMTAB:
                                fDynamicSymbolTable = (macho_dysymtab_command<P>*)cmd;
                                break;
+                       case LC_DYLD_INFO:
+                       case LC_DYLD_INFO_ONLY:
+                               fDyldInfo = (macho_dyld_info_command<P>*)cmd;
+                               break;
+                       case LC_FUNCTION_STARTS:
+                               fFunctionStarts = (macho_linkedit_data_command<P>*)cmd;
+                       case LC_DATA_IN_CODE:
+                               fDataInCode = (macho_linkedit_data_command<P>*)cmd;
+                               break;
                }
                cmd = (const macho_load_command<P>*)(((uint8_t*)cmd)+cmd->cmdsize());
        }       
@@ -951,51 +1561,117 @@ private:
 
 
 template <typename A>
-void LinkEditOptimizer<A>::makeDummyLocalSymbol(uint32_t& symbolIndex, uint8_t* storage, StringPool& pool)
+void LinkEditOptimizer<A>::copyBindInfo(uint32_t& offset)
 {
-       fgLocalSymbolsStartIndexInNewLinkEdit = symbolIndex;
-       macho_nlist<P>* newSymbolEntry = (macho_nlist<P>*)storage;
-       newSymbolEntry->set_n_strx(pool.add("__no_local_symbols_in_dyld_shared_cache"));
-       newSymbolEntry->set_n_type(N_SECT);
-       newSymbolEntry->set_n_sect(1);
-       newSymbolEntry->set_n_desc(0);
-       newSymbolEntry->set_n_value(0);
-       ++symbolIndex;
+       if ( (fDyldInfo != NULL) && (fDyldInfo->bind_off() != 0) ) {
+               fBindInfoOffsetIntoNewLinkEdit = offset;
+               fBindInfoSizeInNewLinkEdit = fDyldInfo->bind_size();
+               memcpy(fNewLinkEditStart+offset, &fLinkEditBase[fDyldInfo->bind_off()], fDyldInfo->bind_size());
+               offset += fDyldInfo->bind_size();
+       }
+}
+
+template <typename A>
+void LinkEditOptimizer<A>::copyWeakBindInfo(uint32_t& offset)
+{
+       if ( (fDyldInfo != NULL) && (fDyldInfo->weak_bind_off() != 0) ) {
+               fWeakBindInfoOffsetIntoNewLinkEdit = offset;
+               fWeakBindInfoSizeInNewLinkEdit = fDyldInfo->weak_bind_size();
+               memcpy(fNewLinkEditStart+offset, &fLinkEditBase[fDyldInfo->weak_bind_off()], fDyldInfo->weak_bind_size());
+               offset += fDyldInfo->weak_bind_size();
+       }
 }
 
 template <typename A>
-void LinkEditOptimizer<A>::copyLocalSymbols()
+void LinkEditOptimizer<A>::copyLazyBindInfo(uint32_t& offset)
 {
-       if ( fDynamicSymbolTable->nlocalsym() > 0 ) {
-               // if image has any local symbols, make cache look like it has one local symbol
-               // which is actually shared by all images
-               fLocalSymbolsCountInNewLinkEdit = 1; 
-               fLocalSymbolsStartIndexInNewLinkEdit = fgLocalSymbolsStartIndexInNewLinkEdit;
+       if ( (fDyldInfo != NULL) && (fDyldInfo->lazy_bind_off() != 0) ) {
+               fLazyBindInfoOffsetIntoNewLinkEdit = offset;
+               fLazyBindInfoSizeInNewLinkEdit = fDyldInfo->lazy_bind_size();
+               memcpy(fNewLinkEditStart+offset, &fLinkEditBase[fDyldInfo->lazy_bind_off()], fDyldInfo->lazy_bind_size());
+               offset += fDyldInfo->lazy_bind_size();
+       }
+}
+
+template <typename A>
+void LinkEditOptimizer<A>::copyExportInfo(uint32_t& offset)
+{
+       if ( (fDyldInfo != NULL) && (fLayout.getDyldInfoExports() != NULL) ) {
+               fExportInfoOffsetIntoNewLinkEdit = offset;
+               fExportInfoSizeInNewLinkEdit = fDyldInfo->export_size();
+               memcpy(fNewLinkEditStart+offset, fLayout.getDyldInfoExports(), fDyldInfo->export_size());
+               offset += fDyldInfo->export_size();
+       }
+}
+
+
+template <typename A>
+void LinkEditOptimizer<A>::copyLocalSymbols(uint32_t symbolTableOffset, uint32_t& symbolIndex, bool dontMapLocalSymbols, uint8_t* cacheStart, 
+                                                                                       StringPool&     unmappedLocalsStringPool, std::vector<macho_nlist<P> >& unmappedSymbols,
+                                                                                       std::vector<LocalSymbolInfo>& dylibInfos)
+{
+       fLocalSymbolsStartIndexInNewLinkEdit = symbolIndex;
+       LocalSymbolInfo localInfo;
+       localInfo.dylibOffset = ((uint8_t*)fHeader) - cacheStart;
+       localInfo.nlistStartIndex = unmappedSymbols.size();
+       localInfo.nlistCount = 0;
+       fSymbolTableStartOffsetInNewLinkEdit = symbolTableOffset + symbolIndex*sizeof(macho_nlist<P>);
+       macho_nlist<P>* const newSymbolTableStart = (macho_nlist<P>*)(fNewLinkEditStart+symbolTableOffset);
+       const macho_nlist<P>* const firstLocal = &fSymbolTable[fDynamicSymbolTable->ilocalsym()];
+       const macho_nlist<P>* const lastLocal  = &fSymbolTable[fDynamicSymbolTable->ilocalsym()+fDynamicSymbolTable->nlocalsym()];
+       uint32_t oldIndex = fDynamicSymbolTable->ilocalsym();
+       for (const macho_nlist<P>* entry = firstLocal; entry < lastLocal; ++entry, ++oldIndex) {
+               // <rdar://problem/12237639> don't copy stab symbols
+               if ( (entry->n_sect() != NO_SECT) && ((entry->n_type() & N_STAB) == 0) ) {
+                       const char* name = &fStrings[entry->n_strx()];
+                       macho_nlist<P>* newSymbolEntry = &newSymbolTableStart[symbolIndex];
+                       *newSymbolEntry = *entry;
+                       if ( dontMapLocalSymbols ) {
+                               // if local in __text, add <redacted> symbol name to shared cache so backtraces don't have bogus names
+                               if ( entry->n_sect() == 1 ) {
+                                       newSymbolEntry->set_n_strx(fNewStringPool.addUnique("<redacted>"));
+                                       ++symbolIndex;
+                               }
+                               // copy local symbol to unmmapped locals area
+                               unmappedSymbols.push_back(*entry);                      
+                               unmappedSymbols.back().set_n_strx(unmappedLocalsStringPool.addUnique(name));
+                       }
+                       else {
+                               newSymbolEntry->set_n_strx(fNewStringPool.addUnique(name));
+                               ++symbolIndex;
+                       }
+               }
        }
+       fLocalSymbolsCountInNewLinkEdit = symbolIndex - fLocalSymbolsStartIndexInNewLinkEdit;
+       localInfo.nlistCount = unmappedSymbols.size() - localInfo.nlistStartIndex;
+       dylibInfos.push_back(localInfo);
+       //fprintf(stderr, "%u locals starting at %u for %s\n", fLocalSymbolsCountInNewLinkEdit, fLocalSymbolsStartIndexInNewLinkEdit, fLayout.getFilePath());
 }
 
 
 template <typename A>
-void LinkEditOptimizer<A>::copyExportedSymbols(uint32_t& symbolIndex)
+void LinkEditOptimizer<A>::copyExportedSymbols(uint32_t symbolTableOffset, uint32_t& symbolIndex)
 {
        fExportedSymbolsStartIndexInNewLinkEdit = symbolIndex;
+       macho_nlist<P>* const newSymbolTableStart = (macho_nlist<P>*)(fNewLinkEditStart+symbolTableOffset);
        const macho_nlist<P>* const firstExport = &fSymbolTable[fDynamicSymbolTable->iextdefsym()];
        const macho_nlist<P>* const lastExport  = &fSymbolTable[fDynamicSymbolTable->iextdefsym()+fDynamicSymbolTable->nextdefsym()];
        uint32_t oldIndex = fDynamicSymbolTable->iextdefsym();
        for (const macho_nlist<P>* entry = firstExport; entry < lastExport; ++entry, ++oldIndex) {
-               if ( ((entry->n_type() & N_TYPE) == N_SECT) && (strncmp(&fStrings[entry->n_strx()], ".objc_", 6) != 0) ) {
-                       macho_nlist<P>* newSymbolEntry = &((macho_nlist<P>*)fNewLinkEditStart)[symbolIndex];
+               if ( ((entry->n_type() & N_TYPE) == N_SECT) && (strncmp(&fStrings[entry->n_strx()], ".objc_", 6) != 0)
+                                               && (strncmp(&fStrings[entry->n_strx()], "$ld$", 4) != 0) ) {
+                       macho_nlist<P>* newSymbolEntry = &newSymbolTableStart[symbolIndex];
                        *newSymbolEntry = *entry;
-                       newSymbolEntry->set_n_strx(fNewStringPool.add(&fStrings[entry->n_strx()]));
-                       fOldToNewSymbolIndexes[oldIndex] = symbolIndex;
+                       newSymbolEntry->set_n_strx(fNewStringPool.addUnique(&fStrings[entry->n_strx()]));
+                       fOldToNewSymbolIndexes[oldIndex] = symbolIndex-fLocalSymbolsStartIndexInNewLinkEdit;
                        ++symbolIndex;
                }
        }
        fExportedSymbolsCountInNewLinkEdit = symbolIndex - fExportedSymbolsStartIndexInNewLinkEdit;
        //fprintf(stderr, "%u exports starting at %u for %s\n", fExportedSymbolsCountInNewLinkEdit, fExportedSymbolsStartIndexInNewLinkEdit, fLayout.getFilePath());
        // sort by name, so that dyld does not need a toc
-       macho_nlist<P>* newSymbolsStart = &((macho_nlist<P>*)fNewLinkEditStart)[fExportedSymbolsStartIndexInNewLinkEdit];
-       macho_nlist<P>* newSymbolsEnd = &((macho_nlist<P>*)fNewLinkEditStart)[fExportedSymbolsStartIndexInNewLinkEdit+fExportedSymbolsCountInNewLinkEdit];
+       macho_nlist<P>* newSymbolsStart = &newSymbolTableStart[fExportedSymbolsStartIndexInNewLinkEdit];
+       macho_nlist<P>* newSymbolsEnd = &newSymbolTableStart[fExportedSymbolsStartIndexInNewLinkEdit+fExportedSymbolsCountInNewLinkEdit];
        std::sort(newSymbolsStart, newSymbolsEnd, SymbolSorter<A>(fNewStringPool));
        //for (macho_nlist<P>* entry = newSymbolsStart; entry < newSymbolsEnd; ++entry)
        //      fprintf(stderr, "\t%u\t %s\n", (entry-newSymbolsStart)+fExportedSymbolsStartIndexInNewLinkEdit, fNewStringPool.stringAtIndex(entry->n_strx()));
@@ -1003,18 +1679,19 @@ void LinkEditOptimizer<A>::copyExportedSymbols(uint32_t& symbolIndex)
 
 
 template <typename A>
-void LinkEditOptimizer<A>::copyImportedSymbols(uint32_t& symbolIndex)
+void LinkEditOptimizer<A>::copyImportedSymbols(uint32_t symbolTableOffset, uint32_t& symbolIndex)
 {
        fImportSymbolsStartIndexInNewLinkEdit = symbolIndex;
+       macho_nlist<P>* const newSymbolTableStart = (macho_nlist<P>*)(fNewLinkEditStart+symbolTableOffset);
        const macho_nlist<P>* const firstImport = &fSymbolTable[fDynamicSymbolTable->iundefsym()];
        const macho_nlist<P>* const lastImport  = &fSymbolTable[fDynamicSymbolTable->iundefsym()+fDynamicSymbolTable->nundefsym()];
        uint32_t oldIndex = fDynamicSymbolTable->iundefsym();
        for (const macho_nlist<P>* entry = firstImport; entry < lastImport; ++entry, ++oldIndex) {
                if ( ((entry->n_type() & N_TYPE) == N_UNDF) && (strncmp(&fStrings[entry->n_strx()], ".objc_", 6) != 0) ) {
-                       macho_nlist<P>* newSymbolEntry = &((macho_nlist<P>*)fNewLinkEditStart)[symbolIndex];
+                       macho_nlist<P>* newSymbolEntry = &newSymbolTableStart[symbolIndex];
                        *newSymbolEntry = *entry;
                        newSymbolEntry->set_n_strx(fNewStringPool.addUnique(&fStrings[entry->n_strx()]));
-                       fOldToNewSymbolIndexes[oldIndex] = symbolIndex;
+                       fOldToNewSymbolIndexes[oldIndex] = symbolIndex-fLocalSymbolsStartIndexInNewLinkEdit;
                        ++symbolIndex;
                }
        }
@@ -1044,6 +1721,27 @@ void LinkEditOptimizer<A>::copyExternalRelocations(uint32_t& offset)
        }
 }
 
+template <typename A>
+void LinkEditOptimizer<A>::copyFunctionStarts(uint32_t& offset)
+{      
+       if ( fFunctionStarts != NULL ) {
+               fFunctionStartsOffsetInNewLinkEdit = offset;
+               memcpy(&fNewLinkEditStart[offset], &fLinkEditBase[fFunctionStarts->dataoff()], fFunctionStarts->datasize());
+               offset += fFunctionStarts->datasize();
+       }
+}
+
+template <typename A>
+void LinkEditOptimizer<A>::copyDataInCode(uint32_t& offset)
+{      
+       if ( fDataInCode != NULL ) {
+               fDataInCodeOffsetInNewLinkEdit = offset;
+               memcpy(&fNewLinkEditStart[offset], &fLinkEditBase[fDataInCode->dataoff()], fDataInCode->datasize());
+               offset += fDataInCode->datasize();
+       }
+}
+
+
 template <typename A>
 void LinkEditOptimizer<A>::copyIndirectSymbolTable(uint32_t& offset)
 {      
@@ -1064,13 +1762,13 @@ void LinkEditOptimizer<A>::copyIndirectSymbolTable(uint32_t& offset)
 }
 
 template <typename A>
-void LinkEditOptimizer<A>::updateLoadCommands(uint64_t newVMAddress, uint64_t size, uint32_t stringPoolOffset)
+void LinkEditOptimizer<A>::updateLoadCommands(uint64_t newVMAddress, uint64_t size, uint32_t stringPoolOffset, 
+                                                                                               uint32_t linkEditsFileOffset, bool keepSignatures)
 {
        // set LINKEDIT segment commmand to new merged LINKEDIT
        const macho_load_command<P>* const cmds = (macho_load_command<P>*)((uint8_t*)fHeader + sizeof(macho_header<P>));
        const uint32_t cmd_count = fHeader->ncmds();
        const macho_load_command<P>* cmd = cmds;
-       uint32_t linkEditStartFileOffset = 0;
        for (uint32_t i = 0; i < cmd_count; ++i) {
                if ( cmd->cmd() == macho_segment_command<P>::CMD ) {
                        macho_segment_command<P>* seg = (macho_segment_command<P>*)cmd;
@@ -1078,37 +1776,118 @@ void LinkEditOptimizer<A>::updateLoadCommands(uint64_t newVMAddress, uint64_t si
                                seg->set_vmaddr(newVMAddress);
                                seg->set_vmsize(size);
                                seg->set_filesize(size);
-                               linkEditStartFileOffset = seg->fileoff();
+                               seg->set_fileoff(linkEditsFileOffset);
+                       }
+                       // don't alter __TEXT until <rdar://problem/7022345> is fixed
+                       else if ( strcmp(seg->segname(), "__TEXT") != 0 ) {
+                               // update all other segments fileoff to be offset from start of cache file
+                               pint_t oldFileOff = seg->fileoff();
+                               seg->set_fileoff(fSharedCache.cacheFileOffsetForVMAddress(seg->vmaddr()));
+                               pint_t fileOffsetDelta = seg->fileoff() - oldFileOff;
+                               // update all sections in this segment
+                               macho_section<P>* const sectionsStart = (macho_section<P>*)((char*)seg + sizeof(macho_segment_command<P>));
+                               macho_section<P>* const sectionsEnd = &sectionsStart[seg->nsects()];
+                               for(macho_section<P>* sect = sectionsStart; sect < sectionsEnd; ++sect) {
+                                       if ( sect->offset() != 0 )
+                                               sect->set_offset(sect->offset()+fileOffsetDelta);
+                               }
                        }
                }
                cmd = (const macho_load_command<P>*)(((uint8_t*)cmd)+cmd->cmdsize());
        }       
+       
+       // update dyld_info with new offsets
+       if ( fDyldInfo != NULL ) {
+               fDyldInfo->set_rebase_off(0);
+               fDyldInfo->set_rebase_size(0);
+               fDyldInfo->set_bind_off(linkEditsFileOffset+fBindInfoOffsetIntoNewLinkEdit);
+               fDyldInfo->set_bind_size(fBindInfoSizeInNewLinkEdit);
+               fDyldInfo->set_weak_bind_off(linkEditsFileOffset+fWeakBindInfoOffsetIntoNewLinkEdit);
+               fDyldInfo->set_weak_bind_size(fWeakBindInfoSizeInNewLinkEdit);
+               fDyldInfo->set_lazy_bind_off(linkEditsFileOffset+fLazyBindInfoOffsetIntoNewLinkEdit);
+               fDyldInfo->set_lazy_bind_size(fLazyBindInfoSizeInNewLinkEdit);
+               fDyldInfo->set_export_off(linkEditsFileOffset+fExportInfoOffsetIntoNewLinkEdit);
+               fDyldInfo->set_export_size(fExportInfoSizeInNewLinkEdit);
+               
+//             fprintf(stderr, "dylib %s\n", fLayout.getFilePath());
+//             fprintf(stderr, "  bind_off=0x%08X\n", fDyldInfo->bind_off());
+//             fprintf(stderr, "  export_off=0x%08X\n", fDyldInfo->export_off());
+//             fprintf(stderr, "  export_size=%d\n", fDyldInfo->export_size());
                
+       }       
+       
        // update symbol table and dynamic symbol table with new offsets
-       fSymbolTableLoadCommand->set_symoff(linkEditStartFileOffset);
-       fSymbolTableLoadCommand->set_nsyms(fExportedSymbolsCountInNewLinkEdit+fImportedSymbolsCountInNewLinkEdit);
-       fSymbolTableLoadCommand->set_stroff(linkEditStartFileOffset+stringPoolOffset);
+       fSymbolTableLoadCommand->set_symoff(linkEditsFileOffset+fSymbolTableStartOffsetInNewLinkEdit);
+       fSymbolTableLoadCommand->set_nsyms(fLocalSymbolsCountInNewLinkEdit+fExportedSymbolsCountInNewLinkEdit+fImportedSymbolsCountInNewLinkEdit);
+       fSymbolTableLoadCommand->set_stroff(linkEditsFileOffset+stringPoolOffset);
        fSymbolTableLoadCommand->set_strsize(fNewStringPool.size());
-       fDynamicSymbolTable->set_ilocalsym(fLocalSymbolsStartIndexInNewLinkEdit);
+       fDynamicSymbolTable->set_ilocalsym(0);
        fDynamicSymbolTable->set_nlocalsym(fLocalSymbolsCountInNewLinkEdit);
-       fDynamicSymbolTable->set_iextdefsym(fExportedSymbolsStartIndexInNewLinkEdit);
+       fDynamicSymbolTable->set_iextdefsym(fExportedSymbolsStartIndexInNewLinkEdit-fLocalSymbolsStartIndexInNewLinkEdit);
        fDynamicSymbolTable->set_nextdefsym(fExportedSymbolsCountInNewLinkEdit);
-       fDynamicSymbolTable->set_iundefsym(fImportSymbolsStartIndexInNewLinkEdit);
+       fDynamicSymbolTable->set_iundefsym(fImportSymbolsStartIndexInNewLinkEdit-fLocalSymbolsStartIndexInNewLinkEdit);
        fDynamicSymbolTable->set_nundefsym(fImportedSymbolsCountInNewLinkEdit);
        fDynamicSymbolTable->set_tocoff(0);
        fDynamicSymbolTable->set_ntoc(0);
        fDynamicSymbolTable->set_modtaboff(0);
        fDynamicSymbolTable->set_nmodtab(0);
-       fDynamicSymbolTable->set_indirectsymoff(linkEditStartFileOffset+fIndirectSymbolTableOffsetInfoNewLinkEdit);
-       fDynamicSymbolTable->set_extreloff(linkEditStartFileOffset+fExternalRelocationsOffsetIntoNewLinkEdit);
+       fDynamicSymbolTable->set_indirectsymoff(linkEditsFileOffset+fIndirectSymbolTableOffsetInfoNewLinkEdit);
+       fDynamicSymbolTable->set_extreloff(linkEditsFileOffset+fExternalRelocationsOffsetIntoNewLinkEdit);
        fDynamicSymbolTable->set_locreloff(0);
        fDynamicSymbolTable->set_nlocrel(0);
+
+       // update function starts
+       if ( fFunctionStarts != NULL ) {
+               fFunctionStarts->set_dataoff(linkEditsFileOffset+fFunctionStartsOffsetInNewLinkEdit);
+       }
+       // update data-in-code info
+       if ( fDataInCode != NULL ) {
+               fDataInCode->set_dataoff(linkEditsFileOffset+fDataInCodeOffsetInNewLinkEdit);
+       }
+       
+       // now remove load commands no longer needed
+       const macho_load_command<P>* srcCmd = cmds;
+       macho_load_command<P>* dstCmd = (macho_load_command<P>*)cmds;
+       int32_t newCount = 0;
+       for (uint32_t i = 0; i < cmd_count; ++i) {      
+               uint32_t cmdSize = srcCmd->cmdsize();
+               switch ( srcCmd->cmd() ) {
+                       case LC_SEGMENT_SPLIT_INFO:
+                       case LC_DYLIB_CODE_SIGN_DRS:
+                               // don't copy
+                               break;
+                       case LC_CODE_SIGNATURE:
+                               if ( !keepSignatures )
+                                       break;
+                               // otherwise fall into copy case
+                       default:
+                               memmove(dstCmd, srcCmd, cmdSize);
+                               dstCmd = (macho_load_command<P>*)(((uint8_t*)dstCmd)+cmdSize);
+                               ++newCount;
+                               break;
+               }
+               srcCmd = (const macho_load_command<P>*)(((uint8_t*)srcCmd)+cmdSize);
+       }
+       // zero out stuff removed
+       bzero(dstCmd, (uint8_t*)srcCmd - (uint8_t*)dstCmd);
+       
+       // update mach_header
+       macho_header<P>* writableHeader = (macho_header<P>*)fHeader; 
+       writableHeader->set_ncmds(newCount);
+       writableHeader->set_sizeofcmds((uint8_t*)dstCmd - ((uint8_t*)fHeader + sizeof(macho_header<P>)));
+       
+       // this invalidates some ivars
+       fDynamicSymbolTable = NULL;
+       fSymbolTableLoadCommand = NULL;
+       fDyldInfo = NULL;
+       fSymbolTable = NULL;
+       fStrings = NULL;
 }
 
 
 
 template <typename A>
-uint8_t* SharedCache<A>::optimizeLINKEDIT()
+uint8_t* SharedCache<A>::optimizeLINKEDIT(bool keepSignatures, bool dontMapLocalSymbols)
 {
        // allocate space for optimized LINKEDIT area
        uint8_t* newLinkEdit = new uint8_t[fLinkEditsTotalUnoptimizedSize];
@@ -1120,58 +1899,98 @@ uint8_t* SharedCache<A>::optimizeLINKEDIT()
        // create optimizer object for each LINKEDIT segment
        std::vector<LinkEditOptimizer<A>*> optimizers;
        for(typename std::vector<LayoutInfo>::const_iterator it = fDylibs.begin(); it != fDylibs.end(); ++it) {
-               optimizers.push_back(new LinkEditOptimizer<A>(*it->layout, newLinkEdit, stringPool));
+               optimizers.push_back(new LinkEditOptimizer<A>(*it->layout, *this, newLinkEdit, stringPool));
        }
 
-       // copy local symbol table entries
-       uint32_t symbolTableIndex = 0;
-       LinkEditOptimizer<A>::makeDummyLocalSymbol(symbolTableIndex, newLinkEdit, stringPool);
+       // rebase info is not copied because images in shared cache are never rebased
+       
+       // copy weak bind info
+       uint32_t offset = 0;
+       fOffsetOfWeakBindInfoInCombinedLinkedit = offset;
        for(typename std::vector<LinkEditOptimizer<A>*>::iterator it = optimizers.begin(); it != optimizers.end(); ++it) {
-               (*it)->copyLocalSymbols();
+               (*it)->copyWeakBindInfo(offset);
+       }
+       
+       // copy export info
+       fOffsetOfExportInfoInCombinedLinkedit = offset;
+       for(typename std::vector<LinkEditOptimizer<A>*>::iterator it = optimizers.begin(); it != optimizers.end(); ++it) {
+               (*it)->copyExportInfo(offset);
        }
 
-       // copy exported symbol table entries
+       // copy bind info
+       fOffsetOfBindInfoInCombinedLinkedit = offset;
        for(typename std::vector<LinkEditOptimizer<A>*>::iterator it = optimizers.begin(); it != optimizers.end(); ++it) {
-               (*it)->copyExportedSymbols(symbolTableIndex);
+               (*it)->copyBindInfo(offset);
        }
-       //fprintf(stderr, "%u exported symbols, with %d bytes of strings\n", symbolTableIndex, stringPool.size());
-       //uint32_t importStart = symbolTableIndex;
-       //uint32_t importPoolStart =  stringPool.size();
        
-       // copy imported symbol table entries
+       // copy lazy bind info
+       fOffsetOfLazyBindInfoInCombinedLinkedit = offset;
+       for(typename std::vector<LinkEditOptimizer<A>*>::iterator it = optimizers.begin(); it != optimizers.end(); ++it) {
+               (*it)->copyLazyBindInfo(offset);
+       }
+
+       // copy symbol table entries
+       fOffsetOfOldSymbolTableInfoInCombinedLinkedit = offset;
+       uint32_t symbolTableOffset = offset;
+       uint32_t symbolTableIndex = 0;
+       if ( dontMapLocalSymbols ) 
+               fUnmappedLocalSymbols.reserve(16384);
        for(typename std::vector<LinkEditOptimizer<A>*>::iterator it = optimizers.begin(); it != optimizers.end(); ++it) {
-               (*it)->copyImportedSymbols(symbolTableIndex);
+               (*it)->copyLocalSymbols(symbolTableOffset, symbolTableIndex, dontMapLocalSymbols, fInMemoryCache,
+                                                               fUnmappedLocalsStringPool, fUnmappedLocalSymbols, fLocalSymbolInfos);
+               (*it)->copyExportedSymbols(symbolTableOffset, symbolTableIndex);
+               (*it)->copyImportedSymbols(symbolTableOffset, symbolTableIndex);
        }
-       //fprintf(stderr, "%u imported symbols, with %d bytes of strings\n", symbolTableIndex-importStart, stringPool.size()-importPoolStart);
+       fSizeOfOldSymbolTableInfoInCombinedLinkedit =  symbolTableIndex * sizeof(macho_nlist<typename A::P>);
+       offset = symbolTableOffset + fSizeOfOldSymbolTableInfoInCombinedLinkedit & (-8);
        
        // copy external relocations, 8-byte aligned after end of symbol table
-       uint32_t externalRelocsOffset = (symbolTableIndex * sizeof(macho_nlist<typename A::P>) + 7) & (-8);
-       //uint32_t externalRelocsStartOffset = externalRelocsOffset;
+       fOffsetOfOldExternalRelocationsInCombinedLinkedit = offset;
        for(typename std::vector<LinkEditOptimizer<A>*>::iterator it = optimizers.begin(); it != optimizers.end(); ++it) {
-               (*it)->copyExternalRelocations(externalRelocsOffset);
+               (*it)->copyExternalRelocations(offset);
        }
-       //fprintf(stderr, "%u bytes of external relocs\n", externalRelocsOffset-externalRelocsStartOffset);
+       fSizeOfOldExternalRelocationsInCombinedLinkedit = offset - fOffsetOfOldExternalRelocationsInCombinedLinkedit;
        
+       // copy function starts
+       fOffsetOfFunctionStartsInCombinedLinkedit = offset;
+       for(typename std::vector<LinkEditOptimizer<A>*>::iterator it = optimizers.begin(); it != optimizers.end(); ++it) {
+               (*it)->copyFunctionStarts(offset);
+       }
+       fSizeOfFunctionStartsInCombinedLinkedit = offset - fOffsetOfFunctionStartsInCombinedLinkedit;
+
+       // copy data-in-code info
+       fOffsetOfDataInCodeInCombinedLinkedit = offset;
+       for(typename std::vector<LinkEditOptimizer<A>*>::iterator it = optimizers.begin(); it != optimizers.end(); ++it) {
+               (*it)->copyDataInCode(offset);
+       }
+       fSizeOfDataInCodeInCombinedLinkedit = offset - fOffsetOfDataInCodeInCombinedLinkedit;
+
        // copy indirect symbol tables
-       uint32_t indirectSymbolTableOffset = externalRelocsOffset;
+       fOffsetOfOldIndirectSymbolsInCombinedLinkedit = offset;
        for(typename std::vector<LinkEditOptimizer<A>*>::iterator it = optimizers.begin(); it != optimizers.end(); ++it) {
-               (*it)->copyIndirectSymbolTable(indirectSymbolTableOffset);
+               (*it)->copyIndirectSymbolTable(offset);
        }
-       
+       fSizeOfOldIndirectSymbolsInCombinedLinkedit = offset - fOffsetOfOldIndirectSymbolsInCombinedLinkedit;
+               
        // copy string pool
-       uint32_t stringPoolOffset = indirectSymbolTableOffset;
-       memcpy(&newLinkEdit[stringPoolOffset], stringPool.getBuffer(), stringPool.size());
+       fOffsetOfOldStringPoolInCombinedLinkedit = offset;
+       memcpy(&newLinkEdit[offset], stringPool.getBuffer(), stringPool.size());
+       fSizeOfOldStringPoolInCombinedLinkedit = stringPool.size();
        
-       // find new size
-       uint32_t linkEditsTotalOptimizedSize = (stringPoolOffset + stringPool.size() + 4095) & (-4096);
+       // total new size round up to page size
+       fLinkEditsTotalOptimizedSize = pageAlign(fOffsetOfOldStringPoolInCombinedLinkedit + fSizeOfOldStringPoolInCombinedLinkedit);
        
+       // choose new linkedit file offset 
+       uint32_t linkEditsFileOffset = cacheFileOffsetForVMAddress(fLinkEditsStartAddress);
+//     uint32_t linkEditsFileOffset = fLinkEditsStartAddress - sharedRegionStartAddress();     
+
        // update load commands so that all dylibs shared different areas of the same LINKEDIT segment
        for(typename std::vector<LinkEditOptimizer<A>*>::iterator it = optimizers.begin(); it != optimizers.end(); ++it) {
-               (*it)->updateLoadCommands(fLinkEditsStartAddress, fLinkEditsTotalUnoptimizedSize, stringPoolOffset);
+               (*it)->updateLoadCommands(fLinkEditsStartAddress, fLinkEditsTotalUnoptimizedSize, fOffsetOfOldStringPoolInCombinedLinkedit, linkEditsFileOffset, keepSignatures);
        }
 
-       //fprintf(stderr, "fLinkEditsTotalUnoptimizedSize=%llu, linkEditsTotalOptimizedSize=%u\n", fLinkEditsTotalUnoptimizedSize, linkEditsTotalOptimizedSize);
-       //fprintf(stderr, "mega link edit mapped starting at: %p\n", fFirstLinkEditSegment->mappedAddress());
+       //fprintf(stderr, "fLinkEditsTotalUnoptimizedSize=%llu, fLinkEditsTotalOptimizedSize=%u\n", fLinkEditsTotalUnoptimizedSize, fLinkEditsTotalOptimizedSize);
+       //printf(stderr, "mega link edit mapped starting at: %p\n", fFirstLinkEditSegment->mappedAddress());
 
        // overwrite mapped LINKEDIT area with new optimized LINKEDIT segment
        memcpy(fFirstLinkEditSegment->mappedAddress(), newLinkEdit, fLinkEditsTotalUnoptimizedSize);
@@ -1184,15 +2003,322 @@ uint8_t* SharedCache<A>::optimizeLINKEDIT()
                        if ( !seg.writable() && !seg.executable() && (strcmp(seg.name(), "__LINKEDIT") == 0) ) {
                                seg.setNewAddress(fLinkEditsStartAddress);
                                seg.setMappedAddress(fFirstLinkEditSegment->mappedAddress());
-                               seg.setSize(linkEditsTotalOptimizedSize);
-                               seg.setFileSize(linkEditsTotalOptimizedSize);
-                               //seg.setFileOffset(0);
+                               seg.setSize(fLinkEditsTotalOptimizedSize);
+                               seg.setFileSize(fLinkEditsTotalOptimizedSize);
+                               seg.setFileOffset(linkEditsFileOffset);
                        }
                }
        }
        
        // return new end of cache
-       return (uint8_t*)fFirstLinkEditSegment->mappedAddress() + linkEditsTotalOptimizedSize;
+       return (uint8_t*)fFirstLinkEditSegment->mappedAddress() + fLinkEditsTotalOptimizedSize;
+}
+
+
+template <typename A>
+class ObjCSelectorUniquer
+{
+private:
+    objc_opt::string_map fSelectorStrings;
+    SharedCache<A> *fCache;
+    size_t fCount;
+
+public:
+
+    ObjCSelectorUniquer(SharedCache<A> *newCache)
+        : fSelectorStrings()
+        , fCache(newCache)
+        , fCount(0)
+    { }
+
+    typename A::P::uint_t visit(typename A::P::uint_t oldValue) 
+    {
+        fCount++;
+        const char *s = (const char *)
+            fCache->mappedAddressForVMAddress(oldValue);
+        objc_opt::string_map::iterator element = 
+            fSelectorStrings.insert(objc_opt::string_map::value_type(s, oldValue)).first;
+        return (typename A::P::uint_t)element->second;
+    }
+
+    objc_opt::string_map& strings() { 
+        return fSelectorStrings;
+    }
+
+    size_t count() const { return fCount; }
+};
+
+
+template <typename A>
+class ClassListBuilder
+{
+private:
+    typedef typename A::P P;
+
+    objc_opt::string_map fClassNames;
+    objc_opt::class_map fClasses;
+    size_t fCount;
+    HeaderInfoOptimizer<A>& fHinfos;
+
+public:
+
+    ClassListBuilder(HeaderInfoOptimizer<A>& hinfos)
+        : fClassNames()
+        , fClasses()
+        , fCount(0)
+        , fHinfos(hinfos)
+    { }
+
+    void visitClass(SharedCache<A>* cache, 
+                    const macho_header<P>* header,
+                    objc_class_t<A>* cls) 
+    {
+        if (cls->isMetaClass(cache)) return;
+
+        const char *name = cls->getName(cache);
+        uint64_t name_vmaddr = cache->VMAddressForMappedAddress(name);
+        uint64_t cls_vmaddr = cache->VMAddressForMappedAddress(cls);
+        uint64_t hinfo_vmaddr = cache->VMAddressForMappedAddress(fHinfos.hinfoForHeader(cache, header));
+        fClassNames.insert(objc_opt::string_map::value_type(name, name_vmaddr));
+        fClasses.insert(objc_opt::class_map::value_type(name, std::pair<uint64_t, uint64_t>(cls_vmaddr, hinfo_vmaddr)));
+        fCount++;
+    }
+
+    objc_opt::string_map& classNames() { 
+        return fClassNames;
+    }
+
+    objc_opt::class_map& classes() { 
+        return fClasses;
+    }
+
+    size_t count() const { return fCount; }
+};
+
+
+static int percent(size_t num, size_t denom) {
+    if (denom) return (int)(num / (double)denom * 100);
+    else return 100;
+}
+
+template <typename A>
+void SharedCache<A>::optimizeObjC(std::vector<void*>& pointersInData)
+{
+    const char *err;
+
+    if ( verbose ) {
+        fprintf(stderr, "update_dyld_shared_cache: for %s, optimizing objc metadata\n", archName());
+    }
+
+    size_t headerSize = P::round_up(sizeof(objc_opt::objc_opt_t));
+    if (headerSize != sizeof(objc_opt::objc_opt_t)) {
+               warn(archName(), "libobjc's optimization structure size is wrong (metadata not optimized)");
+    }
+
+    // Find libobjc's empty sections to fill in
+    const macho_section<P> *optROSection = NULL;
+    const macho_section<P> *optRWSection = NULL;
+       for(typename std::vector<LayoutInfo>::const_iterator it = fDylibs.begin(); it != fDylibs.end(); ++it) {
+        if ( strstr(it->layout->getFilePath(), "libobjc") != NULL ) {
+                       const macho_header<P>* mh = (const macho_header<P>*)(*it->layout).getSegments()[0].mappedAddress();
+                       optROSection = mh->getSection("__TEXT", "__objc_opt_ro");
+                       optRWSection = mh->getSection("__DATA", "__objc_opt_rw");
+                       break;
+               }
+       }
+    
+       if ( optROSection == NULL ) {
+               warn(archName(), "libobjc's read-only section missing (metadata not optimized)");
+               return;
+       }
+       
+       if ( optRWSection == NULL ) {
+               warn(archName(), "libobjc's read/write section missing (metadata not optimized)");
+               return;
+       }
+
+       uint8_t* optROData = (uint8_t*)mappedAddressForVMAddress(optROSection->addr());
+    size_t optRORemaining = optROSection->size();
+
+       uint8_t* optRWData = (uint8_t*)mappedAddressForVMAddress(optRWSection->addr());
+    size_t optRWRemaining = optRWSection->size();
+       
+       if (optRORemaining < headerSize) {
+               warn(archName(), "libobjc's read-only section is too small (metadata not optimized)");
+               return;
+       }
+       objc_opt::objc_opt_t* optROHeader = (objc_opt::objc_opt_t *)optROData;
+    optROData += headerSize;
+    optRORemaining -= headerSize;
+
+       if (E::get32(optROHeader->version) != objc_opt::VERSION) {
+               warn(archName(), "libobjc's read-only section version is unrecognized (metadata not optimized)");
+               return;
+       }
+
+    // Write nothing to optROHeader until everything else is written.
+    // If something fails below, libobjc will not use the section.
+
+    // Find objc-containing dylibs
+    std::vector<LayoutInfo> objcDylibs;
+    for(typename std::vector<LayoutInfo>::const_iterator it = fDylibs.begin(); it != fDylibs.end(); ++it) {
+        macho_header<P> *mh = (macho_header<P>*)(*it->layout).getSegments()[0].mappedAddress();
+        if (mh->getSection("__DATA", "__objc_imageinfo")  ||  mh->getSegment("__OBJC")) {
+            objcDylibs.push_back(*it);
+        }
+    }
+
+    // Build image list
+
+    // This is SAFE: the binaries themselves are unmodified.
+
+    std::vector<LayoutInfo> addressSortedDylibs = objcDylibs;
+    std::sort(addressSortedDylibs.begin(), addressSortedDylibs.end(), ByAddressSorter());
+
+    uint64_t hinfoVMAddr = optRWSection->addr() + optRWSection->size() - optRWRemaining;
+    HeaderInfoOptimizer<A> hinfoOptimizer;
+    err = hinfoOptimizer.init(objcDylibs.size(), optRWData, optRWRemaining);
+    if (err) {
+               warn(archName(), err);
+               return;
+    }
+    for(typename std::vector<LayoutInfo>::const_iterator it = addressSortedDylibs.begin(); it != addressSortedDylibs.end(); ++it) {
+        const macho_header<P> *mh = (const macho_header<P>*)(*it->layout).getSegments()[0].mappedAddress();
+        hinfoOptimizer.update(this, mh, pointersInData);
+    }
+
+
+    // Update selector references and build selector list
+
+    // This is SAFE: if we run out of room for the selector table, 
+    // the modified binaries are still usable.
+
+    // Heuristic: choose selectors from libraries with more cstring data first.
+    // This tries to localize selector cstring memory.
+    ObjCSelectorUniquer<A> uniq(this);
+    std::vector<LayoutInfo> sizeSortedDylibs = objcDylibs;
+    std::sort(sizeSortedDylibs.begin(), sizeSortedDylibs.end(), ByCStringSectionSizeSorter());
+
+    SelectorOptimizer<A, ObjCSelectorUniquer<A> > selOptimizer(uniq);
+       for(typename std::vector<LayoutInfo>::const_iterator it = sizeSortedDylibs.begin(); it != sizeSortedDylibs.end(); ++it) {
+        const macho_header<P> *mh = (const macho_header<P>*)(*it->layout).getSegments()[0].mappedAddress();
+        LegacySelectorUpdater<A, ObjCSelectorUniquer<A> >::update(this, mh, uniq);
+        selOptimizer.optimize(this, mh);
+       }
+
+    uint64_t seloptVMAddr = optROSection->addr() + optROSection->size() - optRORemaining;
+    objc_opt::objc_selopt_t *selopt = new(optROData) objc_opt::objc_selopt_t;
+    err = selopt->write(seloptVMAddr, optRORemaining, uniq.strings());
+    if (err) {
+        warn(archName(), err);
+        return;
+    }
+    optROData += selopt->size();
+    optRORemaining -= selopt->size();
+    selopt->byteswap(E::little_endian), selopt = NULL;
+
+
+    // Build class table.
+
+    // This is SAFE: the binaries themselves are unmodified.
+
+    ClassListBuilder<A> classes(hinfoOptimizer);
+    ClassWalker< A, ClassListBuilder<A> > classWalker(classes);
+       for(typename std::vector<LayoutInfo>::const_iterator it = sizeSortedDylibs.begin(); it != sizeSortedDylibs.end(); ++it) {
+        const macho_header<P> *mh = (const macho_header<P>*)(*it->layout).getSegments()[0].mappedAddress();
+        classWalker.walk(this, mh);
+       }
+
+    uint64_t clsoptVMAddr = optROSection->addr() + optROSection->size() - optRORemaining;
+    objc_opt::objc_clsopt_t *clsopt = new(optROData) objc_opt::objc_clsopt_t;
+    err = clsopt->write(clsoptVMAddr, optRORemaining, 
+                        classes.classNames(), classes.classes(), verbose);
+    if (err) {
+        warn(archName(), err);
+        return;
+    }
+    optROData += clsopt->size();
+    optRORemaining -= clsopt->size();
+    size_t duplicateCount = clsopt->duplicateCount();
+    clsopt->byteswap(E::little_endian), clsopt = NULL;
+
+
+    // Sort method lists.
+
+    // This is SAFE: modified binaries are still usable as unsorted lists.
+    // This must be done AFTER uniquing selectors.
+
+    MethodListSorter<A> methodSorter;
+    for(typename std::vector<LayoutInfo>::const_iterator it = sizeSortedDylibs.begin(); it != sizeSortedDylibs.end(); ++it) {
+        macho_header<P> *mh = (macho_header<P>*)(*it->layout).getSegments()[0].mappedAddress();
+        methodSorter.optimize(this, mh);
+    }
+
+
+    // Repair ivar offsets.
+
+    // This is SAFE: the runtime always validates ivar offsets at runtime.
+
+    IvarOffsetOptimizer<A> ivarOffsetOptimizer;
+       for(typename std::vector<LayoutInfo>::const_iterator it = sizeSortedDylibs.begin(); it != sizeSortedDylibs.end(); ++it) {
+        const macho_header<P> *mh = (const macho_header<P>*)(*it->layout).getSegments()[0].mappedAddress();
+        ivarOffsetOptimizer.optimize(this, mh);
+       }
+    
+
+    // Success. Mark dylibs as optimized.
+       for(typename std::vector<LayoutInfo>::const_iterator it = sizeSortedDylibs.begin(); it != sizeSortedDylibs.end(); ++it) {
+        const macho_header<P> *mh = (const macho_header<P>*)(*it->layout).getSegments()[0].mappedAddress();
+        const macho_section<P> *imageInfoSection;
+        imageInfoSection = mh->getSection("__DATA", "__objc_imageinfo");
+        if (!imageInfoSection) {
+            imageInfoSection = mh->getSection("__OBJC", "__image_info");
+        }
+        if (imageInfoSection) {
+            objc_image_info<A> *info = (objc_image_info<A> *)
+                mappedAddressForVMAddress(imageInfoSection->addr());
+            info->setOptimizedByDyld();
+        }
+    }
+
+
+    // Success. Update RO header last.
+    E::set32(optROHeader->selopt_offset, seloptVMAddr - optROSection->addr());
+    E::set32(optROHeader->clsopt_offset, clsoptVMAddr - optROSection->addr());
+    E::set32(optROHeader->headeropt_offset, hinfoVMAddr - optROSection->addr());
+
+    if ( verbose ) {
+        size_t roSize = optROSection->size() - optRORemaining;
+        size_t rwSize = optRWSection->size() - optRWRemaining;
+        fprintf(stderr, "update_dyld_shared_cache: for %s, %zu/%llu bytes "
+                "(%d%%) used in libobjc read-only optimization section\n", 
+                archName(), roSize, optROSection->size(), 
+                percent(roSize, optROSection->size()));
+        fprintf(stderr, "update_dyld_shared_cache: for %s, %zu/%llu bytes "
+                "(%d%%) used in libobjc read/write optimization section\n", 
+                archName(), rwSize, optRWSection->size(), 
+                percent(rwSize, optRWSection->size()));
+        fprintf(stderr, "update_dyld_shared_cache: for %s, "
+                "uniqued %zu selectors\n", 
+                archName(), uniq.strings().size());
+        fprintf(stderr, "update_dyld_shared_cache: for %s, "
+                "updated %zu selector references\n", 
+                archName(), uniq.count());
+        fprintf(stderr, "update_dyld_shared_cache: for %s, "
+                "updated %zu ivar offsets\n", 
+                archName(), ivarOffsetOptimizer.optimized());
+        fprintf(stderr, "update_dyld_shared_cache: for %s, "
+                "sorted %zu method lists\n", 
+                archName(), methodSorter.optimized());
+        fprintf(stderr, "update_dyld_shared_cache: for %s, "
+                "recorded %zu classes (%zu duplicates)\n", 
+                archName(), classes.classNames().size(), duplicateCount);
+        fprintf(stderr, "update_dyld_shared_cache: for %s, "
+                "wrote objc metadata optimization version %d\n", 
+                archName(), objc_opt::VERSION);
+    }
+
+    return;
 }
 
 
@@ -1209,20 +2335,86 @@ static void cleanup(int sig)
 }
 
 
+// <rdar://problem/10730767> update_dyld_shared_cache should use sync_volume_np() instead of sync() 
+static void sync_volume(const char* volumePath)
+{
+#if __MAC_OS_X_VERSION_MIN_REQUIRED >= 1080
+       int error = sync_volume_np(volumePath, SYNC_VOLUME_FULLSYNC|SYNC_VOLUME_FULLSYNC);
+#else
+       int full_sync = 3; // SYNC_VOLUME_FULLSYNC | SYNC_VOLUME_FULLSYNC
+       int error = 0;
+       if ( fsctl(volumePath, 0x80004101 /*FSCTL_SYNC_VOLUME*/, &full_sync, 0) == -1) 
+               error = errno;
+#endif
+       if ( error )
+               ::sync();
+}
+
+
+// <rdar://problem/12552226> update shared cache should sign the shared cache
+static bool adhoc_codesign_share_cache(const char* path)
+{
+       CFURLRef target = ::CFURLCreateFromFileSystemRepresentation(NULL, (const UInt8 *)path, strlen(path), FALSE);
+       if ( target == NULL )
+               return false;
+
+       SecStaticCodeRef code;
+       OSStatus status = ::SecStaticCodeCreateWithPath(target, kSecCSDefaultFlags, &code);
+       CFRelease(target);
+       if ( status ) {
+               ::fprintf(stderr, "codesign: failed to create url to signed object\n");
+               return false;
+       }
+
+       const void * keys[1] = { (void *)kSecCodeSignerIdentity } ;
+       const void * values[1] = { (void *)kCFNull };
+       CFDictionaryRef params = ::CFDictionaryCreate(NULL, keys, values, 1, &kCFTypeDictionaryKeyCallBacks, &kCFTypeDictionaryValueCallBacks);
+       if ( params == NULL ) {
+               CFRelease(code);
+               return false;
+       }
+       
+       SecCodeSignerRef signer;
+       status = ::SecCodeSignerCreate(params, kSecCSDefaultFlags, &signer);
+       CFRelease(params);
+       if ( status ) {
+               CFRelease(code);
+               ::fprintf(stderr, "codesign: failed to create signer object\n");
+               return false;
+       }
+
+       status = ::SecCodeSignerAddSignatureWithErrors(signer, code, kSecCSDefaultFlags, NULL);
+       CFRelease(code);
+       CFRelease(signer);
+       if ( status ) {
+               ::fprintf(stderr, "codesign: failed to sign object: %s\n", path);
+               return false;
+       }
+
+       if ( verbose )
+               ::fprintf(stderr, "codesigning complete of %s\n", path);
+       
+       return true;
+}
+
+
+
+template <>     bool   SharedCache<x86_64>::addCacheSlideInfo(){ return true; }
+template <>     bool   SharedCache<arm>::addCacheSlideInfo()   { return true; }
+template <>     bool   SharedCache<x86>::addCacheSlideInfo()   { return false; }
+
+
+
 template <typename A>
-bool SharedCache<A>::update(const char* rootPath, const char* cacheDir, bool force, bool optimize, bool deleteExistingFirst, int archIndex, int archCount)
+bool SharedCache<A>::update(bool force, bool optimize, bool deleteExistingFirst, int archIndex,
+                                                               int archCount, bool keepSignatures, bool dontMapLocalSymbols)
 {
        bool didUpdate = false;
-       char cachePath[1024];
-       strcpy(cachePath, rootPath);
-       strcat(cachePath, cacheDir);
-       strcat(cachePath, DYLD_SHARED_CACHE_BASE_NAME);
-       strcat(cachePath, filename(optimize));
        
        // already up to date?
-       if ( force || this->notUpToDate(cachePath) ) {
+       if ( force || fExistingIsNotUpToDate ) {
                if ( verbose )
-                       fprintf(stderr, "update_dyld_shared_cache: regenerating %s\n", cachePath);
+                       fprintf(stderr, "update_dyld_shared_cache: regenerating %s\n", fCacheFilePath);
                if ( fDylibs.size() == 0 ) {
                        fprintf(stderr, "update_dyld_shared_cache: warning, empty cache not generated for arch %s\n", archName());
                        return false;
@@ -1230,37 +2422,43 @@ bool SharedCache<A>::update(const char* rootPath, const char* cacheDir, bool for
                // delete existing cache while building the new one
                // this is a flag to dyld to stop pinging update_dyld_shared_cache
                if ( deleteExistingFirst )
-                       ::unlink(cachePath);
+                       ::unlink(fCacheFilePath);
                uint8_t* inMemoryCache = NULL;
                uint32_t allocatedCacheSize = 0;
-               char tempCachePath[strlen(cachePath)+16];
-               sprintf(tempCachePath, "%s.tmp%u", cachePath, getpid());
+               char tempCachePath[strlen(fCacheFilePath)+16];
+               sprintf(tempCachePath, "%s.tmp%u", fCacheFilePath, getpid());
                try {
                        // allocate a memory block to hold cache
                        uint32_t cacheFileSize = 0;
                        for(std::vector<shared_file_mapping_np>::iterator it = fMappings.begin(); it != fMappings.end(); ++it) {
                                uint32_t end = it->sfm_file_offset + it->sfm_size;
-                               if ( end > cacheFileSize )
+                               if ( end > cacheFileSize ) 
                                        cacheFileSize = end;
                        }
                        if ( vm_allocate(mach_task_self(), (vm_address_t*)(&inMemoryCache), cacheFileSize, VM_FLAGS_ANYWHERE) != KERN_SUCCESS )
                                throwf("can't vm_allocate cache of size %u", cacheFileSize);
                        allocatedCacheSize = cacheFileSize;
+            fInMemoryCache = inMemoryCache;
                        
                        // fill in header
                        dyldCacheHeader<E>* header = (dyldCacheHeader<E>*)inMemoryCache;
+                       const char* archPairName = fArchGraph->archName();
                        char temp[16];
                        strcpy(temp, "dyld_v1        ");
-                       strcpy(&temp[15-strlen(archName())], archName());
+                       strcpy(&temp[15-strlen(archPairName)], archPairName);
                        header->set_magic(temp);
                        //header->set_architecture(arch());
                        header->set_mappingOffset(sizeof(dyldCacheHeader<E>)); 
                        header->set_mappingCount(fMappings.size());
                        header->set_imagesOffset(header->mappingOffset() + fMappings.size()*sizeof(dyldCacheFileMapping<E>));   
-                       header->set_imagesCount(fDylibs.size());
+                       header->set_imagesCount(fDylibs.size()+fDylibAliases.size());
                        header->set_dyldBaseAddress(fDyldBaseAddress);
-                       //header->set_dependenciesOffset(sizeof(dyldCacheHeader<E>) + fMappings.size()*sizeof(dyldCacheFileMapping<E>) + fDylibs.size()*sizeof(dyldCacheImageInfo<E>)); 
-                       //header->set_dependenciesCount(fDependencyPool.size());
+                       header->set_codeSignatureOffset(cacheFileSize);
+                       header->set_codeSignatureSize(0);
+                       header->set_slideInfoOffset(0);
+                       header->set_slideInfoSize(0);
+                       header->set_localSymbolsOffset(0);
+                       header->set_localSymbolsSize(0);
                        
                        // fill in mappings
                        dyldCacheFileMapping<E>* mapping = (dyldCacheFileMapping<E>*)&inMemoryCache[sizeof(dyldCacheHeader<E>)];
@@ -1282,23 +2480,41 @@ bool SharedCache<A>::update(const char* rootPath, const char* cacheDir, bool for
                                image->set_address(it->info.address);
                                image->set_modTime(it->info.modTime);
                                image->set_inode(it->info.inode);
-                               image->set_pathFileOffset(cacheFileOffsetForAddress(it->info.address+it->info.pathFileOffset));
-                               //image->set_dependenciesStartOffset(it->info.dependenciesStartOffset);
+                               image->set_pathFileOffset(cacheFileOffsetForVMAddress(it->info.address+it->info.pathFileOffset));
+                               ++image;
+                       }
+                       
+                       // add aliases to end of image table
+                       for(typename std::vector<LayoutInfo>::iterator it = fDylibAliases.begin(); it != fDylibAliases.end(); ++it) {
+                               image->set_address(it->info.address);
+                               image->set_modTime(it->info.modTime);
+                               image->set_inode(it->info.inode);
+                               image->set_pathFileOffset(it->info.pathFileOffset);
+                               strcpy((char*)inMemoryCache+it->info.pathFileOffset, it->aliases[0]);
+                               //fprintf(stderr, "adding alias to offset 0x%08X %s\n", it->info.pathFileOffset, it->aliases[0]);
                                ++image;
                        }
                                                
                        // copy each segment to cache buffer
+                       const int dylibCount = fDylibs.size();
                        int dylibIndex = 0;
+                       int progressIndex = 0;
                        for(typename std::vector<LayoutInfo>::const_iterator it = fDylibs.begin(); it != fDylibs.end(); ++it, ++dylibIndex) {
                                const char* path = it->layout->getFilePath();
-                               int src = ::open(path, O_RDONLY, 0);    
+                               int src = ::open(path, O_RDONLY, 0);
                                if ( src == -1 )
                                        throwf("can't open file %s, errnor=%d", it->layout->getID().name, errno);
                                // mark source as "don't cache"
                                (void)fcntl(src, F_NOCACHE, 1);
+                               // verify file has not changed since dependency analysis
+                               struct stat stat_buf;
+                               if ( fstat(src, &stat_buf) == -1)
+                                       throwf("can't stat open file %s, errno=%d", path, errno);
+                               if ( (it->layout->getInode() != stat_buf.st_ino) || (it->layout->getLastModTime() != stat_buf.st_mtime) )
+                                       throwf("file modified during cache creation: %s", path);
 
                                if ( verbose )
-                                       fprintf(stderr, "update_dyld_shared_cache: copying %s to cache\n", it->layout->getID().name);
+                                       fprintf(stderr, "update_dyld_shared_cache: copying %s to cache\n", it->layout->getFilePath());
                                try {
                                        const std::vector<MachOLayoutAbstraction::Segment>& segs = it->layout->getSegments();
                                        for (int i=0; i < segs.size(); ++i) {
@@ -1308,9 +2524,15 @@ bool SharedCache<A>::update(const char* rootPath, const char* cacheDir, bool for
                                                if ( seg.size() > 0 ) {
                                                        const uint64_t segmentSrcStartOffset = it->layout->getOffsetInUniversalFile()+seg.fileOffset();
                                                        const uint64_t segmentSize = seg.fileSize();
-                                                       const uint64_t segmentDstStartOffset = cacheFileOffsetForAddress(seg.newAddress());
-                                                       if ( ::pread(src, &inMemoryCache[segmentDstStartOffset], segmentSize, segmentSrcStartOffset) != segmentSize )
-                                                               throwf("read failure copying dylib errno=%d for %s", errno, it->layout->getID().name);
+                                                       const uint64_t segmentDstStartOffset = cacheFileOffsetForVMAddress(seg.newAddress());
+                                                       ssize_t readResult = ::pread(src, &inMemoryCache[segmentDstStartOffset], segmentSize, segmentSrcStartOffset);
+                                                       if ( readResult != segmentSize ) {
+                                                               if ( readResult == -1 )
+                                                                       throwf("read failure copying dylib errno=%d for %s", errno, it->layout->getID().name);
+                                                               else
+                                                                       throwf("read failure copying dylib. Read of %lld bytes at file offset %lld returned %ld for %s", 
+                                                                                       segmentSize, segmentSrcStartOffset, readResult, it->layout->getID().name);
+                                                       }
                                                }
                                        }
                                }
@@ -1318,6 +2540,13 @@ bool SharedCache<A>::update(const char* rootPath, const char* cacheDir, bool for
                                        throwf("%s while copying %s to shared cache", msg, it->layout->getID().name);
                                }
                                ::close(src);
+                               if ( progress ) {
+                                       // assuming read takes 40% of time
+                                       int nextProgressIndex = archIndex*100+(40*dylibIndex)/dylibCount;
+                                       if ( nextProgressIndex != progressIndex )
+                                               fprintf(stdout, "%3u/%u\n", nextProgressIndex, archCount*100);
+                                       progressIndex = nextProgressIndex;
+                               }
                        }
                                                
                        // set mapped address for each segment
@@ -1326,16 +2555,20 @@ bool SharedCache<A>::update(const char* rootPath, const char* cacheDir, bool for
                                for (int i=0; i < segs.size(); ++i) {
                                        MachOLayoutAbstraction::Segment& seg = segs[i];
                                        if ( seg.size() > 0 )
-                                               seg.setMappedAddress(inMemoryCache + cacheFileOffsetForAddress(seg.newAddress()));
+                                               seg.setMappedAddress(inMemoryCache + cacheFileOffsetForVMAddress(seg.newAddress()));
                                        //fprintf(stderr, "%s at %p to %p for %s\n", seg.name(), seg.mappedAddress(), (char*)seg.mappedAddress()+ seg.size(), it->layout->getID().name);
                                }
                        }
-
+       
+                       // also construct list of all pointers in cache to other things in cache
+                       std::vector<void*> pointersInData;
+                       pointersInData.reserve(1024);
+                       
                        // rebase each dylib in shared cache
                        for(typename std::vector<LayoutInfo>::const_iterator it = fDylibs.begin(); it != fDylibs.end(); ++it) {
                                try {
                                        Rebaser<A> r(*it->layout);
-                                       r.rebase();
+                                       r.rebase(pointersInData);
                                        //if ( verbose )
                                        //      fprintf(stderr, "update_dyld_shared_cache: for %s, rebasing dylib into cache for %s\n", archName(), it->layout->getID().name);
                                }
@@ -1344,20 +2577,6 @@ bool SharedCache<A>::update(const char* rootPath, const char* cacheDir, bool for
                                }
                        }
                        
-                       // merge/optimize all LINKEDIT segments
-                       if ( optimize ) {
-                               //fprintf(stderr, "update_dyld_shared_cache: original cache file size %uMB\n", cacheFileSize/(1024*1024));
-                               cacheFileSize = (this->optimizeLINKEDIT() - inMemoryCache);
-                               //fprintf(stderr, "update_dyld_shared_cache: optimized cache file size %uMB\n", cacheFileSize/(1024*1024));
-                               // update header to reduce mapping size
-                               dyldCacheHeader<E>* cacheHeader = (dyldCacheHeader<E>*)inMemoryCache;
-                               dyldCacheFileMapping<E>* mappings = (dyldCacheFileMapping<E>*)&inMemoryCache[sizeof(dyldCacheHeader<E>)];
-                               dyldCacheFileMapping<E>* lastMapping = &mappings[cacheHeader->mappingCount()-1];
-                               lastMapping->set_size(cacheFileSize-lastMapping->file_offset());
-                               // update fMappings so .map file will print correctly
-                               fMappings.back().sfm_size = cacheFileSize-fMappings.back().sfm_file_offset;
-                       }
-                       
                        if ( verbose )
                                fprintf(stderr, "update_dyld_shared_cache: for %s, updating binding information for %lu files:\n", archName(), fDylibs.size());
                        // instantiate a Binder for each image and add to map
@@ -1371,6 +2590,7 @@ bool SharedCache<A>::update(const char* rootPath, const char* cacheDir, bool for
                                if ( it->layout->getID().name != NULL )
                                        map[it->layout->getID().name] = binder;
                        }
+                       
                        // tell each Binder about the others
                        for(typename std::vector<Binder<A>*>::iterator it = binders.begin(); it != binders.end(); ++it) {
                                (*it)->setDependentBinders(map);
@@ -1380,7 +2600,16 @@ bool SharedCache<A>::update(const char* rootPath, const char* cacheDir, bool for
                                if ( verbose )
                                        fprintf(stderr, "update_dyld_shared_cache: for %s, updating binding information in cache for %s\n", archName(), (*it)->getDylibID());
                                try {
-                                       (*it)->bind();
+                                       (*it)->bind(pointersInData);
+                               }
+                               catch (const char* msg) {
+                                       throwf("%s in %s", msg, (*it)->getDylibID());
+                               }
+                       }
+                       // optimize binding
+                       for(typename std::vector<Binder<A>*>::iterator it = binders.begin(); it != binders.end(); ++it) {
+                               try {
+                                       (*it)->optimize();
                                }
                                catch (const char* msg) {
                                        throwf("%s in %s", msg, (*it)->getDylibID());
@@ -1391,93 +2620,444 @@ bool SharedCache<A>::update(const char* rootPath, const char* cacheDir, bool for
                                delete *it;
                        }
        
-                       // install signal handlers to delete temp file if program is killed 
-                       sCleanupFile = tempCachePath;
-                       ::signal(SIGINT, cleanup);
-                       ::signal(SIGBUS, cleanup);
-                       ::signal(SIGSEGV, cleanup);
+                       // merge/optimize all LINKEDIT segments
+                       if ( optimize ) {
+                               //fprintf(stderr, "update_dyld_shared_cache: original cache file size %uMB\n", cacheFileSize/(1024*1024));
+                               cacheFileSize = (this->optimizeLINKEDIT(keepSignatures, dontMapLocalSymbols) - inMemoryCache);
+                               //fprintf(stderr, "update_dyld_shared_cache: optimized cache file size %uMB\n", cacheFileSize/(1024*1024));
+                               // update header to reduce mapping size
+                               dyldCacheHeader<E>* cacheHeader = (dyldCacheHeader<E>*)inMemoryCache;
+                               dyldCacheFileMapping<E>* mappings = (dyldCacheFileMapping<E>*)&inMemoryCache[sizeof(dyldCacheHeader<E>)];
+                               dyldCacheFileMapping<E>* lastMapping = &mappings[cacheHeader->mappingCount()-1];
+                               lastMapping->set_size(cacheFileSize-lastMapping->file_offset());
+                               // update fMappings so .map file will print correctly
+                               fMappings.back().sfm_size = cacheFileSize-fMappings.back().sfm_file_offset;
+                               // update header
+                               //fprintf(stderr, "update_dyld_shared_cache: changing end of cache address from 0x%08llX to 0x%08llX\n", 
+                               //              header->codeSignatureOffset(), fMappings.back().sfm_address + fMappings.back().sfm_size);
+                               header->set_codeSignatureOffset(fMappings.back().sfm_file_offset + fMappings.back().sfm_size);
+                       }
                        
-                       // create temp file for cache
-                       int fd = ::open(tempCachePath, O_CREAT | O_RDWR | O_TRUNC, 0644);       
-                       if ( fd == -1 )
-                               throwf("can't create temp file %s, errnor=%d", tempCachePath, errno);
-                               
-                       // try to allocate whole cache file contiguously
-                       fstore_t fcntlSpec = { F_ALLOCATECONTIG|F_ALLOCATEALL, F_PEOFPOSMODE, 0, cacheFileSize, 0 };
-                       ::fcntl(fd, F_PREALLOCATE, &fcntlSpec);
+                       // unique objc selectors and update other objc metadata
+            if ( optimize ) {
+                               optimizeObjC(pointersInData);
+                               if ( progress ) {
+                                       // assuming objc optimizations takes 15% of time
+                                       fprintf(stdout, "%3u/%u\n", (archIndex+1)*55, archCount*100);
+                               }
+                       }
 
-                       // write out cache file
-                       if ( verbose )
-                               fprintf(stderr, "update_dyld_shared_cache: writing cache to disk\n");
-                       if ( ::pwrite(fd, inMemoryCache, cacheFileSize, 0) != cacheFileSize )
-                               throwf("write() failure creating cache file, errno=%d", errno);
+                       if ( addCacheSlideInfo() ) {
+                               // build bitmap of which pointers need sliding
+                               uint8_t* const dataStart = &inMemoryCache[fMappings[1].sfm_file_offset]; // R/W mapping is always second
+                               uint8_t* const dataEnd   = &inMemoryCache[fMappings[1].sfm_file_offset+fMappings[1].sfm_size];
+                               const int bitmapSize = (dataEnd - dataStart)/(4*8);
+                               uint8_t* bitmap = (uint8_t*)calloc(bitmapSize, 1);
+                               void* lastPointer = inMemoryCache;
+                               for(std::vector<void*>::iterator pit=pointersInData.begin(); pit != pointersInData.end(); ++pit) {
+                                       if ( *pit != lastPointer ) {
+                                               void* p = *pit;
+                                               if ( (p < dataStart) || ( p > dataEnd) )
+                                                       throwf("DATA pointer for sliding, out of range 0x%08lX\n", (long)((uint8_t*)p-inMemoryCache));
+                                               long offset = (long)((uint8_t*)p - dataStart);
+                                               if ( (offset % 4) != 0 )
+                                                       throwf("pointer not 4-byte aligned in DATA offset 0x%08lX\n", offset);
+                                               long byteIndex = offset / (4*8);
+                                               long bitInByte =  (offset % 32) >> 2;
+                                               bitmap[byteIndex] |= (1 << bitInByte);
+                                               lastPointer = p;
+                                       }
+                               }
+
+                               // allocate worst case size block of all slide info
+                               const int entry_size = 4096/(8*4); // 8 bits per byte, possible pointer every 4 bytes.
+                               const int toc_count = bitmapSize/entry_size;
+                               int slideInfoSize = sizeof(dyldCacheSlideInfo<E>) + 2*toc_count + entry_size*(toc_count+1);
+                               dyldCacheSlideInfo<E>* slideInfo = (dyldCacheSlideInfo<E>*)calloc(slideInfoSize, 1);
+                               slideInfo->set_version(1);
+                               slideInfo->set_toc_offset(sizeof(dyldCacheSlideInfo<E>));
+                               slideInfo->set_toc_count(toc_count);
+                               slideInfo->set_entries_offset((slideInfo->toc_offset()+2*toc_count+127)&(-128));
+                               slideInfo->set_entries_count(0);
+                               slideInfo->set_entries_size(entry_size);
+                               // append each unique entry 
+                               const dyldCacheSlideInfoEntry* bitmapAsEntries = (dyldCacheSlideInfoEntry*)bitmap;
+                               dyldCacheSlideInfoEntry* const entriesInSlidInfo = (dyldCacheSlideInfoEntry*)((char*)slideInfo+slideInfo->entries_offset());
+                               int entry_count = 0;
+                               for (int i=0; i < toc_count; ++i) {
+                                       const dyldCacheSlideInfoEntry* thisEntry = &bitmapAsEntries[i];
+                                       // see if it is same as one already added
+                                       bool found = false;
+                                       for (int j=0; j < entry_count; ++j) {
+                                               if ( memcmp(thisEntry, &entriesInSlidInfo[j], entry_size) == 0 ) {
+                                                       //fprintf(stderr, "toc[%d] optimized to %d\n", i, j);
+                                                       slideInfo->set_toc(i, j);
+                                                       found = true;
+                                                       break;
+                                               }       
+                                       }
+                                       if ( ! found ) {
+                                               // append to end
+                                               memcpy(&entriesInSlidInfo[entry_count], thisEntry, entry_size);
+                                               slideInfo->set_toc(i, entry_count++);
+                                       }
+                               }
+                               slideInfo->set_entries_count(entry_count);
+       
+                               int slideInfoPageSize = pageAlign(slideInfo->entries_offset() + entry_count*entry_size);
+                               cacheFileSize += slideInfoPageSize;
+                       
+                               // update mappings to increase RO size
+                               dyldCacheHeader<E>* cacheHeader = (dyldCacheHeader<E>*)inMemoryCache;
+                               dyldCacheFileMapping<E>* mappings = (dyldCacheFileMapping<E>*)&inMemoryCache[sizeof(dyldCacheHeader<E>)];
+                               dyldCacheFileMapping<E>* lastMapping = &mappings[cacheHeader->mappingCount()-1];
+                               lastMapping->set_size(lastMapping->size()+slideInfoPageSize);
+                               
+                               // update header to show location of slidePointers
+                               cacheHeader->set_slideInfoOffset(cacheHeader->codeSignatureOffset());
+                               cacheHeader->set_slideInfoSize(slideInfoPageSize);
+                               cacheHeader->set_codeSignatureOffset(cacheHeader->codeSignatureOffset()+slideInfoPageSize);
+                               
+                               // update fMappings so .map file will print correctly
+                               fMappings.back().sfm_size = cacheFileSize-fMappings.back().sfm_file_offset;
+                               
+                               // copy compressed into into buffer
+                               memcpy(&inMemoryCache[cacheHeader->slideInfoOffset()], slideInfo, slideInfoPageSize);   
+                       }
                        
-                       // flush to disk and close
-                       int result = ::fcntl(fd, F_FULLFSYNC, NULL);
-                       if ( result == -1 ) 
-                               fprintf(stderr, "update_dyld_shared_cache: warning, fcntl(F_FULLFSYNC) failed with errno=%d for %s\n", errno, tempCachePath);
-                       result = ::close(fd);
-                       if ( result != 0 ) 
-                               fprintf(stderr, "update_dyld_shared_cache: warning, close() failed with errno=%d for %s\n", errno, tempCachePath);
+                       // make sure after all optimizations, that whole cache file fits into shared region address range
+                       {
+                               dyldCacheHeader<E>* cacheHeader = (dyldCacheHeader<E>*)inMemoryCache;
+                               dyldCacheFileMapping<E>* mappings = (dyldCacheFileMapping<E>*)&inMemoryCache[cacheHeader->mappingOffset()];
+                               for (int i=0; i < cacheHeader->mappingCount(); ++i) {
+                                       uint64_t endAddr = mappings[i].address() + mappings[i].size();
+                                       if ( endAddr > (sharedRegionStartAddress() + sharedRegionSize()) ) {
+                                               throwf("update_dyld_shared_cache[%u] for arch=%s, shared cache will not fit in address space: 0x%llX\n",
+                                                       getpid(), fArchGraph->archName(), endAddr);
+                                       }
+                               }
+                       }
                        
-                       // atomically swap in new cache file, do this after F_FULLFSYNC
-                       result = ::rename(tempCachePath, cachePath);
-                       if ( result != 0 ) 
-                               throwf("can't swap newly create dyld shared cache file: rename(%s,%s) returned errno=%d", tempCachePath, cachePath, errno);
+                       // append local symbol info in an unmapped region
+                       if ( dontMapLocalSymbols ) {
+                               uint32_t spaceAtEnd = allocatedCacheSize - cacheFileSize;
+                               uint32_t localSymbolsOffset = pageAlign(cacheFileSize);
+                               dyldCacheLocalSymbolsInfo<E>* infoHeader = (dyldCacheLocalSymbolsInfo<E>*)(&inMemoryCache[localSymbolsOffset]);
+                               const uint32_t entriesOffset = sizeof(dyldCacheLocalSymbolsInfo<E>);
+                               const uint32_t entriesCount = fLocalSymbolInfos.size();
+                               const uint32_t nlistOffset = entriesOffset + entriesCount * sizeof(dyldCacheLocalSymbolEntry<E>);
+                               const uint32_t nlistCount = fUnmappedLocalSymbols.size();
+                               const uint32_t stringsOffset = nlistOffset + nlistCount * sizeof(macho_nlist<P>);
+                               const uint32_t stringsSize = fUnmappedLocalsStringPool.size();
+                               if ( stringsOffset+stringsSize > spaceAtEnd ) 
+                                       throwf("update_dyld_shared_cache[%u] for arch=%s, out of space for local symbols. Have 0x%X, Need 0x%X\n",
+                                                       getpid(), fArchGraph->archName(), spaceAtEnd, stringsOffset+stringsSize);
+                               // fill in local symbols info
+                               infoHeader->set_nlistOffset(nlistOffset);
+                               infoHeader->set_nlistCount(nlistCount);
+                               infoHeader->set_stringsOffset(stringsOffset);
+                               infoHeader->set_stringsSize(stringsSize);
+                               infoHeader->set_entriesOffset(entriesOffset);
+                               infoHeader->set_entriesCount(entriesCount);
+                               // copy info for each dylib
+                               dyldCacheLocalSymbolEntry<E>* entries = (dyldCacheLocalSymbolEntry<E>*)(&inMemoryCache[localSymbolsOffset+entriesOffset]);
+                               for (int i=0; i < entriesCount; ++i) {
+                                       entries[i].set_dylibOffset(fLocalSymbolInfos[i].dylibOffset);
+                                       entries[i].set_nlistStartIndex(fLocalSymbolInfos[i].nlistStartIndex);
+                                       entries[i].set_nlistCount(fLocalSymbolInfos[i].nlistCount);
+                               }
+                               // copy nlists
+                               memcpy(&inMemoryCache[localSymbolsOffset+nlistOffset], &fUnmappedLocalSymbols[0], nlistCount*sizeof(macho_nlist<P>));
+                               // copy string pool
+                               memcpy(&inMemoryCache[localSymbolsOffset+stringsOffset], fUnmappedLocalsStringPool.getBuffer(), stringsSize);
                                
-                       // flush everything to disk to assure rename() gets recorded
-                       ::sync();
-                       didUpdate = true;
+                               // update state
+                               fUnmappedLocalSymbolsSize = pageAlign(stringsOffset + stringsSize);
+                               cacheFileSize = localSymbolsOffset + fUnmappedLocalSymbolsSize;
+                               
+                               // update header to show location of slidePointers
+                               dyldCacheHeader<E>* cacheHeader = (dyldCacheHeader<E>*)inMemoryCache;
+                               cacheHeader->set_localSymbolsOffset(localSymbolsOffset);
+                               cacheHeader->set_localSymbolsSize(stringsOffset+stringsSize);
+                               cacheHeader->set_codeSignatureOffset(cacheFileSize);
+                       }
                        
-                       // restore default signal handlers
-                       ::signal(SIGINT, SIG_DFL);
-                       ::signal(SIGBUS, SIG_DFL);
-                       ::signal(SIGSEGV, SIG_DFL);
-
-                       // generate human readable "map" file that shows the layout of the cache file
-                       if ( verbose )
-                               fprintf(stderr, "update_dyld_shared_cache: writing .map file to disk\n");
-                       sprintf(tempCachePath, "%s.map", cachePath);// re-use path buffer
-                       FILE* fmap = ::fopen(tempCachePath, "w");       
-                       if ( fmap == NULL ) {
-                               fprintf(stderr, "can't create map file %s, errnor=%d", tempCachePath, errno);
+                       // compute UUID of whole cache
+                       uint8_t digest[16];
+                       CC_MD5(inMemoryCache, cacheFileSize, digest);
+                       // <rdar://problem/6723729> uuids should conform to RFC 4122 UUID version 4 & UUID version 5 formats
+                       digest[6] = ( digest[6] & 0x0F ) | ( 3 << 4 );
+                       digest[8] = ( digest[8] & 0x3F ) | 0x80;
+                       ((dyldCacheHeader<E>*)inMemoryCache)->set_uuid(digest);
+                       
+                       if ( fVerify ) {
+                               // if no existing cache, say so
+                               if ( fExistingCacheForVerification == NULL ) {
+                                       throwf("update_dyld_shared_cache[%u] for arch=%s, could not verify because cache file does not exist in /var/db/dyld/\n",
+                                        getpid(), archName());
+                               }
+                               // new cache is built, compare header entries
+                               const dyldCacheHeader<E>* newHeader = (dyldCacheHeader<E>*)inMemoryCache;
+                               const dyldCacheHeader<E>* oldHeader = (dyldCacheHeader<E>*)fExistingCacheForVerification;
+                               if ( newHeader->mappingCount() != oldHeader->mappingCount() ) {
+                                       throwf("update_dyld_shared_cache[%u] for arch=%s, could not verify cache because caches have a different number of mappings\n",
+                                        getpid(), archName());
+                               }
+                               const dyldCacheFileMapping<E>* newMappings = (dyldCacheFileMapping<E>*)&inMemoryCache[newHeader->mappingOffset()];
+                               const dyldCacheFileMapping<E>* oldMappings = (dyldCacheFileMapping<E>*)&fExistingCacheForVerification[oldHeader->mappingOffset()];
+                               for (int i=0; i < newHeader->mappingCount(); ++i) {
+                                       if ( newMappings[i].address() != oldMappings[i].address() ) {
+                                               throwf("update_dyld_shared_cache[%u] for arch=%s, could not verify cache because mapping %d starts at a different address 0x%0llX vs 0x%0llX\n", 
+                                                       getpid(), archName(), i, newMappings[i].address(), oldMappings[i].address() );
+                                       }
+                                       if ( newMappings[i].size() != oldMappings[i].size() ) {
+                                               throwf("update_dyld_shared_cache[%u] for arch=%s, could not verify cache because mapping %d has a different size\n",
+                                                getpid(), archName(), i);
+                                       }
+                               }
+                               
+                               //fprintf(stderr, "%s existing cache = %p\n", archName(), fExistingCacheForVerification);
+                               //fprintf(stderr, "%s new cache = %p\n", archName(), inMemoryCache);
+                               // compare content to existing cache page by page
+                               for (int offset=0; offset < cacheFileSize; offset += 4096) {
+                                       if ( memcmp(&inMemoryCache[offset], &fExistingCacheForVerification[offset], 4096) != 0 ) {
+                                               fprintf(stderr, "verifier found differences on page offset 0x%08X for %s:\n", offset, archName());
+                                               for(typename std::vector<LayoutInfo>::const_iterator it = fDylibs.begin(); it != fDylibs.end(); ++it, ++dylibIndex) {
+                                                       const std::vector<MachOLayoutAbstraction::Segment>& segs = it->layout->getSegments();
+                                                       for(std::vector<MachOLayoutAbstraction::Segment>::const_iterator sit = segs.begin(); sit != segs.end(); ++sit) {
+                                                               const MachOLayoutAbstraction::Segment& seg = *sit;
+                                                               if ( (seg.mappedAddress() <= &inMemoryCache[offset]) && (&inMemoryCache[offset] < ((uint8_t*)seg.mappedAddress() + seg.fileSize())) ) {
+                                                                       // all LINKEDITs point to the same region, so just print one
+                                                                       if ( strcmp(seg.name(), "__LINKEDIT") == 0 ) 
+                                                                               fprintf(stderr, "  in merged LINKEDIT segment\n");
+                                                                       else
+                                                                               fprintf(stderr, "  in segment %s of dylib %s\n", seg.name(), it->layout->getID().name);
+                                                                       break;
+                                                               }
+                                                       }
+                                               }
+                                               for (int po=0; po < 4096; po += 16) {
+                                                       if ( memcmp(&inMemoryCache[offset+po], &fExistingCacheForVerification[offset+po], 16) != 0 ) {
+                                                               fprintf(stderr, "   existing: 0x%08X: ", offset+po);
+                                                               for ( int j=0; j < 16; ++j)
+                                                                       fprintf(stderr, " 0x%02X", fExistingCacheForVerification[offset+po+j]);
+                                                               fprintf(stderr, "\n");
+                                                               fprintf(stderr, "  should be: 0x%08X: ", offset+po);
+                                                               for ( int j=0; j < 16; ++j)
+                                                                       fprintf(stderr, " 0x%02X", inMemoryCache[offset+po+j]);
+                                                               fprintf(stderr, "\n");
+                                                       }
+                                               }
+                                       }
+                               }
                        }
                        else {
-                               for(std::vector<shared_file_mapping_np>::iterator it = fMappings.begin(); it != fMappings.end(); ++it) {
-                                       const char* prot = "RW";
-                                       if ( it->sfm_init_prot == (VM_PROT_EXECUTE|VM_PROT_READ) )
-                                               prot = "EX";
-                                       else if ( it->sfm_init_prot == VM_PROT_READ )
-                                               prot = "RO";
-                                       else if ( it->sfm_init_prot == (VM_PROT_EXECUTE|VM_PROT_WRITE|VM_PROT_READ) )
-                                               prot = "WX";
-                                       if ( it->sfm_size > 1024*1024 )
-                                               fprintf(fmap, "mapping %s %4lluMB 0x%0llX -> 0x%0llX\n", prot, it->sfm_size/(1024*1024),
-                                                                                                                       it->sfm_address, it->sfm_address+it->sfm_size);
-                                       else
-                                               fprintf(fmap, "mapping %s %4lluKB 0x%0llX -> 0x%0llX\n", prot, it->sfm_size/1024,
-                                                                                                                       it->sfm_address, it->sfm_address+it->sfm_size);
+                               // install signal handlers to delete temp file if program is killed 
+                               sCleanupFile = tempCachePath;
+                               ::signal(SIGINT, cleanup);
+                               ::signal(SIGBUS, cleanup);
+                               ::signal(SIGSEGV, cleanup);
+                               
+                               // create var/db/dyld dirs if needed
+                               char dyldDirs[1024];
+                               strcpy(dyldDirs, fCacheFilePath);
+                               char* lastSlash = strrchr(dyldDirs, '/');
+                               if ( lastSlash != NULL )
+                                       lastSlash[1] = '\0';
+                               struct stat stat_buf;
+                               if ( stat(dyldDirs, &stat_buf) != 0 ) {
+                                       const char* afterSlash = &dyldDirs[1];
+                                       char* slash;
+                                       while ( (slash = strchr(afterSlash, '/')) != NULL ) {
+                                               *slash = '\0';
+                                               ::mkdir(dyldDirs, S_IRWXU | S_IRGRP|S_IXGRP | S_IROTH|S_IXOTH);
+                                               *slash = '/';
+                                               afterSlash = slash+1;
+                                       }
                                }
-                               for(typename std::vector<LayoutInfo>::const_iterator it = fDylibs.begin(); it != fDylibs.end(); ++it) {
-                                       fprintf(fmap, "%s\n", it->layout->getID().name);
-                                       const std::vector<MachOLayoutAbstraction::Segment>&     segs = it->layout->getSegments();
-                                       for (int i=0; i < segs.size(); ++i) {
-                                               const MachOLayoutAbstraction::Segment& seg = segs[i];
-                                               fprintf(fmap, "\t%16s 0x%0llX -> 0x%0llX\n", seg.name(), seg.newAddress(), seg.newAddress()+seg.size());
+                               
+                               // create temp file for cache
+                               int fd = ::open(tempCachePath, O_CREAT | O_RDWR | O_TRUNC, 0644);       
+                               if ( fd == -1 )
+                                       throwf("can't create temp file %s, errnor=%d", tempCachePath, errno);
+                                       
+                               // try to allocate whole cache file contiguously
+                               fstore_t fcntlSpec = { F_ALLOCATECONTIG|F_ALLOCATEALL, F_PEOFPOSMODE, 0, cacheFileSize, 0 };
+                               ::fcntl(fd, F_PREALLOCATE, &fcntlSpec);
+
+                               // write out cache file
+                               if ( verbose )
+                                       fprintf(stderr, "update_dyld_shared_cache: writing cache to disk: %s\n", tempCachePath);
+                               if ( ::pwrite(fd, inMemoryCache, cacheFileSize, 0) != cacheFileSize )
+                                       throwf("write() failure creating cache file, errno=%d", errno);
+                               if ( progress ) {
+                                       // assuming write takes 35% of time
+                                       fprintf(stdout, "%3u/%u\n", (archIndex+1)*90, archCount*100);
+                               }
+                               
+                               // flush to disk and close
+                               int result = ::fcntl(fd, F_FULLFSYNC, NULL);
+                               if ( result == -1 ) 
+                                       fprintf(stderr, "update_dyld_shared_cache: warning, fcntl(F_FULLFSYNC) failed with errno=%d for %s\n", errno, tempCachePath);
+                               result = ::close(fd);
+                               if ( result != 0 ) 
+                                       fprintf(stderr, "update_dyld_shared_cache: warning, close() failed with errno=%d for %s\n", errno, tempCachePath);
+                               
+                               if ( !iPhoneOS )
+                                       adhoc_codesign_share_cache(tempCachePath);
+
+                               // <rdar://problem/7901042> Make life easier for the kernel at shutdown.
+                               // If we just move the new cache file over the old, the old file
+                               // may need to exist in the open-unlink state.  But because it
+                               // may be mapped into the shared region, it cannot be deleted
+                               // until all user processes are terminated.  That leaves are
+                               // small to non-existent window for the kernel to delete the
+                               // old cache file.
+                               if ( fCacheFileInFinalLocation ) {
+                                       char tmpDirPath[64];
+                                       const char* pathLastSlash = strrchr(fCacheFilePath, '/');
+                                       if ( pathLastSlash != NULL ) {
+                                               sprintf(tmpDirPath, "/var/run%s.old.%u", pathLastSlash, getpid());
+                                               // move existing cache file to /var/run to be clean up next boot
+                                               result = ::rename(fCacheFilePath, tmpDirPath);
+                                               if ( result != 0 ) {
+                                                       if ( errno != ENOENT )
+                                                               fprintf(stderr, "update_dyld_shared_cache: warning, unable to move existing cache to %s errno=%d for %s\n", tmpDirPath, errno, fCacheFilePath);
+                                               }
                                        }
                                }
-                               if ( warnings.size() > 0 ) {
-                                       fprintf(fmap, "# Warnings:\n");
-                                       for (std::vector<const char*>::iterator it=warnings.begin(); it != warnings.end(); ++it) {
-                                               fprintf(fmap, "# %s\n", *it);
+                               
+                               // move new cache file to correct location for use after reboot
+                               if ( verbose )
+                                       fprintf(stderr, "update_dyld_shared_cache: atomically moving cache file into place: %s\n", fCacheFilePath);
+                               result = ::rename(tempCachePath, fCacheFilePath);
+                               if ( result != 0 ) 
+                                       throwf("can't swap newly create dyld shared cache file: rename(%s,%s) returned errno=%d", tempCachePath, fCacheFilePath, errno);
+                               
+                               
+                               // flush everything to disk to assure rename() gets recorded
+                               sync_volume(fCacheFilePath);
+                               didUpdate = true;
+                               
+                               // restore default signal handlers
+                               ::signal(SIGINT, SIG_DFL);
+                               ::signal(SIGBUS, SIG_DFL);
+                               ::signal(SIGSEGV, SIG_DFL);
+
+                               // generate human readable "map" file that shows the layout of the cache file
+                               if ( verbose )
+                                       fprintf(stderr, "update_dyld_shared_cache: writing .map file to disk\n");
+                               char mapFilePath[strlen(fCacheFilePath)+16];
+                               sprintf(mapFilePath, "%s.map", fCacheFilePath);
+                               char tempMapFilePath[strlen(fCacheFilePath)+32];
+                               sprintf(tempMapFilePath, "%s.map%u", fCacheFilePath, getpid());
+                               FILE* fmap = ::fopen(tempMapFilePath, "w");     
+                               if ( fmap == NULL ) {
+                                       fprintf(stderr, "can't create map file %s, errnor=%d", tempCachePath, errno);
+                               }
+                               else {
+                                       for(std::vector<shared_file_mapping_np>::iterator it = fMappings.begin(); it != fMappings.end(); ++it) {
+                                               const char* prot = "RW";
+                                               if ( it->sfm_init_prot == (VM_PROT_EXECUTE|VM_PROT_READ) )
+                                                       prot = "EX";
+                                               else if ( it->sfm_init_prot == VM_PROT_READ )
+                                                       prot = "RO";
+                                               else if ( it->sfm_init_prot == (VM_PROT_EXECUTE|VM_PROT_WRITE|VM_PROT_READ) )
+                                                       prot = "WX";
+                                               if ( it->sfm_size > 1024*1024 )
+                                                       fprintf(fmap, "mapping  %s %4lluMB 0x%0llX -> 0x%0llX\n", prot, it->sfm_size/(1024*1024),
+                                                                                                                               it->sfm_address, it->sfm_address+it->sfm_size);
+                                               else
+                                                       fprintf(fmap, "mapping  %s %4lluKB 0x%0llX -> 0x%0llX\n", prot, it->sfm_size/1024,
+                                                                                                                               it->sfm_address, it->sfm_address+it->sfm_size);
                                        }
+
+                                       fprintf(fmap, " linkedit   %4uKB 0x%0llX -> 0x%0llX weak binding info\n",               
+                                                               (fOffsetOfExportInfoInCombinedLinkedit-fOffsetOfWeakBindInfoInCombinedLinkedit)/1024,
+                                                               fLinkEditsStartAddress+fOffsetOfWeakBindInfoInCombinedLinkedit,
+                                                               fLinkEditsStartAddress+fOffsetOfExportInfoInCombinedLinkedit);
+                                       fprintf(fmap, " linkedit   %4uKB 0x%0llX -> 0x%0llX export info\n",             
+                                                               (fOffsetOfBindInfoInCombinedLinkedit-fOffsetOfExportInfoInCombinedLinkedit)/1024,
+                                                               fLinkEditsStartAddress+fOffsetOfExportInfoInCombinedLinkedit,
+                                                               fLinkEditsStartAddress+fOffsetOfBindInfoInCombinedLinkedit);
+                                       fprintf(fmap, " linkedit   %4uKB 0x%0llX -> 0x%0llX binding info\n",            
+                                                               (fOffsetOfLazyBindInfoInCombinedLinkedit-fOffsetOfBindInfoInCombinedLinkedit)/1024,
+                                                               fLinkEditsStartAddress+fOffsetOfBindInfoInCombinedLinkedit,
+                                                               fLinkEditsStartAddress+fOffsetOfLazyBindInfoInCombinedLinkedit);
+                                       fprintf(fmap, " linkedit   %4uKB 0x%0llX -> 0x%0llX lazy binding info\n",               
+                                                               (fOffsetOfOldSymbolTableInfoInCombinedLinkedit-fOffsetOfLazyBindInfoInCombinedLinkedit)/1024,
+                                                               fLinkEditsStartAddress+fOffsetOfLazyBindInfoInCombinedLinkedit,
+                                                               fLinkEditsStartAddress+fOffsetOfOldSymbolTableInfoInCombinedLinkedit);
+                                       fprintf(fmap, " linkedit   %4uMB 0x%0llX -> 0x%0llX non-dyld symbol table size\n",              
+                                                               (fSizeOfOldSymbolTableInfoInCombinedLinkedit)/(1024*1024),
+                                                               fLinkEditsStartAddress+fOffsetOfOldSymbolTableInfoInCombinedLinkedit,
+                                                               fLinkEditsStartAddress+fOffsetOfOldSymbolTableInfoInCombinedLinkedit+fSizeOfOldSymbolTableInfoInCombinedLinkedit);                              
+                                       if ( fSizeOfFunctionStartsInCombinedLinkedit != 0 )
+                                               fprintf(fmap, " linkedit   %4uKB 0x%0llX -> 0x%0llX non-dyld functions starts size\n",          
+                                                               fSizeOfFunctionStartsInCombinedLinkedit/1024,
+                                                               fLinkEditsStartAddress+fOffsetOfFunctionStartsInCombinedLinkedit,
+                                                               fLinkEditsStartAddress+fOffsetOfFunctionStartsInCombinedLinkedit+fSizeOfFunctionStartsInCombinedLinkedit);                              
+                                       if ( fSizeOfDataInCodeInCombinedLinkedit != 0 )
+                                               fprintf(fmap, " linkedit   %4uKB 0x%0llX -> 0x%0llX non-dyld data-in-code info size\n",         
+                                                               fSizeOfDataInCodeInCombinedLinkedit/1024,
+                                                               fLinkEditsStartAddress+fOffsetOfDataInCodeInCombinedLinkedit,
+                                                               fLinkEditsStartAddress+fOffsetOfDataInCodeInCombinedLinkedit+fSizeOfDataInCodeInCombinedLinkedit);                              
+                                       if ( fSizeOfOldExternalRelocationsInCombinedLinkedit != 0 )
+                                               fprintf(fmap, " linkedit   %4uKB 0x%0llX -> 0x%0llX non-dyld external relocs size\n",           
+                                                               fSizeOfOldExternalRelocationsInCombinedLinkedit/1024,
+                                                               fLinkEditsStartAddress+fOffsetOfOldExternalRelocationsInCombinedLinkedit,
+                                                               fLinkEditsStartAddress+fOffsetOfOldExternalRelocationsInCombinedLinkedit+fSizeOfOldExternalRelocationsInCombinedLinkedit);                              
+                                       fprintf(fmap, " linkedit   %4uKB 0x%0llX -> 0x%0llX non-dyld indirect symbol table size\n",             
+                                                               fSizeOfOldIndirectSymbolsInCombinedLinkedit/1024,
+                                                               fLinkEditsStartAddress+fOffsetOfOldIndirectSymbolsInCombinedLinkedit,
+                                                               fLinkEditsStartAddress+fOffsetOfOldIndirectSymbolsInCombinedLinkedit+fSizeOfOldIndirectSymbolsInCombinedLinkedit);                              
+                                       fprintf(fmap, " linkedit   %4uMB 0x%0llX -> 0x%0llX non-dyld string pool\n",            
+                                                               (fSizeOfOldStringPoolInCombinedLinkedit)/(1024*1024),
+                                                               fLinkEditsStartAddress+fOffsetOfOldStringPoolInCombinedLinkedit,
+                                                               fLinkEditsStartAddress+fOffsetOfOldStringPoolInCombinedLinkedit+fSizeOfOldStringPoolInCombinedLinkedit);                                
+                                       
+                                       fprintf(fmap, "unmapped -- %4uMB local symbol info\n", fUnmappedLocalSymbolsSize/(1024*1024));                                  
+                                       
+                                       uint64_t endMappingAddr = fMappings[2].sfm_address + fMappings[2].sfm_size;
+                                       fprintf(fmap, "total map   %4lluMB\n", (endMappingAddr - sharedRegionStartAddress())/(1024*1024));      
+                                       if ( sharedRegionStartWritableAddress(0) == 0x7FFF70000000LL ) {
+                                               // x86_64 has different slide constraints
+                                               uint64_t freeSpace = 256*1024*1024 - fMappings[1].sfm_size;
+                                               fprintf(fmap, "r/w space   %4lluMB -> %d bits of entropy for ASLR\n\n", freeSpace/(1024*1024), (int)log2(freeSpace/4096));
+                                       }
+                                       else {
+                                               uint64_t freeSpace = sharedRegionStartAddress() + sharedRegionSize() - endMappingAddr;
+                                               fprintf(fmap, "free space  %4lluMB -> %d bits of entropy for ASLR\n\n", freeSpace/(1024*1024), (int)log2(freeSpace/4096));
+                                       }
+                                       
+                                       for(typename std::vector<LayoutInfo>::const_iterator it = fDylibs.begin(); it != fDylibs.end(); ++it) {
+                                               fprintf(fmap, "%s\n", it->layout->getID().name);
+                                               for (std::vector<const char*>::const_iterator ait = it->aliases.begin(); ait != it->aliases.end(); ++ait) 
+                                                       fprintf(fmap, "%s\n", *ait);
+                                               const std::vector<MachOLayoutAbstraction::Segment>&     segs = it->layout->getSegments();
+                                               for (int i=0; i < segs.size(); ++i) {
+                                                       const MachOLayoutAbstraction::Segment& seg = segs[i];
+                                                       fprintf(fmap, "\t%16s 0x%0llX -> 0x%0llX\n", seg.name(), seg.newAddress(), seg.newAddress()+seg.size());
+                                               }
+                                       }
+                                       if ( warnings.size() > 0 ) {
+                                               fprintf(fmap, "# Warnings:\n");
+                                               for (std::vector<const char*>::iterator it=warnings.begin(); it != warnings.end(); ++it) {
+                                                       fprintf(fmap, "# %s\n", *it);
+                                               }
+                                       }
+                                       fclose(fmap);
+                                       result = ::rename(tempMapFilePath, mapFilePath);
                                }
-                               fclose(fmap);
                        }
                        
                        // free in memory cache
                        vm_deallocate(mach_task_self(), (vm_address_t)inMemoryCache, allocatedCacheSize);
                        inMemoryCache = NULL;
+                       if ( progress ) {
+                               // finished
+                               fprintf(stdout, "%3u/%u\n", (archIndex+1)*100, archCount*100);
+                       }
                }
                catch (...){
                        // remove temp cache file
@@ -1546,7 +3126,16 @@ static void parsePathsFile(const char* filePath, std::vector<const char*>& paths
                                                *last = '\0';
                                                --last;
                                        }
-                                       paths.push_back(symbolStart);
+                                       // <rdar://problem/8305479> images in shared cache are bound against different IOKit than found at runtime
+                                       // HACK:  Just ignore the known bad IOKit
+                                       if ( strcmp(symbolStart, "/System/Library/Frameworks/IOKit.framework/IOKit") == 0 ) {
+                                               // Disable warning because after three years <rdar://problem/7089957> has still not been fixed...
+                                               //fprintf(stderr, "update_dyld_shared_cache: warning, ignoring /System/Library/Frameworks/IOKit.framework/IOKit\n");
+                                               //warnings.push_back("update_dyld_shared_cache: warning, ignoring /System/Library/Frameworks/IOKit.framework/IOKit\n");
+                                       }
+                                       else {
+                                               paths.push_back(symbolStart);
+                                       }
                                        symbolStart = NULL;
                                        state = lineStart;
                                }
@@ -1561,10 +3150,32 @@ static void parsePathsFile(const char* filePath, std::vector<const char*>& paths
 }
 
 
-static void scanForSharedDylibs(const char* rootPath, const char* dirOfPathFiles, const std::set<cpu_type_t>& onlyArchs)
+
+static void setSharedDylibs(const char* rootPath, const char* overlayPath, const std::set<ArchPair>& onlyArchs, std::vector<const char*> rootsPaths)
+{
+       // set file system root
+       ArchGraph::setFileSystemRoot(rootPath);
+       ArchGraph::setFileSystemOverlay(overlayPath);
+
+       // initialize all architectures requested
+       for(std::set<ArchPair>::iterator a = onlyArchs.begin(); a != onlyArchs.end(); ++a)
+               ArchGraph::addArchPair(*a);
+
+       // add roots to graph
+       for(std::vector<const char*>::const_iterator it = rootsPaths.begin(); it != rootsPaths.end(); ++it) 
+               ArchGraph::addRoot(*it, onlyArchs);
+
+       // determine shared dylibs
+       for(std::set<ArchPair>::iterator a = onlyArchs.begin(); a != onlyArchs.end(); ++a)
+               ArchGraph::findSharedDylibs(*a);
+}
+
+
+static void scanForSharedDylibs(const char* rootPath, const char* overlayPath, const char* dirOfPathFiles, const std::set<ArchPair>& onlyArchs)
 {
        char rootDirOfPathFiles[strlen(rootPath)+strlen(dirOfPathFiles)+2];
-       if ( strlen(rootPath) != 0 ) {
+       // in -root mode, look for roots in /rootpath/var/db/dyld
+       if ( rootPath[0] != '\0' ) {
                strcpy(rootDirOfPathFiles, rootPath);
                strcat(rootDirOfPathFiles, dirOfPathFiles);
                dirOfPathFiles = rootDirOfPathFiles;
@@ -1578,14 +3189,23 @@ static void scanForSharedDylibs(const char* rootPath, const char* dirOfPathFiles
        if ( dir == NULL )
                throwf("%s does not exist, errno=%d\n", dirOfPathFiles, errno);
        for (dirent* entry = ::readdir(dir); entry != NULL; entry = ::readdir(dir)) {
-               if ( entry->d_type == DT_REG ) {
-                       // only look at files ending in .paths
+               if ( entry->d_type == DT_REG || entry->d_type == DT_UNKNOWN ) {
+                       // only look at regular files ending in .paths
                        if ( strcmp(&entry->d_name[entry->d_namlen-6], ".paths") == 0 ) {
+                               struct stat tmpStatPathsFile;
                                char fullPath[strlen(dirOfPathFiles)+entry->d_namlen+2];
                                strcpy(fullPath, dirOfPathFiles);
                                strcat(fullPath, "/");
                                strcat(fullPath, entry->d_name);
-                               parsePathsFile(fullPath, rootsPaths);
+                               if ( lstat(fullPath, &tmpStatPathsFile) == -1 ) {
+                                       fprintf(stderr, "update_dyld_shared_cache: can't access %s\n", fullPath);
+                               } 
+                               else if ( S_ISREG(tmpStatPathsFile.st_mode) ) {
+                                       parsePathsFile(fullPath, rootsPaths);
+                               } 
+                               else {
+                                       fprintf(stderr, "update_dyld_shared_cache: wrong file type for %s\n", fullPath);
+                               }
                        }
                        else {
                                fprintf(stderr, "update_dyld_shared_cache: warning, ignore file with wrong extension: %s\n", entry->d_name);
@@ -1593,24 +3213,17 @@ static void scanForSharedDylibs(const char* rootPath, const char* dirOfPathFiles
                }
        }
        ::closedir(dir);
-
-       // set file system root
-       ArchGraph::setFileSystemRoot(rootPath);
-
-       // initialize all architectures requested
-       for(std::set<cpu_type_t>::iterator a = onlyArchs.begin(); a != onlyArchs.end(); ++a)
-               ArchGraph::addArch(*a);
-
-       // add roots to graph
-       for(std::vector<const char*>::iterator it = rootsPaths.begin(); it != rootsPaths.end(); ++it) 
-               ArchGraph::addRoot(*it, onlyArchs);
-
-       // determine shared dylibs
-       for(std::set<cpu_type_t>::iterator a = onlyArchs.begin(); a != onlyArchs.end(); ++a)
-               ArchGraph::findSharedDylibs(*a);
        
        if ( rootsPaths.size() == 0 )
                fprintf(stderr, "update_dyld_shared_cache: warning, no entries found in shared_region_roots\n");
+       setSharedDylibs(rootPath, overlayPath, onlyArchs, rootsPaths);
+}
+
+static void setSharedDylibs(const char* rootPath, const char* overlayPath, const char* pathsFile, const std::set<ArchPair>& onlyArchs)
+{
+       std::vector<const char*> rootsPaths;
+       parsePathsFile(pathsFile, rootsPaths);
+       setSharedDylibs(rootPath, overlayPath, onlyArchs, rootsPaths);
 }
 
 
@@ -1621,15 +3234,15 @@ static void scanForSharedDylibs(const char* rootPath, const char* dirOfPathFiles
 // creation time was before the last restart of this machine.
 static void deleteOrphanTempCacheFiles()
 {
-       DIR* dir = ::opendir(DYLD_SHARED_CACHE_DIR);
+       DIR* dir = ::opendir(MACOSX_DYLD_SHARED_CACHE_DIR);
        if ( dir != NULL ) {
                std::vector<const char*> filesToDelete;
                for (dirent* entry = ::readdir(dir); entry != NULL; entry = ::readdir(dir)) {
                        if ( entry->d_type == DT_REG ) {
                                // only look at files with .tmp in name
                                if ( strstr(entry->d_name, ".tmp") != NULL ) {
-                                       char fullPath[strlen(DYLD_SHARED_CACHE_DIR)+entry->d_namlen+2];
-                                       strcpy(fullPath, DYLD_SHARED_CACHE_DIR);
+                                       char fullPath[strlen(MACOSX_DYLD_SHARED_CACHE_DIR)+entry->d_namlen+2];
+                                       strcpy(fullPath, MACOSX_DYLD_SHARED_CACHE_DIR);
                                        strcat(fullPath, "/");
                                        strcat(fullPath, entry->d_name);
                                        struct stat tmpFileStatInfo;
@@ -1657,54 +3270,55 @@ static void deleteOrphanTempCacheFiles()
 
 
 
-static bool updateSharedeCacheFile(const char* rootPath, const char* cacheDir, const std::set<cpu_type_t>& onlyArchs, 
-                                                                       bool force, bool alphaSort, bool optimize, bool deleteExistingFirst)
+static bool updateSharedeCacheFile(const char* rootPath, const char* overlayPath, const char* cacheDir, bool explicitCacheDir, const std::set<ArchPair>& onlyArchs, 
+                                                                       bool force, bool alphaSort, bool optimize, bool deleteExistingFirst, bool verify, bool keepSignatures, bool dontMapLocalSymbols)
 {
        bool didUpdate = false;
        // get dyld load address info
-       UniversalMachOLayout* dyldLayout = new UniversalMachOLayout("/usr/lib/dyld", &onlyArchs);
-
+       UniversalMachOLayout* dyldLayout = NULL;
+       char dyldPath[1024];
+       strlcpy(dyldPath, rootPath, 1024);
+       strlcat(dyldPath, "/usr/lib/dyld", 1024);
+       struct stat stat_buf;
+       if ( stat(dyldPath, &stat_buf) == 0 ) {
+               dyldLayout = new UniversalMachOLayout(dyldPath, &onlyArchs);
+       }
+       else {
+               dyldLayout = new UniversalMachOLayout("/usr/lib/dyld", &onlyArchs);
+       }
        const int archCount = onlyArchs.size();
        int index = 0;
-       for(std::set<cpu_type_t>::iterator a = onlyArchs.begin(); a != onlyArchs.end(); ++a, ++index) {
-               const MachOLayoutAbstraction* dyldLayoutForArch = dyldLayout->getArch(*a);
-               if ( dyldLayoutForArch == NULL )
-                       throw "dyld not avaiable for specified architecture";
-               uint64_t dyldBaseAddress = dyldLayoutForArch->getBaseAddress();
-               switch ( *a ) {
-                       case CPU_TYPE_POWERPC:
-                               {
-                                       SharedCache<ppc> cache(ArchGraph::getArch(*a), alphaSort, dyldBaseAddress);
-               #if __i386__
-                                       // <rdar://problem/5217377> Rosetta does not work with optimized dyld shared cache
-                                       didUpdate |= cache.update(rootPath, cacheDir, force, false, deleteExistingFirst, index, archCount);
-               #else
-                                       didUpdate |= cache.update(rootPath, cacheDir, force, optimize, deleteExistingFirst, index, archCount);
-               #endif
-                               }
-                               break;
-                       case CPU_TYPE_POWERPC64:
+       for(std::set<ArchPair>::iterator a = onlyArchs.begin(); a != onlyArchs.end(); ++a, ++index) {
+               const MachOLayoutAbstraction* dyldLayoutForArch = dyldLayout->getSlice(*a);
+               uint64_t dyldBaseAddress = 0;
+               if ( dyldLayoutForArch != NULL )
+                       dyldBaseAddress = dyldLayoutForArch->getBaseAddress();
+               else
+                       fprintf(stderr, "update_dyld_shared_cache: warning, dyld not available for specified architectures\n");
+               switch ( a->arch ) {
+                       case CPU_TYPE_I386:
                                {
-                                       SharedCache<ppc64> cache(ArchGraph::getArch(*a), alphaSort, dyldBaseAddress);
-                                       didUpdate |= cache.update(rootPath, cacheDir, force, optimize, deleteExistingFirst, index, archCount);
+                                       SharedCache<x86> cache(ArchGraph::graphForArchPair(*a), rootPath, overlayPath, cacheDir, explicitCacheDir, alphaSort, verify, optimize, dyldBaseAddress);
+                                       didUpdate |= cache.update(force, optimize, deleteExistingFirst, index, archCount, keepSignatures, dontMapLocalSymbols);
                                }
                                break;
-                       case CPU_TYPE_I386:
+                       case CPU_TYPE_X86_64:
                                {
-                                       SharedCache<x86> cache(ArchGraph::getArch(*a), alphaSort, dyldBaseAddress);
-                                       didUpdate |= cache.update(rootPath, cacheDir, force, optimize, deleteExistingFirst, index, archCount);
+                                       SharedCache<x86_64> cache(ArchGraph::graphForArchPair(*a), rootPath, overlayPath, cacheDir, explicitCacheDir, alphaSort, verify, optimize, dyldBaseAddress);
+                                       didUpdate |= cache.update(force, optimize, deleteExistingFirst, index, archCount, keepSignatures, dontMapLocalSymbols);
                                }
                                break;
-                       case CPU_TYPE_X86_64:
+                       case CPU_TYPE_ARM:
                                {
-                                       SharedCache<x86_64> cache(ArchGraph::getArch(*a), alphaSort, dyldBaseAddress);
-                                       didUpdate |= cache.update(rootPath, cacheDir, force, optimize, deleteExistingFirst, index, archCount);
+                                       SharedCache<arm> cache(ArchGraph::graphForArchPair(*a), rootPath, overlayPath, cacheDir, explicitCacheDir, alphaSort, verify, optimize, dyldBaseAddress);
+                                       didUpdate |= cache.update(force, optimize, deleteExistingFirst, index, archCount, keepSignatures, dontMapLocalSymbols);
                                }
                                break;
                }
        }
        
-       deleteOrphanTempCacheFiles();
+       if ( !iPhoneOS )
+               deleteOrphanTempCacheFiles();
        
        return didUpdate;
 }
@@ -1712,190 +3326,190 @@ static bool updateSharedeCacheFile(const char* rootPath, const char* cacheDir, c
 
 static void usage()
 {
-       fprintf(stderr, "update_dyld_shared_cache [-force] [-root dir] [-arch arch] [-debug]\n");
-}
-
-// flag so that we only update cache once per invocation
-static bool doNothingAndDrainQueue = false;
-
-static kern_return_t do_update_cache(cpu_type_t arch, bool deleteExistingCacheFileFirst)
-{
-       if ( !doNothingAndDrainQueue ) {
-               std::set<cpu_type_t> onlyArchs;
-               onlyArchs.insert(arch);
-               try {
-                       scanForSharedDylibs("", "/var/db/dyld/shared_region_roots/", onlyArchs);
-                       if ( updateSharedeCacheFile("", DYLD_SHARED_CACHE_DIR, onlyArchs, false, false, true, deleteExistingCacheFileFirst) )
-                               fprintf(stderr, "update_dyld_shared_cache[%u] regenerated cache for arch=%s\n", getpid(), ArchGraph::archName(arch));
-               }
-               catch (const char* msg) {
-                       fprintf(stderr, "update_dyld_shared_cache[%u] for arch=%s failed: %s\n", getpid(), ArchGraph::archName(arch), msg);
-                       return KERN_FAILURE;
-               }
-       }
-       return KERN_SUCCESS;
-}
-
-
-
-kern_return_t do_dyld_shared_cache_missing(mach_port_t dyld_port, cpu_type_t arch)
-{
-       return do_update_cache(arch, false);
-}
-
-
-kern_return_t do_dyld_shared_cache_out_of_date(mach_port_t dyld_port, cpu_type_t arch)
-{
-       // If cache exists but is out of date, delete the file while building the new one.
-       // This will stop dyld from pinging update_dyld_share_cache while the cache is being built.
-       return do_update_cache(arch, true);
+       fprintf(stderr, "update_dyld_shared_cache [-force] [-root dir] [-overlay dir] [-arch arch] [-debug]\n");
 }
 
 
 int main(int argc, const char* argv[])
 {
-       mach_port_t mp;
-       if ( bootstrap_check_in(bootstrap_port, "com.apple.dyld", &mp) == KERN_SUCCESS ) {
-               // started by launchd
-               mach_msg_size_t mxmsgsz = sizeof(union __RequestUnion__do_dyld_server_subsystem) + MAX_TRAILER_SIZE;
-               doNothingAndDrainQueue = false;
-               while ( mach_msg_server(dyld_server_server, mxmsgsz, mp, MACH_RCV_TIMEOUT) == KERN_SUCCESS ) {
-                       // keep processing messages
-                       doNothingAndDrainQueue = true;
-                       // but set flag so work is no longer done.
-                       // This is because the rest of the tool leaks and processing more than once
-                       // can hog system resources: <rdar://problem/5392427> 9A516 - Keep getting disk full errors
-                       // We drain the queue of messages because there is usually are a couple of duplicate messages.
-                       // It is ok to miss some messages.  If the cache is out of date or missing, some new process
-                       // will discover it and send another message.  
-               }
-               return 0;
-       }
-       else {
-               // started as command line tool
-               std::set<cpu_type_t> onlyArchs;
-               const char* rootPath = "";
-               bool force = false;
-               bool alphaSort = false;
-               bool optimize = true;
-               bool makeSymLink = false;
+       std::set<ArchPair> onlyArchs;
+       const char* rootPath = "";
+       const char* overlayPath = "";
+       const char* dylibListFile = NULL;
+       bool force = false;
+       bool alphaSort = false;
+       bool optimize = true;
+       bool verify = false;
+       bool keepSignatures = false;
+       bool explicitCacheDir = false;
+       bool dontMapLocalSymbols = false;
+       const char* cacheDir = NULL;
        
-               try {
-                       // parse command line options
-                       for(int i=1; i < argc; ++i) {
-                               const char* arg = argv[i];
-                               if ( arg[0] == '-' ) {
-                                       if ( strcmp(arg, "-debug") == 0 ) {
-                                               verbose = true;
-                                       }
-                                       else if ( strcmp(arg, "-force") == 0 ) {
-                                               force = true;
-                                       }
-                                       else if ( strcmp(arg, "-sort_by_name") == 0 ) {
-                                               alphaSort = true;
-                                       }
-                                       else if ( strcmp(arg, "-opt") == 0 ) {
-                                               optimize = true;
-                                       }
-                                       else if ( strcmp(arg, "-no_opt") == 0 ) {
-                                               optimize = false;
-                                       }
-                                       else if ( (strcmp(arg, "-root") == 0) || (strcmp(arg, "--root") == 0) ) {
-                                               rootPath = argv[++i];
-                                               if ( rootPath == NULL )
-                                                       throw "-root missing path argument";
-                                               // strip tailing slashes
-                                               int len = strlen(rootPath)-1;
-                                               if (  rootPath[len] == '/' ) {
-                                                       char* newRootPath = strdup(rootPath);
-                                                       while ( newRootPath[len] == '/' )       
-                                                               newRootPath[len--] = '\0';
-                                                       rootPath = newRootPath;
-                                               }
-                                       }
-                                       else if ( strcmp(arg, "-arch") == 0 ) {
-                                               const char* arch = argv[++i];
-                                               if ( strcmp(arch, "ppc") == 0 ) 
-                                                       onlyArchs.insert(CPU_TYPE_POWERPC);
-                                               else if ( strcmp(arch, "ppc64") == 0 )
-                                                       onlyArchs.insert(CPU_TYPE_POWERPC64);
-                                               else if ( strcmp(arch, "i386") == 0 )
-                                                       onlyArchs.insert(CPU_TYPE_I386);
-                                               else if ( strcmp(arch, "x86_64") == 0 )
-                                                       onlyArchs.insert(CPU_TYPE_X86_64);
-                                               else 
-                                                       throwf("unknown architecture %s", arch);
-                                       }
-                                       else if ( strcmp(arg, "-universal_boot") == 0 ) {
-                               #if __ppc__
-                                               throwf("universal_boot option can only be used on Intel machines");
-                               #endif
-                                               onlyArchs.insert(CPU_TYPE_POWERPC);
-                                               onlyArchs.insert(CPU_TYPE_I386);
-                                               makeSymLink = true;
-                                       }
-                                       else {
-                                               usage();
-                                               throwf("unknown option: %s\n", arg);
-                                       }
+       try {
+               // parse command line options
+               for(int i=1; i < argc; ++i) {
+                       const char* arg = argv[i];
+                       if ( arg[0] == '-' ) {
+                               if ( strcmp(arg, "-debug") == 0 ) {
+                                       verbose = true;
+                               }
+                               else if ( strcmp(arg, "-force") == 0 ) {
+                                       force = true;
+                               }
+                               else if ( strcmp(arg, "-verify") == 0 ) {
+                                       verify = true;
+                               }
+                               else if ( strcmp(arg, "-sort_by_name") == 0 ) {
+                                       alphaSort = true;
+                               }
+                               else if ( strcmp(arg, "-progress") == 0 ) {
+                                       progress = true;
+                               }
+                               else if ( strcmp(arg, "-opt") == 0 ) {
+                                       optimize = true;
+                               }
+                               else if ( strcmp(arg, "-no_opt") == 0 ) {
+                                       optimize = false;
+                               }
+                               else if ( strcmp(arg, "-dont_map_local_symbols") == 0 ) {
+                                       dontMapLocalSymbols = true;
+                               }
+                               else if ( strcmp(arg, "-iPhone") == 0 ) {
+                                       iPhoneOS = true;
+                                       alphaSort = true;
+                               }
+                               else if ( strcmp(arg, "-dylib_list") == 0 ) {
+                                       dylibListFile = argv[++i];
+                                       if ( dylibListFile == NULL )
+                                               throw "-dylib_list missing path argument";
+                               }
+                               else if ( (strcmp(arg, "-root") == 0) || (strcmp(arg, "--root") == 0) ) {
+                                       rootPath = argv[++i];
+                                       if ( rootPath == NULL )
+                                               throw "-root missing path argument";
+                               }
+                               else if ( strcmp(arg, "-overlay") == 0 ) {
+                                       overlayPath = argv[++i];
+                                       if ( overlayPath == NULL )
+                                               throw "-overlay missing path argument";
+                               }
+                               else if ( strcmp(arg, "-cache_dir") == 0 ) {
+                                       cacheDir = argv[++i];
+                                       if ( cacheDir == NULL )
+                                               throw "-cache_dir missing path argument";
+                                       explicitCacheDir = true;
+                               }
+                               else if ( strcmp(arg, "-arch") == 0 ) {
+                                       const char* arch = argv[++i];
+                                       if ( strcmp(arch, "i386") == 0 )
+                                               onlyArchs.insert(ArchPair(CPU_TYPE_I386, CPU_SUBTYPE_I386_ALL));
+                                       else if ( strcmp(arch, "x86_64") == 0 )
+                                               onlyArchs.insert(ArchPair(CPU_TYPE_X86_64, CPU_SUBTYPE_X86_64_ALL));
+                                       else if ( strcmp(arch, "armv4t") == 0 )
+                                               onlyArchs.insert(ArchPair(CPU_TYPE_ARM, CPU_SUBTYPE_ARM_V4T));
+                                       else if ( strcmp(arch, "armv5") == 0 )
+                                               onlyArchs.insert(ArchPair(CPU_TYPE_ARM, CPU_SUBTYPE_ARM_V5TEJ));
+                                       else if ( strcmp(arch, "armv6") == 0 )
+                                               onlyArchs.insert(ArchPair(CPU_TYPE_ARM, CPU_SUBTYPE_ARM_V6));
+                                       else if ( strcmp(arch, "armv7") == 0 )
+                                               onlyArchs.insert(ArchPair(CPU_TYPE_ARM, CPU_SUBTYPE_ARM_V7));
+                                       else if ( strcmp(arch, "armv7f") == 0 )
+                                               onlyArchs.insert(ArchPair(CPU_TYPE_ARM, CPU_SUBTYPE_ARM_V7F));
+                                       else if ( strcmp(arch, "armv7k") == 0 )
+                                               onlyArchs.insert(ArchPair(CPU_TYPE_ARM, CPU_SUBTYPE_ARM_V7K));
+                                       else if ( strcmp(arch, "armv7s") == 0 )
+                                               onlyArchs.insert(ArchPair(CPU_TYPE_ARM, CPU_SUBTYPE_ARM_V7S));
+                                       else 
+                                               throwf("unknown architecture %s", arch);
+                               }
+                               else if ( strcmp(arg, "-universal_boot") == 0 ) {
+                                       onlyArchs.insert(ArchPair(CPU_TYPE_X86_64, CPU_SUBTYPE_X86_64_ALL));
+                                       onlyArchs.insert(ArchPair(CPU_TYPE_I386, CPU_SUBTYPE_I386_ALL));
                                }
                                else {
                                        usage();
                                        throwf("unknown option: %s\n", arg);
                                }
                        }
-                                       
-                       // if no restrictions specified, use architectures that work on this machine
-                       if ( onlyArchs.size() == 0 ) {
+                       else {
+                               usage();
+                               throwf("unknown option: %s\n", arg);
+                       }
+               }
+                               
+               // strip tailing slashes on -root 
+               // make it a real path so as to not make all dylibs look like symlink aliases
+               if ( rootPath[0] != '\0' ) {
+                       char realRootPath[MAXPATHLEN];
+                       if ( realpath(rootPath, realRootPath) == NULL )
+                               throwf("realpath() failed on %s\n", rootPath);
+                       rootPath = strdup(realRootPath);
+               }
+               
+               // strip tailing slashes on -overlay
+               if ( overlayPath[0] != '\0' ) {
+                       char realOverlayPath[MAXPATHLEN];
+                       if ( realpath(overlayPath, realOverlayPath) == NULL )
+                               throwf("realpath() failed on %s\n", overlayPath);
+                       overlayPath = strdup(realOverlayPath);
+               }
+
+               // set default location to write cache dir
+               if ( cacheDir == NULL ) 
+                       cacheDir = (iPhoneOS ? IPHONE_DYLD_SHARED_CACHE_DIR : MACOSX_DYLD_SHARED_CACHE_DIR);
+
+               // if no restrictions specified, use architectures that work on this machine
+               if ( onlyArchs.size() == 0 ) {
+                       if ( iPhoneOS ) {
+                               onlyArchs.insert(ArchPair(CPU_TYPE_ARM, CPU_SUBTYPE_ARM_V6));
+                               onlyArchs.insert(ArchPair(CPU_TYPE_ARM, CPU_SUBTYPE_ARM_V7));
+                       }
+                       else {
                                int available;
                                size_t len = sizeof(int);
-                       #if __ppc__     
-                               onlyArchs.insert(CPU_TYPE_POWERPC);
-                               if ( (sysctlbyname("hw.optional.64bitops", &available, &len, NULL, 0) == 0) && available )
-                                       onlyArchs.insert(CPU_TYPE_POWERPC64);
-                       #elif __i386__
-                               onlyArchs.insert(CPU_TYPE_I386);
-                               onlyArchs.insert(CPU_TYPE_POWERPC);     // assume rosetta always available
+                       #if __i386__ || __x86_64__
+                               onlyArchs.insert(ArchPair(CPU_TYPE_I386, CPU_SUBTYPE_I386_ALL));
+                               // check system is capable of running 64-bit programs
                                if ( (sysctlbyname("hw.optional.x86_64", &available, &len, NULL, 0) == 0) && available )
-                                       onlyArchs.insert(CPU_TYPE_X86_64);
+                                       onlyArchs.insert(ArchPair(CPU_TYPE_X86_64, CPU_SUBTYPE_X86_64_ALL));
                        #else
-                               #error unknown architecture
+                               #error unsupported architecture
                        #endif
                        }
-                       
-                       if ( geteuid() != 0 )
-                               throw "you must be root to run this tool";
-                       
-                       // build list of shared dylibs
-                       scanForSharedDylibs(rootPath, "/var/db/dyld/shared_region_roots/", onlyArchs);
-                       updateSharedeCacheFile(rootPath, DYLD_SHARED_CACHE_DIR, onlyArchs, force, alphaSort, optimize, false);
-                       
-                       // To make a universal bootable image with dyld caches,
-                       // build the rosetta cache and symlink ppc to point to it.
-                       // A rosetta cache is just an unoptimized ppc cache, so ppc machine can use it too.
-                       // rdar://problem/5498469
-                       if ( makeSymLink ) {
-                               char symLinkLocation[1024];
-                               strcpy(symLinkLocation, rootPath);
-                               strcat(symLinkLocation, DYLD_SHARED_CACHE_DIR);
-                               strcat(symLinkLocation, DYLD_SHARED_CACHE_BASE_NAME);
-                               strcat(symLinkLocation, SharedCache<ppc>::filename(true));
-                               char symLinkTarget[1024];
-                               strcpy(symLinkTarget, DYLD_SHARED_CACHE_BASE_NAME);
-                               strcat(symLinkTarget, SharedCache<ppc>::filename(false));
-                               if ( symlink(symLinkTarget, symLinkLocation) == -1 ) {
-                                       if ( errno != EEXIST )
-                                               throwf("symlink() returned errno=%d", errno);
-                               }
-                       }
-               }
-               catch (const char* msg) {
-                       fprintf(stderr, "update_dyld_shared_cache failed: %s\n", msg);
-                       return 1;
                }
                
-               return 0;
+               if ( !verify && (geteuid() != 0) )
+                       throw "you must be root to run this tool";
+               
+               // build list of shared dylibs
+               if ( dylibListFile != NULL )
+                       setSharedDylibs(rootPath, overlayPath, dylibListFile, onlyArchs);
+               else
+                       scanForSharedDylibs(rootPath, overlayPath, "/var/db/dyld/shared_region_roots/", onlyArchs);
+               bool didUpdate = updateSharedeCacheFile(rootPath, overlayPath, cacheDir, explicitCacheDir, onlyArchs, force, alphaSort, optimize,
+                                                               false, verify, keepSignatures, dontMapLocalSymbols);
+                                                               
+               if ( didUpdate && !iPhoneOS ) {
+                       void* handle = dlopen("/usr/lib/libspindump.dylib", RTLD_LAZY);
+                       if ( handle != NULL ) {
+                               typedef bool (*dscsym_proc_t)(const char *root);
+                               dscsym_proc_t proc = (dscsym_proc_t)dlsym(handle, "dscsym_save_nuggets_for_current_caches");
+                               const char* nuggetRootPath = "/";
+                               if ( overlayPath[0] != '\0' ) 
+                                       nuggetRootPath = overlayPath;
+                               else if ( rootPath[0] != '\0' )
+                                       nuggetRootPath = rootPath;
+                               (*proc)(nuggetRootPath);
+                       }
+                       dlclose(handle);
+               }
        }
+       catch (const char* msg) {
+               fprintf(stderr, "update_dyld_shared_cache failed: %s\n", msg);
+               return 1;
+       }
+       
+       return 0;
 }