--- dyld/dyld-95.3/src/dyld.cpp
+++ dyld/dyld-97.1/src/dyld.cpp
@@ -328,8 +328,12 @@
 //
 static void notifyAddImageCallbacks(ImageLoader* image)
 {
-	for (std::vector<ImageCallback>::iterator it=sAddImageCallbacks.begin(); it != sAddImageCallbacks.end(); it++)
-		(*it)(image->machHeader(), image->getSlide());
+	// use guard so that we cannot notify about the same image twice
+	if ( ! image->addFuncNotified() ) {
+		for (std::vector<ImageCallback>::iterator it=sAddImageCallbacks.begin(); it != sAddImageCallbacks.end(); it++)
+			(*it)(image->machHeader(), image->getSlide());
+		image->setAddFuncNotified();
+	}
 }
 
 
@@ -675,6 +679,9 @@
 
 void initializeMainExecutable()
 {
+
+	// record that we've reached this step
+	gLinkContext.startedInitializingMainExecutable = true;
 
 #if __i386__
 	// make all __IMPORT segments in the shared cache read-only
@@ -2076,6 +2083,21 @@
 	#define ARCH_CACHE_MAGIC	"dyld_v1  x86_64"
 #endif
 
+const void*	imMemorySharedCacheHeader()
+{
+	return sSharedCache;
+}
+
+int openSharedCacheFile()
+{
+#if __ppc__
+		// rosetta cannot handle optimized _ppc cache, so it use _rosetta cache instead, rdar://problem/5495438
+		if ( isRosetta() )
+			return ::open(DYLD_SHARED_CACHE_DIR DYLD_SHARED_CACHE_BASE_NAME ARCH_NAME_ROSETTA, O_RDONLY);
+		else
+#endif
+		return ::open(DYLD_SHARED_CACHE_DIR DYLD_SHARED_CACHE_BASE_NAME ARCH_NAME, O_RDONLY);
+}
 
 static void mapSharedCache()
 {	
@@ -2091,15 +2113,30 @@
 		}
 	}
 	else {
+		// <rdar://problem/5925940> Safe Boot should disable dyld shared cache
+		// if we are in safe-boot mode and the cache was not made during this boot cycle,
+		// delete the cache file and let it be regenerated 
+		uint32_t	safeBootValue = 0;
+		size_t		safeBootValueSize = sizeof(safeBootValue);
+		if ( (sysctlbyname("kern.safeboot", &safeBootValue, &safeBootValueSize, NULL, 0) == 0) && (safeBootValue != 0) ) {
+			// user booted machine in safe-boot mode
+			struct stat dyldCacheStatInfo;
+			if ( ::stat(DYLD_SHARED_CACHE_DIR DYLD_SHARED_CACHE_BASE_NAME ARCH_NAME, &dyldCacheStatInfo) == 0 ) {
+				struct timeval bootTimeValue;
+				size_t bootTimeValueSize = sizeof(bootTimeValue);
+				if ( (sysctlbyname("kern.boottime", &bootTimeValue, &bootTimeValueSize, NULL, 0) == 0) && (bootTimeValue.tv_sec != 0) ) {
+					// if the cache file was created before this boot, then throw it away and let it rebuild itself
+					if ( dyldCacheStatInfo.st_mtime < bootTimeValue.tv_sec ) {
+						::unlink(DYLD_SHARED_CACHE_DIR DYLD_SHARED_CACHE_BASE_NAME ARCH_NAME);
+						gLinkContext.sharedRegionMode = ImageLoader::kDontUseSharedRegion;
+						gSharedCacheNotFound = true;
+						return;
+					}
+				}
+			}
+		}
 		// map in shared cache to shared region
-		int fd;
-#if __ppc__
-		// rosetta cannot handle optimized _ppc cache, so it use _rosetta cache instead, rdar://problem/5495438
-		if ( isRosetta() )
-			fd = open(DYLD_SHARED_CACHE_DIR DYLD_SHARED_CACHE_BASE_NAME ARCH_NAME_ROSETTA, O_RDONLY);
-		else
-#endif
-		fd = open(DYLD_SHARED_CACHE_DIR DYLD_SHARED_CACHE_BASE_NAME ARCH_NAME, O_RDONLY);
+		int fd = openSharedCacheFile();
 		if ( fd != -1 ) {
 			uint8_t firstPage[4096];
 			if ( ::read(fd, firstPage, 4096) == 4096 ) {
@@ -2113,7 +2150,9 @@
 					if ( fstat(fd, &stat_buf) == 0 ) {
 						goodCache = true;
 						for (const shared_file_mapping_np* p = mappings; p < end; ++p) {
-							if ( p->sfm_file_offset+p->sfm_size > (uint64_t)stat_buf.st_size )
+							// rdar://problem/5694507 old update_dyld_shared_cache tool could make a cache file
+							// that is not page aligned, but otherwise ok.
+							if ( p->sfm_file_offset+p->sfm_size > (uint64_t)(stat_buf.st_size+4095 & (-4096)) )
 								goodCache = false;
 						}
 					}