--- dyld/dyld-1162/common/DyldSharedCache.cpp
+++ dyld/dyld-1122.1/common/DyldSharedCache.cpp
@@ -282,40 +282,6 @@
     }
 }
 
-const char* DyldSharedCache::mappingName(uint32_t maxProt, uint64_t flags)
-{
-    const char* mappingName = "";
-    if ( maxProt & VM_PROT_EXECUTE ) {
-        if ( flags & DYLD_CACHE_MAPPING_TEXT_STUBS ) {
-            mappingName = "__TEXT_STUBS";
-        } else {
-            mappingName = "__TEXT";
-        }
-    } else if ( maxProt & VM_PROT_WRITE ) {
-        if ( flags & DYLD_CACHE_MAPPING_AUTH_DATA ) {
-            if ( flags & DYLD_CACHE_MAPPING_DIRTY_DATA )
-                mappingName = "__AUTH_DIRTY";
-            else if ( flags & DYLD_CACHE_MAPPING_CONST_DATA )
-                mappingName = "__AUTH_CONST";
-            else
-                mappingName = "__AUTH";
-        } else {
-            if ( flags & DYLD_CACHE_MAPPING_DIRTY_DATA )
-                mappingName = "__DATA_DIRTY";
-            else if ( flags & DYLD_CACHE_MAPPING_CONST_DATA )
-                mappingName = "__DATA_CONST";
-            else
-                mappingName = "__DATA";
-        }
-    }
-    else if ( maxProt & VM_PROT_READ ) {
-        mappingName = "__LINKEDIT";
-    } else {
-        mappingName = "*unknown*";
-    }
-    return mappingName;
-}
-
 void DyldSharedCache::forEachRange(void (^handler)(const char* mappingName,
                                                    uint64_t unslidVMAddr, uint64_t vmSize,
                                                    uint32_t cacheFileIndex, uint64_t fileOffset,
@@ -327,7 +293,35 @@
     forEachCache(^(const DyldSharedCache *cache, bool& stopCache) {
         cache->forEachRegion(^(const void *content, uint64_t unslidVMAddr, uint64_t size,
                         uint32_t initProt, uint32_t maxProt, uint64_t flags, bool& stopRegion) {
-            const char* mappingName = DyldSharedCache::mappingName(maxProt, flags);
+            const char* mappingName = "";
+            if ( maxProt & VM_PROT_EXECUTE ) {
+                if ( flags & DYLD_CACHE_MAPPING_TEXT_STUBS ) {
+                    mappingName = "__TEXT_STUBS";
+                } else {
+                    mappingName = "__TEXT";
+                }
+            } else if ( maxProt & VM_PROT_WRITE ) {
+                if ( flags & DYLD_CACHE_MAPPING_AUTH_DATA ) {
+                    if ( flags & DYLD_CACHE_MAPPING_DIRTY_DATA )
+                        mappingName = "__AUTH_DIRTY";
+                    else if ( flags & DYLD_CACHE_MAPPING_CONST_DATA )
+                        mappingName = "__AUTH_CONST";
+                    else
+                        mappingName = "__AUTH";
+                } else {
+                    if ( flags & DYLD_CACHE_MAPPING_DIRTY_DATA )
+                        mappingName = "__DATA_DIRTY";
+                    else if ( flags & DYLD_CACHE_MAPPING_CONST_DATA )
+                        mappingName = "__DATA_CONST";
+                    else
+                        mappingName = "__DATA";
+                }
+            }
+            else if ( maxProt & VM_PROT_READ ) {
+                mappingName = "__LINKEDIT";
+            } else {
+                mappingName = "*unknown*";
+            }
             uint64_t fileOffset = (uint8_t*)content - (uint8_t*)cache;
             bool stop = false;
             handler(mappingName, unslidVMAddr, size, cacheFileIndex, fileOffset, initProt, maxProt, stop);
@@ -413,7 +407,7 @@
     }
 }
 
-bool DyldSharedCache::inCache(const void* addr, size_t length, bool& immutable) const
+bool DyldSharedCache::inCache(const void* addr, size_t length, bool& readOnly) const
 {
     // quick out if before start of cache
     if ( addr < this )
@@ -423,19 +417,22 @@
     uintptr_t slide = (uintptr_t)this - (uintptr_t)(mappings[0].address);
     uintptr_t unslidStart = (uintptr_t)addr - slide;
 
-    // walk cache ranges
-    __block bool found = false;
-    auto inRange = ^(const char* mappingName, uint64_t unslidVMAddr, uint64_t vmSize, uint32_t cacheFileIndex,
-                     uint64_t fileOffset, uint32_t initProt, uint32_t maxProt, bool& stopRange) {
-        if ( (unslidVMAddr <= unslidStart) && ((unslidStart+length) < (unslidVMAddr+vmSize)) ) {
-            found     = true;
-            immutable = ((maxProt & VM_PROT_WRITE) == 0);
-            stopRange = true;
-        }
-    };
-    this->forEachRange(inRange, nullptr);
-
-    return found;
+    // quick out if after end of cache
+    const dyld_cache_mapping_info* lastMapping = &mappings[header.mappingCount - 1];
+    if ( unslidStart > (lastMapping->address + lastMapping->size) )
+        return false;
+
+    // walk cache regions
+    const dyld_cache_mapping_info* mappingsEnd = &mappings[header.mappingCount];
+    uintptr_t unslidEnd = unslidStart + length;
+    for (const dyld_cache_mapping_info* m=mappings; m < mappingsEnd; ++m) {
+        if ( (unslidStart >= m->address) && (unslidEnd < (m->address+m->size)) ) {
+            readOnly = ((m->initProt & VM_PROT_WRITE) == 0);
+            return true;
+        }
+    }
+
+    return false;
 }
 
 bool DyldSharedCache::isAlias(const char* path) const {