diff --git a/libs/binder/PermissionCache.cpp b/libs/binder/PermissionCache.cpp
new file mode 100644
index 0000000..7278187
--- /dev/null
+++ b/libs/binder/PermissionCache.cpp
@@ -0,0 +1,113 @@
+/*
+ * Copyright (C) 2009 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#define LOG_TAG "PermissionCache"
+
+#include <stdint.h>
+#include <utils/Log.h>
+#include <binder/IPCThreadState.h>
+#include <binder/IServiceManager.h>
+#include <binder/PermissionCache.h>
+#include <utils/String8.h>
+
+namespace android {
+
+// ----------------------------------------------------------------------------
+
+ANDROID_SINGLETON_STATIC_INSTANCE(PermissionCache) ;
+
+// ----------------------------------------------------------------------------
+
+PermissionCache::PermissionCache() {
+}
+
+status_t PermissionCache::check(bool* granted,
+        const String16& permission, uid_t uid) const {
+    Mutex::Autolock _l(mLock);
+    Entry e;
+    e.name = permission;
+    e.uid  = uid;
+    ssize_t index = mCache.indexOf(e);
+    if (index >= 0) {
+        *granted = mCache.itemAt(index).granted;
+        return NO_ERROR;
+    }
+    return NAME_NOT_FOUND;
+}
+
+void PermissionCache::cache(const String16& permission,
+        uid_t uid, bool granted) {
+    Mutex::Autolock _l(mLock);
+    Entry e;
+    ssize_t index = mPermissionNamesPool.indexOf(permission);
+    if (index > 0) {
+        e.name = mPermissionNamesPool.itemAt(index);
+    } else {
+        mPermissionNamesPool.add(permission);
+        e.name = permission;
+    }
+    // note, we don't need to store the pid, which is not actually used in
+    // permission checks
+    e.uid  = uid;
+    e.granted = granted;
+    index = mCache.indexOf(e);
+    if (index < 0) {
+        mCache.add(e);
+    }
+}
+
+void PermissionCache::purge() {
+    Mutex::Autolock _l(mLock);
+    mCache.clear();
+}
+
+bool PermissionCache::checkCallingPermission(const String16& permission) {
+    return PermissionCache::checkCallingPermission(permission, NULL, NULL);
+}
+
+bool PermissionCache::checkCallingPermission(
+        const String16& permission, int32_t* outPid, int32_t* outUid) {
+    IPCThreadState* ipcState = IPCThreadState::self();
+    pid_t pid = ipcState->getCallingPid();
+    uid_t uid = ipcState->getCallingUid();
+    if (outPid) *outPid = pid;
+    if (outUid) *outUid = uid;
+    return PermissionCache::checkPermission(permission, pid, uid);
+}
+
+bool PermissionCache::checkPermission(
+        const String16& permission, pid_t pid, uid_t uid) {
+    if ((uid == 0) || (pid == getpid())) {
+        // root and ourselves is always okay
+        return true;
+    }
+
+    PermissionCache& pc(PermissionCache::getInstance());
+    bool granted = false;
+    if (pc.check(&granted, permission, uid) != NO_ERROR) {
+        nsecs_t t = -systemTime();
+        granted = android::checkPermission(permission, pid, uid);
+        t += systemTime();
+        LOGD("checking %s for uid=%d => %s (%d us)",
+                String8(permission).string(), uid,
+                granted?"granted":"denied", (int)ns2us(t));
+        pc.cache(permission, uid, granted);
+    }
+    return granted;
+}
+
+// ---------------------------------------------------------------------------
+}; // namespace android