PermissionCache caches permission checks

This is intended to absorb the cost of the IPC
to the permission controller.
Cached permission checks cost about 3us, while
full blown ones are two orders of magnitude slower.

CAVEAT: PermissionCache can only handle system
permissions safely for now, because the cache is
not purged upon global permission changes.

Change-Id: I8b8a5e71e191e3c01e8f792f253c379190eee62e

1 files changed, 16 insertions, 10 deletions

diff --git a/services/surfaceflinger/SurfaceFlinger.cpp b/services/surfaceflinger/SurfaceFlinger.cpp
index 97edfee..f0b19f2 100644
--- a/services/surfaceflinger/SurfaceFlinger.cpp
+++ b/services/surfaceflinger/SurfaceFlinger.cpp
@@ -32,6 +32,7 @@
 #include <binder/IPCThreadState.h>
 #include <binder/IServiceManager.h>
 #include <binder/MemoryHeapBase.h>
+#include <binder/PermissionCache.h>
 
 #include <utils/String8.h>
 #include <utils/String16.h>
@@ -67,6 +68,13 @@
 namespace android {
 // ---------------------------------------------------------------------------
 
+const String16 sHardwareTest("android.permission.HARDWARE_TEST");
+const String16 sAccessSurfaceFlinger("android.permission.ACCESS_SURFACE_FLINGER");
+const String16 sReadFramebuffer("android.permission.READ_FRAME_BUFFER");
+const String16 sDump("android.permission.DUMP");
+
+// ---------------------------------------------------------------------------
+
 SurfaceFlinger::SurfaceFlinger()
     :   BnSurfaceComposer(), Thread(false),
         mTransactionFlags(0),
@@ -74,10 +82,6 @@ SurfaceFlinger::SurfaceFlinger()
         mResizeTransationPending(false),
         mLayersRemoved(false),
         mBootTime(systemTime()),
-        mHardwareTest("android.permission.HARDWARE_TEST"),
-        mAccessSurfaceFlinger("android.permission.ACCESS_SURFACE_FLINGER"),
-        mReadFramebuffer("android.permission.READ_FRAME_BUFFER"),
-        mDump("android.permission.DUMP"),
         mVisibleRegionsDirty(false),
         mHwWorkListDirty(false),
         mDeferReleaseConsole(false),
@@ -1464,7 +1468,8 @@ status_t SurfaceFlinger::dump(int fd, const Vector<String16>& args)
     const size_t SIZE = 4096;
     char buffer[SIZE];
     String8 result;
-    if (!mDump.checkCalling()) {
+
+    if (!PermissionCache::checkCallingPermission(sDump)) {
         snprintf(buffer, SIZE, "Permission Denial: "
                 "can't dump SurfaceFlinger from pid=%d, uid=%d\n",
                 IPCThreadState::self()->getCallingPid(),
@@ -1596,7 +1601,8 @@ status_t SurfaceFlinger::onTransact(
             IPCThreadState* ipc = IPCThreadState::self();
             const int pid = ipc->getCallingPid();
             const int uid = ipc->getCallingUid();
-            if ((uid != AID_GRAPHICS) && !mAccessSurfaceFlinger.check(pid, uid)) {
+            if ((uid != AID_GRAPHICS) &&
+                    !PermissionCache::checkPermission(sAccessSurfaceFlinger, pid, uid)) {
                 LOGE("Permission Denial: "
                         "can't access SurfaceFlinger pid=%d, uid=%d", pid, uid);
                 return PERMISSION_DENIED;
@@ -1609,7 +1615,8 @@ status_t SurfaceFlinger::onTransact(
             IPCThreadState* ipc = IPCThreadState::self();
             const int pid = ipc->getCallingPid();
             const int uid = ipc->getCallingUid();
-            if ((uid != AID_GRAPHICS) && !mReadFramebuffer.check(pid, uid)) {
+            if ((uid != AID_GRAPHICS) &&
+                    !PermissionCache::checkPermission(sReadFramebuffer, pid, uid)) {
                 LOGE("Permission Denial: "
                         "can't read framebuffer pid=%d, uid=%d", pid, uid);
                 return PERMISSION_DENIED;
@@ -1621,7 +1628,7 @@ status_t SurfaceFlinger::onTransact(
     status_t err = BnSurfaceComposer::onTransact(code, data, reply, flags);
     if (err == UNKNOWN_TRANSACTION || err == PERMISSION_DENIED) {
         CHECK_INTERFACE(ISurfaceComposer, data, reply);
-        if (UNLIKELY(!mHardwareTest.checkCalling())) {
+        if (UNLIKELY(!PermissionCache::checkCallingPermission(sHardwareTest))) {
             IPCThreadState* ipc = IPCThreadState::self();
             const int pid = ipc->getCallingPid();
             const int uid = ipc->getCallingUid();
@@ -2404,8 +2411,7 @@ status_t Client::onTransact(
      const int self_pid = getpid();
      if (UNLIKELY(pid != self_pid && uid != AID_GRAPHICS && uid != 0)) {
          // we're called from a different process, do the real check
-         if (!checkCallingPermission(
-                 String16("android.permission.ACCESS_SURFACE_FLINGER")))
+         if (!PermissionCache::checkCallingPermission(sAccessSurfaceFlinger))
          {
              LOGE("Permission Denial: "
                      "can't openGlobalTransaction pid=%d, uid=%d", pid, uid);