Factor out and speed up permission-checking code

Use the caching permission check for dump to save IPC.

Cache getpid() to save kernel call for other permission checks.

The C runtime library getpid() can't cache due to a fork
race condition, but we know that mediaserver doesn't fork.

Don't construct String16 on the stack.

Change-Id: I6be6161dae5155d39ba6ed6228e7683e67be34ed

5 files changed, 97 insertions, 33 deletions

diff --git a/services/audioflinger/Android.mk b/services/audioflinger/Android.mk
index deeb2de..157405a 100644
--- a/services/audioflinger/Android.mk
+++ b/services/audioflinger/Android.mk
@@ -6,7 +6,8 @@ LOCAL_SRC_FILES:=               \
     AudioFlinger.cpp            \
     AudioMixer.cpp.arm          \
     AudioResampler.cpp.arm      \
-    AudioPolicyService.cpp
+    AudioPolicyService.cpp      \
+    ServiceUtilities.cpp
 #   AudioResamplerSinc.cpp.arm
 #   AudioResamplerCubic.cpp.arm
 
diff --git a/services/audioflinger/AudioFlinger.cpp b/services/audioflinger/AudioFlinger.cpp
index bbc9196..5c964b2 100644
--- a/services/audioflinger/AudioFlinger.cpp
+++ b/services/audioflinger/AudioFlinger.cpp
@@ -48,6 +48,7 @@
 
 #include "AudioMixer.h"
 #include "AudioFlinger.h"
+#include "ServiceUtilities.h"
 
 #include <media/EffectsFactoryApi.h>
 #include <audio_effects/effect_visualizer.h>
@@ -101,20 +102,6 @@ static const uint32_t kMaxThreadSleepTimeShift = 2;
 
 // ----------------------------------------------------------------------------
 
-static bool recordingAllowed() {
-    if (getpid() == IPCThreadState::self()->getCallingPid()) return true;
-    bool ok = checkCallingPermission(String16("android.permission.RECORD_AUDIO"));
-    if (!ok) ALOGE("Request requires android.permission.RECORD_AUDIO");
-    return ok;
-}
-
-static bool settingsAllowed() {
-    if (getpid() == IPCThreadState::self()->getCallingPid()) return true;
-    bool ok = checkCallingPermission(String16("android.permission.MODIFY_AUDIO_SETTINGS"));
-    if (!ok) ALOGE("Request requires android.permission.MODIFY_AUDIO_SETTINGS");
-    return ok;
-}
-
 // To collect the amplifier usage
 static void addBatteryData(uint32_t params) {
     sp<IMediaPlayerService> service = IMediaDeathNotifier::getMediaPlayerService();
@@ -321,7 +308,7 @@ static bool tryLock(Mutex& mutex)
 
 status_t AudioFlinger::dump(int fd, const Vector<String16>& args)
 {
-    if (!checkCallingPermission(String16("android.permission.DUMP"))) {
+    if (!dumpAllowed()) {
         dumpPermissionDenial(fd, args);
     } else {
         // get state of hardware lock
@@ -3436,7 +3423,7 @@ void AudioFlinger::PlaybackThread::Track::dump(char* buffer, size_t size)
     uint32_t vlr = mCblk->getVolumeLR();
     snprintf(buffer, size, "   %05d %05d %03u %03u 0x%08x %05u   %04u %1d %1d %1d %05u %05u %05u  0x%08x 0x%08x 0x%08x 0x%08x\n",
             mName - AudioMixer::TRACK0,
-            (mClient == 0) ? getpid() : mClient->pid(),
+            (mClient == 0) ? getpid_cached : mClient->pid(),
             mStreamType,
             mFormat,
             mChannelMask,
@@ -3757,7 +3744,7 @@ void AudioFlinger::RecordThread::RecordTrack::stop()
 void AudioFlinger::RecordThread::RecordTrack::dump(char* buffer, size_t size)
 {
     snprintf(buffer, size, "   %05d %03u 0x%08x %05d   %04u %01d %05u  %08x %08x\n",
-            (mClient == 0) ? getpid() : mClient->pid(),
+            (mClient == 0) ? getpid_cached : mClient->pid(),
             mFormat,
             mChannelMask,
             mSessionId,
@@ -5404,7 +5391,7 @@ sp<IEffect> AudioFlinger::createEffect(pid_t pid,
 
     // Session AUDIO_SESSION_OUTPUT_STAGE is reserved for output stage effects
     // that can only be created by audio policy manager (running in same process)
-    if (sessionId == AUDIO_SESSION_OUTPUT_STAGE && getpid() != pid) {
+    if (sessionId == AUDIO_SESSION_OUTPUT_STAGE && getpid_cached != pid) {
         lStatus = PERMISSION_DENIED;
         goto Exit;
     }
@@ -7022,7 +7009,7 @@ void AudioFlinger::EffectHandle::dump(char* buffer, size_t size)
     bool locked = mCblk != NULL && tryLock(mCblk->lock);
 
     snprintf(buffer, size, "\t\t\t%05d %05d    %01u    %01u      %05u  %05u\n",
-            (mClient == 0) ? getpid() : mClient->pid(),
+            (mClient == 0) ? getpid_cached : mClient->pid(),
             mPriority,
             mHasControl,
             !locked,
diff --git a/services/audioflinger/AudioPolicyService.cpp b/services/audioflinger/AudioPolicyService.cpp
index f8b430e..21b5811 100644
--- a/services/audioflinger/AudioPolicyService.cpp
+++ b/services/audioflinger/AudioPolicyService.cpp
@@ -30,6 +30,7 @@
 #include <utils/String16.h>
 #include <utils/threads.h>
 #include "AudioPolicyService.h"
+#include "ServiceUtilities.h"
 #include <cutils/properties.h>
 #include <hardware_legacy/power.h>
 #include <media/AudioEffect.h>
@@ -49,13 +50,6 @@ static const char kCmdDeadlockedString[] = "AudioPolicyService command thread ma
 static const int kDumpLockRetries = 50;
 static const int kDumpLockSleepUs = 20000;
 
-static bool checkPermission() {
-    if (getpid() == IPCThreadState::self()->getCallingPid()) return true;
-    bool ok = checkCallingPermission(String16("android.permission.MODIFY_AUDIO_SETTINGS"));
-    if (!ok) ALOGE("Request requires android.permission.MODIFY_AUDIO_SETTINGS");
-    return ok;
-}
-
 namespace {
     extern struct audio_policy_service_ops aps_ops;
 };
@@ -157,7 +151,7 @@ status_t AudioPolicyService::setDeviceConnectionState(audio_devices_t device,
     if (mpAudioPolicy == NULL) {
         return NO_INIT;
     }
-    if (!checkPermission()) {
+    if (!settingsAllowed()) {
         return PERMISSION_DENIED;
     }
     if (!audio_is_output_device(device) && !audio_is_input_device(device)) {
@@ -190,7 +184,7 @@ status_t AudioPolicyService::setPhoneState(audio_mode_t state)
     if (mpAudioPolicy == NULL) {
         return NO_INIT;
     }
-    if (!checkPermission()) {
+    if (!settingsAllowed()) {
         return PERMISSION_DENIED;
     }
     if (uint32_t(state) >= AUDIO_MODE_CNT) {
@@ -213,7 +207,7 @@ status_t AudioPolicyService::setForceUse(audio_policy_force_use_t usage,
     if (mpAudioPolicy == NULL) {
         return NO_INIT;
     }
-    if (!checkPermission()) {
+    if (!settingsAllowed()) {
         return PERMISSION_DENIED;
     }
     if (usage < 0 || usage >= AUDIO_POLICY_FORCE_USE_CNT) {
@@ -388,7 +382,7 @@ status_t AudioPolicyService::initStreamVolume(audio_stream_type_t stream,
     if (mpAudioPolicy == NULL) {
         return NO_INIT;
     }
-    if (!checkPermission()) {
+    if (!settingsAllowed()) {
         return PERMISSION_DENIED;
     }
     if (uint32_t(stream) >= AUDIO_STREAM_CNT) {
@@ -405,7 +399,7 @@ status_t AudioPolicyService::setStreamVolumeIndex(audio_stream_type_t stream,
     if (mpAudioPolicy == NULL) {
         return NO_INIT;
     }
-    if (!checkPermission()) {
+    if (!settingsAllowed()) {
         return PERMISSION_DENIED;
     }
     if (uint32_t(stream) >= AUDIO_STREAM_CNT) {
@@ -578,7 +572,7 @@ status_t AudioPolicyService::dumpInternals(int fd)
 
 status_t AudioPolicyService::dump(int fd, const Vector<String16>& args)
 {
-    if (!checkCallingPermission(String16("android.permission.DUMP"))) {
+    if (!dumpAllowed()) {
         dumpPermissionDenial(fd);
     } else {
         bool locked = tryLock(mLock);
diff --git a/services/audioflinger/ServiceUtilities.cpp b/services/audioflinger/ServiceUtilities.cpp
new file mode 100644
index 0000000..6a58852
--- /dev/null
+++ b/services/audioflinger/ServiceUtilities.cpp
@@ -0,0 +1,55 @@
+/*
+ * Copyright (C) 2012 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.
+ */
+
+#include <binder/IPCThreadState.h>
+#include <binder/IServiceManager.h>
+#include <binder/PermissionCache.h>
+#include "ServiceUtilities.h"
+
+namespace android {
+
+// This optimization assumes mediaserver process doesn't fork, which it doesn't
+const pid_t getpid_cached = getpid();
+
+bool recordingAllowed() {
+    if (getpid_cached == IPCThreadState::self()->getCallingPid()) return true;
+    static const String16 sRecordAudio("android.permission.RECORD_AUDIO");
+    // don't use PermissionCache; this is not a system permission
+    bool ok = checkCallingPermission(sRecordAudio);
+    if (!ok) ALOGE("Request requires android.permission.RECORD_AUDIO");
+    return ok;
+}
+
+bool settingsAllowed() {
+    if (getpid_cached == IPCThreadState::self()->getCallingPid()) return true;
+    static const String16 sAudioSettings("android.permission.MODIFY_AUDIO_SETTINGS");
+    // don't use PermissionCache; this is not a system permission
+    bool ok = checkCallingPermission(sAudioSettings);
+    if (!ok) ALOGE("Request requires android.permission.MODIFY_AUDIO_SETTINGS");
+    return ok;
+}
+
+bool dumpAllowed() {
+    // don't optimize for same pid, since mediaserver never dumps itself
+    static const String16 sDump("android.permission.DUMP");
+    // OK to use PermissionCache; this is a system permission
+    bool ok = PermissionCache::checkCallingPermission(sDump);
+    // convention is for caller to dump an error message to fd instead of logging here
+    //if (!ok) ALOGE("Request requires android.permission.DUMP");
+    return ok;
+}
+
+} // namespace android
diff --git a/services/audioflinger/ServiceUtilities.h b/services/audioflinger/ServiceUtilities.h
new file mode 100644
index 0000000..f77ec5b
--- /dev/null
+++ b/services/audioflinger/ServiceUtilities.h
@@ -0,0 +1,27 @@
+/*
+ * Copyright (C) 2012 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.
+ */
+
+#include <unistd.h>
+
+namespace android {
+
+extern const pid_t getpid_cached;
+
+bool recordingAllowed();
+bool settingsAllowed();
+bool dumpAllowed();
+
+}