logd: filter on __android_log_is_loggable

(cherry pick from commit e59c469fa8)

- Default level when not specified is ANDROID_LOG_VERBOSE
  which is inert.

Bug: 20416721
Bug: 19544788
Bug: 17760225
Change-Id: Icc098e53dc47ceaaeb24ec42eb6f61d6430ec2f6

logd/LogBuffer.cpp

@@ -140,8 +140,26 @@ int LogBuffer::log(log_id_t log_id, log_time realtime,
     if ((log_id >= LOG_ID_MAX) || (log_id < 0)) {
         return -EINVAL;
     }
+
     LogBufferElement *elem = new LogBufferElement(log_id, realtime,
                                                   uid, pid, tid, msg, len);
+    int prio = ANDROID_LOG_INFO;
+    const char *tag = NULL;
+    if (log_id == LOG_ID_EVENTS) {
+        tag = android::tagToName(elem->getTag());
+    } else {
+        prio = *msg;
+        tag = msg + 1;
+    }
+    if (!__android_log_is_loggable(prio, tag, ANDROID_LOG_VERBOSE)) {
+        // Log traffic received to total
+        pthread_mutex_lock(&mLogElementsLock);
+        stats.add(elem);
+        stats.subtract(elem);
+        pthread_mutex_unlock(&mLogElementsLock);
+        delete elem;
+        return -EACCES;
+    }
 
     pthread_mutex_lock(&mLogElementsLock);
 

logd/LogBufferElement.cpp

@@ -105,8 +105,12 @@ char *android::tidToName(pid_t tid) {
 size_t LogBufferElement::populateDroppedMessage(char *&buffer,
         LogBuffer *parent) {
     static const char tag[] = "chatty";
-    static const char format_uid[] = "uid=%u%s%s expire %u line%s";
 
+    if (!__android_log_is_loggable(ANDROID_LOG_INFO, tag, ANDROID_LOG_VERBOSE)) {
+        return 0;
+    }
+
+    static const char format_uid[] = "uid=%u%s%s expire %u line%s";
     char *name = parent->uidToName(mUid);
     char *commName = android::tidToName(mTid);
     if (!commName && (mTid != mPid)) {