logd: Allow apps to clear their UID-specific data

Bug: 13501501
Change-Id: Ia72e25fc19430ce63fb359cd9b3f0523d41f5aa8

logd/CommandListener.cpp

@@ -74,9 +74,9 @@ static void setname() {
 int CommandListener::ClearCmd::runCommand(SocketClient *cli,
                                          int argc, char **argv) {
     setname();
-    if (!clientHasLogCredentials(cli)) {
-        cli->sendMsg("Permission Denied");
-        return 0;
+    uid_t uid = cli->getUid();
+    if (clientHasLogCredentials(cli)) {
+        uid = AID_ROOT;
     }
 
     if (argc < 2) {
@@ -90,7 +90,7 @@ int CommandListener::ClearCmd::runCommand(SocketClient *cli,
         return 0;
     }
 
-    mBuf.clear((log_id_t) id);
+    mBuf.clear((log_id_t) id, uid);
     cli->sendMsg("success");
     return 0;
 }

logd/LogBuffer.cpp

@@ -232,7 +232,7 @@ void LogBuffer::maybePrune(log_id_t id) {
 // prune "pruneRows" of type "id" from the buffer.
 //
 // mLogElementsLock must be held when this function is called.
-void LogBuffer::prune(log_id_t id, unsigned long pruneRows) {
+void LogBuffer::prune(log_id_t id, unsigned long pruneRows, uid_t caller_uid) {
     LogTimeEntry *oldest = NULL;
 
     LogTimeEntry::lock();
@@ -250,6 +250,38 @@ void LogBuffer::prune(log_id_t id, unsigned long pruneRows) {
 
     LogBufferElementCollection::iterator it;
 
+    if (caller_uid != AID_ROOT) {
+        for(it = mLogElements.begin(); it != mLogElements.end();) {
+            LogBufferElement *e = *it;
+
+            if (oldest && (oldest->mStart <= e->getMonotonicTime())) {
+                break;
+            }
+
+            if (e->getLogId() != id) {
+                ++it;
+                continue;
+            }
+
+            uid_t uid = e->getUid();
+
+            if (uid == caller_uid) {
+                it = mLogElements.erase(it);
+                unsigned short len = e->getMsgLen();
+                stats.subtract(len, id, uid, e->getPid());
+                delete e;
+                pruneRows--;
+                if (pruneRows == 0) {
+                    break;
+                }
+            } else {
+                ++it;
+            }
+        }
+        LogTimeEntry::unlock();
+        return;
+    }
+
     // prune by worst offender by uid
     while (pruneRows > 0) {
         // recalculate the worst offender on every batched pass
@@ -375,9 +407,9 @@ void LogBuffer::prune(log_id_t id, unsigned long pruneRows) {
 }
 
 // clear all rows of type "id" from the buffer.
-void LogBuffer::clear(log_id_t id) {
+void LogBuffer::clear(log_id_t id, uid_t uid) {
     pthread_mutex_lock(&mLogElementsLock);
-    prune(id, ULONG_MAX);
+    prune(id, ULONG_MAX, uid);
     pthread_mutex_unlock(&mLogElementsLock);
 }
 

logd/LogBuffer.h

@@ -23,6 +23,8 @@
 #include <sysutils/SocketClient.h>
 #include <utils/List.h>
 
+#include <private/android_filesystem_config.h>
+
 #include "LogBufferElement.h"
 #include "LogTimes.h"
 #include "LogStatistics.h"
@@ -55,7 +57,7 @@ public:
                      bool (*filter)(const LogBufferElement *element, void *arg) = NULL,
                      void *arg = NULL);
 
-    void clear(log_id_t id);
+    void clear(log_id_t id, uid_t uid = AID_ROOT);
     unsigned long getSize(log_id_t id);
     int setSize(log_id_t id, unsigned long size);
     unsigned long getSizeUsed(log_id_t id);
@@ -77,7 +79,7 @@ public:
 
 private:
     void maybePrune(log_id_t id);
-    void prune(log_id_t id, unsigned long pruneRows);
+    void prune(log_id_t id, unsigned long pruneRows, uid_t uid = AID_ROOT);
 
 };