3 files changed, 46 insertions, 15 deletions

diff --git a/src/arch/arm/nativetrace.cc b/src/arch/arm/nativetrace.cc
index 469869e56..7c9c70e0c 100644
--- a/src/arch/arm/nativetrace.cc
+++ b/src/arch/arm/nativetrace.cc
@@ -51,10 +51,31 @@ Trace::ArmNativeTrace::ThreadState::update(NativeTrace *parent)
     current = (current + 1) % 2;
     newState = state[current];
 
-    parent->read(newState, sizeof(newState[0]) * STATE_NUMVALS);
+    memcpy(newState, oldState, sizeof(state[0]));
+
+    uint32_t diffVector;
+    parent->read(&diffVector, sizeof(diffVector));
+    diffVector = ArmISA::gtoh(diffVector);
+
+    int changes = 0;
     for (int i = 0; i < STATE_NUMVALS; i++) {
-        newState[i] = ArmISA::gtoh(newState[i]);
-        changed[i] = (oldState[i] != newState[i]);
+        if (diffVector & 0x1) {
+            changed[i] = true;
+            changes++;
+        } else {
+            changed[i] = false;
+        }
+        diffVector >>= 1;
+    }
+
+    uint32_t values[changes];
+    parent->read(values, sizeof(values));
+    int pos = 0;
+    for (int i = 0; i < STATE_NUMVALS; i++) {
+        if (changed[i]) {
+            newState[i] = ArmISA::gtoh(values[pos++]);
+            changed[i] = (newState[i] != oldState[i]);
+        }
     }
 }
 
diff --git a/util/statetrace/arch/tracechild_arm.cc b/util/statetrace/arch/tracechild_arm.cc
index fc2eb3e24..4687b46f0 100644
--- a/util/statetrace/arch/tracechild_arm.cc
+++ b/util/statetrace/arch/tracechild_arm.cc
@@ -46,23 +46,38 @@ const char* ARMTraceChild::regNames[numregs] = {
 
 ARMTraceChild::ARMTraceChild()
 {
-    for (int x = 0; x < numregs; x++)
+    for (int x = 0; x < numregs; x++) {
+        memset(&regs, 0, sizeof(regs));
+        memset(&oldregs, 0, sizeof(regs));
         regDiffSinceUpdate[x] = false;
+    }
 }
 
 bool ARMTraceChild::sendState(int socket)
 {
     uint32_t regVal = 0;
-    for(int x = 0; x < numregs; x++)
-    {
-        regVal = getRegVal(x);
-        if(write(socket, &regVal, sizeof(regVal)) == -1)
-        {
+    uint32_t message[numregs + 1];
+    int pos = 1;
+    message[0] = 0;
+    for (int x = 0; x < numregs; x++) {
+        if (regDiffSinceUpdate[x]) {
+            message[0] = message[0] | (1 << x);
+            message[pos++] = getRegVal(x);
+        }
+    }
+
+    size_t sent = 0;
+    size_t toSend = pos * sizeof(message[0]);
+    uint8_t *messagePtr = (uint8_t *)message;
+    while (toSend != 0) {
+        sent = write(socket, messagePtr, toSend);
+        if (sent == -1) {
             cerr << "Write failed! " << strerror(errno) << endl;
             tracing = false;
             return false;
         }
-      
+        toSend -= sent;
+        messagePtr += sent;
     }
     
     return true;
diff --git a/util/statetrace/tracechild.cc b/util/statetrace/tracechild.cc
index 52e19a0e9..85f42addd 100644
--- a/util/statetrace/tracechild.cc
+++ b/util/statetrace/tracechild.cc
@@ -79,11 +79,6 @@ bool TraceChild::startTracing(const char * pathToFile, char * const argv[])
                 return false;
         }
         tracing = true;
-        if(!update(pid))
-        {
-                cout << "Didn't update successfully!" << endl;
-                return false;
-        }
         return true;
 }