Add wrapper for RDTSCP instruction

xtoskrnl/ar/i686/cpufunc.cc

@@ -255,7 +255,7 @@ AR::CpuFunc::LoadLocalDescriptorTable(IN USHORT Source)
 XTCDECL
 VOID
 AR::CpuFunc::LoadSegment(IN USHORT Segment,
-                     IN ULONG Source)
+                         IN ULONG Source)
 {
     switch(Segment)
     {
@@ -543,6 +543,33 @@ AR::CpuFunc::ReadTimeStampCounter(VOID)
     return Value;
 }
 
+/**
+ * Reads the current value of the CPU's time-stamp counter and processor ID.
+ *
+ * @param TscAux
+ *        Supplies a pointer to a variable that receives the auxiliary TSC information (IA32_TSC_AUX).
+ *
+ * @return This routine returns the current instruction cycle count since the processor was last reset.
+ *
+ * @since XT 1.0
+ */
+XTCDECL
+ULONGLONG
+AR::CpuFunc::ReadTimeStampCounterProcessor(OUT PULONG TscAux)
+{
+    ULONG Low, High;
+
+    /* Execute the RDTSCP instruction */
+    __asm__ volatile("rdtscp"
+                     : "=a" (Low),
+                       "=d" (High),
+                       "=c" (*TscAux)
+    );
+
+    /* Combine the two 32-bit registers into a single 64-bit unsigned integer and return the value */
+    return ((ULONGLONG)High << 32) | Low;
+}
+
 /**
  * Orders memory accesses as seen by other processors, without fence.
  *
@@ -650,7 +677,7 @@ AR::CpuFunc::StoreLocalDescriptorTable(OUT PVOID Destination)
 XTCDECL
 VOID
 AR::CpuFunc::StoreSegment(IN USHORT Segment,
-                      OUT PVOID Destination)
+                          OUT PVOID Destination)
 {
     switch(Segment)
     {