Implement HlReadTimeStampCounter() routine

xtoskrnl/hl/amd64/cpufunc.c

@@ -321,6 +321,26 @@ HlReadModelSpecificRegister(IN ULONG Register)
     return ((ULONGLONG)High << 32) | Low;
 }
 
+/**
+ * Reads the current value of the CPU's time-stamp counter.
+ *
+ * @return This routine returns the current instruction cycle count since the processor was started.
+ *
+ * @since XT 1.0
+ */
+XTCDECL
+ULONGLONG
+HlReadTimeStampCounter()
+{
+    ULONGLONG Low, High;
+
+    asm volatile("rdtsc"
+                 :"=a"(Low),
+                 "=d"(High));
+
+    return ((ULONGLONG)High << 32) | Low;
+}
+
 /**
  * Instructs the processor to set the interrupt flag.
  *

xtoskrnl/hl/i686/cpufunc.c

@@ -313,6 +313,25 @@ HlReadModelSpecificRegister(IN ULONG Register)
     return Value;
 }
 
+/**
+ * Reads the current value of the CPU's time-stamp counter.
+ *
+ * @return This routine returns the current instruction cycle count since the processor was started.
+ *
+ * @since XT 1.0
+ */
+XTCDECL
+ULONGLONG
+HlReadTimeStampCounter()
+{
+    ULONGLONG Value;
+
+    asm volatile("rdtsc"
+                 : "=A"(Value));
+
+    return Value;
+}
+
 /**
  * Instructs the processor to set the interrupt flag.
  *