diff -up haveged-1.3/configure.ac.s390 haveged-1.3/configure.ac
--- haveged-1.3/configure.ac.s390	2011-11-25 10:33:44.784760266 -0500
+++ haveged-1.3/configure.ac	2011-11-25 10:34:02.044760923 -0500
@@ -93,6 +93,10 @@ case "$host" in
     HA_CPPFLAGS="-DHAVE_ISA_SPARC"
  ;;
 
+ s390*-*)
+    HA_CPPFLAGS="-DHAVE_ISA_S390"
+ ;;
+
  *)
     echo "Unsupported host: $host";
     exit 1
diff -up haveged-1.3/configure.s390 haveged-1.3/configure
--- haveged-1.3/configure.s390	2011-11-25 10:49:45.334762435 -0500
+++ haveged-1.3/configure	2011-11-25 10:37:49.964754934 -0500
@@ -4585,6 +4585,10 @@ case "$host" in
     HA_CPPFLAGS="-DHAVE_ISA_SPARC"
  ;;
 
+ s390*-*)
+    HA_CPPFLAGS="-DHAVE_ISA_S390"
+ ;;
+
  *)
     echo "Unsupported host: $host";
     exit 1
diff -up haveged-1.3/src/havegecollect.h.s390 haveged-1.3/src/havegecollect.h
--- haveged-1.3/src/havegecollect.h.s390	2011-11-25 10:34:13.574761327 -0500
+++ haveged-1.3/src/havegecollect.h	2011-11-25 10:35:30.934753116 -0500
@@ -122,6 +122,11 @@ unsigned int havege_collect(volatile H_P
 #define HARDCLOCK(x) ASM("mftb %0":"=r"(x)) /* eq. to mftb %0, 268 */
 #endif
 
+#ifdef HAVE_ISA_S390
+#define ARCH "s390"
+#define HARDCLOCK(x) { unsigned long long tsc; ASM("stck %0":"=Q"(tsc)::"cc"); x = (unsigned int)tsc; }
+#endif
+
 #ifdef HAVE_ISA_IA64
 #define ARCH "ia64"
 #define CPUID(op,reg) ASM("mov %0=cpuid[%1]"\