diff --git a/build/ck.build.s390x b/build/ck.build.s390x
new file mode 100644
index 0000000..5abec30
--- /dev/null
+++ b/build/ck.build.s390x
@@ -0,0 +1 @@
+CFLAGS+=-O2
diff --git a/configure b/configure
index 04eda5c..29a1f2c 100755
--- a/configure
+++ b/configure
@@ -482,6 +482,13 @@ case $PLATFORM in
 		PLATFORM=aarch64
 		ENVIRONMENT=64
 		;;
+	"s390x")
+		RTM_ENABLE="CK_MD_RTM_DISABLE"
+		LSE_ENABLE="CK_MD_LSE_DISABLE"
+		MM="${MM:-"CK_MD_RMO"}"
+		PLATFORM=s390x
+		ENVIRONMENT=64
+		;;
 	*)
 		RTM_ENABLE="CK_MD_RTM_DISABLE"
 		LSE_ENABLE="CK_MD_LSE_DISABLE"
diff --git a/include/ck_pr.h b/include/ck_pr.h
index 9b7fc42..4fdbdff 100644
--- a/include/ck_pr.h
+++ b/include/ck_pr.h
@@ -43,6 +43,8 @@
 #include "gcc/sparcv9/ck_pr.h"
 #elif defined(__ppc64__)
 #include "gcc/ppc64/ck_pr.h"
+#elif defined(__s390x__)
+#include "gcc/s390x/ck_pr.h"
 #elif defined(__ppc__)
 #include "gcc/ppc/ck_pr.h"
 #elif defined(__arm__)
diff --git a/include/gcc/s390x/ck_f_pr.h b/include/gcc/s390x/ck_f_pr.h
new file mode 100644
index 0000000..cd54a28
--- /dev/null
+++ b/include/gcc/s390x/ck_f_pr.h
@@ -0,0 +1,97 @@
+/* DO NOT EDIT. This is auto-generated from feature.sh */
+#define CK_F_PR_ADD_32
+#define CK_F_PR_ADD_64
+#define CK_F_PR_ADD_INT
+#define CK_F_PR_ADD_PTR
+#define CK_F_PR_ADD_UINT
+#define CK_F_PR_AND_32
+#define CK_F_PR_AND_64
+#define CK_F_PR_AND_INT
+#define CK_F_PR_AND_PTR
+#define CK_F_PR_AND_UINT
+#define CK_F_PR_CAS_32
+#define CK_F_PR_CAS_32_VALUE
+#define CK_F_PR_CAS_64
+#define CK_F_PR_CAS_64_VALUE
+#define CK_F_PR_CAS_INT
+#define CK_F_PR_CAS_INT_VALUE
+#define CK_F_PR_CAS_PTR
+#define CK_F_PR_CAS_PTR_VALUE
+#define CK_F_PR_CAS_UINT
+#define CK_F_PR_CAS_UINT_VALUE
+#define CK_F_PR_DEC_32
+#define CK_F_PR_DEC_64
+#define CK_F_PR_DEC_INT
+#define CK_F_PR_DEC_PTR
+#define CK_F_PR_DEC_UINT
+#define CK_F_PR_FAA_32
+#define CK_F_PR_FAA_64
+#define CK_F_PR_FAA_INT
+#define CK_F_PR_FAA_PTR
+#define CK_F_PR_FAA_UINT
+#define CK_F_PR_FAS_32
+#define CK_F_PR_FAS_64
+#define CK_F_PR_FAS_INT
+#define CK_F_PR_FAS_PTR
+#define CK_F_PR_FAS_UINT
+#define CK_F_PR_FAS_DOUBLE
+#define CK_F_PR_FENCE_LOAD
+#define CK_F_PR_FENCE_LOAD_DEPENDS
+#define CK_F_PR_FENCE_MEMORY
+#define CK_F_PR_FENCE_STORE
+#define CK_F_PR_FENCE_STRICT_LOAD
+#define CK_F_PR_FENCE_STRICT_LOAD_DEPENDS
+#define CK_F_PR_FENCE_STRICT_MEMORY
+#define CK_F_PR_FENCE_STRICT_STORE
+#define CK_F_PR_INC_32
+#define CK_F_PR_INC_64
+#define CK_F_PR_INC_INT
+#define CK_F_PR_INC_PTR
+#define CK_F_PR_INC_UINT
+#define CK_F_PR_LOAD_16
+#define CK_F_PR_LOAD_32
+#define CK_F_PR_LOAD_64
+#define CK_F_PR_LOAD_8
+#define CK_F_PR_LOAD_CHAR
+#define CK_F_PR_LOAD_DOUBLE
+#define CK_F_PR_LOAD_INT
+#define CK_F_PR_LOAD_PTR
+#define CK_F_PR_LOAD_SHORT
+#define CK_F_PR_LOAD_UINT
+#define CK_F_PR_NEG_32
+#define CK_F_PR_NEG_64
+#define CK_F_PR_NEG_INT
+#define CK_F_PR_NEG_PTR
+#define CK_F_PR_NEG_UINT
+#define CK_F_PR_NOT_32
+#define CK_F_PR_NOT_64
+#define CK_F_PR_NOT_INT
+#define CK_F_PR_NOT_PTR
+#define CK_F_PR_NOT_UINT
+#define CK_F_PR_OR_32
+#define CK_F_PR_OR_64
+#define CK_F_PR_OR_INT
+#define CK_F_PR_OR_PTR
+#define CK_F_PR_OR_UINT
+#define CK_F_PR_STALL
+#define CK_F_PR_STORE_16
+#define CK_F_PR_STORE_32
+#define CK_F_PR_STORE_64
+#define CK_F_PR_STORE_8
+#define CK_F_PR_STORE_CHAR
+#define CK_F_PR_STORE_DOUBLE
+#define CK_F_PR_STORE_INT
+#define CK_F_PR_STORE_PTR
+#define CK_F_PR_STORE_SHORT
+#define CK_F_PR_STORE_UINT
+#define CK_F_PR_SUB_32
+#define CK_F_PR_SUB_64
+#define CK_F_PR_SUB_INT
+#define CK_F_PR_SUB_PTR
+#define CK_F_PR_SUB_UINT
+#define CK_F_PR_XOR_32
+#define CK_F_PR_XOR_64
+#define CK_F_PR_XOR_INT
+#define CK_F_PR_XOR_PTR
+#define CK_F_PR_XOR_UINT
+
diff --git a/include/gcc/s390x/ck_pr.h b/include/gcc/s390x/ck_pr.h
new file mode 100644
index 0000000..8ad22b2
--- /dev/null
+++ b/include/gcc/s390x/ck_pr.h
@@ -0,0 +1,373 @@
+/*
+ * Copyright 2009-2015 Samy Al Bahra.
+ * Copyright 2017 Neale Ferguson
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#ifndef CK_PR_S390X_H
+#define CK_PR_S390X_H
+
+#ifndef CK_PR_H
+#error Do not include this file directly, use ck_pr.h
+#endif
+
+#include <ck_cc.h>
+#include <ck_md.h>
+
+/*
+ * The following represent supported atomic operations.
+ * These operations may be emulated.
+ */
+#include "ck_f_pr.h"
+
+/*
+ * Minimum interface requirement met.
+ */
+#define CK_F_PR
+
+/*
+ * This bounces the hardware thread from low to medium
+ * priority. I am unsure of the benefits of this approach
+ * but it is used by the Linux kernel.
+ */
+CK_CC_INLINE static void
+ck_pr_stall(void)
+{
+	__sync_synchronize();
+	return;
+}
+
+#define CK_PR_FENCE(T)					\
+	CK_CC_INLINE static void			\
+	ck_pr_fence_strict_##T(void)			\
+	{						\
+		__sync_synchronize();			\
+	}
+
+/*
+ * These are derived from:
+ *     http://www.ibm.com/developerworks/systems/articles/powerpc.html
+ */
+CK_PR_FENCE(atomic)
+CK_PR_FENCE(atomic_store)
+CK_PR_FENCE(atomic_load)
+CK_PR_FENCE(store_atomic)
+CK_PR_FENCE(load_atomic)
+CK_PR_FENCE(store)
+CK_PR_FENCE(store_load)
+CK_PR_FENCE(load)
+CK_PR_FENCE(load_store)
+CK_PR_FENCE(memory)
+CK_PR_FENCE(acquire)
+CK_PR_FENCE(release)
+CK_PR_FENCE(acqrel)
+CK_PR_FENCE(lock)
+CK_PR_FENCE(unlock)
+
+#undef CK_PR_FENCE
+
+#define CK_PR_LOAD(S, M, T, C, I)					\
+	CK_CC_INLINE static T						\
+	ck_pr_md_load_##S(const M *target)				\
+	{								\
+		T r;							\
+		__asm__ __volatile__(I "\t%0, %1\n"			\
+					: "=r" (r)			\
+					: "Q"  (*(const C *)target)	\
+					: "memory");			\
+		return (r);						\
+	}
+
+CK_PR_LOAD(ptr, void, void *, uint64_t, "lg")
+
+#define CK_PR_LOAD_S(S, T, I) CK_PR_LOAD(S, T, T, T, I)
+
+CK_PR_LOAD_S(64, uint64_t, "lg")
+CK_PR_LOAD_S(32, uint32_t, "llgf")
+CK_PR_LOAD_S(16, uint16_t, "llgh")
+CK_PR_LOAD_S(8, uint8_t, "llgc")
+CK_PR_LOAD_S(uint, unsigned int, "llgf")
+CK_PR_LOAD_S(int, int, "llgf")
+CK_PR_LOAD_S(short, short, "lgh")
+CK_PR_LOAD_S(char, char, "lgb")
+#ifndef CK_PR_DISABLE_DOUBLE
+CK_CC_INLINE static double
+ck_pr_md_load_double(const double *target)
+{
+	double r;
+	__asm__ __volatile__("ld  %0, %1\n"
+				: "=f" (r)
+				: "Q"  (*(const double *)target)   
+				: "memory");
+	return (r);			
+}
+#endif
+
+#undef CK_PR_LOAD_S
+#undef CK_PR_LOAD
+
+#define CK_PR_STORE(S, M, T, C, I)				\
+	CK_CC_INLINE static void				\
+	ck_pr_md_store_##S(M *target, T v)			\
+	{							\
+		__asm__ __volatile__(I "\t%1, %0\n"		\
+					: "=Q" (*(C *)target)	\
+					: "r" (v)		\
+					: "memory");		\
+		return;						\
+	}
+
+CK_PR_STORE(ptr, void, const void *, uint64_t, "stg")
+
+#define CK_PR_STORE_S(S, T, I) CK_PR_STORE(S, T, T, T, I)
+
+CK_PR_STORE_S(64, uint64_t, "stg")
+CK_PR_STORE_S(32, uint32_t, "st")
+CK_PR_STORE_S(16, uint16_t, "sth")
+CK_PR_STORE_S(8, uint8_t, "stc")
+CK_PR_STORE_S(uint, unsigned int, "st")
+CK_PR_STORE_S(int, int, "st")
+CK_PR_STORE_S(short, short, "sth")
+CK_PR_STORE_S(char, char, "stc")
+#ifndef CK_PR_DISABLE_DOUBLE
+CK_CC_INLINE static void
+ck_pr_md_store_double(double *target, double v)
+{
+	__asm__ __volatile__(" std  %1, %0\n"
+				: "=Q" (*(double *)target)   
+				: "f"  (v)
+				: "0", "memory");
+}
+#endif
+
+#undef CK_PR_STORE_S
+#undef CK_PR_STORE
+
+CK_CC_INLINE static bool
+ck_pr_cas_64_value(uint64_t *target, uint64_t compare, uint64_t set, uint64_t *value)
+{
+	*value = __sync_val_compare_and_swap(target,compare,set);
+        return (*value == compare);
+}
+
+CK_CC_INLINE static bool
+ck_pr_cas_ptr_value(void *target, void *compare, void *set, void *value)
+{
+	uintptr_t previous;
+
+	previous = __sync_val_compare_and_swap((uintptr_t *) target,
+					       (uintptr_t) compare,
+					       (uintptr_t) set);
+	*((uintptr_t *) value) = previous;
+        return (previous == (uintptr_t) compare);
+}
+
+CK_CC_INLINE static bool
+ck_pr_cas_64(uint64_t *target, uint64_t compare, uint64_t set)
+{
+	return(__sync_bool_compare_and_swap(target,compare,set));
+}
+
+CK_CC_INLINE static bool
+ck_pr_cas_ptr(void *target, void *compare, void *set)
+{
+	return(__sync_bool_compare_and_swap((uintptr_t *) target,
+					    (uintptr_t) compare,
+					    (uintptr_t) set));
+}
+
+#define CK_PR_CAS(N, T)							\
+	CK_CC_INLINE static bool					\
+	ck_pr_cas_##N##_value(T *target, T compare, T set, T *value)	\
+	{								\
+		*value = __sync_val_compare_and_swap(target,		\
+						     compare,		\
+						     set);		\
+		return(*value == compare);				\
+	}								\
+	CK_CC_INLINE static bool					\
+	ck_pr_cas_##N(T *target, T compare, T set)			\
+	{								\
+		return(__sync_bool_compare_and_swap(target,		\
+						   compare,		\
+						   set));		\
+	}
+
+CK_PR_CAS(32, uint32_t)
+CK_PR_CAS(uint, unsigned int)
+CK_PR_CAS(int, int)
+
+#undef CK_PR_CAS
+
+CK_CC_INLINE static void *
+ck_pr_fas_ptr(void *target, void *v)
+{
+	return((void *)__atomic_exchange_n((uintptr_t *) target, (uintptr_t) v, __ATOMIC_ACQUIRE));
+}
+
+#define CK_PR_FAS(N, M, T)							\
+	CK_CC_INLINE static T							\
+	ck_pr_fas_##N(M *target, T v)						\
+	{									\
+		return(__atomic_exchange_n(target, v, __ATOMIC_ACQUIRE));	\
+	}
+
+CK_PR_FAS(64, uint64_t, uint64_t)
+CK_PR_FAS(32, uint32_t, uint32_t)
+CK_PR_FAS(int, int, int)
+CK_PR_FAS(uint, unsigned int, unsigned int)
+
+#ifndef CK_PR_DISABLE_DOUBLE
+CK_CC_INLINE static double
+ck_pr_fas_double(double *target, double *v)
+{
+	double previous;
+
+	__asm__ __volatile__ ("	   lg   1,%2\n"
+			      "0:  lg	0,%1\n"
+			      "    csg	0,1,%1\n"
+			      "    jnz	0b\n"
+			      "    ldgr %0,0\n"
+			      : "=f" (previous) 
+			      : "Q" (target), "Q" (v)
+			      : "0", "1", "cc", "memory");
+	return (previous);
+}
+#endif
+
+#undef CK_PR_FAS
+
+/*
+ * Atomic store-only binary operations.
+ */
+#define CK_PR_BINARY(K, S, M, T)				\
+	CK_CC_INLINE static void				\
+	ck_pr_##K##_##S(M *target, T d)				\
+	{							\
+		d = __sync_fetch_and_##K((T *)target, d);	\
+		return;						\
+	}
+
+#define CK_PR_BINARY_S(K, S, T) CK_PR_BINARY(K, S, T, T)
+
+#define CK_PR_GENERATE(K)			\
+	CK_PR_BINARY(K, ptr, void, void *)	\
+	CK_PR_BINARY_S(K, char, char)		\
+	CK_PR_BINARY_S(K, int, int)		\
+	CK_PR_BINARY_S(K, uint, unsigned int)	\
+	CK_PR_BINARY_S(K, 64, uint64_t)		\
+	CK_PR_BINARY_S(K, 32, uint32_t)		\
+	CK_PR_BINARY_S(K, 16, uint16_t)		\
+	CK_PR_BINARY_S(K, 8, uint8_t)
+
+CK_PR_GENERATE(add)
+CK_PR_GENERATE(sub)
+CK_PR_GENERATE(and)
+CK_PR_GENERATE(or)
+CK_PR_GENERATE(xor)
+
+#undef CK_PR_GENERATE
+#undef CK_PR_BINARY_S
+#undef CK_PR_BINARY
+
+#define CK_PR_UNARY(S, M, T)			\
+	CK_CC_INLINE static void		\
+	ck_pr_inc_##S(M *target)		\
+	{					\
+		ck_pr_add_##S(target, (T)1);	\
+		return;				\
+	}					\
+	CK_CC_INLINE static void		\
+	ck_pr_dec_##S(M *target)		\
+	{					\
+		ck_pr_sub_##S(target, (T)1);	\
+		return;				\
+	}
+
+#define CK_PR_UNARY_X(S, M) 	  					\
+	CK_CC_INLINE static void					\
+	ck_pr_not_##S(M *target)					\
+	{								\
+		M newval;						\
+		do {							\
+			newval = ~(*target);				\
+		} while (!__sync_bool_compare_and_swap(target, 		\
+						      *target,		\
+						      newval));		\
+	}								\
+	CK_CC_INLINE static void					\
+	ck_pr_neg_##S(M *target)					\
+	{								\
+		M newval;						\
+		do {							\
+			newval = -(*target);				\
+		} while (!__sync_bool_compare_and_swap(target, 		\
+						      *target,		\
+						      newval));		\
+	}								
+
+#define CK_PR_UNARY_S(S, M) CK_PR_UNARY(S, M, M) \
+			    CK_PR_UNARY_X(S, M)
+
+CK_PR_UNARY(ptr, void, void *)
+CK_PR_UNARY_S(char, char)
+CK_PR_UNARY_S(int, int)
+CK_PR_UNARY_S(uint, unsigned int)
+CK_PR_UNARY_S(64, uint64_t)
+CK_PR_UNARY_S(32, uint32_t)
+CK_PR_UNARY_S(16, uint16_t)
+CK_PR_UNARY_S(8, uint8_t)
+
+#undef CK_PR_UNARY_S
+#undef CK_PR_UNARY
+
+CK_CC_INLINE static void *
+ck_pr_faa_ptr(void *target, uintptr_t delta)
+{
+	uintptr_t previous;
+
+	previous = __sync_fetch_and_add((uintptr_t *) target, delta);
+
+	return (void *)(previous);
+}
+
+#define CK_PR_FAA(S, T)							\
+	CK_CC_INLINE static T						\
+	ck_pr_faa_##S(T *target, T delta)				\
+	{								\
+		T previous;						\
+									\
+		previous = __sync_fetch_and_add(target, delta);		\
+									\
+		return (previous);					\
+	}
+
+CK_PR_FAA(64, uint64_t)
+CK_PR_FAA(32, uint32_t)
+CK_PR_FAA(uint, unsigned int)
+CK_PR_FAA(int, int)
+
+#undef CK_PR_FAA
+
+#endif /* CK_PR_S390X_H */
diff --git a/src/ck_ht_hash.h b/src/ck_ht_hash.h
index cd3d7a5..532fa0e 100644
--- a/src/ck_ht_hash.h
+++ b/src/ck_ht_hash.h
@@ -88,7 +88,15 @@ static inline uint64_t rotl64 ( uint64_t x, int8_t r )
 
 FORCE_INLINE static uint32_t getblock ( const uint32_t * p, int i )
 {
+#if __s390x__
+  uint32_t res;
+
+  __asm__ ("	lrv	%0,%1\n"
+	   : "=r" (res) : "Q" (p[i]) : "cc", "mem");
+  return res;
+#else
   return p[i];
+#endif
 }
 
 //-----------------------------------------------------------------------------