diff --git a/executor/executor.cc b/executor/executor.cc
index ab8ae3d6c553..19aa45e814de 100644
--- a/executor/executor.cc
+++ b/executor/executor.cc
@@ -95,6 +95,7 @@ const int kOutFd = 4;
 static uint32* output_data;
 static uint32* output_pos;
 static uint32* write_output(uint32 v);
+static uint32* write_output_64(uint64 v);
 static void write_completed(uint32 completed);
 static uint32 hash(uint32 a);
 static bool dedup(uint32 sig);
@@ -1308,6 +1309,15 @@ uint32* write_output(uint32 v)
 	return output_pos++;
 }
 
+uint32* write_output_64(uint64 v)
+{
+	if (output_pos < output_data || (char*)(output_pos + 1) >= (char*)output_data + kMaxOutput)
+		fail("output overflow: pos=%p region=[%p:%p]",
+		     output_pos, output_data, (char*)output_data + kMaxOutput);
+	*(uint64*)output_pos = v;
+	return output_pos + 2;
+}
+
 void write_completed(uint32 completed)
 {
 	__atomic_store_n(output_data, completed, __ATOMIC_RELEASE);
@@ -1344,13 +1354,10 @@ void kcov_comparison_t::write()
 	if (!is_size_8) {
 		write_output((uint32)arg1);
 		write_output((uint32)arg2);
-		return;
+	} else {
+		write_output_64(arg1);
+		write_output_64(arg2);
 	}
-	// If we have 64 bits arguments then write them in Little-endian.
-	write_output((uint32)(arg1 & 0xFFFFFFFF));
-	write_output((uint32)(arg1 >> 32));
-	write_output((uint32)(arg2 & 0xFFFFFFFF));
-	write_output((uint32)(arg2 >> 32));
 }
 
 bool kcov_comparison_t::ignore() const
diff --git a/executor/executor_linux.h b/executor/executor_linux.h
index 47804f4f4f73..98b89fc9a9d5 100644
--- a/executor/executor_linux.h
+++ b/executor/executor_linux.h
@@ -167,8 +167,10 @@ static void cover_reset(cover_t* cov)
 
 static void cover_collect(cover_t* cov)
 {
-	// Note: this assumes little-endian kernel.
-	cov->size = *(uint32*)cov->data;
+	if (is_kernel_64_bit)
+		cov->size = *(uint64*)cov->data;
+	else
+		cov->size = *(uint32*)cov->data;
 }
 
 static bool cover_check(uint32 pc)
diff --git a/executor/test.h b/executor/test.h
index 1f940eb714b5..0d3587b849f2 100644
--- a/executor/test.h
+++ b/executor/test.h
@@ -8,7 +8,7 @@
 static int test_copyin()
 {
 	static uint16 buf[3];
-	STORE_BY_BITMASK(uint16, , &buf[1], 0x1234, 0, 16);
+	STORE_BY_BITMASK(uint16, htole16, &buf[1], 0x1234, 0, 16);
 	unsigned char x[sizeof(buf)];
 	memcpy(x, buf, sizeof(x));
 	if (x[0] != 0 || x[1] != 0 ||
@@ -18,7 +18,7 @@ static int test_copyin()
 		       x[0], x[1], x[2], x[3], x[4], x[5]);
 		return 1;
 	}
-	STORE_BY_BITMASK(uint16, , &buf[1], 0x555a, 5, 4);
+	STORE_BY_BITMASK(uint16, htole16, &buf[1], 0x555a, 5, 4);
 	memcpy(x, buf, sizeof(x));
 	if (x[0] != 0 || x[1] != 0 ||
 	    x[2] != 0x54 || x[3] != 0x13 ||
diff --git a/pkg/ipc/ipc.go b/pkg/ipc/ipc.go
index f6aa20855e16..1abab7f5ef71 100644
--- a/pkg/ipc/ipc.go
+++ b/pkg/ipc/ipc.go
@@ -4,7 +4,6 @@
 package ipc
 
 import (
-	"encoding/binary"
 	"fmt"
 	"io"
 	"io/ioutil"
@@ -439,7 +438,7 @@ func readUint32(outp *[]byte) (uint32, bool) {
 	if len(out) < 4 {
 		return 0, false
 	}
-	v := binary.LittleEndian.Uint32(out)
+	v := prog.HostEndian.Uint32(out)
 	*outp = out[4:]
 	return v, true
 }
@@ -449,7 +448,7 @@ func readUint64(outp *[]byte) (uint64, bool) {
 	if len(out) < 8 {
 		return 0, false
 	}
-	v := binary.LittleEndian.Uint64(out)
+	v := prog.HostEndian.Uint64(out)
 	*outp = out[8:]
 	return v, true
 }
diff --git a/prog/big_endian.go b/prog/big_endian.go
new file mode 100644
index 000000000000..1f9ebfffebd0
--- /dev/null
+++ b/prog/big_endian.go
@@ -0,0 +1,10 @@
+// Copyright 2020 syzkaller project authors. All rights reserved.
+// Use of this source code is governed by Apache 2 LICENSE that can be found in the LICENSE file.
+
+// +build s390x
+
+package prog
+
+import "encoding/binary"
+
+var HostEndian = binary.BigEndian
diff --git a/prog/decodeexec.go b/prog/decodeexec.go
index 57f08d0fceae..e2ef2586c352 100644
--- a/prog/decodeexec.go
+++ b/prog/decodeexec.go
@@ -203,10 +203,7 @@ func (dec *execDecoder) read() uint64 {
 	if dec.err != nil {
 		return 0
 	}
-	var v uint64
-	for i := 0; i < 8; i++ {
-		v |= uint64(dec.data[i]) << uint(i*8)
-	}
+	v := HostEndian.Uint64(dec.data)
 	dec.data = dec.data[8:]
 	return v
 }
diff --git a/prog/encodingexec.go b/prog/encodingexec.go
index 78eae81ae888..2295bb72e1c6 100644
--- a/prog/encodingexec.go
+++ b/prog/encodingexec.go
@@ -20,6 +20,8 @@
 package prog
 
 import (
+	"bytes"
+	"encoding/binary"
 	"fmt"
 	"sort"
 )
@@ -221,14 +223,9 @@ func (w *execContext) write(v uint64) {
 		w.eof = true
 		return
 	}
-	w.buf[0] = byte(v >> 0)
-	w.buf[1] = byte(v >> 8)
-	w.buf[2] = byte(v >> 16)
-	w.buf[3] = byte(v >> 24)
-	w.buf[4] = byte(v >> 32)
-	w.buf[5] = byte(v >> 40)
-	w.buf[6] = byte(v >> 48)
-	w.buf[7] = byte(v >> 56)
+	buf := new(bytes.Buffer)
+	binary.Write(buf, HostEndian, v)
+	copy(w.buf, buf.Bytes())
 	w.buf = w.buf[8:]
 }
 
diff --git a/prog/encodingexec_test.go b/prog/encodingexec_test.go
index 141cf5dda698..7cda63cc06bf 100644
--- a/prog/encodingexec_test.go
+++ b/prog/encodingexec_test.go
@@ -42,6 +42,18 @@ func TestSerializeForExec(t *testing.T) {
 		}
 		return uint64(c.ID)
 	}
+	letoh64 := func(v uint64) uint64 {
+		buf := make([]byte, 8)
+		buf[0] = byte(v >> 0)
+		buf[1] = byte(v >> 8)
+		buf[2] = byte(v >> 16)
+		buf[3] = byte(v >> 24)
+		buf[4] = byte(v >> 32)
+		buf[5] = byte(v >> 40)
+		buf[6] = byte(v >> 48)
+		buf[7] = byte(v >> 56)
+		return HostEndian.Uint64(buf)
+	}
 	tests := []struct {
 		prog       string
 		serialized []uint64
@@ -204,7 +216,7 @@ func TestSerializeForExec(t *testing.T) {
 			"test$array1(&(0x7f0000000000)={0x42, \"0102030405\"})",
 			[]uint64{
 				execInstrCopyin, dataOffset + 0, execArgConst, 1, 0x42,
-				execInstrCopyin, dataOffset + 1, execArgData, 5, 0x0504030201,
+				execInstrCopyin, dataOffset + 1, execArgData, 5, letoh64(0x0504030201),
 				callID("test$array1"), ExecNoCopyout, 1, execArgConst, ptrSize, dataOffset,
 				execInstrEOF,
 			},
@@ -214,7 +226,7 @@ func TestSerializeForExec(t *testing.T) {
 			"test$array2(&(0x7f0000000000)={0x42, \"aaaaaaaabbbbbbbbccccccccdddddddd\", 0x43})",
 			[]uint64{
 				execInstrCopyin, dataOffset + 0, execArgConst, 2, 0x42,
-				execInstrCopyin, dataOffset + 2, execArgData, 16, 0xbbbbbbbbaaaaaaaa, 0xddddddddcccccccc,
+				execInstrCopyin, dataOffset + 2, execArgData, 16, letoh64(0xbbbbbbbbaaaaaaaa), letoh64(0xddddddddcccccccc),
 				execInstrCopyin, dataOffset + 18, execArgConst, 2, 0x43,
 				callID("test$array2"), ExecNoCopyout, 1, execArgConst, ptrSize, dataOffset,
 				execInstrEOF,
@@ -436,8 +448,7 @@ func TestSerializeForExec(t *testing.T) {
 				execInstrCopyin, dataOffset + 2, execArgConst, 4 | 1<<8, 0x1,
 				execInstrCopyin, dataOffset + 6, execArgConst, 4 | 1<<8, 0x2,
 				execInstrCopyin, dataOffset + 10, execArgConst, 2, 0x0,
-				execInstrCopyin, dataOffset + 12, execArgData, 1, 0xab,
-
+				execInstrCopyin, dataOffset + 12, execArgData, 1, letoh64(0xab),
 				execInstrCopyin, dataOffset + 10, execArgCsum, 2, ExecArgCsumInet, 5,
 				ExecArgCsumChunkData, dataOffset + 2, 4,
 				ExecArgCsumChunkData, dataOffset + 6, 4,
@@ -466,11 +477,11 @@ func TestSerializeForExec(t *testing.T) {
 				t.Fatalf("failed to serialize: %v", err)
 			}
 			w := new(bytes.Buffer)
-			binary.Write(w, binary.LittleEndian, test.serialized)
+			binary.Write(w, HostEndian, test.serialized)
 			data := buf[:n]
 			if !bytes.Equal(data, w.Bytes()) {
 				got := make([]uint64, len(data)/8)
-				binary.Read(bytes.NewReader(data), binary.LittleEndian, &got)
+				binary.Read(bytes.NewReader(data), HostEndian, &got)
 				t.Logf("want: %v", test.serialized)
 				t.Logf("got:  %v", got)
 				t.Fatalf("mismatch")
diff --git a/prog/little_endian.go b/prog/little_endian.go
new file mode 100644
index 000000000000..4403926576f4
--- /dev/null
+++ b/prog/little_endian.go
@@ -0,0 +1,10 @@
+// Copyright 2020 syzkaller project authors. All rights reserved.
+// Use of this source code is governed by Apache 2 LICENSE that can be found in the LICENSE file.
+
+// +build amd64 386 arm64 arm mips64le ppc64le
+
+package prog
+
+import "encoding/binary"
+
+var HostEndian = binary.LittleEndian