Generate a specification exception in the helper before trying to fetch
the instruction.

Reported-by: Nina Schoetterl-Glausch <nsg@linux.ibm.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
---
 target/s390x/tcg/mem_helper.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/target/s390x/tcg/mem_helper.c b/target/s390x/tcg/mem_helper.c
index 6835c26dda4..9d1c4bb7374 100644
--- a/target/s390x/tcg/mem_helper.c
+++ b/target/s390x/tcg/mem_helper.c
@@ -2468,8 +2468,16 @@ void HELPER(stpq_parallel)(CPUS390XState *env, uint64_t addr,
 */
 void HELPER(ex)(CPUS390XState *env, uint32_t ilen, uint64_t r1, uint64_t addr)
 {
-    uint64_t insn = cpu_lduw_code(env, addr);
-    uint8_t opc = insn >> 8;
+    uint64_t insn;
+    uint8_t opc;
+
+    /* EXECUTE targets must be at even addresses.  */
+    if (addr & 1) {
+        tcg_s390_program_interrupt(env, PGM_SPECIFICATION, GETPC());
+    }
+
+    insn = cpu_lduw_code(env, addr);
+    opc = insn >> 8;
 
     /* Or in the contents of R1[56:63].  */
     insn |= r1 & 0xff;
-- 
2.39.2