target/s390x: Diagnose specification exception for atomics

All of the interlocked access facility instructions raise a
specification exception for unaligned accesses.  Do this by
using the (previously unused) unaligned_access hook.

Reviewed-by: Aurelien Jarno <aurelien@aurel32.net>
Signed-off-by: Richard Henderson <rth@twiddle.net>

target/s390x/cpu.c

@@ -430,6 +430,7 @@ static void s390_cpu_class_init(ObjectClass *oc, void *data)
     cc->write_elf64_note = s390_cpu_write_elf64_note;
     cc->cpu_exec_interrupt = s390_cpu_exec_interrupt;
     cc->debug_excp_handler = s390x_cpu_debug_excp_handler;
+    cc->do_unaligned_access = s390x_cpu_do_unaligned_access;
 #endif
     cc->disas_set_info = s390_cpu_disas_set_info;
 

target/s390x/cpu.h

@@ -480,6 +480,9 @@ int s390_cpu_handle_mmu_fault(CPUState *cpu, vaddr address, int rw,
 
 #ifndef CONFIG_USER_ONLY
 void do_restart_interrupt(CPUS390XState *env);
+void s390x_cpu_do_unaligned_access(CPUState *cs, vaddr addr,
+                                   MMUAccessType access_type,
+                                   int mmu_idx, uintptr_t retaddr);
 
 static inline hwaddr decode_basedisp_s(CPUS390XState *env, uint32_t ipb,
                                        uint8_t *ar)

target/s390x/helper.c

@@ -718,4 +718,20 @@ void s390x_cpu_debug_excp_handler(CPUState *cs)
         cpu_loop_exit_noexc(cs);
     }
 }
+
+/* Unaligned accesses are only diagnosed with MO_ALIGN.  At the moment,
+   this is only for the atomic operations, for which we want to raise a
+   specification exception.  */
+void s390x_cpu_do_unaligned_access(CPUState *cs, vaddr addr,
+                                   MMUAccessType access_type,
+                                   int mmu_idx, uintptr_t retaddr)
+{
+    S390CPU *cpu = S390_CPU(cs);
+    CPUS390XState *env = &cpu->env;
+
+    if (retaddr) {
+        cpu_restore_state(cs, retaddr);
+    }
+    program_interrupt(env, PGM_SPECIFICATION, ILEN_LATER);
+}
 #endif /* CONFIG_USER_ONLY */