The "system instructions" and "system register move" subcategories
of "branches, exception generating and system instructions" for A64
only apply if bits [23:22] are zero; other values are currently
unallocated. Correctly UNDEF these unallocated encodings.

Reported-by: Laurent Desnogues <laurent.desnogues@gmail.com>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
 target/arm/translate-a64.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/target/arm/translate-a64.c b/target/arm/translate-a64.c
index 4d28a27c3bd..e6df303e321 100644
--- a/target/arm/translate-a64.c
+++ b/target/arm/translate-a64.c
@@ -2144,7 +2144,11 @@ static void disas_b_exc_sys(DisasContext *s, uint32_t insn)
         break;
     case 0x6a: /* Exception generation / System */
         if (insn & (1 << 24)) {
-            disas_system(s, insn);
+            if (extract32(insn, 22, 2) == 0) {
+                disas_system(s, insn);
+            } else {
+                unallocated_encoding(s);
+            }
         } else {
             disas_exc(s, insn);
         }
-- 
2.20.1

On Fri, Jan 25, 2019 at 7:26 PM Peter Maydell <peter.maydell@linaro.org> wrote:
>
> The "system instructions" and "system register move" subcategories
> of "branches, exception generating and system instructions" for A64
> only apply if bits [23:22] are zero; other values are currently
> unallocated. Correctly UNDEF these unallocated encodings.
>
> Reported-by: Laurent Desnogues <laurent.desnogues@gmail.com>
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

Reviewed-by: Laurent Desnogues <laurent.desnogues@gmail.com>

Thanks,

Laurent

> ---
>  target/arm/translate-a64.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/target/arm/translate-a64.c b/target/arm/translate-a64.c
> index 4d28a27c3bd..e6df303e321 100644
> --- a/target/arm/translate-a64.c
> +++ b/target/arm/translate-a64.c
> @@ -2144,7 +2144,11 @@ static void disas_b_exc_sys(DisasContext *s, uint32_t insn)
>          break;
>      case 0x6a: /* Exception generation / System */
>          if (insn & (1 << 24)) {
> -            disas_system(s, insn);
> +            if (extract32(insn, 22, 2) == 0) {
> +                disas_system(s, insn);
> +            } else {
> +                unallocated_encoding(s);
> +            }
>          } else {
>              disas_exc(s, insn);
>          }
> --
> 2.20.1
>