Re: [risu PATCH 1/4] s390x: Add basic s390x support to the C code

[Ilya Leoshkevich <iii@linux.ibm.com>]

On Mon, 2023-09-04 at 16:00 +0200, Thomas Huth wrote:
> With these changes, it is now possible to compile the "risu" binary
> for s390x hosts.
> 
> Signed-off-by: Thomas Huth <thuth@redhat.com>
> ---
>  risu_reginfo_s390x.c | 142
> +++++++++++++++++++++++++++++++++++++++++++
>  risu_reginfo_s390x.h |  23 +++++++
>  risu_s390x.c         |  48 +++++++++++++++
>  test_s390x.S         |  32 ++++++++++
>  4 files changed, 245 insertions(+)
>  create mode 100644 risu_reginfo_s390x.c
>  create mode 100644 risu_reginfo_s390x.h
>  create mode 100644 risu_s390x.c
>  create mode 100644 test_s390x.S

Looks really interesting! I was doing similar qemu-system-s390x testing
with a bunch of ad-hoc scripts, and there are quite a few unresolved
problems still, especially in the error handling area.

Acked-by: Ilya Leoshkevich <iii@linux.ibm.com>

I have one small question (see below).

[...]

> +/* reginfo_is_eq: compare the reginfo structs, returns nonzero if
> equal */
> +int reginfo_is_eq(struct reginfo *m, struct reginfo *a)
> +{
> +    int i;
> +
> +    if (m->psw_mask != a->psw_mask || m->psw_addr != a->psw_addr) {
> +        return 0;
> +    }
> +
> +    /* Skip return address register and stack register for
> comparison */

Is this because of ASLR? In this case, would it be possible to build a
non-PIE binary and switch to a private stack at the beginning? This
could be useful for the other architectures as well.

[...]