Re: [PATCH for 5.2 07/12] rseq/selftests: s390: use trap4 for RSEQ_SIG

[shuah]

Hi Mathieu,

On 4/29/19 9:27 AM, Mathieu Desnoyers wrote:
> From: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>
>
> Use trap4 as the guard instruction for the restartable sequence abort
> handler.
>
> Signed-off-by: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>
> Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx>
> ---
>   tools/testing/selftests/rseq/rseq-s390.h | 9 ++++++++-
>   1 file changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/tools/testing/selftests/rseq/rseq-s390.h b/tools/testing/selftests/rseq/rseq-s390.h
> index 7c4f3a70b6c7..1d05c5187ae6 100644
> --- a/tools/testing/selftests/rseq/rseq-s390.h
> +++ b/tools/testing/selftests/rseq/rseq-s390.h
> @@ -1,6 +1,13 @@
>   /* SPDX-License-Identifier: LGPL-2.1 OR MIT */
>   
> -#define RSEQ_SIG	0x53053053
> +/*
> + * RSEQ_SIG uses the trap4 instruction. As Linux does not make use of the
> + * access-register mode nor the linkage stack this instruction will always
> + * cause a special-operation exception (the trap-enabled bit in the DUCT
> + * is and will stay 0). The instruction pattern is
> + *	b2 ff 0f ff	trap4   4095(%r0)
> + */
> +#define RSEQ_SIG	0xB2FF0FFF
>   
>   #define rseq_smp_mb()	__asm__ __volatile__ ("bcr 15,0" ::: "memory")
>   #define rseq_smp_rmb()	rseq_smp_mb()

I generated my pull request for Linus and did a sanity check and ran
into merge conflict on this patch. Looks like this is already in
Linus's tree.

Can you confirm!

I have to drop this patch and regenerate my pull request. Can you
confirm!

thanks,
-- Shuah