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

----- On May 16, 2019, at 4:39 PM, shuah shuah@kernel.org wrote:

Hi Mathieu,

On 4/29/19 9:27 AM, Mathieu Desnoyers wrote:

quoted

From: Martin Schwidefsky <redacted>

Use trap4 as the guard instruction for the restartable sequence abort
handler.

Signed-off-by: Martin Schwidefsky <redacted>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
---
  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!

I confirm, it went through the s390 maintainer tree, here is the
upstream commit already in Linus' master:

commit e24e4712efad737ca09ff299276737331cd021d9
Author: Martin Schwidefsky [off-list ref]
Date:   Wed Apr 10 12:28:41 2019 +0200

    s390/rseq: use trap4 for RSEQ_SIG
    
    Use trap4 as the guard instruction for the restartable sequence abort
    handler.
    
    Signed-off-by: Martin Schwidefsky [off-list ref]

So you can either drop it from your end of the pull request, or Linus will
deal with the merge, as you prefer.

Thanks!

Mathieu

thanks,
-- Shuah

-- 
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com