[PATCH for 5.2 10/12] rseq/selftests: powerpc code signature: generate valid instructions

[Mathieu Desnoyers]

Use "twui" as the guard instruction for the restartable sequence abort
handler.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx>
CC: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>
CC: Paul Mackerras <paulus@xxxxxxxxx>
CC: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
CC: Boqun Feng <boqun.feng@xxxxxxxxx>
CC: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
CC: "Paul E. McKenney" <paulmck@xxxxxxxxxxxxxxxxxx>
CC: Alan Modra <amodra@xxxxxxxxx>
CC: linuxppc-dev@xxxxxxxxxxxxxxxx
---
 tools/testing/selftests/rseq/rseq-ppc.h | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/rseq/rseq-ppc.h b/tools/testing/selftests/rseq/rseq-ppc.h
index 9df18487fa9f..76be90196fe4 100644
--- a/tools/testing/selftests/rseq/rseq-ppc.h
+++ b/tools/testing/selftests/rseq/rseq-ppc.h
@@ -6,7 +6,15 @@
  * (C) Copyright 2016-2018 - Boqun Feng <boqun.feng@xxxxxxxxx>
  */
 
-#define RSEQ_SIG	0x53053053
+/*
+ * RSEQ_SIG is used with the following trap instruction:
+ *
+ * powerpc-be:    0f e5 00 0b           twui   r5,11
+ * powerpc64-le:  0b 00 e5 0f           twui   r5,11
+ * powerpc64-be:  0f e5 00 0b           twui   r5,11
+ */
+
+#define RSEQ_SIG	0x0fe5000b
 
 #define rseq_smp_mb()		__asm__ __volatile__ ("sync"	::: "memory", "cc")
 #define rseq_smp_lwsync()	__asm__ __volatile__ ("lwsync"	::: "memory", "cc")
-- 
2.11.0