[RFC PATCH for 5.2 09/10] 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 at efficios.com>
CC: Benjamin Herrenschmidt <benh at kernel.crashing.org>
CC: Paul Mackerras <paulus at samba.org>
CC: Michael Ellerman <mpe at ellerman.id.au>
CC: Boqun Feng <boqun.feng at gmail.com>
CC: Peter Zijlstra <peterz at infradead.org>
CC: "Paul E. McKenney" <paulmck at linux.vnet.ibm.com>
CC: Alan Modra <amodra at gmail.com>
CC: linuxppc-dev at lists.ozlabs.org
---
 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 at gmail.com>
  */
 
-#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