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Subject[RFC PATCH for 5.2 10/10] rseq/selftests: mips: use break instruction for RSEQ_SIG
Date
Use break as guard instruction for the restartable sequence abort
handler.

Previously, the chosen signature was simply data, based on the
assumption that it could always sit in a literal pool. However,
some compilation environments favor disabling literal pool. Therefore,
ensure the signature is a valid uncommon trap instruction.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
CC: Paul Burton <paul.burton@mips.com>
CC: James Hogan <jhogan@kernel.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
---
tools/testing/selftests/rseq/rseq-mips.h | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/rseq/rseq-mips.h b/tools/testing/selftests/rseq/rseq-mips.h
index fe3eabcdcbe5..eb53a6adfbbb 100644
--- a/tools/testing/selftests/rseq/rseq-mips.h
+++ b/tools/testing/selftests/rseq/rseq-mips.h
@@ -7,7 +7,11 @@
* (C) Copyright 2016-2018 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
*/

-#define RSEQ_SIG 0x53053053
+/*
+ * RSEQ_SIG uses the break instruction. The instruction pattern is
+ * 0350000d break 0x350
+ */
+#define RSEQ_SIG 0x0350000d

#define rseq_smp_mb() __asm__ __volatile__ ("sync" ::: "memory")
#define rseq_smp_rmb() rseq_smp_mb()
--
2.11.0
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