Commit 16b96b6e authored Apr 29, 2019 by Mathieu Desnoyers Committed by Shuah Khan May 07, 2019

rseq/selftests: mips: use break instruction for RSEQ_SIG



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.

Suggested-by: Paul Burton <paul.burton@mips.com>
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
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

parent 496fd0fc

tools/testing/selftests/rseq/rseq-mips.h

+33 −1

Original line number	Diff line number	Diff line
		@@ -7,7 +7,39 @@
		* (C) Copyright 2016-2018 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
		*/

		#define RSEQ_SIG 0x53053053
		/*
		* RSEQ_SIG uses the break instruction. The instruction pattern is:
		*
		* On MIPS:
		* 0350000d break 0x350
		*
		* On nanoMIPS:
		* 00100350 break 0x350
		*
		* On microMIPS:
		* 0000d407 break 0x350
		*
		* For nanoMIPS32 and microMIPS, the instruction stream is encoded as 16-bit
		* halfwords, so the signature halfwords need to be swapped accordingly for
		* little-endian.
		*/
		#if defined(__nanomips__)
		# ifdef __MIPSEL__
		# define RSEQ_SIG 0x03500010
		# else
		# define RSEQ_SIG 0x00100350
		# endif
		#elif defined(__mips_micromips)
		# ifdef __MIPSEL__
		# define RSEQ_SIG 0xd4070000
		# else
		# define RSEQ_SIG 0x0000d407
		# endif
		#elif defined(__mips__)
		# define RSEQ_SIG 0x0350000d
		#else
		/* Unknown MIPS architecture. */
		#endif

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

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