linux-kernel - [PATCH 2/4] MIPS: Add syscall detection for restartable sequences

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Date:   Thu, 14 Jun 2018 16:52:08 -0700
From:   Paul Burton <paul.burton@...s.com>
To:     <linux-mips@...ux-mips.org>
CC:     Peter Zijlstra <peterz@...radead.org>,
        James Hogan <jhogan@...nel.org>,
        <linux-kernel@...r.kernel.org>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Boqun Feng <boqun.feng@...il.com>,
        "Paul E . McKenney" <paulmck@...ux.vnet.ibm.com>,
        Ralf Baechle <ralf@...ux-mips.org>,
        Paul Burton <paul.burton@...s.com>
Subject: [PATCH 2/4] MIPS: Add syscall detection for restartable sequences

Syscalls are not allowed inside restartable sequences, so add a call to
rseq_syscall() at the very beginning of the system call exit path when
CONFIG_DEBUG_RSEQ=y. This will help us to detect whether there is a
syscall issued erroneously inside a restartable sequence.

Signed-off-by: Paul Burton <paul.burton@...s.com>
Cc: James Hogan <jhogan@...nel.org>
Cc: Ralf Baechle <ralf@...ux-mips.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
Cc: Boqun Feng <boqun.feng@...il.com>
Cc: linux-mips@...ux-mips.org
Cc: linux-kernel@...r.kernel.org
---

 arch/mips/kernel/entry.S | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/arch/mips/kernel/entry.S b/arch/mips/kernel/entry.S
index 38a302919e6b..d7de8adcfcc8 100644
--- a/arch/mips/kernel/entry.S
+++ b/arch/mips/kernel/entry.S
@@ -79,6 +79,10 @@ FEXPORT(ret_from_fork)
 	jal	schedule_tail		# a0 = struct task_struct *prev
 
 FEXPORT(syscall_exit)
+#ifdef CONFIG_DEBUG_RSEQ
+	move	a0, sp
+	jal	rseq_syscall
+#endif
 	local_irq_disable		# make sure need_resched and
 					# signals dont change between
 					# sampling and return
@@ -141,6 +145,10 @@ work_notifysig:				# deal with pending signals and
 	j	resume_userspace_check
 
 FEXPORT(syscall_exit_partial)
+#ifdef CONFIG_DEBUG_RSEQ
+	move	a0, sp
+	jal	rseq_syscall
+#endif
 	local_irq_disable		# make sure need_resched doesn't
 					# change between and return
 	LONG_L	a2, TI_FLAGS($28)	# current->work
-- 
2.17.1