linux-kernel - [PATCH 1/4] MIPS: Add support for restartable sequences

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Date:   Thu, 14 Jun 2018 16:52:07 -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 1/4] MIPS: Add support for restartable sequences

Implement support for restartable sequences on MIPS, which requires 3
simple things:

  - Call rseq_handle_notify_resume() on return to userspace if
    TIF_NOTIFY_RESUME is set.

  - Call rseq_signal_deliver() to fixup the pre-signal stack frame when
    a signal is delivered whilst executing a restartable sequence
    critical section.

  - Select CONFIG_HAVE_RSEQ.

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/Kconfig         | 1 +
 arch/mips/kernel/signal.c | 3 +++
 2 files changed, 4 insertions(+)

diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
index fe98e459a416..afe2b0c867ac 100644
--- a/arch/mips/Kconfig
+++ b/arch/mips/Kconfig
@@ -66,6 +66,7 @@ config MIPS
 	select HAVE_OPROFILE
 	select HAVE_PERF_EVENTS
 	select HAVE_REGS_AND_STACK_ACCESS_API
+	select HAVE_RSEQ
 	select HAVE_SYSCALL_TRACEPOINTS
 	select HAVE_VIRT_CPU_ACCOUNTING_GEN if 64BIT || !SMP
 	select IRQ_FORCED_THREADING
diff --git a/arch/mips/kernel/signal.c b/arch/mips/kernel/signal.c
index 9e224469c788..00f2535d2226 100644
--- a/arch/mips/kernel/signal.c
+++ b/arch/mips/kernel/signal.c
@@ -801,6 +801,8 @@ static void handle_signal(struct ksignal *ksig, struct pt_regs *regs)
 		regs->regs[0] = 0;		/* Don't deal with this again.	*/
 	}
 
+	rseq_signal_deliver(regs);
+
 	if (sig_uses_siginfo(&ksig->ka, abi))
 		ret = abi->setup_rt_frame(vdso + abi->vdso->off_rt_sigreturn,
 					  ksig, regs, oldset);
@@ -868,6 +870,7 @@ asmlinkage void do_notify_resume(struct pt_regs *regs, void *unused,
 	if (thread_info_flags & _TIF_NOTIFY_RESUME) {
 		clear_thread_flag(TIF_NOTIFY_RESUME);
 		tracehook_notify_resume(regs);
+		rseq_handle_notify_resume(regs);
 	}
 
 	user_enter();
-- 
2.17.1