[RFC PATCH for 4.18 08/16] powerpc: Add support for restartable sequences

[Mathieu Desnoyers]

From: Boqun Feng <boqun.feng at gmail.com>

Call the rseq_handle_notify_resume() function on return to userspace if
TIF_NOTIFY_RESUME thread flag is set.

Perform fixup on the pre-signal when a signal is delivered on top of a
restartable sequence critical section.

Signed-off-by: Boqun Feng <boqun.feng at gmail.com>
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: Peter Zijlstra <peterz at infradead.org>
CC: "Paul E. McKenney" <paulmck at linux.vnet.ibm.com>
CC: linuxppc-dev at lists.ozlabs.org
---
 arch/powerpc/Kconfig         | 1 +
 arch/powerpc/kernel/signal.c | 3 +++
 2 files changed, 4 insertions(+)

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index c32a181a7cbb..ed21a777e8c6 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -223,6 +223,7 @@ config PPC
 	select HAVE_SYSCALL_TRACEPOINTS
 	select HAVE_VIRT_CPU_ACCOUNTING
 	select HAVE_IRQ_TIME_ACCOUNTING
+	select HAVE_RSEQ
 	select IRQ_DOMAIN
 	select IRQ_FORCED_THREADING
 	select MODULES_USE_ELF_RELA
diff --git a/arch/powerpc/kernel/signal.c b/arch/powerpc/kernel/signal.c
index 61db86ecd318..d3bb3aaaf5ac 100644
--- a/arch/powerpc/kernel/signal.c
+++ b/arch/powerpc/kernel/signal.c
@@ -133,6 +133,8 @@ static void do_signal(struct task_struct *tsk)
 	/* Re-enable the breakpoints for the signal stack */
 	thread_change_pc(tsk, tsk->thread.regs);
 
+	rseq_signal_deliver(tsk->thread.regs);
+
 	if (is32) {
         	if (ksig.ka.sa.sa_flags & SA_SIGINFO)
 			ret = handle_rt_signal32(&ksig, oldset, tsk);
@@ -164,6 +166,7 @@ void do_notify_resume(struct pt_regs *regs, unsigned long thread_info_flags)
 	if (thread_info_flags & _TIF_NOTIFY_RESUME) {
 		clear_thread_flag(TIF_NOTIFY_RESUME);
 		tracehook_notify_resume(regs);
+		rseq_handle_notify_resume(regs);
 	}
 
 	user_enter();
-- 
2.11.0