arm: Add restartable sequences support

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 frame when a signal is delivered on top
of a restartable sequence critical section.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Joel Fernandes <joelaf@google.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Dave Watson <davejwatson@fb.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: "H . Peter Anvin" <hpa@zytor.com>
Cc: Chris Lameter <cl@linux.com>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Andrew Hunter <ahh@google.com>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: "Paul E . McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Paul Turner <pjt@google.com>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Ben Maurer <bmaurer@fb.com>
Cc: linux-api@vger.kernel.org
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: https://lkml.kernel.org/r/20180602124408.8430-4-mathieu.desnoyers@efficios.com

2 files changed, 8 insertions, 0 deletions

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index c43f5bb55ac8..4fb45365c0ea 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -90,6 +90,7 @@ config ARM
         select HAVE_PERF_USER_STACK_DUMP
         select HAVE_RCU_TABLE_FREE if (SMP && ARM_LPAE)
         select HAVE_REGS_AND_STACK_ACCESS_API
+        select HAVE_RSEQ
         select HAVE_SYSCALL_TRACEPOINTS
         select HAVE_UID16
         select HAVE_VIRT_CPU_ACCOUNTING_GEN
diff --git a/arch/arm/kernel/signal.c b/arch/arm/kernel/signal.c
index bd8810d4acb3..5879ab3f53c1 100644
--- a/arch/arm/kernel/signal.c
+++ b/arch/arm/kernel/signal.c
@@ -541,6 +541,12 @@ static void handle_signal(struct ksignal *ksig, struct pt_regs *regs)
         int ret;
 
         /*
+         * Increment event counter and perform fixup for the pre-signal
+         * frame.
+         */
+        rseq_signal_deliver(regs);
+
+        /*
          * Set up the stack frame
          */
         if (ksig->ka.sa.sa_flags & SA_SIGINFO)
@@ -660,6 +666,7 @@ do_work_pending(struct pt_regs *regs, unsigned int thread_flags, int syscall)
                         } else {
                                 clear_thread_flag(TIF_NOTIFY_RESUME);
                                 tracehook_notify_resume(regs);
+                                rseq_handle_notify_resume(regs);
                         }
                 }
                 local_irq_disable();