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

[Paul Burton]

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.bur...@mips.com>
Cc: James Hogan <jho...@kernel.org>
Cc: Ralf Baechle <r...@linux-mips.org>
Cc: Mathieu Desnoyers <mathieu.desnoy...@efficios.com>
Cc: Peter Zijlstra <pet...@infradead.org>
Cc: Paul E. McKenney <paul...@linux.vnet.ibm.com>
Cc: Boqun Feng <boqun.f...@gmail.com>
Cc: linux-m...@linux-mips.org
Cc: linux-kernel@vger.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