Honor QEMU_ESIGRETURN and QEMU_ERESTARTSYS.

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 linux-user/nios2/cpu_loop.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/linux-user/nios2/cpu_loop.c b/linux-user/nios2/cpu_loop.c
index 63afba5862..2963fc62b4 100644
--- a/linux-user/nios2/cpu_loop.c
+++ b/linux-user/nios2/cpu_loop.c
@@ -55,6 +55,14 @@ void cpu_loop(CPUNios2State *env)
                                  env->regs[7], env->regs[8], env->regs[9],
                                  0, 0);
 
+                if (ret == -QEMU_ESIGRETURN) {
+                    /* rt_sigreturn has set all state. */
+                    break;
+                }
+                if (ret == -QEMU_ERESTARTSYS) {
+                    env->regs[R_PC] -= 4;
+                    break;
+                }
                 /*
                  * See the code after translate_rc_and_ret: all negative
                  * values are errors (aided by userspace restricted to 2G),
-- 
2.34.1