[SPARC]: Add support for *at(), ppoll, and pselect syscalls.

This also includes by necessity _TIF_RESTORE_SIGMASK support,
which actually resulted in a lot of cleanups.

The sparc signal handling code is quite a mess and I should
clean it up some day.

Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/arch/sparc64/solaris/entry64.S b/arch/sparc64/solaris/entry64.S
index 4b6ae58..eb314ed 100644
--- a/arch/sparc64/solaris/entry64.S
+++ b/arch/sparc64/solaris/entry64.S
@@ -180,6 +180,8 @@
 	 nop
 	call		sys_sigsuspend
 	 stx		%o0, [%sp + PTREGS_OFF + PT_V9_I0]
+	b,pt		%xcc, ret_from_solaris
+	 nop
 
 	.globl		solaris_getpid
 solaris_getpid: