mips: switch to generic sigaltstack

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/arch/mips/kernel/signal.c b/arch/mips/kernel/signal.c
index 4d790d1..eab3086 100644
--- a/arch/mips/kernel/signal.c
+++ b/arch/mips/kernel/signal.c
@@ -313,15 +313,6 @@
 }
 #endif
 
-asmlinkage int sys_sigaltstack(nabi_no_regargs struct pt_regs regs)
-{
-	const stack_t __user *uss = (const stack_t __user *) regs.regs[4];
-	stack_t __user *uoss = (stack_t __user *) regs.regs[5];
-	unsigned long usp = regs.regs[29];
-
-	return do_sigaltstack(uss, uoss, usp);
-}
-
 #ifdef CONFIG_TRAD_SIGNALS
 asmlinkage void sys_sigreturn(nabi_no_regargs struct pt_regs regs)
 {
@@ -378,9 +369,8 @@
 	else if (sig)
 		force_sig(sig, current);
 
-	/* It is more difficult to avoid calling this function than to
-	   call it and ignore errors.  */
-	do_sigaltstack(&frame->rs_uc.uc_stack, NULL, regs.regs[29]);
+	if (restore_altstack(&frame->rs_uc.uc_stack))
+		goto badframe;
 
 	/*
 	 * Don't let your children do this ...
@@ -457,12 +447,7 @@
 	/* Create the ucontext.  */
 	err |= __put_user(0, &frame->rs_uc.uc_flags);
 	err |= __put_user(NULL, &frame->rs_uc.uc_link);
-	err |= __put_user((void __user *)current->sas_ss_sp,
-	                  &frame->rs_uc.uc_stack.ss_sp);
-	err |= __put_user(sas_ss_flags(regs->regs[29]),
-	                  &frame->rs_uc.uc_stack.ss_flags);
-	err |= __put_user(current->sas_ss_size,
-	                  &frame->rs_uc.uc_stack.ss_size);
+	err |= __save_altstack(&frame->rs_uc.uc_stack, regs->regs[29]);
 	err |= setup_sigcontext(regs, &frame->rs_uc.uc_mcontext);
 	err |= __copy_to_user(&frame->rs_uc.uc_sigmask, set, sizeof(*set));