openrisc: switch to generic sigaltstack

Signed-off-by: Al Viro <[e-mail]>

arch/openrisc/Kconfig

···
 	select GENERIC_STRNCPY_FROM_USER
 	select GENERIC_STRNLEN_USER
 	select MODULES_USE_ELF_RELA
+	select GENERIC_SIGALTSTACK
 
 config MMU
 	def_bool y

arch/openrisc/kernel/entry.S

···
 	l.j	_fork_save_extra_regs_and_call
 	 l.addi	r3,r1,0
 
-ENTRY(sys_sigaltstack)
-	l.j	_sys_sigaltstack
-	 l.addi	r5,r1,0
-
 ENTRY(sys_rt_sigreturn)
 	l.j	_sys_rt_sigreturn
 	 l.addi	r3,r1,0

arch/openrisc/kernel/signal.c

···
 
 #define DEBUG_SIG 0
 
-asmlinkage long
-_sys_sigaltstack(const stack_t *uss, stack_t *uoss, struct pt_regs *regs)
-{
-	return do_sigaltstack(uss, uoss, regs->sp);
-}
-
 struct rt_sigframe {
 	struct siginfo *pinfo;
 	void *puc;
···
 	if (restore_sigcontext(regs, &frame->uc.uc_mcontext))
 		goto badframe;
 
-	/* It is more difficult to avoid calling this function than to
-	   call it and ignore errors.  */
-	if (do_sigaltstack(&frame->uc.uc_stack, NULL, regs->sp) == -EFAULT)
+	if (restore_altstack(&frame->uc.uc_stack))
 		goto badframe;
 
 	return regs->gpr[11];
···
 	err |= __clear_user(&frame->uc, offsetof(struct ucontext, uc_mcontext));
 	err |= __put_user(0, &frame->uc.uc_flags);
 	err |= __put_user(NULL, &frame->uc.uc_link);
-	err |= __put_user((void *)current->sas_ss_sp,
-			  &frame->uc.uc_stack.ss_sp);
-	err |= __put_user(sas_ss_flags(regs->sp), &frame->uc.uc_stack.ss_flags);
-	err |= __put_user(current->sas_ss_size, &frame->uc.uc_stack.ss_size);
+	err |= __save_altstack(&frame->uc.uc_stack, regs->sp);
 	err |= setup_sigcontext(&frame->uc.uc_mcontext, regs, set->sig[0]);
 
 	err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));