xtensa: switch to generic sigaltstack

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

arch/xtensa/Kconfig

···
 	select ARCH_WANT_OPTIONAL_GPIOLIB
 	select CLONE_BACKWARDS
 	select IRQ_DOMAIN
+	select GENERIC_SIGALTSTACK
 	help
 	  Xtensa processors are 32-bit RISC machines designed by Tensilica
 	  primarily for embedded systems.  These processors are both

arch/xtensa/include/asm/syscall.h

···
 asmlinkage long xtensa_ptrace(long, long, long, long);
 asmlinkage long xtensa_sigreturn(struct pt_regs*);
 asmlinkage long xtensa_rt_sigreturn(struct pt_regs*);
-asmlinkage long xtensa_sigaltstack(struct pt_regs *regs);
 asmlinkage long xtensa_shmat(int, char __user *, int);
 asmlinkage long xtensa_fadvise64_64(int, int,
 				    unsigned long long, unsigned long long);

arch/xtensa/include/uapi/asm/unistd.h

···
 #define __NR_restart_syscall 			223
 __SYSCALL(223, sys_restart_syscall, 0)
 #define __NR_sigaltstack 			224
-__SYSCALL(224, xtensa_sigaltstack, 2)
+__SYSCALL(224, sys_sigaltstack, 2)
 #define __NR_rt_sigreturn 			225
 __SYSCALL(225, xtensa_rt_sigreturn, 1)
 #define __NR_rt_sigaction 			226

arch/xtensa/kernel/signal.c

···
 
 	ret = regs->areg[2];
 
-	if (do_sigaltstack(&frame->uc.uc_stack, NULL, regs->areg[1]) == -EFAULT)
+	if (restore_altstack(&frame->uc.uc_stack))
 		goto badframe;
 
 	return ret;
···
 
 	err |= __put_user(0, &frame->uc.uc_flags);
 	err |= __put_user(0, &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->areg[1]),
-			  &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->areg[1]);
 	err |= setup_sigcontext(frame, regs);
 	err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
 
···
 	force_sigsegv(sig, current);
 	return -EFAULT;
 }
-
-asmlinkage long xtensa_sigaltstack(const stack_t __user *uss,
-				   stack_t __user *uoss,
-				   long a2, long a3, long a4, long a5,
-				   struct pt_regs *regs)
-{
-	return do_sigaltstack(uss, uoss, regs->areg[1]);
-}
-
-
 
 /*
  * Note that 'init' is a special process: it doesn't get signals it doesn't