hexagon: switch to generic sigaltstack

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

arch/hexagon/Kconfig

@@ -31,6 +31,7 @@ config HEXAGON
 	select GENERIC_CLOCKEVENTS
 	select GENERIC_CLOCKEVENTS_BROADCAST
 	select MODULES_USE_ELF_RELA
+	select GENERIC_SIGALTSTACK
 	---help---
 	  Qualcomm Hexagon is a processor architecture designed for high
 	  performance and low power across a wide variety of applications.

arch/hexagon/kernel/signal.c

@@ -247,12 +247,6 @@ void do_notify_resume(struct pt_regs *regs, unsigned long thread_info_flags)
 /*
  * Architecture-specific wrappers for signal-related system calls
  */
-asmlinkage int sys_sigaltstack(const stack_t __user *uss, stack_t __user *uoss)
-{
-	struct pt_regs *regs = current_pt_regs();
-
-	return do_sigaltstack(uss, uoss, regs->r29);
-}
 
 asmlinkage int sys_rt_sigreturn(void)
 {
@@ -288,14 +282,7 @@ asmlinkage int sys_rt_sigreturn(void)
 	 */
 	regs->syscall_nr = __NR_rt_sigreturn;
 
-	/*
-	 * If we were meticulous, we'd only call this if we knew that
-	 * we were actually going to use an alternate stack, and we'd
-	 * consider any error to be fatal.  What we do here, in common
-	 * with many other architectures, is call it blindly and only
-	 * consider the -EFAULT return case to be proof of a problem.
-	 */
-	if (do_sigaltstack(&frame->uc.uc_stack, NULL, pt_psp(regs)) == -EFAULT)
+	if (restore_altstack(&frame->uc.uc_stack))
 		goto badframe;
 
 	return 0;