arm: switch to generic sigaltstack

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

arch/arm/Kconfig

@@ -56,6 +56,7 @@ config ARM
 	select HAVE_MOD_ARCH_SPECIFIC if ARM_UNWIND
 	select MODULES_USE_ELF_REL
 	select CLONE_BACKWARDS
+	select GENERIC_SIGALTSTACK
 	help
 	  The ARM series is a line of low-power-consumption RISC chip designs
 	  licensed by ARM Ltd and targeted at embedded applications and

arch/arm/kernel/calls.S

@@ -195,7 +195,7 @@
 		CALL(sys_getcwd)
 		CALL(sys_capget)
 /* 185 */	CALL(sys_capset)
-		CALL(sys_sigaltstack_wrapper)
+		CALL(sys_sigaltstack)
 		CALL(sys_sendfile)
 		CALL(sys_ni_syscall)		/* getpmsg */
 		CALL(sys_ni_syscall)		/* putpmsg */

arch/arm/kernel/entry-common.S

@@ -514,11 +514,6 @@ sys_rt_sigreturn_wrapper:
 		b	sys_rt_sigreturn
 ENDPROC(sys_rt_sigreturn_wrapper)
 
-sys_sigaltstack_wrapper:
-		ldr	r2, [sp, #S_OFF + S_SP]
-		b	do_sigaltstack
-ENDPROC(sys_sigaltstack_wrapper)
-
 sys_statfs64_wrapper:
 		teq	r1, #88
 		moveq	r1, #84

arch/arm/kernel/signal.c

@@ -300,7 +300,7 @@ asmlinkage int sys_rt_sigreturn(struct pt_regs *regs)
 	if (restore_sigframe(regs, &frame->sig))
 		goto badframe;
 
-	if (do_sigaltstack(&frame->sig.uc.uc_stack, NULL, regs->ARM_sp) == -EFAULT)
+	if (restore_altstack(&frame->sig.uc.uc_stack))
 		goto badframe;
 
 	return regs->ARM_r0;
@@ -486,7 +486,6 @@ setup_rt_frame(int usig, struct k_sigaction *ka, siginfo_t *info,
 	       sigset_t *set, struct pt_regs *regs)
 {
 	struct rt_sigframe __user *frame = get_sigframe(ka, regs, sizeof(*frame));
-	stack_t stack;
 	int err = 0;
 
 	if (!frame)
@@ -497,12 +496,7 @@ setup_rt_frame(int usig, struct k_sigaction *ka, siginfo_t *info,
 	__put_user_error(0, &frame->sig.uc.uc_flags, err);
 	__put_user_error(NULL, &frame->sig.uc.uc_link, err);
 
-	memset(&stack, 0, sizeof(stack));
-	stack.ss_sp = (void __user *)current->sas_ss_sp;
-	stack.ss_flags = sas_ss_flags(regs->ARM_sp);
-	stack.ss_size = current->sas_ss_size;
-	err |= __copy_to_user(&frame->sig.uc.uc_stack, &stack, sizeof(stack));
-
+	err |= __save_altstack(&frame->sig.uc.uc_stack, regs->ARM_sp);
 	err |= setup_sigframe(&frame->sig, regs, set);
 	if (err == 0)
 		err = setup_return(regs, ka, frame->sig.retcode, frame, usig);