s390: add current_stack_pointer() helper function

Implement current_stack_pointer() helper function and use it
everywhere, instead of having several different inline assembly
variants.
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Tested-by: Peter Oberparleiter <oberpar@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/include/asm/processor.h

@@ -203,6 +203,14 @@ unsigned long get_wchan(struct task_struct *p);
 /* Has task runtime instrumentation enabled ? */
 #define is_ri_task(tsk) (!!(tsk)->thread.ri_cb)
 
+static inline unsigned long current_stack_pointer(void)
+{
+	unsigned long sp;
+
+	asm volatile("la %0,0(15)" : "=a" (sp));
+	return sp;
+}
+
 static inline unsigned short stap(void)
 {
 	unsigned short cpu_address;

arch/s390/kernel/dumpstack.c

@@ -67,12 +67,11 @@ static void show_trace(struct task_struct *task, unsigned long *stack)
 {
 	const unsigned long frame_size =
 		STACK_FRAME_OVERHEAD + sizeof(struct pt_regs);
-	register unsigned long __r15 asm ("15");
 	unsigned long sp;
 
 	sp = (unsigned long) stack;
 	if (!sp)
-		sp = task ? task->thread.ksp : __r15;
+		sp = task ? task->thread.ksp : current_stack_pointer();
 	printk("Call Trace:\n");
 #ifdef CONFIG_CHECK_STACK
 	sp = __show_trace(sp,
@@ -95,15 +94,16 @@ static void show_trace(struct task_struct *task, unsigned long *stack)
 
 void show_stack(struct task_struct *task, unsigned long *sp)
 {
-	register unsigned long *__r15 asm ("15");
 	unsigned long *stack;
 	int i;
 
-	if (!sp)
-		stack = task ? (unsigned long *) task->thread.ksp : __r15;
-	else
 	stack = sp;
-
+	if (!stack) {
+		if (!task)
+			stack = (unsigned long *)current_stack_pointer();
+		else
+			stack = (unsigned long *)task->thread.ksp;
+	}
 	for (i = 0; i < 20; i++) {
 		if (((addr_t) stack & (THREAD_SIZE-1)) == 0)
 			break;

arch/s390/kernel/irq.c

@@ -164,8 +164,7 @@ void do_softirq_own_stack(void)
 {
 	unsigned long old, new;
 
-	/* Get current stack pointer. */
-	asm volatile("la %0,0(15)" : "=a" (old));
+	old = current_stack_pointer();
 	/* Check against async. stack address range. */
 	new = S390_lowcore.async_stack;
 	if (((new - old) >> (PAGE_SHIFT + THREAD_ORDER)) != 0) {

arch/s390/kernel/stacktrace.c

@@ -77,10 +77,9 @@ static void __save_stack_trace(struct stack_trace *trace, unsigned long sp)
 
 void save_stack_trace(struct stack_trace *trace)
 {
-	register unsigned long r15 asm ("15");
 	unsigned long sp;
 
-	sp = r15;
+	sp = current_stack_pointer();
 	__save_stack_trace(trace, sp);
 	if (trace->nr_entries < trace->max_entries)
 		trace->entries[trace->nr_entries++] = ULONG_MAX;
@@ -92,10 +91,8 @@ void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
 	unsigned long sp, low, high;
 
 	sp = tsk->thread.ksp;
-	if (tsk == current) {
-		/* Get current stack pointer. */
-		asm volatile("la %0,0(15)" : "=a" (sp));
-	}
+	if (tsk == current)
+		sp = current_stack_pointer();
 	low = (unsigned long) task_stack_page(tsk);
 	high = (unsigned long) task_pt_regs(tsk);
 	save_context_stack(trace, sp, low, high, 1);