ARC: Make arc_unwind_core accessible externally

The arc unwinder can also be used for perf callchains.

Signed-off-by: Mischa Jonker <mjonker@synopsys.com>
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
diff --git a/arch/arc/kernel/stacktrace.c b/arch/arc/kernel/stacktrace.c
index 9ce47cf..6492507 100644
--- a/arch/arc/kernel/stacktrace.c
+++ b/arch/arc/kernel/stacktrace.c
@@ -43,6 +43,10 @@
 				   struct pt_regs *regs,
 				   struct unwind_frame_info *frame_info)
 {
+	/*
+	 * synchronous unwinding (e.g. dump_stack)
+	 *  - uses current values of SP and friends
+	 */
 	if (tsk == NULL && regs == NULL) {
 		unsigned long fp, sp, blink, ret;
 		frame_info->task = current;
@@ -61,6 +65,11 @@
 		frame_info->regs.r63 = ret;
 		frame_info->call_frame = 0;
 	} else if (regs == NULL) {
+		/*
+		 * Asynchronous unwinding of sleeping task
+		 *  - Gets SP etc from task's pt_regs (saved bottom of kernel
+		 *    mode stack of task)
+		 */
 
 		frame_info->task = tsk;
 
@@ -83,6 +92,10 @@
 		frame_info->call_frame = 0;
 
 	} else {
+		/*
+		 * Asynchronous unwinding of intr/exception
+		 *  - Just uses the pt_regs passed
+		 */
 		frame_info->task = tsk;
 
 		frame_info->regs.r27 = regs->fp;
@@ -95,7 +108,7 @@
 
 #endif
 
-static noinline unsigned int
+notrace noinline unsigned int
 arc_unwind_core(struct task_struct *tsk, struct pt_regs *regs,
 		int (*consumer_fn) (unsigned int, void *), void *arg)
 {