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>

2 files changed, 51 insertions, 1 deletions

diff --git a/arch/arc/include/asm/stacktrace.h b/arch/arc/include/asm/stacktrace.h
new file mode 100644
index 000000000000..b29b6064ea14
--- /dev/null
+++ b/arch/arc/include/asm/stacktrace.h
@@ -0,0 +1,37 @@
+/*
+ * Copyright (C) 2014-15 Synopsys, Inc. (www.synopsys.com)
+ * Copyright (C) 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#ifndef __ASM_STACKTRACE_H
+#define __ASM_STACKTRACE_H
+
+#include <linux/sched.h>
+
+/**
+ * arc_unwind_core - Unwind the kernel mode stack for an execution context
+ * @tsk:                NULL for current task, specific task otherwise
+ * @regs:               pt_regs used to seed the unwinder {SP, FP, BLINK, PC}
+ *                      If NULL, use pt_regs of @tsk (if !NULL) otherwise
+ *                      use the current values of {SP, FP, BLINK, PC}
+ * @consumer_fn:        Callback invoked for each frame unwound
+ *                      Returns 0 to continue unwinding, -1 to stop
+ * @arg:                Arg to callback
+ *
+ * Returns the address of first function in stack
+ *
+ * Semantics:
+ *  - synchronous unwinding (e.g. dump_stack): @tsk  NULL, @regs  NULL
+ *  - Asynchronous unwinding of sleeping task: @tsk !NULL, @regs  NULL
+ *  - Asynchronous unwinding of intr/excp etc: @tsk !NULL, @regs !NULL
+ */
+notrace noinline unsigned int arc_unwind_core(
+        struct task_struct *tsk, struct pt_regs *regs,
+        int (*consumer_fn) (unsigned int, void *),
+        void *arg);
+
+#endif /* __ASM_STACKTRACE_H */
diff --git a/arch/arc/kernel/stacktrace.c b/arch/arc/kernel/stacktrace.c
index 9ce47cfe2303..6492507a3d74 100644
--- a/arch/arc/kernel/stacktrace.c
+++ b/arch/arc/kernel/stacktrace.c
@@ -43,6 +43,10 @@ static void seed_unwind_frame_info(struct task_struct *tsk,
                                    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 @@ static void seed_unwind_frame_info(struct task_struct *tsk,
                 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 @@ static void seed_unwind_frame_info(struct task_struct *tsk,
                 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 @@ static void seed_unwind_frame_info(struct task_struct *tsk,
 
 #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)
 {