[PATCH v6 06/17] arm64: stacktrace: Add description of stacktrace/common.h

[Kalesh Singh]

Add brief description on how to use stacktrace/common.h to implement
a stack unwinder.

Signed-off-by: Kalesh Singh <kaleshsingh at google.com>
Reviewed-by: Fuad Tabba <tabba at google.com>
---

Changes in v6:
  - Add Fuad’s Reviewed-by tag

Changes in v5:
  - Add short description of each required function, per Fuad and Marc

 arch/arm64/include/asm/stacktrace/common.h | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/arch/arm64/include/asm/stacktrace/common.h b/arch/arm64/include/asm/stacktrace/common.h
index 4b632141d91c..45474b383630 100644
--- a/arch/arm64/include/asm/stacktrace/common.h
+++ b/arch/arm64/include/asm/stacktrace/common.h
@@ -2,6 +2,21 @@
 /*
  * Common arm64 stack unwinder code.
  *
+ * To implement a new arm64 stack unwinder:
+ *     1) Include this header
+ *
+ *     2) Provide implementations for the following functions:
+ *          on_overflow_stack():   Returns true if SP is on the overflow
+ *                                 stack.
+ *          on_accessible_stack(): Returns true is SP is on any accessible
+ *                                 stack.
+ *          unwind_next():         Performs validation checks on the frame
+ *                                 pointer, and transitions unwind_state
+ *                                 to the next frame.
+ *
+ *         See: arch/arm64/include/asm/stacktrace.h for reference
+ *              implementations.
+ *
  * Copyright (C) 2012 ARM Ltd.
  */
 #ifndef __ASM_STACKTRACE_COMMON_H
-- 
2.37.1.359.gd136c6c3e2-goog