v4.19.13 snapshot.
diff --git a/arch/openrisc/kernel/unwinder.c b/arch/openrisc/kernel/unwinder.c
new file mode 100644
index 0000000..8ae15c2
--- /dev/null
+++ b/arch/openrisc/kernel/unwinder.c
@@ -0,0 +1,105 @@
+/*
+ * OpenRISC unwinder.c
+ *
+ * Reusable arch specific api for unwinding stacks.
+ *
+ * Copyright (C) 2017 Stafford Horne <shorne@gmail.com>
+ *
+ * This file is licensed under the terms of the GNU General Public License
+ * version 2. This program is licensed "as is" without any warranty of any
+ * kind, whether express or implied.
+ */
+
+#include <linux/sched/task_stack.h>
+#include <linux/kernel.h>
+
+#include <asm/unwinder.h>
+
+#ifdef CONFIG_FRAME_POINTER
+struct or1k_frameinfo {
+ unsigned long *fp;
+ unsigned long ra;
+ unsigned long top;
+};
+
+/*
+ * Verify a frameinfo structure. The return address should be a valid text
+ * address. The frame pointer may be null if its the last frame, otherwise
+ * the frame pointer should point to a location in the stack after the the
+ * top of the next frame up.
+ */
+static inline int or1k_frameinfo_valid(struct or1k_frameinfo *frameinfo)
+{
+ return (frameinfo->fp == NULL ||
+ (!kstack_end(frameinfo->fp) &&
+ frameinfo->fp > &frameinfo->top)) &&
+ __kernel_text_address(frameinfo->ra);
+}
+
+/*
+ * Create a stack trace doing scanning which is frame pointer aware. We can
+ * get reliable stack traces by matching the previously found frame
+ * pointer with the top of the stack address every time we find a valid
+ * or1k_frameinfo.
+ *
+ * Ideally the stack parameter will be passed as FP, but it can not be
+ * guaranteed. Therefore we scan each address looking for the first sign
+ * of a return address.
+ *
+ * The OpenRISC stack frame looks something like the following. The
+ * location SP is held in r1 and location FP is held in r2 when frame pointers
+ * enabled.
+ *
+ * SP -> (top of stack)
+ * - (callee saved registers)
+ * - (local variables)
+ * FP-8 -> previous FP \
+ * FP-4 -> return address |- or1k_frameinfo
+ * FP -> (previous top of stack) /
+ */
+void unwind_stack(void *data, unsigned long *stack,
+ void (*trace)(void *data, unsigned long addr, int reliable))
+{
+ unsigned long *next_fp = NULL;
+ struct or1k_frameinfo *frameinfo = NULL;
+ int reliable = 0;
+
+ while (!kstack_end(stack)) {
+ frameinfo = container_of(stack,
+ struct or1k_frameinfo,
+ top);
+
+ if (__kernel_text_address(frameinfo->ra)) {
+ if (or1k_frameinfo_valid(frameinfo) &&
+ (next_fp == NULL ||
+ next_fp == &frameinfo->top)) {
+ reliable = 1;
+ next_fp = frameinfo->fp;
+ } else
+ reliable = 0;
+
+ trace(data, frameinfo->ra, reliable);
+ }
+ stack++;
+ }
+}
+
+#else /* CONFIG_FRAME_POINTER */
+
+/*
+ * Create a stack trace by doing a simple scan treating all text addresses
+ * as return addresses.
+ */
+void unwind_stack(void *data, unsigned long *stack,
+ void (*trace)(void *data, unsigned long addr, int reliable))
+{
+ unsigned long addr;
+
+ while (!kstack_end(stack)) {
+ addr = *stack++;
+ if (__kernel_text_address(addr))
+ trace(data, addr, 0);
+ }
+}
+#endif /* CONFIG_FRAME_POINTER */
+