v4.19.13 snapshot.
diff --git a/arch/riscv/kernel/stacktrace.c b/arch/riscv/kernel/stacktrace.c
new file mode 100644
index 0000000..a4b1d94
--- /dev/null
+++ b/arch/riscv/kernel/stacktrace.c
@@ -0,0 +1,183 @@
+/*
+ * Copyright (C) 2008 ARM Limited
+ * Copyright (C) 2014 Regents of the University of California
+ *
+ * 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.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ */
+
+#include <linux/export.h>
+#include <linux/kallsyms.h>
+#include <linux/sched.h>
+#include <linux/sched/debug.h>
+#include <linux/sched/task_stack.h>
+#include <linux/stacktrace.h>
+#include <linux/ftrace.h>
+
+#ifdef CONFIG_FRAME_POINTER
+
+struct stackframe {
+ unsigned long fp;
+ unsigned long ra;
+};
+
+static void notrace walk_stackframe(struct task_struct *task,
+ struct pt_regs *regs, bool (*fn)(unsigned long, void *), void *arg)
+{
+ unsigned long fp, sp, pc;
+
+ if (regs) {
+ fp = GET_FP(regs);
+ sp = GET_USP(regs);
+ pc = GET_IP(regs);
+ } else if (task == NULL || task == current) {
+ const register unsigned long current_sp __asm__ ("sp");
+ fp = (unsigned long)__builtin_frame_address(0);
+ sp = current_sp;
+ pc = (unsigned long)walk_stackframe;
+ } else {
+ /* task blocked in __switch_to */
+ fp = task->thread.s[0];
+ sp = task->thread.sp;
+ pc = task->thread.ra;
+ }
+
+ for (;;) {
+ unsigned long low, high;
+ struct stackframe *frame;
+
+ if (unlikely(!__kernel_text_address(pc) || fn(pc, arg)))
+ break;
+
+ /* Validate frame pointer */
+ low = sp + sizeof(struct stackframe);
+ high = ALIGN(sp, THREAD_SIZE);
+ if (unlikely(fp < low || fp > high || fp & 0x7))
+ break;
+ /* Unwind stack frame */
+ frame = (struct stackframe *)fp - 1;
+ sp = fp;
+ fp = frame->fp;
+#ifdef HAVE_FUNCTION_GRAPH_RET_ADDR_PTR
+ pc = ftrace_graph_ret_addr(current, NULL, frame->ra,
+ (unsigned long *)(fp - 8));
+#else
+ pc = frame->ra - 0x4;
+#endif
+ }
+}
+
+#else /* !CONFIG_FRAME_POINTER */
+
+static void notrace walk_stackframe(struct task_struct *task,
+ struct pt_regs *regs, bool (*fn)(unsigned long, void *), void *arg)
+{
+ unsigned long sp, pc;
+ unsigned long *ksp;
+
+ if (regs) {
+ sp = GET_USP(regs);
+ pc = GET_IP(regs);
+ } else if (task == NULL || task == current) {
+ const register unsigned long current_sp __asm__ ("sp");
+ sp = current_sp;
+ pc = (unsigned long)walk_stackframe;
+ } else {
+ /* task blocked in __switch_to */
+ sp = task->thread.sp;
+ pc = task->thread.ra;
+ }
+
+ if (unlikely(sp & 0x7))
+ return;
+
+ ksp = (unsigned long *)sp;
+ while (!kstack_end(ksp)) {
+ if (__kernel_text_address(pc) && unlikely(fn(pc, arg)))
+ break;
+ pc = (*ksp++) - 0x4;
+ }
+}
+
+#endif /* CONFIG_FRAME_POINTER */
+
+
+static bool print_trace_address(unsigned long pc, void *arg)
+{
+ print_ip_sym(pc);
+ return false;
+}
+
+void show_stack(struct task_struct *task, unsigned long *sp)
+{
+ pr_cont("Call Trace:\n");
+ walk_stackframe(task, NULL, print_trace_address, NULL);
+}
+
+
+static bool save_wchan(unsigned long pc, void *arg)
+{
+ if (!in_sched_functions(pc)) {
+ unsigned long *p = arg;
+ *p = pc;
+ return true;
+ }
+ return false;
+}
+
+unsigned long get_wchan(struct task_struct *task)
+{
+ unsigned long pc = 0;
+
+ if (likely(task && task != current && task->state != TASK_RUNNING))
+ walk_stackframe(task, NULL, save_wchan, &pc);
+ return pc;
+}
+
+
+#ifdef CONFIG_STACKTRACE
+
+static bool __save_trace(unsigned long pc, void *arg, bool nosched)
+{
+ struct stack_trace *trace = arg;
+
+ if (unlikely(nosched && in_sched_functions(pc)))
+ return false;
+ if (unlikely(trace->skip > 0)) {
+ trace->skip--;
+ return false;
+ }
+
+ trace->entries[trace->nr_entries++] = pc;
+ return (trace->nr_entries >= trace->max_entries);
+}
+
+static bool save_trace(unsigned long pc, void *arg)
+{
+ return __save_trace(pc, arg, false);
+}
+
+/*
+ * Save stack-backtrace addresses into a stack_trace buffer.
+ */
+void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
+{
+ walk_stackframe(tsk, NULL, save_trace, trace);
+ if (trace->nr_entries < trace->max_entries)
+ trace->entries[trace->nr_entries++] = ULONG_MAX;
+}
+EXPORT_SYMBOL_GPL(save_stack_trace_tsk);
+
+void save_stack_trace(struct stack_trace *trace)
+{
+ save_stack_trace_tsk(NULL, trace);
+}
+EXPORT_SYMBOL_GPL(save_stack_trace);
+
+#endif /* CONFIG_STACKTRACE */