v4.19.13 snapshot.
diff --git a/include/linux/stacktrace.h b/include/linux/stacktrace.h
new file mode 100644
index 0000000..ba29a06
--- /dev/null
+++ b/include/linux/stacktrace.h
@@ -0,0 +1,44 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __LINUX_STACKTRACE_H
+#define __LINUX_STACKTRACE_H
+
+#include <linux/types.h>
+
+struct task_struct;
+struct pt_regs;
+
+#ifdef CONFIG_STACKTRACE
+struct stack_trace {
+ unsigned int nr_entries, max_entries;
+ unsigned long *entries;
+ int skip; /* input argument: How many entries to skip */
+};
+
+extern void save_stack_trace(struct stack_trace *trace);
+extern void save_stack_trace_regs(struct pt_regs *regs,
+ struct stack_trace *trace);
+extern void save_stack_trace_tsk(struct task_struct *tsk,
+ struct stack_trace *trace);
+extern int save_stack_trace_tsk_reliable(struct task_struct *tsk,
+ struct stack_trace *trace);
+
+extern void print_stack_trace(struct stack_trace *trace, int spaces);
+extern int snprint_stack_trace(char *buf, size_t size,
+ struct stack_trace *trace, int spaces);
+
+#ifdef CONFIG_USER_STACKTRACE_SUPPORT
+extern void save_stack_trace_user(struct stack_trace *trace);
+#else
+# define save_stack_trace_user(trace) do { } while (0)
+#endif
+
+#else /* !CONFIG_STACKTRACE */
+# define save_stack_trace(trace) do { } while (0)
+# define save_stack_trace_tsk(tsk, trace) do { } while (0)
+# define save_stack_trace_user(trace) do { } while (0)
+# define print_stack_trace(trace, spaces) do { } while (0)
+# define snprint_stack_trace(buf, size, trace, spaces) do { } while (0)
+# define save_stack_trace_tsk_reliable(tsk, trace) ({ -ENOSYS; })
+#endif /* CONFIG_STACKTRACE */
+
+#endif /* __LINUX_STACKTRACE_H */