[PATCH v13 01/14] unwind_user: Add user space unwinding API

@@ -25928,6 +25928,14 @@ F:	Documentation/driver-api/uio-howto.rst
 F:	drivers/uio/
 F:	include/linux/uio_driver.h
 
+USERSPACE STACK UNWINDING
+M:	Josh Poimboeuf <jpoimboe@kernel.org>
+M:	Steven Rostedt <rostedt@goodmis.org>
+S:	Maintained
+F:	include/linux/unwind*.h
+F:	kernel/unwind/
+
+
 UTIL-LINUX PACKAGE
 M:	Karel Zak <kzak@redhat.com>
 L:	util-linux@vger.kernel.org

@@ -435,6 +435,9 @@ config HAVE_HARDLOCKUP_DETECTOR_ARCH
 	  It uses the same command line parameters, and sysctl interface,
 	  as the generic hardlockup detectors.
 
+config UNWIND_USER
+	bool
+
 config HAVE_PERF_REGS
 	bool
 	help

@@ -0,0 +1,9 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _LINUX_UNWIND_USER_H
+#define _LINUX_UNWIND_USER_H
+
+#include <linux/unwind_user_types.h>
+
+int unwind_user(struct unwind_stacktrace *trace, unsigned int max_entries);
+
+#endif /* _LINUX_UNWIND_USER_H */

@@ -0,0 +1,31 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _LINUX_UNWIND_USER_TYPES_H
+#define _LINUX_UNWIND_USER_TYPES_H
+
+#include <linux/types.h>
+
+enum unwind_user_type {
+	UNWIND_USER_TYPE_NONE,
+};
+
+struct unwind_stacktrace {
+	unsigned int	nr;
+	unsigned long	*entries;
+};
+
+struct unwind_user_frame {
+	s32 cfa_off;
+	s32 ra_off;
+	s32 fp_off;
+	bool use_fp;
+};
+
+struct unwind_user_state {
+	unsigned long ip;
+	unsigned long sp;
+	unsigned long fp;
+	enum unwind_user_type type;
+	bool done;
+};
+
+#endif /* _LINUX_UNWIND_USER_TYPES_H */

@@ -55,6 +55,7 @@ obj-y += rcu/
 obj-y += livepatch/
 obj-y += dma/
 obj-y += entry/
+obj-y += unwind/
 obj-$(CONFIG_MODULES) += module/
 
 obj-$(CONFIG_KCMP) += kcmp.o

@@ -0,0 +1 @@
+ obj-$(CONFIG_UNWIND_USER) += user.o

@@ -0,0 +1,58 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+* Generic interfaces for unwinding user space
+*/
+#include <linux/kernel.h>
+#include <linux/sched.h>
+#include <linux/sched/task_stack.h>
+#include <linux/unwind_user.h>
+
+#define for_each_user_frame(state) \
+	for (unwind_user_start(state); !(state)->done; unwind_user_next(state))
+
+static int unwind_user_next(struct unwind_user_state *state)
+{
+	/* no implementation yet */
+	return -EINVAL;
+}
+
+static int unwind_user_start(struct unwind_user_state *state)
+{
+	struct pt_regs *regs = task_pt_regs(current);
+
+	memset(state, 0, sizeof(*state));
+
+	if ((current->flags & PF_KTHREAD) || !user_mode(regs)) {
+		state->done = true;
+		return -EINVAL;
+	}
+
+	state->type = UNWIND_USER_TYPE_NONE;
+
+	state->ip = instruction_pointer(regs);
+	state->sp = user_stack_pointer(regs);
+	state->fp = frame_pointer(regs);
+
+	return 0;
+}
+
+int unwind_user(struct unwind_stacktrace *trace, unsigned int max_entries)
+{
+	struct unwind_user_state state;
+
+	trace->nr = 0;
+
+	if (!max_entries)
+		return -EINVAL;
+
+	if (current->flags & PF_KTHREAD)
+		return 0;
+
+	for_each_user_frame(&state) {
+		trace->entries[trace->nr++] = state.ip;
+		if (trace->nr >= max_entries)
+			break;
+	}
+
+	return 0;
+}