Commit 71753c6e authored Jul 29, 2025 by Josh Poimboeuf Committed by Steven Rostedt (Google) Jul 29, 2025

unwind_user: Add user space unwinding API with frame pointer support

Introduce a generic API for unwinding user stacks.

In order to expand user space unwinding to be able to handle more complex
scenarios, such as deferred unwinding and reading user space information,
create a generic interface that all architectures can use that support the
various unwinding methods.

This is an alternative method for handling user space stack traces from
the simple stack_trace_save_user() API. This does not replace that
interface, but this interface will be used to expand the functionality of
user space stack walking.

None of the structures introduced will be exposed to user space tooling.

Support for frame pointer unwinding is added. For an architecture to
support frame pointer unwinding it needs to enable
CONFIG_HAVE_UNWIND_USER_FP and define ARCH_INIT_USER_FP_FRAME.

By encoding the frame offsets in struct unwind_user_frame, much of this
code can also be reused for future unwinder implementations like sframe.

Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Andrii Nakryiko <andrii@kernel.org>
Cc: Indu Bhagat <indu.bhagat@oracle.com>
Cc: "Jose E. Marchesi" <jemarch@gnu.org>
Cc: Beau Belgrave <beaub@linux.microsoft.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Florian Weimer <fweimer@redhat.com>
Cc: Sam James <sam@gentoo.org>
Link: https://lore.kernel.org/20250729182404.975790139@kernel.org


Reviewed-by: Jens Remus <jremus@linux.ibm.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Co-developed-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Link: https://lore.kernel.org/all/20250710164301.3094-2-mathieu.desnoyers@efficios.com/


Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Co-developed-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

parent d7b8f8e2

MAINTAINERS

+8 −0

Original line number	Diff line number	Diff line
		@@ -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

arch/Kconfig

+7 −0

Original line number	Diff line number	Diff line
		@@ -435,6 +435,13 @@ 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_UNWIND_USER_FP
		bool
		select UNWIND_USER

		config HAVE_PERF_REGS
		bool
		help

include/asm-generic/Kbuild

+1 −0

Original line number	Diff line number	Diff line
		@@ -59,6 +59,7 @@ mandatory-y += tlbflush.h
		mandatory-y += topology.h
		mandatory-y += trace_clock.h
		mandatory-y += uaccess.h
		mandatory-y += unwind_user.h
		mandatory-y += vermagic.h
		mandatory-y += vga.h
		mandatory-y += video.h

include/asm-generic/unwind_user.h

0 → 100644

+5 −0

Original line number	Diff line number	Diff line
		/* SPDX-License-Identifier: GPL-2.0 */
		#ifndef _ASM_GENERIC_UNWIND_USER_H
		#define _ASM_GENERIC_UNWIND_USER_H

		#endif /* _ASM_GENERIC_UNWIND_USER_H */

include/linux/unwind_user.h

0 → 100644

+14 −0

Original line number	Diff line number	Diff line
		/* SPDX-License-Identifier: GPL-2.0 */
		#ifndef _LINUX_UNWIND_USER_H
		#define _LINUX_UNWIND_USER_H

		#include <linux/unwind_user_types.h>
		#include <asm/unwind_user.h>

		#ifndef ARCH_INIT_USER_FP_FRAME
		#define ARCH_INIT_USER_FP_FRAME
		#endif

		int unwind_user(struct unwind_stacktrace *trace, unsigned int max_entries);

		#endif /* _LINUX_UNWIND_USER_H */