linux.git/kernel/unwind/user.c, branch v6.18.21 Clone of https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git unwind_user/x86: Teach FP unwind about start of function 2026-03-12T11:09:28+00:00 Peter Zijlstra peterz@infradead.org 2025-10-24T10:31:10+00:00 f7df71d26b308a3588e240300740e11e844845cf [ Upstream commit ae25884ad749e7f6e0c3565513bdc8aa2554a425 ] When userspace is interrupted at the start of a function, before we get a chance to complete the frame, unwind will miss one caller. X86 has a uprobe specific fixup for this, add bits to the generic unwinder to support this. Suggested-by: Jens Remus <jremus@linux.ibm.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://patch.msgid.link/20251024145156.GM4068168@noisy.programming.kicks-ass.net Stable-dep-of: d55c571e4333 ("x86/uprobes: Fix XOL allocation failure for 32-bit tasks") Signed-off-by: Sasha Levin <sashal@kernel.org> 
[ Upstream commit ae25884ad749e7f6e0c3565513bdc8aa2554a425 ]

When userspace is interrupted at the start of a function, before we
get a chance to complete the frame, unwind will miss one caller.

X86 has a uprobe specific fixup for this, add bits to the generic
unwinder to support this.

Suggested-by: Jens Remus <jremus@linux.ibm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/20251024145156.GM4068168@noisy.programming.kicks-ass.net
Stable-dep-of: d55c571e4333 ("x86/uprobes: Fix XOL allocation failure for 32-bit tasks")
Signed-off-by: Sasha Levin <sashal@kernel.org>
unwind: Implement compat fp unwind 2026-03-12T11:09:27+00:00 Peter Zijlstra peterz@infradead.org 2025-09-23T11:27:34+00:00 6f553dbbb25d66a81f2b23057b5e26be685e77f5 [ Upstream commit c79dd946e370af3537edb854f210cba3a94b4516 ] It is important to be able to unwind compat tasks too. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://patch.msgid.link/20250924080119.613695709@infradead.org Stable-dep-of: d55c571e4333 ("x86/uprobes: Fix XOL allocation failure for 32-bit tasks") Signed-off-by: Sasha Levin <sashal@kernel.org> 
[ Upstream commit c79dd946e370af3537edb854f210cba3a94b4516 ]

It is important to be able to unwind compat tasks too.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/20250924080119.613695709@infradead.org
Stable-dep-of: d55c571e4333 ("x86/uprobes: Fix XOL allocation failure for 32-bit tasks")
Signed-off-by: Sasha Levin <sashal@kernel.org>
unwind: Simplify unwind_user_next_fp() alignment check 2026-03-12T11:09:27+00:00 Peter Zijlstra peterz@infradead.org 2025-09-23T11:04:09+00:00 5364f7bbd611a87cd123673e2549ab3e2e4a91ea [ Upstream commit 5578534e4b92350995a20068f2e6ea3186c62d7f ] 2^log_2(n) == n Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Steven Rostedt (Google) <rostedt@goodmis.org> Link: https://patch.msgid.link/20250924080119.497867836@infradead.org Stable-dep-of: d55c571e4333 ("x86/uprobes: Fix XOL allocation failure for 32-bit tasks") Signed-off-by: Sasha Levin <sashal@kernel.org> 
[ Upstream commit 5578534e4b92350995a20068f2e6ea3186c62d7f ]

  2^log_2(n) == n

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Link: https://patch.msgid.link/20250924080119.497867836@infradead.org
Stable-dep-of: d55c571e4333 ("x86/uprobes: Fix XOL allocation failure for 32-bit tasks")
Signed-off-by: Sasha Levin <sashal@kernel.org>
unwind_user: Add user space unwinding API with frame pointer support 2025-07-29T18:46:07+00:00 Josh Poimboeuf jpoimboe@kernel.org 2025-07-29T18:23:05+00:00 71753c6ed2bf2aee5be26c1bc06a94c9e3713ade 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> 
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>