From: Indu Bhagat <indu.bhagat@oracle.com>
To: Dylan Hatch <dylanbhatch@google.com>,
Josh Poimboeuf <jpoimboe@kernel.org>
Cc: Steven Rostedt <rostedt@goodmis.org>,
Peter Zijlstra <peterz@infradead.org>,
Will Deacon <will@kernel.org>,
Catalin Marinas <catalin.marinas@arm.com>,
Jiri Kosina <jikos@kernel.org>,
Roman Gushchin <roman.gushchin@linux.dev>,
Weinan Liu <wnliu@google.com>,
Mark Rutland <mark.rutland@arm.com>,
Ian Rogers <irogers@google.com>,
linux-toolchains@vger.kernel.org, linux-kernel@vger.kernel.org,
live-patching@vger.kernel.org, joe.lawrence@redhat.com,
Puranjay Mohan <puranjay@kernel.org>, Song Liu <song@kernel.org>,
Prasanna Kumar T S M <ptsm@linux.microsoft.com>
Subject: Re: [PATCH v2 6/6] unwind: arm64: Add reliable stacktrace with sframe unwinder.
Date: Tue, 18 Nov 2025 23:12:01 -0800 [thread overview]
Message-ID: <03540be1-7687-4bdc-bf38-dfd713ea09db@oracle.com> (raw)
In-Reply-To: <CADBMgpzmzyQgs4K3XoYf5h=C7vv-FDfNb5wharucyeoxUKo4bg@mail.gmail.com>
On 11/18/25 7:17 PM, Dylan Hatch wrote:
>> For sframe v3, I believe Indu is planning to add support for marking the
>> outermost frame. That would be one definitive way to know that the
>> stack trace made it to the end.
> How would this work? Is there a way of determining at compile time
> which functions would end up being the outermost frame?
No, the compiler does not emit such a marker.
SFrame information is generated by assembler using the .cfi_*
directives. For the outermost functions, they need to be marked with a:
.cfi_undefined RA
where RA is the default return address register for the ABI.
This mechanism is formalised in the DWARF standard:
"If a Return Address register is defined in the virtual unwind table,
and its rule is undefined (for example, by DW_CFA_undefined), then there
is no return address and no call address, and the virtual unwind of
stack activations is complete."
SFrame relies on this to emit a marker for identifying outermost frame.
next prev parent reply other threads:[~2025-11-19 7:12 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-09-04 22:38 [PATCH v2 0/6] unwind, arm64: add sframe unwinder for kernel Dylan Hatch
2025-09-04 22:38 ` [PATCH v2 1/6] unwind: build kernel with sframe info Dylan Hatch
2025-11-14 13:34 ` Will Deacon
2025-11-19 14:59 ` Jens Remus
2025-09-04 22:38 ` [PATCH v2 2/6] arm64: entry: add unwind info for various kernel entries Dylan Hatch
2025-09-04 22:38 ` [PATCH v2 3/6] unwind: add sframe v2 header Dylan Hatch
2025-09-04 22:38 ` [PATCH v2 4/6] unwind: Implement generic sframe unwinder library Dylan Hatch
2025-09-09 16:44 ` Puranjay Mohan
2025-09-09 18:39 ` Indu Bhagat
2025-09-04 22:38 ` [PATCH v2 5/6] arm64/module, unwind: Add sframe support for modules Dylan Hatch
2025-09-04 22:38 ` [PATCH v2 6/6] unwind: arm64: Add reliable stacktrace with sframe unwinder Dylan Hatch
2025-09-17 23:41 ` Josh Poimboeuf
2025-11-15 6:44 ` Dylan Hatch
2025-11-17 23:01 ` Josh Poimboeuf
2025-11-19 3:17 ` Dylan Hatch
2025-11-19 7:12 ` Indu Bhagat [this message]
2025-09-29 19:46 ` [PATCH v2 0/6] unwind, arm64: add sframe unwinder for kernel Song Liu
2025-09-29 19:55 ` Puranjay Mohan
2025-11-15 6:50 ` Dylan Hatch
2025-11-17 23:06 ` Josh Poimboeuf
2025-11-17 23:42 ` Steven Rostedt
2025-11-18 0:10 ` Josh Poimboeuf
2025-11-18 0:49 ` Puranjay Mohan
2025-11-18 5:18 ` Josh Poimboeuf
2025-11-18 18:20 ` Steven Rostedt
2025-11-18 18:29 ` Indu Bhagat
2025-11-17 23:50 ` Puranjay Mohan
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