linux-kernel - Re: [PATCH 2/2] x86/unwind/orc: Support reliable unwinding through BPF stack frames

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Message-ID: <CAPhsuW5+0F1rVvYyWCq+cAOim2=FE3FmVMH23sLr1Vft55FGpg@mail.gmail.com>
Date: Tue, 2 Dec 2025 10:59:19 -0800
From: Song Liu <song@...nel.org>
To: Josh Poimboeuf <jpoimboe@...nel.org>
Cc: x86@...nel.org, linux-kernel@...r.kernel.org, 
	live-patching@...r.kernel.org, bpf@...r.kernel.org, 
	Andrey Grodzovsky <andrey.grodzovsky@...wdstrike.com>, Petr Mladek <pmladek@...e.com>, 
	Raja Khan <raja.khan@...wdstrike.com>, Miroslav Benes <mbenes@...e.cz>, 
	Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, 
	Andrii Nakryiko <andrii@...nel.org>, Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH 2/2] x86/unwind/orc: Support reliable unwinding through
 BPF stack frames

On Tue, Dec 2, 2025 at 10:20 AM Josh Poimboeuf <jpoimboe@...nel.org> wrote:
>
> BPF JIT programs and trampolines use a frame pointer, so the current ORC
> unwinder strategy of falling back to frame pointers (when an ORC entry
> is missing) usually works in practice when unwinding through BPF JIT
> stack frames.
>
> However, that frame pointer fallback is just a guess, so the unwind gets
> marked unreliable for live patching, which can cause livepatch
> transition stalls.
>
> Make the common case reliable by calling the bpf_has_frame_pointer()
> helper to detect the valid frame pointer region of BPF JIT programs and
> trampolines.
>
> Fixes: ee9f8fce9964 ("x86/unwind: Add the ORC unwinder")
> Reported-by: Andrey Grodzovsky <andrey.grodzovsky@...wdstrike.com>
> Closes: https://lore.kernel.org/0e555733-c670-4e84-b2e6-abb8b84ade38@crowdstrike.com
> Signed-off-by: Josh Poimboeuf <jpoimboe@...nel.org>

Acked-by: Song Liu <song@...nel.org>