From: Kumar Kartikeya Dwivedi <memxor@gmail.com>
To: bot+bpf-ci@kernel.org
Cc: bpf@vger.kernel.org, ast@kernel.org, andrii@kernel.org,
daniel@iogearbox.net, eddyz87@gmail.com, emil@etsalapatis.com,
ihor.solodrai@linux.dev, kkd@meta.com, kernel-team@meta.com,
martin.lau@kernel.org, yonghong.song@linux.dev, mason@kernel.org
Subject: Re: [RFC PATCH bpf-next v1 01/11] bpf: Give a helper a way to call its callback with a pad
Date: Wed, 28 Oct 2026 03:15:19 +0100 [thread overview]
Message-ID: <20261028021519.1203900-8-memxor@gmail.com> (raw)
In-Reply-To: <81df2f63249021a13160d155eccab3bbd591e464d05db9765a15427c3cc97650@mail.kernel.org>
On Wed Oct 28, 2026 at 2:39 AM CET, bot+bpf-ci wrote:
> [...]
> TL;DR:
> - bpf_unwind_leave() may misbehave if the helper is ftrace/kretprobe/fexit
> traced: unwind lost, pointer or reference treated as scalar
Right. Every function with a pad is notrace and no kprobe target in the
next version, as the verifier lets only fentry attach to a subprog that
unwinds, with a test that fexit on bpf_loop() is refused.
> - With gcc, bpf_call_cb() register variables may be clobbered by KASAN/KCSAN
> calls, possibly jumping to a bad address
Right, for a call in the evaluation of a later argument, which the
compiler does not keep the register variables across. The next version
evaluates every argument into a temporary first.
> [...]
next prev parent reply other threads:[~2026-10-28 2:15 UTC|newest]
Thread overview: 46+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-10-28 0:44 [RFC PATCH bpf-next v1 00/11] Unwinding for synchronous callbacks Kumar Kartikeya Dwivedi
2026-10-28 0:44 ` [RFC PATCH bpf-next v1 01/11] bpf: Give a helper a way to call its callback with a pad Kumar Kartikeya Dwivedi
2026-10-28 1:20 ` sashiko-bot
2026-10-28 2:15 ` Kumar Kartikeya Dwivedi
2026-10-28 1:39 ` bot+bpf-ci
2026-10-28 2:15 ` Kumar Kartikeya Dwivedi [this message]
2026-10-28 0:44 ` [RFC PATCH bpf-next v1 02/11] bpf, arm64: Let the pad after a helper call have r0 Kumar Kartikeya Dwivedi
2026-10-28 1:02 ` sashiko-bot
2026-10-28 2:15 ` Kumar Kartikeya Dwivedi
2026-10-28 0:44 ` [RFC PATCH bpf-next v1 03/11] bpf: Let a callback unwind into the pad of its helper Kumar Kartikeya Dwivedi
2026-10-28 1:31 ` sashiko-bot
2026-10-28 2:15 ` Kumar Kartikeya Dwivedi
2026-10-28 1:39 ` bot+bpf-ci
2026-10-28 2:15 ` Kumar Kartikeya Dwivedi
2026-10-28 0:44 ` [RFC PATCH bpf-next v1 04/11] bpf: Give the inlined bpf_loop a pad Kumar Kartikeya Dwivedi
2026-10-28 1:10 ` sashiko-bot
2026-10-28 2:15 ` Kumar Kartikeya Dwivedi
2026-10-28 0:44 ` [RFC PATCH bpf-next v1 05/11] bpf: Let the callback of bpf_loop unwind Kumar Kartikeya Dwivedi
2026-10-28 1:19 ` sashiko-bot
2026-10-28 2:15 ` Kumar Kartikeya Dwivedi
2026-10-28 1:25 ` bot+bpf-ci
2026-10-28 2:15 ` Kumar Kartikeya Dwivedi
2026-10-28 0:44 ` [RFC PATCH bpf-next v1 06/11] bpf: Let the callback of bpf_for_each_map_elem unwind Kumar Kartikeya Dwivedi
2026-10-28 1:25 ` bot+bpf-ci
2026-10-28 2:15 ` Kumar Kartikeya Dwivedi
2026-10-28 0:44 ` [RFC PATCH bpf-next v1 07/11] bpf: Let the callback of bpf_find_vma unwind Kumar Kartikeya Dwivedi
2026-10-28 1:08 ` sashiko-bot
2026-10-28 2:15 ` Kumar Kartikeya Dwivedi
2026-10-28 0:44 ` [RFC PATCH bpf-next v1 08/11] bpf: Let the callback of bpf_user_ringbuf_drain unwind Kumar Kartikeya Dwivedi
2026-10-28 1:01 ` sashiko-bot
2026-10-28 1:04 ` Kumar Kartikeya Dwivedi
2026-10-28 0:44 ` [RFC PATCH bpf-next v1 09/11] bpf: Let the comparator of bpf_rbtree_add unwind Kumar Kartikeya Dwivedi
2026-10-28 1:21 ` sashiko-bot
2026-10-28 2:15 ` Kumar Kartikeya Dwivedi
2026-10-28 1:25 ` bot+bpf-ci
2026-10-28 2:15 ` Kumar Kartikeya Dwivedi
2026-10-28 0:44 ` [RFC PATCH bpf-next v1 10/11] selftests/bpf: Test callbacks that unwind Kumar Kartikeya Dwivedi
2026-10-28 1:25 ` bot+bpf-ci
2026-10-28 2:15 ` Kumar Kartikeya Dwivedi
2026-10-28 0:44 ` [RFC PATCH bpf-next v1 11/11] selftests/bpf: Test what a callback unwinds with Kumar Kartikeya Dwivedi
2026-10-28 5:06 ` [RFC PATCH bpf-next v1 00/11] Unwinding for synchronous callbacks Alexei Starovoitov
2026-10-28 10:20 ` Kumar Kartikeya Dwivedi
2026-10-28 20:17 ` Alexei Starovoitov
2026-10-28 21:42 ` Kumar Kartikeya Dwivedi
2026-10-28 23:12 ` Eduard Zingerman
2026-10-29 0:14 ` Alexei Starovoitov
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