From: "Alexei Starovoitov" <alexei.starovoitov@gmail.com>
To: "Daniel Borkmann" <daniel@iogearbox.net>,
"Jiri Olsa" <olsajiri@gmail.com>
Cc: <bpf@vger.kernel.org>, <andrii@kernel.org>,
"Menglong Dong" <dongml2@chinatelecom.cn>,
"Steven Rostedt" <rostedt@goodmis.org>
Subject: Re: [PATCH bpf 1/2] x86/ftrace: Use jmp mode only where functions are aligned
Date: Sun, 25 Oct 2026 17:38:05 +0000 [thread overview]
Message-ID: <DME3OUNAYUV6.2JD94UVU3DBNP@gmail.com> (raw)
In-Reply-To: <8c2784c0-2b13-4cc2-b770-51bbb8006f26@iogearbox.net>
On Sun, Oct 25, 2026 at 08:27 AM Daniel Borkmann <daniel@iogearbox.net> wrote:
> I had the below first as well, but then saw that there were similar issues
> regarding function alignment in the past and they were solved on kconfig
> level, some picks:
>
> - b3f11af9b2ce ("arm64: ftrace: forbid CALL_OPS with CC_OPTIMIZE_FOR_SIZE")
> - a743f26d03a9 ("arm64: ftrace: Don't forbid CALL_OPS+CC_OPTIMIZE_FOR_SIZE with Clang")
> - c41bf4326c7b ("riscv: ftrace: align patchable functions to 4 Byte boundary")
> - 9315e22b0c0a ("arm64: ftrace: allow DIRECT_CALLS without CALL_OPS")
I think those are different. They need the traced function to be aligned
by design. CALL_OPS keeps an 8 byte literal in front of it.
Here nothing needs C functions to be aligned. The callback is hit by
the bit 0 check only because it goes through ftrace_call_replace().
> But I can also spin a v2 with the code change instead if preferred.
I don't insist, but imo my approach is cleaner.
prev parent reply other threads:[~2026-10-25 17:38 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-10-24 7:37 [PATCH bpf 1/2] x86/ftrace: Use jmp mode only where functions are aligned Daniel Borkmann
2026-10-24 7:37 ` [PATCH bpf 2/2] selftests/bpf: Test kprobe and fentry programs on one function Daniel Borkmann
2026-10-24 19:10 ` [PATCH bpf 1/2] x86/ftrace: Use jmp mode only where functions are aligned Alexei Starovoitov
2026-10-25 13:18 ` Jiri Olsa
2026-10-25 15:27 ` Daniel Borkmann
2026-10-25 17:38 ` Alexei Starovoitov [this message]
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