From: KaFai Wan <kafai.wan@linux.dev>
To: Eduard Zingerman <eddyz87@gmail.com>,
Puranjay Mohan <puranjay12@gmail.com>
Cc: puranjay@kernel.org, xukuohai@huaweicloud.com, ast@kernel.org,
daniel@iogearbox.net, john.fastabend@gmail.com,
andrii@kernel.org, martin.lau@linux.dev, song@kernel.org,
yonghong.song@linux.dev, kpsingh@kernel.org, sdf@fomichev.me,
haoluo@google.com, jolsa@kernel.org, mykolal@fb.com,
shuah@kernel.org, mrpre@163.com, linux-kernel@vger.kernel.org,
bpf@vger.kernel.org, linux-kselftest@vger.kernel.org
Subject: Re: [PATCH bpf v2 2/2] selftests/bpf: Add socket filter attach test
Date: Sat, 16 Aug 2025 23:14:54 +0800 [thread overview]
Message-ID: <06952937f3dd04e7f68bbd288da23f00ae83c213.camel@linux.dev> (raw)
In-Reply-To: <35c18502a4870d8a833c1c9af20b85ca3f8a0ff6.camel@gmail.com>
On Thu, 2025-08-14 at 09:06 -0700, Eduard Zingerman wrote:
> On Thu, 2025-08-14 at 13:23 +0200, Puranjay Mohan wrote:
> > On Thu, Aug 14, 2025 at 2:35 AM Eduard Zingerman
> > <eddyz87@gmail.com> wrote:
> > >
> > > On Wed, 2025-08-13 at 23:29 +0800, KaFai Wan wrote:
> > > > This test verifies socket filter attachment functionality on
> > > > architectures
> > > > supporting either BPF JIT compilation or the interpreter.
> > > >
> > > > It specifically validates the fallback to interpreter behavior
> > > > when JIT fails,
> > > > particularly targeting ARMv6 devices with the following
> > > > configuration:
> > > > # CONFIG_BPF_JIT_ALWAYS_ON is not set
> > > > CONFIG_BPF_JIT_DEFAULT_ON=y
> > > >
> > > > Signed-off-by: KaFai Wan <kafai.wan@linux.dev>
> > > > ---
> > >
> > > This test should not be landed as-is, first let's do an analysis
> > > for
> > > why the program fails to jit compile on arm.
> > >
> > > I modified kernel to dump BPF program before jit attempt, but
> > > don't
> > > see anything obviously wrong with it. The patch to get
> > > disassembly
> > > and disassembly itself with resolved kallsyms are attached.
> > >
> > > Can someone with access to ARM vm/machine take a looks at this?
> > > Puranjay, Xu, would you have some time?
> >
> > Hi Eduard,
> > Thanks for the email, I will look into it.
> >
> > Let me try to boot a kernel on ARMv6 qemu and reproduce this.
>
> Thank you, Puranjay,
>
> While looking at the code yesterday I found a legit case for failing
> to jit on armv6:
>
> https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git/tree/arch/arm/net/bpf_jit_32.c#n445
> https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git/tree/arch/arm/net/bpf_jit_32.c#n2089
>
> But attached program does not seem to be that big to hit 0xfff
> boundary.
Hi Eduard, Puranjay
OpenWRT users reported several tests that aren't working properly,
which may be helpful.
https://github.com/openwrt/openwrt/issues/19405#issuecomment-3121390534
https://github.com/openwrt/openwrt/issues/19405#issuecomment-3176820629
--
Thanks,
KaFai
next prev parent reply other threads:[~2025-08-16 15:15 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-08-13 15:29 [PATCH bpf v2 0/2] bpf: Allow fall back to interpreter for programs with stack size <= 512 KaFai Wan
2025-08-13 15:29 ` [PATCH bpf v2 1/2] " KaFai Wan
2025-08-13 15:29 ` [PATCH bpf v2 2/2] selftests/bpf: Add socket filter attach test KaFai Wan
2025-08-14 0:35 ` Eduard Zingerman
2025-08-14 11:23 ` Puranjay Mohan
2025-08-14 16:06 ` Eduard Zingerman
2025-08-16 15:14 ` KaFai Wan [this message]
2025-08-25 19:27 ` Puranjay Mohan
2025-08-25 19:32 ` Eduard Zingerman
2025-08-27 11:16 ` Puranjay Mohan
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