linux-kernel - Re: [PATCH bpf v2 2/2] selftests/bpf: Add socket filter attach test

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Message-ID: <eb6f9ba4acccc7685596a8f1b282667a43d51ca8.camel@gmail.com>
Date: Wed, 13 Aug 2025 17:35:01 -0700
From: Eduard Zingerman <eddyz87@...il.com>
To: KaFai Wan <kafai.wan@...ux.dev>, puranjay@...nel.org, 
	xukuohai@...weicloud.com
Cc: ast@...nel.org, daniel@...earbox.net, john.fastabend@...il.com, 
	andrii@...nel.org, martin.lau@...ux.dev, song@...nel.org,
 yonghong.song@...ux.dev, 	kpsingh@...nel.org, sdf@...ichev.me,
 haoluo@...gle.com, jolsa@...nel.org, 	mykolal@...com, shuah@...nel.org,
 mrpre@....com, linux-kernel@...r.kernel.org, 	bpf@...r.kernel.org,
 linux-kselftest@...r.kernel.org
Subject: Re: [PATCH bpf v2 2/2] selftests/bpf: Add socket filter attach test

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@...ux.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?

[...]

View attachment "filter-show-prog.diff" of type "text/x-patch" (1041 bytes)

View attachment "socket-filter-prog.txt" of type "text/plain" (6800 bytes)