linux-kernel - Re: [PATCH bpf-next 1/2] bpf: Remove bpf_jit

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Message-ID: <d3949501-8f7d-57c4-b3fe-bcc3b24c09d8@isovalent.com>
Date:   Thu, 15 Apr 2021 16:41:23 +0100
From:   Quentin Monnet <quentin@...valent.com>
To:     Daniel Borkmann <daniel@...earbox.net>,
        Jianlin Lv <Jianlin.Lv@....com>, bpf@...r.kernel.org
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Subject: Re: [PATCH bpf-next 1/2] bpf: Remove bpf_jit_enable=2 debugging mode

2021-04-15 16:37 UTC+0200 ~ Daniel Borkmann <daniel@...earbox.net>
> On 4/15/21 11:32 AM, Jianlin Lv wrote:
>> For debugging JITs, dumping the JITed image to kernel log is discouraged,
>> "bpftool prog dump jited" is much better way to examine JITed dumps.
>> This patch get rid of the code related to bpf_jit_enable=2 mode and
>> update the proc handler of bpf_jit_enable, also added auxiliary
>> information to explain how to use bpf_jit_disasm tool after this change.
>>
>> Signed-off-by: Jianlin Lv <Jianlin.Lv@....com>

Hello,

For what it's worth, I have already seen people dump the JIT image in
kernel logs in Qemu VMs running with just a busybox, not for kernel
development, but in a context where buiding/using bpftool was not
possible. Maybe not a common case, but still, removing the debugging
mode will make that impossible. Is there a particular incentive to
remove the feature?

Best regards,
Quentin