netdev - Re: [PATCH bpf-next v2 0/2] bpf: Introduce user log

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <b40831db-1a64-6fa6-ddcb-d33068882e90@gmail.com>
Date: Sun, 9 Jul 2023 11:44:42 +0800
From: Leon Hwang <hffilwlqm@...il.com>
To: Daniel Xu <dxu@...uu.xyz>
Cc: ast@...nel.org, daniel@...earbox.net, john.fastabend@...il.com,
 andrii@...nel.org, martin.lau@...ux.dev, song@...nel.org, yhs@...com,
 kpsingh@...nel.org, sdf@...gle.com, haoluo@...gle.com, jolsa@...nel.org,
 davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
 pabeni@...hat.com, hawk@...nel.org, tangyeechou@...il.com,
 kernel-patches-bot@...com, bpf@...r.kernel.org,
 linux-kernel@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH bpf-next v2 0/2] bpf: Introduce user log



On 2023/7/9 06:02, Daniel Xu wrote:
> Hi Leon,
> 
> On Sat, Jul 08, 2023 at 12:07:48PM +0800, Leon Hwang wrote:
>> This series introduces bpf user log to transfer error message from
>> kernel space to user space when users provide buffer to receive the
>> error message.
>>
>> Especially, when to attach XDP to device, it can transfer the error
>> message along with errno from dev_xdp_attach() to user space, if error
>> happens in dev_xdp_attach().
> 
> Have you considered adding a tracepoint instead? With some TP_printk()
> stuff I think you can achieve a similar result without having to do
> go through changing uapi.

If just for dev_xdp_attach(), I think netlink approach is better than
tracepoint approach.

As for BPF syscall, error message along with errno through uapi is a
good UX, like "create link: invalid argument (Invalid XDP flags for BPF
link attachment)" when failed to attach XDP to a device. Hence, users
are able to know the error details instead of -EINVAL or "invalid
argument" only.

Furthermore, as for other BPF syscall subcommands, we are able to
provide error message along with errno by bpf_ulog_once(&attr->xxx.ulog,
"An error").