linux-kernel - Re: [PATCH bpf-next v1 1/2] bpf: Add kfuncs for detecting execution context

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Message-ID: <8764fe64-d896-460e-8e0c-cd81667c57b9@gmail.com>
Date: Wed, 22 Oct 2025 20:55:55 +0800
From: Leon Hwang <hffilwlqm@...il.com>
To: Jiayuan Chen <jiayuan.chen@...ux.dev>, bpf@...r.kernel.org
Cc: Alexei Starovoitov <ast@...nel.org>,
 Daniel Borkmann <daniel@...earbox.net>, Andrii Nakryiko <andrii@...nel.org>,
 Martin KaFai Lau <martin.lau@...ux.dev>, Eduard Zingerman
 <eddyz87@...il.com>, Song Liu <song@...nel.org>,
 Yonghong Song <yonghong.song@...ux.dev>,
 John Fastabend <john.fastabend@...il.com>, KP Singh <kpsingh@...nel.org>,
 Stanislav Fomichev <sdf@...ichev.me>, Hao Luo <haoluo@...gle.com>,
 Jiri Olsa <jolsa@...nel.org>, Shuah Khan <shuah@...nel.org>,
 linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org
Subject: Re: [PATCH bpf-next v1 1/2] bpf: Add kfuncs for detecting execution
 context



On 2025/10/22 19:33, Jiayuan Chen wrote:
> This path introduces several kfuncs to help BPF programs determine their
> current execution context. When hooking functions for statistics, we often
> need to use current->comm to get the process name.
>
> However, these hooked functions can be called from either process context
> or interrupt context. When called from interrupt context, the current we
> obtain may refer to the process that was interrupted, which may not be
> what we need.
>
> These new kfuncs expose APIs that allow users to determine the actual
> execution context.

Hi Jiayuan,

Rather than introducing multiple kfuncs to determine the current
execution context, this can already be achieved by using the
'bpf_this_cpu_ptr()' helper to read the underlying preemption count.

Please refer to my earlier patch,
"selftests/bpf: Introduce experimental bpf_in_interrupt()"[1], which
demonstrates this approach.

Links:
[1] https://lore.kernel.org/bpf/20250903140438.59517-1-leon.hwang@linux.dev/

Thanks,
Leon

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