linux-kernel - Re: [PATCH v5 bpf-next 0/3] libbpf: Fix event name too long error and add tests

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Message-ID: <aADi-FfI-PljQzcO@krava>
Date: Thu, 17 Apr 2025 13:16:08 +0200
From: Jiri Olsa <olsajiri@...il.com>
To: Feng Yang <yangfeng59949@....com>
Cc: ast@...nel.org, daniel@...earbox.net, andrii@...nel.org,
	martin.lau@...ux.dev, eddyz87@...il.com, song@...nel.org,
	yonghong.song@...ux.dev, john.fastabend@...il.com,
	kpsingh@...nel.org, sdf@...ichev.me, haoluo@...gle.com,
	hengqi.chen@...il.com, olsajiri@...il.com, bpf@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 bpf-next 0/3] libbpf: Fix event name too long error
 and add tests

On Thu, Apr 17, 2025 at 09:48:45AM +0800, Feng Yang wrote:
> From: Feng Yang <yangfeng@...inos.cn>
> 
> Hi everyone,
> 
> This series tries to fix event name too long error and add tests.
> 
> When the binary path is excessively long, the generated probe_name in libbpf
> exceeds the kernel's MAX_EVENT_NAME_LEN limit (64 bytes).
> This causes legacy uprobe event attachment to fail with error code -22.
> 
> The fix reorders the fields to place the unique ID before the name.
> This ensures that even if truncation occurs via snprintf, the unique ID
> remains intact, preserving event name uniqueness. Additionally, explicit
> checks with MAX_EVENT_NAME_LEN are added to enforce length constraints.
> ---
> Changes in v5:
> - use strrchr instead of basename.
> - kprobe_test add __weak. Thanks, Andrii Nakryiko!
> - Link to v4: https://lore.kernel.org/all/20250415093907.280501-1-yangfeng59949@163.com/

Acked-by: Jiri Olsa <jolsa@...nel.org>

thanks,
jirka


> 
> Changes in v4:
> - add changelog. 
> - gen_uprobe_legacy_event_name and gen_kprobe_legacy_event_name are combined into a function
> - kprobe_test use normal module function. Thanks, Jiri Olsa!
> - Link to v3: https://lore.kernel.org/bpf/20250414093402.384872-1-yangfeng59949@163.com/
> 
> Changes in v3:
> - add __sync_fetch_and_add(&index) and let snprintf() do the trimming. Thanks, Andrii Nakryiko!
> - add selftests.
> - Link to v2: https://lore.kernel.org/all/20250411080545.319865-1-yangfeng59949@163.com/
> 
> Changes in v2:
> - Use basename() and %.32s to fix. Thanks, Hengqi Chen!
> - Link to v1: https://lore.kernel.org/all/20250410052712.206785-1-yangfeng59949@163.com/
> 
> Feng Yang (3):
>   libbpf: Fix event name too long error
>   selftests/bpf: Add test for attaching uprobe with long event names
>   selftests/bpf: Add test for attaching kprobe with long event names
> 
>  tools/lib/bpf/libbpf.c                        | 43 ++++------
>  .../selftests/bpf/prog_tests/attach_probe.c   | 84 +++++++++++++++++++
>  .../selftests/bpf/test_kmods/bpf_testmod.c    |  4 +
>  3 files changed, 104 insertions(+), 27 deletions(-)
> 
> -- 
> 2.43.0
>