Re: [PATCH bpf-next v11 04/10] libbpf: Probe percpu data feature

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] The newly added feature probe `FEAT_PERCPU_DATA` is never used to make capability decisions.
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--- Patch [4]: [PATCH bpf-next v11 04/10] libbpf: Probe percpu data feature ---
commit 925264284b89c241360ff401bd914f9c19997613
Author: Leon Hwang <[email protected]>

libbpf: Probe percpu data feature

This commit adds a feature probe to detect if the kernel supports global
percpu data. It aims to allow libbpf to fail predictably when this feature
is unavailable on older kernels.

> diff --git a/tools/lib/bpf/features.c b/tools/lib/bpf/features.c
> index b7e388f99d0bb..ef9581c113035 100644
> --- a/tools/lib/bpf/features.c
> +++ b/tools/lib/bpf/features.c
[ ... ]
> @@ -707,6 +739,9 @@ static struct kern_feature_desc {
>  	[FEAT_BPF_SYSCALL_COMMON_ATTRS] = {
>  		"BPF syscall common attributes support", probe_bpf_syscall_common_attrs,
>  	},
> +	[FEAT_PERCPU_DATA] = {
> +		"kernel supports percpu data", probe_kern_percpu_data,
> +	},
>  };

[Severity: Medium]
Are there any callers that actually query this new feature probe?

The commit message notes that libbpf can make capability decisions early
and fail predictably when global percpu data is unavailable. However,
FEAT_PERCPU_DATA appears to only be defined and registered, without being
queried in the loader code.

Is there a missing update to the loader, perhaps using kernel_supports(),
that checks this flag before attempting to load percpu global data?

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/[email protected]?part=4