linux-kernel - Re: [PATCH bpf-next v4 3/8] resolve_btfids: Introduce enum btf_id

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Message-Id: <106b6e71bce75b8f12a85f2f99e75129e67af7287f6d81fa912589ece14044f9@mail.kernel.org>
Date: Thu, 18 Dec 2025 00:47:30 +0000 (UTC)
From: bot+bpf-ci@...nel.org
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Subject: Re: [PATCH bpf-next v4 3/8] resolve_btfids: Introduce enum btf_id_kind

> diff --git a/tools/bpf/resolve_btfids/main.c b/tools/bpf/resolve_btfids/main.c
> index b4caae1170dd..da8c7d127632 100644
> --- a/tools/bpf/resolve_btfids/main.c
> +++ b/tools/bpf/resolve_btfids/main.c

[ ... ]

> @@ -260,22 +279,36 @@ static char *get_id(const char *prefix_end)
>  	return id;
>  }
>
> -static struct btf_id *add_set(struct object *obj, char *name, bool is_set8)
> +static struct btf_id *add_set(struct object *obj, char *name, enum btf_id_kind kind)
>  {
> +	int len = strlen(name);
> +	int prefixlen;
> +	char *id;
> +
>  	/*
>  	 * __BTF_ID__set__name
>  	 * name =    ^
>  	 * id   =         ^
>  	 */
> -	char *id = name + (is_set8 ? sizeof(BTF_SET8 "__") : sizeof(BTF_SET "__")) - 1;
> -	int len = strlen(name);
> +	switch (kind) {
> +	case BTF_ID_KIND_SET:
> +		prefixlen = sizeof(BTF_SET "__") - 1;
> +		break;
> +	case BTF_ID_KIND_SET8:
> +		prefixlen = sizeof(BTF_SET8 "__") - 1;
> +		break;
> +	default:
> +		pr_err("Unexpected kind %d passed to %s() for symbol %s\n", kind, __func__, name);
> +		return NULL;
> +	}
> +
> +	id = name + prefixlen - 1;

Is this off by one? The original code computed:

    id = name + sizeof(BTF_SET "__") - 1

For BTF_SET ("set"), this gives: name + sizeof("set__") - 1 = name + 6 - 1 = name + 5

The new code computes:

    prefixlen = sizeof(BTF_SET "__") - 1 = 6 - 1 = 5
    id = name + prefixlen - 1 = name + 5 - 1 = name + 4

The -1 appears to be applied twice now, once in the prefixlen assignment and
again when computing id. Should this line be:

    id = name + prefixlen;

>  	if (id >= name + len) {
>  		pr_err("FAILED to parse set name: %s\n", name);
>  		return NULL;
>  	}
>
> -	return btf_id__add(&obj->sets, id, true);
> +	return btf_id__add_unique(&obj->sets, id, kind);
>  }


---
AI reviewed your patch. Please fix the bug or email reply why it's not a bug.
See: https://github.com/kernel-patches/vmtest/blob/master/ci/claude/README.md

CI run summary: https://github.com/kernel-patches/bpf/actions/runs/20321956014