linux-kernel - Re: [PATCH bpf-next v2 3/4] resolve_btfids: introduce enum btf_id

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Message-ID: <CAEf4Bza+L_RL_d7JFFLmzkYj2dbnT8rDgqwCat2zLOekToRm-g@mail.gmail.com>
Date: Mon, 1 Dec 2025 09:27:03 -0800
From: Andrii Nakryiko <andrii.nakryiko@...il.com>
To: Ihor Solodrai <ihor.solodrai@...ux.dev>
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>, Nathan Chancellor <nathan@...nel.org>, 
	Nicolas Schier <nicolas.schier@...ux.dev>, 
	Nick Desaulniers <nick.desaulniers+lkml@...il.com>, Bill Wendling <morbo@...gle.com>, 
	Justin Stitt <justinstitt@...gle.com>, Alan Maguire <alan.maguire@...cle.com>, 
	Donglin Peng <dolinux.peng@...il.com>, bpf@...r.kernel.org, dwarves@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-kbuild@...r.kernel.org
Subject: Re: [PATCH bpf-next v2 3/4] resolve_btfids: introduce enum btf_id_kind

On Thu, Nov 27, 2025 at 10:53 AM Ihor Solodrai <ihor.solodrai@...ux.dev> wrote:
>
> Instead of using multiple flags, make struct btf_id tagged with an
> enum value indicating its kind in the context of resolve_btfids.
>
> Signed-off-by: Ihor Solodrai <ihor.solodrai@...ux.dev>
> ---
>  tools/bpf/resolve_btfids/main.c | 62 ++++++++++++++++++++++-----------
>  1 file changed, 42 insertions(+), 20 deletions(-)

[...]

>
> -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)
>  {
>         /*
>          * __BTF_ID__set__name
>          * name =    ^
>          * id   =         ^
>          */
> -       char *id = name + (is_set8 ? sizeof(BTF_SET8 "__") : sizeof(BTF_SET "__")) - 1;
> +       int prefixlen = kind == BTF_ID_KIND_SET8 ? sizeof(BTF_SET8 "__") : sizeof(BTF_SET "__");
> +       char *id = name + prefixlen - 1;
>         int len = strlen(name);
> +       struct btf_id *btf_id;
>
>         if (id >= name + len) {
>                 pr_err("FAILED to parse set name: %s\n", name);
>                 return NULL;
>         }
>
> -       return btf_id__add(&obj->sets, id, true);
> +       btf_id = btf_id__add(&obj->sets, id, true);
> +       if (btf_id)
> +               btf_id->kind = kind;
> +
> +       return btf_id;
>  }
>
>  static struct btf_id *add_symbol(struct rb_root *root, char *name, size_t size)
>  {
> +       struct btf_id *btf_id;
>         char *id;
>
>         id = get_id(name + size);
> @@ -288,7 +301,11 @@ static struct btf_id *add_symbol(struct rb_root *root, char *name, size_t size)
>                 return NULL;
>         }
>
> -       return btf_id__add(root, id, false);
> +       btf_id = btf_id__add(root, id, false);
> +       if (btf_id)
> +               btf_id->kind = BTF_ID_KIND_SYM;

seeing this pattern repeated, wouldn't it make sense to just pass this
kind to btf_id__add() and set it there?

> +
> +       return btf_id;
>  }
>

[...]

> @@ -643,7 +656,7 @@ static int id_patch(struct object *obj, struct btf_id *id)
>         int i;
>
>         /* For set, set8, id->id may be 0 */
> -       if (!id->id && !id->is_set && !id->is_set8) {
> +       if (!id->id && id->kind == BTF_ID_KIND_SYM) {

nit: comment says the exception is specifically for SET and SET8, so I
think checking for those two instead of for SYM (implying that only
other possible options are set and set8) would be a bit more
future-proof?

>                 pr_err("WARN: resolve_btfids: unresolved symbol %s\n", id->name);
>                 warnings++;
>         }

[...]