Re: [PATCH bpf-next v2 11/21] bpf: Add tracing_multi link support for bpf progs

[Jiri Olsa <olsajiri@gmail.com>]

On Mon, Oct 12, 2026 at 11:40:13PM +0800, Leon Hwang wrote:

SNIP

> @@ -3787,64 +3796,129 @@ static const struct bpf_link_ops bpf_tracing_multi_link_lops = {
>  #endif
>  };
>  
> -static int ids_cmp_r(const void *pa, const void *pb, const void *priv __maybe_unused)
> +struct tracing_multi_sort_data {
> +	u64 *keys;
> +	struct bpf_prog **progs;
> +	u32 *ids;
> +	u64 *cookies;
> +};
> +
> +static int keys_cmp_r(const void *pa, const void *pb, const void *priv __maybe_unused)
>  {
> -	u32 a = *(u32 *) pa;
> -	u32 b = *(u32 *) pb;

I think you could just s/32/64/ and keep the rest in here and have simpler diff

> +	const u64 *key_a = pa, *key_b = pb;
>  
> -	return (a > b) - (a < b);
> +	return (*key_a > *key_b) - (*key_a < *key_b);
>  }
>  
> -static void ids_swap_r(void *a, void *b, int size __maybe_unused,
> -		       const void *priv __maybe_unused)
> +static void keys_swap_r(void *a, void *b, int size __maybe_unused,
> +			const void *priv __maybe_unused)
>  {
> +	const struct tracing_multi_sort_data *data = priv;
> +	struct bpf_prog **prog_a, **prog_b;
>  	u64 *cookie_a, *cookie_b, *cookies;
> -	u32 *id_a = a, *id_b = b, *ids;
> -	void **data = (void **) priv;
> +	u64 *key_a = a, *key_b = b, *keys;
> +	u32 *id_a, *id_b, *ids;
> +
> +	keys    = data->keys;
> +	ids     = data->ids;
> +	cookies = data->cookies;
> +	id_a    = ids + (key_a - keys);
> +	id_b    = ids + (key_b - keys);
>  
> -	ids     = data[0];
> -	cookies = data[1];
> +	if (data->progs) {

nit, let's unify with the rest of the code and have progs variable for data->progs ?

SNIP

> -	err = check_dup_ids(ids, cookies, cnt);
> +	keys = kvmalloc_objs(*keys, cnt);
> +	if (!keys) {
> +		err = -ENOMEM;
> +		goto error;
> +	}
> +
> +	for (int i = 0; i < cnt; i++)
> +		keys[i] = bpf_trampoline_compute_key(progs ? progs[i] : NULL, btf, ids[i]);
> +
> +	err = check_dup_keys(keys, progs, ids, cookies, cnt);
>  	if (err)
>  		goto error;
>  
> @@ -3908,19 +4022,32 @@ int bpf_tracing_multi_attach(struct bpf_prog *prog, const union bpf_attr *attr)
>  	link->nodes_cnt = cnt;
>  	link->cookies = cookies;
>  	link->fexits = fexits;
> +	link->tgt_progs = progs;
> +	link->pokes = pokes;
>  
> -	err = bpf_trampoline_multi_attach(prog, ids, link);
> +	if (progs)
> +		err = bpf_trampoline_multi_prog_attach(prog, ids, keys, link);

you need keys computed ahead for dups check, so let's the above
bpf_trampoline_compute_key calls be the single place we compute keys
and pass keys to bpf_trampoline_multi_attach below as well?

> +	else
> +		err = bpf_trampoline_multi_attach(prog, ids, link);

nit, let's add empty line in here?

>  	kvfree(ids);
> +	kvfree(keys);
> +	kvfree(fds);
>  	if (err) {
> +		bpf_put_progs(progs, cnt);
>  		bpf_link_cleanup(&link_primer);
>  		return err;
>  	}
>  	return bpf_link_settle(&link_primer);

thanks,
jirka