Re: [PATCHv5 bpf-next 13/28] bpf: Add support for tracing multi link

[sashiko-bot@kernel.org]

Sashiko AI review found 1 potential issue(s):
- [Low] The patch references several undeclared identifiers and incomplete types, causing compilation failures.
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commit fc7697083b71bebef41d2da3a91ca2a0741ad6f0
Author: Jiri Olsa <jolsa@kernel.org>

bpf: Add support for tracing multi link

Adding a new link to allow attaching a BPF program to multiple function
BTF IDs, represented by struct bpf_tracing_multi_link.

> diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
> index a3c0214ca9341..da3e01dd7ee9a 100644
> --- a/kernel/bpf/syscall.c
> +++ b/kernel/bpf/syscall.c
[ ... ]
> @@ -5748,6 +5748,8 @@ static int link_create(union bpf_attr *attr, bpfptr_t uattr)
>  			ret = bpf_iter_link_attach(attr, uattr, prog);
>  		else if (prog->expected_attach_type == BPF_LSM_CGROUP)
>  			ret = cgroup_bpf_link_attach(attr, prog);
> +		else if (is_tracing_multi(prog->expected_attach_type))
> +			ret = bpf_tracing_multi_attach(prog, attr);

Is is_tracing_multi() defined anywhere? It doesn't appear to be declared
in this patch or the existing kernel tree, which could lead to a build
failure.

> diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
> index af7079aa0f36d..df06a733a2e71 100644
> --- a/kernel/trace/bpf_trace.c
> +++ b/kernel/trace/bpf_trace.c
[ ... ]
> +static void bpf_tracing_multi_link_release(struct bpf_link *link)
> +{
> +	struct bpf_tracing_multi_link *tr_link =
> +		container_of(link, struct bpf_tracing_multi_link, link);
> +
> +	WARN_ON_ONCE(bpf_trampoline_multi_detach(link->prog, tr_link));
> +}

Where is struct bpf_tracing_multi_link defined? It seems to be an
incomplete type here. 

Similarly, bpf_trampoline_multi_detach() doesn't appear to be declared in
this patch. Will this cause compilation errors when dereferencing or
calling these?

[ ... ]
> +	err = bpf_link_prime(&link->link, &link_primer);
> +	if (err)
> +		goto error;
> +
> +	link->nodes_cnt = cnt;
> +
> +	err = bpf_trampoline_multi_attach(prog, ids, link);

Does bpf_trampoline_multi_attach() also miss a declaration?

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Sashiko AI review · https://sashiko.dev/#/patchset/20260417192502.194548-14-jolsa@kernel.org?part=1