Re: [PATCHv7 bpf-next 13/29] bpf: Add support for tracing multi link

[Jiri Olsa <olsajiri@gmail.com>]

On Wed, Jun 03, 2026 at 11:41:50AM +0000, sashiko-bot@kernel.org wrote:
> Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
> - [Low] The patch references multiple undefined symbols (`struct bpf_tracing_multi_link`, `bpf_trampoline_multi_attach`, `bpf_trampoline_multi_detach`, and `is_tracing_multi`), which results in compilation failures.
> --

this commit compiles fine, specific answers below

jirka

> 
> commit 4e3377b79034e4eafa802e1a2382a4ca893a956f
> Author: Jiri Olsa <jolsa@kernel.org>
> 
> bpf: Add support for tracing multi link
> 
> This commit adds a new link type to allow attaching a BPF program to
> multiple function BTF IDs. It introduces the tracing_multi configuration
> fields in bpf_attr::link_create and implements the attachment logic.
> 
> > diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
> > index 625a4366fe6d7..6f72ede0c8f04 100644
> > --- a/kernel/bpf/syscall.c
> > +++ b/kernel/bpf/syscall.c
> > @@ -5842,6 +5842,8 @@ 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))
> 
> [Severity: Low]
> Is is_tracing_multi() defined anywhere in this series? It appears this might
> cause an implicit declaration error during the build, as the function or macro
> seems to be missing.

yes, in: bpf: Add multi tracing attach types

> 
> > +			ret = bpf_tracing_multi_attach(prog, attr);
> >  		else
> >  			ret = bpf_tracing_prog_attach(prog,
> 
> [ ... ]
> 
> > diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
> > index d853f97bd154f..9e3cb547651e5 100644
> > --- a/kernel/trace/bpf_trace.c
> > +++ b/kernel/trace/bpf_trace.c
> > @@ -3641,3 +3642,132 @@ __bpf_kfunc int bpf_copy_from_user_task_str_dynptr(const struct bpf_dynptr *dptr
> >  }
> >  
> >  __bpf_kfunc_end_defs();
> > +
> > +#if defined(CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS) && \
> > +    defined(CONFIG_HAVE_SINGLE_FTRACE_DIRECT_OPS)
> > +
> > +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));
> 
> [Severity: Low]
> Where is bpf_trampoline_multi_detach() declared? It looks like the declaration
> and definition for this function are missing, which will break the build.

yes, in: bpf: Add bpf_trampoline_multi_attach/detach functions

> 
> > +}
> 
> [ ... ]
> 
> > +int bpf_tracing_multi_attach(struct bpf_prog *prog, const union bpf_attr *attr)
> > +{
> > +	struct bpf_tracing_multi_link *link = NULL;
> > +	struct bpf_link_primer link_primer;
> > +	u32 cnt, *ids = NULL;
> 
> [ ... ]
> 
> > +	err = check_dup_ids(ids, cnt);
> > +	if (err)
> > +		goto error;
> > +
> > +	link = kvzalloc_flex(*link, nodes, cnt);
> 
> [Severity: Low]
> Is struct bpf_tracing_multi_link defined anywhere? Evaluating the size of an
> incomplete type in this allocation macro will lead to a compiler error.

yes, in: bpf: Add bpf_trampoline_multi_attach/detach functions

> 
> > +	if (!link) {
> > +		err = -ENOMEM;
> > +		goto error;
> > +	}
> 
> [ ... ]
> 
> > +	link->nodes_cnt = cnt;
> > +
> > +	err = bpf_trampoline_multi_attach(prog, ids, link);
> 
> [Severity: Low]
> Does bpf_trampoline_multi_attach() exist yet? Like the detach function, this
> seems to be undeclared and undefined, leading to a build failure.

yes, in: bpf: Add bpf_trampoline_multi_attach/detach functions

> 
> > +	kvfree(ids);
> 
> -- 
> Sashiko AI review · https://sashiko.dev/#/patchset/20260603110554.29590-14-jolsa@kernel.org?part=1