On Tue, Apr 26, 2022 at 2:45 PM Andrii Nakryiko
<andrii.nakryiko@xxxxxxxxx> wrote:
>
> On Sat, Apr 23, 2022 at 7:01 AM Yafang Shao <laoar.shao@xxxxxxxxx> wrote:
> >
> > Currently there're helpers for allowing to open/load/attach BPF object
> > through BPF object skeleton. Let's also add helpers for pinning through
> > BPF object skeleton. It could simplify BPF userspace code which wants to
> > pin the progs into bpffs.
> >
> > After this change, with command 'bpftool gen skeleton XXX.bpf.o', the
> > helpers for pinning BPF prog will be generated in BPF object skeleton.
> >
> > The new helpers are named with __{pin, unpin}_prog, because it only pins
> > bpf progs. If the user also wants to pin bpf maps, he can use
> > LIBBPF_PIN_BY_NAME.
>
> API says it's pinning programs, but really it's trying to pin links.
Actually it should be bpf_object__pin_skeleton_link().
> But those links might not even be created for non-auto-attachable
> programs, and for others users might or might not set
> <skel>.links.<prog_name> links.
>
> There are lots of questions about this new functionality... But the
> main one is why do we need it? What does it bring that's hard to do
> otherwise?
>
See also my replyment to Daniel[1].
For the FD-based bpf objects, the userspace code is similar, so we can
abstract the userspace code into a common code, and then the developer
doesn't need to write the userspace code any more (if he doesn't have
some special userspace logical.).
[1]. https://lore.kernel.org/bpf/CAEf4BzbhODOBrE=unLOUpo40uUYz72BJX-+uJobiwhF9VFSizQ@xxxxxxxxxxxxxx/T/#m32dfc6343f2b4fba980c62686b245cb6e0133c2f
> >
> > Yafang Shao (4):
> > libbpf: Define DEFAULT_BPFFS
> > libbpf: Add helpers for pinning bpf prog through bpf object skeleton
> > bpftool: Fix incorrect return in generated detach helper
> > bpftool: Generate helpers for pinning prog through bpf object skeleton
> >
> > tools/bpf/bpftool/gen.c | 18 ++++++++++-
> > tools/lib/bpf/bpf_helpers.h | 2 +-
> > tools/lib/bpf/libbpf.c | 61 ++++++++++++++++++++++++++++++++++++-
> > tools/lib/bpf/libbpf.h | 10 ++++--
> > tools/lib/bpf/libbpf.map | 2 ++
> > 5 files changed, 88 insertions(+), 5 deletions(-)
> >
> > --
> > 2.17.1
> >
--
Regards
Yafang
