On Wed, May 29, 2024 at 12:38 AM Benjamin Tissoires bentiss@kernel.org wrote:
Take a look at include/linux/bpf_mprog.h I suspect it might be useful here too.
From the quick look of it this is interesting, but for plain struct bpf_prog, right?
So I would have to adapt this include for struct_ops?
yeah. It needs work to be adapted to work with struct-ops. I mentioned it mainly from uapi perspective. BPF_F_BEFORE, BPF_F_AFTER, BPF_F_REPLACE. Would be good to keep things consistent.
@@ -112,6 +113,63 @@ struct hid_ops {
extern struct hid_ops *hid_ops;
+/**
- struct hid_bpf_ops - A BPF struct_ops of callbacks allowing to attach HID-BPF
programs to a HID device
- @hid_id: the HID uniq ID to attach to. This is writeable before ``load()``, and
cannot be changed after
- @flags: &enum hid_bpf_attach_flags to assign flags before ``load()``.
Writeable only before ``load()``- */
+struct hid_bpf_ops {
/* hid_id needs to stay first so we can easily change it* from userspace.*/hmm. patch 5 just does:
skel->struct_ops.mouse_invert->hid_id = hid_id;I don't see a reason why it needs to be first.
See the selftests (and my external loader, udev-hid-bpf):
map = bpf_object__find_map_by_name(*self->skel->skeleton->obj, programs[i].name + 4); ASSERT_OK_PTR(map) TH_LOG("can not find struct_ops by name '%s'", programs[i].name + 4); /* hid_id is the first field of struct hid_bpf_ops */ ops_hid_id = bpf_map__initial_value(map, NULL); ASSERT_OK_PTR(ops_hid_id) TH_LOG("unable to retrieve struct_ops data"); *ops_hid_id = self->hid_id;Basically, I want to have to deal with .bpf.o and not the skeletons for the generic case. I want to be able to drop a file in /lib/firmware/hid and have udev-hid-bpf load it without having to recompile udev-hid-bpf.
and with additional restriction of only one struct-ops prog per elf file, right? Otherwise multiple hid_bpf_ops will be in the same elf section and the same map.
I couldn't seem to be able to access the struct_ops BTF information from libbpf, so I decided to have hid_id and flags first and consider this to be ABI while I figure out how to get to the real offsets :)
I see. I guess it's ok for now.