Re: [PATCH v4 bpf-next 3/4] bpf: Add kernel module with user mode driver that populates bpffs.

On 7/24/20 10:38 PM, Alexei Starovoitov wrote:

From: Alexei Starovoitov <ast@kernel.org>

Add kernel module with user mode driver that populates bpffs with
BPF iterators.

$ mount bpffs /my/bpffs/ -t bpf
$ ls -la /my/bpffs/
total 4
drwxrwxrwt  2 root root    0 Jul  2 00:27 .
drwxr-xr-x 19 root root 4096 Jul  2 00:09 ..
-rw-------  1 root root    0 Jul  2 00:27 maps.debug
-rw-------  1 root root    0 Jul  2 00:27 progs.debug

The user mode driver will load BPF Type Formats, create BPF maps, populate BPF
maps, load two BPF programs, attach them to BPF iterators, and finally send two
bpf_link IDs back to the kernel.
The kernel will pin two bpf_links into newly mounted bpffs instance under
names "progs.debug" and "maps.debug". These two files become human readable.

$ cat /my/bpffs/progs.debug
   id name            attached
   11 dump_bpf_map    bpf_iter_bpf_map
   12 dump_bpf_prog   bpf_iter_bpf_prog
   27 test_pkt_access
   32 test_main       test_pkt_access test_pkt_access
   33 test_subprog1   test_pkt_access_subprog1 test_pkt_access
   34 test_subprog2   test_pkt_access_subprog2 test_pkt_access
   35 test_subprog3   test_pkt_access_subprog3 test_pkt_access
   36 new_get_skb_len get_skb_len test_pkt_access
   37 new_get_skb_ifindex get_skb_ifindex test_pkt_access
   38 new_get_constant get_constant test_pkt_access

The BPF program dump_bpf_prog() in iterators.bpf.c is printing this data about
all BPF programs currently loaded in the system. This information is unstable
and will change from kernel to kernel as ".debug" suffix conveys.

Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Looks like this needs one last respin, but either way the module handling looks much
cleaner now, Ack.

Thanks,
Daniel