Re: [PATCH bpf-next v4 00/13] bpf: implement bpf iterator for map elements

On Thu, Jul 23, 2020 at 11:41:08AM -0700, Yonghong Song wrote:

Bpf iterator has been implemented for task, task_file,
bpf_map, ipv6_route, netlink, tcp and udp so far.

For map elements, there are two ways to traverse all elements from
user space:
  1. using BPF_MAP_GET_NEXT_KEY bpf subcommand to get elements
     one by one.
  2. using BPF_MAP_LOOKUP_BATCH bpf subcommand to get a batch of
     elements.
Both these approaches need to copy data from kernel to user space
in order to do inspection.

This patch implements bpf iterator for map elements.
User can have a bpf program in kernel to run with each map element,
do checking, filtering, aggregation, modifying values etc.
without copying data to user space.

Patch #1 and #2 are refactoring. Patch #3 implements readonly/readwrite
buffer support in verifier. Patches #4 - #7 implements map element
support for hash, percpu hash, lru hash lru percpu hash, array,
percpu array and sock local storage maps. Patches #8 - #9 are libbpf
and bpftool support. Patches #10 - #13 are selftests for implemented
map element iterators.

Changelogs:
  v3 -> v4:
    . fix a kasan failure triggered by a failed bpf_iter link_create,
      not just free_link but need cleanup_link. (Alexei)

Applied, Thanks