Merge branch 'bpf-subprog-mgmt-cleanup'

Merge branch 'bpf-subprog-mgmt-cleanup'

Jiong Wang says:

====================
This patch set clean up some code logic related with managing subprog
information.

Part of the set are inspried by Edwin's code in his RFC:

  "bpf/verifier: subprog/func_call simplifications"

but with clearer separation so it could be easier to review.

  - Path 1 unifies main prog and subprogs. All of them are registered in
    env->subprog_starts.

  - After patch 1, it is clear that subprog_starts and subprog_stack_depth
    could be merged as both of them now have main and subprog unified.
    Patch 2 therefore does the merge, all subprog information are centred
    at bpf_subprog_info.

  - Patch 3 goes further to introduce a new fake "exit" subprog which
    serves as an ending marker to the subprog list. We could then turn the
    following code snippets across verifier:

       if (env->subprog_cnt == cur_subprog + 1)
               subprog_end = insn_cnt;
       else
               subprog_end = env->subprog_info[cur_subprog + 1].start;

    into:
       subprog_end = env->subprog_info[cur_subprog + 1].start;

There is no functional change by this patch set.
No bpf selftest (both non-jit and jit) regression found after this set.

v2:
  - fixed adjust_subprog_starts to also update fake "exit" subprog start.
  - for John's suggestion on renaming subprog to prog, I could work on
    a follow-up patch if it is recognized as worth the change.
====================

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>