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>

include/linux/bpf_verifier.h

@@ -173,6 +173,11 @@ static inline bool bpf_verifier_log_needed(const struct bpf_verifier_log *log)
 
 #define BPF_MAX_SUBPROGS 256
 
+struct bpf_subprog_info {
+	u32 start; /* insn idx of function entry point */
+	u16 stack_depth; /* max. stack depth used by this function */
+};
+
 /* single container for all structs
  * one verifier_env per bpf_check() call
  */
@@ -191,9 +196,7 @@ struct bpf_verifier_env {
 	bool seen_direct_write;
 	struct bpf_insn_aux_data *insn_aux_data; /* array of per-insn state */
 	struct bpf_verifier_log log;
-	u32 subprog_starts[BPF_MAX_SUBPROGS];
-	/* computes the stack depth of each bpf function */
-	u16 subprog_stack_depth[BPF_MAX_SUBPROGS + 1];
+	struct bpf_subprog_info subprog_info[BPF_MAX_SUBPROGS + 1];
 	u32 subprog_cnt;
 };