[RFC bpf-next 7/8] bpf: migrate insn remove to list patching infra

[Jiong Wang]

This patch migrate dead code remove pass to new list patching
infrastructure.

Signed-off-by: Jiong Wang <jiong.w...@netronome.com>
---
 kernel/bpf/verifier.c | 59 +++++++++++++++++----------------------------------
 1 file changed, 19 insertions(+), 40 deletions(-)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 58d6bbe..abe11fd 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -8500,49 +8500,30 @@ verifier_linearize_list_insn(struct bpf_verifier_env 
*env,
        return ret_env;
 }
 
-static int opt_remove_dead_code(struct bpf_verifier_env *env)
+static int opt_remove_useless_code(struct bpf_verifier_env *env)
 {
-       struct bpf_insn_aux_data *aux_data = env->insn_aux_data;
-       int insn_cnt = env->prog->len;
-       int i, err;
-
-       for (i = 0; i < insn_cnt; i++) {
-               int j;
-
-               j = 0;
-               while (i + j < insn_cnt && !aux_data[i + j].seen)
-                       j++;
-               if (!j)
-                       continue;
-
-               err = verifier_remove_insns(env, i, j);
-               if (err)
-                       return err;
-               insn_cnt = env->prog->len;
-       }
-
-       return 0;
-}
-
-static int opt_remove_nops(struct bpf_verifier_env *env)
-{
-       const struct bpf_insn ja = BPF_JMP_IMM(BPF_JA, 0, 0, 0);
-       struct bpf_insn *insn = env->prog->insnsi;
-       int insn_cnt = env->prog->len;
-       int i, err;
+       struct bpf_insn_aux_data *auxs = env->insn_aux_data;
+       const struct bpf_insn nop =
+               BPF_JMP_IMM(BPF_JA, 0, 0, 0);
+       struct bpf_list_insn *list, *elem;
+       int ret = 0;
 
-       for (i = 0; i < insn_cnt; i++) {
-               if (memcmp(&insn[i], &ja, sizeof(ja)))
+       list = bpf_create_list_insn(env->prog);
+       if (IS_ERR(list))
+               return PTR_ERR(list);
+       for (elem = list; elem; elem = elem->next) {
+               if (auxs[elem->orig_idx - 1].seen &&
+                   memcmp(&elem->insn, &nop, sizeof(nop)))
                        continue;
 
-               err = verifier_remove_insns(env, i, 1);
-               if (err)
-                       return err;
-               insn_cnt--;
-               i--;
+               elem->flag |= LIST_INSN_FLAG_REMOVED;
        }
 
-       return 0;
+       env = verifier_linearize_list_insn(env, list);
+       if (IS_ERR(env))
+               ret = PTR_ERR(env);
+       bpf_destroy_list_insn(list);
+       return ret;
 }
 
 static int opt_subreg_zext_lo32_rnd_hi32(struct bpf_verifier_env *env,
@@ -9488,9 +9469,7 @@ int bpf_check(struct bpf_prog **prog, union bpf_attr 
*attr,
                if (ret == 0)
                        opt_hard_wire_dead_code_branches(env);
                if (ret == 0)
-                       ret = opt_remove_dead_code(env);
-               if (ret == 0)
-                       ret = opt_remove_nops(env);
+                       ret = opt_remove_useless_code(env);
        } else {
                if (ret == 0)
                        sanitize_dead_code(env);
-- 
2.7.4