Only output backtracking information in log level 2

Backtracking information is very verbose, don't print it in log
level 1 to improve readability.
Signed-off-by: Christy Lee <christylee@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20211216213358.3374427-4-christylee@fb.com

kernel/bpf/verifier.c

@@ -2398,7 +2398,7 @@ static int backtrack_insn(struct bpf_verifier_env *env, int idx,
 
 	if (insn->code == 0)
 		return 0;
-	if (env->log.level & BPF_LOG_LEVEL) {
+	if (env->log.level & BPF_LOG_LEVEL2) {
 		verbose(env, "regs=%x stack=%llx before ", *reg_mask, *stack_mask);
 		verbose(env, "%d: ", idx);
 		print_bpf_insn(&cbs, insn, env->allow_ptr_leaks);
@@ -2656,7 +2656,7 @@ static int __mark_chain_precision(struct bpf_verifier_env *env, int regno,
 		DECLARE_BITMAP(mask, 64);
 		u32 history = st->jmp_history_cnt;
 
-		if (env->log.level & BPF_LOG_LEVEL)
+		if (env->log.level & BPF_LOG_LEVEL2)
 			verbose(env, "last_idx %d first_idx %d\n", last_idx, first_idx);
 		for (i = last_idx;;) {
 			if (skip_first) {
@@ -2743,7 +2743,7 @@ static int __mark_chain_precision(struct bpf_verifier_env *env, int regno,
 				new_marks = true;
 			reg->precise = true;
 		}
-		if (env->log.level & BPF_LOG_LEVEL) {
+		if (env->log.level & BPF_LOG_LEVEL2) {
 			verbose(env, "parent %s regs=%x stack=%llx marks:",
 				new_marks ? "didn't have" : "already had",
 				reg_mask, stack_mask);