bpf: split explored_states

split explored_states into prune_point boolean mark
and link list of explored states.
This removes STATE_LIST_MARK hack and allows marks to be separate from states.

Signed-off-by: Alexei Starovoitov <[email protected]>
Signed-off-by: Daniel Borkmann <[email protected]>

Author: Alexei Starovoitov

include/linux/bpf_verifier.h

@@ -233,6 +233,7 @@ struct bpf_insn_aux_data {
 	int sanitize_stack_off; /* stack slot to be cleared */
 	bool seen; /* this insn was processed by the verifier */
 	u8 alu_state; /* used in combination with alu_limit */
+	bool prune_point;
 	unsigned int orig_idx; /* original instruction index */
 };
 

kernel/bpf/verifier.c

@@ -5436,7 +5436,6 @@ enum {
 	BRANCH = 2,
 };
 
-#define STATE_LIST_MARK ((struct bpf_verifier_state_list *) -1L)
 static struct bpf_verifier_state_list **explored_state(
 					struct bpf_verifier_env *env,
 					int idx)
@@ -5446,7 +5445,7 @@ static struct bpf_verifier_state_list **explored_state(
 
 static void init_explored_state(struct bpf_verifier_env *env, int idx)
 {
-	env->explored_states[idx] = STATE_LIST_MARK;
+	env->insn_aux_data[idx].prune_point = true;
 }
 
 /* t, w, e - match pseudo-code above:
@@ -6018,10 +6017,7 @@ static void clean_live_states(struct bpf_verifier_env *env, int insn,
 	int i;
 
 	sl = *explored_state(env, insn);
-	if (!sl)
-		return;
-
-	while (sl != STATE_LIST_MARK) {
+	while (sl) {
 		if (sl->state.curframe != cur->curframe)
 			goto next;
 		for (i = 0; i <= cur->curframe; i++)
@@ -6376,18 +6372,18 @@ static int is_state_visited(struct bpf_verifier_env *env, int insn_idx)
 	struct bpf_verifier_state *cur = env->cur_state, *new;
 	int i, j, err, states_cnt = 0;
 
-	pprev = explored_state(env, insn_idx);
-	sl = *pprev;
-
-	if (!sl)
+	if (!env->insn_aux_data[insn_idx].prune_point)
 		/* this 'insn_idx' instruction wasn't marked, so we will not
 		 * be doing state search here
 		 */
 		return 0;
 
+	pprev = explored_state(env, insn_idx);
+	sl = *pprev;
+
 	clean_live_states(env, insn_idx, cur);
 
-	while (sl != STATE_LIST_MARK) {
+	while (sl) {
 		if (states_equal(env, &sl->state, cur)) {
 			sl->hit_cnt++;
 			/* reached equivalent register/stack state,
@@ -8145,13 +8141,12 @@ static void free_states(struct bpf_verifier_env *env)
 	for (i = 0; i < env->prog->len; i++) {
 		sl = env->explored_states[i];
 
-		if (sl)
-			while (sl != STATE_LIST_MARK) {
-				sln = sl->next;
-				free_verifier_state(&sl->state, false);
-				kfree(sl);
-				sl = sln;
-			}
+		while (sl) {
+			sln = sl->next;
+			free_verifier_state(&sl->state, false);
+			kfree(sl);
+			sl = sln;
+		}
 	}
 
 	kvfree(env->explored_states);