bpf: Track verifier context diagnostic events

Record verifier context transitions in the diagnostic history so later reports
can anchor causal paths to the critical section that made an operation invalid.

This covers lock, IRQ, RCU, and preempt regions without adding any new
verifier error reports. Category-specific commits decide where those recorded
events should be rendered.

Use context depth when selecting scoped history so nested regions anchor at the
outer active region, and fall back to the earliest retained event when the
matching entry was pruned.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://patch.msgid.link/20260815064612.378577-8-memxor@gmail.com
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>

3 files changed, 74 insertions, 5 deletions

diff --git a/kernel/bpf/diagnostics.c b/kernel/bpf/diagnostics.c
index ddeaff1e90b7..15bca8a02a48 100644
--- a/kernel/bpf/diagnostics.c
+++ b/kernel/bpf/diagnostics.c
@@ -104,6 +104,7 @@ enum bpf_diag_history_kind {
 	BPF_DIAG_HISTORY_MOD,
 	BPF_DIAG_HISTORY_REF_ACQUIRE,
 	BPF_DIAG_HISTORY_REF_RELEASE,
+	BPF_DIAG_HISTORY_CONTEXT,
 };
 
 struct bpf_diag_history_event {
@@ -124,6 +125,11 @@ struct bpf_diag_history_event {
 		struct {
 			u32 ref_id;
 		} ref;
+		struct {
+			u32 depth;
+			u8 kind;
+			bool enter;
+		} ctx;
 	};
 };
 
@@ -388,6 +394,19 @@ void bpf_diag_event_log_restore(struct bpf_verifier_env *env, u64 log_pos)
 	log->cnt = log_pos - log->first_seq;
 }
 
+u32 bpf_diag_irq_depth(const struct bpf_verifier_state *state)
+{
+	u32 depth = 0;
+	int i;
+
+	for (i = 0; i < state->acquired_refs; i++) {
+		if (state->refs[i].type == REF_TYPE_IRQ)
+			depth++;
+	}
+
+	return depth;
+}
+
 static void diag_append_history(struct bpf_verifier_env *env,
 				const struct bpf_diag_history_event *event)
 {
@@ -1049,3 +1068,23 @@ void bpf_diag_record_ref_release(struct bpf_verifier_env *env, u32 insn_idx, u32
 {
 	diag_record_ref(env, insn_idx, BPF_DIAG_HISTORY_REF_RELEASE, ref_id);
 }
+
+void bpf_diag_record_context(struct bpf_verifier_env *env, u32 insn_idx,
+			     enum bpf_diag_context_kind ctx_kind, bool enter, u32 depth)
+{
+	/*
+	 * Keep leave events so context rendering can stop at a depth-zero exit
+	 * and show nested-region depth accurately for the active path.
+	 */
+	struct bpf_diag_history_event event = {
+		.insn_idx = insn_idx,
+		.kind = BPF_DIAG_HISTORY_CONTEXT,
+		.ctx = {
+			.kind = ctx_kind,
+			.enter = enter,
+			.depth = depth,
+		},
+	};
+
+	diag_append_history(env, &event);
+}
diff --git a/kernel/bpf/diagnostics.h b/kernel/bpf/diagnostics.h
index d17b498a3f66..ed64776736c6 100644
--- a/kernel/bpf/diagnostics.h
+++ b/kernel/bpf/diagnostics.h
@@ -11,6 +11,7 @@
 struct bpf_func_state;
 struct bpf_reg_state;
 struct bpf_verifier_env;
+struct bpf_verifier_state;
 struct btf;
 
 enum bpf_diag_mod_reason {
@@ -23,6 +24,14 @@ enum bpf_diag_mod_reason {
 	BPF_DIAG_MOD_CALLER_SAVED,
 };
 
+enum bpf_diag_context_kind {
+	BPF_DIAG_CONTEXT_NONE,
+	BPF_DIAG_CONTEXT_RCU,
+	BPF_DIAG_CONTEXT_PREEMPT,
+	BPF_DIAG_CONTEXT_IRQ,
+	BPF_DIAG_CONTEXT_LOCK,
+};
+
 bool bpf_diag_enabled(const struct bpf_verifier_env *env);
 int bpf_diag_init(struct bpf_verifier_env *env);
 void bpf_diag_init_frame(struct bpf_verifier_env *env, struct bpf_func_state *state);
@@ -33,6 +42,7 @@ const char *bpf_diag_fmt(struct bpf_verifier_env *env, const char *fmt, ...) __p
 const char *bpf_diag_fmt_btf_type(struct bpf_verifier_env *env, const struct btf *btf, u32 type_id);
 u64 bpf_diag_event_log_save(struct bpf_verifier_env *env);
 void bpf_diag_event_log_restore(struct bpf_verifier_env *env, u64 log_pos);
+u32 bpf_diag_irq_depth(const struct bpf_verifier_state *state);
 void bpf_diag_free(struct bpf_verifier_env *env);
 void bpf_diag_record_branch(struct bpf_verifier_env *env, u32 insn_idx, bool cond_true);
 void bpf_diag_mod_begin(struct bpf_verifier_env *env, const struct bpf_reg_state *reg,
@@ -45,5 +55,7 @@ void bpf_diag_record_scrub_stack(struct bpf_verifier_env *env,
 				 enum bpf_diag_mod_reason reason);
 void bpf_diag_record_ref_acquire(struct bpf_verifier_env *env, u32 insn_idx, u32 ref_id);
 void bpf_diag_record_ref_release(struct bpf_verifier_env *env, u32 insn_idx, u32 ref_id);
+void bpf_diag_record_context(struct bpf_verifier_env *env, u32 insn_idx,
+			     enum bpf_diag_context_kind ctx_kind, bool enter, u32 depth);
 
 #endif /* __BPF_DIAGNOSTICS_H */
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 8e32fa5fa30a..1f2a7f480ce3 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -1045,7 +1045,7 @@ static int is_iter_reg_valid_init(struct bpf_verifier_env *env, struct bpf_reg_s
 }
 
 static int acquire_irq_state(struct bpf_verifier_env *env, int insn_idx);
-static int release_irq_state(struct bpf_verifier_state *state, int id);
+static int release_irq_state(struct bpf_verifier_env *env, int id);
 
 static int mark_stack_slot_irq_flag(struct bpf_verifier_env *env,
 				     struct bpf_call_arg_meta *meta,
@@ -1104,7 +1104,7 @@ static int unmark_stack_slot_irq_flag(struct bpf_verifier_env *env, struct bpf_r
 		return -EINVAL;
 	}
 
-	err = release_irq_state(env->cur_state, st->id);
+	err = release_irq_state(env, st->id);
 	WARN_ON_ONCE(err && err != -EACCES);
 	if (err) {
 		int insn_idx = 0;
@@ -1439,6 +1439,8 @@ static int acquire_lock_state(struct bpf_verifier_env *env, int insn_idx, enum r
 	state->active_locks++;
 	state->active_lock_id = id;
 	state->active_lock_ptr = ptr;
+	bpf_diag_record_context(env, insn_idx, BPF_DIAG_CONTEXT_LOCK, true,
+				state->active_locks);
 	return 0;
 }
 
@@ -1454,6 +1456,8 @@ static int acquire_irq_state(struct bpf_verifier_env *env, int insn_idx)
 	s->id = ++env->id_gen;
 
 	state->active_irq_id = s->id;
+	bpf_diag_record_context(env, insn_idx, BPF_DIAG_CONTEXT_IRQ, true,
+				bpf_diag_irq_depth(state));
 	return s->id;
 }
 
@@ -1495,8 +1499,9 @@ static bool reg_is_referenced(struct bpf_verifier_env *env, const struct bpf_reg
 	return find_reference_state(env->cur_state, reg->id);
 }
 
-static int release_lock_state(struct bpf_verifier_state *state, int type, int id, void *ptr)
+static int release_lock_state(struct bpf_verifier_env *env, int type, int id, void *ptr)
 {
+	struct bpf_verifier_state *state = env->cur_state;
 	void *prev_ptr = NULL;
 	u32 prev_id = 0;
 	int i;
@@ -1509,6 +1514,8 @@ static int release_lock_state(struct bpf_verifier_state *state, int type, int id
 			/* Reassign active lock (id, ptr). */
 			state->active_lock_id = prev_id;
 			state->active_lock_ptr = prev_ptr;
+			bpf_diag_record_context(env, env->insn_idx, BPF_DIAG_CONTEXT_LOCK,
+						false, state->active_locks);
 			return 0;
 		}
 		if (state->refs[i].type & REF_TYPE_LOCK_MASK) {
@@ -1519,8 +1526,9 @@ static int release_lock_state(struct bpf_verifier_state *state, int type, int id
 	return -EINVAL;
 }
 
-static int release_irq_state(struct bpf_verifier_state *state, int id)
+static int release_irq_state(struct bpf_verifier_env *env, int id)
 {
+	struct bpf_verifier_state *state = env->cur_state;
 	u32 prev_id = 0;
 	int i;
 
@@ -1533,6 +1541,8 @@ static int release_irq_state(struct bpf_verifier_state *state, int id)
 		if (state->refs[i].id == id) {
 			release_reference_state(state, i);
 			state->active_irq_id = prev_id;
+			bpf_diag_record_context(env, env->insn_idx, BPF_DIAG_CONTEXT_IRQ,
+						false, bpf_diag_irq_depth(state));
 			return 0;
 		} else {
 			prev_id = state->refs[i].id;
@@ -7181,7 +7191,7 @@ static int process_spin_lock(struct bpf_verifier_env *env, struct bpf_reg_state
 			verbose(env, "%s_unlock cannot be out of order\n", lock_str);
 			return -EINVAL;
 		}
-		if (release_lock_state(cur, type, reg->id, ptr)) {
+		if (release_lock_state(env, type, reg->id, ptr)) {
 			verbose(env, "%s_unlock of different lock\n", lock_str);
 			return -EINVAL;
 		}
@@ -13242,22 +13252,30 @@ static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
 
 	if (rcu_lock) {
 		env->cur_state->active_rcu_locks++;
+		bpf_diag_record_context(env, insn_idx, BPF_DIAG_CONTEXT_RCU, true,
+					env->cur_state->active_rcu_locks);
 	} else if (rcu_unlock) {
 		if (env->cur_state->active_rcu_locks == 0) {
 			verbose(env, "unmatched rcu read unlock (kernel function %s)\n", func_name);
 			return -EINVAL;
 		}
 		env->cur_state->active_rcu_locks--;
+		bpf_diag_record_context(env, insn_idx, BPF_DIAG_CONTEXT_RCU, false,
+					env->cur_state->active_rcu_locks);
 		if (!in_rcu_cs(env))
 			invalidate_rcu_protected_refs(env);
 	} else if (preempt_disable) {
 		env->cur_state->active_preempt_locks++;
+		bpf_diag_record_context(env, insn_idx, BPF_DIAG_CONTEXT_PREEMPT, true,
+					env->cur_state->active_preempt_locks);
 	} else if (preempt_enable) {
 		if (env->cur_state->active_preempt_locks == 0) {
 			verbose(env, "unmatched attempt to enable preemption (kernel function %s)\n", func_name);
 			return -EINVAL;
 		}
 		env->cur_state->active_preempt_locks--;
+		bpf_diag_record_context(env, insn_idx, BPF_DIAG_CONTEXT_PREEMPT, false,
+					env->cur_state->active_preempt_locks);
 		if (!in_rcu_cs(env))
 			invalidate_rcu_protected_refs(env);
 	}