[PATCH bpf-next v6 06/10] bpf: Add verifier support for bpf_timer argument in kfuncs

[Mykyta Yatsenko <mykyta.yatsenko5@gmail.com>]

From: Mykyta Yatsenko <yatsenko@meta.com>

Extend the verifier to recognize struct bpf_timer as a valid kfunc
argument type. Previously, bpf_timer was only supported in BPF helpers.

This prepares for adding timer-related kfuncs in subsequent patches.

Signed-off-by: Mykyta Yatsenko <yatsenko@meta.com>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
---
 kernel/bpf/verifier.c | 59 +++++++++++++++++++++++++++++++++++++++++++++------
 1 file changed, 53 insertions(+), 6 deletions(-)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 9de0ec0c3ed998b0b135d85d64fe07ee0f8df6d5..ae189a6af1dbcbf2da30f70dd9b848c4f90bb5cf 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -8566,17 +8566,15 @@ static int check_map_field_pointer(struct bpf_verifier_env *env, u32 regno,
 }
 
 static int process_timer_func(struct bpf_verifier_env *env, int regno,
-			      struct bpf_call_arg_meta *meta)
+			      struct bpf_map *map)
 {
-	struct bpf_reg_state *reg = reg_state(env, regno);
-	struct bpf_map *map = reg->map_ptr;
 	int err;
 
 	err = check_map_field_pointer(env, regno, BPF_TIMER);
 	if (err)
 		return err;
 
-	if (meta->map_ptr) {
+	if (map) {
 		verifier_bug(env, "Two map pointers in a timer helper");
 		return -EFAULT;
 	}
@@ -8584,8 +8582,36 @@ static int process_timer_func(struct bpf_verifier_env *env, int regno,
 		verbose(env, "bpf_timer cannot be used for PREEMPT_RT.\n");
 		return -EOPNOTSUPP;
 	}
+	return 0;
+}
+
+static int process_timer_helper(struct bpf_verifier_env *env, int regno,
+				struct bpf_call_arg_meta *meta)
+{
+	struct bpf_reg_state *reg = reg_state(env, regno);
+	int err;
+
+	err = process_timer_func(env, regno, meta->map_ptr);
+	if (err)
+		return err;
+
 	meta->map_uid = reg->map_uid;
-	meta->map_ptr = map;
+	meta->map_ptr = reg->map_ptr;
+	return 0;
+}
+
+static int process_timer_kfunc(struct bpf_verifier_env *env, int regno,
+			       struct bpf_kfunc_call_arg_meta *meta)
+{
+	struct bpf_reg_state *reg = reg_state(env, regno);
+	int err;
+
+	err = process_timer_func(env, regno, meta->map.ptr);
+	if (err)
+		return err;
+
+	meta->map.uid = reg->map_uid;
+	meta->map.ptr = reg->map_ptr;
 	return 0;
 }
 
@@ -9913,7 +9939,7 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 arg,
 		}
 		break;
 	case ARG_PTR_TO_TIMER:
-		err = process_timer_func(env, regno, meta);
+		err = process_timer_helper(env, regno, meta);
 		if (err)
 			return err;
 		break;
@@ -12166,6 +12192,7 @@ enum {
 	KF_ARG_WORKQUEUE_ID,
 	KF_ARG_RES_SPIN_LOCK_ID,
 	KF_ARG_TASK_WORK_ID,
+	KF_ARG_TIMER_ID,
 };
 
 BTF_ID_LIST(kf_arg_btf_ids)
@@ -12177,6 +12204,7 @@ BTF_ID(struct, bpf_rb_node)
 BTF_ID(struct, bpf_wq)
 BTF_ID(struct, bpf_res_spin_lock)
 BTF_ID(struct, bpf_task_work)
+BTF_ID(struct, bpf_timer)
 
 static bool __is_kfunc_ptr_arg_type(const struct btf *btf,
 				    const struct btf_param *arg, int type)
@@ -12220,6 +12248,11 @@ static bool is_kfunc_arg_rbtree_node(const struct btf *btf, const struct btf_par
 	return __is_kfunc_ptr_arg_type(btf, arg, KF_ARG_RB_NODE_ID);
 }
 
+static bool is_kfunc_arg_timer(const struct btf *btf, const struct btf_param *arg)
+{
+	return __is_kfunc_ptr_arg_type(btf, arg, KF_ARG_TIMER_ID);
+}
+
 static bool is_kfunc_arg_wq(const struct btf *btf, const struct btf_param *arg)
 {
 	return __is_kfunc_ptr_arg_type(btf, arg, KF_ARG_WORKQUEUE_ID);
@@ -12314,6 +12347,7 @@ enum kfunc_ptr_arg_type {
 	KF_ARG_PTR_TO_NULL,
 	KF_ARG_PTR_TO_CONST_STR,
 	KF_ARG_PTR_TO_MAP,
+	KF_ARG_PTR_TO_TIMER,
 	KF_ARG_PTR_TO_WORKQUEUE,
 	KF_ARG_PTR_TO_IRQ_FLAG,
 	KF_ARG_PTR_TO_RES_SPIN_LOCK,
@@ -12559,6 +12593,9 @@ get_kfunc_ptr_arg_type(struct bpf_verifier_env *env,
 	if (is_kfunc_arg_wq(meta->btf, &args[argno]))
 		return KF_ARG_PTR_TO_WORKQUEUE;
 
+	if (is_kfunc_arg_timer(meta->btf, &args[argno]))
+		return KF_ARG_PTR_TO_TIMER;
+
 	if (is_kfunc_arg_task_work(meta->btf, &args[argno]))
 		return KF_ARG_PTR_TO_TASK_WORK;
 
@@ -13345,6 +13382,7 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_
 		case KF_ARG_PTR_TO_REFCOUNTED_KPTR:
 		case KF_ARG_PTR_TO_CONST_STR:
 		case KF_ARG_PTR_TO_WORKQUEUE:
+		case KF_ARG_PTR_TO_TIMER:
 		case KF_ARG_PTR_TO_TASK_WORK:
 		case KF_ARG_PTR_TO_IRQ_FLAG:
 		case KF_ARG_PTR_TO_RES_SPIN_LOCK:
@@ -13644,6 +13682,15 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_
 			if (ret < 0)
 				return ret;
 			break;
+		case KF_ARG_PTR_TO_TIMER:
+			if (reg->type != PTR_TO_MAP_VALUE) {
+				verbose(env, "arg#%d doesn't point to a map value\n", i);
+				return -EINVAL;
+			}
+			ret = process_timer_kfunc(env, regno, meta);
+			if (ret < 0)
+				return ret;
+			break;
 		case KF_ARG_PTR_TO_TASK_WORK:
 			if (reg->type != PTR_TO_MAP_VALUE) {
 				verbose(env, "arg#%d doesn't point to a map value\n", i);

-- 
2.52.0