[PATCH bpf-next v5 2/6] bpf/verifier: add bpf_timer as a kfunc capable type

[Benjamin Tissoires]

We need to extend the bpf_timer API, but the way forward relies on kfuncs.
So make bpf_timer known for kfuncs from the verifier PoV

Signed-off-by: Benjamin Tissoires <bent...@kernel.org>

---

changes in v5:
- also check for the reg offset

changes in v4:
- enforce KF_ARG_PTR_TO_TIMER to be of type PTR_TO_MAP_VALUE

new in v3 (split from v2 02/10)
---
 kernel/bpf/verifier.c | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 63749ad5ac6b..24a604e26ec7 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -10826,6 +10826,7 @@ enum {
        KF_ARG_LIST_NODE_ID,
        KF_ARG_RB_ROOT_ID,
        KF_ARG_RB_NODE_ID,
+       KF_ARG_TIMER_ID,
 };
 
 BTF_ID_LIST(kf_arg_btf_ids)
@@ -10834,6 +10835,7 @@ BTF_ID(struct, bpf_list_head)
 BTF_ID(struct, bpf_list_node)
 BTF_ID(struct, bpf_rb_root)
 BTF_ID(struct, bpf_rb_node)
+BTF_ID(struct, bpf_timer_kern)
 
 static bool __is_kfunc_ptr_arg_type(const struct btf *btf,
                                    const struct btf_param *arg, int type)
@@ -10877,6 +10879,12 @@ 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)
+{
+       bool ret = __is_kfunc_ptr_arg_type(btf, arg, KF_ARG_TIMER_ID);
+       return ret;
+}
+
 static bool is_kfunc_arg_callback(struct bpf_verifier_env *env, const struct 
btf *btf,
                                  const struct btf_param *arg)
 {
@@ -10946,6 +10954,7 @@ 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,
 };
 
 enum special_kfunc_type {
@@ -11102,6 +11111,9 @@ get_kfunc_ptr_arg_type(struct bpf_verifier_env *env,
        if (is_kfunc_arg_map(meta->btf, &args[argno]))
                return KF_ARG_PTR_TO_MAP;
 
+       if (is_kfunc_arg_timer(meta->btf, &args[argno]))
+               return KF_ARG_PTR_TO_TIMER;
+
        if ((base_type(reg->type) == PTR_TO_BTF_ID || 
reg2btf_ids[base_type(reg->type)])) {
                if (!btf_type_is_struct(ref_t)) {
                        verbose(env, "kernel function %s args#%d pointer type 
%s %s is not supported\n",
@@ -11735,6 +11747,7 @@ static int check_kfunc_args(struct bpf_verifier_env 
*env, struct bpf_kfunc_call_
                case KF_ARG_PTR_TO_CALLBACK:
                case KF_ARG_PTR_TO_REFCOUNTED_KPTR:
                case KF_ARG_PTR_TO_CONST_STR:
+               case KF_ARG_PTR_TO_TIMER:
                        /* Trusted by default */
                        break;
                default:
@@ -12021,6 +12034,16 @@ static int check_kfunc_args(struct bpf_verifier_env 
*env, struct bpf_kfunc_call_
                        if (ret)
                                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;
+                       }
+                       if (reg->off) {
+                               verbose(env, "arg#%d offset can not be greater 
than 0\n", i);
+                               return -EINVAL;
+                       }
+                       break;
                }
        }
 

-- 
2.44.0