[PATCH v2 bpf-next 06/13] bpf: Add bpf_rbtree_{add,remove,first} kfuncs

Dave Marchevsky
2022-12-17T08:25:42Z

This patch adds implementations of bpf_rbtree_{add,remove,first}
and teaches verifier about their BTF_IDs as well as those of
bpf_rb_{root,node}.

All three kfuncs have some nonstandard component to their verification
that needs to be addressed in future patches before programs can
properly use them:

* bpf_rbtree_add: Takes 'less' callback, need to verify it

* bpf_rbtree_first: Returns ptr_to_node_type(off=rb_node_off) instead
of ptr_to_rb_node(off=0). Return value ref is
non-owning.

* bpf_rbtree_remove: Returns ptr_to_node_type(off=rb_node_off) instead
of ptr_to_rb_node(off=0). 2nd arg (node) is a
non-owning reference.

Signed-off-by: Dave Marchevsky <davemarchevsky@fb.com>
---
kernel/bpf/helpers.c | 28 ++++++++++++++++++++++++++++
kernel/bpf/verifier.c | 11 +++++++++++
2 files changed, 39 insertions(+)

diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index 30fff015f9a1..de4523c777b7 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -1873,6 +1873,30 @@ struct bpf_list_node *bpf_list_pop_back(struct bpf_list_head *head)
return __bpf_list_del(head, true);
}

+struct bpf_rb_node *bpf_rbtree_remove(struct bpf_rb_root *root, struct bpf_rb_node *node)
+{
+ struct rb_root_cached *r = (struct rb_root_cached *)root;
+ struct rb_node *n = (struct rb_node *)node;
+
+ rb_erase_cached(n, r);
+ RB_CLEAR_NODE(n);
+ return (struct bpf_rb_node *)n;
+}
+
+void bpf_rbtree_add(struct bpf_rb_root *root, struct bpf_rb_node *node,
+ bool (less)(struct bpf_rb_node *a, const struct bpf_rb_node *b))
+{
+ rb_add_cached((struct rb_node *)node, (struct rb_root_cached *)root,
+ (bool (*)(struct rb_node *, const struct rb_node *))less);
+}
+
+struct bpf_rb_node *bpf_rbtree_first(struct bpf_rb_root *root)
+{
+ struct rb_root_cached *r = (struct rb_root_cached *)root;
+
+ return (struct bpf_rb_node *)rb_first_cached(r);
+}
+
/**
* bpf_task_acquire - Acquire a reference to a task. A task acquired by this
* kfunc which is not stored in a map as a kptr, must be released by calling
@@ -2097,6 +2121,10 @@ BTF_ID_FLAGS(func, bpf_task_acquire, KF_ACQUIRE | KF_TRUSTED_ARGS)
BTF_ID_FLAGS(func, bpf_task_acquire_not_zero, KF_ACQUIRE | KF_RCU | KF_RET_NULL)
BTF_ID_FLAGS(func, bpf_task_kptr_get, KF_ACQUIRE | KF_KPTR_GET | KF_RET_NULL)
BTF_ID_FLAGS(func, bpf_task_release, KF_RELEASE)
+BTF_ID_FLAGS(func, bpf_rbtree_remove, KF_ACQUIRE)
+BTF_ID_FLAGS(func, bpf_rbtree_add, KF_RELEASE | KF_RELEASE_NON_OWN)
+BTF_ID_FLAGS(func, bpf_rbtree_first, KF_RET_NULL)
+
#ifdef CONFIG_CGROUPS
BTF_ID_FLAGS(func, bpf_cgroup_acquire, KF_ACQUIRE | KF_TRUSTED_ARGS)
BTF_ID_FLAGS(func, bpf_cgroup_kptr_get, KF_ACQUIRE | KF_KPTR_GET | KF_RET_NULL)
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 89d8d754567b..e90cf0b74571 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -8406,6 +8406,8 @@ BTF_ID_LIST(kf_arg_btf_ids)
BTF_ID(struct, bpf_dynptr_kern)
BTF_ID(struct, bpf_list_head)
BTF_ID(struct, bpf_list_node)
+BTF_ID(struct, bpf_rb_root)
+BTF_ID(struct, bpf_rb_node)

static bool __is_kfunc_ptr_arg_type(const struct btf *btf,
const struct btf_param *arg, int type)
@@ -8511,6 +8513,9 @@ enum special_kfunc_type {
KF_bpf_rdonly_cast,
KF_bpf_rcu_read_lock,
KF_bpf_rcu_read_unlock,
+ KF_bpf_rbtree_remove,
+ KF_bpf_rbtree_add,
+ KF_bpf_rbtree_first,
};

BTF_SET_START(special_kfunc_set)
@@ -8522,6 +8527,9 @@ BTF_ID(func, bpf_list_pop_front)
BTF_ID(func, bpf_list_pop_back)
BTF_ID(func, bpf_cast_to_kern_ctx)
BTF_ID(func, bpf_rdonly_cast)
+BTF_ID(func, bpf_rbtree_remove)
+BTF_ID(func, bpf_rbtree_add)
+BTF_ID(func, bpf_rbtree_first)
BTF_SET_END(special_kfunc_set)

BTF_ID_LIST(special_kfunc_list)
@@ -8535,6 +8543,9 @@ BTF_ID(func, bpf_cast_to_kern_ctx)
BTF_ID(func, bpf_rdonly_cast)
BTF_ID(func, bpf_rcu_read_lock)
BTF_ID(func, bpf_rcu_read_unlock)
+BTF_ID(func, bpf_rbtree_remove)
+BTF_ID(func, bpf_rbtree_add)
+BTF_ID(func, bpf_rbtree_first)

static bool is_kfunc_bpf_rcu_read_lock(struct bpf_kfunc_call_arg_meta *meta)
{
--
2.30.2