From: Martin KaFai Lau <martin.lau@xxxxxxxxxx>
In the kernel fq qdisc implementation, it only needs to look at
the fields of the first node in a list but does not always
need to remove it from the list. It is more convenient to have
a peek kfunc for the list. It works similar to the bpf_rbtree_first().
This patch adds bpf_list_{front,back} kfunc. The verifier is changed
such that the kfunc returning "struct bpf_list_node *" will be
marked as non-owning. The exception is the KF_ACQUIRE kfunc. The
net effect is only the new bpf_list_{front,back} kfuncs will
have its return pointer marked as non-owning.
Acked-by: Kumar Kartikeya Dwivedi <memxor@xxxxxxxxx>
Signed-off-by: Martin KaFai Lau <martin.lau@xxxxxxxxxx>
---
kernel/bpf/helpers.c | 22 ++++++++++++++++++++++
kernel/bpf/verifier.c | 12 ++++++++++--
2 files changed, 32 insertions(+), 2 deletions(-)
diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index 36150d340c16..78cefb41266a 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -2293,6 +2293,26 @@ __bpf_kfunc struct bpf_list_node *bpf_list_pop_back(struct bpf_list_head *head)
return __bpf_list_del(head, true);
}
+__bpf_kfunc struct bpf_list_node *bpf_list_front(struct bpf_list_head *head)
+{
+ struct list_head *h = (struct list_head *)head;
+
+ if (list_empty(h) || unlikely(!h->next))
+ return NULL;
+
+ return (struct bpf_list_node *)h->next;
+}
+
+__bpf_kfunc struct bpf_list_node *bpf_list_back(struct bpf_list_head *head)
+{
+ struct list_head *h = (struct list_head *)head;
+
+ if (list_empty(h) || unlikely(!h->next))
+ return NULL;
+
+ return (struct bpf_list_node *)h->prev;
+}
+
__bpf_kfunc struct bpf_rb_node *bpf_rbtree_remove(struct bpf_rb_root *root,
struct bpf_rb_node *node)
{
@@ -3236,6 +3256,8 @@ BTF_ID_FLAGS(func, bpf_list_push_front_impl)
BTF_ID_FLAGS(func, bpf_list_push_back_impl)
BTF_ID_FLAGS(func, bpf_list_pop_front, KF_ACQUIRE | KF_RET_NULL)
BTF_ID_FLAGS(func, bpf_list_pop_back, KF_ACQUIRE | KF_RET_NULL)
+BTF_ID_FLAGS(func, bpf_list_front, KF_RET_NULL)
+BTF_ID_FLAGS(func, bpf_list_back, KF_RET_NULL)
BTF_ID_FLAGS(func, bpf_task_acquire, KF_ACQUIRE | KF_RCU | KF_RET_NULL)
BTF_ID_FLAGS(func, bpf_task_release, KF_RELEASE)
BTF_ID_FLAGS(func, bpf_rbtree_remove, KF_ACQUIRE | KF_RET_NULL)
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index acb2f44316cc..99aa2c890e7b 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -12079,6 +12079,8 @@ enum special_kfunc_type {
KF_bpf_list_push_back_impl,
KF_bpf_list_pop_front,
KF_bpf_list_pop_back,
+ KF_bpf_list_front,
+ KF_bpf_list_back,
KF_bpf_cast_to_kern_ctx,
KF_bpf_rdonly_cast,
KF_bpf_rcu_read_lock,
@@ -12124,6 +12126,8 @@ BTF_ID(func, bpf_list_push_front_impl)
BTF_ID(func, bpf_list_push_back_impl)
BTF_ID(func, bpf_list_pop_front)
BTF_ID(func, bpf_list_pop_back)
+BTF_ID(func, bpf_list_front)
+BTF_ID(func, bpf_list_back)
BTF_ID(func, bpf_cast_to_kern_ctx)
BTF_ID(func, bpf_rdonly_cast)
BTF_ID(func, bpf_rbtree_remove)
@@ -12160,6 +12164,8 @@ BTF_ID(func, bpf_list_push_front_impl)
BTF_ID(func, bpf_list_push_back_impl)
BTF_ID(func, bpf_list_pop_front)
BTF_ID(func, bpf_list_pop_back)
+BTF_ID(func, bpf_list_front)
+BTF_ID(func, bpf_list_back)
BTF_ID(func, bpf_cast_to_kern_ctx)
BTF_ID(func, bpf_rdonly_cast)
BTF_ID(func, bpf_rcu_read_lock)
@@ -12598,7 +12604,9 @@ static bool is_bpf_list_api_kfunc(u32 btf_id)
return btf_id == special_kfunc_list[KF_bpf_list_push_front_impl] ||
btf_id == special_kfunc_list[KF_bpf_list_push_back_impl] ||
btf_id == special_kfunc_list[KF_bpf_list_pop_front] ||
- btf_id == special_kfunc_list[KF_bpf_list_pop_back];
+ btf_id == special_kfunc_list[KF_bpf_list_pop_back] ||
+ btf_id == special_kfunc_list[KF_bpf_list_front] ||
+ btf_id == special_kfunc_list[KF_bpf_list_back];
}
static bool is_bpf_rbtree_api_kfunc(u32 btf_id)
@@ -13903,7 +13911,7 @@ static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
if (is_kfunc_ret_null(&meta))
regs[BPF_REG_0].id = id;
regs[BPF_REG_0].ref_obj_id = id;
- } else if (is_rbtree_node_type(ptr_type)) {
+ } else if (is_rbtree_node_type(ptr_type) || is_list_node_type(ptr_type)) {
ref_set_non_owning(env, ®s[BPF_REG_0]);
}
--
2.47.1
