From b5709f6d26d65f6bb9711f4b5f98469fd507cb5b Mon Sep 17 00:00:00 2001 From: Amery Hung Date: Wed, 3 Dec 2025 15:37:44 -0800 Subject: bpf: Support associating BPF program with struct_ops Add a new BPF command BPF_PROG_ASSOC_STRUCT_OPS to allow associating a BPF program with a struct_ops map. This command takes a file descriptor of a struct_ops map and a BPF program and set prog->aux->st_ops_assoc to the kdata of the struct_ops map. The command does not accept a struct_ops program nor a non-struct_ops map. Programs of a struct_ops map is automatically associated with the map during map update. If a program is shared between two struct_ops maps, prog->aux->st_ops_assoc will be poisoned to indicate that the associated struct_ops is ambiguous. The pointer, once poisoned, cannot be reset since we have lost track of associated struct_ops. For other program types, the associated struct_ops map, once set, cannot be changed later. This restriction may be lifted in the future if there is a use case. A kernel helper bpf_prog_get_assoc_struct_ops() can be used to retrieve the associated struct_ops pointer. The returned pointer, if not NULL, is guaranteed to be valid and point to a fully updated struct_ops struct. For struct_ops program reused in multiple struct_ops map, the return will be NULL. prog->aux->st_ops_assoc is protected by bumping the refcount for non-struct_ops programs and RCU for struct_ops programs. Since it would be inefficient to track programs associated with a struct_ops map, every non-struct_ops program will bump the refcount of the map to make sure st_ops_assoc stays valid. For a struct_ops program, it is protected by RCU as map_free will wait for an RCU grace period before disassociating the program with the map. The helper must be called in BPF program context or RCU read-side critical section. struct_ops implementers should note that the struct_ops returned may not be initialized nor attached yet. The struct_ops implementer will be responsible for tracking and checking the state of the associated struct_ops map if the use case expects an initialized or attached struct_ops. Signed-off-by: Amery Hung Signed-off-by: Andrii Nakryiko Acked-by: Andrii Nakryiko Acked-by: Martin KaFai Lau Link: https://lore.kernel.org/bpf/20251203233748.668365-3-ameryhung@gmail.com --- include/linux/bpf.h | 16 ++++++++++++++++ 1 file changed, 16 insertions(+) (limited to 'include/linux') diff --git a/include/linux/bpf.h b/include/linux/bpf.h index 6498be4c44f8..28d8d6b7bb1e 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -1739,6 +1739,8 @@ struct bpf_prog_aux { struct rcu_head rcu; }; struct bpf_stream stream[2]; + struct mutex st_ops_assoc_mutex; + struct bpf_map __rcu *st_ops_assoc; }; struct bpf_prog { @@ -2041,6 +2043,9 @@ static inline void bpf_module_put(const void *data, struct module *owner) module_put(owner); } int bpf_struct_ops_link_create(union bpf_attr *attr); +int bpf_prog_assoc_struct_ops(struct bpf_prog *prog, struct bpf_map *map); +void bpf_prog_disassoc_struct_ops(struct bpf_prog *prog); +void *bpf_prog_get_assoc_struct_ops(const struct bpf_prog_aux *aux); u32 bpf_struct_ops_id(const void *kdata); #ifdef CONFIG_NET @@ -2088,6 +2093,17 @@ static inline int bpf_struct_ops_link_create(union bpf_attr *attr) { return -EOPNOTSUPP; } +static inline int bpf_prog_assoc_struct_ops(struct bpf_prog *prog, struct bpf_map *map) +{ + return -EOPNOTSUPP; +} +static inline void bpf_prog_disassoc_struct_ops(struct bpf_prog *prog) +{ +} +static inline void *bpf_prog_get_assoc_struct_ops(const struct bpf_prog_aux *aux) +{ + return NULL; +} static inline void bpf_map_struct_ops_info_fill(struct bpf_map_info *info, struct bpf_map *map) { } -- cgit v1.2.3