STRUCT BPF_STRUCT_OPS(9)

💅 struct bpf_struct_ops 💅

okay so welcome to the Kernel API Manual page for struct bpf_struct_ops(9) — yes bestie, this is that struct. It's literally a structure of callbacks that lets a subsystem define a BPF_MAP_TYPE_STRUCT_OPS map type made up of BPF_PROG_TYPE_STRUCT_OPS progs. iconic behavior, no cap 🫶

✨ NAME ✨

struct bpf_struct_ops — a structure of callbacks allowing a subsystem to define a BPF_MAP_TYPE_STRUCT_OPS map type composed of BPF_PROG_TYPE_STRUCT_OPS progs. 💖

🌸 SYNOPSIS 🌸

struct bpf_struct_ops {
    const struct bpf_verifier_ops *verifier_ops;
    int (*init)(struct btf *btf);
    int (*check_member)(const struct btf_type *t, const struct btf_member *member, const struct bpf_prog *prog);
    int (*init_member)(const struct btf_type *t, const struct btf_member *member, void *kdata, const void *udata);
    int (*reg)(void *kdata, struct bpf_link *link);
    void (*unreg)(void *kdata, struct bpf_link *link);
    int (*update)(void *kdata, void *old_kdata, struct bpf_link *link);
    int (*validate)(void *kdata);
    void *cfi_stubs;
    struct module *owner;
    const char *name;
    struct btf_func_model func_models[BPF_STRUCT_OPS_MAX_NR_MEMBERS];
};

💖 Members 💖

• verifier_ops — a structure of callbacks that are invoked by the verifier when it's determining whether the struct_ops progs in the struct_ops map are valid. verifier vibe check, literally 💅
• init — a callback that is invoked a single time, and before any other callback, to initialize the structure. A nonzero return value means the subsystem could not be initialized. first one in, no cap ✨
• check_member — when defined, a callback invoked by the verifier to allow the subsystem to determine if an entry in the struct_ops map is valid. A nonzero return value means that the map is invalid and should be rejected by the verifier. reject the map, periodt 🚫
• init_member — a callback that is invoked for each member of the struct_ops map to allow the subsystem to initialize the member. A nonzero value means the member could not be initialized. This callback is exclusive with the type, type_id, value_type, and value_id fields. mutually exclusive bestie, don't mix 😭
• reg — a callback that is invoked when the struct_ops map has been initialized and is being attached to. Zero means the struct_ops map has been successfully registered and is live. A nonzero return value means the struct_ops map could not be registered. live and registered, slay ✅
• unreg — a callback that is invoked when the struct_ops map should be unregistered. time to say bye 👋
• update — a callback that is invoked when the live struct_ops map is being updated to contain new values. This callback is only invoked when the struct_ops map is loaded with BPF_F_LINK. If not defined, it is assumed that the struct_ops map cannot be updated. only with BPF_F_LINK, iykyk 🔥
• validate — a callback that is invoked after all of the members have been initialized. This callback should perform static checks on the map, meaning that it should either fail or succeed deterministically. A struct_ops map that has been validated may not necessarily succeed in being registered if the call to reg fails. For example, a valid struct_ops map may be loaded, but then fail to be registered due to there being another active struct_ops map on the system in the subsystem already. For this reason, if this callback is not defined, the check is skipped as the struct_ops map will have final verification performed in reg. deterministic checks only, no chaotic energy 🧚
• cfi_stubs — pointer to a structure of stub functions for CFI. These stubs provide the correct Control Flow Integrity hashes for the trampolines generated by BPF struct_ops. CFI stubs giving correct hashes 🔐
• owner — the module that owns this struct_ops. Used for module reference counting to ensure the module providing the struct_ops cannot be unloaded while in use. keeps the module pinned, no unload-while-in-use drama 🫶
• name — the name of the struct bpf_struct_ops object. name reveal 💫
• func_models — func models. that's the note, bestie 🍓

🔎 SEE ALSO 🔎

• Kernel file ./include/linux/bpf.h — go read it if you want the deep lore 📖

xoxo, your struct_ops bestie 💖 — from ./include/linux, source/version October 2026, all about struct bpf_struct_ops(9) 🫶