• Daniel Borkmann's avatar
    bpf: Add poke dependency tracking for prog array maps · da765a2f
    Daniel Borkmann authored
    This work adds program tracking to prog array maps. This is needed such
    that upon prog array updates/deletions we can fix up all programs which
    make use of this tail call map. We add ops->map_poke_{un,}track()
    helpers to maps to maintain the list of programs and ops->map_poke_run()
    for triggering the actual update.
    
    bpf_array_aux is extended to contain the list head and poke_mutex in
    order to serialize program patching during updates/deletions.
    bpf_free_used_maps() will untrack the program shortly before dropping
    the reference to the map. For clearing out the prog array once all urefs
    are dropped we need to use schedule_work() to have a sleepable context.
    
    The prog_array_map_poke_run() is triggered during updates/deletions and
    walks the maintained prog list. It checks in their poke_tabs whether the
    map and key is matching and runs the actual bpf_arch_text_poke() for
    patching in the nop or new jmp location. Depending on the type of update,
    we use one of BPF_MOD_{NOP_TO_JUMP,JUMP_TO_NOP,JUMP_TO_JUMP}.
    Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
    Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
    Acked-by: default avatarAndrii Nakryiko <andriin@fb.com>
    Link: https://lore.kernel.org/bpf/1fb364bb3c565b3e415d5ea348f036ff379e779d.1574452833.git.daniel@iogearbox.net
    da765a2f
syscall.c 72 KB