• Mauricio Vasquez B's avatar
    bpf: add queue and stack maps · f1a2e44a
    Mauricio Vasquez B authored
    Queue/stack maps implement a FIFO/LIFO data storage for ebpf programs.
    These maps support peek, pop and push operations that are exposed to eBPF
    programs through the new bpf_map[peek/pop/push] helpers.  Those operations
    are exposed to userspace applications through the already existing
    syscalls in the following way:
    BPF_MAP_LOOKUP_ELEM            -> peek
    BPF_MAP_UPDATE_ELEM            -> push
    Queue/stack maps are implemented using a buffer, tail and head indexes,
    hence BPF_F_NO_PREALLOC is not supported.
    As opposite to other maps, queue and stack do not use RCU for protecting
    maps values, the bpf_map[peek/pop] have a ARG_PTR_TO_UNINIT_MAP_VALUE
    argument that is a pointer to a memory zone where to save the value of a
    map.  Basically the same as ARG_PTR_TO_UNINIT_MEM, but the size has not
    be passed as an extra argument.
    Our main motivation for implementing queue/stack maps was to keep track
    of a pool of elements, like network ports in a SNAT, however we forsee
    other use cases, like for exampling saving last N kernel events in a map
    and then analysing from userspace.
    Signed-off-by: default avatarMauricio Vasquez B <mauricio.vasquez@polito.it>
    Acked-by: default avatarSong Liu <songliubraving@fb.com>
    Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
bpf.h 26.8 KB