On Thu, Nov 14, 2019 at 5:04 PM Daniel Borkmann <daniel@xxxxxxxxxxxxx> wrote:
>
> 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.
>
> 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: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
> ---
> include/linux/bpf.h | 36 +++++++++++++
> kernel/bpf/arraymap.c | 120 +++++++++++++++++++++++++++++++++++++++++-
> kernel/bpf/core.c | 9 +++-
> 3 files changed, 162 insertions(+), 3 deletions(-)
>
> diff --git a/include/linux/bpf.h b/include/linux/bpf.h
> index 0ff06a0d0058..62a369fb8d98 100644
> --- a/include/linux/bpf.h
> +++ b/include/linux/bpf.h
> @@ -21,6 +21,7 @@ struct bpf_verifier_env;
> struct bpf_verifier_log;
> struct perf_event;
> struct bpf_prog;
> +struct bpf_prog_aux;
> struct bpf_map;
> struct sock;
> struct seq_file;
> @@ -63,6 +64,12 @@ struct bpf_map_ops {
> const struct btf_type *key_type,
> const struct btf_type *value_type);
>
> + /* Prog poke tracking helpers. */
> + int (*map_poke_track)(struct bpf_map *map, struct bpf_prog_aux *aux);
> + void (*map_poke_untrack)(struct bpf_map *map, struct bpf_prog_aux *aux);
> + void (*map_poke_run)(struct bpf_map *map, u32 key, struct bpf_prog *old,
> + struct bpf_prog *new);
You are passing bpf_prog_aux for track/untrack, but bpf_prog itself
for run. Maybe stick to just bpf_prog everywhere?
> +
> /* Direct value access helpers. */
> int (*map_direct_value_addr)(const struct bpf_map *map,
> u64 *imm, u32 off);
> @@ -584,6 +591,9 @@ struct bpf_array_aux {
> */
> enum bpf_prog_type type;
> bool jited;
> + /* Programs with direct jumps into programs part of this array. */
> + struct list_head poke_progs;
> + struct mutex poke_mutex;
> };
>
[...]
