Commit 96c85308 authored by Andrii Nakryiko's avatar Andrii Nakryiko Committed by Alexei Starovoitov
Browse files

docs/bpf: update BPF map definition example 



Use BTF-defined map definition in the documentation example.

Signed-off-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20220120060529.1890907-5-andrii@kernel.org


Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent 93b8952d

Documentation/bpf/btf.rst

+14 −18
Original line number Diff line number Diff line
@@ -565,18 +565,15 @@ A map can be created with ``btf_fd`` and specified key/value type id.:: 
In libbpf, the map can be defined with extra annotation like below:

::



    struct bpf_map_def SEC("maps") btf_map = {

        .type = BPF_MAP_TYPE_ARRAY,

        .key_size = sizeof(int),

        .value_size = sizeof(struct ipv_counts),

        .max_entries = 4,

    };

    BPF_ANNOTATE_KV_PAIR(btf_map, int, struct ipv_counts);

    struct {

        __uint(type, BPF_MAP_TYPE_ARRAY);

        __type(key, int);

        __type(value, struct ipv_counts);

        __uint(max_entries, 4);

    } btf_map SEC(".maps");



Here, the parameters for macro BPF_ANNOTATE_KV_PAIR are map name, key and

value types for the map. During ELF parsing, libbpf is able to extract

key/value type_id's and assign them to BPF_MAP_CREATE attributes

automatically.

During ELF parsing, libbpf is able to extract key/value type_id's and assign

them to BPF_MAP_CREATE attributes automatically.



.. _BPF_Prog_Load:
@@ -824,13 +821,12 @@ structure has bitfields. For example, for the following map,:: 
           ___A b1:4;

           enum A b2:4;

      };

      struct bpf_map_def SEC("maps") tmpmap = {

           .type = BPF_MAP_TYPE_ARRAY,

           .key_size = sizeof(__u32),

           .value_size = sizeof(struct tmp_t),

           .max_entries = 1,

      };

      BPF_ANNOTATE_KV_PAIR(tmpmap, int, struct tmp_t);

      struct {

           __uint(type, BPF_MAP_TYPE_ARRAY);

           __type(key, int);

           __type(value, struct tmp_t);

           __uint(max_entries, 1);

      } tmpmap SEC(".maps");



bpftool is able to pretty print like below:

::