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docs/bpf: update BPF map definition example

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Use BTF-defined map definition in the documentation example.

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20220120060529.1890907-5-andrii@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Andrii Nakryiko 2022-01-19 22:05:29 -08:00 committed by Alexei Starovoitov
parent 93b8952d22
commit 96c85308ee
1 changed files with 14 additions and 18 deletions
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32
Documentation/bpf/btf.rst
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@ -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:
::