On Wed, May 12, 2021 at 2:33 PM Alexei Starovoitov
<alexei.starovoitov@xxxxxxxxx> wrote:
>
> From: Alexei Starovoitov <ast@xxxxxxxxxx>
>
> Introduce bpf_map__initial_value() to read initial contents
> of rodata/bss maps. Note only mmaped maps qualify.
> Just as bpf_map__set_initial_value() works only for mmaped kconfig.
This sentence is confusing. bpf_map__set_initial_value() rejects
LIBBPF_MAP_KCONFIG, so it *doesn't* work for kconfig. But your
implementation will return non-NULL pointer for kconfig (it will be
all zeroes before load). So did you intend to match
set_initial_value() semantics or not?
>
> Signed-off-by: Alexei Starovoitov <ast@xxxxxxxxxx>
> ---
> tools/lib/bpf/libbpf.c | 8 ++++++++
> tools/lib/bpf/libbpf.h | 1 +
> tools/lib/bpf/libbpf.map | 1 +
> 3 files changed, 10 insertions(+)
>
> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> index 8fd70f0592ad..8d3b136c6b29 100644
> --- a/tools/lib/bpf/libbpf.c
> +++ b/tools/lib/bpf/libbpf.c
> @@ -9736,6 +9736,14 @@ int bpf_map__set_initial_value(struct bpf_map *map,
> return 0;
> }
>
> +const void *bpf_map__initial_value(struct bpf_map *map, size_t *psize)
> +{
> + if (!map->mmaped)
> + return NULL;
> + *psize = map->def.value_size;
> + return map->mmaped;
> +}
> +
> bool bpf_map__is_offload_neutral(const struct bpf_map *map)
> {
> return map->def.type == BPF_MAP_TYPE_PERF_EVENT_ARRAY;
> diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
> index 8cf168f3717c..a50eab5fec0a 100644
> --- a/tools/lib/bpf/libbpf.h
> +++ b/tools/lib/bpf/libbpf.h
> @@ -471,6 +471,7 @@ LIBBPF_API int bpf_map__set_priv(struct bpf_map *map, void *priv,
> LIBBPF_API void *bpf_map__priv(const struct bpf_map *map);
> LIBBPF_API int bpf_map__set_initial_value(struct bpf_map *map,
> const void *data, size_t size);
> +LIBBPF_API const void *bpf_map__initial_value(struct bpf_map *map, size_t *psize);
> LIBBPF_API bool bpf_map__is_offload_neutral(const struct bpf_map *map);
> LIBBPF_API bool bpf_map__is_internal(const struct bpf_map *map);
> LIBBPF_API int bpf_map__set_pin_path(struct bpf_map *map, const char *path);
> diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
> index 889ee2f3611c..dd0f24370939 100644
> --- a/tools/lib/bpf/libbpf.map
> +++ b/tools/lib/bpf/libbpf.map
> @@ -359,6 +359,7 @@ LIBBPF_0.4.0 {
> bpf_linker__finalize;
> bpf_linker__free;
> bpf_linker__new;
> + bpf_map__initial_value;
> bpf_map__inner_map;
> bpf_object__gen_loader;
> bpf_object__set_kversion;
> --
> 2.30.2
>
