> On Nov 7, 2019, at 8:20 PM, Andrii Nakryiko <andriin@xxxxxx> wrote:
>
> Add detection of BPF_F_MMAPABLE flag support for arrays and add it as an extra
> flag to internal global data maps, if supported by kernel. This allows users
> to memory-map global data and use it without BPF map operations, greatly
> simplifying user experience.
>
> Signed-off-by: Andrii Nakryiko <andriin@xxxxxx>
Acked-by: Song Liu <songliubraving@xxxxxx>
With nit below.
> ---
> tools/lib/bpf/libbpf.c | 31 +++++++++++++++++++++++++++++--
> 1 file changed, 29 insertions(+), 2 deletions(-)
>
> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> index fde6cb3e5d41..73607a31a068 100644
> --- a/tools/lib/bpf/libbpf.c
> +++ b/tools/lib/bpf/libbpf.c
> @@ -142,6 +142,8 @@ struct bpf_capabilities {
> __u32 btf_func:1;
> /* BTF_KIND_VAR and BTF_KIND_DATASEC support */
> __u32 btf_datasec:1;
> + /* BPF_F_MMAPABLE is supported for arrays */
> + __u32 array_mmap:1;
> };
>
> /*
> @@ -855,8 +857,6 @@ bpf_object__init_internal_map(struct bpf_object *obj, enum libbpf_map_type type,
> pr_warn("failed to alloc map name\n");
> return -ENOMEM;
> }
> - pr_debug("map '%s' (global data): at sec_idx %d, offset %zu.\n",
> - map_name, map->sec_idx, map->sec_offset);
>
> def = &map->def;
> def->type = BPF_MAP_TYPE_ARRAY;
> @@ -864,6 +864,12 @@ bpf_object__init_internal_map(struct bpf_object *obj, enum libbpf_map_type type,
> def->value_size = data->d_size;
> def->max_entries = 1;
> def->map_flags = type == LIBBPF_MAP_RODATA ? BPF_F_RDONLY_PROG : 0;
> + if (obj->caps.array_mmap)
> + def->map_flags |= BPF_F_MMAPABLE;
> +
> + pr_debug("map '%s' (global data): at sec_idx %d, offset %zu, flags %u.\n",
nit: Better print flags as %x.
