On Mon, Mar 4, 2024 at 2:52 PM Eduard Zingerman <eddyz87@xxxxxxxxx> wrote:
>
> Allow using two new section names for struct_ops maps:
> - SEC("?.struct_ops")
> - SEC("?.struct_ops.link")
>
> To specify maps that have bpf_map->autocreate == false after open.
>
> Signed-off-by: Eduard Zingerman <eddyz87@xxxxxxxxx>
> ---
> tools/lib/bpf/libbpf.c | 17 ++++++++++++++++-
> 1 file changed, 16 insertions(+), 1 deletion(-)
>
Please check that patch subject is <80, and perhaps shorten it a bit?
> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> index 4ef3902e65db..c0212244bdf7 100644
> --- a/tools/lib/bpf/libbpf.c
> +++ b/tools/lib/bpf/libbpf.c
> @@ -497,6 +497,8 @@ struct bpf_struct_ops {
> #define KSYMS_SEC ".ksyms"
> #define STRUCT_OPS_SEC ".struct_ops"
> #define STRUCT_OPS_LINK_SEC ".struct_ops.link"
> +#define OPT_STRUCT_OPS_SEC "?.struct_ops"
> +#define OPT_STRUCT_OPS_LINK_SEC "?.struct_ops.link"
>
I wouldn't do this, see below
> enum libbpf_map_type {
> LIBBPF_MAP_UNSPEC,
> @@ -1324,6 +1326,15 @@ static int init_struct_ops_maps(struct bpf_object *obj, const char *sec_name,
> return -ENOMEM;
> map->btf_value_type_id = type_id;
>
> + /* Follow same convention as for programs autoload:
> + * SEC("?.struct_ops") means map is not created by default.
> + */
> + if (sec_name[0] == '?') {
> + map->autocreate = false;
> + /* from now on forget there was ? in section name */
> + sec_name++;
> + }
> +
> map->def.type = BPF_MAP_TYPE_STRUCT_OPS;
> map->def.key_size = sizeof(int);
> map->def.value_size = type->size;
> @@ -3688,7 +3699,9 @@ static int bpf_object__elf_collect(struct bpf_object *obj)
> sec_desc->shdr = sh;
> sec_desc->data = data;
> } else if (strcmp(name, STRUCT_OPS_SEC) == 0 ||
> - strcmp(name, STRUCT_OPS_LINK_SEC) == 0) {
> + strcmp(name, STRUCT_OPS_LINK_SEC) == 0 ||
> + strcmp(name, OPT_STRUCT_OPS_SEC) == 0 ||
> + strcmp(name, OPT_STRUCT_OPS_LINK_SEC) == 0) {
I'd do just
strcmp(name, "?" STRUCT_OPS_SEC) == 0 ||
strcmp(name, "?" STRUCT_OPS_LINK_SEC) == 0 ||
> sec_desc->sec_type = SEC_ST_OPS;
> sec_desc->shdr = sh;
> sec_desc->data = data;
> @@ -3708,6 +3721,8 @@ static int bpf_object__elf_collect(struct bpf_object *obj)
> if (!section_have_execinstr(obj, targ_sec_idx) &&
> strcmp(name, ".rel" STRUCT_OPS_SEC) &&
> strcmp(name, ".rel" STRUCT_OPS_LINK_SEC) &&
> + strcmp(name, ".rel" OPT_STRUCT_OPS_SEC) &&
> + strcmp(name, ".rel" OPT_STRUCT_OPS_LINK_SEC) &&
and similarly here, just use ".rel?" ?
> strcmp(name, ".rel" MAPS_ELF_SEC)) {
> pr_info("elf: skipping relo section(%d) %s for section(%d) %s\n",
> idx, name, targ_sec_idx,
> --
> 2.43.0
>
