bpf: pass btf object id in bpf_map_info.

Include btf object id (btf_obj_id) in bpf_map_info so that tools (ex:
bpftools struct_ops dump) know the correct btf from the kernel to look up
type information of struct_ops types.

Since struct_ops types can be defined and registered in a module. The
type information of a struct_ops type are defined in the btf of the
module defining it.  The userspace tools need to know which btf is for
the module defining a struct_ops type.

Signed-off-by: Kui-Feng Lee <thinker.li@gmail.com>
Link: https://lore.kernel.org/r/20240119225005.668602-7-thinker.li@gmail.com
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>

1 files changed, 7 insertions, 0 deletions

diff --git a/kernel/bpf/bpf_struct_ops.c b/kernel/bpf/bpf_struct_ops.c
index 5ddcca4c4fba..5e98af4fc2e2 100644
--- a/kernel/bpf/bpf_struct_ops.c
+++ b/kernel/bpf/bpf_struct_ops.c
@@ -947,3 +947,10 @@ err_out:
 	kfree(link);
 	return err;
 }
+
+void bpf_map_struct_ops_info_fill(struct bpf_map_info *info, struct bpf_map *map)
+{
+	struct bpf_struct_ops_map *st_map = (struct bpf_struct_ops_map *)map;
+
+	info->btf_vmlinux_id = btf_obj_id(st_map->btf);
+}