bpf: btf: Add struct bpf_btf_info

During BPF_OBJ_GET_INFO_BY_FD on a btf_fd, the current bpf_attr's
info.info is directly filled with the BTF binary data.  It is
not extensible.  In this case, we want to add BTF ID.

This patch adds "struct bpf_btf_info" which has the BTF ID as
one of its member.  The BTF binary data itself is exposed through
the "btf" and "btf_size" members.

Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Acked-by: Alexei Starovoitov <ast@fb.com>
Acked-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

1 files changed, 16 insertions, 1 deletions

diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 31c4092da277..e2aeb5e89f44 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -2021,6 +2021,21 @@ static int bpf_map_get_info_by_fd(struct bpf_map *map,
         return 0;
 }
 
+static int bpf_btf_get_info_by_fd(struct btf *btf,
+                                  const union bpf_attr *attr,
+                                  union bpf_attr __user *uattr)
+{
+        struct bpf_btf_info __user *uinfo = u64_to_user_ptr(attr->info.info);
+        u32 info_len = attr->info.info_len;
+        int err;
+
+        err = check_uarg_tail_zero(uinfo, sizeof(*uinfo), info_len);
+        if (err)
+                return err;
+
+        return btf_get_info_by_fd(btf, attr, uattr);
+}
+
 #define BPF_OBJ_GET_INFO_BY_FD_LAST_FIELD info.info
 
 static int bpf_obj_get_info_by_fd(const union bpf_attr *attr,
@@ -2044,7 +2059,7 @@ static int bpf_obj_get_info_by_fd(const union bpf_attr *attr,
                 err = bpf_map_get_info_by_fd(f.file->private_data, attr,
                                              uattr);
         else if (f.file->f_op == &btf_fops)
-                err = btf_get_info_by_fd(f.file->private_data, attr, uattr);
+                err = bpf_btf_get_info_by_fd(f.file->private_data, attr, uattr);
         else
                 err = -EINVAL;