> On May 4, 2018, at 2:49 PM, Martin KaFai Lau <ka...@fb.com> wrote:
>
> 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 <ka...@fb.com>
> Acked-by: Alexei Starovoitov <a...@fb.com>
> ---
> include/uapi/linux/bpf.h | 6 ++++++
> kernel/bpf/btf.c | 26 +++++++++++++++++++++-----
> kernel/bpf/syscall.c | 17 ++++++++++++++++-
> 3 files changed, 43 insertions(+), 6 deletions(-)
>
> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> index 6106f23a9a8a..d615c777b573 100644
> --- a/include/uapi/linux/bpf.h
> +++ b/include/uapi/linux/bpf.h
> @@ -2137,6 +2137,12 @@ struct bpf_map_info {
> __u32 btf_value_id;
> } __attribute__((aligned(8)));
>
> +struct bpf_btf_info {
> + __aligned_u64 btf;
> + __u32 btf_size;
> + __u32 id;
> +} __attribute__((aligned(8)));
> +
> /* User bpf_sock_addr struct to access socket fields and sockaddr struct
> passed
> * by user and intended to be used by socket (e.g. to bind to, depends on
> * attach attach type).
> diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
> index 40950b6bf395..ded10ab47b8a 100644
> --- a/kernel/bpf/btf.c
> +++ b/kernel/bpf/btf.c
> @@ -2114,12 +2114,28 @@ int btf_get_info_by_fd(const struct btf *btf,
> const union bpf_attr *attr,
> union bpf_attr __user *uattr)
> {
> - void __user *udata = u64_to_user_ptr(attr->info.info);
> - u32 copy_len = min_t(u32, btf->data_size,
> - attr->info.info_len);
> + struct bpf_btf_info __user *uinfo;
> + struct bpf_btf_info info = {};
> + u32 info_copy, btf_copy;
> + void __user *ubtf;
> + u32 uinfo_len;
>
> - if (copy_to_user(udata, btf->data, copy_len) ||
> - put_user(btf->data_size, &uattr->info.info_len))
> + uinfo = u64_to_user_ptr(attr->info.info);
> + uinfo_len = attr->info.info_len;
> +
> + info_copy = min_t(u32, uinfo_len, sizeof(info));
> + if (copy_from_user(&info, uinfo, info_copy))
> + return -EFAULT;
> +
> + info.id = btf->id;
> + ubtf = u64_to_user_ptr(info.btf);
> + btf_copy = min_t(u32, btf->data_size, info.btf_size);
> + if (copy_to_user(ubtf, btf->data, btf_copy))
> + return -EFAULT;
> + info.btf_size = btf->data_size;
> +
> + if (copy_to_user(uinfo, &info, info_copy) ||
> + put_user(info_copy, &uattr->info.info_len))
> return -EFAULT;
>
> return 0;
> diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
> index 8b0a45d65454..d2895e3e5cbf 100644
> --- a/kernel/bpf/syscall.c
> +++ b/kernel/bpf/syscall.c
> @@ -2019,6 +2019,21 @@ 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,
> @@ -2042,7 +2057,7 @@ 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;
>
> --
> 2.9.5
>
Acked-by: Song Liu <songliubrav...@fb.com>
