Re: [PATCH bpf-next 3/6] bpf: btf: Add struct bpf_btf_info

[Song Liu <songliubraving@fb.com>]

> On May 4, 2018, at 2:49 PM, Martin KaFai Lau <kafai@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 <kafai@fb.com>
> Acked-by: Alexei Starovoitov <ast@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 <songliubraving@fb.com>