Re: [RFC PATCH bpf-next 05/16] bpf: create file or anonymous dumpers

Alexei Starovoitov
2020-04-10T03:00:24Z

On Wed, Apr 08, 2020 at 04:25:26PM -0700, Yonghong Song wrote:
> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> index 0f1cbed446c1..b51d56fc77f9 100644
> --- a/include/uapi/linux/bpf.h
> +++ b/include/uapi/linux/bpf.h
> @@ -354,6 +354,7 @@ enum {
> /* Flags for accessing BPF object from syscall side. */
> BPF_F_RDONLY = (1U << 3),
> BPF_F_WRONLY = (1U << 4),
> + BPF_F_DUMP = (1U << 5),
...
> static int bpf_obj_pin(const union bpf_attr *attr)
> {
> - if (CHECK_ATTR(BPF_OBJ) || attr->file_flags != 0)
> + if (CHECK_ATTR(BPF_OBJ) || attr->file_flags & ~BPF_F_DUMP)
> return -EINVAL;
>
> + if (attr->file_flags == BPF_F_DUMP)
> + return bpf_dump_create(attr->bpf_fd,
> + u64_to_user_ptr(attr->dumper_name));
> +
> return bpf_obj_pin_user(attr->bpf_fd, u64_to_user_ptr(attr->pathname));
> }

I think kernel can be a bit smarter here. There is no need for user space
to pass BPF_F_DUMP flag to kernel just to differentiate the pinning.
Can prog attach type be used instead?