On 5/8/20 11:24 AM, Andrii Nakryiko wrote:
On Wed, May 6, 2020 at 10:41 PM Yonghong Song <yhs@xxxxxx> wrote:
Given a bpf program, the step to create an anonymous bpf iterator is:
- create a bpf_iter_link, which combines bpf program and the target.
In the future, there could be more information recorded in the link.
A link_fd will be returned to the user space.
- create an anonymous bpf iterator with the given link_fd.
The bpf_iter_link can be pinned to bpffs mount file system to
create a file based bpf iterator as well.
The benefit to use of bpf_iter_link:
- using bpf link simplifies design and implementation as bpf link
is used for other tracing bpf programs.
- for file based bpf iterator, bpf_iter_link provides a standard
way to replace underlying bpf programs.
- for both anonymous and free based iterators, bpf link query
capability can be leveraged.
The patch added support of tracing/iter programs for BPF_LINK_CREATE.
A new link type BPF_LINK_TYPE_ITER is added to facilitate link
querying. Currently, only prog_id is needed, so there is no
additional in-kernel show_fdinfo() and fill_link_info() hook
is needed for BPF_LINK_TYPE_ITER link.
Acked-by: Andrii Nakryiko <andriin@xxxxxx>
Signed-off-by: Yonghong Song <yhs@xxxxxx>
---
still looks good, but I realized show_fdinfo and fill_link_info is
missing, see request for a follow-up below :)
include/linux/bpf.h | 1 +
include/linux/bpf_types.h | 1 +
include/uapi/linux/bpf.h | 1 +
kernel/bpf/bpf_iter.c | 62 ++++++++++++++++++++++++++++++++++
kernel/bpf/syscall.c | 14 ++++++++
tools/include/uapi/linux/bpf.h | 1 +
6 files changed, 80 insertions(+)
[...]
+static const struct bpf_link_ops bpf_iter_link_lops = {
+ .release = bpf_iter_link_release,
+ .dealloc = bpf_iter_link_dealloc,
+};
Link infra supports .show_fdinfo and .fill_link_info methods, there is
no need to block on this, but it would be great to implement them from
BPF_LINK_TYPE_ITER as well in the same release as a follow-up. Thanks!
The reason I did not implement is due to we do not have additional
information beyond prog_id to present. The prog_id itself gives all
information about this link. I looked at tracing program
show_fdinfo/fill_link_info, the additional attach_type is printed.
But attach_type is obvious for BPF_LINK_TYPE_ITER which does not
need print.
In the future when we add more stuff to parameterize the bpf_iter,
will need to implement these two callbacks as well as bpftool.
[...]
