On 5/5/20 5:14 PM, Yonghong Song wrote:
On 5/5/20 2:30 PM, Andrii Nakryiko wrote:
On Sun, May 3, 2020 at 11:26 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.
Signed-off-by: Yonghong Song <yhs@xxxxxx>
---
LGTM. See small nit about __GFP_NOWARN.
Acked-by: Andrii Nakryiko <andriin@xxxxxx>
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(+)
[...]
+int bpf_iter_link_attach(const union bpf_attr *attr, struct bpf_prog
*prog)
+{
+ struct bpf_link_primer link_primer;
+ struct bpf_iter_target_info *tinfo;
+ struct bpf_iter_link *link;
+ bool existed = false;
+ u32 prog_btf_id;
+ int err;
+
+ if (attr->link_create.target_fd || attr->link_create.flags)
+ return -EINVAL;
+
+ prog_btf_id = prog->aux->attach_btf_id;
+ mutex_lock(&targets_mutex);
+ list_for_each_entry(tinfo, &targets, list) {
+ if (tinfo->btf_id == prog_btf_id) {
+ existed = true;
+ break;
+ }
+ }
+ mutex_unlock(&targets_mutex);
+ if (!existed)
+ return -ENOENT;
+
+ link = kzalloc(sizeof(*link), GFP_USER | __GFP_NOWARN);
nit: all existing link implementation don't specify __GFP_NOWARN,
wonder if bpf_iter_link should be special?
Nothing special. Just feel __GFP_NOWARN is the right thing to do to
avoid pollute dmesg since -ENOMEM is returned to user space. But in
reality, unlike some key/value allocation where the size could be huge
and __GFP_NOWARN might be more useful, here, sizeof(*link) is fixed
and small, __GFP_NOWARN probably not that useful.
Will drop it.
actually all existing user space driven allocation have nowarn.
If we missed it in other link allocs we should probably add it.
