Re: [PATCH bpf-next v6 2/4] bpf: Handle bpf_link_info for the parameterized task BPF iterators.

Yonghong Song
2022-08-24T19:42:20Z

On 8/19/22 3:09 PM, Kui-Feng Lee wrote:
> Add new fields to bpf_link_info that users can query it through
> bpf_obj_get_info_by_fd().
>
> Signed-off-by: Kui-Feng Lee <kuifeng@fb.com>

Acked-by: Yonghong Song <yhs@fb.com>

But we are missing bpftool implementation which actually dumps the
tid/pid here. So you need another bpftool patch to do this.
See file tools/bpf/bpftool/link.c to see how map_id is
printed.

> ---
> include/uapi/linux/bpf.h | 6 ++++++
> kernel/bpf/task_iter.c | 18 ++++++++++++++++++
> tools/include/uapi/linux/bpf.h | 6 ++++++
> 3 files changed, 30 insertions(+)
>
> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> index 778fbf11aa00..6647e052dd00 100644
> --- a/include/uapi/linux/bpf.h
> +++ b/include/uapi/linux/bpf.h
> @@ -6170,6 +6170,12 @@ struct bpf_link_info {
> __u32 map_id;
> } map;
> };
> + union {
> + struct {
> + __u32 tid;
> + __u32 pid;
> + } task;
> + };
> } iter;
> struct {
> __u32 netns_ino;
> diff --git a/kernel/bpf/task_iter.c b/kernel/bpf/task_iter.c
> index 2f5fc6602917..927b3a1cf354 100644
> --- a/kernel/bpf/task_iter.c
> +++ b/kernel/bpf/task_iter.c
> @@ -596,6 +596,21 @@ static const struct bpf_iter_seq_info task_seq_info = {
> .seq_priv_size = sizeof(struct bpf_iter_seq_task_info),
> };
>
> +static int bpf_iter_fill_link_info(const struct bpf_iter_aux_info *aux, struct bpf_link_info *info)
> +{
> + switch (aux->task.type) {
> + case BPF_TASK_ITER_TID:
> + info->iter.task.tid = aux->task.pid;
> + break;
> + case BPF_TASK_ITER_TGID:
> + info->iter.task.pid = aux->task.pid;
> + break;
> + default:
> + break;
> + }
> + return 0;
> +}
> +
> static struct bpf_iter_reg task_reg_info = {
> .target = "task",
> .attach_target = bpf_iter_attach_task,
> @@ -606,6 +621,7 @@ static struct bpf_iter_reg task_reg_info = {
> PTR_TO_BTF_ID_OR_NULL },
> },
> .seq_info = &task_seq_info,
> + .fill_link_info = bpf_iter_fill_link_info,
> };
>
> static const struct bpf_iter_seq_info task_file_seq_info = {
> @@ -627,6 +643,7 @@ static struct bpf_iter_reg task_file_reg_info = {
> PTR_TO_BTF_ID_OR_NULL },
> },
> .seq_info = &task_file_seq_info,
> + .fill_link_info = bpf_iter_fill_link_info,
> };
>
> static const struct bpf_iter_seq_info task_vma_seq_info = {
> @@ -648,6 +665,7 @@ static struct bpf_iter_reg task_vma_reg_info = {
> PTR_TO_BTF_ID_OR_NULL },
> },
> .seq_info = &task_vma_seq_info,
> + .fill_link_info = bpf_iter_fill_link_info,
> };
>
> BPF_CALL_5(bpf_find_vma, struct task_struct *, task, u64, start,
> diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
> index 7a0268749a48..177722c5dd62 100644
> --- a/tools/include/uapi/linux/bpf.h
> +++ b/tools/include/uapi/linux/bpf.h
> @@ -6170,6 +6170,12 @@ struct bpf_link_info {
> __u32 map_id;
> } map;
> };
> + union {
> + struct {
> + __u32 tid;
> + __u32 pid;
> + } task;
> + };
> } iter;
> struct {
> __u32 netns_ino;