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

[Yonghong Song <yhs@fb.com>]

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;