Re: [RFC PATCH bpf-next 1/2] bpf: Add bpf_link iterator

[Andrii Nakryiko <andrii.nakryiko@gmail.com>]

On Fri, Apr 22, 2022 at 11:23 AM Dmitrii Dolgov <9erthalion6@gmail.com> wrote:
>
> Implement bpf_link iterator to traverse links via bpf_seq_file
> operations. The changeset is mostly shamelessly copied from
> commit a228a64fc1e4 ("bpf: Add bpf_prog iterator")
>
> Signed-off-by: Dmitrii Dolgov <9erthalion6@gmail.com>
> ---
>  include/linux/bpf.h    |   1 +
>  kernel/bpf/Makefile    |   2 +-
>  kernel/bpf/link_iter.c | 107 +++++++++++++++++++++++++++++++++++++++++
>  kernel/bpf/syscall.c   |  19 ++++++++
>  4 files changed, 128 insertions(+), 1 deletion(-)
>  create mode 100644 kernel/bpf/link_iter.c
>
> diff --git a/include/linux/bpf.h b/include/linux/bpf.h
> index 7bf441563ffc..330e88fcc50e 100644
> --- a/include/linux/bpf.h
> +++ b/include/linux/bpf.h
> @@ -1489,6 +1489,7 @@ void bpf_link_put(struct bpf_link *link);
>  int bpf_link_new_fd(struct bpf_link *link);
>  struct file *bpf_link_new_file(struct bpf_link *link, int *reserved_fd);
>  struct bpf_link *bpf_link_get_from_fd(u32 ufd);
> +struct bpf_link *bpf_link_get_curr_or_next(u32 *id);
>
>  int bpf_obj_pin_user(u32 ufd, const char __user *pathname);
>  int bpf_obj_get_user(const char __user *pathname, int flags);
> diff --git a/kernel/bpf/Makefile b/kernel/bpf/Makefile
> index c1a9be6a4b9f..057ba8e01e70 100644
> --- a/kernel/bpf/Makefile
> +++ b/kernel/bpf/Makefile
> @@ -6,7 +6,7 @@ cflags-nogcse-$(CONFIG_X86)$(CONFIG_CC_IS_GCC) := -fno-gcse
>  endif
>  CFLAGS_core.o += $(call cc-disable-warning, override-init) $(cflags-nogcse-yy)
>
> -obj-$(CONFIG_BPF_SYSCALL) += syscall.o verifier.o inode.o helpers.o tnum.o bpf_iter.o map_iter.o task_iter.o prog_iter.o
> +obj-$(CONFIG_BPF_SYSCALL) += syscall.o verifier.o inode.o helpers.o tnum.o bpf_iter.o map_iter.o task_iter.o prog_iter.o link_iter.o
>  obj-$(CONFIG_BPF_SYSCALL) += hashtab.o arraymap.o percpu_freelist.o bpf_lru_list.o lpm_trie.o map_in_map.o bloom_filter.o
>  obj-$(CONFIG_BPF_SYSCALL) += local_storage.o queue_stack_maps.o ringbuf.o
>  obj-$(CONFIG_BPF_SYSCALL) += bpf_local_storage.o bpf_task_storage.o
> diff --git a/kernel/bpf/link_iter.c b/kernel/bpf/link_iter.c
> new file mode 100644
> index 000000000000..fde41d09f26b
> --- /dev/null
> +++ b/kernel/bpf/link_iter.c
> @@ -0,0 +1,107 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/* Copyright (c) 2020 Facebook */

this probably needs a bit of update?

> +#include <linux/bpf.h>
> +#include <linux/fs.h>
> +#include <linux/filter.h>
> +#include <linux/kernel.h>
> +#include <linux/btf_ids.h>
> +
> +struct bpf_iter_seq_link_info {
> +       u32 link_id;
> +};
> +

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