Commit 6b0a249a authored by Yonghong Song's avatar Yonghong Song Committed by Alexei Starovoitov
Browse files

bpf: Implement link_query for bpf iterators 



This patch implemented bpf_link callback functions
show_fdinfo and fill_link_info to support link_query
interface.

The general interface for show_fdinfo and fill_link_info
will print/fill the target_name. Each targets can
register show_fdinfo and fill_link_info callbacks
to print/fill more target specific information.

For example, the below is a fdinfo result for a bpf
task iterator.
  $ cat /proc/1749/fdinfo/7
  pos:    0
  flags:  02000000
  mnt_id: 14
  link_type:      iter
  link_id:        11
  prog_tag:       990e1f8152f7e54f
  prog_id:        59
  target_name:    task

Signed-off-by: default avatarYonghong Song <yhs@fb.com>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200821184418.574122-1-yhs@fb.com
parent 149cb339

include/linux/bpf.h

+6 −0
Original line number Diff line number Diff line
@@ -1218,12 +1218,18 @@ typedef int (*bpf_iter_attach_target_t)(struct bpf_prog *prog, 
					union bpf_iter_link_info *linfo,

					struct bpf_iter_aux_info *aux);

typedef void (*bpf_iter_detach_target_t)(struct bpf_iter_aux_info *aux);

typedef void (*bpf_iter_show_fdinfo_t) (const struct bpf_iter_aux_info *aux,

					struct seq_file *seq);

typedef int (*bpf_iter_fill_link_info_t)(const struct bpf_iter_aux_info *aux,

					 struct bpf_link_info *info);



#define BPF_ITER_CTX_ARG_MAX 2

struct bpf_iter_reg {

	const char *target;

	bpf_iter_attach_target_t attach_target;

	bpf_iter_detach_target_t detach_target;

	bpf_iter_show_fdinfo_t show_fdinfo;

	bpf_iter_fill_link_info_t fill_link_info;

	u32 ctx_arg_info_size;

	struct bpf_ctx_arg_aux ctx_arg_info[BPF_ITER_CTX_ARG_MAX];

	const struct bpf_iter_seq_info *seq_info;

include/uapi/linux/bpf.h

+7 −0
Original line number Diff line number Diff line
@@ -4071,6 +4071,13 @@ struct bpf_link_info { 
			__u64 cgroup_id;

			__u32 attach_type;

		} cgroup;

		struct {

			__aligned_u64 target_name; /* in/out: target_name buffer ptr */

			__u32 target_name_len;	   /* in/out: target_name buffer len */

			union {

				__u32 map_id;

			} map;

		} iter;

		struct  {

			__u32 netns_ino;

			__u32 attach_type;

kernel/bpf/bpf_iter.c

+58 −0
Original line number Diff line number Diff line
@@ -377,10 +377,68 @@ out_unlock: 
	return ret;

}



static void bpf_iter_link_show_fdinfo(const struct bpf_link *link,

				      struct seq_file *seq)

{

	struct bpf_iter_link *iter_link =

		container_of(link, struct bpf_iter_link, link);

	bpf_iter_show_fdinfo_t show_fdinfo;



	seq_printf(seq,

		   "target_name:\t%s\n",

		   iter_link->tinfo->reg_info->target);



	show_fdinfo = iter_link->tinfo->reg_info->show_fdinfo;

	if (show_fdinfo)

		show_fdinfo(&iter_link->aux, seq);

}



static int bpf_iter_link_fill_link_info(const struct bpf_link *link,

					struct bpf_link_info *info)

{

	struct bpf_iter_link *iter_link =

		container_of(link, struct bpf_iter_link, link);

	char __user *ubuf = u64_to_user_ptr(info->iter.target_name);

	bpf_iter_fill_link_info_t fill_link_info;

	u32 ulen = info->iter.target_name_len;

	const char *target_name;

	u32 target_len;



	if (!ulen ^ !ubuf)

		return -EINVAL;



	target_name = iter_link->tinfo->reg_info->target;

	target_len =  strlen(target_name);

	info->iter.target_name_len = target_len + 1;



	if (ubuf) {

		if (ulen >= target_len + 1) {

			if (copy_to_user(ubuf, target_name, target_len + 1))

				return -EFAULT;

		} else {

			char zero = '\0';



			if (copy_to_user(ubuf, target_name, ulen - 1))

				return -EFAULT;

			if (put_user(zero, ubuf + ulen - 1))

				return -EFAULT;

			return -ENOSPC;

		}

	}



	fill_link_info = iter_link->tinfo->reg_info->fill_link_info;

	if (fill_link_info)

		return fill_link_info(&iter_link->aux, info);



	return 0;

}



static const struct bpf_link_ops bpf_iter_link_lops = {

	.release = bpf_iter_link_release,

	.dealloc = bpf_iter_link_dealloc,

	.update_prog = bpf_iter_link_replace,

	.show_fdinfo = bpf_iter_link_show_fdinfo,

	.fill_link_info = bpf_iter_link_fill_link_info,

};



bool bpf_link_is_iter(struct bpf_link *link)

tools/include/uapi/linux/bpf.h

+7 −0
Original line number Diff line number Diff line
@@ -4071,6 +4071,13 @@ struct bpf_link_info { 
			__u64 cgroup_id;

			__u32 attach_type;

		} cgroup;

		struct {

			__aligned_u64 target_name; /* in/out: target_name buffer ptr */

			__u32 target_name_len;	   /* in/out: target_name buffer len */

			union {

				__u32 map_id;

			} map;

		} iter;

		struct  {

			__u32 netns_ino;

			__u32 attach_type;

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