Commit 9f883612 authored by Dmitrii Dolgov's avatar Dmitrii Dolgov Committed by Alexei Starovoitov
Browse files

bpf: Add bpf_link iterator 



Implement bpf_link iterator to traverse links via bpf_seq_file
operations. The changeset is mostly shamelessly copied from
commit a228a64f ("bpf: Add bpf_prog iterator")

Signed-off-by: default avatarDmitrii Dolgov <9erthalion6@gmail.com>
Acked-by: default avatarYonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/r/20220510155233.9815-2-9erthalion6@gmail.com


Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent c4423a17

include/linux/bpf.h

+1 −0
Original line number Diff line number Diff line
@@ -1544,6 +1544,7 @@ 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);

kernel/bpf/Makefile

+1 −1
Original line number Diff line number Diff line
@@ -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

kernel/bpf/link_iter.c

0 → 100644
+107 −0
Original line number Diff line number Diff line 
// SPDX-License-Identifier: GPL-2.0-only

/* Copyright (c) 2022 Red Hat, Inc. */

#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;

};



static void *bpf_link_seq_start(struct seq_file *seq, loff_t *pos)

{

	struct bpf_iter_seq_link_info *info = seq->private;

	struct bpf_link *link;



	link = bpf_link_get_curr_or_next(&info->link_id);

	if (!link)

		return NULL;



	if (*pos == 0)

		++*pos;

	return link;

}



static void *bpf_link_seq_next(struct seq_file *seq, void *v, loff_t *pos)

{

	struct bpf_iter_seq_link_info *info = seq->private;



	++*pos;

	++info->link_id;

	bpf_link_put((struct bpf_link *)v);

	return bpf_link_get_curr_or_next(&info->link_id);

}



struct bpf_iter__bpf_link {

	__bpf_md_ptr(struct bpf_iter_meta *, meta);

	__bpf_md_ptr(struct bpf_link *, link);

};



DEFINE_BPF_ITER_FUNC(bpf_link, struct bpf_iter_meta *meta, struct bpf_link *link)



static int __bpf_link_seq_show(struct seq_file *seq, void *v, bool in_stop)

{

	struct bpf_iter__bpf_link ctx;

	struct bpf_iter_meta meta;

	struct bpf_prog *prog;

	int ret = 0;



	ctx.meta = &meta;

	ctx.link = v;

	meta.seq = seq;

	prog = bpf_iter_get_info(&meta, in_stop);

	if (prog)

		ret = bpf_iter_run_prog(prog, &ctx);



	return ret;

}



static int bpf_link_seq_show(struct seq_file *seq, void *v)

{

	return __bpf_link_seq_show(seq, v, false);

}



static void bpf_link_seq_stop(struct seq_file *seq, void *v)

{

	if (!v)

		(void)__bpf_link_seq_show(seq, v, true);

	else

		bpf_link_put((struct bpf_link *)v);

}



static const struct seq_operations bpf_link_seq_ops = {

	.start	= bpf_link_seq_start,

	.next	= bpf_link_seq_next,

	.stop	= bpf_link_seq_stop,

	.show	= bpf_link_seq_show,

};



BTF_ID_LIST(btf_bpf_link_id)

BTF_ID(struct, bpf_link)



static const struct bpf_iter_seq_info bpf_link_seq_info = {

	.seq_ops		= &bpf_link_seq_ops,

	.init_seq_private	= NULL,

	.fini_seq_private	= NULL,

	.seq_priv_size		= sizeof(struct bpf_iter_seq_link_info),

};



static struct bpf_iter_reg bpf_link_reg_info = {

	.target			= "bpf_link",

	.ctx_arg_info_size	= 1,

	.ctx_arg_info		= {

		{ offsetof(struct bpf_iter__bpf_link, link),

		  PTR_TO_BTF_ID_OR_NULL },

	},

	.seq_info		= &bpf_link_seq_info,

};



static int __init bpf_link_iter_init(void)

{

	bpf_link_reg_info.ctx_arg_info[0].btf_id = *btf_bpf_link_id;

	return bpf_iter_reg_target(&bpf_link_reg_info);

}



late_initcall(bpf_link_iter_init);

kernel/bpf/syscall.c

+19 −0
Original line number Diff line number Diff line
@@ -4680,6 +4680,25 @@ struct bpf_link *bpf_link_by_id(u32 id) 
	return link;

}



struct bpf_link *bpf_link_get_curr_or_next(u32 *id)

{

	struct bpf_link *link;



	spin_lock_bh(&link_idr_lock);

again:

	link = idr_get_next(&link_idr, id);

	if (link) {

		link = bpf_link_inc_not_zero(link);

		if (IS_ERR(link)) {

			(*id)++;

			goto again;

		}

	}

	spin_unlock_bh(&link_idr_lock);



	return link;

}



#define BPF_LINK_GET_FD_BY_ID_LAST_FIELD link_id



static int bpf_link_get_fd_by_id(const union bpf_attr *attr)