Commit ac51d99b authored by Yonghong Song's avatar Yonghong Song Committed by Alexei Starovoitov
Browse files

bpf: Create anonymous bpf iterator 



A new bpf command BPF_ITER_CREATE is added.

The anonymous bpf iterator is seq_file based.
The seq_file private data are referenced by targets.
The bpf_iter infrastructure allocated additional space
at seq_file->private before the space used by targets
to store some meta data, e.g.,
  prog:       prog to run
  session_id: an unique id for each opened seq_file
  seq_num:    how many times bpf programs are queried in this session
  done_stop:  an internal state to decide whether bpf program
              should be called in seq_ops->stop() or not

The seq_num will start from 0 for valid objects.
The bpf program may see the same seq_num more than once if
 - seq_file buffer overflow happens and the same object
   is retried by bpf_seq_read(), or
 - the bpf program explicitly requests a retry of the
   same object

Since module is not supported for bpf_iter, all target
registeration happens at __init time, so there is no
need to change bpf_iter_unreg_target() as it is used
mostly in error path of the init function at which time
no bpf iterators have been created yet.

Signed-off-by: default avatarYonghong Song <yhs@fb.com>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Acked-by: default avatarAndrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/20200509175905.2475770-1-yhs@fb.com
parent fd4f12bc

include/linux/bpf.h

+1 −0
Original line number Original line Diff line number Diff line
@@ -1144,6 +1144,7 @@ int bpf_iter_reg_target(struct bpf_iter_reg *reg_info); 
void bpf_iter_unreg_target(const char *target);

void bpf_iter_unreg_target(const char *target);

bool bpf_iter_prog_supported(struct bpf_prog *prog);

bool bpf_iter_prog_supported(struct bpf_prog *prog);

int bpf_iter_link_attach(const union bpf_attr *attr, struct bpf_prog *prog);

int bpf_iter_link_attach(const union bpf_attr *attr, struct bpf_prog *prog);

int bpf_iter_new_fd(struct bpf_link *link);





int bpf_percpu_hash_copy(struct bpf_map *map, void *key, void *value);

int bpf_percpu_hash_copy(struct bpf_map *map, void *key, void *value);

int bpf_percpu_array_copy(struct bpf_map *map, void *key, void *value);

int bpf_percpu_array_copy(struct bpf_map *map, void *key, void *value);

include/uapi/linux/bpf.h

+6 −0
Original line number Original line Diff line number Diff line
@@ -116,6 +116,7 @@ enum bpf_cmd { 
	BPF_LINK_GET_FD_BY_ID,

	BPF_LINK_GET_FD_BY_ID,

	BPF_LINK_GET_NEXT_ID,

	BPF_LINK_GET_NEXT_ID,

	BPF_ENABLE_STATS,

	BPF_ENABLE_STATS,

	BPF_ITER_CREATE,

};

};





enum bpf_map_type {

enum bpf_map_type {
@@ -614,6 +615,11 @@ union bpf_attr { 
		__u32		type;

		__u32		type;

	} enable_stats;

	} enable_stats;





	struct { /* struct used by BPF_ITER_CREATE command */

		__u32		link_fd;

		__u32		flags;

	} iter_create;



} __attribute__((aligned(8)));

} __attribute__((aligned(8)));





/* The description below is an attempt at providing documentation to eBPF

/* The description below is an attempt at providing documentation to eBPF

kernel/bpf/bpf_iter.c

+129 −0
Original line number Original line Diff line number Diff line
@@ -2,6 +2,7 @@ 
/* Copyright (c) 2020 Facebook */

/* Copyright (c) 2020 Facebook */





#include <linux/fs.h>

#include <linux/fs.h>

#include <linux/anon_inodes.h>

#include <linux/filter.h>

#include <linux/filter.h>

#include <linux/bpf.h>

#include <linux/bpf.h>
@@ -20,12 +21,24 @@ struct bpf_iter_link { 
	struct bpf_iter_target_info *tinfo;

	struct bpf_iter_target_info *tinfo;

};

};





struct bpf_iter_priv_data {

	struct bpf_iter_target_info *tinfo;

	struct bpf_prog *prog;

	u64 session_id;

	u64 seq_num;

	bool done_stop;

	u8 target_private[] __aligned(8);

};



static struct list_head targets = LIST_HEAD_INIT(targets);

static struct list_head targets = LIST_HEAD_INIT(targets);

static DEFINE_MUTEX(targets_mutex);

static DEFINE_MUTEX(targets_mutex);





/* protect bpf_iter_link changes */

/* protect bpf_iter_link changes */

static DEFINE_MUTEX(link_mutex);

static DEFINE_MUTEX(link_mutex);





/* incremented on every opened seq_file */

static atomic64_t session_id;



/* bpf_seq_read, a customized and simpler version for bpf iterator.

/* bpf_seq_read, a customized and simpler version for bpf iterator.

 * no_llseek is assumed for this file.

 * no_llseek is assumed for this file.

 * The following are differences from seq_read():

 * The following are differences from seq_read():
@@ -149,6 +162,33 @@ done: 
	return copied;

	return copied;

}

}





static int iter_release(struct inode *inode, struct file *file)

{

	struct bpf_iter_priv_data *iter_priv;

	struct seq_file *seq;



	seq = file->private_data;

	if (!seq)

		return 0;



	iter_priv = container_of(seq->private, struct bpf_iter_priv_data,

				 target_private);



	if (iter_priv->tinfo->fini_seq_private)

		iter_priv->tinfo->fini_seq_private(seq->private);



	bpf_prog_put(iter_priv->prog);

	seq->private = iter_priv;



	return seq_release_private(inode, file);

}



static const struct file_operations bpf_iter_fops = {

	.llseek		= no_llseek,

	.read		= bpf_seq_read,

	.release	= iter_release,

};



int bpf_iter_reg_target(struct bpf_iter_reg *reg_info)

int bpf_iter_reg_target(struct bpf_iter_reg *reg_info)

{

{

	struct bpf_iter_target_info *tinfo;

	struct bpf_iter_target_info *tinfo;
@@ -309,3 +349,92 @@ int bpf_iter_link_attach(const union bpf_attr *attr, struct bpf_prog *prog) 




	return bpf_link_settle(&link_primer);

	return bpf_link_settle(&link_primer);

}

}



static void init_seq_meta(struct bpf_iter_priv_data *priv_data,

			  struct bpf_iter_target_info *tinfo,

			  struct bpf_prog *prog)

{

	priv_data->tinfo = tinfo;

	priv_data->prog = prog;

	priv_data->session_id = atomic64_inc_return(&session_id);

	priv_data->seq_num = 0;

	priv_data->done_stop = false;

}



static int prepare_seq_file(struct file *file, struct bpf_iter_link *link)

{

	struct bpf_iter_priv_data *priv_data;

	struct bpf_iter_target_info *tinfo;

	struct bpf_prog *prog;

	u32 total_priv_dsize;

	struct seq_file *seq;

	int err = 0;



	mutex_lock(&link_mutex);

	prog = link->link.prog;

	bpf_prog_inc(prog);

	mutex_unlock(&link_mutex);



	tinfo = link->tinfo;

	total_priv_dsize = offsetof(struct bpf_iter_priv_data, target_private) +

			   tinfo->seq_priv_size;

	priv_data = __seq_open_private(file, tinfo->seq_ops, total_priv_dsize);

	if (!priv_data) {

		err = -ENOMEM;

		goto release_prog;

	}



	if (tinfo->init_seq_private) {

		err = tinfo->init_seq_private(priv_data->target_private);

		if (err)

			goto release_seq_file;

	}



	init_seq_meta(priv_data, tinfo, prog);

	seq = file->private_data;

	seq->private = priv_data->target_private;



	return 0;



release_seq_file:

	seq_release_private(file->f_inode, file);

	file->private_data = NULL;

release_prog:

	bpf_prog_put(prog);

	return err;

}



int bpf_iter_new_fd(struct bpf_link *link)

{

	struct file *file;

	unsigned int flags;

	int err, fd;



	if (link->ops != &bpf_iter_link_lops)

		return -EINVAL;



	flags = O_RDONLY | O_CLOEXEC;

	fd = get_unused_fd_flags(flags);

	if (fd < 0)

		return fd;



	file = anon_inode_getfile("bpf_iter", &bpf_iter_fops, NULL, flags);

	if (IS_ERR(file)) {

		err = PTR_ERR(file);

		goto free_fd;

	}



	err = prepare_seq_file(file,

			       container_of(link, struct bpf_iter_link, link));

	if (err)

		goto free_file;



	fd_install(fd, file);

	return fd;



free_file:

	fput(file);

free_fd:

	put_unused_fd(fd);

	return err;

}

kernel/bpf/syscall.c

+26 −0
Original line number Original line Diff line number Diff line
@@ -3941,6 +3941,29 @@ static int bpf_enable_stats(union bpf_attr *attr) 
	return -EINVAL;

	return -EINVAL;

}

}





#define BPF_ITER_CREATE_LAST_FIELD iter_create.flags



static int bpf_iter_create(union bpf_attr *attr)

{

	struct bpf_link *link;

	int err;



	if (CHECK_ATTR(BPF_ITER_CREATE))

		return -EINVAL;



	if (attr->iter_create.flags)

		return -EINVAL;



	link = bpf_link_get_from_fd(attr->iter_create.link_fd);

	if (IS_ERR(link))

		return PTR_ERR(link);



	err = bpf_iter_new_fd(link);

	bpf_link_put(link);



	return err;

}



SYSCALL_DEFINE3(bpf, int, cmd, union bpf_attr __user *, uattr, unsigned int, size)

SYSCALL_DEFINE3(bpf, int, cmd, union bpf_attr __user *, uattr, unsigned int, size)

{

{

	union bpf_attr attr;

	union bpf_attr attr;
@@ -4068,6 +4091,9 @@ SYSCALL_DEFINE3(bpf, int, cmd, union bpf_attr __user *, uattr, unsigned int, siz 
	case BPF_ENABLE_STATS:

	case BPF_ENABLE_STATS:

		err = bpf_enable_stats(&attr);

		err = bpf_enable_stats(&attr);

		break;

		break;

	case BPF_ITER_CREATE:

		err = bpf_iter_create(&attr);

		break;

	default:

	default:

		err = -EINVAL;

		err = -EINVAL;

		break;

		break;

tools/include/uapi/linux/bpf.h

+6 −0
Original line number Original line Diff line number Diff line
@@ -116,6 +116,7 @@ enum bpf_cmd { 
	BPF_LINK_GET_FD_BY_ID,

	BPF_LINK_GET_FD_BY_ID,

	BPF_LINK_GET_NEXT_ID,

	BPF_LINK_GET_NEXT_ID,

	BPF_ENABLE_STATS,

	BPF_ENABLE_STATS,

	BPF_ITER_CREATE,

};

};





enum bpf_map_type {

enum bpf_map_type {
@@ -614,6 +615,11 @@ union bpf_attr { 
		__u32		type;

		__u32		type;

	} enable_stats;

	} enable_stats;





	struct { /* struct used by BPF_ITER_CREATE command */

		__u32		link_fd;

		__u32		flags;

	} iter_create;



} __attribute__((aligned(8)));

} __attribute__((aligned(8)));





/* The description below is an attempt at providing documentation to eBPF

/* The description below is an attempt at providing documentation to eBPF

CRA Git | Maintained and supported by SUSTech CRA and CCSE