Commit eaaacd23 authored by Yonghong Song's avatar Yonghong Song Committed by Alexei Starovoitov
Browse files

bpf: Add task and task/file iterator targets 



Only the tasks belonging to "current" pid namespace
are enumerated.

For task/file target, the bpf program will have access to
  struct task_struct *task
  u32 fd
  struct file *file
where fd/file is an open file for the task.

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/20200509175911.2476407-1-yhs@fb.com
parent 138d0be3

kernel/bpf/Makefile

+1 −1
Original line number Diff line number Diff line
@@ -2,7 +2,7 @@ 
obj-y := core.o

CFLAGS_core.o += $(call cc-disable-warning, override-init)



obj-$(CONFIG_BPF_SYSCALL) += syscall.o verifier.o inode.o helpers.o tnum.o bpf_iter.o map_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

obj-$(CONFIG_BPF_SYSCALL) += hashtab.o arraymap.o percpu_freelist.o bpf_lru_list.o lpm_trie.o map_in_map.o

obj-$(CONFIG_BPF_SYSCALL) += local_storage.o queue_stack_maps.o

obj-$(CONFIG_BPF_SYSCALL) += disasm.o

kernel/bpf/task_iter.c

0 → 100644
+333 −0
Original line number Diff line number Diff line 
// SPDX-License-Identifier: GPL-2.0-only

/* Copyright (c) 2020 Facebook */



#include <linux/init.h>

#include <linux/namei.h>

#include <linux/pid_namespace.h>

#include <linux/fs.h>

#include <linux/fdtable.h>

#include <linux/filter.h>



struct bpf_iter_seq_task_common {

	struct pid_namespace *ns;

};



struct bpf_iter_seq_task_info {

	/* The first field must be struct bpf_iter_seq_task_common.

	 * this is assumed by {init, fini}_seq_pidns() callback functions.

	 */

	struct bpf_iter_seq_task_common common;

	u32 tid;

};



static struct task_struct *task_seq_get_next(struct pid_namespace *ns,

					     u32 *tid)

{

	struct task_struct *task = NULL;

	struct pid *pid;



	rcu_read_lock();

	pid = idr_get_next(&ns->idr, tid);

	if (pid)

		task = get_pid_task(pid, PIDTYPE_PID);

	rcu_read_unlock();



	return task;

}



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

{

	struct bpf_iter_seq_task_info *info = seq->private;

	struct task_struct *task;



	task = task_seq_get_next(info->common.ns, &info->tid);

	if (!task)

		return NULL;



	++*pos;

	return task;

}



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

{

	struct bpf_iter_seq_task_info *info = seq->private;

	struct task_struct *task;



	++*pos;

	++info->tid;

	put_task_struct((struct task_struct *)v);

	task = task_seq_get_next(info->common.ns, &info->tid);

	if (!task)

		return NULL;



	return task;

}



struct bpf_iter__task {

	__bpf_md_ptr(struct bpf_iter_meta *, meta);

	__bpf_md_ptr(struct task_struct *, task);

};



DEFINE_BPF_ITER_FUNC(task, struct bpf_iter_meta *meta, struct task_struct *task)



static int __task_seq_show(struct seq_file *seq, struct task_struct *task,

			   bool in_stop)

{

	struct bpf_iter_meta meta;

	struct bpf_iter__task ctx;

	struct bpf_prog *prog;



	meta.seq = seq;

	prog = bpf_iter_get_info(&meta, in_stop);

	if (!prog)

		return 0;



	meta.seq = seq;

	ctx.meta = &meta;

	ctx.task = task;

	return bpf_iter_run_prog(prog, &ctx);

}



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

{

	return __task_seq_show(seq, v, false);

}



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

{

	if (!v)

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

	else

		put_task_struct((struct task_struct *)v);

}



static const struct seq_operations task_seq_ops = {

	.start	= task_seq_start,

	.next	= task_seq_next,

	.stop	= task_seq_stop,

	.show	= task_seq_show,

};



struct bpf_iter_seq_task_file_info {

	/* The first field must be struct bpf_iter_seq_task_common.

	 * this is assumed by {init, fini}_seq_pidns() callback functions.

	 */

	struct bpf_iter_seq_task_common common;

	struct task_struct *task;

	struct files_struct *files;

	u32 tid;

	u32 fd;

};



static struct file *

task_file_seq_get_next(struct bpf_iter_seq_task_file_info *info,

		       struct task_struct **task, struct files_struct **fstruct)

{

	struct pid_namespace *ns = info->common.ns;

	u32 curr_tid = info->tid, max_fds;

	struct files_struct *curr_files;

	struct task_struct *curr_task;

	int curr_fd = info->fd;



	/* If this function returns a non-NULL file object,

	 * it held a reference to the task/files_struct/file.

	 * Otherwise, it does not hold any reference.

	 */

again:

	if (*task) {

		curr_task = *task;

		curr_files = *fstruct;

		curr_fd = info->fd;

	} else {

		curr_task = task_seq_get_next(ns, &curr_tid);

		if (!curr_task)

			return NULL;



		curr_files = get_files_struct(curr_task);

		if (!curr_files) {

			put_task_struct(curr_task);

			curr_tid = ++(info->tid);

			info->fd = 0;

			goto again;

		}



		/* set *fstruct, *task and info->tid */

		*fstruct = curr_files;

		*task = curr_task;

		if (curr_tid == info->tid) {

			curr_fd = info->fd;

		} else {

			info->tid = curr_tid;

			curr_fd = 0;

		}

	}



	rcu_read_lock();

	max_fds = files_fdtable(curr_files)->max_fds;

	for (; curr_fd < max_fds; curr_fd++) {

		struct file *f;



		f = fcheck_files(curr_files, curr_fd);

		if (!f)

			continue;



		/* set info->fd */

		info->fd = curr_fd;

		get_file(f);

		rcu_read_unlock();

		return f;

	}



	/* the current task is done, go to the next task */

	rcu_read_unlock();

	put_files_struct(curr_files);

	put_task_struct(curr_task);

	*task = NULL;

	*fstruct = NULL;

	info->fd = 0;

	curr_tid = ++(info->tid);

	goto again;

}



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

{

	struct bpf_iter_seq_task_file_info *info = seq->private;

	struct files_struct *files = NULL;

	struct task_struct *task = NULL;

	struct file *file;



	file = task_file_seq_get_next(info, &task, &files);

	if (!file) {

		info->files = NULL;

		info->task = NULL;

		return NULL;

	}



	++*pos;

	info->task = task;

	info->files = files;



	return file;

}



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

{

	struct bpf_iter_seq_task_file_info *info = seq->private;

	struct files_struct *files = info->files;

	struct task_struct *task = info->task;

	struct file *file;



	++*pos;

	++info->fd;

	fput((struct file *)v);

	file = task_file_seq_get_next(info, &task, &files);

	if (!file) {

		info->files = NULL;

		info->task = NULL;

		return NULL;

	}



	info->task = task;

	info->files = files;



	return file;

}



struct bpf_iter__task_file {

	__bpf_md_ptr(struct bpf_iter_meta *, meta);

	__bpf_md_ptr(struct task_struct *, task);

	u32 fd __aligned(8);

	__bpf_md_ptr(struct file *, file);

};



DEFINE_BPF_ITER_FUNC(task_file, struct bpf_iter_meta *meta,

		     struct task_struct *task, u32 fd,

		     struct file *file)



static int __task_file_seq_show(struct seq_file *seq, struct file *file,

				bool in_stop)

{

	struct bpf_iter_seq_task_file_info *info = seq->private;

	struct bpf_iter__task_file ctx;

	struct bpf_iter_meta meta;

	struct bpf_prog *prog;



	meta.seq = seq;

	prog = bpf_iter_get_info(&meta, in_stop);

	if (!prog)

		return 0;



	ctx.meta = &meta;

	ctx.task = info->task;

	ctx.fd = info->fd;

	ctx.file = file;

	return bpf_iter_run_prog(prog, &ctx);

}



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

{

	return __task_file_seq_show(seq, v, false);

}



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

{

	struct bpf_iter_seq_task_file_info *info = seq->private;



	if (!v) {

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

	} else {

		fput((struct file *)v);

		put_files_struct(info->files);

		put_task_struct(info->task);

		info->files = NULL;

		info->task = NULL;

	}

}



static int init_seq_pidns(void *priv_data)

{

	struct bpf_iter_seq_task_common *common = priv_data;



	common->ns = get_pid_ns(task_active_pid_ns(current));

	return 0;

}



static void fini_seq_pidns(void *priv_data)

{

	struct bpf_iter_seq_task_common *common = priv_data;



	put_pid_ns(common->ns);

}



static const struct seq_operations task_file_seq_ops = {

	.start	= task_file_seq_start,

	.next	= task_file_seq_next,

	.stop	= task_file_seq_stop,

	.show	= task_file_seq_show,

};



static int __init task_iter_init(void)

{

	struct bpf_iter_reg task_file_reg_info = {

		.target			= "task_file",

		.seq_ops		= &task_file_seq_ops,

		.init_seq_private	= init_seq_pidns,

		.fini_seq_private	= fini_seq_pidns,

		.seq_priv_size		= sizeof(struct bpf_iter_seq_task_file_info),

	};

	struct bpf_iter_reg task_reg_info = {

		.target			= "task",

		.seq_ops		= &task_seq_ops,

		.init_seq_private	= init_seq_pidns,

		.fini_seq_private	= fini_seq_pidns,

		.seq_priv_size		= sizeof(struct bpf_iter_seq_task_info),

	};

	int ret;



	ret = bpf_iter_reg_target(&task_reg_info);

	if (ret)

		return ret;



	return bpf_iter_reg_target(&task_file_reg_info);

}

late_initcall(task_iter_init);

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