tracefs: Add new tracefs file system

obj-$(CONFIG_HPPFS)		+= hppfs/

obj-$(CONFIG_CACHEFILES)	+= cachefiles/

obj-$(CONFIG_DEBUG_FS)		+= debugfs/

obj-$(CONFIG_TRACING)		+= tracefs/

obj-$(CONFIG_OCFS2_FS)		+= ocfs2/

obj-$(CONFIG_BTRFS_FS)		+= btrfs/

obj-$(CONFIG_GFS2_FS)           += gfs2/

tracefs-objs	:= inode.o

obj-$(CONFIG_TRACING)	+= tracefs.o

/*

 *  inode.c - part of tracefs, a pseudo file system for activating tracing

 *

 * Based on debugfs by: Greg Kroah-Hartman <greg@kroah.com>

 *

 *  Copyright (C) 2014 Red Hat Inc, author: Steven Rostedt <srostedt@redhat.com>

 *

 *	This program is free software; you can redistribute it and/or

 *	modify it under the terms of the GNU General Public License version

 *	2 as published by the Free Software Foundation.

 *

 * tracefs is the file system that is used by the tracing infrastructure.

 *

 */

#include <linux/module.h>

#include <linux/fs.h>

#include <linux/mount.h>

#include <linux/namei.h>

#include <linux/tracefs.h>

#include <linux/fsnotify.h>

#include <linux/seq_file.h>

#include <linux/parser.h>

#include <linux/magic.h>

#include <linux/slab.h>

#define TRACEFS_DEFAULT_MODE	0700

static struct vfsmount *tracefs_mount;

static int tracefs_mount_count;

static bool tracefs_registered;

static ssize_t default_read_file(struct file *file, char __user *buf,

				 size_t count, loff_t *ppos)

{

	return 0;

}

static ssize_t default_write_file(struct file *file, const char __user *buf,

				   size_t count, loff_t *ppos)

{

	return count;

}

static const struct file_operations tracefs_file_operations = {

	.read =		default_read_file,

	.write =	default_write_file,

	.open =		simple_open,

	.llseek =	noop_llseek,

};

static struct inode *tracefs_get_inode(struct super_block *sb)

{

	struct inode *inode = new_inode(sb);

	if (inode) {

		inode->i_ino = get_next_ino();

		inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;

	}

	return inode;

}

struct tracefs_mount_opts {

	kuid_t uid;

	kgid_t gid;

	umode_t mode;

};

enum {

	Opt_uid,

	Opt_gid,

	Opt_mode,

	Opt_err

};

static const match_table_t tokens = {

	{Opt_uid, "uid=%u"},

	{Opt_gid, "gid=%u"},

	{Opt_mode, "mode=%o"},

	{Opt_err, NULL}

};

struct tracefs_fs_info {

	struct tracefs_mount_opts mount_opts;

};

static int tracefs_parse_options(char *data, struct tracefs_mount_opts *opts)

{

	substring_t args[MAX_OPT_ARGS];

	int option;

	int token;

	kuid_t uid;

	kgid_t gid;

	char *p;

	opts->mode = TRACEFS_DEFAULT_MODE;

	while ((p = strsep(&data, ",")) != NULL) {

		if (!*p)

			continue;

		token = match_token(p, tokens, args);

		switch (token) {

		case Opt_uid:

			if (match_int(&args[0], &option))

				return -EINVAL;

			uid = make_kuid(current_user_ns(), option);

			if (!uid_valid(uid))

				return -EINVAL;

			opts->uid = uid;

			break;

		case Opt_gid:

			if (match_int(&args[0], &option))

				return -EINVAL;

			gid = make_kgid(current_user_ns(), option);

			if (!gid_valid(gid))

				return -EINVAL;

			opts->gid = gid;

			break;

		case Opt_mode:

			if (match_octal(&args[0], &option))

				return -EINVAL;

			opts->mode = option & S_IALLUGO;

			break;

		/*

		 * We might like to report bad mount options here;

		 * but traditionally tracefs has ignored all mount options

		 */

		}

	}

	return 0;

}

static int tracefs_apply_options(struct super_block *sb)

{

	struct tracefs_fs_info *fsi = sb->s_fs_info;

	struct inode *inode = sb->s_root->d_inode;

	struct tracefs_mount_opts *opts = &fsi->mount_opts;

	inode->i_mode &= ~S_IALLUGO;

	inode->i_mode |= opts->mode;

	inode->i_uid = opts->uid;

	inode->i_gid = opts->gid;

	return 0;

}

static int tracefs_remount(struct super_block *sb, int *flags, char *data)

{

	int err;

	struct tracefs_fs_info *fsi = sb->s_fs_info;

	sync_filesystem(sb);

	err = tracefs_parse_options(data, &fsi->mount_opts);

	if (err)

		goto fail;

	tracefs_apply_options(sb);

fail:

	return err;

}

static int tracefs_show_options(struct seq_file *m, struct dentry *root)

{

	struct tracefs_fs_info *fsi = root->d_sb->s_fs_info;

	struct tracefs_mount_opts *opts = &fsi->mount_opts;

	if (!uid_eq(opts->uid, GLOBAL_ROOT_UID))

		seq_printf(m, ",uid=%u",

			   from_kuid_munged(&init_user_ns, opts->uid));

	if (!gid_eq(opts->gid, GLOBAL_ROOT_GID))

		seq_printf(m, ",gid=%u",

			   from_kgid_munged(&init_user_ns, opts->gid));

	if (opts->mode != TRACEFS_DEFAULT_MODE)

		seq_printf(m, ",mode=%o", opts->mode);

	return 0;

}

static const struct super_operations tracefs_super_operations = {

	.statfs		= simple_statfs,

	.remount_fs	= tracefs_remount,

	.show_options	= tracefs_show_options,

};

static int trace_fill_super(struct super_block *sb, void *data, int silent)

{

	static struct tree_descr trace_files[] = {{""}};

	struct tracefs_fs_info *fsi;

	int err;

	save_mount_options(sb, data);

	fsi = kzalloc(sizeof(struct tracefs_fs_info), GFP_KERNEL);

	sb->s_fs_info = fsi;

	if (!fsi) {

		err = -ENOMEM;

		goto fail;

	}

	err = tracefs_parse_options(data, &fsi->mount_opts);

	if (err)

		goto fail;

	err  =  simple_fill_super(sb, TRACEFS_MAGIC, trace_files);

	if (err)

		goto fail;

	sb->s_op = &tracefs_super_operations;

	tracefs_apply_options(sb);

	return 0;

fail:

	kfree(fsi);

	sb->s_fs_info = NULL;

	return err;

}

static struct dentry *trace_mount(struct file_system_type *fs_type,

			int flags, const char *dev_name,

			void *data)

{

	return mount_single(fs_type, flags, data, trace_fill_super);

}

static struct file_system_type trace_fs_type = {

	.owner =	THIS_MODULE,

	.name =		"tracefs",

	.mount =	trace_mount,

	.kill_sb =	kill_litter_super,

};

MODULE_ALIAS_FS("tracefs");

static struct dentry *start_creating(const char *name, struct dentry *parent)

{

	struct dentry *dentry;

	int error;

	pr_debug("tracefs: creating file '%s'\n",name);

	error = simple_pin_fs(&trace_fs_type, &tracefs_mount,

			      &tracefs_mount_count);

	if (error)

		return ERR_PTR(error);

	/* If the parent is not specified, we create it in the root.

	 * We need the root dentry to do this, which is in the super

	 * block. A pointer to that is in the struct vfsmount that we

	 * have around.

	 */

	if (!parent)

		parent = tracefs_mount->mnt_root;

	mutex_lock(&parent->d_inode->i_mutex);

	dentry = lookup_one_len(name, parent, strlen(name));

	if (!IS_ERR(dentry) && dentry->d_inode) {

		dput(dentry);

		dentry = ERR_PTR(-EEXIST);

	}

	if (IS_ERR(dentry))

		mutex_unlock(&parent->d_inode->i_mutex);

	return dentry;

}

static struct dentry *failed_creating(struct dentry *dentry)

{

	mutex_unlock(&dentry->d_parent->d_inode->i_mutex);

	dput(dentry);

	simple_release_fs(&tracefs_mount, &tracefs_mount_count);

	return NULL;

}

static struct dentry *end_creating(struct dentry *dentry)

{

	mutex_unlock(&dentry->d_parent->d_inode->i_mutex);

	return dentry;

}

/**

 * tracefs_create_file - create a file in the tracefs filesystem

 * @name: a pointer to a string containing the name of the file to create.

 * @mode: the permission that the file should have.

 * @parent: a pointer to the parent dentry for this file.  This should be a

 *          directory dentry if set.  If this parameter is NULL, then the

 *          file will be created in the root of the tracefs filesystem.

 * @data: a pointer to something that the caller will want to get to later

 *        on.  The inode.i_private pointer will point to this value on

 *        the open() call.

 * @fops: a pointer to a struct file_operations that should be used for

 *        this file.

 *

 * This is the basic "create a file" function for tracefs.  It allows for a

 * wide range of flexibility in creating a file, or a directory (if you want

 * to create a directory, the tracefs_create_dir() function is

 * recommended to be used instead.)

 *

 * This function will return a pointer to a dentry if it succeeds.  This

 * pointer must be passed to the tracefs_remove() function when the file is

 * to be removed (no automatic cleanup happens if your module is unloaded,

 * you are responsible here.)  If an error occurs, %NULL will be returned.

 *

 * If tracefs is not enabled in the kernel, the value -%ENODEV will be

 * returned.

 */

struct dentry *tracefs_create_file(const char *name, umode_t mode,

				   struct dentry *parent, void *data,

				   const struct file_operations *fops)

{

	struct dentry *dentry;

	struct inode *inode;

	if (!(mode & S_IFMT))

		mode |= S_IFREG;

	BUG_ON(!S_ISREG(mode));

	dentry = start_creating(name, parent);

	if (IS_ERR(dentry))

		return NULL;

	inode = tracefs_get_inode(dentry->d_sb);

	if (unlikely(!inode))

		return failed_creating(dentry);

	inode->i_mode = mode;

	inode->i_fop = fops ? fops : &tracefs_file_operations;

	inode->i_private = data;

	d_instantiate(dentry, inode);

	fsnotify_create(dentry->d_parent->d_inode, dentry);

	return end_creating(dentry);

}

/**

 * tracefs_create_dir - create a directory in the tracefs filesystem

 * @name: a pointer to a string containing the name of the directory to

 *        create.

 * @parent: a pointer to the parent dentry for this file.  This should be a

 *          directory dentry if set.  If this parameter is NULL, then the

 *          directory will be created in the root of the tracefs filesystem.

 *

 * This function creates a directory in tracefs with the given name.

 *

 * This function will return a pointer to a dentry if it succeeds.  This

 * pointer must be passed to the tracefs_remove() function when the file is

 * to be removed. If an error occurs, %NULL will be returned.

 *

 * If tracing is not enabled in the kernel, the value -%ENODEV will be

 * returned.

 */

struct dentry *tracefs_create_dir(const char *name, struct dentry *parent)

{

	struct dentry *dentry = start_creating(name, parent);

	struct inode *inode;

	if (IS_ERR(dentry))

		return NULL;

	inode = tracefs_get_inode(dentry->d_sb);

	if (unlikely(!inode))

		return failed_creating(dentry);

	inode->i_mode = S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO;

	inode->i_op = &simple_dir_inode_operations;

	inode->i_fop = &simple_dir_operations;

	/* directory inodes start off with i_nlink == 2 (for "." entry) */

	inc_nlink(inode);

	d_instantiate(dentry, inode);

	inc_nlink(dentry->d_parent->d_inode);

	fsnotify_mkdir(dentry->d_parent->d_inode, dentry);

	return end_creating(dentry);

}

static inline int tracefs_positive(struct dentry *dentry)

{

	return dentry->d_inode && !d_unhashed(dentry);

}

static int __tracefs_remove(struct dentry *dentry, struct dentry *parent)

{

	int ret = 0;

	if (tracefs_positive(dentry)) {

		if (dentry->d_inode) {

			dget(dentry);

			switch (dentry->d_inode->i_mode & S_IFMT) {

			case S_IFDIR:

				ret = simple_rmdir(parent->d_inode, dentry);

				break;

			default:

				simple_unlink(parent->d_inode, dentry);

				break;

			}

			if (!ret)

				d_delete(dentry);

			dput(dentry);

		}

	}

	return ret;

}

/**

 * tracefs_remove - removes a file or directory from the tracefs filesystem

 * @dentry: a pointer to a the dentry of the file or directory to be

 *          removed.

 *

 * This function removes a file or directory in tracefs that was previously

 * created with a call to another tracefs function (like

 * tracefs_create_file() or variants thereof.)

 */

void tracefs_remove(struct dentry *dentry)

{

	struct dentry *parent;

	int ret;

	if (IS_ERR_OR_NULL(dentry))

		return;

	parent = dentry->d_parent;

	if (!parent || !parent->d_inode)

		return;

	mutex_lock(&parent->d_inode->i_mutex);

	ret = __tracefs_remove(dentry, parent);

	mutex_unlock(&parent->d_inode->i_mutex);

	if (!ret)

		simple_release_fs(&tracefs_mount, &tracefs_mount_count);

}

/**

 * tracefs_remove_recursive - recursively removes a directory

 * @dentry: a pointer to a the dentry of the directory to be removed.

 *

 * This function recursively removes a directory tree in tracefs that

 * was previously created with a call to another tracefs function

 * (like tracefs_create_file() or variants thereof.)

 */

void tracefs_remove_recursive(struct dentry *dentry)

{

	struct dentry *child, *parent;

	if (IS_ERR_OR_NULL(dentry))

		return;

	parent = dentry->d_parent;

	if (!parent || !parent->d_inode)

		return;

	parent = dentry;

 down:

	mutex_lock(&parent->d_inode->i_mutex);

 loop:

	/*

	 * The parent->d_subdirs is protected by the d_lock. Outside that

	 * lock, the child can be unlinked and set to be freed which can

	 * use the d_u.d_child as the rcu head and corrupt this list.

	 */

	spin_lock(&parent->d_lock);

	list_for_each_entry(child, &parent->d_subdirs, d_child) {

		if (!tracefs_positive(child))

			continue;

		/* perhaps simple_empty(child) makes more sense */

		if (!list_empty(&child->d_subdirs)) {

			spin_unlock(&parent->d_lock);

			mutex_unlock(&parent->d_inode->i_mutex);

			parent = child;

			goto down;

		}

		spin_unlock(&parent->d_lock);

		if (!__tracefs_remove(child, parent))

			simple_release_fs(&tracefs_mount, &tracefs_mount_count);

		/*

		 * The parent->d_lock protects agaist child from unlinking

		 * from d_subdirs. When releasing the parent->d_lock we can

		 * no longer trust that the next pointer is valid.

		 * Restart the loop. We'll skip this one with the

		 * tracefs_positive() check.

		 */

		goto loop;

	}

	spin_unlock(&parent->d_lock);

	mutex_unlock(&parent->d_inode->i_mutex);

	child = parent;

	parent = parent->d_parent;

	mutex_lock(&parent->d_inode->i_mutex);

	if (child != dentry)

		/* go up */

		goto loop;

	if (!__tracefs_remove(child, parent))

		simple_release_fs(&tracefs_mount, &tracefs_mount_count);

	mutex_unlock(&parent->d_inode->i_mutex);

}

/**

 * tracefs_initialized - Tells whether tracefs has been registered

 */

bool tracefs_initialized(void)

{

	return tracefs_registered;

}

static int __init tracefs_init(void)

{

	int retval;

	retval = register_filesystem(&trace_fs_type);

	if (!retval)

		tracefs_registered = true;

	return retval;

}

core_initcall(tracefs_init);

/*

 *  tracefs.h - a pseudo file system for activating tracing

 *

 * Based on debugfs by: 2004 Greg Kroah-Hartman <greg@kroah.com>

 *

 *  Copyright (C) 2014 Red Hat Inc, author: Steven Rostedt <srostedt@redhat.com>

 *

 *	This program is free software; you can redistribute it and/or

 *	modify it under the terms of the GNU General Public License version

 *	2 as published by the Free Software Foundation.

 *

 * tracefs is the file system that is used by the tracing infrastructure.

 *

 */

#ifndef _TRACEFS_H_

#define _TRACEFS_H_

#include <linux/fs.h>

#include <linux/seq_file.h>

#include <linux/types.h>

struct file_operations;

#ifdef CONFIG_TRACING

struct dentry *tracefs_create_file(const char *name, umode_t mode,

				   struct dentry *parent, void *data,

				   const struct file_operations *fops);

struct dentry *tracefs_create_dir(const char *name, struct dentry *parent);

void tracefs_remove(struct dentry *dentry);

void tracefs_remove_recursive(struct dentry *dentry);

bool tracefs_initialized(void);

#endif /* CONFIG_TRACING */

#endif

#define STACK_END_MAGIC		0x57AC6E9D

#define TRACEFS_MAGIC          0x74726163

#define V9FS_MAGIC		0x01021997

#define BDEVFS_MAGIC            0x62646576