[mirror_ubuntu-jammy-kernel.git] / fs / tracefs / inode.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 *  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>
 *
 * 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/kobject.h>
#include <linux/namei.h>
#include <linux/tracefs.h>
#include <linux/fsnotify.h>
#include <linux/security.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 tracefs_dir_ops {
	int (*mkdir)(const char *name);
	int (*rmdir)(const char *name);
} tracefs_ops __ro_after_init;

static char *get_dname(struct dentry *dentry)
{
	const char *dname;
	char *name;
	int len = dentry->d_name.len;

	dname = dentry->d_name.name;
	name = kmalloc(len + 1, GFP_KERNEL);
	if (!name)
		return NULL;
	memcpy(name, dname, len);
	name[len] = 0;
	return name;
}

static int tracefs_syscall_mkdir(struct inode *inode, struct dentry *dentry, umode_t mode)
{
	char *name;
	int ret;

	name = get_dname(dentry);
	if (!name)
		return -ENOMEM;

	/*
	 * The mkdir call can call the generic functions that create
	 * the files within the tracefs system. It is up to the individual
	 * mkdir routine to handle races.
	 */
	inode_unlock(inode);
	ret = tracefs_ops.mkdir(name);
	inode_lock(inode);

	kfree(name);

	return ret;
}

static int tracefs_syscall_rmdir(struct inode *inode, struct dentry *dentry)
{
	char *name;
	int ret;

	name = get_dname(dentry);
	if (!name)
		return -ENOMEM;

	/*
	 * The rmdir call can call the generic functions that create
	 * the files within the tracefs system. It is up to the individual
	 * rmdir routine to handle races.
	 * This time we need to unlock not only the parent (inode) but
	 * also the directory that is being deleted.
	 */
	inode_unlock(inode);
	inode_unlock(dentry->d_inode);

	ret = tracefs_ops.rmdir(name);

	inode_lock_nested(inode, I_MUTEX_PARENT);
	inode_lock(dentry->d_inode);

	kfree(name);

	return ret;
}

static const struct inode_operations tracefs_dir_inode_operations = {
	.lookup		= simple_lookup,
	.mkdir		= tracefs_syscall_mkdir,
	.rmdir		= tracefs_syscall_rmdir,
};

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(inode);
	}
	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 const struct tree_descr trace_files[] = {{""}};
	struct tracefs_fs_info *fsi;
	int err;

	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;

	inode_lock(parent->d_inode);
	if (unlikely(IS_DEADDIR(parent->d_inode)))
		dentry = ERR_PTR(-ENOENT);
	else
		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)) {
		inode_unlock(parent->d_inode);
		simple_release_fs(&tracefs_mount, &tracefs_mount_count);
	}

	return dentry;
}

static struct dentry *failed_creating(struct dentry *dentry)
{
	inode_unlock(dentry->d_parent->d_inode);
	dput(dentry);
	simple_release_fs(&tracefs_mount, &tracefs_mount_count);
	return NULL;
}

static struct dentry *end_creating(struct dentry *dentry)
{
	inode_unlock(dentry->d_parent->d_inode);
	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 (security_locked_down(LOCKDOWN_TRACEFS))
		return NULL;

	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);
}

static struct dentry *__create_dir(const char *name, struct dentry *parent,
				   const struct inode_operations *ops)
{
	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 = ops;
	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);
}

/**
 * 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)
{
	return __create_dir(name, parent, &simple_dir_inode_operations);
}

/**
 * tracefs_create_instance_dir - create the tracing instances directory
 * @name: The name of the instances directory to create
 * @parent: The parent directory that the instances directory will exist
 * @mkdir: The function to call when a mkdir is performed.
 * @rmdir: The function to call when a rmdir is performed.
 *
 * Only one instances directory is allowed.
 *
 * The instances directory is special as it allows for mkdir and rmdir to
 * to be done by userspace. When a mkdir or rmdir is performed, the inode
 * locks are released and the methhods passed in (@mkdir and @rmdir) are
 * called without locks and with the name of the directory being created
 * within the instances directory.
 *
 * Returns the dentry of the instances directory.
 */
__init struct dentry *tracefs_create_instance_dir(const char *name,
					  struct dentry *parent,
					  int (*mkdir)(const char *name),
					  int (*rmdir)(const char *name))
{
	struct dentry *dentry;

	/* Only allow one instance of the instances directory. */
	if (WARN_ON(tracefs_ops.mkdir || tracefs_ops.rmdir))
		return NULL;

	dentry = __create_dir(name, parent, &tracefs_dir_inode_operations);
	if (!dentry)
		return NULL;

	tracefs_ops.mkdir = mkdir;
	tracefs_ops.rmdir = rmdir;

	return dentry;
}

static void remove_one(struct dentry *victim)
{
	simple_release_fs(&tracefs_mount, &tracefs_mount_count);
}

/**
 * tracefs_remove - 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(struct dentry *dentry)
{
	if (IS_ERR_OR_NULL(dentry))
		return;

	simple_pin_fs(&trace_fs_type, &tracefs_mount, &tracefs_mount_count);
	simple_recursive_removal(dentry, remove_one);
	simple_release_fs(&tracefs_mount, &tracefs_mount_count);
}

/**
 * tracefs_initialized - Tells whether tracefs has been registered
 */
bool tracefs_initialized(void)
{
	return tracefs_registered;
}

static int __init tracefs_init(void)
{
	int retval;

	retval = sysfs_create_mount_point(kernel_kobj, "tracing");
	if (retval)
		return -EINVAL;

	retval = register_filesystem(&trace_fs_type);
	if (!retval)
		tracefs_registered = true;

	return retval;
}
core_initcall(tracefs_init);
Commit	Line	Data
d2912cb1	1	// SPDX-License-Identifier: GPL-2.0-only
4282d606 SRRH	2	/*
	3	* inode.c - part of tracefs, a pseudo file system for activating tracing
	4	*
	5	* Based on debugfs by: Greg Kroah-Hartman <greg@kroah.com>
	6	*
	7	* Copyright (C) 2014 Red Hat Inc, author: Steven Rostedt <srostedt@redhat.com>
	8	*
4282d606	9	* tracefs is the file system that is used by the tracing infrastructure.
4282d606 SRRH	10	*/
	11
	12	#include <linux/module.h>
	13	#include <linux/fs.h>
	14	#include <linux/mount.h>
cc31004a	15	#include <linux/kobject.h>
4282d606 SRRH	16	#include <linux/namei.h>
	17	#include <linux/tracefs.h>
	18	#include <linux/fsnotify.h>
bf8e6021	19	#include <linux/security.h>
4282d606 SRRH	20	#include <linux/seq_file.h>
	21	#include <linux/parser.h>
	22	#include <linux/magic.h>
	23	#include <linux/slab.h>
	24
	25	#define TRACEFS_DEFAULT_MODE 0700
	26
	27	static struct vfsmount *tracefs_mount;
	28	static int tracefs_mount_count;
	29	static bool tracefs_registered;
	30
	31	static ssize_t default_read_file(struct file file, char __user buf,
	32	size_t count, loff_t *ppos)
	33	{
	34	return 0;
	35	}
	36
	37	static ssize_t default_write_file(struct file file, const char __user buf,
	38	size_t count, loff_t *ppos)
	39	{
	40	return count;
	41	}
	42
	43	static const struct file_operations tracefs_file_operations = {
	44	.read = default_read_file,
	45	.write = default_write_file,
	46	.open = simple_open,
	47	.llseek = noop_llseek,
	48	};
	49
eae47358 SRRH	50	static struct tracefs_dir_ops {
	51	int (mkdir)(const char name);
	52	int (rmdir)(const char name);
5248ee85	53	} tracefs_ops __ro_after_init;
eae47358 SRRH	54
	55	static char get_dname(struct dentry dentry)
	56	{
	57	const char *dname;
	58	char *name;
	59	int len = dentry->d_name.len;
	60
	61	dname = dentry->d_name.name;
	62	name = kmalloc(len + 1, GFP_KERNEL);
	63	if (!name)
	64	return NULL;
	65	memcpy(name, dname, len);
	66	name[len] = 0;
	67	return name;
	68	}
	69
	70	static int tracefs_syscall_mkdir(struct inode inode, struct dentry dentry, umode_t mode)
	71	{
	72	char *name;
	73	int ret;
	74
	75	name = get_dname(dentry);
	76	if (!name)
	77	return -ENOMEM;
	78
	79	/*
	80	* The mkdir call can call the generic functions that create
	81	* the files within the tracefs system. It is up to the individual
	82	* mkdir routine to handle races.
	83	*/
5955102c	84	inode_unlock(inode);
eae47358	85	ret = tracefs_ops.mkdir(name);
5955102c	86	inode_lock(inode);
eae47358 SRRH	87
	88	kfree(name);
	89
	90	return ret;
	91	}
	92
	93	static int tracefs_syscall_rmdir(struct inode inode, struct dentry dentry)
	94	{
	95	char *name;
	96	int ret;
	97
	98	name = get_dname(dentry);
	99	if (!name)
	100	return -ENOMEM;
	101
	102	/*
	103	* The rmdir call can call the generic functions that create
	104	* the files within the tracefs system. It is up to the individual
	105	* rmdir routine to handle races.
	106	* This time we need to unlock not only the parent (inode) but
	107	* also the directory that is being deleted.
	108	*/
5955102c AV	109	inode_unlock(inode);
5955102c AV	110	inode_unlock(dentry->d_inode);
eae47358 SRRH	111
	112	ret = tracefs_ops.rmdir(name);
	113
5955102c AV	114	inode_lock_nested(inode, I_MUTEX_PARENT);
5955102c AV	115	inode_lock(dentry->d_inode);
eae47358 SRRH	116
	117	kfree(name);
	118
	119	return ret;
	120	}
	121
	122	static const struct inode_operations tracefs_dir_inode_operations = {
	123	.lookup = simple_lookup,
	124	.mkdir = tracefs_syscall_mkdir,
	125	.rmdir = tracefs_syscall_rmdir,
	126	};
	127
4282d606 SRRH	128	static struct inode tracefs_get_inode(struct super_block sb)
	129	{
	130	struct inode *inode = new_inode(sb);
	131	if (inode) {
	132	inode->i_ino = get_next_ino();
078cd827	133	inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
4282d606 SRRH	134	}
	135	return inode;
	136	}
	137
	138	struct tracefs_mount_opts {
	139	kuid_t uid;
	140	kgid_t gid;
	141	umode_t mode;
	142	};
	143
	144	enum {
	145	Opt_uid,
	146	Opt_gid,
	147	Opt_mode,
	148	Opt_err
	149	};
	150
	151	static const match_table_t tokens = {
	152	{Opt_uid, "uid=%u"},
	153	{Opt_gid, "gid=%u"},
	154	{Opt_mode, "mode=%o"},
	155	{Opt_err, NULL}
	156	};
	157
	158	struct tracefs_fs_info {
	159	struct tracefs_mount_opts mount_opts;
	160	};
	161
	162	static int tracefs_parse_options(char data, struct tracefs_mount_opts opts)
	163	{
	164	substring_t args[MAX_OPT_ARGS];
	165	int option;
	166	int token;
	167	kuid_t uid;
	168	kgid_t gid;
	169	char *p;
	170
	171	opts->mode = TRACEFS_DEFAULT_MODE;
	172
	173	while ((p = strsep(&data, ",")) != NULL) {
	174	if (!*p)
	175	continue;
	176
	177	token = match_token(p, tokens, args);
	178	switch (token) {
	179	case Opt_uid:
	180	if (match_int(&args[0], &option))
	181	return -EINVAL;
	182	uid = make_kuid(current_user_ns(), option);
	183	if (!uid_valid(uid))
	184	return -EINVAL;
	185	opts->uid = uid;
	186	break;
	187	case Opt_gid:
	188	if (match_int(&args[0], &option))
	189	return -EINVAL;
	190	gid = make_kgid(current_user_ns(), option);
	191	if (!gid_valid(gid))
	192	return -EINVAL;
	193	opts->gid = gid;
	194	break;
	195	case Opt_mode:
	196	if (match_octal(&args[0], &option))
	197	return -EINVAL;
198	opts->mode = option & S_IALLUGO;
199	break;
200	/*
201	* We might like to report bad mount options here;
202	* but traditionally tracefs has ignored all mount options
203	*/
204	}
205	}
206
207	return 0;
208	}
209
210	static int tracefs_apply_options(struct super_block *sb)
211	{
212	struct tracefs_fs_info *fsi = sb->s_fs_info;
213	struct inode *inode = sb->s_root->d_inode;
214	struct tracefs_mount_opts *opts = &fsi->mount_opts;
215
216	inode->i_mode &= ~S_IALLUGO;
217	inode->i_mode \|= opts->mode;
218
219	inode->i_uid = opts->uid;
220	inode->i_gid = opts->gid;
221
222	return 0;
223	}
224
225	static int tracefs_remount(struct super_block sb, int flags, char *data)
226	{
227	int err;
228	struct tracefs_fs_info *fsi = sb->s_fs_info;
229
230	sync_filesystem(sb);
231	err = tracefs_parse_options(data, &fsi->mount_opts);
232	if (err)
233	goto fail;
234
235	tracefs_apply_options(sb);
236
237	fail:
238	return err;
239	}
240
241	static int tracefs_show_options(struct seq_file m, struct dentry root)
242	{
243	struct tracefs_fs_info *fsi = root->d_sb->s_fs_info;
244	struct tracefs_mount_opts *opts = &fsi->mount_opts;
245
246	if (!uid_eq(opts->uid, GLOBAL_ROOT_UID))
247	seq_printf(m, ",uid=%u",
248	from_kuid_munged(&init_user_ns, opts->uid));
249	if (!gid_eq(opts->gid, GLOBAL_ROOT_GID))
250	seq_printf(m, ",gid=%u",
251	from_kgid_munged(&init_user_ns, opts->gid));
252	if (opts->mode != TRACEFS_DEFAULT_MODE)
253	seq_printf(m, ",mode=%o", opts->mode);
254
255	return 0;
256	}
257
258	static const struct super_operations tracefs_super_operations = {
259	.statfs = simple_statfs,
260	.remount_fs = tracefs_remount,
261	.show_options = tracefs_show_options,
262	};
263
264	static int trace_fill_super(struct super_block sb, void data, int silent)
265	{
cda37124	266	static const struct tree_descr trace_files[] = {{""}};
4282d606 SRRH	267	struct tracefs_fs_info *fsi;
	268	int err;
	269
4282d606 SRRH	270	fsi = kzalloc(sizeof(struct tracefs_fs_info), GFP_KERNEL);
	271	sb->s_fs_info = fsi;
	272	if (!fsi) {
	273	err = -ENOMEM;
	274	goto fail;
	275	}
	276
	277	err = tracefs_parse_options(data, &fsi->mount_opts);
	278	if (err)
	279	goto fail;
	280
	281	err = simple_fill_super(sb, TRACEFS_MAGIC, trace_files);
	282	if (err)
	283	goto fail;
	284
	285	sb->s_op = &tracefs_super_operations;
	286
	287	tracefs_apply_options(sb);
	288
	289	return 0;
	290
	291	fail:
	292	kfree(fsi);
	293	sb->s_fs_info = NULL;
	294	return err;
	295	}
	296
	297	static struct dentry trace_mount(struct file_system_type fs_type,
	298	int flags, const char *dev_name,
	299	void *data)
	300	{
	301	return mount_single(fs_type, flags, data, trace_fill_super);
	302	}
	303
	304	static struct file_system_type trace_fs_type = {
	305	.owner = THIS_MODULE,
	306	.name = "tracefs",
	307	.mount = trace_mount,
	308	.kill_sb = kill_litter_super,
	309	};
	310	MODULE_ALIAS_FS("tracefs");
	311
	312	static struct dentry start_creating(const char name, struct dentry *parent)
	313	{
	314	struct dentry *dentry;
	315	int error;
	316
	317	pr_debug("tracefs: creating file '%s'\n",name);
	318
	319	error = simple_pin_fs(&trace_fs_type, &tracefs_mount,
	320	&tracefs_mount_count);
	321	if (error)
	322	return ERR_PTR(error);
	323
	324	/* If the parent is not specified, we create it in the root.
	325	* We need the root dentry to do this, which is in the super
	326	* block. A pointer to that is in the struct vfsmount that we
	327	* have around.
	328	*/
	329	if (!parent)
	330	parent = tracefs_mount->mnt_root;
	331
5955102c	332	inode_lock(parent->d_inode);
a3d1e7eb AV	333	if (unlikely(IS_DEADDIR(parent->d_inode)))
	334	dentry = ERR_PTR(-ENOENT);
	335	else
	336	dentry = lookup_one_len(name, parent, strlen(name));
4282d606 SRRH	337	if (!IS_ERR(dentry) && dentry->d_inode) {
	338	dput(dentry);
	339	dentry = ERR_PTR(-EEXIST);
	340	}
d227c3ae DB	341
d227c3ae DB	342	if (IS_ERR(dentry)) {
5955102c	343	inode_unlock(parent->d_inode);
d227c3ae DB	344	simple_release_fs(&tracefs_mount, &tracefs_mount_count);
	345	}
	346
4282d606 SRRH	347	return dentry;
	348	}
	349
	350	static struct dentry failed_creating(struct dentry dentry)
	351	{
5955102c	352	inode_unlock(dentry->d_parent->d_inode);
4282d606 SRRH	353	dput(dentry);
	354	simple_release_fs(&tracefs_mount, &tracefs_mount_count);
	355	return NULL;
	356	}
	357
	358	static struct dentry end_creating(struct dentry dentry)
	359	{
5955102c	360	inode_unlock(dentry->d_parent->d_inode);
4282d606 SRRH	361	return dentry;
	362	}
	363
	364	/**
	365	* tracefs_create_file - create a file in the tracefs filesystem
	366	* @name: a pointer to a string containing the name of the file to create.
	367	* @mode: the permission that the file should have.
	368	* @parent: a pointer to the parent dentry for this file. This should be a
	369	* directory dentry if set. If this parameter is NULL, then the
	370	* file will be created in the root of the tracefs filesystem.
	371	* @data: a pointer to something that the caller will want to get to later
	372	* on. The inode.i_private pointer will point to this value on
	373	* the open() call.
	374	* @fops: a pointer to a struct file_operations that should be used for
	375	* this file.
	376	*
	377	* This is the basic "create a file" function for tracefs. It allows for a
	378	* wide range of flexibility in creating a file, or a directory (if you want
	379	* to create a directory, the tracefs_create_dir() function is
	380	* recommended to be used instead.)
	381	*
	382	* This function will return a pointer to a dentry if it succeeds. This
	383	* pointer must be passed to the tracefs_remove() function when the file is
	384	* to be removed (no automatic cleanup happens if your module is unloaded,
	385	* you are responsible here.) If an error occurs, %NULL will be returned.
	386	*
	387	* If tracefs is not enabled in the kernel, the value -%ENODEV will be
	388	* returned.
	389	*/
	390	struct dentry tracefs_create_file(const char name, umode_t mode,
	391	struct dentry parent, void data,
	392	const struct file_operations *fops)
	393	{
	394	struct dentry *dentry;
	395	struct inode *inode;
	396
bf8e6021 SRV	397	if (security_locked_down(LOCKDOWN_TRACEFS))
	398	return NULL;
	399
4282d606 SRRH	400	if (!(mode & S_IFMT))
	401	mode \|= S_IFREG;
	402	BUG_ON(!S_ISREG(mode));
	403	dentry = start_creating(name, parent);
	404
	405	if (IS_ERR(dentry))
	406	return NULL;
	407
	408	inode = tracefs_get_inode(dentry->d_sb);
	409	if (unlikely(!inode))
	410	return failed_creating(dentry);
	411
	412	inode->i_mode = mode;
3ed270b1	413	inode->i_fop = fops ? fops : &tracefs_file_operations;
4282d606 SRRH	414	inode->i_private = data;
	415	d_instantiate(dentry, inode);
	416	fsnotify_create(dentry->d_parent->d_inode, dentry);
	417	return end_creating(dentry);
	418	}
	419
eae47358 SRRH	420	static struct dentry __create_dir(const char name, struct dentry *parent,
	421	const struct inode_operations *ops)
	422	{
	423	struct dentry *dentry = start_creating(name, parent);
	424	struct inode *inode;
	425
	426	if (IS_ERR(dentry))
	427	return NULL;
	428
	429	inode = tracefs_get_inode(dentry->d_sb);
	430	if (unlikely(!inode))
	431	return failed_creating(dentry);
	432
	433	inode->i_mode = S_IFDIR \| S_IRWXU \| S_IRUGO \| S_IXUGO;
	434	inode->i_op = ops;
	435	inode->i_fop = &simple_dir_operations;
	436
	437	/* directory inodes start off with i_nlink == 2 (for "." entry) */
	438	inc_nlink(inode);
	439	d_instantiate(dentry, inode);
	440	inc_nlink(dentry->d_parent->d_inode);
	441	fsnotify_mkdir(dentry->d_parent->d_inode, dentry);
	442	return end_creating(dentry);
	443	}
	444
4282d606 SRRH	445	/**
	446	* tracefs_create_dir - create a directory in the tracefs filesystem
	447	* @name: a pointer to a string containing the name of the directory to
	448	* create.
	449	* @parent: a pointer to the parent dentry for this file. This should be a
	450	* directory dentry if set. If this parameter is NULL, then the
	451	* directory will be created in the root of the tracefs filesystem.
	452	*
	453	* This function creates a directory in tracefs with the given name.
	454	*
	455	* This function will return a pointer to a dentry if it succeeds. This
	456	* pointer must be passed to the tracefs_remove() function when the file is
	457	* to be removed. If an error occurs, %NULL will be returned.
	458	*
	459	* If tracing is not enabled in the kernel, the value -%ENODEV will be
	460	* returned.
	461	*/
	462	struct dentry tracefs_create_dir(const char name, struct dentry *parent)
	463	{
eae47358 SRRH	464	return __create_dir(name, parent, &simple_dir_inode_operations);
eae47358 SRRH	465	}
4282d606	466
eae47358 SRRH	467	/**
	468	* tracefs_create_instance_dir - create the tracing instances directory
	469	* @name: The name of the instances directory to create
	470	* @parent: The parent directory that the instances directory will exist
	471	* @mkdir: The function to call when a mkdir is performed.
	472	* @rmdir: The function to call when a rmdir is performed.
	473	*
	474	* Only one instances directory is allowed.
	475	*
	476	* The instances directory is special as it allows for mkdir and rmdir to
	477	* to be done by userspace. When a mkdir or rmdir is performed, the inode
	478	* locks are released and the methhods passed in (@mkdir and @rmdir) are
	479	* called without locks and with the name of the directory being created
	480	* within the instances directory.
	481	*
	482	* Returns the dentry of the instances directory.
	483	*/
5248ee85 ZM	484	__init struct dentry tracefs_create_instance_dir(const char name,
5248ee85 ZM	485	struct dentry *parent,
eae47358 SRRH	486	int (mkdir)(const char name),
	487	int (rmdir)(const char name))
	488	{
	489	struct dentry *dentry;
	490
	491	/* Only allow one instance of the instances directory. */
	492	if (WARN_ON(tracefs_ops.mkdir \|\| tracefs_ops.rmdir))
4282d606 SRRH	493	return NULL;
4282d606 SRRH	494
eae47358 SRRH	495	dentry = __create_dir(name, parent, &tracefs_dir_inode_operations);
	496	if (!dentry)
	497	return NULL;
4282d606	498
eae47358 SRRH	499	tracefs_ops.mkdir = mkdir;
eae47358 SRRH	500	tracefs_ops.rmdir = rmdir;
4282d606	501
eae47358	502	return dentry;
4282d606 SRRH	503	}
4282d606 SRRH	504
a3d1e7eb	505	static void remove_one(struct dentry *victim)
4282d606	506	{
a3d1e7eb	507	simple_release_fs(&tracefs_mount, &tracefs_mount_count);
4282d606 SRRH	508	}
	509
	510	/**
a3d1e7eb	511	* tracefs_remove - recursively removes a directory
4282d606 SRRH	512	* @dentry: a pointer to a the dentry of the directory to be removed.
	513	*
	514	* This function recursively removes a directory tree in tracefs that
	515	* was previously created with a call to another tracefs function
	516	* (like tracefs_create_file() or variants thereof.)
	517	*/
a3d1e7eb	518	void tracefs_remove(struct dentry *dentry)
4282d606	519	{
4282d606 SRRH	520	if (IS_ERR_OR_NULL(dentry))
	521	return;
	522
a3d1e7eb AV	523	simple_pin_fs(&trace_fs_type, &tracefs_mount, &tracefs_mount_count);
	524	simple_recursive_removal(dentry, remove_one);
	525	simple_release_fs(&tracefs_mount, &tracefs_mount_count);
4282d606 SRRH	526	}
	527
	528	/**
	529	* tracefs_initialized - Tells whether tracefs has been registered
	530	*/
	531	bool tracefs_initialized(void)
	532	{
	533	return tracefs_registered;
	534	}
	535
	536	static int __init tracefs_init(void)
	537	{
	538	int retval;
	539
f9bb4882 EB	540	retval = sysfs_create_mount_point(kernel_kobj, "tracing");
f9bb4882 EB	541	if (retval)
cc31004a SRRH	542	return -EINVAL;
cc31004a SRRH	543
4282d606 SRRH	544	retval = register_filesystem(&trace_fs_type);
	545	if (!retval)
	546	tracefs_registered = true;
	547
	548	return retval;
	549	}
	550	core_initcall(tracefs_init);