5 files changed, 570 insertions, 0 deletions

diff --git a/fs/Makefile b/fs/Makefile
index bedff48e8fdc..d244b8d973ac 100644
--- a/fs/Makefile
+++ b/fs/Makefile
@@ -118,6 +118,7 @@ obj-$(CONFIG_HOSTFS)		+= hostfs/
 obj-$(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/
diff --git a/fs/tracefs/Makefile b/fs/tracefs/Makefile
new file mode 100644
index 000000000000..82fa35b656c4
--- /dev/null
+++ b/fs/tracefs/Makefile
@@ -0,0 +1,4 @@
+tracefs-objs    := inode.o
+
+obj-$(CONFIG_TRACING)   += tracefs.o
+
diff --git a/fs/tracefs/inode.c b/fs/tracefs/inode.c
new file mode 100644
index 000000000000..5b1547a452d8
--- /dev/null
+++ b/fs/tracefs/inode.c
@@ -0,0 +1,522 @@
+/*
+ *  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);
diff --git a/include/linux/tracefs.h b/include/linux/tracefs.h
new file mode 100644
index 000000000000..23e04ce21749
--- /dev/null
+++ b/include/linux/tracefs.h
@@ -0,0 +1,41 @@
+/*
+ *  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
diff --git a/include/uapi/linux/magic.h b/include/uapi/linux/magic.h
index 7d664ea85ebd..7b1425a6b370 100644
--- a/include/uapi/linux/magic.h
+++ b/include/uapi/linux/magic.h
@@ -58,6 +58,8 @@
 
 #define STACK_END_MAGIC         0x57AC6E9D
 
+#define TRACEFS_MAGIC          0x74726163
+
 #define V9FS_MAGIC              0x01021997
 
 #define BDEVFS_MAGIC            0x62646576