diff options
Diffstat (limited to 'fs/tracefs/inode.c')
| -rw-r--r-- | fs/tracefs/inode.c | 522 |
1 files changed, 522 insertions, 0 deletions
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); |