| // 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/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); |
| 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 (!(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 int __tracefs_remove(struct dentry *dentry, struct dentry *parent) |
| { |
| int ret = 0; |
| |
| if (simple_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); |
| if (!ret) |
| fsnotify_rmdir(parent->d_inode, dentry); |
| break; |
| default: |
| simple_unlink(parent->d_inode, dentry); |
| fsnotify_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; |
| inode_lock(parent->d_inode); |
| ret = __tracefs_remove(dentry, parent); |
| inode_unlock(parent->d_inode); |
| 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; |
| down: |
| inode_lock(parent->d_inode); |
| 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 (!simple_positive(child)) |
| continue; |
| |
| /* perhaps simple_empty(child) makes more sense */ |
| if (!list_empty(&child->d_subdirs)) { |
| spin_unlock(&parent->d_lock); |
| inode_unlock(parent->d_inode); |
| 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 |
| * simple_positive() check. |
| */ |
| goto loop; |
| } |
| spin_unlock(&parent->d_lock); |
| |
| inode_unlock(parent->d_inode); |
| child = parent; |
| parent = parent->d_parent; |
| inode_lock(parent->d_inode); |
| |
| if (child != dentry) |
| /* go up */ |
| goto loop; |
| |
| if (!__tracefs_remove(child, parent)) |
| simple_release_fs(&tracefs_mount, &tracefs_mount_count); |
| inode_unlock(parent->d_inode); |
| } |
| |
| /** |
| * 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); |