diff options
Diffstat (limited to 'fs/tracefs')
| -rw-r--r-- | fs/tracefs/Makefile | 5 | ||||
| -rw-r--r-- | fs/tracefs/inode.c | 648 |
2 files changed, 653 insertions, 0 deletions
diff --git a/fs/tracefs/Makefile b/fs/tracefs/Makefile new file mode 100644 index 000000000..7c35a282b --- /dev/null +++ b/fs/tracefs/Makefile @@ -0,0 +1,5 @@ +# SPDX-License-Identifier: GPL-2.0-only +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 000000000..6541d917e --- /dev/null +++ b/fs/tracefs/inode.c @@ -0,0 +1,648 @@ +// 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 user_namespace *mnt_userns, + 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(d_inode(dentry)); + + ret = tracefs_ops.rmdir(name); + + inode_lock_nested(inode, I_MUTEX_PARENT); + inode_lock(d_inode(dentry)); + + 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; + /* Opt_* bitfield. */ + unsigned int opts; +}; + +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 void change_gid(struct dentry *dentry, kgid_t gid) +{ + if (!dentry->d_inode) + return; + dentry->d_inode->i_gid = gid; +} + +/* + * Taken from d_walk, but without he need for handling renames. + * Nothing can be renamed while walking the list, as tracefs + * does not support renames. This is only called when mounting + * or remounting the file system, to set all the files to + * the given gid. + */ +static void set_gid(struct dentry *parent, kgid_t gid) +{ + struct dentry *this_parent; + struct list_head *next; + + this_parent = parent; + spin_lock(&this_parent->d_lock); + + change_gid(this_parent, gid); +repeat: + next = this_parent->d_subdirs.next; +resume: + while (next != &this_parent->d_subdirs) { + struct list_head *tmp = next; + struct dentry *dentry = list_entry(tmp, struct dentry, d_child); + next = tmp->next; + + spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED); + + change_gid(dentry, gid); + + if (!list_empty(&dentry->d_subdirs)) { + spin_unlock(&this_parent->d_lock); + spin_release(&dentry->d_lock.dep_map, _RET_IP_); + this_parent = dentry; + spin_acquire(&this_parent->d_lock.dep_map, 0, 1, _RET_IP_); + goto repeat; + } + spin_unlock(&dentry->d_lock); + } + /* + * All done at this level ... ascend and resume the search. + */ + rcu_read_lock(); +ascend: + if (this_parent != parent) { + struct dentry *child = this_parent; + this_parent = child->d_parent; + + spin_unlock(&child->d_lock); + spin_lock(&this_parent->d_lock); + + /* go into the first sibling still alive */ + do { + next = child->d_child.next; + if (next == &this_parent->d_subdirs) + goto ascend; + child = list_entry(next, struct dentry, d_child); + } while (unlikely(child->d_flags & DCACHE_DENTRY_KILLED)); + rcu_read_unlock(); + goto resume; + } + rcu_read_unlock(); + spin_unlock(&this_parent->d_lock); + return; +} + +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->opts = 0; + 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 + */ + } + + opts->opts |= BIT(token); + } + + return 0; +} + +static int tracefs_apply_options(struct super_block *sb, bool remount) +{ + struct tracefs_fs_info *fsi = sb->s_fs_info; + struct inode *inode = d_inode(sb->s_root); + struct tracefs_mount_opts *opts = &fsi->mount_opts; + + /* + * On remount, only reset mode/uid/gid if they were provided as mount + * options. + */ + + if (!remount || opts->opts & BIT(Opt_mode)) { + inode->i_mode &= ~S_IALLUGO; + inode->i_mode |= opts->mode; + } + + if (!remount || opts->opts & BIT(Opt_uid)) + inode->i_uid = opts->uid; + + if (!remount || opts->opts & BIT(Opt_gid)) { + /* Set all the group ids to the mount option */ + set_gid(sb->s_root, 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, true); + +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, false); + + 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(d_inode(parent)); + if (unlikely(IS_DEADDIR(d_inode(parent)))) + dentry = ERR_PTR(-ENOENT); + else + dentry = lookup_one_len(name, parent, strlen(name)); + if (!IS_ERR(dentry) && d_inode(dentry)) { + dput(dentry); + dentry = ERR_PTR(-EEXIST); + } + + if (IS_ERR(dentry)) { + inode_unlock(d_inode(parent)); + simple_release_fs(&tracefs_mount, &tracefs_mount_count); + } + + return dentry; +} + +static struct dentry *failed_creating(struct dentry *dentry) +{ + inode_unlock(d_inode(dentry->d_parent)); + dput(dentry); + simple_release_fs(&tracefs_mount, &tracefs_mount_count); + return NULL; +} + +static struct dentry *end_creating(struct dentry *dentry) +{ + inode_unlock(d_inode(dentry->d_parent)); + 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; + inode->i_uid = d_inode(dentry->d_parent)->i_uid; + inode->i_gid = d_inode(dentry->d_parent)->i_gid; + d_instantiate(dentry, inode); + fsnotify_create(d_inode(dentry->d_parent), 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); + + /* Do not set bits for OTH */ + inode->i_mode = S_IFDIR | S_IRWXU | S_IRUSR| S_IRGRP | S_IXUSR | S_IXGRP; + inode->i_op = ops; + inode->i_fop = &simple_dir_operations; + inode->i_uid = d_inode(dentry->d_parent)->i_uid; + inode->i_gid = d_inode(dentry->d_parent)->i_gid; + + /* directory inodes start off with i_nlink == 2 (for "." entry) */ + inc_nlink(inode); + d_instantiate(dentry, inode); + inc_nlink(d_inode(dentry->d_parent)); + fsnotify_mkdir(d_inode(dentry->d_parent), 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) +{ + if (security_locked_down(LOCKDOWN_TRACEFS)) + return NULL; + + 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 be done by userspace. When a mkdir or rmdir is performed, the inode + * locks are released and the methods 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); |