OSCL-LXR linux-6.0.1/​fs/​tracefs/​inode.c	Source navigation Diff markup Identifier search General search
	Version: linux-6.0.1 spark-3.0.0 hadoop-3.2.0-src hadoop-3.3.0-src spark-2.4.7 linux-4.15.13 hadoop-2.7.4-src Revert   Change

 // 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)
 {
     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);

This page was automatically generated by the 2.1.0 LXR engine. The LXR team