// SPDX-License-Identifier: GPL-2.0

  /*
   *  linux/fs/proc/root.c
   *
   *  Copyright (C) 1991, 1992 Linus Torvalds
   *
   *  proc root directory handling functions
   */

  #include <linux/uaccess.h>

  
  #include <linux/errno.h>
  #include <linux/time.h>
  #include <linux/proc_fs.h>
  #include <linux/stat.h>

  #include <linux/init.h>

  #include <linux/sched.h>

  #include <linux/sched/stat.h>

  #include <linux/module.h>
  #include <linux/bitops.h>

  #include <linux/user_namespace.h>

  #include <linux/mount.h>

  #include <linux/pid_namespace.h>

  #include <linux/parser.h>

  #include <linux/cred.h>

  #include "internal.h"

  enum {

  	Opt_gid, Opt_hidepid, Opt_err,

  };
  
  static const match_table_t tokens = {

  	{Opt_hidepid, "hidepid=%u"},
  	{Opt_gid, "gid=%u"},

  	{Opt_err, NULL},
  };

  int proc_parse_options(char *options, struct pid_namespace *pid)

  {
  	char *p;
  	substring_t args[MAX_OPT_ARGS];

  	int option;

  
  	if (!options)
  		return 1;
  
  	while ((p = strsep(&options, ",")) != NULL) {
  		int token;
  		if (!*p)
  			continue;

  		args[0].to = args[0].from = NULL;

  		token = match_token(p, tokens, args);
  		switch (token) {

  		case Opt_gid:
  			if (match_int(&args[0], &option))
  				return 0;

  			pid->pid_gid = make_kgid(current_user_ns(), option);

  			break;
  		case Opt_hidepid:
  			if (match_int(&args[0], &option))
  				return 0;

  			if (option < HIDEPID_OFF ||
  			    option > HIDEPID_INVISIBLE) {

  				pr_err("proc: hidepid value must be between 0 and 2.
  ");
  				return 0;
  			}
  			pid->hide_pid = option;
  			break;

  		default:
  			pr_err("proc: unrecognized mount option \"%s\" "
  			       "or missing value
  ", p);
  			return 0;
  		}
  	}
  
  	return 1;
  }
  
  int proc_remount(struct super_block *sb, int *flags, char *data)
  {
  	struct pid_namespace *pid = sb->s_fs_info;

  
  	sync_filesystem(sb);

  	return !proc_parse_options(data, pid);
  }

  static struct dentry *proc_mount(struct file_system_type *fs_type,
  	int flags, const char *dev_name, void *data)

  {

  	struct pid_namespace *ns;

  	if (flags & SB_KERNMOUNT) {

  		ns = data;
  		data = NULL;

  	} else {

  		ns = task_active_pid_ns(current);

  	}

  	return mount_ns(fs_type, flags, data, ns, ns->user_ns, proc_fill_super);

  }
  
  static void proc_kill_sb(struct super_block *sb)
  {
  	struct pid_namespace *ns;
  
  	ns = (struct pid_namespace *)sb->s_fs_info;

  	if (ns->proc_self)
  		dput(ns->proc_self);

  	if (ns->proc_thread_self)
  		dput(ns->proc_thread_self);

  	kill_anon_super(sb);
  	put_pid_ns(ns);

  }

  static struct file_system_type proc_fs_type = {

  	.name		= "proc",

  	.mount		= proc_mount,

  	.kill_sb	= proc_kill_sb,

  	.fs_flags	= FS_USERNS_MOUNT,

  };

  void __init proc_root_init(void)
  {

  	proc_init_kmemcache();

  	set_proc_pid_nlink();

  	proc_self_init();

  	proc_thread_self_init();

  	proc_symlink("mounts", NULL, "self/mounts");

  
  	proc_net_init();

  	proc_mkdir("fs", NULL);

  	proc_mkdir("driver", NULL);

  	proc_create_mount_point("fs/nfsd"); /* somewhere for the nfsd filesystem to be mounted */

  #if defined(CONFIG_SUN_OPENPROMFS) || defined(CONFIG_SUN_OPENPROMFS_MODULE)
  	/* just give it a mountpoint */

  	proc_create_mount_point("openprom");

  #endif
  	proc_tty_init();

  	proc_mkdir("bus", NULL);

  	proc_sys_init();

  
  	register_filesystem(&proc_fs_type);

  }

  static int proc_root_getattr(const struct path *path, struct kstat *stat,
  			     u32 request_mask, unsigned int query_flags)

  {

  	generic_fillattr(d_inode(path->dentry), stat);

  	stat->nlink = proc_root.nlink + nr_processes();
  	return 0;
  }

  static struct dentry *proc_root_lookup(struct inode * dir, struct dentry * dentry, unsigned int flags)

  {

  	if (!proc_pid_lookup(dir, dentry, flags))

  		return NULL;

  	return proc_lookup(dir, dentry, flags);

  }

  static int proc_root_readdir(struct file *file, struct dir_context *ctx)

  {

  	if (ctx->pos < FIRST_PROCESS_ENTRY) {

  		int error = proc_readdir(file, ctx);
  		if (unlikely(error <= 0))
  			return error;

  		ctx->pos = FIRST_PROCESS_ENTRY;

  	}

  	return proc_pid_readdir(file, ctx);

  }
  
  /*
   * The root /proc directory is special, as it has the
   * <pid> directories. Thus we don't use the generic
   * directory handling functions for that..
   */

  static const struct file_operations proc_root_operations = {

  	.read		 = generic_read_dir,

  	.iterate_shared	 = proc_root_readdir,
  	.llseek		= generic_file_llseek,

  };
  
  /*
   * proc root can do almost nothing..
   */

  static const struct inode_operations proc_root_inode_operations = {

  	.lookup		= proc_root_lookup,

  	.getattr	= proc_root_getattr,

  };
  
  /*
   * This is the root "inode" in the /proc tree..
   */
  struct proc_dir_entry proc_root = {
  	.low_ino	= PROC_ROOT_INO, 
  	.namelen	= 5, 

  	.mode		= S_IFDIR | S_IRUGO | S_IXUGO, 
  	.nlink		= 2, 

  	.refcnt		= REFCOUNT_INIT(1),

  	.proc_iops	= &proc_root_inode_operations, 
  	.proc_fops	= &proc_root_operations,
  	.parent		= &proc_root,

  	.subdir		= RB_ROOT,

  	.name		= "/proc",

  };

  int pid_ns_prepare_proc(struct pid_namespace *ns)
  {
  	struct vfsmount *mnt;
  
  	mnt = kern_mount_data(&proc_fs_type, ns);
  	if (IS_ERR(mnt))
  		return PTR_ERR(mnt);

  	ns->proc_mnt = mnt;

  	return 0;
  }
  
  void pid_ns_release_proc(struct pid_namespace *ns)
  {

  	kern_unmount(ns->proc_mnt);

  }