// SPDX-License-Identifier: GPL-2.0-only

  /*
   *  Copyright (C) 2007
   *
   *  Author: Eric Biederman <ebiederm@xmision.com>

   */

  #include <linux/export.h>

  #include <linux/uts.h>
  #include <linux/utsname.h>

  #include <linux/sysctl.h>

  #include <linux/wait.h>

  #include <linux/rwsem.h>

  #ifdef CONFIG_PROC_SYSCTL

  static void *get_uts(struct ctl_table *table)

  {
  	char *which = table->data;

  	struct uts_namespace *uts_ns;
  
  	uts_ns = current->nsproxy->uts_ns;
  	which = (which - (char *)&init_uts_ns) + (char *)uts_ns;

  	return which;
  }

  /*
   *	Special case of dostring for the UTS structure. This has locks
   *	to observe. Should this be in kernel/sys.c ????
   */

  static int proc_do_uts_string(struct ctl_table *table, int write,

  		  void *buffer, size_t *lenp, loff_t *ppos)

  {
  	struct ctl_table uts_table;
  	int r;

  	char tmp_data[__NEW_UTS_LEN + 1];

  	memcpy(&uts_table, table, sizeof(uts_table));

  	uts_table.data = tmp_data;
  
  	/*
  	 * Buffer the value in tmp_data so that proc_dostring() can be called
  	 * without holding any locks.
  	 * We also need to read the original value in the write==1 case to
  	 * support partial writes.
  	 */
  	down_read(&uts_sem);
  	memcpy(tmp_data, get_uts(table), sizeof(tmp_data));
  	up_read(&uts_sem);

  	r = proc_dostring(&uts_table, write, buffer, lenp, ppos);

  	if (write) {
  		/*
  		 * Write back the new value.
  		 * Note that, since we dropped uts_sem, the result can
  		 * theoretically be incorrect if there are two parallel writes
  		 * at non-zero offsets to the same sysctl.
  		 */
  		down_write(&uts_sem);
  		memcpy(get_uts(table), tmp_data, sizeof(tmp_data));
  		up_write(&uts_sem);

  		proc_sys_poll_notify(table->poll);

  	}

  	return r;
  }
  #else
  #define proc_do_uts_string NULL
  #endif

  static DEFINE_CTL_TABLE_POLL(hostname_poll);
  static DEFINE_CTL_TABLE_POLL(domainname_poll);

  static struct ctl_table uts_kern_table[] = {
  	{

  		.procname	= "ostype",
  		.data		= init_uts_ns.name.sysname,
  		.maxlen		= sizeof(init_uts_ns.name.sysname),
  		.mode		= 0444,
  		.proc_handler	= proc_do_uts_string,

  	},
  	{

  		.procname	= "osrelease",
  		.data		= init_uts_ns.name.release,
  		.maxlen		= sizeof(init_uts_ns.name.release),
  		.mode		= 0444,
  		.proc_handler	= proc_do_uts_string,

  	},
  	{

  		.procname	= "version",
  		.data		= init_uts_ns.name.version,
  		.maxlen		= sizeof(init_uts_ns.name.version),
  		.mode		= 0444,
  		.proc_handler	= proc_do_uts_string,

  	},
  	{

  		.procname	= "hostname",
  		.data		= init_uts_ns.name.nodename,
  		.maxlen		= sizeof(init_uts_ns.name.nodename),
  		.mode		= 0644,
  		.proc_handler	= proc_do_uts_string,

  		.poll		= &hostname_poll,

  	},
  	{

  		.procname	= "domainname",
  		.data		= init_uts_ns.name.domainname,
  		.maxlen		= sizeof(init_uts_ns.name.domainname),
  		.mode		= 0644,
  		.proc_handler	= proc_do_uts_string,

  		.poll		= &domainname_poll,

  	},
  	{}
  };
  
  static struct ctl_table uts_root_table[] = {
  	{

  		.procname	= "kernel",
  		.mode		= 0555,
  		.child		= uts_kern_table,
  	},
  	{}
  };

  #ifdef CONFIG_PROC_SYSCTL
  /*
   * Notify userspace about a change in a certain entry of uts_kern_table,
   * identified by the parameter proc.
   */
  void uts_proc_notify(enum uts_proc proc)
  {
  	struct ctl_table *table = &uts_kern_table[proc];
  
  	proc_sys_poll_notify(table->poll);
  }
  #endif

  static int __init utsname_sysctl_init(void)
  {

  	register_sysctl_table(uts_root_table);

  	return 0;
  }

  device_initcall(utsname_sysctl_init);