/*
   * linux/ipc/sem.c
   * Copyright (C) 1992 Krishna Balasubramanian
   * Copyright (C) 1995 Eric Schenk, Bruno Haible
   *
   * IMPLEMENTATION NOTES ON CODE REWRITE (Eric Schenk, January 1995):
   * This code underwent a massive rewrite in order to solve some problems
   * with the original code. In particular the original code failed to
   * wake up processes that were waiting for semval to go to 0 if the
   * value went to 0 and was then incremented rapidly enough. In solving
   * this problem I have also modified the implementation so that it
   * processes pending operations in a FIFO manner, thus give a guarantee
   * that processes waiting for a lock on the semaphore won't starve
   * unless another locking process fails to unlock.
   * In addition the following two changes in behavior have been introduced:
   * - The original implementation of semop returned the value
   *   last semaphore element examined on success. This does not
   *   match the manual page specifications, and effectively
   *   allows the user to read the semaphore even if they do not
   *   have read permissions. The implementation now returns 0
   *   on success as stated in the manual page.
   * - There is some confusion over whether the set of undo adjustments
   *   to be performed at exit should be done in an atomic manner.
   *   That is, if we are attempting to decrement the semval should we queue
   *   up and wait until we can do so legally?
   *   The original implementation attempted to do this.
   *   The current implementation does not do so. This is because I don't
   *   think it is the right thing (TM) to do, and because I couldn't
   *   see a clean way to get the old behavior with the new design.
   *   The POSIX standard and SVID should be consulted to determine
   *   what behavior is mandated.
   *
   * Further notes on refinement (Christoph Rohland, December 1998):
   * - The POSIX standard says, that the undo adjustments simply should
   *   redo. So the current implementation is o.K.
   * - The previous code had two flaws:
   *   1) It actively gave the semaphore to the next waiting process
   *      sleeping on the semaphore. Since this process did not have the
   *      cpu this led to many unnecessary context switches and bad
   *      performance. Now we only check which process should be able to
   *      get the semaphore and if this process wants to reduce some
   *      semaphore value we simply wake it up without doing the
   *      operation. So it has to try to get it later. Thus e.g. the
   *      running process may reacquire the semaphore during the current
   *      time slice. If it only waits for zero or increases the semaphore,
   *      we do the operation in advance and wake it up.
   *   2) It did not wake up all zero waiting processes. We try to do
   *      better but only get the semops right which only wait for zero or
   *      increase. If there are decrement operations in the operations
   *      array we do the same as before.
   *
   * With the incarnation of O(1) scheduler, it becomes unnecessary to perform
   * check/retry algorithm for waking up blocked processes as the new scheduler
   * is better at handling thread switch than the old one.
   *
   * /proc/sysvipc/sem support (c) 1999 Dragos Acostachioaie <dragos@iname.com>
   *
   * SMP-threaded, sysctl's added

   * (c) 1999 Manfred Spraul <manfred@colorfullife.com>

   * Enforced range limit on SEM_UNDO
   * (c) 2001 Red Hat Inc <alan@redhat.com>
   * Lockless wakeup
   * (c) 2003 Manfred Spraul <manfred@colorfullife.com>

   *
   * support for audit of ipc object properties and permission changes
   * Dustin Kirkland <dustin.kirkland@us.ibm.com>

   *
   * namespaces support
   * OpenVZ, SWsoft Inc.
   * Pavel Emelianov <xemul@openvz.org>

   */

  #include <linux/slab.h>
  #include <linux/spinlock.h>
  #include <linux/init.h>
  #include <linux/proc_fs.h>
  #include <linux/time.h>

  #include <linux/security.h>
  #include <linux/syscalls.h>
  #include <linux/audit.h>

  #include <linux/capability.h>

  #include <linux/seq_file.h>

  #include <linux/rwsem.h>

  #include <linux/nsproxy.h>

  #include <linux/ipc_namespace.h>

  #include <asm/uaccess.h>
  #include "util.h"

  #define sem_ids(ns)	((ns)->ids[IPC_SEM_IDS])

  #define sem_unlock(sma)		ipc_unlock(&(sma)->sem_perm)

  #define sem_checkid(sma, semid)	ipc_checkid(&sma->sem_perm, semid)

  static int newary(struct ipc_namespace *, struct ipc_params *);

  static void freeary(struct ipc_namespace *, struct kern_ipc_perm *);

  #ifdef CONFIG_PROC_FS

  static int sysvipc_sem_proc_show(struct seq_file *s, void *it);

  #endif
  
  #define SEMMSL_FAST	256 /* 512 bytes on stack */
  #define SEMOPM_FAST	64  /* ~ 372 bytes on stack */
  
  /*
   * linked list protection:
   *	sem_undo.id_next,
   *	sem_array.sem_pending{,last},
   *	sem_array.sem_undo: sem_lock() for read/write
   *	sem_undo.proc_next: only "current" is allowed to read/write that field.
   *	
   */

  #define sc_semmsl	sem_ctls[0]
  #define sc_semmns	sem_ctls[1]
  #define sc_semopm	sem_ctls[2]
  #define sc_semmni	sem_ctls[3]

  void sem_init_ns(struct ipc_namespace *ns)

  {

  	ns->sc_semmsl = SEMMSL;
  	ns->sc_semmns = SEMMNS;
  	ns->sc_semopm = SEMOPM;
  	ns->sc_semmni = SEMMNI;
  	ns->used_sems = 0;

  	ipc_init_ids(&ns->ids[IPC_SEM_IDS]);

  }

  #ifdef CONFIG_IPC_NS

  void sem_exit_ns(struct ipc_namespace *ns)
  {

  	free_ipcs(ns, &sem_ids(ns), freeary);

  }

  #endif

  
  void __init sem_init (void)
  {

  	sem_init_ns(&init_ipc_ns);

  	ipc_init_proc_interface("sysvipc/sem",
  				"       key      semid perms      nsems   uid   gid  cuid  cgid      otime      ctime
  ",

  				IPC_SEM_IDS, sysvipc_sem_proc_show);

  }

  /*

   * sem_lock_(check_) routines are called in the paths where the rw_mutex
   * is not held.
   */

  static inline struct sem_array *sem_lock(struct ipc_namespace *ns, int id)
  {

  	struct kern_ipc_perm *ipcp = ipc_lock(&sem_ids(ns), id);

  	if (IS_ERR(ipcp))
  		return (struct sem_array *)ipcp;

  	return container_of(ipcp, struct sem_array, sem_perm);

  }
  
  static inline struct sem_array *sem_lock_check(struct ipc_namespace *ns,
  						int id)
  {

  	struct kern_ipc_perm *ipcp = ipc_lock_check(&sem_ids(ns), id);

  	if (IS_ERR(ipcp))
  		return (struct sem_array *)ipcp;

  	return container_of(ipcp, struct sem_array, sem_perm);

  }

  static inline void sem_lock_and_putref(struct sem_array *sma)
  {
  	ipc_lock_by_ptr(&sma->sem_perm);
  	ipc_rcu_putref(sma);
  }
  
  static inline void sem_getref_and_unlock(struct sem_array *sma)
  {
  	ipc_rcu_getref(sma);
  	ipc_unlock(&(sma)->sem_perm);
  }
  
  static inline void sem_putref(struct sem_array *sma)
  {
  	ipc_lock_by_ptr(&sma->sem_perm);
  	ipc_rcu_putref(sma);
  	ipc_unlock(&(sma)->sem_perm);
  }

  static inline void sem_rmid(struct ipc_namespace *ns, struct sem_array *s)
  {
  	ipc_rmid(&sem_ids(ns), &s->sem_perm);
  }

  /*
   * Lockless wakeup algorithm:
   * Without the check/retry algorithm a lockless wakeup is possible:
   * - queue.status is initialized to -EINTR before blocking.
   * - wakeup is performed by
   *	* unlinking the queue entry from sma->sem_pending
   *	* setting queue.status to IN_WAKEUP
   *	  This is the notification for the blocked thread that a
   *	  result value is imminent.
   *	* call wake_up_process
   *	* set queue.status to the final value.
   * - the previously blocked thread checks queue.status:
   *   	* if it's IN_WAKEUP, then it must wait until the value changes
   *   	* if it's not -EINTR, then the operation was completed by
   *   	  update_queue. semtimedop can return queue.status without

   *   	  performing any operation on the sem array.

   *   	* otherwise it must acquire the spinlock and check what's up.
   *
   * The two-stage algorithm is necessary to protect against the following
   * races:
   * - if queue.status is set after wake_up_process, then the woken up idle
   *   thread could race forward and try (and fail) to acquire sma->lock
   *   before update_queue had a chance to set queue.status
   * - if queue.status is written before wake_up_process and if the
   *   blocked process is woken up by a signal between writing
   *   queue.status and the wake_up_process, then the woken up
   *   process could return from semtimedop and die by calling
   *   sys_exit before wake_up_process is called. Then wake_up_process
   *   will oops, because the task structure is already invalid.
   *   (yes, this happened on s390 with sysv msg).
   *
   */
  #define IN_WAKEUP	1

  /**
   * newary - Create a new semaphore set
   * @ns: namespace
   * @params: ptr to the structure that contains key, semflg and nsems
   *

   * Called with sem_ids.rw_mutex held (as a writer)

   */

  static int newary(struct ipc_namespace *ns, struct ipc_params *params)

  {
  	int id;
  	int retval;
  	struct sem_array *sma;
  	int size;

  	key_t key = params->key;
  	int nsems = params->u.nsems;
  	int semflg = params->flg;

  
  	if (!nsems)
  		return -EINVAL;

  	if (ns->used_sems + nsems > ns->sc_semmns)

  		return -ENOSPC;
  
  	size = sizeof (*sma) + nsems * sizeof (struct sem);
  	sma = ipc_rcu_alloc(size);
  	if (!sma) {
  		return -ENOMEM;
  	}
  	memset (sma, 0, size);
  
  	sma->sem_perm.mode = (semflg & S_IRWXUGO);
  	sma->sem_perm.key = key;
  
  	sma->sem_perm.security = NULL;
  	retval = security_sem_alloc(sma);
  	if (retval) {
  		ipc_rcu_putref(sma);
  		return retval;
  	}

  	id = ipc_addid(&sem_ids(ns), &sma->sem_perm, ns->sc_semmni);

  	if (id < 0) {

  		security_sem_free(sma);
  		ipc_rcu_putref(sma);

  		return id;

  	}

  	ns->used_sems += nsems;

  
  	sma->sem_base = (struct sem *) &sma[1];

  	INIT_LIST_HEAD(&sma->sem_pending);

  	INIT_LIST_HEAD(&sma->list_id);

  	sma->sem_nsems = nsems;
  	sma->sem_ctime = get_seconds();
  	sem_unlock(sma);

  	return sma->sem_perm.id;

  }

  /*

   * Called with sem_ids.rw_mutex and ipcp locked.

   */

  static inline int sem_security(struct kern_ipc_perm *ipcp, int semflg)

  {

  	struct sem_array *sma;
  
  	sma = container_of(ipcp, struct sem_array, sem_perm);
  	return security_sem_associate(sma, semflg);

  }

  /*

   * Called with sem_ids.rw_mutex and ipcp locked.

   */

  static inline int sem_more_checks(struct kern_ipc_perm *ipcp,
  				struct ipc_params *params)

  {

  	struct sem_array *sma;
  
  	sma = container_of(ipcp, struct sem_array, sem_perm);
  	if (params->u.nsems > sma->sem_nsems)

  		return -EINVAL;
  
  	return 0;
  }
  
  asmlinkage long sys_semget(key_t key, int nsems, int semflg)

  {

  	struct ipc_namespace *ns;

  	struct ipc_ops sem_ops;
  	struct ipc_params sem_params;

  
  	ns = current->nsproxy->ipc_ns;

  	if (nsems < 0 || nsems > ns->sc_semmsl)

  		return -EINVAL;

  	sem_ops.getnew = newary;
  	sem_ops.associate = sem_security;
  	sem_ops.more_checks = sem_more_checks;
  
  	sem_params.key = key;
  	sem_params.flg = semflg;
  	sem_params.u.nsems = nsems;

  	return ipcget(ns, &sem_ids(ns), &sem_ops, &sem_params);

  }

  /*
   * Determine whether a sequence of semaphore operations would succeed
   * all at once. Return 0 if yes, 1 if need to sleep, else return error code.
   */
  
  static int try_atomic_semop (struct sem_array * sma, struct sembuf * sops,
  			     int nsops, struct sem_undo *un, int pid)
  {
  	int result, sem_op;
  	struct sembuf *sop;
  	struct sem * curr;
  
  	for (sop = sops; sop < sops + nsops; sop++) {
  		curr = sma->sem_base + sop->sem_num;
  		sem_op = sop->sem_op;
  		result = curr->semval;
    
  		if (!sem_op && result)
  			goto would_block;
  
  		result += sem_op;
  		if (result < 0)
  			goto would_block;
  		if (result > SEMVMX)
  			goto out_of_range;
  		if (sop->sem_flg & SEM_UNDO) {
  			int undo = un->semadj[sop->sem_num] - sem_op;
  			/*
  	 		 *	Exceeding the undo range is an error.
  			 */
  			if (undo < (-SEMAEM - 1) || undo > SEMAEM)
  				goto out_of_range;
  		}
  		curr->semval = result;
  	}
  
  	sop--;
  	while (sop >= sops) {
  		sma->sem_base[sop->sem_num].sempid = pid;
  		if (sop->sem_flg & SEM_UNDO)
  			un->semadj[sop->sem_num] -= sop->sem_op;
  		sop--;
  	}
  	
  	sma->sem_otime = get_seconds();
  	return 0;
  
  out_of_range:
  	result = -ERANGE;
  	goto undo;
  
  would_block:
  	if (sop->sem_flg & IPC_NOWAIT)
  		result = -EAGAIN;
  	else
  		result = 1;
  
  undo:
  	sop--;
  	while (sop >= sops) {
  		sma->sem_base[sop->sem_num].semval -= sop->sem_op;
  		sop--;
  	}
  
  	return result;
  }
  
  /* Go through the pending queue for the indicated semaphore
   * looking for tasks that can be completed.
   */
  static void update_queue (struct sem_array * sma)
  {
  	int error;
  	struct sem_queue * q;

  	q = list_entry(sma->sem_pending.next, struct sem_queue, list);
  	while (&q->list != &sma->sem_pending) {

  		error = try_atomic_semop(sma, q->sops, q->nsops,
  					 q->undo, q->pid);
  
  		/* Does q->sleeper still need to sleep? */
  		if (error <= 0) {
  			struct sem_queue *n;

  			/*
  			 * Continue scanning. The next operation
  			 * that must be checked depends on the type of the
  			 * completed operation:
  			 * - if the operation modified the array, then
  			 *   restart from the head of the queue and
  			 *   check for threads that might be waiting
  			 *   for semaphore values to become 0.
  			 * - if the operation didn't modify the array,
  			 *   then just continue.

  			 * The order of list_del() and reading ->next
  			 * is crucial: In the former case, the list_del()
  			 * must be done first [because we might be the
  			 * first entry in ->sem_pending], in the latter
  			 * case the list_del() must be done last
  			 * [because the list is invalid after the list_del()]

  			 */

  			if (q->alter) {
  				list_del(&q->list);
  				n = list_entry(sma->sem_pending.next,
  						struct sem_queue, list);
  			} else {
  				n = list_entry(q->list.next, struct sem_queue,
  						list);
  				list_del(&q->list);
  			}
  
  			/* wake up the waiting thread */
  			q->status = IN_WAKEUP;

  			wake_up_process(q->sleeper);
  			/* hands-off: q will disappear immediately after
  			 * writing q->status.
  			 */

  			smp_wmb();

  			q->status = error;
  			q = n;
  		} else {

  			q = list_entry(q->list.next, struct sem_queue, list);

  		}
  	}
  }
  
  /* The following counts are associated to each semaphore:
   *   semncnt        number of tasks waiting on semval being nonzero
   *   semzcnt        number of tasks waiting on semval being zero
   * This model assumes that a task waits on exactly one semaphore.
   * Since semaphore operations are to be performed atomically, tasks actually
   * wait on a whole sequence of semaphores simultaneously.
   * The counts we return here are a rough approximation, but still
   * warrant that semncnt+semzcnt>0 if the task is on the pending queue.
   */
  static int count_semncnt (struct sem_array * sma, ushort semnum)
  {
  	int semncnt;
  	struct sem_queue * q;
  
  	semncnt = 0;

  	list_for_each_entry(q, &sma->sem_pending, list) {

  		struct sembuf * sops = q->sops;
  		int nsops = q->nsops;
  		int i;
  		for (i = 0; i < nsops; i++)
  			if (sops[i].sem_num == semnum
  			    && (sops[i].sem_op < 0)
  			    && !(sops[i].sem_flg & IPC_NOWAIT))
  				semncnt++;
  	}
  	return semncnt;
  }

  static int count_semzcnt (struct sem_array * sma, ushort semnum)
  {
  	int semzcnt;
  	struct sem_queue * q;
  
  	semzcnt = 0;

  	list_for_each_entry(q, &sma->sem_pending, list) {

  		struct sembuf * sops = q->sops;
  		int nsops = q->nsops;
  		int i;
  		for (i = 0; i < nsops; i++)
  			if (sops[i].sem_num == semnum
  			    && (sops[i].sem_op == 0)
  			    && !(sops[i].sem_flg & IPC_NOWAIT))
  				semzcnt++;
  	}
  	return semzcnt;
  }

  void free_un(struct rcu_head *head)
  {
  	struct sem_undo *un = container_of(head, struct sem_undo, rcu);
  	kfree(un);
  }

  /* Free a semaphore set. freeary() is called with sem_ids.rw_mutex locked
   * as a writer and the spinlock for this semaphore set hold. sem_ids.rw_mutex
   * remains locked on exit.

   */

  static void freeary(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp)

  {

  	struct sem_undo *un, *tu;
  	struct sem_queue *q, *tq;

  	struct sem_array *sma = container_of(ipcp, struct sem_array, sem_perm);

  	/* Free the existing undo structures for this semaphore set.  */

  	assert_spin_locked(&sma->sem_perm.lock);

  	list_for_each_entry_safe(un, tu, &sma->list_id, list_id) {
  		list_del(&un->list_id);
  		spin_lock(&un->ulp->lock);

  		un->semid = -1;

  		list_del_rcu(&un->list_proc);
  		spin_unlock(&un->ulp->lock);
  		call_rcu(&un->rcu, free_un);
  	}

  
  	/* Wake up all pending processes and let them fail with EIDRM. */

  	list_for_each_entry_safe(q, tq, &sma->sem_pending, list) {

  		list_del(&q->list);

  		q->status = IN_WAKEUP;
  		wake_up_process(q->sleeper); /* doesn't sleep */

  		smp_wmb();

  		q->status = -EIDRM;	/* hands-off q */

  	}

  	/* Remove the semaphore set from the IDR */
  	sem_rmid(ns, sma);

  	sem_unlock(sma);

  	ns->used_sems -= sma->sem_nsems;

  	security_sem_free(sma);
  	ipc_rcu_putref(sma);
  }
  
  static unsigned long copy_semid_to_user(void __user *buf, struct semid64_ds *in, int version)
  {
  	switch(version) {
  	case IPC_64:
  		return copy_to_user(buf, in, sizeof(*in));
  	case IPC_OLD:
  	    {
  		struct semid_ds out;
  
  		ipc64_perm_to_ipc_perm(&in->sem_perm, &out.sem_perm);
  
  		out.sem_otime	= in->sem_otime;
  		out.sem_ctime	= in->sem_ctime;
  		out.sem_nsems	= in->sem_nsems;
  
  		return copy_to_user(buf, &out, sizeof(out));
  	    }
  	default:
  		return -EINVAL;
  	}
  }

  static int semctl_nolock(struct ipc_namespace *ns, int semid,
  			 int cmd, int version, union semun arg)

  {
  	int err = -EINVAL;
  	struct sem_array *sma;
  
  	switch(cmd) {
  	case IPC_INFO:
  	case SEM_INFO:
  	{
  		struct seminfo seminfo;
  		int max_id;
  
  		err = security_sem_semctl(NULL, cmd);
  		if (err)
  			return err;
  		
  		memset(&seminfo,0,sizeof(seminfo));

  		seminfo.semmni = ns->sc_semmni;
  		seminfo.semmns = ns->sc_semmns;
  		seminfo.semmsl = ns->sc_semmsl;
  		seminfo.semopm = ns->sc_semopm;

  		seminfo.semvmx = SEMVMX;
  		seminfo.semmnu = SEMMNU;
  		seminfo.semmap = SEMMAP;
  		seminfo.semume = SEMUME;

  		down_read(&sem_ids(ns).rw_mutex);

  		if (cmd == SEM_INFO) {

  			seminfo.semusz = sem_ids(ns).in_use;
  			seminfo.semaem = ns->used_sems;

  		} else {
  			seminfo.semusz = SEMUSZ;
  			seminfo.semaem = SEMAEM;
  		}

  		max_id = ipc_get_maxid(&sem_ids(ns));

  		up_read(&sem_ids(ns).rw_mutex);

  		if (copy_to_user (arg.__buf, &seminfo, sizeof(struct seminfo))) 
  			return -EFAULT;
  		return (max_id < 0) ? 0: max_id;
  	}

  	case IPC_STAT:

  	case SEM_STAT:
  	{
  		struct semid64_ds tbuf;
  		int id;

  		if (cmd == SEM_STAT) {
  			sma = sem_lock(ns, semid);
  			if (IS_ERR(sma))
  				return PTR_ERR(sma);
  			id = sma->sem_perm.id;
  		} else {
  			sma = sem_lock_check(ns, semid);
  			if (IS_ERR(sma))
  				return PTR_ERR(sma);
  			id = 0;
  		}

  
  		err = -EACCES;
  		if (ipcperms (&sma->sem_perm, S_IRUGO))
  			goto out_unlock;
  
  		err = security_sem_semctl(sma, cmd);
  		if (err)
  			goto out_unlock;

  		memset(&tbuf, 0, sizeof(tbuf));

  		kernel_to_ipc64_perm(&sma->sem_perm, &tbuf.sem_perm);
  		tbuf.sem_otime  = sma->sem_otime;
  		tbuf.sem_ctime  = sma->sem_ctime;
  		tbuf.sem_nsems  = sma->sem_nsems;
  		sem_unlock(sma);
  		if (copy_semid_to_user (arg.buf, &tbuf, version))
  			return -EFAULT;
  		return id;
  	}
  	default:
  		return -EINVAL;
  	}
  	return err;
  out_unlock:
  	sem_unlock(sma);
  	return err;
  }

  static int semctl_main(struct ipc_namespace *ns, int semid, int semnum,
  		int cmd, int version, union semun arg)

  {
  	struct sem_array *sma;
  	struct sem* curr;
  	int err;
  	ushort fast_sem_io[SEMMSL_FAST];
  	ushort* sem_io = fast_sem_io;
  	int nsems;

  	sma = sem_lock_check(ns, semid);
  	if (IS_ERR(sma))
  		return PTR_ERR(sma);

  
  	nsems = sma->sem_nsems;

  	err = -EACCES;
  	if (ipcperms (&sma->sem_perm, (cmd==SETVAL||cmd==SETALL)?S_IWUGO:S_IRUGO))
  		goto out_unlock;
  
  	err = security_sem_semctl(sma, cmd);
  	if (err)
  		goto out_unlock;
  
  	err = -EACCES;
  	switch (cmd) {
  	case GETALL:
  	{
  		ushort __user *array = arg.array;
  		int i;
  
  		if(nsems > SEMMSL_FAST) {

  			sem_getref_and_unlock(sma);

  
  			sem_io = ipc_alloc(sizeof(ushort)*nsems);
  			if(sem_io == NULL) {

  				sem_putref(sma);

  				return -ENOMEM;
  			}

  			sem_lock_and_putref(sma);

  			if (sma->sem_perm.deleted) {
  				sem_unlock(sma);
  				err = -EIDRM;
  				goto out_free;
  			}
  		}
  
  		for (i = 0; i < sma->sem_nsems; i++)
  			sem_io[i] = sma->sem_base[i].semval;
  		sem_unlock(sma);
  		err = 0;
  		if(copy_to_user(array, sem_io, nsems*sizeof(ushort)))
  			err = -EFAULT;
  		goto out_free;
  	}
  	case SETALL:
  	{
  		int i;
  		struct sem_undo *un;

  		sem_getref_and_unlock(sma);

  
  		if(nsems > SEMMSL_FAST) {
  			sem_io = ipc_alloc(sizeof(ushort)*nsems);
  			if(sem_io == NULL) {

  				sem_putref(sma);

  				return -ENOMEM;
  			}
  		}
  
  		if (copy_from_user (sem_io, arg.array, nsems*sizeof(ushort))) {

  			sem_putref(sma);

  			err = -EFAULT;
  			goto out_free;
  		}
  
  		for (i = 0; i < nsems; i++) {
  			if (sem_io[i] > SEMVMX) {

  				sem_putref(sma);

  				err = -ERANGE;
  				goto out_free;
  			}
  		}

  		sem_lock_and_putref(sma);

  		if (sma->sem_perm.deleted) {
  			sem_unlock(sma);
  			err = -EIDRM;
  			goto out_free;
  		}
  
  		for (i = 0; i < nsems; i++)
  			sma->sem_base[i].semval = sem_io[i];

  
  		assert_spin_locked(&sma->sem_perm.lock);
  		list_for_each_entry(un, &sma->list_id, list_id) {

  			for (i = 0; i < nsems; i++)
  				un->semadj[i] = 0;

  		}

  		sma->sem_ctime = get_seconds();
  		/* maybe some queued-up processes were waiting for this */
  		update_queue(sma);
  		err = 0;
  		goto out_unlock;
  	}

  	/* GETVAL, GETPID, GETNCTN, GETZCNT, SETVAL: fall-through */
  	}
  	err = -EINVAL;
  	if(semnum < 0 || semnum >= nsems)
  		goto out_unlock;
  
  	curr = &sma->sem_base[semnum];
  
  	switch (cmd) {
  	case GETVAL:
  		err = curr->semval;
  		goto out_unlock;
  	case GETPID:
  		err = curr->sempid;
  		goto out_unlock;
  	case GETNCNT:
  		err = count_semncnt(sma,semnum);
  		goto out_unlock;
  	case GETZCNT:
  		err = count_semzcnt(sma,semnum);
  		goto out_unlock;
  	case SETVAL:
  	{
  		int val = arg.val;
  		struct sem_undo *un;

  		err = -ERANGE;
  		if (val > SEMVMX || val < 0)
  			goto out_unlock;

  		assert_spin_locked(&sma->sem_perm.lock);
  		list_for_each_entry(un, &sma->list_id, list_id)

  			un->semadj[semnum] = 0;

  		curr->semval = val;

  		curr->sempid = task_tgid_vnr(current);

  		sma->sem_ctime = get_seconds();
  		/* maybe some queued-up processes were waiting for this */
  		update_queue(sma);
  		err = 0;
  		goto out_unlock;
  	}
  	}
  out_unlock:
  	sem_unlock(sma);
  out_free:
  	if(sem_io != fast_sem_io)
  		ipc_free(sem_io, sizeof(ushort)*nsems);
  	return err;
  }

  static inline unsigned long
  copy_semid_from_user(struct semid64_ds *out, void __user *buf, int version)

  {
  	switch(version) {
  	case IPC_64:

  		if (copy_from_user(out, buf, sizeof(*out)))

  			return -EFAULT;

  		return 0;

  	case IPC_OLD:
  	    {
  		struct semid_ds tbuf_old;
  
  		if(copy_from_user(&tbuf_old, buf, sizeof(tbuf_old)))
  			return -EFAULT;

  		out->sem_perm.uid	= tbuf_old.sem_perm.uid;
  		out->sem_perm.gid	= tbuf_old.sem_perm.gid;
  		out->sem_perm.mode	= tbuf_old.sem_perm.mode;

  
  		return 0;
  	    }
  	default:
  		return -EINVAL;
  	}
  }

  /*
   * This function handles some semctl commands which require the rw_mutex
   * to be held in write mode.
   * NOTE: no locks must be held, the rw_mutex is taken inside this function.
   */

  static int semctl_down(struct ipc_namespace *ns, int semid,
  		       int cmd, int version, union semun arg)

  {
  	struct sem_array *sma;
  	int err;

  	struct semid64_ds semid64;

  	struct kern_ipc_perm *ipcp;
  
  	if(cmd == IPC_SET) {

  		if (copy_semid_from_user(&semid64, arg.buf, version))

  			return -EFAULT;

  	}

  	ipcp = ipcctl_pre_down(&sem_ids(ns), semid, cmd, &semid64.sem_perm, 0);
  	if (IS_ERR(ipcp))
  		return PTR_ERR(ipcp);

  	sma = container_of(ipcp, struct sem_array, sem_perm);

  
  	err = security_sem_semctl(sma, cmd);
  	if (err)
  		goto out_unlock;
  
  	switch(cmd){
  	case IPC_RMID:

  		freeary(ns, ipcp);

  		goto out_up;

  	case IPC_SET:

  		ipc_update_perm(&semid64.sem_perm, ipcp);

  		sma->sem_ctime = get_seconds();

  		break;
  	default:

  		err = -EINVAL;

  	}

  
  out_unlock:
  	sem_unlock(sma);

  out_up:
  	up_write(&sem_ids(ns).rw_mutex);

  	return err;
  }
  
  asmlinkage long sys_semctl (int semid, int semnum, int cmd, union semun arg)
  {
  	int err = -EINVAL;
  	int version;

  	struct ipc_namespace *ns;

  
  	if (semid < 0)
  		return -EINVAL;
  
  	version = ipc_parse_version(&cmd);

  	ns = current->nsproxy->ipc_ns;

  
  	switch(cmd) {
  	case IPC_INFO:
  	case SEM_INFO:

  	case IPC_STAT:

  	case SEM_STAT:

  		err = semctl_nolock(ns, semid, cmd, version, arg);

  		return err;
  	case GETALL:
  	case GETVAL:
  	case GETPID:
  	case GETNCNT:
  	case GETZCNT:

  	case SETVAL:
  	case SETALL:

  		err = semctl_main(ns,semid,semnum,cmd,version,arg);

  		return err;
  	case IPC_RMID:
  	case IPC_SET:

  		err = semctl_down(ns, semid, cmd, version, arg);

  		return err;
  	default:
  		return -EINVAL;
  	}
  }

  /* If the task doesn't already have a undo_list, then allocate one
   * here.  We guarantee there is only one thread using this undo list,
   * and current is THE ONE
   *
   * If this allocation and assignment succeeds, but later
   * portions of this code fail, there is no need to free the sem_undo_list.
   * Just let it stay associated with the task, and it'll be freed later
   * at exit time.
   *
   * This can block, so callers must hold no locks.
   */
  static inline int get_undo_list(struct sem_undo_list **undo_listp)
  {
  	struct sem_undo_list *undo_list;

  
  	undo_list = current->sysvsem.undo_list;
  	if (!undo_list) {

  		undo_list = kzalloc(sizeof(*undo_list), GFP_KERNEL);

  		if (undo_list == NULL)
  			return -ENOMEM;

  		spin_lock_init(&undo_list->lock);

  		atomic_set(&undo_list->refcnt, 1);

  		INIT_LIST_HEAD(&undo_list->list_proc);

  		current->sysvsem.undo_list = undo_list;
  	}
  	*undo_listp = undo_list;
  	return 0;
  }
  
  static struct sem_undo *lookup_undo(struct sem_undo_list *ulp, int semid)
  {

  	struct sem_undo *walk;

  	list_for_each_entry_rcu(walk, &ulp->list_proc, list_proc) {

  		if (walk->semid == semid)
  			return walk;

  	}

  	return NULL;

  }

  /**
   * find_alloc_undo - Lookup (and if not present create) undo array
   * @ns: namespace
   * @semid: semaphore array id
   *
   * The function looks up (and if not present creates) the undo structure.
   * The size of the undo structure depends on the size of the semaphore
   * array, thus the alloc path is not that straightforward.

   * Lifetime-rules: sem_undo is rcu-protected, on success, the function
   * performs a rcu_read_lock().

   */
  static struct sem_undo *find_alloc_undo(struct ipc_namespace *ns, int semid)

  {
  	struct sem_array *sma;
  	struct sem_undo_list *ulp;
  	struct sem_undo *un, *new;
  	int nsems;
  	int error;
  
  	error = get_undo_list(&ulp);
  	if (error)
  		return ERR_PTR(error);

  	rcu_read_lock();

  	spin_lock(&ulp->lock);

  	un = lookup_undo(ulp, semid);

  	spin_unlock(&ulp->lock);

  	if (likely(un!=NULL))
  		goto out;

  	rcu_read_unlock();

  
  	/* no undo structure around - allocate one. */

  	/* step 1: figure out the size of the semaphore array */

  	sma = sem_lock_check(ns, semid);
  	if (IS_ERR(sma))
  		return ERR_PTR(PTR_ERR(sma));

  	nsems = sma->sem_nsems;

  	sem_getref_and_unlock(sma);

  	/* step 2: allocate new undo structure */

  	new = kzalloc(sizeof(struct sem_undo) + sizeof(short)*nsems, GFP_KERNEL);

  	if (!new) {

  		sem_putref(sma);

  		return ERR_PTR(-ENOMEM);
  	}

  	/* step 3: Acquire the lock on semaphore array */

  	sem_lock_and_putref(sma);

  	if (sma->sem_perm.deleted) {
  		sem_unlock(sma);

  		kfree(new);
  		un = ERR_PTR(-EIDRM);
  		goto out;
  	}

  	spin_lock(&ulp->lock);
  
  	/*
  	 * step 4: check for races: did someone else allocate the undo struct?
  	 */
  	un = lookup_undo(ulp, semid);
  	if (un) {
  		kfree(new);
  		goto success;
  	}

  	/* step 5: initialize & link new undo structure */
  	new->semadj = (short *) &new[1];

  	new->ulp = ulp;

  	new->semid = semid;
  	assert_spin_locked(&ulp->lock);

  	list_add_rcu(&new->list_proc, &ulp->list_proc);

  	assert_spin_locked(&sma->sem_perm.lock);
  	list_add(&new->list_id, &sma->list_id);

  	un = new;

  success:

  	spin_unlock(&ulp->lock);

  	rcu_read_lock();
  	sem_unlock(sma);

  out:
  	return un;
  }
  
  asmlinkage long sys_semtimedop(int semid, struct sembuf __user *tsops,
  			unsigned nsops, const struct timespec __user *timeout)
  {
  	int error = -EINVAL;
  	struct sem_array *sma;
  	struct sembuf fast_sops[SEMOPM_FAST];
  	struct sembuf* sops = fast_sops, *sop;
  	struct sem_undo *un;

  	int undos = 0, alter = 0, max;

  	struct sem_queue queue;
  	unsigned long jiffies_left = 0;

  	struct ipc_namespace *ns;
  
  	ns = current->nsproxy->ipc_ns;

  
  	if (nsops < 1 || semid < 0)
  		return -EINVAL;

  	if (nsops > ns->sc_semopm)

  		return -E2BIG;
  	if(nsops > SEMOPM_FAST) {
  		sops = kmalloc(sizeof(*sops)*nsops,GFP_KERNEL);
  		if(sops==NULL)
  			return -ENOMEM;
  	}
  	if (copy_from_user (sops, tsops, nsops * sizeof(*tsops))) {
  		error=-EFAULT;
  		goto out_free;
  	}
  	if (timeout) {
  		struct timespec _timeout;
  		if (copy_from_user(&_timeout, timeout, sizeof(*timeout))) {
  			error = -EFAULT;
  			goto out_free;
  		}
  		if (_timeout.tv_sec < 0 || _timeout.tv_nsec < 0 ||
  			_timeout.tv_nsec >= 1000000000L) {
  			error = -EINVAL;
  			goto out_free;
  		}
  		jiffies_left = timespec_to_jiffies(&_timeout);
  	}
  	max = 0;
  	for (sop = sops; sop < sops + nsops; sop++) {
  		if (sop->sem_num >= max)
  			max = sop->sem_num;
  		if (sop->sem_flg & SEM_UNDO)

  			undos = 1;
  		if (sop->sem_op != 0)

  			alter = 1;
  	}

  	if (undos) {

  		un = find_alloc_undo(ns, semid);

  		if (IS_ERR(un)) {
  			error = PTR_ERR(un);
  			goto out_free;
  		}
  	} else
  		un = NULL;

  	sma = sem_lock_check(ns, semid);
  	if (IS_ERR(sma)) {

  		if (un)
  			rcu_read_unlock();

  		error = PTR_ERR(sma);

  		goto out_free;

  	}

  	/*

  	 * semid identifiers are not unique - find_alloc_undo may have

  	 * allocated an undo structure, it was invalidated by an RMID

  	 * and now a new array with received the same id. Check and fail.

  	 * This case can be detected checking un->semid. The existance of
  	 * "un" itself is guaranteed by rcu.

  	 */

  	error = -EIDRM;

  	if (un) {
  		if (un->semid == -1) {
  			rcu_read_unlock();
  			goto out_unlock_free;
  		} else {
  			/*
  			 * rcu lock can be released, "un" cannot disappear:
  			 * - sem_lock is acquired, thus IPC_RMID is
  			 *   impossible.
  			 * - exit_sem is impossible, it always operates on
  			 *   current (or a dead task).
  			 */
  
  			rcu_read_unlock();
  		}
  	}

  	error = -EFBIG;
  	if (max >= sma->sem_nsems)
  		goto out_unlock_free;
  
  	error = -EACCES;
  	if (ipcperms(&sma->sem_perm, alter ? S_IWUGO : S_IRUGO))
  		goto out_unlock_free;
  
  	error = security_sem_semop(sma, sops, nsops, alter);
  	if (error)
  		goto out_unlock_free;

  	error = try_atomic_semop (sma, sops, nsops, un, task_tgid_vnr(current));

  	if (error <= 0) {
  		if (alter && error == 0)
  			update_queue (sma);
  		goto out_unlock_free;
  	}
  
  	/* We need to sleep on this operation, so we put the current
  	 * task into the pending queue and go to sleep.
  	 */
  		

  	queue.sops = sops;
  	queue.nsops = nsops;
  	queue.undo = un;

  	queue.pid = task_tgid_vnr(current);

  	queue.alter = alter;
  	if (alter)

  		list_add_tail(&queue.list, &sma->sem_pending);

  	else

  		list_add(&queue.list, &sma->sem_pending);

  
  	queue.status = -EINTR;
  	queue.sleeper = current;
  	current->state = TASK_INTERRUPTIBLE;
  	sem_unlock(sma);
  
  	if (timeout)
  		jiffies_left = schedule_timeout(jiffies_left);
  	else
  		schedule();
  
  	error = queue.status;
  	while(unlikely(error == IN_WAKEUP)) {
  		cpu_relax();
  		error = queue.status;
  	}
  
  	if (error != -EINTR) {
  		/* fast path: update_queue already obtained all requested
  		 * resources */
  		goto out_free;
  	}

  	sma = sem_lock(ns, semid);

  	if (IS_ERR(sma)) {

  		error = -EIDRM;
  		goto out_free;
  	}
  
  	/*
  	 * If queue.status != -EINTR we are woken up by another process
  	 */
  	error = queue.status;
  	if (error != -EINTR) {
  		goto out_unlock_free;
  	}
  
  	/*
  	 * If an interrupt occurred we have to clean up the queue
  	 */
  	if (timeout && jiffies_left == 0)
  		error = -EAGAIN;

  	list_del(&queue.list);

  	goto out_unlock_free;
  
  out_unlock_free:
  	sem_unlock(sma);
  out_free:
  	if(sops != fast_sops)
  		kfree(sops);
  	return error;
  }
  
  asmlinkage long sys_semop (int semid, struct sembuf __user *tsops, unsigned nsops)
  {
  	return sys_semtimedop(semid, tsops, nsops, NULL);
  }
  
  /* If CLONE_SYSVSEM is set, establish sharing of SEM_UNDO state between
   * parent and child tasks.

   */
  
  int copy_semundo(unsigned long clone_flags, struct task_struct *tsk)
  {
  	struct sem_undo_list *undo_list;
  	int error;
  
  	if (clone_flags & CLONE_SYSVSEM) {
  		error = get_undo_list(&undo_list);
  		if (error)
  			return error;

  		atomic_inc(&undo_list->refcnt);
  		tsk->sysvsem.undo_list = undo_list;
  	} else 
  		tsk->sysvsem.undo_list = NULL;
  
  	return 0;
  }
  
  /*
   * add semadj values to semaphores, free undo structures.
   * undo structures are not freed when semaphore arrays are destroyed
   * so some of them may be out of date.
   * IMPLEMENTATION NOTE: There is some confusion over whether the
   * set of adjustments that needs to be done should be done in an atomic
   * manner or not. That is, if we are attempting to decrement the semval
   * should we queue up and wait until we can do so legally?
   * The original implementation attempted to do this (queue and wait).
   * The current implementation does not do so. The POSIX standard
   * and SVID should be consulted to determine what behavior is mandated.
   */
  void exit_sem(struct task_struct *tsk)
  {

  	struct sem_undo_list *ulp;

  	ulp = tsk->sysvsem.undo_list;
  	if (!ulp)

  		return;

  	tsk->sysvsem.undo_list = NULL;

  	if (!atomic_dec_and_test(&ulp->refcnt))

  		return;

  	for (;;) {

  		struct sem_array *sma;

  		struct sem_undo *un;
  		int semid;

  		int i;

  		rcu_read_lock();
  		un = list_entry(rcu_dereference(ulp->list_proc.next),
  					struct sem_undo, list_proc);
  		if (&un->list_proc == &ulp->list_proc)
  			semid = -1;
  		 else
  			semid = un->semid;
  		rcu_read_unlock();

  		if (semid == -1)
  			break;

  		sma = sem_lock_check(tsk->nsproxy->ipc_ns, un->semid);

  		/* exit_sem raced with IPC_RMID, nothing to do */
  		if (IS_ERR(sma))
  			continue;

  		un = lookup_undo(ulp, semid);
  		if (un == NULL) {
  			/* exit_sem raced with IPC_RMID+semget() that created
  			 * exactly the same semid. Nothing to do.
  			 */
  			sem_unlock(sma);
  			continue;
  		}
  
  		/* remove un from the linked lists */

  		assert_spin_locked(&sma->sem_perm.lock);
  		list_del(&un->list_id);

  		spin_lock(&ulp->lock);
  		list_del_rcu(&un->list_proc);
  		spin_unlock(&ulp->lock);

  		/* perform adjustments registered in un */
  		for (i = 0; i < sma->sem_nsems; i++) {

  			struct sem * semaphore = &sma->sem_base[i];

  			if (un->semadj[i]) {
  				semaphore->semval += un->semadj[i];

  				/*
  				 * Range checks of the new semaphore value,
  				 * not defined by sus:
  				 * - Some unices ignore the undo entirely
  				 *   (e.g. HP UX 11i 11.22, Tru64 V5.1)
  				 * - some cap the value (e.g. FreeBSD caps
  				 *   at 0, but doesn't enforce SEMVMX)
  				 *
  				 * Linux caps the semaphore value, both at 0
  				 * and at SEMVMX.
  				 *
  				 * 	Manfred <manfred@colorfullife.com>
  				 */

  				if (semaphore->semval < 0)
  					semaphore->semval = 0;
  				if (semaphore->semval > SEMVMX)
  					semaphore->semval = SEMVMX;

  				semaphore->sempid = task_tgid_vnr(current);

  			}
  		}
  		sma->sem_otime = get_seconds();
  		/* maybe some queued-up processes were waiting for this */
  		update_queue(sma);

  		sem_unlock(sma);

  
  		call_rcu(&un->rcu, free_un);

  	}

  	kfree(ulp);

  }
  
  #ifdef CONFIG_PROC_FS

  static int sysvipc_sem_proc_show(struct seq_file *s, void *it)

  {

  	struct sem_array *sma = it;
  
  	return seq_printf(s,
  			  "%10d %10d  %4o %10lu %5u %5u %5u %5u %10lu %10lu
  ",
  			  sma->sem_perm.key,

  			  sma->sem_perm.id,

  			  sma->sem_perm.mode,
  			  sma->sem_nsems,
  			  sma->sem_perm.uid,
  			  sma->sem_perm.gid,
  			  sma->sem_perm.cuid,
  			  sma->sem_perm.cgid,
  			  sma->sem_otime,
  			  sma->sem_ctime);

  }
  #endif