/*
   * linux/kernel/futex_compat.c
   *
   * Futex compatibililty routines.
   *
   * Copyright 2006, Red Hat, Inc., Ingo Molnar
   */
  
  #include <linux/linkage.h>
  #include <linux/compat.h>
  #include <linux/futex.h>
  
  #include <asm/uaccess.h>

  
  /*
   * Fetch a robust-list pointer. Bit 0 signals PI futexes:
   */
  static inline int
  fetch_robust_entry(compat_uptr_t *uentry, struct robust_list __user **entry,

  		   compat_uptr_t __user *head, int *pi)

  {
  	if (get_user(*uentry, head))
  		return -EFAULT;
  
  	*entry = compat_ptr((*uentry) & ~1);
  	*pi = (unsigned int)(*uentry) & 1;
  
  	return 0;
  }

  /*
   * Walk curr->robust_list (very carefully, it's a userspace list!)
   * and mark any locks found there dead, and notify any waiters.
   *
   * We silently return on any sign of list-walking problem.
   */
  void compat_exit_robust_list(struct task_struct *curr)
  {
  	struct compat_robust_list_head __user *head = curr->compat_robust_list;
  	struct robust_list __user *entry, *pending;

  	unsigned int limit = ROBUST_LIST_LIMIT, pi, pip;

  	compat_uptr_t uentry, upending;

  	compat_long_t futex_offset;
  
  	/*
  	 * Fetch the list head (which was registered earlier, via
  	 * sys_set_robust_list()):
  	 */

  	if (fetch_robust_entry(&uentry, &entry, &head->list.next, &pi))

  		return;

  	/*
  	 * Fetch the relative futex offset:
  	 */
  	if (get_user(futex_offset, &head->futex_offset))
  		return;
  	/*
  	 * Fetch any possibly pending lock-add first, and handle it
  	 * if it exists:
  	 */

  	if (fetch_robust_entry(&upending, &pending,

  			       &head->list_op_pending, &pip))

  		return;

  	if (upending)

  		handle_futex_death((void __user *)pending + futex_offset, curr, pip);

  
  	while (compat_ptr(uentry) != &head->list) {
  		/*
  		 * A pending lock might already be on the list, so
  		 * dont process it twice:
  		 */
  		if (entry != pending)

  			if (handle_futex_death((void __user *)entry + futex_offset,

  						curr, pi))

  				return;
  
  		/*
  		 * Fetch the next entry in the list:
  		 */

  		if (fetch_robust_entry(&uentry, &entry,

  				       (compat_uptr_t __user *)&entry->next, &pi))

  			return;

  		/*
  		 * Avoid excessively long or circular lists:
  		 */
  		if (!--limit)
  			break;
  
  		cond_resched();
  	}
  }
  
  asmlinkage long
  compat_sys_set_robust_list(struct compat_robust_list_head __user *head,
  			   compat_size_t len)
  {
  	if (unlikely(len != sizeof(*head)))
  		return -EINVAL;
  
  	current->compat_robust_list = head;
  
  	return 0;
  }
  
  asmlinkage long

  compat_sys_get_robust_list(int pid, compat_uptr_t __user *head_ptr,

  			   compat_size_t __user *len_ptr)
  {

  	struct compat_robust_list_head __user *head;

  	unsigned long ret;
  
  	if (!pid)
  		head = current->compat_robust_list;
  	else {
  		struct task_struct *p;
  
  		ret = -ESRCH;
  		read_lock(&tasklist_lock);
  		p = find_task_by_pid(pid);
  		if (!p)
  			goto err_unlock;
  		ret = -EPERM;
  		if ((current->euid != p->euid) && (current->euid != p->uid) &&
  				!capable(CAP_SYS_PTRACE))
  			goto err_unlock;
  		head = p->compat_robust_list;
  		read_unlock(&tasklist_lock);
  	}
  
  	if (put_user(sizeof(*head), len_ptr))
  		return -EFAULT;
  	return put_user(ptr_to_compat(head), head_ptr);
  
  err_unlock:
  	read_unlock(&tasklist_lock);
  
  	return ret;
  }

  asmlinkage long compat_sys_futex(u32 __user *uaddr, int op, u32 val,

  		struct compat_timespec __user *utime, u32 __user *uaddr2,

  		u32 val3)

  {
  	struct timespec t;
  	unsigned long timeout = MAX_SCHEDULE_TIMEOUT;
  	int val2 = 0;

  	if (utime && (op == FUTEX_WAIT || op == FUTEX_LOCK_PI)) {

  		if (get_compat_timespec(&t, utime))
  			return -EFAULT;

  		if (!timespec_valid(&t))
  			return -EINVAL;

  		if (op == FUTEX_WAIT)
  			timeout = timespec_to_jiffies(&t) + 1;
  		else {
  			timeout = t.tv_sec;
  			val2 = t.tv_nsec;
  		}

  	}

  	if (op == FUTEX_REQUEUE || op == FUTEX_CMP_REQUEUE)

  		val2 = (int) (unsigned long) utime;

  	return do_futex(uaddr, op, val, timeout, uaddr2, val2, val3);

  }