/*
   * 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/nsproxy.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, unsigned int *pi)

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

  static void __user *futex_uaddr(struct robust_list __user *entry,

  				compat_long_t futex_offset)
  {
  	compat_uptr_t base = ptr_to_compat(entry);
  	void __user *uaddr = compat_ptr(base + futex_offset);
  
  	return uaddr;
  }

  /*
   * 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, *next_entry, *pending;

  	unsigned int limit = ROBUST_LIST_LIMIT, pi, pip;
  	unsigned int uninitialized_var(next_pi);

  	compat_uptr_t uentry, next_uentry, upending;

  	compat_long_t futex_offset;

  	int rc;

  	if (!futex_cmpxchg_enabled)
  		return;

  	/*
  	 * 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;

  	next_entry = NULL;	/* avoid warning with gcc */

  	while (entry != (struct robust_list __user *) &head->list) {

  		/*

  		 * Fetch the next entry in the list before calling
  		 * handle_futex_death:
  		 */
  		rc = fetch_robust_entry(&next_uentry, &next_entry,
  			(compat_uptr_t __user *)&entry->next, &next_pi);
  		/*

  		 * A pending lock might already be on the list, so
  		 * dont process it twice:
  		 */

  		if (entry != pending) {
  			void __user *uaddr = futex_uaddr(entry, futex_offset);

  			if (handle_futex_death(uaddr, curr, pi))
  				return;
  		}

  		if (rc)

  			return;

  		uentry = next_uentry;
  		entry = next_entry;
  		pi = next_pi;

  		/*
  		 * Avoid excessively long or circular lists:
  		 */
  		if (!--limit)
  			break;
  
  		cond_resched();
  	}

  	if (pending) {
  		void __user *uaddr = futex_uaddr(pending, futex_offset);
  
  		handle_futex_death(uaddr, curr, pip);
  	}

  }
  
  asmlinkage long
  compat_sys_set_robust_list(struct compat_robust_list_head __user *head,
  			   compat_size_t len)
  {

  	if (!futex_cmpxchg_enabled)
  		return -ENOSYS;

  	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;

  	const struct cred *cred = current_cred(), *pcred;

  	if (!futex_cmpxchg_enabled)
  		return -ENOSYS;

  	if (!pid)
  		head = current->compat_robust_list;
  	else {
  		struct task_struct *p;
  
  		ret = -ESRCH;

  		rcu_read_lock();

  		p = find_task_by_vpid(pid);

  		if (!p)
  			goto err_unlock;
  		ret = -EPERM;

  		pcred = __task_cred(p);

  		/* If victim is in different user_ns, then uids are not
  		   comparable, so we must have CAP_SYS_PTRACE */
  		if (cred->user->user_ns != pcred->user->user_ns) {
  			if (!ns_capable(pcred->user->user_ns, CAP_SYS_PTRACE))
  				goto err_unlock;
  			goto ok;
  		}
  		/* If victim is in same user_ns, then uids are comparable */

  		if (cred->euid != pcred->euid &&
  		    cred->euid != pcred->uid &&

  		    !ns_capable(pcred->user->user_ns, CAP_SYS_PTRACE))

  			goto err_unlock;

  ok:

  		head = p->compat_robust_list;

  		rcu_read_unlock();

  	}
  
  	if (put_user(sizeof(*head), len_ptr))
  		return -EFAULT;
  	return put_user(ptr_to_compat(head), head_ptr);
  
  err_unlock:

  	rcu_read_unlock();

  
  	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 ts;
  	ktime_t t, *tp = NULL;

  	int val2 = 0;

  	int cmd = op & FUTEX_CMD_MASK;

  	if (utime && (cmd == FUTEX_WAIT || cmd == FUTEX_LOCK_PI ||

  		      cmd == FUTEX_WAIT_BITSET ||
  		      cmd == FUTEX_WAIT_REQUEUE_PI)) {

  		if (get_compat_timespec(&ts, utime))

  			return -EFAULT;

  		if (!timespec_valid(&ts))

  			return -EINVAL;

  
  		t = timespec_to_ktime(ts);

  		if (cmd == FUTEX_WAIT)

  			t = ktime_add_safe(ktime_get(), t);

  		tp = &t;

  	}

  	if (cmd == FUTEX_REQUEUE || cmd == FUTEX_CMP_REQUEUE ||
  	    cmd == FUTEX_CMP_REQUEUE_PI || cmd == FUTEX_WAKE_OP)

  		val2 = (int) (unsigned long) utime;

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

  }