1/*
  2 * linux/kernel/futex_compat.c
  3 *
  4 * Futex compatibililty routines.
  5 *
  6 * Copyright 2006, Red Hat, Inc., Ingo Molnar
  7 */
  8
  9#include <linux/linkage.h>
 10#include <linux/compat.h>
 11#include <linux/nsproxy.h>
 12#include <linux/futex.h>
 13#include <linux/ptrace.h>
 14
 15#include <asm/uaccess.h>
 16
 17
 18/*
 19 * Fetch a robust-list pointer. Bit 0 signals PI futexes:
 20 */
 21static inline int
 22fetch_robust_entry(compat_uptr_t *uentry, struct robust_list __user **entry,
 23		   compat_uptr_t __user *head, unsigned int *pi)
 24{
 25	if (get_user(*uentry, head))
 26		return -EFAULT;
 27
 28	*entry = compat_ptr((*uentry) & ~1);
 29	*pi = (unsigned int)(*uentry) & 1;
 30
 31	return 0;
 32}
 33
 34static void __user *futex_uaddr(struct robust_list __user *entry,
 35				compat_long_t futex_offset)
 36{
 37	compat_uptr_t base = ptr_to_compat(entry);
 38	void __user *uaddr = compat_ptr(base + futex_offset);
 39
 40	return uaddr;
 41}
 42
 43/*
 44 * Walk curr->robust_list (very carefully, it's a userspace list!)
 45 * and mark any locks found there dead, and notify any waiters.
 46 *
 47 * We silently return on any sign of list-walking problem.
 48 */
 49void compat_exit_robust_list(struct task_struct *curr)
 50{
 51	struct compat_robust_list_head __user *head = curr->compat_robust_list;
 52	struct robust_list __user *entry, *next_entry, *pending;
 53	unsigned int limit = ROBUST_LIST_LIMIT, pi, pip;
 54	unsigned int uninitialized_var(next_pi);
 55	compat_uptr_t uentry, next_uentry, upending;
 56	compat_long_t futex_offset;
 57	int rc;
 58
 59	if (!futex_cmpxchg_enabled)
 60		return;
 61
 62	/*
 63	 * Fetch the list head (which was registered earlier, via
 64	 * sys_set_robust_list()):
 65	 */
 66	if (fetch_robust_entry(&uentry, &entry, &head->list.next, &pi))
 67		return;
 68	/*
 69	 * Fetch the relative futex offset:
 70	 */
 71	if (get_user(futex_offset, &head->futex_offset))
 72		return;
 73	/*
 74	 * Fetch any possibly pending lock-add first, and handle it
 75	 * if it exists:
 76	 */
 77	if (fetch_robust_entry(&upending, &pending,
 78			       &head->list_op_pending, &pip))
 79		return;
 80
 81	next_entry = NULL;	/* avoid warning with gcc */
 82	while (entry != (struct robust_list __user *) &head->list) {
 83		/*
 84		 * Fetch the next entry in the list before calling
 85		 * handle_futex_death:
 86		 */
 87		rc = fetch_robust_entry(&next_uentry, &next_entry,
 88			(compat_uptr_t __user *)&entry->next, &next_pi);
 89		/*
 90		 * A pending lock might already be on the list, so
 91		 * dont process it twice:
 92		 */
 93		if (entry != pending) {
 94			void __user *uaddr = futex_uaddr(entry, futex_offset);
 95
 96			if (handle_futex_death(uaddr, curr, pi))
 97				return;
 98		}
 99		if (rc)
100			return;
101		uentry = next_uentry;
102		entry = next_entry;
103		pi = next_pi;
104		/*
105		 * Avoid excessively long or circular lists:
106		 */
107		if (!--limit)
108			break;
109
110		cond_resched();
111	}
112	if (pending) {
113		void __user *uaddr = futex_uaddr(pending, futex_offset);
114
115		handle_futex_death(uaddr, curr, pip);
116	}
117}
118
119asmlinkage long
120compat_sys_set_robust_list(struct compat_robust_list_head __user *head,
121			   compat_size_t len)
122{
123	if (!futex_cmpxchg_enabled)
124		return -ENOSYS;
125
126	if (unlikely(len != sizeof(*head)))
127		return -EINVAL;
128
129	current->compat_robust_list = head;
130
131	return 0;
132}
133
134asmlinkage long
135compat_sys_get_robust_list(int pid, compat_uptr_t __user *head_ptr,
136			   compat_size_t __user *len_ptr)
137{
138	struct compat_robust_list_head __user *head;
139	unsigned long ret;
140	struct task_struct *p;
141
142	if (!futex_cmpxchg_enabled)
143		return -ENOSYS;
144
145	WARN_ONCE(1, "deprecated: get_robust_list will be deleted in 2013.\n");
146
147	rcu_read_lock();
148
149	ret = -ESRCH;
150	if (!pid)
151		p = current;
152	else {
153		p = find_task_by_vpid(pid);
154		if (!p)
155			goto err_unlock;
156	}
157
158	ret = -EPERM;
159	if (!ptrace_may_access(p, PTRACE_MODE_READ))
160		goto err_unlock;
161
162	head = p->compat_robust_list;
163	rcu_read_unlock();
164
165	if (put_user(sizeof(*head), len_ptr))
166		return -EFAULT;
167	return put_user(ptr_to_compat(head), head_ptr);
168
169err_unlock:
170	rcu_read_unlock();
171
172	return ret;
173}
174
175asmlinkage long compat_sys_futex(u32 __user *uaddr, int op, u32 val,
176		struct compat_timespec __user *utime, u32 __user *uaddr2,
177		u32 val3)
178{
179	struct timespec ts;
180	ktime_t t, *tp = NULL;
181	int val2 = 0;
182	int cmd = op & FUTEX_CMD_MASK;
183
184	if (utime && (cmd == FUTEX_WAIT || cmd == FUTEX_LOCK_PI ||
185		      cmd == FUTEX_WAIT_BITSET ||
186		      cmd == FUTEX_WAIT_REQUEUE_PI)) {
187		if (get_compat_timespec(&ts, utime))
188			return -EFAULT;
189		if (!timespec_valid(&ts))
190			return -EINVAL;
191
192		t = timespec_to_ktime(ts);
193		if (cmd == FUTEX_WAIT)
194			t = ktime_add_safe(ktime_get(), t);
195		tp = &t;
196	}
197	if (cmd == FUTEX_REQUEUE || cmd == FUTEX_CMP_REQUEUE ||
198	    cmd == FUTEX_CMP_REQUEUE_PI || cmd == FUTEX_WAKE_OP)
199		val2 = (int) (unsigned long) utime;
200
201	return do_futex(uaddr, op, val, tp, uaddr2, val2, val3);
202}