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#include <linux/syscalls.h>
15
16#include <asm/uaccess.h>
17
18
19/*
20 * Fetch a robust-list pointer. Bit 0 signals PI futexes:
21 */
22static inline int
23fetch_robust_entry(compat_uptr_t *uentry, struct robust_list __user **entry,
24		   compat_uptr_t __user *head, unsigned int *pi)
25{
26	if (get_user(*uentry, head))
27		return -EFAULT;
28
29	*entry = compat_ptr((*uentry) & ~1);
30	*pi = (unsigned int)(*uentry) & 1;
31
32	return 0;
33}
34
35static void __user *futex_uaddr(struct robust_list __user *entry,
36				compat_long_t futex_offset)
37{
38	compat_uptr_t base = ptr_to_compat(entry);
39	void __user *uaddr = compat_ptr(base + futex_offset);
40
41	return uaddr;
42}
43
44/*
45 * Walk curr->robust_list (very carefully, it's a userspace list!)
46 * and mark any locks found there dead, and notify any waiters.
47 *
48 * We silently return on any sign of list-walking problem.
49 */
50void compat_exit_robust_list(struct task_struct *curr)
51{
52	struct compat_robust_list_head __user *head = curr->compat_robust_list;
53	struct robust_list __user *entry, *next_entry, *pending;
54	unsigned int limit = ROBUST_LIST_LIMIT, pi, pip;
55	unsigned int uninitialized_var(next_pi);
56	compat_uptr_t uentry, next_uentry, upending;
57	compat_long_t futex_offset;
58	int rc;
59
60	if (!futex_cmpxchg_enabled)
61		return;
62
63	/*
64	 * Fetch the list head (which was registered earlier, via
65	 * sys_set_robust_list()):
66	 */
67	if (fetch_robust_entry(&uentry, &entry, &head->list.next, &pi))
68		return;
69	/*
70	 * Fetch the relative futex offset:
71	 */
72	if (get_user(futex_offset, &head->futex_offset))
73		return;
74	/*
75	 * Fetch any possibly pending lock-add first, and handle it
76	 * if it exists:
77	 */
78	if (fetch_robust_entry(&upending, &pending,
79			       &head->list_op_pending, &pip))
80		return;
81
82	next_entry = NULL;	/* avoid warning with gcc */
83	while (entry != (struct robust_list __user *) &head->list) {
84		/*
85		 * Fetch the next entry in the list before calling
86		 * handle_futex_death:
87		 */
88		rc = fetch_robust_entry(&next_uentry, &next_entry,
89			(compat_uptr_t __user *)&entry->next, &next_pi);
90		/*
91		 * A pending lock might already be on the list, so
92		 * dont process it twice:
93		 */
94		if (entry != pending) {
95			void __user *uaddr = futex_uaddr(entry, futex_offset);
96
97			if (handle_futex_death(uaddr, curr, pi))
98				return;
99		}
100		if (rc)
101			return;
102		uentry = next_uentry;
103		entry = next_entry;
104		pi = next_pi;
105		/*
106		 * Avoid excessively long or circular lists:
107		 */
108		if (!--limit)
109			break;
110
111		cond_resched();
112	}
113	if (pending) {
114		void __user *uaddr = futex_uaddr(pending, futex_offset);
115
116		handle_futex_death(uaddr, curr, pip);
117	}
118}
119
120COMPAT_SYSCALL_DEFINE2(set_robust_list,
121		struct compat_robust_list_head __user *, head,
122		compat_size_t, len)
123{
124	if (!futex_cmpxchg_enabled)
125		return -ENOSYS;
126
127	if (unlikely(len != sizeof(*head)))
128		return -EINVAL;
129
130	current->compat_robust_list = head;
131
132	return 0;
133}
134
135COMPAT_SYSCALL_DEFINE3(get_robust_list, int, pid,
136			compat_uptr_t __user *, head_ptr,
137			compat_size_t __user *, len_ptr)
138{
139	struct compat_robust_list_head __user *head;
140	unsigned long ret;
141	struct task_struct *p;
142
143	if (!futex_cmpxchg_enabled)
144		return -ENOSYS;
145
146	rcu_read_lock();
147
148	ret = -ESRCH;
149	if (!pid)
150		p = current;
151	else {
152		p = find_task_by_vpid(pid);
153		if (!p)
154			goto err_unlock;
155	}
156
157	ret = -EPERM;
158	if (!ptrace_may_access(p, PTRACE_MODE_READ_REALCREDS))
159		goto err_unlock;
160
161	head = p->compat_robust_list;
162	rcu_read_unlock();
163
164	if (put_user(sizeof(*head), len_ptr))
165		return -EFAULT;
166	return put_user(ptr_to_compat(head), head_ptr);
167
168err_unlock:
169	rcu_read_unlock();
170
171	return ret;
172}
173
174COMPAT_SYSCALL_DEFINE6(futex, u32 __user *, uaddr, int, op, u32, val,
175		struct compat_timespec __user *, utime, u32 __user *, uaddr2,
176		u32, val3)
177{
178	struct timespec ts;
179	ktime_t t, *tp = NULL;
180	int val2 = 0;
181	int cmd = op & FUTEX_CMD_MASK;
182
183	if (utime && (cmd == FUTEX_WAIT || cmd == FUTEX_LOCK_PI ||
184		      cmd == FUTEX_WAIT_BITSET ||
185		      cmd == FUTEX_WAIT_REQUEUE_PI)) {
186		if (compat_get_timespec(&ts, utime))
187			return -EFAULT;
188		if (!timespec_valid(&ts))
189			return -EINVAL;
190
191		t = timespec_to_ktime(ts);
192		if (cmd == FUTEX_WAIT)
193			t = ktime_add_safe(ktime_get(), t);
194		tp = &t;
195	}
196	if (cmd == FUTEX_REQUEUE || cmd == FUTEX_CMP_REQUEUE ||
197	    cmd == FUTEX_CMP_REQUEUE_PI || cmd == FUTEX_WAKE_OP)
198		val2 = (int) (unsigned long) utime;
199
200	return do_futex(uaddr, op, val, tp, uaddr2, val2, val3);
201}
202