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/futex.h>
12
13#include <asm/uaccess.h>
14
15
16/*
17 * Fetch a robust-list pointer. Bit 0 signals PI futexes:
18 */
19static inline int
20fetch_robust_entry(compat_uptr_t *uentry, struct robust_list __user **entry,
21		   compat_uptr_t __user *head, int *pi)
22{
23	if (get_user(*uentry, head))
24		return -EFAULT;
25
26	*entry = compat_ptr((*uentry) & ~1);
27	*pi = (unsigned int)(*uentry) & 1;
28
29	return 0;
30}
31
32/*
33 * Walk curr->robust_list (very carefully, it's a userspace list!)
34 * and mark any locks found there dead, and notify any waiters.
35 *
36 * We silently return on any sign of list-walking problem.
37 */
38void compat_exit_robust_list(struct task_struct *curr)
39{
40	struct compat_robust_list_head __user *head = curr->compat_robust_list;
41	struct robust_list __user *entry, *pending;
42	unsigned int limit = ROBUST_LIST_LIMIT, pi, pip;
43	compat_uptr_t uentry, upending;
44	compat_long_t futex_offset;
45
46	/*
47	 * Fetch the list head (which was registered earlier, via
48	 * sys_set_robust_list()):
49	 */
50	if (fetch_robust_entry(&uentry, &entry, &head->list.next, &pi))
51		return;
52	/*
53	 * Fetch the relative futex offset:
54	 */
55	if (get_user(futex_offset, &head->futex_offset))
56		return;
57	/*
58	 * Fetch any possibly pending lock-add first, and handle it
59	 * if it exists:
60	 */
61	if (fetch_robust_entry(&upending, &pending,
62			       &head->list_op_pending, &pip))
63		return;
64	if (upending)
65		handle_futex_death((void __user *)pending + futex_offset, curr, pip);
66
67	while (compat_ptr(uentry) != &head->list) {
68		/*
69		 * A pending lock might already be on the list, so
70		 * dont process it twice:
71		 */
72		if (entry != pending)
73			if (handle_futex_death((void __user *)entry + futex_offset,
74						curr, pi))
75				return;
76
77		/*
78		 * Fetch the next entry in the list:
79		 */
80		if (fetch_robust_entry(&uentry, &entry,
81				       (compat_uptr_t __user *)&entry->next, &pi))
82			return;
83		/*
84		 * Avoid excessively long or circular lists:
85		 */
86		if (!--limit)
87			break;
88
89		cond_resched();
90	}
91}
92
93asmlinkage long
94compat_sys_set_robust_list(struct compat_robust_list_head __user *head,
95			   compat_size_t len)
96{
97	if (unlikely(len != sizeof(*head)))
98		return -EINVAL;
99
100	current->compat_robust_list = head;
101
102	return 0;
103}
104
105asmlinkage long
106compat_sys_get_robust_list(int pid, compat_uptr_t __user *head_ptr,
107			   compat_size_t __user *len_ptr)
108{
109	struct compat_robust_list_head __user *head;
110	unsigned long ret;
111
112	if (!pid)
113		head = current->compat_robust_list;
114	else {
115		struct task_struct *p;
116
117		ret = -ESRCH;
118		read_lock(&tasklist_lock);
119		p = find_task_by_pid(pid);
120		if (!p)
121			goto err_unlock;
122		ret = -EPERM;
123		if ((current->euid != p->euid) && (current->euid != p->uid) &&
124				!capable(CAP_SYS_PTRACE))
125			goto err_unlock;
126		head = p->compat_robust_list;
127		read_unlock(&tasklist_lock);
128	}
129
130	if (put_user(sizeof(*head), len_ptr))
131		return -EFAULT;
132	return put_user(ptr_to_compat(head), head_ptr);
133
134err_unlock:
135	read_unlock(&tasklist_lock);
136
137	return ret;
138}
139
140asmlinkage long compat_sys_futex(u32 __user *uaddr, int op, u32 val,
141		struct compat_timespec __user *utime, u32 __user *uaddr2,
142		u32 val3)
143{
144	struct timespec ts;
145	ktime_t t, *tp = NULL;
146	int val2 = 0;
147	int cmd = op & FUTEX_CMD_MASK;
148
149	if (utime && (cmd == FUTEX_WAIT || cmd == FUTEX_LOCK_PI)) {
150		if (get_compat_timespec(&ts, utime))
151			return -EFAULT;
152		if (!timespec_valid(&ts))
153			return -EINVAL;
154
155		t = timespec_to_ktime(ts);
156		if (cmd == FUTEX_WAIT)
157			t = ktime_add(ktime_get(), t);
158		tp = &t;
159	}
160	if (cmd == FUTEX_REQUEUE || cmd == FUTEX_CMP_REQUEUE)
161		val2 = (int) (unsigned long) utime;
162
163	return do_futex(uaddr, op, val, tp, uaddr2, val2, val3);
164}
165