Merge branch 'for-next' into for-linus
[linux-2.6.git] / kernel / futex_compat.c
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
14 #include <asm/uaccess.h>
15
16
17 /*
18  * Fetch a robust-list pointer. Bit 0 signals PI futexes:
19  */
20 static inline int
21 fetch_robust_entry(compat_uptr_t *uentry, struct robust_list __user **entry,
22                    compat_uptr_t __user *head, int *pi)
23 {
24         if (get_user(*uentry, head))
25                 return -EFAULT;
26
27         *entry = compat_ptr((*uentry) & ~1);
28         *pi = (unsigned int)(*uentry) & 1;
29
30         return 0;
31 }
32
33 static void __user *futex_uaddr(struct robust_list __user *entry,
34                                 compat_long_t futex_offset)
35 {
36         compat_uptr_t base = ptr_to_compat(entry);
37         void __user *uaddr = compat_ptr(base + futex_offset);
38
39         return uaddr;
40 }
41
42 /*
43  * Walk curr->robust_list (very carefully, it's a userspace list!)
44  * and mark any locks found there dead, and notify any waiters.
45  *
46  * We silently return on any sign of list-walking problem.
47  */
48 void compat_exit_robust_list(struct task_struct *curr)
49 {
50         struct compat_robust_list_head __user *head = curr->compat_robust_list;
51         struct robust_list __user *entry, *next_entry, *pending;
52         unsigned int limit = ROBUST_LIST_LIMIT, pi, next_pi, pip;
53         compat_uptr_t uentry, next_uentry, upending;
54         compat_long_t futex_offset;
55         int rc;
56
57         if (!futex_cmpxchg_enabled)
58                 return;
59
60         /*
61          * Fetch the list head (which was registered earlier, via
62          * sys_set_robust_list()):
63          */
64         if (fetch_robust_entry(&uentry, &entry, &head->list.next, &pi))
65                 return;
66         /*
67          * Fetch the relative futex offset:
68          */
69         if (get_user(futex_offset, &head->futex_offset))
70                 return;
71         /*
72          * Fetch any possibly pending lock-add first, and handle it
73          * if it exists:
74          */
75         if (fetch_robust_entry(&upending, &pending,
76                                &head->list_op_pending, &pip))
77                 return;
78
79         next_entry = NULL;      /* avoid warning with gcc */
80         while (entry != (struct robust_list __user *) &head->list) {
81                 /*
82                  * Fetch the next entry in the list before calling
83                  * handle_futex_death:
84                  */
85                 rc = fetch_robust_entry(&next_uentry, &next_entry,
86                         (compat_uptr_t __user *)&entry->next, &next_pi);
87                 /*
88                  * A pending lock might already be on the list, so
89                  * dont process it twice:
90                  */
91                 if (entry != pending) {
92                         void __user *uaddr = futex_uaddr(entry, futex_offset);
93
94                         if (handle_futex_death(uaddr, curr, pi))
95                                 return;
96                 }
97                 if (rc)
98                         return;
99                 uentry = next_uentry;
100                 entry = next_entry;
101                 pi = next_pi;
102                 /*
103                  * Avoid excessively long or circular lists:
104                  */
105                 if (!--limit)
106                         break;
107
108                 cond_resched();
109         }
110         if (pending) {
111                 void __user *uaddr = futex_uaddr(pending, futex_offset);
112
113                 handle_futex_death(uaddr, curr, pip);
114         }
115 }
116
117 asmlinkage long
118 compat_sys_set_robust_list(struct compat_robust_list_head __user *head,
119                            compat_size_t len)
120 {
121         if (!futex_cmpxchg_enabled)
122                 return -ENOSYS;
123
124         if (unlikely(len != sizeof(*head)))
125                 return -EINVAL;
126
127         current->compat_robust_list = head;
128
129         return 0;
130 }
131
132 asmlinkage long
133 compat_sys_get_robust_list(int pid, compat_uptr_t __user *head_ptr,
134                            compat_size_t __user *len_ptr)
135 {
136         struct compat_robust_list_head __user *head;
137         unsigned long ret;
138         const struct cred *cred = current_cred(), *pcred;
139
140         if (!futex_cmpxchg_enabled)
141                 return -ENOSYS;
142
143         if (!pid)
144                 head = current->compat_robust_list;
145         else {
146                 struct task_struct *p;
147
148                 ret = -ESRCH;
149                 rcu_read_lock();
150                 p = find_task_by_vpid(pid);
151                 if (!p)
152                         goto err_unlock;
153                 ret = -EPERM;
154                 pcred = __task_cred(p);
155                 if (cred->euid != pcred->euid &&
156                     cred->euid != pcred->uid &&
157                     !capable(CAP_SYS_PTRACE))
158                         goto err_unlock;
159                 head = p->compat_robust_list;
160                 rcu_read_unlock();
161         }
162
163         if (put_user(sizeof(*head), len_ptr))
164                 return -EFAULT;
165         return put_user(ptr_to_compat(head), head_ptr);
166
167 err_unlock:
168         rcu_read_unlock();
169
170         return ret;
171 }
172
173 asmlinkage long compat_sys_futex(u32 __user *uaddr, int op, u32 val,
174                 struct compat_timespec __user *utime, u32 __user *uaddr2,
175                 u32 val3)
176 {
177         struct timespec ts;
178         ktime_t t, *tp = NULL;
179         int val2 = 0;
180         int cmd = op & FUTEX_CMD_MASK;
181
182         if (utime && (cmd == FUTEX_WAIT || cmd == FUTEX_LOCK_PI ||
183                       cmd == FUTEX_WAIT_BITSET ||
184                       cmd == FUTEX_WAIT_REQUEUE_PI)) {
185                 if (get_compat_timespec(&ts, utime))
186                         return -EFAULT;
187                 if (!timespec_valid(&ts))
188                         return -EINVAL;
189
190                 t = timespec_to_ktime(ts);
191                 if (cmd == FUTEX_WAIT)
192                         t = ktime_add_safe(ktime_get(), t);
193                 tp = &t;
194         }
195         if (cmd == FUTEX_REQUEUE || cmd == FUTEX_CMP_REQUEUE ||
196             cmd == FUTEX_CMP_REQUEUE_PI || cmd == FUTEX_WAKE_OP)
197                 val2 = (int) (unsigned long) utime;
198
199         return do_futex(uaddr, op, val, tp, uaddr2, val2, val3);
200 }