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