Root/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#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))
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 (get_compat_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

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