linux/kernel/futex_compat.c
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   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 t;
 145        unsigned long timeout = MAX_SCHEDULE_TIMEOUT;
 146        int val2 = 0;
 147
 148        if (utime && (op == FUTEX_WAIT || op == FUTEX_LOCK_PI)) {
 149                if (get_compat_timespec(&t, utime))
 150                        return -EFAULT;
 151                if (!timespec_valid(&t))
 152                        return -EINVAL;
 153                if (op == FUTEX_WAIT)
 154                        timeout = timespec_to_jiffies(&t) + 1;
 155                else {
 156                        timeout = t.tv_sec;
 157                        val2 = t.tv_nsec;
 158                }
 159        }
 160        if (op == FUTEX_REQUEUE || op == FUTEX_CMP_REQUEUE)
 161                val2 = (int) (unsigned long) utime;
 162
 163        return do_futex(uaddr, op, val, timeout, uaddr2, val2, val3);
 164}
 165