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 /*
  17  * Fetch a robust-list pointer. Bit 0 signals PI futexes:
  18  */
  19 static inline int
  20 fetch_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  */
  38 void 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
  93 asmlinkage long
  94 compat_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
 105 asmlinkage long
 106 compat_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
 134 err_unlock:
 135         read_unlock(&tasklist_lock);
 136
 137         return ret;
 138 }
 139
 140 asmlinkage 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
 148         if (utime && (op == FUTEX_WAIT || op == FUTEX_LOCK_PI)) {
 149                 if (get_compat_timespec(&ts, utime))
 150                         return -EFAULT;
 151                 if (!timespec_valid(&ts))
 152                         return -EINVAL;
 153
 154                 t = timespec_to_ktime(ts);
 155                 if (op == FUTEX_WAIT)
 156                         t = ktime_add(ktime_get(), t);
 157                 tp = &t;
 158         }
 159         if (op == FUTEX_REQUEUE || op == FUTEX_CMP_REQUEUE
 160             || op == FUTEX_CMP_REQUEUE_PI)
 161                 val2 = (int) (unsigned long) utime;
 162
 163         return do_futex(uaddr, op, val, tp, uaddr2, val2, val3);
 164 }