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 #include <linux/vs_cvirt.h>
  13
  14 #include <asm/uaccess.h>
  15
  16 /*
  17  * Walk curr->robust_list (very carefully, it's a userspace list!)
  18  * and mark any locks found there dead, and notify any waiters.
  19  *
  20  * We silently return on any sign of list-walking problem.
  21  */
  22 void compat_exit_robust_list(struct task_struct *curr)
  23 {
  24         struct compat_robust_list_head __user *head = curr->compat_robust_list;
  25         struct robust_list __user *entry, *pending;
  26         compat_uptr_t uentry, upending;
  27         unsigned int limit = ROBUST_LIST_LIMIT;
  28         compat_long_t futex_offset;
  29
  30         /*
  31          * Fetch the list head (which was registered earlier, via
  32          * sys_set_robust_list()):
  33          */
  34         if (get_user(uentry, &head->list.next))
  35                 return;
  36         entry = compat_ptr(uentry);
  37         /*
  38          * Fetch the relative futex offset:
  39          */
  40         if (get_user(futex_offset, &head->futex_offset))
  41                 return;
  42         /*
  43          * Fetch any possibly pending lock-add first, and handle it
  44          * if it exists:
  45          */
  46         if (get_user(upending, &head->list_op_pending))
  47                 return;
  48         pending = compat_ptr(upending);
  49         if (upending)
  50                 handle_futex_death((void *)pending + futex_offset, curr);
  51
  52         while (compat_ptr(uentry) != &head->list) {
  53                 /*
  54                  * A pending lock might already be on the list, so
  55                  * dont process it twice:
  56                  */
  57                 if (entry != pending)
  58                         if (handle_futex_death((void *)entry + futex_offset,
  59                                                 curr))
  60                                 return;
  61
  62                 /*
  63                  * Fetch the next entry in the list:
  64                  */
  65                 if (get_user(uentry, (compat_uptr_t *)&entry->next))
  66                         return;
  67                 entry = compat_ptr(uentry);
  68                 /*
  69                  * Avoid excessively long or circular lists:
  70                  */
  71                 if (!--limit)
  72                         break;
  73
  74                 cond_resched();
  75         }
  76 }
  77
  78 asmlinkage long
  79 compat_sys_set_robust_list(struct compat_robust_list_head __user *head,
  80                            compat_size_t len)
  81 {
  82         if (unlikely(len != sizeof(*head)))
  83                 return -EINVAL;
  84
  85         current->compat_robust_list = head;
  86
  87         return 0;
  88 }
  89
  90 asmlinkage long
  91 compat_sys_get_robust_list(int pid, compat_uptr_t *head_ptr,
  92                            compat_size_t __user *len_ptr)
  93 {
  94         struct compat_robust_list_head *head;
  95         unsigned long ret;
  96
  97         if (!pid)
  98                 head = current->compat_robust_list;
  99         else {
 100                 struct task_struct *p;
 101
 102                 ret = -ESRCH;
 103                 read_lock(&tasklist_lock);
 104                 p = find_task_by_pid(pid);
 105                 if (!p)
 106                         goto err_unlock;
 107                 ret = -EPERM;
 108                 if ((current->euid != p->euid) && (current->euid != p->uid) &&
 109                                 !capable(CAP_SYS_PTRACE))
 110                         goto err_unlock;
 111                 head = p->compat_robust_list;
 112                 read_unlock(&tasklist_lock);
 113         }
 114
 115         if (put_user(sizeof(*head), len_ptr))
 116                 return -EFAULT;
 117         return put_user(ptr_to_compat(head), head_ptr);
 118
 119 err_unlock:
 120         read_unlock(&tasklist_lock);
 121
 122         return ret;
 123 }
 124
 125 asmlinkage long compat_sys_futex(u32 __user *uaddr, int op, u32 val,
 126                 struct compat_timespec __user *utime, u32 __user *uaddr2,
 127                 u32 val3)
 128 {
 129         struct timespec t;
 130         unsigned long timeout = MAX_SCHEDULE_TIMEOUT;
 131         int val2 = 0;
 132
 133         if (utime && (op == FUTEX_WAIT)) {
 134                 if (get_compat_timespec(&t, utime))
 135                         return -EFAULT;
 136                 if (!timespec_valid(&t))
 137                         return -EINVAL;
 138                 timeout = timespec_to_jiffies(&t) + 1;
 139         }
 140         if (op >= FUTEX_REQUEUE)
 141                 val2 = (int) (unsigned long) utime;
 142
 143         return do_futex((unsigned long)uaddr, op, val, timeout,
 144                         (unsigned long)uaddr2, val2, val3);
 145 }