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, u32 val,
 125                 struct compat_timespec __user *utime, u32 __user *uaddr2,
 126                 u32 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(uaddr, op, val, timeout, uaddr2, val2, val3);
 141 }