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, *next_entry, *pending;
  42         unsigned int limit = ROBUST_LIST_LIMIT, pi, next_pi, pip;
  43         compat_uptr_t uentry, next_uentry, upending;
  44         compat_long_t futex_offset;
  45         int rc;
  46
  47         /*
  48          * Fetch the list head (which was registered earlier, via
  49          * sys_set_robust_list()):
  50          */
  51         if (fetch_robust_entry(&uentry, &entry, &head->list.next, &pi))
  52                 return;
  53         /*
  54          * Fetch the relative futex offset:
  55          */
  56         if (get_user(futex_offset, &head->futex_offset))
  57                 return;
  58         /*
  59          * Fetch any possibly pending lock-add first, and handle it
  60          * if it exists:
  61          */
  62         if (fetch_robust_entry(&upending, &pending,
  63                                &head->list_op_pending, &pip))
  64                 return;
  65
  66         next_entry = NULL;      /* avoid warning with gcc */
  67         while (entry != (struct robust_list __user *) &head->list) {
  68                 /*
  69                  * Fetch the next entry in the list before calling
  70                  * handle_futex_death:
  71                  */
  72                 rc = fetch_robust_entry(&next_uentry, &next_entry,
  73                         (compat_uptr_t __user *)&entry->next, &next_pi);
  74                 /*
  75                  * A pending lock might already be on the list, so
  76                  * dont process it twice:
  77                  */
  78                 if (entry != pending)
  79                         if (handle_futex_death((void __user *)entry + futex_offset,
  80                                                 curr, pi))
  81                                 return;
  82
  83                 if (rc)
  84                         return;
  85                 uentry = next_uentry;
  86                 entry = next_entry;
  87                 pi = next_pi;
  88                 /*
  89                  * Avoid excessively long or circular lists:
  90                  */
  91                 if (!--limit)
  92                         break;
  93
  94                 cond_resched();
  95         }
  96         if (pending)
  97                 handle_futex_death((void __user *)pending + futex_offset,
  98                                    curr, pip);
  99 }
 100
 101 asmlinkage long
 102 compat_sys_set_robust_list(struct compat_robust_list_head __user *head,
 103                            compat_size_t len)
 104 {
 105         if (unlikely(len != sizeof(*head)))
 106                 return -EINVAL;
 107
 108         current->compat_robust_list = head;
 109
 110         return 0;
 111 }
 112
 113 asmlinkage long
 114 compat_sys_get_robust_list(int pid, compat_uptr_t __user *head_ptr,
 115                            compat_size_t __user *len_ptr)
 116 {
 117         struct compat_robust_list_head __user *head;
 118         unsigned long ret;
 119
 120         if (!pid)
 121                 head = current->compat_robust_list;
 122         else {
 123                 struct task_struct *p;
 124
 125                 ret = -ESRCH;
 126                 read_lock(&tasklist_lock);
 127                 p = find_task_by_pid(pid);
 128                 if (!p)
 129                         goto err_unlock;
 130                 ret = -EPERM;
 131                 if ((current->euid != p->euid) && (current->euid != p->uid) &&
 132                                 !capable(CAP_SYS_PTRACE))
 133                         goto err_unlock;
 134                 head = p->compat_robust_list;
 135                 read_unlock(&tasklist_lock);
 136         }
 137
 138         if (put_user(sizeof(*head), len_ptr))
 139                 return -EFAULT;
 140         return put_user(ptr_to_compat(head), head_ptr);
 141
 142 err_unlock:
 143         read_unlock(&tasklist_lock);
 144
 145         return ret;
 146 }
 147
 148 asmlinkage long compat_sys_futex(u32 __user *uaddr, int op, u32 val,
 149                 struct compat_timespec __user *utime, u32 __user *uaddr2,
 150                 u32 val3)
 151 {
 152         struct timespec ts;
 153         ktime_t t, *tp = NULL;
 154         int val2 = 0;
 155         int cmd = op & FUTEX_CMD_MASK;
 156
 157         if (utime && (cmd == FUTEX_WAIT || cmd == FUTEX_LOCK_PI)) {
 158                 if (get_compat_timespec(&ts, utime))
 159                         return -EFAULT;
 160                 if (!timespec_valid(&ts))
 161                         return -EINVAL;
 162
 163                 t = timespec_to_ktime(ts);
 164                 if (cmd == FUTEX_WAIT)
 165                         t = ktime_add(ktime_get(), t);
 166                 tp = &t;
 167         }
 168         if (cmd == FUTEX_REQUEUE || cmd == FUTEX_CMP_REQUEUE)
 169                 val2 = (int) (unsigned long) utime;
 170
 171         return do_futex(uaddr, op, val, tp, uaddr2, val2, val3);
 172 }