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 static void __user *futex_uaddr(struct robust_list *entry,
  33                                 compat_long_t futex_offset)
  34 {
  35         compat_uptr_t base = ptr_to_compat(entry);
  36         void __user *uaddr = compat_ptr(base + futex_offset);
  37
  38         return uaddr;
  39 }
  40
  41 /*
  42  * Walk curr->robust_list (very carefully, it's a userspace list!)
  43  * and mark any locks found there dead, and notify any waiters.
  44  *
  45  * We silently return on any sign of list-walking problem.
  46  */
  47 void compat_exit_robust_list(struct task_struct *curr)
  48 {
  49         struct compat_robust_list_head __user *head = curr->compat_robust_list;
  50         struct robust_list __user *entry, *pending;
  51         unsigned int limit = ROBUST_LIST_LIMIT, pi, pip;
  52         compat_uptr_t uentry, upending;
  53         compat_long_t futex_offset;
  54
  55         /*
  56          * Fetch the list head (which was registered earlier, via
  57          * sys_set_robust_list()):
  58          */
  59         if (fetch_robust_entry(&uentry, &entry, &head->list.next, &pi))
  60                 return;
  61         /*
  62          * Fetch the relative futex offset:
  63          */
  64         if (get_user(futex_offset, &head->futex_offset))
  65                 return;
  66         /*
  67          * Fetch any possibly pending lock-add first, and handle it
  68          * if it exists:
  69          */
  70         if (fetch_robust_entry(&upending, &pending,
  71                                &head->list_op_pending, &pip))
  72                 return;
  73         if (pending) {
  74                 void __user *uaddr = futex_uaddr(pending,
  75                                                  futex_offset);
  76                 handle_futex_death(uaddr, curr, pip);
  77         }
  78
  79         while (entry != (struct robust_list __user *) &head->list) {
  80                 /*
  81                  * A pending lock might already be on the list, so
  82                  * dont process it twice:
  83                  */
  84                 if (entry != pending) {
  85                         void __user *uaddr = futex_uaddr(entry,
  86                                                          futex_offset);
  87                         if (handle_futex_death(uaddr, curr, pi))
  88                                 return;
  89                 }
  90
  91                 /*
  92                  * Fetch the next entry in the list:
  93                  */
  94                 if (fetch_robust_entry(&uentry, &entry,
  95                                        (compat_uptr_t __user *)&entry->next, &pi))
  96                         return;
  97                 /*
  98                  * Avoid excessively long or circular lists:
  99                  */
 100                 if (!--limit)
 101                         break;
 102
 103                 cond_resched();
 104         }
 105 }
 106
 107 asmlinkage long
 108 compat_sys_set_robust_list(struct compat_robust_list_head __user *head,
 109                            compat_size_t len)
 110 {
 111         if (unlikely(len != sizeof(*head)))
 112                 return -EINVAL;
 113
 114         current->compat_robust_list = head;
 115
 116         return 0;
 117 }
 118
 119 asmlinkage long
 120 compat_sys_get_robust_list(int pid, compat_uptr_t __user *head_ptr,
 121                            compat_size_t __user *len_ptr)
 122 {
 123         struct compat_robust_list_head __user *head;
 124         unsigned long ret;
 125
 126         if (!pid)
 127                 head = current->compat_robust_list;
 128         else {
 129                 struct task_struct *p;
 130
 131                 ret = -ESRCH;
 132                 read_lock(&tasklist_lock);
 133                 p = find_task_by_pid(pid);
 134                 if (!p)
 135                         goto err_unlock;
 136                 ret = -EPERM;
 137                 if ((current->euid != p->euid) && (current->euid != p->uid) &&
 138                                 !capable(CAP_SYS_PTRACE))
 139                         goto err_unlock;
 140                 head = p->compat_robust_list;
 141                 read_unlock(&tasklist_lock);
 142         }
 143
 144         if (put_user(sizeof(*head), len_ptr))
 145                 return -EFAULT;
 146         return put_user(ptr_to_compat(head), head_ptr);
 147
 148 err_unlock:
 149         read_unlock(&tasklist_lock);
 150
 151         return ret;
 152 }
 153
 154 asmlinkage long compat_sys_futex(u32 __user *uaddr, int op, u32 val,
 155                 struct compat_timespec __user *utime, u32 __user *uaddr2,
 156                 u32 val3)
 157 {
 158         struct timespec ts;
 159         ktime_t t, *tp = NULL;
 160         int val2 = 0;
 161         int cmd = op & FUTEX_CMD_MASK;
 162
 163         if (utime && (cmd == FUTEX_WAIT || cmd == FUTEX_LOCK_PI)) {
 164                 if (get_compat_timespec(&ts, utime))
 165                         return -EFAULT;
 166                 if (!timespec_valid(&ts))
 167                         return -EINVAL;
 168
 169                 t = timespec_to_ktime(ts);
 170                 if (cmd == FUTEX_WAIT)
 171                         t = ktime_add(ktime_get(), t);
 172                 tp = &t;
 173         }
 174         if (cmd == FUTEX_REQUEUE || cmd == FUTEX_CMP_REQUEUE)
 175                 val2 = (int) (unsigned long) utime;
 176
 177         return do_futex(uaddr, op, val, tp, uaddr2, val2, val3);
 178 }