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/nsproxy.h>
  12 #include <linux/futex.h>
  13 #include <linux/ptrace.h>
  14
  15 #include <asm/uaccess.h>
  16
  17
  18 /*
  19  * Fetch a robust-list pointer. Bit 0 signals PI futexes:
  20  */
  21 static inline int
  22 fetch_robust_entry(compat_uptr_t *uentry, struct robust_list __user **entry,
  23                    compat_uptr_t __user *head, unsigned int *pi)
  24 {
  25         if (get_user(*uentry, head))
  26                 return -EFAULT;
  27
  28         *entry = compat_ptr((*uentry) & ~1);
  29         *pi = (unsigned int)(*uentry) & 1;
  30
  31         return 0;
  32 }
  33
  34 static void __user *futex_uaddr(struct robust_list __user *entry,
  35                                 compat_long_t futex_offset)
  36 {
  37         compat_uptr_t base = ptr_to_compat(entry);
  38         void __user *uaddr = compat_ptr(base + futex_offset);
  39
  40         return uaddr;
  41 }
  42
  43 /*
  44  * Walk curr->robust_list (very carefully, it's a userspace list!)
  45  * and mark any locks found there dead, and notify any waiters.
  46  *
  47  * We silently return on any sign of list-walking problem.
  48  */
  49 void compat_exit_robust_list(struct task_struct *curr)
  50 {
  51         struct compat_robust_list_head __user *head = curr->compat_robust_list;
  52         struct robust_list __user *entry, *next_entry, *pending;
  53         unsigned int limit = ROBUST_LIST_LIMIT, pi, pip;
  54         unsigned int uninitialized_var(next_pi);
  55         compat_uptr_t uentry, next_uentry, upending;
  56         compat_long_t futex_offset;
  57         int rc;
  58
  59         if (!futex_cmpxchg_enabled)
  60                 return;
  61
  62         /*
  63          * Fetch the list head (which was registered earlier, via
  64          * sys_set_robust_list()):
  65          */
  66         if (fetch_robust_entry(&uentry, &entry, &head->list.next, &pi))
  67                 return;
  68         /*
  69          * Fetch the relative futex offset:
  70          */
  71         if (get_user(futex_offset, &head->futex_offset))
  72                 return;
  73         /*
  74          * Fetch any possibly pending lock-add first, and handle it
  75          * if it exists:
  76          */
  77         if (fetch_robust_entry(&upending, &pending,
  78                                &head->list_op_pending, &pip))
  79                 return;
  80
  81         next_entry = NULL;      /* avoid warning with gcc */
  82         while (entry != (struct robust_list __user *) &head->list) {
  83                 /*
  84                  * Fetch the next entry in the list before calling
  85                  * handle_futex_death:
  86                  */
  87                 rc = fetch_robust_entry(&next_uentry, &next_entry,
  88                         (compat_uptr_t __user *)&entry->next, &next_pi);
  89                 /*
  90                  * A pending lock might already be on the list, so
  91                  * dont process it twice:
  92                  */
  93                 if (entry != pending) {
  94                         void __user *uaddr = futex_uaddr(entry, futex_offset);
  95
  96                         if (handle_futex_death(uaddr, curr, pi))
  97                                 return;
  98                 }
  99                 if (rc)
 100                         return;
 101                 uentry = next_uentry;
 102                 entry = next_entry;
 103                 pi = next_pi;
 104                 /*
 105                  * Avoid excessively long or circular lists:
 106                  */
 107                 if (!--limit)
 108                         break;
 109
 110                 cond_resched();
 111         }
 112         if (pending) {
 113                 void __user *uaddr = futex_uaddr(pending, futex_offset);
 114
 115                 handle_futex_death(uaddr, curr, pip);
 116         }
 117 }
 118
 119 asmlinkage long
 120 compat_sys_set_robust_list(struct compat_robust_list_head __user *head,
 121                            compat_size_t len)
 122 {
 123         if (!futex_cmpxchg_enabled)
 124                 return -ENOSYS;
 125
 126         if (unlikely(len != sizeof(*head)))
 127                 return -EINVAL;
 128
 129         current->compat_robust_list = head;
 130
 131         return 0;
 132 }
 133
 134 asmlinkage long
 135 compat_sys_get_robust_list(int pid, compat_uptr_t __user *head_ptr,
 136                            compat_size_t __user *len_ptr)
 137 {
 138         struct compat_robust_list_head __user *head;
 139         unsigned long ret;
 140         struct task_struct *p;
 141
 142         if (!futex_cmpxchg_enabled)
 143                 return -ENOSYS;
 144
 145         rcu_read_lock();
 146
 147         ret = -ESRCH;
 148         if (!pid)
 149                 p = current;
 150         else {
 151                 p = find_task_by_vpid(pid);
 152                 if (!p)
 153                         goto err_unlock;
 154         }
 155
 156         ret = -EPERM;
 157         if (!ptrace_may_access(p, PTRACE_MODE_READ))
 158                 goto err_unlock;
 159
 160         head = p->compat_robust_list;
 161         rcu_read_unlock();
 162
 163         if (put_user(sizeof(*head), len_ptr))
 164                 return -EFAULT;
 165         return put_user(ptr_to_compat(head), head_ptr);
 166
 167 err_unlock:
 168         rcu_read_unlock();
 169
 170         return ret;
 171 }
 172
 173 asmlinkage long compat_sys_futex(u32 __user *uaddr, int op, u32 val,
 174                 struct compat_timespec __user *utime, u32 __user *uaddr2,
 175                 u32 val3)
 176 {
 177         struct timespec ts;
 178         ktime_t t, *tp = NULL;
 179         int val2 = 0;
 180         int cmd = op & FUTEX_CMD_MASK;
 181
 182         if (utime && (cmd == FUTEX_WAIT || cmd == FUTEX_LOCK_PI ||
 183                       cmd == FUTEX_WAIT_BITSET ||
 184                       cmd == FUTEX_WAIT_REQUEUE_PI)) {
 185                 if (get_compat_timespec(&ts, utime))
 186                         return -EFAULT;
 187                 if (!timespec_valid(&ts))
 188                         return -EINVAL;
 189
 190                 t = timespec_to_ktime(ts);
 191                 if (cmd == FUTEX_WAIT)
 192                         t = ktime_add_safe(ktime_get(), t);
 193                 tp = &t;
 194         }
 195         if (cmd == FUTEX_REQUEUE || cmd == FUTEX_CMP_REQUEUE ||
 196             cmd == FUTEX_CMP_REQUEUE_PI || cmd == FUTEX_WAKE_OP)
 197                 val2 = (int) (unsigned long) utime;
 198
 199         return do_futex(uaddr, op, val, tp, uaddr2, val2, val3);
 200 }