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, *next_entry, *pending;
  51         unsigned int limit = ROBUST_LIST_LIMIT, pi, next_pi, pip;
  52         compat_uptr_t uentry, next_uentry, upending;
  53         compat_long_t futex_offset;
  54         int rc;
  55
  56         /*
  57          * Fetch the list head (which was registered earlier, via
  58          * sys_set_robust_list()):
  59          */
  60         if (fetch_robust_entry(&uentry, &entry, &head->list.next, &pi))
  61                 return;
  62         /*
  63          * Fetch the relative futex offset:
  64          */
  65         if (get_user(futex_offset, &head->futex_offset))
  66                 return;
  67         /*
  68          * Fetch any possibly pending lock-add first, and handle it
  69          * if it exists:
  70          */
  71         if (fetch_robust_entry(&upending, &pending,
  72                                &head->list_op_pending, &pip))
  73                 return;
  74
  75         next_entry = NULL;      /* avoid warning with gcc */
  76         while (entry != (struct robust_list __user *) &head->list) {
  77                 /*
  78                  * Fetch the next entry in the list before calling
  79                  * handle_futex_death:
  80                  */
  81                 rc = fetch_robust_entry(&next_uentry, &next_entry,
  82                         (compat_uptr_t __user *)&entry->next, &next_pi);
  83                 /*
  84                  * A pending lock might already be on the list, so
  85                  * dont process it twice:
  86                  */
  87                 if (entry != pending) {
  88                         void __user *uaddr = futex_uaddr(entry,
  89                                                          futex_offset);
  90
  91                         if (handle_futex_death(uaddr, curr, pi))
  92                                 return;
  93                 }
  94                 if (rc)
  95                         return;
  96                 uentry = next_uentry;
  97                 entry = next_entry;
  98                 pi = next_pi;
  99                 /*
 100                  * Avoid excessively long or circular lists:
 101                  */
 102                 if (!--limit)
 103                         break;
 104
 105                 cond_resched();
 106         }
 107         if (pending) {
 108                 void __user *uaddr = futex_uaddr(pending, futex_offset);
 109
 110                 handle_futex_death(uaddr, curr, pip);
 111         }
 112 }
 113
 114 asmlinkage long
 115 compat_sys_set_robust_list(struct compat_robust_list_head __user *head,
 116                            compat_size_t len)
 117 {
 118         if (unlikely(len != sizeof(*head)))
 119                 return -EINVAL;
 120
 121         current->compat_robust_list = head;
 122
 123         return 0;
 124 }
 125
 126 asmlinkage long
 127 compat_sys_get_robust_list(int pid, compat_uptr_t __user *head_ptr,
 128                            compat_size_t __user *len_ptr)
 129 {
 130         struct compat_robust_list_head __user *head;
 131         unsigned long ret;
 132
 133         if (!pid)
 134                 head = current->compat_robust_list;
 135         else {
 136                 struct task_struct *p;
 137
 138                 ret = -ESRCH;
 139                 read_lock(&tasklist_lock);
 140                 p = find_task_by_pid(pid);
 141                 if (!p)
 142                         goto err_unlock;
 143                 ret = -EPERM;
 144                 if ((current->euid != p->euid) && (current->euid != p->uid) &&
 145                                 !capable(CAP_SYS_PTRACE))
 146                         goto err_unlock;
 147                 head = p->compat_robust_list;
 148                 read_unlock(&tasklist_lock);
 149         }
 150
 151         if (put_user(sizeof(*head), len_ptr))
 152                 return -EFAULT;
 153         return put_user(ptr_to_compat(head), head_ptr);
 154
 155 err_unlock:
 156         read_unlock(&tasklist_lock);
 157
 158         return ret;
 159 }
 160
 161 asmlinkage long compat_sys_futex(u32 __user *uaddr, int op, u32 val,
 162                 struct compat_timespec __user *utime, u32 __user *uaddr2,
 163                 u32 val3)
 164 {
 165         struct timespec ts;
 166         ktime_t t, *tp = NULL;
 167         int val2 = 0;
 168         int cmd = op & FUTEX_CMD_MASK;
 169
 170         if (utime && (cmd == FUTEX_WAIT || cmd == FUTEX_LOCK_PI)) {
 171                 if (get_compat_timespec(&ts, utime))
 172                         return -EFAULT;
 173                 if (!timespec_valid(&ts))
 174                         return -EINVAL;
 175
 176                 t = timespec_to_ktime(ts);
 177                 if (cmd == FUTEX_WAIT)
 178                         t = ktime_add_safe(ktime_get(), t);
 179                 tp = &t;
 180         }
 181         if (cmd == FUTEX_REQUEUE || cmd == FUTEX_CMP_REQUEUE)
 182                 val2 = (int) (unsigned long) utime;
 183
 184         return do_futex(uaddr, op, val, tp, uaddr2, val2, val3);
 185 }