include/asm-generic/futex.h

   1 #ifndef _ASM_GENERIC_FUTEX_H
   2 #define _ASM_GENERIC_FUTEX_H
   3
   4 #include <linux/futex.h>
   5 #include <linux/uaccess.h>
   6 #include <asm/errno.h>
   7
   8 #ifndef CONFIG_SMP
   9 /*
  10  * The following implementation only for uniprocessor machines.
  11  * It relies on preempt_disable() ensuring mutual exclusion.
  12  *
  13  */
  14
  15 /**
  16  * arch_futex_atomic_op_inuser() - Atomic arithmetic operation with constant
  17  *                        argument and comparison of the previous
  18  *                        futex value with another constant.
  19  *
  20  * @encoded_op: encoded operation to execute
  21  * @uaddr:      pointer to user space address
  22  *
  23  * Return:
  24  * 0 - On success
  25  * <0 - On error
  26  */
  27 static inline int
  28 arch_futex_atomic_op_inuser(int op, u32 oparg, int *oval, u32 __user *uaddr)
  29 {
  30         int oldval, ret;
  31         u32 tmp;
  32
  33         preempt_disable();
  34         pagefault_disable();
  35
  36         ret = -EFAULT;
  37         if (unlikely(get_user(oldval, uaddr) != 0))
  38                 goto out_pagefault_enable;
  39
  40         ret = 0;
  41         tmp = oldval;
  42
  43         switch (op) {
  44         case FUTEX_OP_SET:
  45                 tmp = oparg;
  46                 break;
  47         case FUTEX_OP_ADD:
  48                 tmp += oparg;
  49                 break;
  50         case FUTEX_OP_OR:
  51                 tmp |= oparg;
  52                 break;
  53         case FUTEX_OP_ANDN:
  54                 tmp &= ~oparg;
  55                 break;
  56         case FUTEX_OP_XOR:
  57                 tmp ^= oparg;
  58                 break;
  59         default:
  60                 ret = -ENOSYS;
  61         }
  62
  63         if (ret == 0 && unlikely(put_user(tmp, uaddr) != 0))
  64                 ret = -EFAULT;
  65
  66 out_pagefault_enable:
  67         pagefault_enable();
  68         preempt_enable();
  69
  70         if (ret == 0)
  71                 *oval = oldval;
  72
  73         return ret;
  74 }
  75
  76 /**
  77  * futex_atomic_cmpxchg_inatomic() - Compare and exchange the content of the
  78  *                              uaddr with newval if the current value is
  79  *                              oldval.
  80  * @uval:       pointer to store content of @uaddr
  81  * @uaddr:      pointer to user space address
  82  * @oldval:     old value
  83  * @newval:     new value to store to @uaddr
  84  *
  85  * Return:
  86  * 0 - On success
  87  * <0 - On error
  88  */
  89 static inline int
  90 futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr,
  91                               u32 oldval, u32 newval)
  92 {
  93         u32 val;
  94
  95         preempt_disable();
  96         if (unlikely(get_user(val, uaddr) != 0)) {
  97                 preempt_enable();
  98                 return -EFAULT;
  99         }
 100
 101         if (val == oldval && unlikely(put_user(newval, uaddr) != 0)) {
 102                 preempt_enable();
 103                 return -EFAULT;
 104         }
 105
 106         *uval = val;
 107         preempt_enable();
 108
 109         return 0;
 110 }
 111
 112 #else
 113 static inline int
 114 arch_futex_atomic_op_inuser(int op, u32 oparg, int *oval, u32 __user *uaddr)
 115 {
 116         int oldval = 0, ret;
 117
 118         pagefault_disable();
 119
 120         switch (op) {
 121         case FUTEX_OP_SET:
 122         case FUTEX_OP_ADD:
 123         case FUTEX_OP_OR:
 124         case FUTEX_OP_ANDN:
 125         case FUTEX_OP_XOR:
 126         default:
 127                 ret = -ENOSYS;
 128         }
 129
 130         pagefault_enable();
 131
 132         if (!ret)
 133                 *oval = oldval;
 134
 135         return ret;
 136 }
 137
 138 static inline int
 139 futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr,
 140                               u32 oldval, u32 newval)
 141 {
 142         return -ENOSYS;
 143 }
 144
 145 #endif /* CONFIG_SMP */
 146 #endif