include/asm-generic/futex.h

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 #ifndef _ASM_GENERIC_FUTEX_H
   3 #define _ASM_GENERIC_FUTEX_H
   4
   5 #include <linux/futex.h>
   6 #include <linux/uaccess.h>
   7 #include <asm/errno.h>
   8
   9 #ifndef CONFIG_SMP
  10 /*
  11  * The following implementation only for uniprocessor machines.
  12  * It relies on preempt_disable() ensuring mutual exclusion.
  13  *
  14  */
  15
  16 /**
  17  * arch_futex_atomic_op_inuser() - Atomic arithmetic operation with constant
  18  *                        argument and comparison of the previous
  19  *                        futex value with another constant.
  20  *
  21  * @encoded_op: encoded operation to execute
  22  * @uaddr:      pointer to user space address
  23  *
  24  * Return:
  25  * 0 - On success
  26  * -EFAULT - User access resulted in a page fault
  27  * -EAGAIN - Atomic operation was unable to complete due to contention
  28  * -ENOSYS - Operation not supported
  29  */
  30 static inline int
  31 arch_futex_atomic_op_inuser(int op, u32 oparg, int *oval, u32 __user *uaddr)
  32 {
  33         int oldval, ret;
  34         u32 tmp;
  35
  36         preempt_disable();
  37
  38         ret = -EFAULT;
  39         if (unlikely(get_user(oldval, uaddr) != 0))
  40                 goto out_pagefault_enable;
  41
  42         ret = 0;
  43         tmp = oldval;
  44
  45         switch (op) {
  46         case FUTEX_OP_SET:
  47                 tmp = oparg;
  48                 break;
  49         case FUTEX_OP_ADD:
  50                 tmp += oparg;
  51                 break;
  52         case FUTEX_OP_OR:
  53                 tmp |= oparg;
  54                 break;
  55         case FUTEX_OP_ANDN:
  56                 tmp &= ~oparg;
  57                 break;
  58         case FUTEX_OP_XOR:
  59                 tmp ^= oparg;
  60                 break;
  61         default:
  62                 ret = -ENOSYS;
  63         }
  64
  65         if (ret == 0 && unlikely(put_user(tmp, uaddr) != 0))
  66                 ret = -EFAULT;
  67
  68 out_pagefault_enable:
  69         preempt_enable();
  70
  71         if (ret == 0)
  72                 *oval = oldval;
  73
  74         return ret;
  75 }
  76
  77 /**
  78  * futex_atomic_cmpxchg_inatomic() - Compare and exchange the content of the
  79  *                              uaddr with newval if the current value is
  80  *                              oldval.
  81  * @uval:       pointer to store content of @uaddr
  82  * @uaddr:      pointer to user space address
  83  * @oldval:     old value
  84  * @newval:     new value to store to @uaddr
  85  *
  86  * Return:
  87  * 0 - On success
  88  * -EFAULT - User access resulted in a page fault
  89  * -EAGAIN - Atomic operation was unable to complete due to contention
  90  * -ENOSYS - Function not implemented (only if !HAVE_FUTEX_CMPXCHG)
  91  */
  92 static inline int
  93 futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr,
  94                               u32 oldval, u32 newval)
  95 {
  96         u32 val;
  97
  98         preempt_disable();
  99         if (unlikely(get_user(val, uaddr) != 0)) {
 100                 preempt_enable();
 101                 return -EFAULT;
 102         }
 103
 104         if (val == oldval && unlikely(put_user(newval, uaddr) != 0)) {
 105                 preempt_enable();
 106                 return -EFAULT;
 107         }
 108
 109         *uval = val;
 110         preempt_enable();
 111
 112         return 0;
 113 }
 114
 115 #else
 116 static inline int
 117 arch_futex_atomic_op_inuser(int op, u32 oparg, int *oval, u32 __user *uaddr)
 118 {
 119         return -ENOSYS;
 120 }
 121
 122 static inline int
 123 futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr,
 124                               u32 oldval, u32 newval)
 125 {
 126         return -ENOSYS;
 127 }
 128
 129 #endif /* CONFIG_SMP */
 130 #endif