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