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         pagefault_disable();
  38
  39         ret = -EFAULT;
  40         if (unlikely(get_user(oldval, uaddr) != 0))
  41                 goto out_pagefault_enable;
  42
  43         ret = 0;
  44         tmp = oldval;
  45
  46         switch (op) {
  47         case FUTEX_OP_SET:
  48                 tmp = oparg;
  49                 break;
  50         case FUTEX_OP_ADD:
  51                 tmp += oparg;
  52                 break;
  53         case FUTEX_OP_OR:
  54                 tmp |= oparg;
  55                 break;
  56         case FUTEX_OP_ANDN:
  57                 tmp &= ~oparg;
  58                 break;
  59         case FUTEX_OP_XOR:
  60                 tmp ^= oparg;
  61                 break;
  62         default:
  63                 ret = -ENOSYS;
  64         }
  65
  66         if (ret == 0 && unlikely(put_user(tmp, uaddr) != 0))
  67                 ret = -EFAULT;
  68
  69 out_pagefault_enable:
  70         pagefault_enable();
  71         preempt_enable();
  72
  73         if (ret == 0)
  74                 *oval = oldval;
  75
  76         return ret;
  77 }
  78
  79 /**
  80  * futex_atomic_cmpxchg_inatomic() - Compare and exchange the content of the
  81  *                              uaddr with newval if the current value is
  82  *                              oldval.
  83  * @uval:       pointer to store content of @uaddr
  84  * @uaddr:      pointer to user space address
  85  * @oldval:     old value
  86  * @newval:     new value to store to @uaddr
  87  *
  88  * Return:
  89  * 0 - On success
  90  * -EFAULT - User access resulted in a page fault
  91  * -EAGAIN - Atomic operation was unable to complete due to contention
  92  * -ENOSYS - Function not implemented (only if !HAVE_FUTEX_CMPXCHG)
  93  */
  94 static inline int
  95 futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr,
  96                               u32 oldval, u32 newval)
  97 {
  98         u32 val;
  99
 100         preempt_disable();
 101         if (unlikely(get_user(val, uaddr) != 0)) {
 102                 preempt_enable();
 103                 return -EFAULT;
 104         }
 105
 106         if (val == oldval && unlikely(put_user(newval, uaddr) != 0)) {
 107                 preempt_enable();
 108                 return -EFAULT;
 109         }
 110
 111         *uval = val;
 112         preempt_enable();
 113
 114         return 0;
 115 }
 116
 117 #else
 118 static inline int
 119 arch_futex_atomic_op_inuser(int op, u32 oparg, int *oval, u32 __user *uaddr)
 120 {
 121         return -ENOSYS;
 122 }
 123
 124 static inline int
 125 futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr,
 126                               u32 oldval, u32 newval)
 127 {
 128         return -ENOSYS;
 129 }
 130
 131 #endif /* CONFIG_SMP */
 132 #endif