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  * <0 - On error
  27  */
  28 static inline int
  29 arch_futex_atomic_op_inuser(int op, u32 oparg, int *oval, u32 __user *uaddr)
  30 {
  31         int oldval, ret;
  32         u32 tmp;
  33
  34         preempt_disable();
  35         pagefault_disable();
  36
  37         ret = -EFAULT;
  38         if (unlikely(get_user(oldval, uaddr) != 0))
  39                 goto out_pagefault_enable;
  40
  41         ret = 0;
  42         tmp = oldval;
  43
  44         switch (op) {
  45         case FUTEX_OP_SET:
  46                 tmp = oparg;
  47                 break;
  48         case FUTEX_OP_ADD:
  49                 tmp += oparg;
  50                 break;
  51         case FUTEX_OP_OR:
  52                 tmp |= oparg;
  53                 break;
  54         case FUTEX_OP_ANDN:
  55                 tmp &= ~oparg;
  56                 break;
  57         case FUTEX_OP_XOR:
  58                 tmp ^= oparg;
  59                 break;
  60         default:
  61                 ret = -ENOSYS;
  62         }
  63
  64         if (ret == 0 && unlikely(put_user(tmp, uaddr) != 0))
  65                 ret = -EFAULT;
  66
  67 out_pagefault_enable:
  68         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  * <0 - On error
  89  */
  90 static inline int
  91 futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr,
  92                               u32 oldval, u32 newval)
  93 {
  94         u32 val;
  95
  96         preempt_disable();
  97         if (unlikely(get_user(val, uaddr) != 0)) {
  98                 preempt_enable();
  99                 return -EFAULT;
 100         }
 101
 102         if (val == oldval && unlikely(put_user(newval, uaddr) != 0)) {
 103                 preempt_enable();
 104                 return -EFAULT;
 105         }
 106
 107         *uval = val;
 108         preempt_enable();
 109
 110         return 0;
 111 }
 112
 113 #else
 114 static inline int
 115 arch_futex_atomic_op_inuser(int op, u32 oparg, int *oval, u32 __user *uaddr)
 116 {
 117         int oldval = 0, ret;
 118
 119         pagefault_disable();
 120
 121         switch (op) {
 122         case FUTEX_OP_SET:
 123         case FUTEX_OP_ADD:
 124         case FUTEX_OP_OR:
 125         case FUTEX_OP_ANDN:
 126         case FUTEX_OP_XOR:
 127         default:
 128                 ret = -ENOSYS;
 129         }
 130
 131         pagefault_enable();
 132
 133         if (!ret)
 134                 *oval = oldval;
 135
 136         return ret;
 137 }
 138
 139 static inline int
 140 futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr,
 141                               u32 oldval, u32 newval)
 142 {
 143         return -ENOSYS;
 144 }
 145
 146 #endif /* CONFIG_SMP */
 147 #endif