LXR linux/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 */
  30static inline int
  31arch_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
  68out_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 */
  92static inline int
  93futex_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
 116static inline int
 117arch_futex_atomic_op_inuser(int op, u32 oparg, int *oval, u32 __user *uaddr)
 118{
 119        return -ENOSYS;
 120}
 121
 122static inline int
 123futex_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
 131