/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _ASM_GENERIC_FUTEX_H
#define _ASM_GENERIC_FUTEX_H

#include <linux/futex.h>
#include <linux/uaccess.h>
#include <asm/errno.h>

#ifndef futex_atomic_cmpxchg_inatomic
#ifndef CONFIG_SMP
/*
 * The following implementation only for uniprocessor machines.
 * It relies on preempt_disable() ensuring mutual exclusion.
 *
 */
#define futex_atomic_cmpxchg_inatomic(uval, uaddr, oldval, newval) \
        futex_atomic_cmpxchg_inatomic_local(uval, uaddr, oldval, newval)
#define arch_futex_atomic_op_inuser(op, oparg, oval, uaddr) \
        futex_atomic_op_inuser_local(op, oparg, oval, uaddr)
#endif /* CONFIG_SMP */
#endif

/**
 * futex_atomic_op_inuser_local() - Atomic arithmetic operation with constant
 *                        argument and comparison of the previous
 *                        futex value with another constant.
 *
 * @encoded_op: encoded operation to execute
 * @uaddr:      pointer to user space address
 *
 * Return:
 * 0 - On success
 * -EFAULT - User access resulted in a page fault
 * -EAGAIN - Atomic operation was unable to complete due to contention
 * -ENOSYS - Operation not supported
 */
static inline int
futex_atomic_op_inuser_local(int op, u32 oparg, int *oval, u32 __user *uaddr)
{
        int oldval, ret;
        u32 tmp;

        preempt_disable();

        ret = -EFAULT;
        if (unlikely(get_user(oldval, uaddr) != 0))
                goto out_pagefault_enable;

        ret = 0;
        tmp = oldval;

        switch (op) {
        case FUTEX_OP_SET:
                tmp = oparg;
                break;
        case FUTEX_OP_ADD:
                tmp += oparg;
                break;
        case FUTEX_OP_OR:
                tmp |= oparg;
                break;
        case FUTEX_OP_ANDN:
                tmp &= ~oparg;
                break;
        case FUTEX_OP_XOR:
                tmp ^= oparg;
                break;
        default:
                ret = -ENOSYS;
        }

        if (ret == 0 && unlikely(put_user(tmp, uaddr) != 0))
                ret = -EFAULT;

out_pagefault_enable:
        preempt_enable();

        if (ret == 0)
                *oval = oldval;

        return ret;
}

/**
 * futex_atomic_cmpxchg_inatomic_local() - Compare and exchange the content of the
 *                              uaddr with newval if the current value is
 *                              oldval.
 * @uval:       pointer to store content of @uaddr
 * @uaddr:      pointer to user space address
 * @oldval:     old value
 * @newval:     new value to store to @uaddr
 *
 * Return:
 * 0 - On success
 * -EFAULT - User access resulted in a page fault
 * -EAGAIN - Atomic operation was unable to complete due to contention
 */
static inline int
futex_atomic_cmpxchg_inatomic_local(u32 *uval, u32 __user *uaddr,
                              u32 oldval, u32 newval)
{
        u32 val;

        preempt_disable();
        if (unlikely(get_user(val, uaddr) != 0)) {
                preempt_enable();
                return -EFAULT;
        }

        if (val == oldval && unlikely(put_user(newval, uaddr) != 0)) {
                preempt_enable();
                return -EFAULT;
        }

        *uval = val;
        preempt_enable();

        return 0;
}

#endif