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torvalds
GitHub Repository: torvalds/linux
 Path: blob/master/include/asm-generic/futex.h
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/* SPDX-License-Identifier: GPL-2.0 */

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#ifndef _ASM_GENERIC_FUTEX_H

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#define _ASM_GENERIC_FUTEX_H

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#include <linux/futex.h>

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#include <linux/uaccess.h>

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#include <asm/errno.h>

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#ifndef futex_atomic_cmpxchg_inatomic

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#ifndef CONFIG_SMP

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/*

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 * The following implementation only for uniprocessor machines.

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 * It relies on preempt_disable() ensuring mutual exclusion.

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 *

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 */

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#define futex_atomic_cmpxchg_inatomic(uval, uaddr, oldval, newval) \

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	futex_atomic_cmpxchg_inatomic_local(uval, uaddr, oldval, newval)

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#define arch_futex_atomic_op_inuser(op, oparg, oval, uaddr) \

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	futex_atomic_op_inuser_local(op, oparg, oval, uaddr)

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#endif /* CONFIG_SMP */

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#endif

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/**

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 * futex_atomic_op_inuser_local() - Atomic arithmetic operation with constant

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 *			  argument and comparison of the previous

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 *			  futex value with another constant.

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 *

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 * @encoded_op:	encoded operation to execute

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 * @uaddr:	pointer to user space address

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 *

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 * Return:

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 * 0 - On success

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 * -EFAULT - User access resulted in a page fault

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 * -EAGAIN - Atomic operation was unable to complete due to contention

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 * -ENOSYS - Operation not supported

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 */

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static inline int

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futex_atomic_op_inuser_local(int op, u32 oparg, int *oval, u32 __user *uaddr)

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{

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	int oldval, ret;

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	u32 tmp;

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	preempt_disable();

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	ret = -EFAULT;

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	if (unlikely(get_user(oldval, uaddr) != 0))

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		goto out_pagefault_enable;

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	ret = 0;

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	tmp = oldval;

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	switch (op) {

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	case FUTEX_OP_SET:

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		tmp = oparg;

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		break;

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	case FUTEX_OP_ADD:

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		tmp += oparg;

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		break;

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	case FUTEX_OP_OR:

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		tmp |= oparg;

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		break;

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	case FUTEX_OP_ANDN:

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		tmp &= ~oparg;

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		break;

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	case FUTEX_OP_XOR:

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		tmp ^= oparg;

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		break;

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	default:

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		ret = -ENOSYS;

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	}

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

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		ret = -EFAULT;

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out_pagefault_enable:

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	preempt_enable();

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	if (ret == 0)

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		*oval = oldval;

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	return ret;

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}

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/**

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 * futex_atomic_cmpxchg_inatomic_local() - Compare and exchange the content of the

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 *				uaddr with newval if the current value is

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 *				oldval.

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 * @uval:	pointer to store content of @uaddr

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 * @uaddr:	pointer to user space address

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 * @oldval:	old value

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 * @newval:	new value to store to @uaddr

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 *

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 * Return:

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 * 0 - On success

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 * -EFAULT - User access resulted in a page fault

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 * -EAGAIN - Atomic operation was unable to complete due to contention

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 */

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static inline int

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futex_atomic_cmpxchg_inatomic_local(u32 *uval, u32 __user *uaddr,

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			      u32 oldval, u32 newval)

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{

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	u32 val;

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	preempt_disable();

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	if (unlikely(get_user(val, uaddr) != 0)) {

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		preempt_enable();

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		return -EFAULT;

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	}

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	if (val == oldval && unlikely(put_user(newval, uaddr) != 0)) {

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		preempt_enable();

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		return -EFAULT;

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	}

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	*uval = val;

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	preempt_enable();

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	return 0;

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}

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#endif

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