u-boot/arch/x86/include/asm/control_regs.h

/*
 * Copyright (c) 2012 The Chromium OS Authors.
 *
 * (C) Copyright 2008-2011
 * Graeme Russ, <graeme.russ@gmail.com>
 *
 * (C) Copyright 2002
 * Daniel Engström, Omicron Ceti AB, <daniel@omicron.se>
 *
 * Portions of this file are derived from the Linux kernel source
 *  Copyright (C) 1991, 1992  Linus Torvalds
 *
 * SPDX-License-Identifier:	GPL-2.0+
 */

#ifndef __X86_CONTROL_REGS_H
#define __X86_CONTROL_REGS_H

/*
 * The memory clobber prevents the GCC from reordering the read/write order
 * of CR0
*/
static inline unsigned long read_cr0(void)
{
	unsigned long val;

	asm volatile ("movl %%cr0, %0" : "=r" (val) : : "memory");
	return val;
}

static inline void write_cr0(unsigned long val)
{
	asm volatile ("movl %0, %%cr0" : : "r" (val) : "memory");
}

static inline unsigned long read_cr2(void)
{
	unsigned long val;

	asm volatile("mov %%cr2,%0\n\t" : "=r" (val) : : "memory");
	return val;
}

static inline unsigned long read_cr3(void)
{
	unsigned long val;

	asm volatile("mov %%cr3,%0\n\t" : "=r" (val) : : "memory");
	return val;
}

static inline unsigned long read_cr4(void)
{
	unsigned long val;

	asm volatile("mov %%cr4,%0\n\t" : "=r" (val) : : "memory");
	return val;
}

static inline unsigned long get_debugreg(int regno)
{
	unsigned long val = 0;  /* Damn you, gcc! */

	switch (regno) {
	case 0:
		asm("mov %%db0, %0" : "=r" (val));
		break;
	case 1:
		asm("mov %%db1, %0" : "=r" (val));
		break;
	case 2:
		asm("mov %%db2, %0" : "=r" (val));
		break;
	case 3:
		asm("mov %%db3, %0" : "=r" (val));
		break;
	case 6:
		asm("mov %%db6, %0" : "=r" (val));
		break;
	case 7:
		asm("mov %%db7, %0" : "=r" (val));
		break;
	default:
		val = 0;
	}
	return val;
}

#endif