init_mmu.c

来自「QNX ADS BSP code for i.MX27 chips」· C语言 代码 · 共 82 行

/*
 * $QNXLicenseC: 
 * Copyright 2007, QNX Software Systems.  
 *  
 * Licensed under the Apache License, Version 2.0 (the "License"). You  
 * may not reproduce, modify or distribute this software except in  
 * compliance with the License. You may obtain a copy of the License  
 * at: http://www.apache.org/licenses/LICENSE-2.0  
 *  
 * Unless required by applicable law or agreed to in writing, software  
 * distributed under the License is distributed on an "AS IS" basis,  
 * WITHOUT WARRANTIES OF ANY KIND, either express or implied. 
 * 
 * This file may contain contributions from others, either as  
 * contributors under the License or as licensors under other terms.   
 * Please review this entire file for other proprietary rights or license  
 * notices, as well as the QNX Development Suite License Guide at  
 * http://licensing.qnx.com/license-guide/ for other information. 
 * $
 */

#include "startup.h"

extern void	vstart();
extern void	arm_get_pte_info();

paddr_t		L1_paddr;
paddr_t		L1_vaddr;
paddr_t		L2_paddr;
paddr_t		startup_base;
unsigned	startup_size;

/*
 * Section mappings
 */
#define	SCSIZE	0x100000
#define SCMASK	(SCSIZE-1)

/*
 * Initialize page tables. This prepares the system to leap into virtual mode.
 * This code is hardware independant and should not have to be
 * changed by end users.
 */
void
init_mmu(void)
{
	unsigned	base;

	/*
	 * Get the CPU-specific PTE descriptors
	 */
	arm_get_pte_info();

	/*
	 * Allocate the L1 table and the "page directory" used to map L2 tables
	 */
	L1_paddr = calloc_ram(ARM_L1_SIZE, ARM_L1_SIZE);
	L2_paddr = calloc_ram(__PAGESIZE, __PAGESIZE);

	/*
	 * Map the "page directory" within itself
	 */
	arm_ptmap(L2_paddr, ARM_PTP_BASE);

	/*
	 * Map the real L1 table
	 */
	L1_vaddr = arm_map(~0L, L1_paddr, ARM_L1_SIZE, ARM_PTE_RW);

	/*
	 * Section map startup code to allow transition to virtual addresses.
	 * This 1-1 mapping is also used by kdebug to access the imagefs.
	 * procnto uses syspage->un.arm.startup_base/startup_size to unmap it.
	 */
	startup_base = shdr->ram_paddr & ~SCMASK;
	startup_size = shdr->ram_size;
	for (base = startup_base; base < startup_base + startup_size; base += SCSIZE) {
		arm_scmap(base, base, ARM_PTE_RO);
	}
}