aedrix-kernel/arch/arm/kernel/mmu.c

/*
    Copyright (C) 2012, Aaron Lindsay <aaron@aclindsay.com>

    This file is part of Aedrix.

    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License along
    with this program; if not, write to the Free Software Foundation, Inc.,
    51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 */

#include <print.h>
#include <types.h>

#include <arch/properties.h>

#define SCTLR 15,0,1,0,0
#define TTBR0 15,0,2,0,0
#define TTBR1 15,0,2,0,1
#define TTBCR 15,0,2,0,2

#define _cp_read(var, cp, opc1, CRn, CRm, opc2) asm("mrc p" #cp ", " #opc1 ", %0, c" #CRn ", c" #CRm ", " #opc2 ";" : "=r"(var) : )
#define _cp_write(var, cp, opc1, CRn, CRm, opc2) asm("mcr p" #cp ", " #opc1 ", %0, c" #CRn ", c" #CRm ", " #opc2 ";" : : "r"(var) )
#define cp_read(var, ...)  _cp_read(var, __VA_ARGS__)
#define cp_write(var, ...)  _cp_write(var, __VA_ARGS__)

void print_mapping(void *addr) {
	extern uint32 tt_base_virtual;
	print("%x: %x\n", addr, *(uint32 *)(tt_base_virtual + (((uint32)addr)>>18)));
}

static inline int page_intersects(uint32 *page_start, uint32 *lower, uint32 *upper) {
	return (lower >= page_start && lower < (page_start + (CONFIG_INIT_PAGE_SIZE>>2))) ||
		(upper >= page_start && upper < (page_start + (CONFIG_INIT_PAGE_SIZE>>2))) ||
		(lower < page_start && upper >= (page_start + (CONFIG_INIT_PAGE_SIZE>>2)));
}

void mmu_reinit() {
	extern uint32 tt_base_virtual;
	uint32 *curr_addr, *curr_tt_entry;
	uint32 virt_phys_offset = kernel_start_virtual() - kernel_start_physical(); /* CAUTION: 1 = 4 bytes */

	//get the current translation table base address
	curr_tt_entry = (uint32 *)tt_base_virtual;

	//do first loop iteration outside the loop, because we have to check against wrapping back around to know we're done
	*curr_tt_entry = 0xc02; /* 0xc02 means read/write at any priviledge level, and that it's a section w/o PXN bit set */
	curr_tt_entry++;

	//create identity mapping for entire address space using sections.
	//BUT, if we've relocated the kernel from where it is in physical
	//memory, make sure we keep those mappings correct, and we'll actually
	//swap the two mappings so all of memory is addressable.
	for (curr_addr = (uint32 *)CONFIG_INIT_PAGE_SIZE; curr_addr != 0; curr_addr += (CONFIG_INIT_PAGE_SIZE>>2)) {
		if (page_intersects(curr_addr, kernel_start_physical(), kernel_end_physical())) {
			*curr_tt_entry = (uint32)(curr_addr + virt_phys_offset) | 0xc02;
		} else if (page_intersects(curr_addr, kernel_start_virtual(), kernel_end_virtual())) {
			*curr_tt_entry = (uint32)(curr_addr - virt_phys_offset) | 0xc02;
		} else {
			*curr_tt_entry = (uint32)curr_addr | 0xc02;
		}
		curr_tt_entry++;
	}
}