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/* Copyright (c) 2013 The Chromium OS Authors. All rights reserved.
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*/
/* MPU module for Chrome EC */
#include "mpu.h"
#include "console.h"
#include "registers.h"
#include "task.h"
#include "util.h"
/**
* Update a memory region.
*
* region: number of the region to update
* addr: base address of the region
* size_bit: size of the region in power of two.
* attr: attribute of the region. Current value will be overwritten if enable
* is set.
* enable: enables the region if non zero. Otherwise, disables the region.
*
* Based on 3.1.4.1 'Updating an MPU Region' of Stellaris LM4F232H5QC Datasheet
*/
static void mpu_update_region(uint8_t region, uint32_t addr, uint8_t size_bit,
uint16_t attr, uint8_t enable)
{
asm volatile("isb; dsb;");
MPU_NUMBER = region;
MPU_SIZE &= ~1; /* Disable */
if (enable) {
MPU_BASE = addr;
MPU_ATTR = attr;
MPU_SIZE = (size_bit - 1) << 1 | 1; /* Enable */
}
asm volatile("isb; dsb;");
}
int mpu_config_region(uint8_t region, uint32_t addr, uint32_t size,
uint16_t attr, uint8_t enable)
{
int size_bit = 0;
if (!size)
return -EC_ERROR_INVAL;
while (!(size & 1)) {
size_bit++;
size >>= 1;
}
/* Region size must be a power of 2 (size == 0) and equal or larger than
* 32 (size_bit >= 5) */
if (size > 1 || size_bit < 5)
return -EC_ERROR_INVAL;
mpu_update_region(region, addr, size_bit, attr, enable);
return EC_SUCCESS;
}
int mpu_nx_region(uint8_t region, uint32_t addr, uint32_t size)
{
return mpu_config_region(
region, addr, size,
MPU_ATTR_NX | MPU_ATTR_FULLACCESS | MPU_ATTR_INTERNALSRAM, 1);
}
void mpu_enable(void)
{
MPU_CTRL |= MPU_CTRL_PRIVDEFEN | MPU_CTRL_HFNMIENA | MPU_CTRL_ENABLE;
}
void mpu_disable(void)
{
MPU_CTRL &= ~(MPU_CTRL_PRIVDEFEN | MPU_CTRL_HFNMIENA | MPU_CTRL_ENABLE);
}
uint32_t mpu_get_type(void)
{
return MPU_TYPE;
}
/**
* Prevent code from running on RAM.
* We need to allow execution from iram.text. Using higher region# allows us to
* do 'whitelisting' (lock down all then create exceptions).
*/
int mpu_protect_ram(void)
{
int ret;
ret = mpu_nx_region(0, CONFIG_RAM_BASE, CONFIG_RAM_SIZE);
if (ret != EC_SUCCESS)
return ret;
ret = mpu_config_region(
7, (uint32_t)&__iram_text_start,
(uint32_t)(&__iram_text_end - &__iram_text_start),
MPU_ATTR_FULLACCESS | MPU_ATTR_INTERNALSRAM, 1);
return ret;
}
int mpu_pre_init(void)
{
int i;
if (mpu_get_type() != 0x00000800)
return EC_ERROR_UNIMPLEMENTED;
mpu_disable();
for (i = 0; i < 8; ++i) {
mpu_config_region(
i, CONFIG_RAM_BASE, CONFIG_RAM_SIZE,
MPU_ATTR_FULLACCESS | MPU_ATTR_INTERNALSRAM, 0);
}
return EC_SUCCESS;
}
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