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/*
* This file is part of the coreboot project.
*
* Copyright (C) 2016 Google Inc.
*
* 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; version 2 of the License.
*
* 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.
*/
#include <arch/early_variables.h>
#include <string.h>
#include <types.h>
#include <security/vboot/vbnv.h>
#include <security/vboot/vbnv_layout.h>
static int vbnv_initialized CAR_GLOBAL;
static uint8_t vbnv[VBOOT_VBNV_BLOCK_SIZE] CAR_GLOBAL;
/* Wrappers for accessing the variables marked as CAR_GLOBAL. */
static inline int is_vbnv_initialized(void)
{
return car_get_var(vbnv_initialized);
}
static inline uint8_t *vbnv_data_addr(int index)
{
uint8_t *vbnv_arr = car_get_var_ptr(vbnv);
return &vbnv_arr[index];
}
static inline uint8_t vbnv_data(int index)
{
return *vbnv_data_addr(index);
}
/* Return CRC-8 of the data, using x^8 + x^2 + x + 1 polynomial. */
static uint8_t crc8_vbnv(const uint8_t *data, int len)
{
unsigned int crc = 0;
int i, j;
for (j = len; j; j--, data++) {
crc ^= (*data << 8);
for (i = 8; i; i--) {
if (crc & 0x8000)
crc ^= (0x1070 << 3);
crc <<= 1;
}
}
return (uint8_t) (crc >> 8);
}
void vbnv_reset(uint8_t *vbnv_copy)
{
memset(vbnv_copy, 0, VBOOT_VBNV_BLOCK_SIZE);
}
/* Read VBNV data into cache. */
static void vbnv_setup(void)
{
if (!is_vbnv_initialized()) {
read_vbnv(vbnv_data_addr(0));
car_set_var(vbnv_initialized, 1);
}
}
/* Verify VBNV header and checksum. */
int verify_vbnv(uint8_t *vbnv_copy)
{
return (HEADER_SIGNATURE == (vbnv_copy[HEADER_OFFSET] & HEADER_MASK)) &&
(crc8_vbnv(vbnv_copy, CRC_OFFSET) == vbnv_copy[CRC_OFFSET]);
}
/* Re-generate VBNV checksum. */
void regen_vbnv_crc(uint8_t *vbnv_copy)
{
vbnv_copy[CRC_OFFSET] = crc8_vbnv(vbnv_copy, CRC_OFFSET);
}
/*
* Read VBNV data from configured storage backend.
* If VBNV verification fails, reset the vbnv copy.
*/
void read_vbnv(uint8_t *vbnv_copy)
{
if (CONFIG(VBOOT_VBNV_CMOS))
read_vbnv_cmos(vbnv_copy);
else if (CONFIG(VBOOT_VBNV_EC))
read_vbnv_ec(vbnv_copy);
else if (CONFIG(VBOOT_VBNV_FLASH))
read_vbnv_flash(vbnv_copy);
/* Check data for consistency */
if (!verify_vbnv(vbnv_copy))
vbnv_reset(vbnv_copy);
}
/*
* Write VBNV data to configured storage backend.
* This assumes that the caller has updated the CRC already.
*/
void save_vbnv(const uint8_t *vbnv_copy)
{
if (CONFIG(VBOOT_VBNV_CMOS))
save_vbnv_cmos(vbnv_copy);
else if (CONFIG(VBOOT_VBNV_EC))
save_vbnv_ec(vbnv_copy);
else if (CONFIG(VBOOT_VBNV_FLASH))
save_vbnv_flash(vbnv_copy);
/* Clear initialized flag to force cached data to be updated */
car_set_var(vbnv_initialized, 0);
}
/* Save a recovery reason into VBNV. */
void set_recovery_mode_into_vbnv(int recovery_reason)
{
uint8_t vbnv_copy[VBOOT_VBNV_BLOCK_SIZE];
read_vbnv(vbnv_copy);
vbnv_copy[RECOVERY_OFFSET] = recovery_reason;
vbnv_copy[CRC_OFFSET] = crc8_vbnv(vbnv_copy, CRC_OFFSET);
save_vbnv(vbnv_copy);
}
/* Read the recovery reason from VBNV. */
int get_recovery_mode_from_vbnv(void)
{
vbnv_setup();
return vbnv_data(RECOVERY_OFFSET);
}
/* Read the USB Device Controller(UDC) enable flag from VBNV. */
int vbnv_udc_enable_flag(void)
{
vbnv_setup();
return (vbnv_data(DEV_FLAGS_OFFSET) & DEV_ENABLE_UDC) ? 1 : 0;
}
void vbnv_init(uint8_t *vbnv_copy)
{
if (CONFIG(VBOOT_VBNV_CMOS))
vbnv_init_cmos(vbnv_copy);
read_vbnv(vbnv_copy);
}
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