Atmosphere/stratosphere/boot/source/boot_calibration.cpp

/*
 * Copyright (c) 2018-2019 Atmosphère-NX
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms and conditions of the GNU General Public License,
 * version 2, as published by the Free Software Foundation.
 *
 * This program is distributed in the hope 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, see <http://www.gnu.org/licenses/>.
 */

#include "boot_functions.hpp"

static constexpr size_t BatteryLotOffset = 0x2CE0;
static constexpr size_t BatteryLotSize = 0x20;
static constexpr size_t BatteryVersionOffset = 0x4310;
static constexpr size_t BatteryVersionSize = 0x10;

static constexpr u32 DefaultBatteryVendor = static_cast<u32>('A');
static constexpr u32 DefaultBatteryVersion = 0;

static constexpr Result ResultCalInvalidCrc = 0xCAC6; /* TODO: Verify this really is cal, move to libstrat results. */

u16 Boot::GetCrc16(const void *data, size_t size) {
    static constexpr u16 s_crc_table[0x10] = {
        0x0000, 0xCC01, 0xD801, 0x1400, 0xF001, 0x3C00, 0x2800, 0xE401,
        0xA001, 0x6C00, 0x7800, 0xB401, 0x5000, 0x9C01, 0x8801, 0x4400
    };

    if (data == nullptr) {
        std::abort();
    }

    u16 crc16 = 0x55AA;
    const u8 *data_u8 = reinterpret_cast<const u8 *>(data);
    for (size_t i = 0; i < size; i++) {
        crc16 = (crc16 >> 4) ^ (s_crc_table[crc16 & 0xF]) ^ (s_crc_table[data_u8[i] & 0xF]);
        crc16 = (crc16 >> 4) ^ (s_crc_table[crc16 & 0xF]) ^ (s_crc_table[(data_u8[i] >> 4) & 0xF]);
    }
    return crc16;
}

static Result ValidateCalibrationCrc16(const void *data, size_t size) {
    const u8 *data_u8 = reinterpret_cast<const u8 *>(data);
    if (Boot::GetCrc16(data, size - sizeof(u16)) != *(reinterpret_cast<const u16 *>(&data_u8[size - sizeof(u16)]))) {
        return ResultCalInvalidCrc;
    }
    return ResultSuccess;
}

static Result GetBatteryVendorImpl(u32 *vendor) {
    FsStorage s;
    R_TRY(fsOpenBisStorage(&s, FsBisStorageId_CalibrationBinary));
    ON_SCOPE_EXIT { fsStorageClose(&s); };

    u8 battery_lot[BatteryLotSize];
    R_TRY(fsStorageRead(&s, BatteryLotOffset, battery_lot, sizeof(battery_lot)));

    R_TRY(ValidateCalibrationCrc16(battery_lot, sizeof(battery_lot)));

    *vendor = battery_lot[7];
    return ResultSuccess;
}

static Result GetBatteryVersionImpl(u32 *version) {
    FsStorage s;
    R_TRY(fsOpenBisStorage(&s, FsBisStorageId_CalibrationBinary));
    ON_SCOPE_EXIT { fsStorageClose(&s); };

    u8 battery_version[BatteryVersionSize];
    R_TRY(fsStorageRead(&s, BatteryVersionOffset, battery_version, sizeof(battery_version)));

    R_TRY(ValidateCalibrationCrc16(battery_version, sizeof(battery_version)));

    *version = battery_version[0];
    return ResultSuccess;
}

u32 Boot::GetBatteryVendor() {
    u32 vendor;
    if (R_FAILED(GetBatteryVendorImpl(&vendor))) {
        return DefaultBatteryVendor;
    }
    return vendor;
}

u32 Boot::GetBatteryVersion() {
    u32 version;
    if (R_FAILED(GetBatteryVersionImpl(&version))) {
        return DefaultBatteryVersion;
    }
    return version;
}