Android系统开发 android8之后版本读写Nvram

秦嘉宏 發表於 2022-11-8 14:20:00

Android系统开发 android8之后版本读写Nvram

<h1>前言</h1>
　　此博客讲解Android8之后的版本为准，Android8.0以前，是通过AIDL的方式去获取一个名为【NvRAMAgent】的服务。 到了Android8.0之后，NVRAM的读写方式已经变更，不再通过AIDL去获取NVRAM服务，然后进行读写。而是通过HIDL的方式去获取服务来进行读写。
　　另外请注意，此博客讲解的是如何使用Android studio上编译的apk工程读写Nvram中的SN与WiFi的Mac地址。如果是系统工程apk请拉到博客最下面。
<h1>了解文件位置</h1>
在开始实现具体操作流程之前先了解下在系统工程目录里新的NVRAM是怎么生成的。HIDL的是需要依靠系统编译成so与jar形成接口来调用的，类似于AIDL与JNI的组合使用。另外这里只需要了解，并不需要修改这些文件与代码。因为我们需要得到经过系统编译后的so与jar文件，将其导入到后续我们的apk项目里。
<h2>hal文件</h2>
路径：
<div class="cnblogs_code">
<pre>vendor/mediatek/proprietary/hardware/interfaces/nvram/1.0/INvram.hal</pre>
</div>
 代码：
<div class="cnblogs_code">
<pre>/*
* Copyright (C) 2016 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file 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 OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/

package vendor.mediatek.hardware.nvram@1.0;

/*
* Purpose:
* Nvram hidl interface is used by java layer to access nvram file
* Note:
* Support nvram file list in nvram@1.0 was listed as below
* Please update nvram interface and versoin if new nvram file need to be supported
*
/vendor/nvdata/APCFG/APRDEB/BT_Addr
/vendor/nvdata/APCFG/APRDCL/AUXADC
/vendor/nvdata/media/CAMERA_Para
/vendor/nvdata/media/CAMERA_3A
/vendor/nvdata/media/CAMERA_SHADING
/vendor/nvdata/media/CAMERA_DEFECT
/vendor/nvdata/media/CAMERA_SENSOR
/vendor/nvdata/media/CAMERA_LENS
/vendor/nvdata/APCFG/APRDCL/UART
/vendor/nvdata/APCFG/APRDCL/FACTORY
/vendor/nvdata/APCFG/APRDCL/BWCS
/vendor/nvdata/APCFG/APRDCL/HWMON_ACC
/vendor/nvdata/APCFG/APRDCL/HWMON_GYRO
/vendor/nvdata/media/Voice_Recognize_Param
/vendor/nvdata/media/Audio_AudEnh_Control_Opt
/vendor/nvdata/media/Audio_VOIP_Param
/vendor/nvdata/APCFG/APRDCL/HWMON_PS
/vendor/nvdata/APCFG/APRDCL/MD_Type
/vendor/nvdata/APCFG/APRDCL/EXT_MD_Type
/vendor/nvdata/APCFG/APRDCL/SDIO
/vendor/nvdata/media/CAMERA_VERSION
/vendor/nvdata/media/CAMERA_FEATURE
/vendor/nvdata/media/CAMERA_GEOMETRY
/vendor/nvdata/APCFG/APRDCL/MD_SBP
/vendor/nvdata/media/CAMERA_SHADING2
/vendor/nvdata/media/CAMERA_PLINE
/vendor/nvdata/media/CAMERA_AF
/vendor/nvdata/media/CAMERA_FLASH_CALIBRATION
/vendor/nvdata/media/Audio_Sph
/vendor/nvdata/APCFG/APRDEB/GPS
/vendor/nvdata/media/Audio_CompFlt
/vendor/nvdata/media/Audio_Effect
/vendor/nvdata/APCFG/APRDEB/WIFI
/vendor/nvdata/APCFG/APRDEB/WIFI_CUSTOM
/vendor/nvdata/media/Audio_Sph_Med
/vendor/nvdata/media/Audio_Vol_custom
/vendor/nvdata/media/Sph_Dual_Mic
/vendor/nvdata/media/Audio_Wb_Sph
/vendor/nvdata/APCFG/APRDEB/PRODUCT_INFO
/vendor/nvdata/media/Headphone_CompFlt
/vendor/nvdata/media/Audio_gain_table
/vendor/nvdata/media/Audio_ver1_Vol_custom
/vendor/nvdata/media/Audio_Hd_Record_Param
/vendor/nvdata/media/Audio_Hd_Record_Scene_Table
/vendor/nvdata/media/Audio_Buffer_DC_Calibration_Param
/vendor/nvdata/media/VibSpk_CompFlt
/vendor/nvdata/media/MusicDRC_CompFlt
/vendor/nvdata/media/RingToneDRC_CompFlt
/vendor/nvdata/media/Audio_MAGI_CONFERENCE
/vendor/nvdata/media/Audio_HAC_Param
*/

interface INvram {
readFileByName(string filename, uint32_t size)
 generates (string data);
writeFileByNamevec(string filename, uint32_t size, vec<uint8_t> data)
 generates (int8_t retval);
};</pre>
</div>
<h2>.h文件</h2>
路径
<div class="cnblogs_code">
<pre>vendor/mediatek/proprietary/external/libnvram/nvram_hidl/1.0/NvRam.h</pre>
</div>
代码：
<div class="cnblogs_code">
<pre>#ifndef VENDOR_MEDIATEK_HARDWARE_NVRAM_V1_0_NVRAM_H
#define VENDOR_MEDIATEK_HARDWARE_NVRAM_V1_0_NVRAM_H

#include <vendor/mediatek/hardware/nvram/1.0/INvram.h>
#include <hidl/MQDescriptor.h>
#include <hidl/Status.h>

namespace vendor {
namespace mediatek {
namespace hardware {
namespace nvram {
namespace V1_0 {
namespace implementation {

using ::android::hidl::base::V1_0::DebugInfo;
using ::android::hidl::base::V1_0::IBase;
using ::vendor::mediatek::hardware::nvram::V1_0::INvram;
using ::android::hardware::hidl_array;
using ::android::hardware::hidl_memory;
using ::android::hardware::hidl_string;
using ::android::hardware::hidl_vec;
using ::android::hardware::Return;
using ::android::hardware::Void;
using ::android::sp;

struct Nvram : public INvram {
// Methods from ::vendor::mediatek::hardware::nvram::V1_0::INvram follow.
Return<void> readFileByName(const hidl_string& filename, uint32_t size, readFileByName_cb _hidl_cb) override;
Return<int8_t> writeFileByNamevec(const hidl_string& filename, uint32_t size, const hidl_vec<uint8_t>& data) override;

// Methods from ::android::hidl::base::V1_0::IBase follow.

};

extern "C" INvram* HIDL_FETCH_INvram(const char* name);

}// namespace implementation
}// namespace V1_0
}// namespace nvram
}// namespace hardware
}// namespace mediatek
}// namespace vendor

#endif// VENDOR_MEDIATEK_HARDWARE_NVRAM_V1_0_NVRAM_H</pre>
</div>
<h2>.cpp文件</h2>
路径
<div class="cnblogs_code">
<pre>vendor/mediatek/proprietary/external/libnvram/nvram_hidl/1.0/NvRam.cpp</pre>
</div>
代码：
<div class="cnblogs_code">
<pre>#include "Nvram.h"
#include <android-base/logging.h>
#include <log/log.h>
#include "libnvram.h"
#include "libnvram_log.h"
using std::string;

#define NVRAM_LOG(...) \
 do { \
 ALOGD(__VA_ARGS__); \
 } while (0)

namespace vendor {
namespace mediatek {
namespace hardware {
namespace nvram {
namespace V1_0 {
namespace implementation {
void covertVector2Array(std::vector<uint8_t> in, char* out) {
 int size = in.size();
 for(int i = 0; i < size; i++) {
 out = in.at(i);
 }
}

void covertArray2Vector(const char* in, int len, std::vector<uint8_t>& out) {
 out.clear();
 for(int i = 0; i < len; i++) {
 out.push_back(in);
 }
}

// Methods from ::vendor::mediatek::hardware::nvram::V1_0::INvram follow.
Return<void> Nvram::readFileByName(const hidl_string& filename, uint32_t size, readFileByName_cb _hidl_cb) {
// TODO implement
int pRecSize=0,pRecNum=0;
bool IsRead=1;
char *buff=NULL;
int file_lid = -1;
string result;
int i = 0;
char *nvramstr = (char*)malloc(2*size+1);
char *nvramptr = nvramstr;
char *cstr=new char;
if (nvramstr==NULL || size==0 || cstr==NULL) {
NVRAM_LOG("nvramstr==NULL\n");
 if(nvramstr!=NULL)
 free(nvramstr);
 if(cstr!=NULL)
 delete[] cstr;
return Void();
}

snprintf(cstr, filename.size()+1,"%s", filename.c_str());

file_lid = NVM_GetLIDByName(cstr);
if(file_lid < 0)
{
 NVRAM_LOG("Get LID by name fail! %s\n",cstr);
 free(nvramstr);
 delete[] cstr;
 return Void();
}

F_ID fd=NVM_GetFileDesc(file_lid,&pRecSize,&pRecNum,IsRead);
if (fd.iFileDesc==-1)
{
 LOG(ERROR) << "open file Error!";
 free(nvramstr);
 delete[] cstr;
 return Void();
}
LOG(ERROR) << "RecNum is "<<pRecNum;
//size=pRecSize*pRecNum;
buff=(char *)malloc(size);
if(buff == NULL)
{
 NVRAM_LOG("Malloc Error!\n");
 if(!NVM_CloseFileDesc(fd))
 NVRAM_LOG("close File error!\n");
 free(nvramstr);
 delete[] cstr;
 return Void();
}
if((ssize_t)size == read(fd.iFileDesc,buff,(ssize_t)size))
{
 if(NVM_CloseFileDesc(fd))
 {
 NVRAM_LOG("Read Done!Size is %d\n",size);
 //return buff;
 }
 else
 {
 NVRAM_LOG("Close file error!\n");
 free(buff);
 free(nvramstr);
 delete[] cstr;
 return Void();
 }
}
else
{
 NVRAM_LOG("read File error!\n");
 if(!NVM_CloseFileDesc(fd))
 NVRAM_LOG("close File error!\n");
 free(buff);
 free(nvramstr);
 delete[] cstr;
 return Void();
}

NVRAM_LOG("nvramstr buff%x, buff%x, buff%x, buff%x, buff%x, buff%x, buff%x, buff%x, buff%x \n",
 buff[0],buff[1],buff[2],buff[3],buff[4],buff[5],buff[6],buff[7],buff[8]);

for(i=0; i<(int)size; i++)
{
 nvramptr += sprintf(nvramptr, "%02X",buff);
}
sprintf(nvramptr,"\n");
*(nvramptr+1)='\0';

NVRAM_LOG("nvramstr %s\n",nvramstr);
_hidl_cb(nvramstr);
free(buff);
delete[] cstr;
return Void();
}

Return<int8_t> Nvram::writeFileByNamevec(const hidl_string& filename, uint32_t size, const hidl_vec<uint8_t>& data) {
// TODO implement
char *cstr_filename=new char;
char *cstr_data=new char;
if (cstr_data==NULL || size==0 || cstr_filename==NULL) {
NVRAM_LOG("cstr_data==NULL\n");
 if(cstr_data!=NULL)
 delete[] cstr_data;
 if(cstr_filename!=NULL)
 delete[] cstr_filename;
return int8_t {};
}
snprintf(cstr_filename, filename.size()+1,"%s", filename.c_str());
covertVector2Array(data, cstr_data);

int pRecSize=0,pRecNum=0,looptimes=0;
bool IsRead=0;
int file_lid = -1;

file_lid = NVM_GetLIDByName(cstr_filename);
if(file_lid < 0)
{
 NVRAM_LOG("Get LID by name fail!\n");
 delete[] cstr_data;
 delete[] cstr_filename;
 return int8_t {};
}

F_ID fd=NVM_GetFileDesc(file_lid,&pRecSize,&pRecNum,IsRead);
if (fd.iFileDesc==-1)
{
 NVRAM_LOG("open file Error!\n");
 delete[] cstr_data;
 delete[] cstr_filename;
 return int8_t {};
}
#if 0
if(size != pRecSize)
{
 NVRAM_LOG("Input size (%d) and RecSize (%d) not match!\n",size,pRecSize);
 if(!NVM_CloseFileDesc(fd))
 NVRAM_LOG("close File error!\n");
 //return 0;
 return int8_t {};
}
#endif

// GetFileDesc should return right pos and this would cause pro_info multi lids issue.
#if 0
if(0 != lseek(fd.iFileDesc,0,SEEK_SET)){
 NVRAM_LOG("lseek error!\n");
 if(!NVM_CloseFileDesc(fd))
 NVRAM_LOG("close File error!\n");
 return 0;
 }
#endif
looptimes = pRecNum;
NVRAM_LOG("RecNum is :%d\n",pRecNum);
while(looptimes--)
{
 if((ssize_t)size != write(fd.iFileDesc,cstr_data,(ssize_t)size))
 {
 NVRAM_LOG("write file error!\n");
 if(!NVM_CloseFileDesc(fd))
 NVRAM_LOG("close File error!\n");
 delete[] cstr_data;
 delete[] cstr_filename;
 return int8_t {};
 }
}
if(NVM_CloseFileDesc(fd))
{
 NVRAM_LOG("Write file Done!\n");
 delete[] cstr_data;
 delete[] cstr_filename;
 return int8_t {};
}
else
{
 NVRAM_LOG("close File error!\n");
 delete[] cstr_data;
 delete[] cstr_filename;
 return int8_t {};
}
//return int8_t {};
}

// Methods from ::android::hidl::base::V1_0::IBase follow.

INvram* HIDL_FETCH_INvram(const char* /* name */) {
return new Nvram();
}

}// namespace implementation
}// namespace V1_0
}// namespace nvram
}// namespace hardware
}// namespace mediatek
}// namespace vendor</pre>
</div>
<h2>经过系统编译后输出的so文件路径与jar文件路径</h2>
so路径
<div class="cnblogs_code">
<pre>out\target\product\A8385_JS04\obj\SHARED_LIBRARIES\vendor.mediatek.hardware.nvram@1.0.vendor_intermediates</pre>
</div>
jar路径
<div class="cnblogs_code">
<pre>out\target\common\obj\JAVA_LIBRARIES\vendor.mediatek.hardware.nvram-V1.0-java_intermediates</pre>
</div>
其中classes.jar就包含了INvram这个类，这里可以用反编译工具解包后查看
<img src="https://img2022.cnblogs.com/blog/1497956/202211/1497956-20221108143408766-1015074942.png" alt="">
 如图：
<img src="https://img2022.cnblogs.com/blog/1497956/202211/1497956-20221108143903706-942084213.png" alt="">
<h1>读写Nvram中SN号的操作流程</h1>
这里是Android studio上编译的工程
<h2>第一步导入系统编译Nvram的so与jar</h2>
<img src="https://img2022.cnblogs.com/blog/1497956/202211/1497956-20221108143625553-1960685561.png" alt="">
 在build里添加
<div class="cnblogs_code">
<pre>android {
compileSdk 28

defaultConfig {
 applicationId "com.xxx.xxxx"
 minSdk 26
 targetSdk 28
 versionCode 11
 versionName "1.10"

 testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
}
//添加
 sourceSets {
 main {
 jniLibs.srcDirs = ["libs"]
 }
}
//略...
}

dependencies {
implementation fileTree(dir: 'libs', include: ['*.jar'])//添加
implementation files('libs\\classes.jar')//添加
}</pre>
</div>
<h2>第二步项目必须是系统权限与系统签名</h2>
怎么实现请参考博客：https://www.cnblogs.com/guanxinjing/p/11410915.html
<h2>第三步项目必须架包framework</h2>
怎么实现请参考博客：https://www.cnblogs.com/guanxinjing/p/16613716.html
这里说一下为什么需要架framework，因为Android studio在编译的时候会检查到代码里没有IHwInterface这个类并且抛出编译异常，而这个类在framework中。
<div class="cnblogs_code">
<pre>android.os.IHwInterface;</pre>
</div>
这里在啰嗦一下为什么会检查这个类。因为在调用INvram.getService()方法的时候，INvram的基类是IBase
<img src="https://img2022.cnblogs.com/blog/1497956/202211/1497956-20221108143057128-1308081574.png" alt="">
 
而IBase继承了IHwInterface
 <img src="https://img2022.cnblogs.com/blog/1497956/202211/1497956-20221108143135438-108068402.png" alt="">
 
<h2>第四步修改系统工程里的代码，删除Nv写入保护的代码</h2>
系统工程修改文件路径
<div class="cnblogs_code">
<pre>vendor\mediatek\proprietary\bootable\bootloader\lk\platform\mt6765\write_protect.c</pre>
</div>
修改代码位置
<img src="https://img2022.cnblogs.com/blog/1497956/202211/1497956-20221108144246384-657102252.png" alt="">
 如果不删除写入保护set_write_protect，会出现在写入NV的时候如下报错
<img src="https://img2022.cnblogs.com/blog/1497956/202211/1497956-20221108145923965-1470317031.png" alt="">
<h2>第五步使用下面工具类读写SN号，或者Nv里的其他数据 </h2>
<div class="cnblogs_code">
<pre>import android.util.Log;
import com.android.internal.util.HexDump;
import java.nio.ByteBuffer;
import java.nio.CharBuffer;
import java.nio.charset.Charset;
import java.util.ArrayList;
import java.util.Arrays;
import vendor.mediatek.hardware.nvram.V1_0.INvram;

/**
*
* /vendor/nvdata/APCFG/APRDEB/BT_Addr
* /vendor/nvdata/APCFG/APRDCL/AUXADC
* /vendor/nvdata/media/CAMERA_Para
* /vendor/nvdata/media/CAMERA_3A
* /vendor/nvdata/media/CAMERA_SHADING
* /vendor/nvdata/media/CAMERA_DEFECT
* /vendor/nvdata/media/CAMERA_SENSOR
* /vendor/nvdata/media/CAMERA_LENS
* /vendor/nvdata/APCFG/APRDCL/UART
* /vendor/nvdata/APCFG/APRDCL/FACTORY
* /vendor/nvdata/APCFG/APRDCL/BWCS
* /vendor/nvdata/APCFG/APRDCL/HWMON_ACC
* /vendor/nvdata/APCFG/APRDCL/HWMON_GYRO
* /vendor/nvdata/media/Voice_Recognize_Param
* /vendor/nvdata/media/Audio_AudEnh_Control_Opt
* /vendor/nvdata/media/Audio_VOIP_Param
* /vendor/nvdata/APCFG/APRDCL/HWMON_PS
* /vendor/nvdata/APCFG/APRDCL/MD_Type
* /vendor/nvdata/APCFG/APRDCL/EXT_MD_Type
* /vendor/nvdata/APCFG/APRDCL/SDIO
* /vendor/nvdata/media/CAMERA_VERSION
* /vendor/nvdata/media/CAMERA_FEATURE
* /vendor/nvdata/media/CAMERA_GEOMETRY
* /vendor/nvdata/APCFG/APRDCL/MD_SBP
* /vendor/nvdata/media/CAMERA_SHADING2
* /vendor/nvdata/media/CAMERA_PLINE
* /vendor/nvdata/media/CAMERA_AF
* /vendor/nvdata/media/CAMERA_FLASH_CALIBRATION
* /vendor/nvdata/media/Audio_Sph
* /vendor/nvdata/APCFG/APRDEB/GPS
* /vendor/nvdata/media/Audio_CompFlt
* /vendor/nvdata/media/Audio_Effect
* /vendor/nvdata/APCFG/APRDEB/WIFI
* /vendor/nvdata/APCFG/APRDEB/WIFI_CUSTOM
* /vendor/nvdata/media/Audio_Sph_Med
* /vendor/nvdata/media/Audio_Vol_custom
* /vendor/nvdata/media/Sph_Dual_Mic
* /vendor/nvdata/media/Audio_Wb_Sph
* /vendor/nvdata/APCFG/APRDEB/PRODUCT_INFO
* /vendor/nvdata/media/Headphone_CompFlt
* /vendor/nvdata/media/Audio_gain_table
* /vendor/nvdata/media/Audio_ver1_Vol_custom
* /vendor/nvdata/media/Audio_Hd_Record_Param
* /vendor/nvdata/media/Audio_Hd_Record_Scene_Table
* /vendor/nvdata/media/Audio_Buffer_DC_Calibration_Param
* /vendor/nvdata/media/VibSpk_CompFlt
* /vendor/nvdata/media/MusicDRC_CompFlt
* /vendor/nvdata/media/RingToneDRC_CompFlt
* /vendor/nvdata/media/Audio_MAGI_CONFERENCE
* /vendor/nvdata/media/Audio_HAC_Param
*/
public class SNParamUtils {
public static final String PRODUCT_INFO_FILENAME = "/vendor/nvdata/APCFG/APRDEB/PRODUCT_INFO";
private static final int SN_LENGTH = 32;

public static void writeSn(String sn) {
 char sn_chars[] = sn.toCharArray();
 byte sn_bytes[] = getBytes(sn_chars);
 try {
 INvram agent = INvram.getService();
 if (agent != null) {
 ArrayList<Byte> dataArray = new ArrayList<>();
 for (byte b : sn_bytes) {
 dataArray.add(new Byte(b));
 }
 int ret_1 = agent.writeFileByNamevec(PRODUCT_INFO_FILENAME, SN_LENGTH, dataArray);
 if (ret_1 == 0) {
 Log.e("zh", "writeSn success " + ret_1);
 } else {
 Log.e("zh", "writeSn failed" + ret_1);
 }
 } else {
 Log.e("zh", "writeSn: agent null");
 }
 } catch (Exception e) {
 Log.e("zh", "writeSn exception:" + e.getLocalizedMessage());
 e.printStackTrace();
 }
}

public static String readSn() {
 int targets = 0;
 try {
 String buff = null;
 INvram agent = INvram.getService();

 if (agent != null) {
 buff = agent.readFileByName(PRODUCT_INFO_FILENAME, SN_LENGTH);
 Log.e("zh", "buff: " + buff );
 }
 byte[] buffArr = HexDump.hexStringToByteArray(buff.substring(0, buff.length() - 1));
 targets = (buffArr & 0xff) | ((buffArr << 8) & 0xff00) | ((buffArr << 24) >>> 8) | (buffArr << 24);
 Log.e("zh","readSn: chars=>" + Arrays.toString(getChars(buffArr)) + ", targets == " + targets);
 Log.e("zh","readSn: bytes=>" + Arrays.toString((buffArr)) + ", targets == " + targets);
 return String.valueOf(getChars(buffArr));
 } catch (Exception e) {
 Log.e("zh","readSn exception:" + e.getLocalizedMessage());
 e.printStackTrace();
 }
 return "123456789";
}

private static char[] getChars(byte[] bytes) {
 Charset cs = Charset.forName("UTF-8");
 ByteBuffer bb = ByteBuffer.allocate(bytes.length);
 bb.put(bytes);
 bb.flip();
 CharBuffer cb = cs.decode(bb);
 return cb.array();
}

private static byte[] getBytes(char[] chars) {
 Charset cs = Charset.forName("UTF-8");
 CharBuffer cb = CharBuffer.allocate(chars.length);
 cb.put(chars);
 cb.flip();
 ByteBuffer bb = cs.encode(cb);
 return bb.array();
}
}</pre>
</div>
<h1>假如你是系统工程编译apk</h1>
<h3>可以在apk工程的android.mk里直接导入，不需要以上的第一步到第三步，但是依然需要第四步与第五步</h3>
<pre class="highlighter-hljs" data-dark-theme="true"><code>LOCAL_STATIC_JAVA_LIBRARIES := vendor.mediatek.hardware.nvram-V1.0-java</code></pre>
<div class="cnblogs_code">
<pre>LOCAL_PATH:= $(call my-dir)
include $(CLEAR_VARS)

LOCAL_MODULE_TAGS := optional
LOCAL_CERTIFICATE := platform

# Add static library for nvram
# LOCAL_STATIC_JAVA_LIBRARIES := vendor.mediatek.hardware.nvram-V1.1-java-static
LOCAL_STATIC_JAVA_LIBRARIES := vendor.mediatek.hardware.nvram-V1.0-java
LOCAL_SRC_FILES := $(call all-subdir-java-files)
LOCAL_PACKAGE_NAME := JNvRAM_V11
LOCAL_PRIVATE_PLATFORM_APIS := true
include $(BUILD_PACKAGE)</pre>
</div>
<h1>MTK平台如何用Build.getSerial()方法读取写入的SN号</h1>
这里直接复制MTK论坛那边的开发回复(下面提是MTK的写号工具SN Write，但是我们这个写NV的方法同样适用)：
在/vendor/mediatek/proprietary/bootable/bootloader/lk/app/mt_boot/mt_boot.c 中，将 #define SERIAL_NUM_FROM_BARCODE  宏定义打开 这时SN Write工具写Barcode即可，其他无需修改。 这是最简单的方式，相当于serial no取Barcode空间的值。
<img src="https://img2023.cnblogs.com/blog/1497956/202212/1497956-20221219114049817-1344626868.png" alt="">
<h1>在NV中读写WiFi的Mac地址</h1>
请注意！在Android10版本以后，WiFi已经默认使用随机mac地址，意思是说，哪怕你写到了NV中，在WifiManager中也不会读取到，这需要你手动设置或者修改代码将，下面的选项从随机Mac地址修改成固定设备的Mac地址。如下图位置：
<img src="https://img2023.cnblogs.com/blog/1497956/202310/1497956-20231020144621293-664473884.png">
<img src="https://img2023.cnblogs.com/blog/1497956/202310/1497956-20231020144650235-930652558.png">
代码部分：
其他流程与上面一样，这里直接提供读写代码。 
<pre class="language-java highlighter-hljs" data-dark-theme="true"><code>import android.app.Application;
import android.content.Context;
import android.net.wifi.WifiManager;
import android.util.Log;
import com.android.internal.util.HexDump;
import java.lang.reflect.Method;
import java.nio.ByteBuffer;
import java.nio.CharBuffer;
import java.nio.charset.Charset;
import java.util.ArrayList;
import java.util.StringTokenizer;
import vendor.mediatek.hardware.nvram.V1_0.INvram;

public class MacParamUtils {
public static final String MAC_ADDRESS_FILENAME = "/vendor/nvdata/APCFG/APRDEB/WIFI";
private static final int MAC_ADDRESS_OFFSET = 4;
private static final int MAC_ADDRESS_DIGITS = 6;

/**
* 通过WifiManager获取WiFi Mac地址
*/
public static String getMACAddress(Application application) {
 try {
 WifiManager wifiManager = (WifiManager)application.getSystemService(Context.WIFI_SERVICE);
 Method getFactoryMacAddresses = wifiManager.getClass().getMethod("getFactoryMacAddresses");
 String[] macAddresses= (String[]) getFactoryMacAddresses.invoke(wifiManager);
 String macAddress = "";
 if (macAddresses.length > 0) {
 macAddress = macAddresses;
 }
 return macAddress;
 } catch (Exception e) {
 return null;
 }
}

/**
* 直接从NV中读取Mac地址
* @return
*/
public static String getWifiMacFromNvram() {
 StringBuffer nvramBuf = new StringBuffer();
 try {
 int i = 0;
 String buff = null;
 INvram agent = INvram.getService();
 if (agent == null) {
 Log.e("zh", "NvRAMAgent is null");
 return ""; }
 try {
 buff = agent.readFileByName(MAC_ADDRESS_FILENAME, MAC_ADDRESS_OFFSET + MAC_ADDRESS_DIGITS);
 } catch (Exception e) {
 e.printStackTrace();
 return "";
 }
 Log.e("zh", "Raw data:" + buff);
 if (buff.length() < 2 * (MAC_ADDRESS_OFFSET + MAC_ADDRESS_DIGITS)) {
 return "";
 }
 // Remove the \0 special character.
 int macLen = buff.length() - 1;
 for (i = MAC_ADDRESS_OFFSET * 2; i < macLen; i += 2) {
 if ((i + 2) < macLen) {
 nvramBuf.append(buff.substring(i, i + 2));
 nvramBuf.append(":");
 } else {
 nvramBuf.append(buff.substring(i));
 }
 }
 } catch (Exception e) {
 e.printStackTrace();
 return "";
 }
 return nvramBuf.toString();
}

/**
* 更新WiFi Mac地址到NV中
* @param mac
* @return
*/
public static int updateWifiMacToNvram(String mac){
 try {
 int i = 0;
 INvram agent = INvram.getService();
 byte[] macAddr = new byte;
 if (agent == null) {
 Log.e("zh", "NvRAMAgent is null");
 return 0;
 }
 //parse mac address firstly
 StringTokenizer txtBuffer = new StringTokenizer(mac, ":");
 while (txtBuffer.hasMoreTokens()) {
 macAddr = (byte) Integer.parseInt(txtBuffer.nextToken(), 16);
 i++;
 }
 if(i != MAC_ADDRESS_DIGITS){
 Log.e("zh", "Wrong length of macAddr:" + i);
 return 0;
 }
 String buff = null;
 try {
 buff = agent.readFileByName(MAC_ADDRESS_FILENAME, MAC_ADDRESS_OFFSET + MAC_ADDRESS_DIGITS);
 } catch (Exception e) {
 e.printStackTrace();
 return 0;
 }
 byte[] buffArr = HexDump.hexStringToByteArray(buff.substring(0, buff.length() - 1));
 for (i = 0; i < MAC_ADDRESS_DIGITS; i ++) {
 buffArr = macAddr;
 }
 ArrayList<Byte> dataArray = new ArrayList<Byte>(MAC_ADDRESS_OFFSET + MAC_ADDRESS_DIGITS);
 for (i = 0; i < MAC_ADDRESS_OFFSET + MAC_ADDRESS_DIGITS; i++) {
 dataArray.add(i, new Byte(buffArr));
 }
 int flag = 0;
 try {
 flag = agent.writeFileByNamevec(MAC_ADDRESS_FILENAME,MAC_ADDRESS_OFFSET + MAC_ADDRESS_DIGITS,dataArray);
 return flag;
 } catch (Exception e) {
 e.printStackTrace();
 return 0;
 }
 }catch (Exception e) {
 e.printStackTrace();
 }
 return 0;
}

private static char[] getChars(byte[] bytes) {
 Charset cs = Charset.forName("UTF-8");
 ByteBuffer bb = ByteBuffer.allocate(bytes.length);
 bb.put(bytes);
 bb.flip();
 CharBuffer cb = cs.decode(bb);
 return cb.array();
}

private static byte[] getBytes(char[] chars) {
 Charset cs = Charset.forName("UTF-8");
 CharBuffer cb = CharBuffer.allocate(chars.length);
 cb.put(chars);
 cb.flip();
 ByteBuffer bb = cs.encode(cb);
 return bb.array();
}
}</code></pre>
 
 
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Android系统开发 android8之后版本读写Nvram