本文我们主要了解学习Android系统中recovery系统的功能知识与系统实现源码。
目录
1. Recovery主要功能
2. 源码路径和主要原文件
3. recovery.cpp命令行参数
4. main 函数
5. 界面定制实现Recovery UI
6. 实现头部显示和列表项
7. 实现ScreenRecoveryUI
8. 实现设备类
9. 添加编译实现
1.Recovery主要功能
深入了解recovery源码前，先浏览下recovery能够给我们提供哪些功能；
- 首先是我们熟悉的恢复工厂设置 –> wipe_data wipe_cache
- 刷升级包，可以通过sdcard升级，通常说的卡刷，有些还提供ADB sideload升级；
- 可以进行系统的系统的OTA升级，本质上同手动刷包一样；
2.源码路径和主要原文件
在Android源码环境中，recovery的源码主要在bootable/recovery文件下，另外再device目录下，会根据各个设备定制自己的接口以及UI界面，也就是文章后半部分分析的界面定制的内容；
在bootable/recovery目录下，主要的源文件有：
LOCAL_SRC_FILES := \
adb_install.cpp \
asn1_decoder.cpp \
bootloader.cpp \
device.cpp \
fuse_sdcard_provider.c \
install.cpp \
recovery.cpp \
roots.cpp \
screen_ui.cpp \
ui.cpp \
verifier.cpp \
该部分代码在编译后，会统一输出到 out/target/product/arbutus/recovery/root/目录；
3.recovery.cpp命令行参数
recovery最后是编译成一个可执行的命令，放在recovery文件系统中的/sbin/recovery；所以我们可以在终端中直接运行该命令，具体的参数如下：
--send_intent=anystring - 传递给recovery的信息
--adbd - adb sideload升级
--update_package=path - 指定OTA升级包
--wipe_data - 清楚用户数据并重启
--wipe_cache - 清楚缓存并重启
--set_encrypted_filesystem=on|off - 使能或者关闭文件系统加密
--just_exit - 退出并重启
4.main 函数
从main入口函数分析recovery的主要源码：
输出重定向
redirect_stdio(TEMPORARY_LOG_FILE);
//redirect log to serial output
#ifdef LogToSerial
freopen("/dev/ttyFIQ0", "a", stdout); setbuf(stdout, NULL);
freopen("/dev/ttyFIQ0", "a", stderr); setbuf(stderr, NULL);
#endif
这部分代码很容易理解，主要作用是输出log到/tem/recovery.log文件中
执行adb sideload分支
if (argc == 2 && strcmp(argv[1], "--adbd") == 0) {
adb_main(0, DEFAULT_ADB_PORT);
return 0;
}
判断命令行参数是否为–adbd，并执行adb_main函数，这部分代码在后续adb_install.cpp中分析；
填充fstab结构体
在main函数中调用 load_volume_table()，读取/etc/recovery.emmc.fstab文件内容，并填充fstab结构体，但是并没有执行挂载操作；
load_volume_table函数在roots.cpp文件中，也是很容易理解：
void load_volume_table()
{
...
int emmcState = getEmmcState();//判断是否为emmc设备
if(emmcState) {
fstab = fs_mgr_read_fstab("/etc/recovery.emmc.fstab");
}else {
fstab = fs_mgr_read_fstab("/etc/recovery.fstab");
}
...
//读取文件中每个条目内容，填充fstab结构体
ret = fs_mgr_add_entry(fstab, "/tmp", "ramdisk", "ramdisk");
...
//日志打印fstable信息
printf("recovery filesystem table\n");
printf("=========================\n");
for (i = 0; i < fstab->num_entries; ++i) {
Volume* v = &fstab->recs[i];
printf(" %d %s %s %s %lld\n", i, v->mount_point, v->fs_type,
v->blk_device, v->length);
}
printf("\n");
}
读取控制参数
recovery 和 bootloader 必须通过内存的一个特定分区，才能进行相互的通信，这个分区一般是/misc；
对应的信息数据结构体为bootloader_message；
参照源码中bootloader_message的注释
struct bootloader_message {
char command[32];//bootloader 启动时读取改数据，决定是否进入recovery模式
char status[32];//由bootloader进行更新，标识升级的结果；
char recovery[768];//由Android系统进行写入，recovery从中读取信息；
char stage[32];
char reserved[224];
};
recovery 根据命令行参数，再从/misc分区中解析出对应的参数，进行后续的操作，具体的调用函数为get_args(&argc, &argv)；
static void
get_args(int *argc, char ***argv) {
struct bootloader_message boot;//参数结构体
memset(&boot, 0, sizeof(boot));
get_bootloader_message(&boot); // 具体的读取信息的函数，可能为空的情况
stage = strndup(boot.stage, sizeof(boot.stage));
...
// 如果上述情况为空，则从/cache/recovery/command获取参数，其中COMMAND_FILE=/cache/recovery/command
if (*argc <= 1) {
FILE *fp = fopen_path(COMMAND_FILE, "r");
if (fp != NULL) {
char *token;
char *argv0 = (*argv)[0];
*argv = (char **) malloc(sizeof(char *) * MAX_ARGS);
(*argv)[0] = argv0; // use the same program name
char buf[MAX_ARG_LENGTH];
for (*argc = 1; *argc < MAX_ARGS; ++*argc) {
if (!fgets(buf, sizeof(buf), fp)) break;
token = strtok(buf, "\r\n");
if (token != NULL) {
(*argv)[*argc] = strdup(token); // Strip newline.
} else {
--*argc;
}
}
check_and_fclose(fp, COMMAND_FILE);
LOGI("Got arguments from %s\n", COMMAND_FILE);
}
}
//把从/cache/recovery/command获取参数重新写回到/misc分区
// --> write the arguments we have back into the bootloader control block
// always boot into recovery after this (until finish_recovery() is called)
strlcpy(boot.command, "boot-recovery", sizeof(boot.command));
strlcpy(boot.recovery, "recovery\n", sizeof(boot.recovery));
int i;
for (i = 1; i < *argc; ++i) {
strlcat(boot.recovery, (*argv)[i], sizeof(boot.recovery));
strlcat(boot.recovery, "\n", sizeof(boot.recovery));
}
set_bootloader_message(&boot);
}
解析命令行参数
while ((arg = getopt_long(argc, argv, "", OPTIONS, NULL)) != -1) {
switch (arg) {
case 'f': factory_mode = optarg; bFactoryMode = true; break;
case 'i': send_intent = optarg; break;
case 'u': update_package = optarg; break;
case 'w': should_wipe_data = true; break;
case 'k': update_rkimage = optarg;break;
case 'c': should_wipe_cache = true; break;
case 't': show_text = true; break;
case 's': sideload = true; break;
case 'a': sideload = true; sideload_auto_reboot = true; break;
case 'x': just_exit = true; break;
case 'l': locale = optarg; break;
case 'g': {
if (stage == NULL || *stage == '\0') {
char buffer[20] = "1/";
strncat(buffer, optarg, sizeof(buffer)-3);
stage = strdup(buffer);
}
break;
}
case 'f'+'w': //fw_update
if((optarg)&&(!sdboot_update_package)){
sdboot_update_package = strdup(optarg);
}
break;
case 'd': //demo_copy
if((optarg)&&(! demo_copy_path)){
demo_copy_path = strdup(optarg);
}
break;
case 'p': shutdown_after = true; break;
case 'r': reason = optarg; break;
case 'w'+'a': { should_wipe_all = should_wipe_data = should_wipe_cache = true;show_text = true;} break;
case '?':
LOGE("Invalid command argument\n");
continue;
}
}
这部分代码很简单，就是通过getopt_long进行命令行参数的解析并赋值；
显示界面和功能选项
接下来就是创建device，显示对应UI界面和功能选项；
Device* device = make_device();//可以自己实现一个设备
ui = device->GetUI();
gCurrentUI = ui;//赋值ui界面
ui->SetLocale(locale);//获取归属地信息
ui->Init();//初始化，可以重载，在init中实现相应功能
ui->SetStage(st_cur, st_max);
ui->SetBackground(RecoveryUI::NONE);
进行分区挂载操作
ensure_path_mounted
int ensure_path_mounted(const char* path) {
...
Volume* v = volume_for_path(path);//根据路径名获取分区信息
...
int result;
result = scan_mounted_volumes();
const MountedVolume* mv =
find_mounted_volume_by_mount_point(v->mount_point);//根据挂载点，获取已挂载分区的信息，如果不为空，说明已经成功挂载
if (mv) {
// volume is already mounted
return 0;
}
result = mkdir(v->mount_point, 0755); // 创建对应目录，确保目录存在，也有可能目录已经存在
if (result!=0)
{
printf("failed to create %s dir,err=%s!\n",v->mount_point,strerror(errno));
}
// 根据文件系统类型，执行mount操作
if (strcmp(v->fs_type, "yaffs2") == 0) {
// mount an MTD partition as a YAFFS2 filesystem.
mtd_scan_partitions();
const MtdPartition* partition;
partition = mtd_find_partition_by_name(v->blk_device);
if (partition == NULL) {
LOGE("failed to find \"%s\" partition to mount at \"%s\"\n",
v->blk_device, v->mount_point);
return -1;
}
return mtd_mount_partition(partition, v->mount_point, v->fs_type, 0);
} else if (strcmp(v->fs_type, "ext4") == 0 ||
strcmp(v->fs_type, "ext3") == 0) {
result = mount(v->blk_device, v->mount_point, v->fs_type,
MS_NOATIME | MS_NODEV | MS_NODIRATIME, "");
if (result == 0) return 0;
LOGE("failed to mount %s %s (%s)\n", v->mount_point, v->blk_device, strerror(errno));
return -1;
} else if (strcmp(v->fs_type, "vfat") == 0) {
result = mount(v->blk_device, v->mount_point, v->fs_type,
MS_NOATIME | MS_NODEV | MS_NODIRATIME, "shortname=mixed,utf8");
if (result == 0) return 0;
LOGW("trying mount %s to ntfs\n", v->blk_device);
result = mount(v->blk_device, v->mount_point, "ntfs",
MS_NOATIME | MS_NODEV | MS_NODIRATIME, "");
if (result == 0) return 0;
char *sec_dev = v->fs_options;
if(sec_dev != NULL) {
char *temp = strchr(sec_dev, ',');
if(temp) {
temp[0] = '\0';
}
result = mount(sec_dev, v->mount_point, v->fs_type,
MS_NOATIME | MS_NODEV | MS_NODIRATIME, "shortname=mixed,utf8");
if (result == 0) return 0;
LOGW("trying mount %s to ntfs\n", sec_dev);
result = mount(sec_dev, v->mount_point, "ntfs",
MS_NOATIME | MS_NODEV | MS_NODIRATIME, "");
if (result == 0) return 0;
}
LOGE("failed to mount %s (%s)\n", v->mount_point, strerror(errno));
return -1;
}else if (strcmp(v->fs_type, "ntfs") == 0) {
LOGW("trying mount %s to ntfs\n", v->blk_device);
result = mount(v->blk_device, v->mount_point, "ntfs",
MS_NOATIME | MS_NODEV | MS_NODIRATIME, "");
if (result == 0) return 0;
LOGE("failed to mount %s (%s)\n", v->mount_point, strerror(errno));
return -1;
}
LOGE("unknown fs_type \"%s\" for %s\n", v->fs_type, v->mount_point);
return -1;
}
5.界面定制实现Recovery UI
在自己的设备目录下：device/vendor/recovery/recovery_ui.cpp
#include <linux/input.h>
#include <sys/stat.h>
#include <errno.h>
#include <string.h>
#include "common.h"
#include "device.h"
#include "screen_ui.h"
6.实现头部显示和列表项
const char* HEADERS[] = {
"Volume up/down to move highlight;",
"power button to select.",
"",
NULL
};
const char* ITEMS[] ={
"reboot system now",
//"apply update from ADB",
"apply update from external storage",
"update rkimage from external storage",
"apply update from cache",
"wipe data/factory reset",
"wipe cache partition",
"recovery system from backup",
NULL
};
7.实现ScreenRecoveryUI
class DeviceUI : public ScreenRecoveryUI {
public:
DeviceUI () :
consecutive_power_keys(0) {
}
//实现自己的识别key类型的功能，可以为不同的输入设备适配recovery功能
virtual KeyAction CheckKey(int key) {
if (IsKeyPressed(KEY_POWER) && key == KEY_VOLUMEUP) {
return TOGGLE;
}
if (key == KEY_POWER) {
++consecutive_power_keys;
if (consecutive_power_keys >= 7) {
return REBOOT;
}
} else {
consecutive_power_keys = 0;
}
return ENQUEUE;
}
private:
int consecutive_power_keys;
};
8.实现设备类
class MyDevice : public Device {
public:
RkDevice() :
ui(new DeviceUI ) {
}
RecoveryUI* GetUI() { return ui; }
int HandleMenuKey(int key_code, int visible) {
if (visible) {
switch (key_code) {
case KEY_DOWN:
case KEY_VOLUMEDOWN:
return kHighlightDown;
case KEY_UP:
case KEY_VOLUMEUP:
return kHighlightUp;
case KEY_ENTER:
case KEY_POWER:
return kInvokeItem;
}
}
return kNoAction;
}
BuiltinAction InvokeMenuItem(int menu_position) {
switch (menu_position) {
case 0: return REBOOT;
//case 1: return APPLY_ADB_SIDELOAD;
case 1: return APPLY_EXT;
case 2: return APPLY_INT_RKIMG;
case 3: return APPLY_CACHE;
case 4: return WIPE_DATA;
case 5: return WIPE_CACHE;
case 6: return RECOVER_SYSTEM;
default: return NO_ACTION;
}
}
const char* const* GetMenuHeaders() { return HEADERS; }
const char* const* GetMenuItems() { return ITEMS; }
private:
RecoveryUI* ui;
};
//创建自己实现的设备
Device* make_device() {
return new MyDevice ;
}
9.添加编译实现
主要是覆盖TARGET_RECOVERY_UI_LIB，输出到/out/…./recovery/root目录下：
Android.mk
LOCAL_PATH := $(call my-dir)
include $(CLEAR_VARS)
LOCAL_MODULE_TAGS := eng
LOCAL_C_INCLUDES += bootable/recovery
LOCAL_SRC_FILES := recovery_ui.cpp
# should match TARGET_RECOVERY_UI_LIB set in BoardConfig.mk
LOCAL_MODULE := librecovery_ui_$(TARGET_PRODUCT)
include $(BUILD_STATIC_LIBRARY)
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