Android Recovery 源码解析和界面定制

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；

1. 首先是我们熟悉的恢复工厂设置 –> wipe_data wipe_cache
2. 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；
3. 可以进行系统的系统的OTA升级，本质上同手动刷包一样；

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/recovery/root/目录；

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

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 voidget_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;}

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"

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 };

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;};

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 ;}

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 $(CLEAR_VARS)LOCAL_MODULE_TAGS := engLOCAL_C_INCLUDES += bootable/recoveryLOCAL_SRC_FILES := recovery_ui.cpp# should match TARGET_RECOVERY_UI_LIB set in BoardConfig.mkLOCAL_MODULE := librecovery_ui_$(TARGET_PRODUCT)include $(BUILD_STATIC_LIBRARY)