在Tiny4412的Android5.0源代码中:

bootable/recovery/recovery.cpp是recovery程序的主文件。

仔细一看，对比了其它平台的recovery源代码，除了MTK对Recovery做了相应的定制外，其它的平台几乎没有看到，关于MTK平台，后续再分析。

关于Android5.0的recovery，有什么功能，在recovery.cpp中开头就已经做了详细的说明，我们来看看:

/*
 * The recovery tool communicates with the main system through /cache files.
 *   /cache/recovery/command - INPUT - command line for tool, one arg per line
 *   /cache/recovery/log - OUTPUT - combined log file from recovery run(s)
 *   /cache/recovery/intent - OUTPUT - intent that was passed in
 *
 * The arguments which may be supplied in the recovery.command file:
 *   --send_intent=anystring - write the text out to recovery.intent
 *   --update_package=path - verify install an OTA package file
 *   --wipe_data - erase user data (and cache), then reboot
 *   --wipe_cache - wipe cache (but not user data), then reboot
 *   --set_encrypted_filesystem=on|off - enables / diasables encrypted fs
 *   --just_exit - do nothing; exit and reboot
 *
 * After completing, we remove /cache/recovery/command and reboot.
 * Arguments may also be supplied in the bootloader control block (BCB).
 * These important scenarios must be safely restartable at any point:
 *
 * FACTORY RESET
 * 1. user selects "factory reset"
 * 2. main system writes "--wipe_data" to /cache/recovery/command
 * 3. main system reboots into recovery
 * 4. get_args() writes BCB with "boot-recovery" and "--wipe_data"
 *    -- after this, rebooting will restart the erase --
 * 5. erase_volume() reformats /data
 * 6. erase_volume() reformats /cache
 * 7. finish_recovery() erases BCB
 *    -- after this, rebooting will restart the main system --
 * 8. main() calls reboot() to boot main system
 *
 * OTA INSTALL
 * 1. main system downloads OTA package to /cache/some-filename.zip
 * 2. main system writes "--update_package=/cache/some-filename.zip"
 * 3. main system reboots into recovery
 * 4. get_args() writes BCB with "boot-recovery" and "--update_package=..."
 *    -- after this, rebooting will attempt to reinstall the update --
 * 5. install_package() attempts to install the update
 *    NOTE: the package install must itself be restartable from any point
 * 6. finish_recovery() erases BCB
 *    -- after this, rebooting will (try to) restart the main system --
 * 7. ** if install failed **
 *    7a. prompt_and_wait() shows an error icon and waits for the user
 *    7b; the user reboots (pulling the battery, etc) into the main system
 * 8. main() calls maybe_install_firmware_update()
 *    ** if the update contained radio/hboot firmware **:
 *    8a. m_i_f_u() writes BCB with "boot-recovery" and "--wipe_cache"
 *        -- after this, rebooting will reformat cache & restart main system --
 *    8b. m_i_f_u() writes firmware image into raw cache partition
 *    8c. m_i_f_u() writes BCB with "update-radio/hboot" and "--wipe_cache"
 *        -- after this, rebooting will attempt to reinstall firmware --
 *    8d. bootloader tries to flash firmware
 *    8e. bootloader writes BCB with "boot-recovery" (keeping "--wipe_cache")
 *        -- after this, rebooting will reformat cache & restart main system --
 *    8f. erase_volume() reformats /cache
 *    8g. finish_recovery() erases BCB
 *        -- after this, rebooting will (try to) restart the main system --
 * 9. main() calls reboot() to boot main system
 */

在这段英文注释里，详细的说明了factory_reset(Android的恢复出厂设置功能)的流程以及OTA系统更新的流程。

在这段注释得最前面说得很明白，我们只要往/cache/recovery/command中写入相应的命令：

 * The arguments which may be supplied in the recovery.command file:
 *   --send_intent=anystring - write the text out to recovery.intent
 *   --update_package=path - verify install an OTA package file
 *   --wipe_data - erase user data (and cache), then reboot
 *   --wipe_cache - wipe cache (but not user data), then reboot
 *   --set_encrypted_filesystem=on|off - enables / diasables encrypted fs
 *   --just_exit - do nothing; exit and reboot

比如写入: 

--update_package=path(对应的OTA更新的路径)

例如:

--update_package=/mnt/external_sd/xxx.zip

将这条命令写入后，再重启Android系统，recovery检测到有这个命令存在，就会去搜索这个路径，然后将这个路径做路径转换，接下来获取转换后的路径后，就挂载这个路径，然后挂载这个路径，获取OTA包，解包，校验，然后最后实现真正的更新。

如果我们往这个文件写入: --wipe_data

那么就会做出厂设置，格式化/data分区的内容。

接下来，我们来看看代码，从main函数开始分析:

进入main函数后，会将recovery产生的log信息重定向到/tmp/recovery.log这个文件里，具体代码实现如下：

//重定向标准输出和标准出错到/tmp/recovery.log 这个文件里
	//static const char *TEMPORARY_LOG_FILE = "/tmp/recovery.log";
    redirect_stdio(TEMPORARY_LOG_FILE);

redirect_stdio函数源代码:

static void redirect_stdio(const char* filename) {
    // If these fail, there's not really anywhere to complain...
    freopen(filename, "a", stdout); setbuf(stdout, NULL);
    freopen(filename, "a", stderr); setbuf(stderr, NULL);
}

我们看到，所有产生来自stdout和stderr的信息会使用freopen这个函数重定向到/tmp/recovery.log这个文件里。

stdout就是标准输出，stdout就是标准出错。标准输出就是我们平时使用的printf输出的信息。

当然也可以使用fprintf(stdout,"hello world\n");也是一样的

标准出错就是fprintf(stderr,"hello world!\n");类似的代码。

接下下来，将会判断是否使用adb的sideload来传入，通过参数--adbd来判断：

    // If this binary is started with the single argument "--adbd",
    // instead of being the normal recovery binary, it turns into kind
    // of a stripped-down version of adbd that only supports the
    // 'sideload' command.  Note this must be a real argument, not
    // anything in the command file or bootloader control block; the
    // only way recovery should be run with this argument is when it
    // starts a copy of itself from the apply_from_adb() function.
    if (argc == 2 && strcmp(argv[1], "--adbd") == 0) {
        adb_main();
        return 0;
    }

做完这些步骤以后，会初始化并装载recovery的分区表recovery.fstab，然后挂载/cache/recovery/last_log这个文件，用来输出log。

    printf("Starting recovery (pid %d) on %s", getpid(), ctime(&start));
	//装载recovery的分区表recovery.fstab
    load_volume_table();
	//在recovery中挂载/cache/recovery/last_log这个文件
	//#define LAST_LOG_FILE "/cache/recovery/last_log"
    ensure_path_mounted(LAST_LOG_FILE);
    rotate_last_logs(KEEP_LOG_COUNT);

这里主要看如何装载分区表的流程,先来看看recovery.fstab

/dev/block/by-name/boot         /boot         emmc     defaults                                                                defaults
/dev/block/by-name/recovery     /recovery     emmc     defaults                                                                defaults
/dev/block/by-name/splashscreen /splashscreen emmc     defaults                                                                defaults
/dev/block/by-name/fastboot     /fastboot     emmc     defaults                                                                defaults
/dev/block/by-name/misc         /misc         emmc     defaults                                                                defaults
/dev/block/by-name/system       /system       ext4     ro,noatime                                                              wait
/dev/block/by-name/cache        /cache        ext4     nosuid,nodev,noatime,barrier=1,data=ordered                             wait,check
/dev/block/by-name/userdata     /data         ext4     nosuid,nodev,noatime,discard,barrier=1,data=ordered,noauto_da_alloc     wait,check
/dev/block/by-name/factory      /factory      ext4     nosuid,nodev,noatime,barrier=1,data=ordered                             wait

接下来看是如果挂载的：

void load_volume_table()
{
    int i;
    int ret;
	//读recovery.fstab 这个分区表
    fstab = fs_mgr_read_fstab("/etc/recovery.fstab");
    if (!fstab) {
        LOGE("failed to read /etc/recovery.fstab\n");
        return;
    }
	//将对应的信息加入到一条链表中
    ret = fs_mgr_add_entry(fstab, "/tmp", "ramdisk", "ramdisk");
	//如果load到的分区表为空，后面做释放操作
    if (ret < 0 ) {
        LOGE("failed to add /tmp entry to fstab\n");
        fs_mgr_free_fstab(fstab);
        fstab = NULL;
        return;
    }

    printf("recovery filesystem table\n");
    printf("=========================\n");
	//到这一步，打印分区表信息，这类信息在
	//recovery启动的时候的log可以看到
	//分别是以下
	//编号|   挂载节点|  文件系统类型|  块设备|   长度
    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");
}

挂载完相应的分区以后，就需要获取命令参数，因为只有挂载了对应的分区，才能访问到前面要写入command的这个文件，这样我们才能正确的打开文件，如果分区都没找到，那么当然就找不到分区上的文件，上面这个步骤是至关重要的。

//获取参数
	//这个参数也可能是从/cache/recovery/command文件中得到相应的命令
	//也就是可以往command这个文件写入对应的格式的命令即可
    get_args(&argc, &argv);

    const char *send_intent = NULL;
    const char *update_package = NULL;
    int wipe_data = 0, wipe_cache = 0, show_text = 0;
    bool just_exit = false;
    bool shutdown_after = false;

    int arg;
	//参数有擦除分区，OTA更新等
    while ((arg = getopt_long(argc, argv, "", OPTIONS, NULL)) != -1) {
        switch (arg) {
        case 's': send_intent = optarg; break;
        case 'u': update_package = optarg; break;
        case 'w': wipe_data = wipe_cache = 1; break;
        case 'c': wipe_cache = 1; break;
        case 't': show_text = 1; 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 'p': shutdown_after = true; break;
        case 'r': reason = optarg; break;
        case '?':
            LOGE("Invalid command argument\n");
            continue;
        }
    }

获取 到对应的命令，就会执行对应的标志，后面会根据标志来执行对应的操作。

做完以上的流程后，下面就是创建设备，设置语言信息，初始化recovery的UI界面，设置Selinux权限，代码如下：

//设置语言
    if (locale == NULL) {
        load_locale_from_cache();
    }
    printf("locale is [%s]\n", locale);
    printf("stage is [%s]\n", stage);
    printf("reason is [%s]\n", reason);
	//创建设备
    Device* device = make_device();
	//获取UI
    ui = device->GetUI();
	//设置当前的UI
    gCurrentUI = ui;
	//设置UI的语言信息
    ui->SetLocale(locale);
	//UI初始化
    ui->Init();

    int st_cur, st_max;
    if (stage != NULL && sscanf(stage, "%d/%d", &st_cur, &st_max) == 2) {
        ui->SetStage(st_cur, st_max);
    }
	//设置recovery的背景图
    ui->SetBackground(RecoveryUI::NONE);
	//设置界面上是否能够显示字符，使能ui->print函数开关
    if (show_text) ui->ShowText(true);
	//设置selinux权限，一般我会把selinux 给disabled
    struct selinux_opt seopts[] = {
      { SELABEL_OPT_PATH, "/file_contexts" }
    };

    sehandle = selabel_open(SELABEL_CTX_FILE, seopts, 1);

    if (!sehandle) {
        ui->Print("Warning: No file_contexts\n");
    }
	//虚函数，没有做什么流程
    device->StartRecovery();

    printf("Command:");
    for (arg = 0; arg < argc; arg++) {
        printf(" \"%s\"", argv[arg]);
    }
    printf("\n");

接下来 是重要的环节，这个环节将会根据上面命令参数来做真正的事情了，比如恢复出厂设置，OTA更新等。

//如果update_package(也就是要升级的OTA包)不为空的情况下
	//这里要对升级包的路径做一下路径转换，这里可以自由定制自己升级包的路径
    if (update_package) {
        // For backwards compatibility on the cache partition only, if
        // we're given an old 'root' path "CACHE:foo", change it to
        // "/cache/foo".

	//这里就是做转换的方法
	//先比较传进来的recovery参数的前6个byte是否是CACHE
	//如果是将其路径转化为/cache/CACHE: ......
        if (strncmp(update_package, "CACHE:", 6) == 0) {
            int len = strlen(update_package) + 10;
            char* modified_path = (char*)malloc(len);
            strlcpy(modified_path, "/cache/", len);
            strlcat(modified_path, update_package+6, len);
            printf("(replacing path \"%s\" with \"%s\")\n",
                   update_package, modified_path);
			//这个update_package就是转换后的路径
            update_package = modified_path;
        }
    }
    printf("\n");
    property_list(print_property, NULL);
	//获取属性，这里应该是从一个文件中找到ro.build.display.id
	//获取recovery的版本信息
    property_get("ro.build.display.id", recovery_version, "");
    printf("\n");

	//定义一个安装成功的标志位INSTALL_SUCCESS  ----> 其实是个枚举，值为0
    int status = INSTALL_SUCCESS;
	//判断转换后的OTA升级包的路径是否不为空，如果不为空
	//执行install_package 函数进行升级
    if (update_package != NULL) {
        status = install_package(update_package, &wipe_cache, TEMPORARY_INSTALL_FILE, true);
		//判断是否升级成功
        if (status == INSTALL_SUCCESS && wipe_cache) {
			//擦除这个路径，相当于删除了这个路径下的OTA升级包
            if (erase_volume("/cache")) {
                LOGE("Cache wipe (requested by package) failed.");
            }
        }
		//如果安装不成功
        if (status != INSTALL_SUCCESS) {
            ui->Print("Installation aborted.\n");

            // If this is an eng or userdebug build, then automatically
            // turn the text display on if the script fails so the error
            // message is visible.
            char buffer[PROPERTY_VALUE_MAX+1];
            property_get("ro.build.fingerprint", buffer, "");
            if (strstr(buffer, ":userdebug/") || strstr(buffer, ":eng/")) {
                ui->ShowText(true);
            }
        }
    }
	//如果跑的是格式化数据区，那么就走这个流程
	else if (wipe_data) {
        if (device->WipeData()) status = INSTALL_ERROR;
		//格式化/data分区
        if (erase_volume("/data")) status = INSTALL_ERROR;
        if (wipe_cache && erase_volume("/cache")) status = INSTALL_ERROR;
        if (erase_persistent_partition() == -1 ) status = INSTALL_ERROR;
        if (status != INSTALL_SUCCESS) ui->Print("Data wipe failed.\n");
    } 
	//格式化cache分区
	else if (wipe_cache) {
        if (wipe_cache && erase_volume("/cache")) status = INSTALL_ERROR;
        if (status != INSTALL_SUCCESS) ui->Print("Cache wipe failed.\n");
    } 
	else if (!just_exit) {
        status = INSTALL_NONE;  // No command specified
        ui->SetBackground(RecoveryUI::NO_COMMAND);
    }
	//如果安装失败或者。。。
    if (status == INSTALL_ERROR || status == INSTALL_CORRUPT) {
        copy_logs();
		//显示错误的LOGO
        ui->SetBackground(RecoveryUI::ERROR);
    }
    Device::BuiltinAction after = shutdown_after ? Device::SHUTDOWN : Device::REBOOT;
    if (status != INSTALL_SUCCESS || ui->IsTextVisible()) {
        Device::BuiltinAction temp = prompt_and_wait(device, status);
        if (temp != Device::NO_ACTION) after = temp;
    }
	
    // Save logs and clean up before rebooting or shutting down.
    //完成recovery升级
    finish_recovery(send_intent);

    switch (after) {
        case Device::SHUTDOWN:
            ui->Print("Shutting down...\n");
            property_set(ANDROID_RB_PROPERTY, "shutdown,");
            break;

        case Device::REBOOT_BOOTLOADER:
            ui->Print("Rebooting to bootloader...\n");
            property_set(ANDROID_RB_PROPERTY, "reboot,bootloader");
            break;

        default:
            ui->Print("Rebooting...\n");
            property_set(ANDROID_RB_PROPERTY, "reboot,");
            break;
    }
    sleep(5); // should reboot before this finishes
    return EXIT_SUCCESS;

在 这里面，我们最常用的即是OTA更新和恢复出厂设置，先来说说恢复出厂设置，这个功能就是所谓的手机双清，众所周知，Android手机在使用很久后，由于垃圾数据，以及其它的因素会导致手机的反应越来越慢，这让人烦恼不已，所以就需要双清，双清一般就是清除

/data分区和/cache分区，代码流程很详细，有兴趣可以自己去分析。

接下来看看OTA是如何实现更新的，我们看到install_ota_package这个函数，执行到这个函数，看到源码：

//安装更新包
int
install_package(const char* path, int* wipe_cache, const char* install_file,
                bool needs_mount)
{
    FILE* install_log = fopen_path(install_file, "w");
    if (install_log) {
        fputs(path, install_log);
        fputc('\n', install_log);
    } else {
        LOGE("failed to open last_install: %s\n", strerror(errno));
    }
    int result;
	//设置安装挂载对应的节点
	//这一步是关键
    if (setup_install_mounts() != 0) {
        LOGE("failed to set up expected mounts for install; aborting\n");
        result = INSTALL_ERROR;
    } else {
    	//到这里才是真正的去安装OTA包
        result = really_install_package(path, wipe_cache, needs_mount);
    }
	//如果返回结果为0，那么安装就成功了
    if (install_log) {
        fputc(result == INSTALL_SUCCESS ? '1' : '0', install_log);
        fputc('\n', install_log);
        fclose(install_log);
    }
    return result;
}

其实到了really_install_package这一步，才是真正做到OTA更新，但是在OTA更新之前至关重要的一步就是设置安装挂载对应的节点了，我曾经掉入此坑，现在拿出来分析一下，我们来看看setup_install_mounts这个函数:

//设置安装挂载的节点
int setup_install_mounts() {
    if (fstab == NULL) {
        LOGE("can't set up install mounts: no fstab loaded\n");
        return -1;
    }
    for (int i = 0; i < fstab->num_entries; ++i) {
        Volume* v = fstab->recs + i;
	//如果判断挂载的路径是/tmp 或者/cache
	//那么就挂载对应的节点，而其它的节点都不会去挂载
        if (strcmp(v->mount_point, "/tmp") == 0 ||
            strcmp(v->mount_point, "/cache") == 0) {
            if (ensure_path_mounted(v->mount_point) != 0) {
                LOGE("failed to mount %s\n", v->mount_point);
                return -1;
            }

        }
		//如果不是/tmp或者/cache这两个节点，则默认就会卸载所有的挂载节点
		else {
        	//卸载所有的挂载节点
            if (ensure_path_unmounted(v->mount_point) != 0) {
                LOGE("failed to unmount %s\n", v->mount_point);
                return -1;
            }
        }
    }
    return 0;
}

如果在安装更新的时候，OTA包经过路径转换后不是放在/tmp和/cache这个路径下的时候，那么就会走else分支，从而卸载所有的挂载节点，这样就会导致，传的路径正确，却OTA更新不成功，如果是做自己定制的路径，这一步一定要小心，我们可以在这里继续添加定制的挂载点。

那么，执行完设置挂载节点的函数后，接下来就是执行真正的OTA更新了，我们来看看：

static int
really_install_package(const char *path, int* wipe_cache, bool needs_mount)
{
    //设置更新时的背景
    ui->SetBackground(RecoveryUI::INSTALLING_UPDATE);
    ui->Print("Finding update package...\n");
    // Give verification half the progress bar...
    //设置进度条的类型
    ui->SetProgressType(RecoveryUI::DETERMINATE);
    //显示进度条
    ui->ShowProgress(VERIFICATION_PROGRESS_FRACTION, VERIFICATION_PROGRESS_TIME);
    LOGI("Update location: %s\n", path);
    //在屏幕上打印 Opening update package..
    // Map the update package into memory.
    ui->Print("Opening update package...\n");
	//patch是OTA的路径,need_mount参数表示是否需要挂载，1挂载，0，不挂载
    if (path && needs_mount) {
        if (path[0] == '@') {
            ensure_path_mounted(path+1);
        } else {
        	//挂载OTA升级包的路径------> 一般是执行这个流程
            ensure_path_mounted(path);
        }
    }

    MemMapping map;
    if (sysMapFile(path, &map) != 0) {
        LOGE("failed to map file\n");
        return INSTALL_CORRUPT;
    }

    int numKeys;
    //获取校验公钥文件
    Certificate* loadedKeys = load_keys(PUBLIC_KEYS_FILE, &numKeys);
    if (loadedKeys == NULL) {
        LOGE("Failed to load keys\n");
        return INSTALL_CORRUPT;
    }
    LOGI("%d key(s) loaded from %s\n", numKeys, PUBLIC_KEYS_FILE);

    ui->Print("Verifying update package...\n");

    int err;
	//校验文件
    err = verify_file(map.addr, map.length, loadedKeys, numKeys);
    free(loadedKeys);
    LOGI("verify_file returned %d\n", err);
	//如果校验不成功
    if (err != VERIFY_SUCCESS) {
		//打印签名失败
        LOGE("signature verification failed\n");
        sysReleaseMap(&map);
        return INSTALL_CORRUPT;
    }

    /* Try to open the package.
     */
    //尝试去打开ota压缩包
    ZipArchive zip;
    err = mzOpenZipArchive(map.addr, map.length, &zip);
    if (err != 0) {
        LOGE("Can't open %s\n(%s)\n", path, err != -1 ? strerror(err) : "bad");
        sysReleaseMap(&map);
        return INSTALL_CORRUPT;
    }

    /* Verify and install the contents of the package.
     */
    //开始安装升级包
    ui->Print("Installing update...\n");
    ui->SetEnableReboot(false);
    int result = try_update_binary(path, &zip, wipe_cache);
	//安装成功后自动重启
    ui->SetEnableReboot(true);
    ui->Print("\n");

    sysReleaseMap(&map);
	//返回结果
    return result;
}

关于recovery的大致流程，我们分析至此，关于如何像MTK平台一样，定制recovery，这就需要读者能够读懂recovery的流程，然后加入自己的代码进行定制，当然我们也会看到，一些recovery花样百出，很多UI做了自己的，而不是用安卓系统原生态的，安卓系统recovery原生态的UI如下：

如何定制相应的UI，后续我们会对recovery源代码中的UI显示做进一步的分析。。。。

接下来，贴出Android5.0的recovery.cpp代码和注释：

/*
 * Copyright (C) 2007 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.
 */

#include <ctype.h>
#include <dirent.h>
#include <errno.h>
#include <fcntl.h>
#include <getopt.h>
#include <limits.h>
#include <linux/input.h>
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <time.h>
#include <unistd.h>

#include "bootloader.h"
#include "common.h"
#include "cutils/properties.h"
#include "cutils/android_reboot.h"
#include "install.h"
#include "minui/minui.h"
#include "minzip/DirUtil.h"
#include "roots.h"
#include "ui.h"
#include "screen_ui.h"
#include "device.h"
#include "adb_install.h"
extern "C" {
#include "minadbd/adb.h"
#include "fuse_sideload.h"
#include "fuse_sdcard_provider.h"
}

struct selabel_handle *sehandle;

static const struct option OPTIONS[] = {
  { "send_intent", required_argument, NULL, 's' },
  { "update_package", required_argument, NULL, 'u' },
  { "wipe_data", no_argument, NULL, 'w' },
  { "wipe_cache", no_argument, NULL, 'c' },
  { "show_text", no_argument, NULL, 't' },
  { "just_exit", no_argument, NULL, 'x' },
  { "locale", required_argument, NULL, 'l' },
  { "stages", required_argument, NULL, 'g' },
  { "shutdown_after", no_argument, NULL, 'p' },
  { "reason", required_argument, NULL, 'r' },
  { NULL, 0, NULL, 0 },
};

#define LAST_LOG_FILE "/cache/recovery/last_log"

static const char *CACHE_LOG_DIR = "/cache/recovery";
static const char *COMMAND_FILE = "/cache/recovery/command";
static const char *INTENT_FILE = "/cache/recovery/intent";
static const char *LOG_FILE = "/cache/recovery/log";
static const char *LAST_INSTALL_FILE = "/cache/recovery/last_install";
static const char *LOCALE_FILE = "/cache/recovery/last_locale";
static const char *CACHE_ROOT = "/cache";
static const char *SDCARD_ROOT = "/sdcard";
static const char *TEMPORARY_LOG_FILE = "/tmp/recovery.log";
static const char *TEMPORARY_INSTALL_FILE = "/tmp/last_install";

#define KEEP_LOG_COUNT 10

RecoveryUI* ui = NULL;
char* locale = NULL;
char recovery_version[PROPERTY_VALUE_MAX+1];
char* stage = NULL;
char* reason = NULL;

/*
 * The recovery tool communicates with the main system through /cache files.
 *   /cache/recovery/command - INPUT - command line for tool, one arg per line
 *   /cache/recovery/log - OUTPUT - combined log file from recovery run(s)
 *   /cache/recovery/intent - OUTPUT - intent that was passed in
 *
 * The arguments which may be supplied in the recovery.command file:
 *   --send_intent=anystring - write the text out to recovery.intent
 *   --update_package=path - verify install an OTA package file
 *   --wipe_data - erase user data (and cache), then reboot
 *   --wipe_cache - wipe cache (but not user data), then reboot
 *   --set_encrypted_filesystem=on|off - enables / diasables encrypted fs
 *   --just_exit - do nothing; exit and reboot
 *
 * After completing, we remove /cache/recovery/command and reboot.
 * Arguments may also be supplied in the bootloader control block (BCB).
 * These important scenarios must be safely restartable at any point:
 *
 * FACTORY RESET
 * 1. user selects "factory reset"
 * 2. main system writes "--wipe_data" to /cache/recovery/command
 * 3. main system reboots into recovery
 * 4. get_args() writes BCB with "boot-recovery" and "--wipe_data"
 *    -- after this, rebooting will restart the erase --
 * 5. erase_volume() reformats /data
 * 6. erase_volume() reformats /cache
 * 7. finish_recovery() erases BCB
 *    -- after this, rebooting will restart the main system --
 * 8. main() calls reboot() to boot main system
 *
 * OTA INSTALL
 * 1. main system downloads OTA package to /cache/some-filename.zip
 * 2. main system writes "--update_package=/cache/some-filename.zip"
 * 3. main system reboots into recovery
 * 4. get_args() writes BCB with "boot-recovery" and "--update_package=..."
 *    -- after this, rebooting will attempt to reinstall the update --
 * 5. install_package() attempts to install the update
 *    NOTE: the package install must itself be restartable from any point
 * 6. finish_recovery() erases BCB
 *    -- after this, rebooting will (try to) restart the main system --
 * 7. ** if install failed **
 *    7a. prompt_and_wait() shows an error icon and waits for the user
 *    7b; the user reboots (pulling the battery, etc) into the main system
 * 8. main() calls maybe_install_firmware_update()
 *    ** if the update contained radio/hboot firmware **:
 *    8a. m_i_f_u() writes BCB with "boot-recovery" and "--wipe_cache"
 *        -- after this, rebooting will reformat cache & restart main system --
 *    8b. m_i_f_u() writes firmware image into raw cache partition
 *    8c. m_i_f_u() writes BCB with "update-radio/hboot" and "--wipe_cache"
 *        -- after this, rebooting will attempt to reinstall firmware --
 *    8d. bootloader tries to flash firmware
 *    8e. bootloader writes BCB with "boot-recovery" (keeping "--wipe_cache")
 *        -- after this, rebooting will reformat cache & restart main system --
 *    8f. erase_volume() reformats /cache
 *    8g. finish_recovery() erases BCB
 *        -- after this, rebooting will (try to) restart the main system --
 * 9. main() calls reboot() to boot main system
 */

static const int MAX_ARG_LENGTH = 4096;
static const int MAX_ARGS = 100;

// open a given path, mounting partitions as necessary
FILE*
fopen_path(const char *path, const char *mode) {
    if (ensure_path_mounted(path) != 0) {
        LOGE("Can't mount %s\n", path);
        return NULL;
    }

    // When writing, try to create the containing directory, if necessary.
    // Use generous permissions, the system (init.rc) will reset them.
    if (strchr("wa", mode[0])) dirCreateHierarchy(path, 0777, NULL, 1, sehandle);

    FILE *fp = fopen(path, mode);
    return fp;
}

static void redirect_stdio(const char* filename) {
    // If these fail, there's not really anywhere to complain...
    freopen(filename, "a", stdout); setbuf(stdout, NULL);
    freopen(filename, "a", stderr); setbuf(stderr, NULL);
}

// close a file, log an error if the error indicator is set
static void
check_and_fclose(FILE *fp, const char *name) {
    fflush(fp);
    if (ferror(fp)) LOGE("Error in %s\n(%s)\n", name, strerror(errno));
    fclose(fp);
}

// command line args come from, in decreasing precedence:
//   - the actual command line
//   - the bootloader control block (one per line, after "recovery")
//   - the contents of COMMAND_FILE (one per line)
static void
get_args(int *argc, char ***argv) {
    struct bootloader_message boot;
    memset(&boot, 0, sizeof(boot));
    get_bootloader_message(&boot);  // this may fail, leaving a zeroed structure
    stage = strndup(boot.stage, sizeof(boot.stage));

    if (boot.command[0] != 0 && boot.command[0] != 255) {
        LOGI("Boot command: %.*s\n", (int)sizeof(boot.command), boot.command);
    }

    if (boot.status[0] != 0 && boot.status[0] != 255) {
        LOGI("Boot status: %.*s\n", (int)sizeof(boot.status), boot.status);
    }

    // --- if arguments weren't supplied, look in the bootloader control block
    if (*argc <= 1) {
        boot.recovery[sizeof(boot.recovery) - 1] = '\0';  // Ensure termination
        const char *arg = strtok(boot.recovery, "\n");
        if (arg != NULL && !strcmp(arg, "recovery")) {
            *argv = (char **) malloc(sizeof(char *) * MAX_ARGS);
            (*argv)[0] = strdup(arg);
            for (*argc = 1; *argc < MAX_ARGS; ++*argc) {
                if ((arg = strtok(NULL, "\n")) == NULL) break;
                (*argv)[*argc] = strdup(arg);
            }
            LOGI("Got arguments from boot message\n");
        } else if (boot.recovery[0] != 0 && boot.recovery[0] != 255) {
            LOGE("Bad boot message\n\"%.20s\"\n", boot.recovery);
        }
    }

    // --- if that doesn't work, try the command file
    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);
        }
    }

    // --> 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);
}

static void
set_sdcard_update_bootloader_message() {
    struct bootloader_message boot;
    memset(&boot, 0, sizeof(boot));
    strlcpy(boot.command, "boot-recovery", sizeof(boot.command));
    strlcpy(boot.recovery, "recovery\n", sizeof(boot.recovery));
    set_bootloader_message(&boot);
}

// How much of the temp log we have copied to the copy in cache.
static long tmplog_offset = 0;

static void
copy_log_file(const char* source, const char* destination, int append) {
    FILE *log = fopen_path(destination, append ? "a" : "w");
    if (log == NULL) {
        LOGE("Can't open %s\n", destination);
    } else {
        FILE *tmplog = fopen(source, "r");
        if (tmplog != NULL) {
            if (append) {
                fseek(tmplog, tmplog_offset, SEEK_SET);  // Since last write
            }
            char buf[4096];
            while (fgets(buf, sizeof(buf), tmplog)) fputs(buf, log);
            if (append) {
                tmplog_offset = ftell(tmplog);
            }
            check_and_fclose(tmplog, source);
        }
        check_and_fclose(log, destination);
    }
}

// Rename last_log -> last_log.1 -> last_log.2 -> ... -> last_log.$max
// Overwrites any existing last_log.$max.
static void
rotate_last_logs(int max) {
    char oldfn[256];
    char newfn[256];

    int i;
    for (i = max-1; i >= 0; --i) {
        snprintf(oldfn, sizeof(oldfn), (i==0) ? LAST_LOG_FILE : (LAST_LOG_FILE ".%d"), i);
        snprintf(newfn, sizeof(newfn), LAST_LOG_FILE ".%d", i+1);
        // ignore errors
        rename(oldfn, newfn);
    }
}

static void
copy_logs() {
    // Copy logs to cache so the system can find out what happened.
    copy_log_file(TEMPORARY_LOG_FILE, LOG_FILE, true);
    copy_log_file(TEMPORARY_LOG_FILE, LAST_LOG_FILE, false);
    copy_log_file(TEMPORARY_INSTALL_FILE, LAST_INSTALL_FILE, false);
    chmod(LOG_FILE, 0600);
    chown(LOG_FILE, 1000, 1000);   // system user
    chmod(LAST_LOG_FILE, 0640);
    chmod(LAST_INSTALL_FILE, 0644);
    sync();
}

// clear the recovery command and prepare to boot a (hopefully working) system,
// copy our log file to cache as well (for the system to read), and
// record any intent we were asked to communicate back to the system.
// this function is idempotent: call it as many times as you like.
static void
finish_recovery(const char *send_intent) {
    // By this point, we're ready to return to the main system...
    if (send_intent != NULL) {
        FILE *fp = fopen_path(INTENT_FILE, "w");
        if (fp == NULL) {
            LOGE("Can't open %s\n", INTENT_FILE);
        } else {
            fputs(send_intent, fp);
            check_and_fclose(fp, INTENT_FILE);
        }
    }

    // Save the locale to cache, so if recovery is next started up
    // without a --locale argument (eg, directly from the bootloader)
    // it will use the last-known locale.
    if (locale != NULL) {
        LOGI("Saving locale \"%s\"\n", locale);
        FILE* fp = fopen_path(LOCALE_FILE, "w");
        fwrite(locale, 1, strlen(locale), fp);
        fflush(fp);
        fsync(fileno(fp));
        check_and_fclose(fp, LOCALE_FILE);
    }

    copy_logs();

    // Reset to normal system boot so recovery won't cycle indefinitely.
    struct bootloader_message boot;
    memset(&boot, 0, sizeof(boot));
    set_bootloader_message(&boot);

    // Remove the command file, so recovery won't repeat indefinitely.
    if (ensure_path_mounted(COMMAND_FILE) != 0 ||
        (unlink(COMMAND_FILE) && errno != ENOENT)) {
        LOGW("Can't unlink %s\n", COMMAND_FILE);
    }

    ensure_path_unmounted(CACHE_ROOT);
    sync();  // For good measure.
}

typedef struct _saved_log_file {
    char* name;
    struct stat st;
    unsigned char* data;
    struct _saved_log_file* next;
} saved_log_file;

static int
erase_volume(const char *volume) {
    bool is_cache = (strcmp(volume, CACHE_ROOT) == 0);

    ui->SetBackground(RecoveryUI::ERASING);
    ui->SetProgressType(RecoveryUI::INDETERMINATE);

    saved_log_file* head = NULL;

    if (is_cache) {
        // If we're reformatting /cache, we load any
        // "/cache/recovery/last*" files into memory, so we can restore
        // them after the reformat.

        ensure_path_mounted(volume);

        DIR* d;
        struct dirent* de;
        d = opendir(CACHE_LOG_DIR);
        if (d) {
            char path[PATH_MAX];
            strcpy(path, CACHE_LOG_DIR);
            strcat(path, "/");
            int path_len = strlen(path);
            while ((de = readdir(d)) != NULL) {
                if (strncmp(de->d_name, "last", 4) == 0) {
                    saved_log_file* p = (saved_log_file*) malloc(sizeof(saved_log_file));
                    strcpy(path+path_len, de->d_name);
                    p->name = strdup(path);
                    if (stat(path, &(p->st)) == 0) {
                        // truncate files to 512kb
                        if (p->st.st_size > (1 << 19)) {
                            p->st.st_size = 1 << 19;
                        }
                        p->data = (unsigned char*) malloc(p->st.st_size);
                        FILE* f = fopen(path, "rb");
                        fread(p->data, 1, p->st.st_size, f);
                        fclose(f);
                        p->next = head;
                        head = p;
                    } else {
                        free(p);
                    }
                }
            }
            closedir(d);
        } else {
            if (errno != ENOENT) {
                printf("opendir failed: %s\n", strerror(errno));
            }
        }
    }

    ui->Print("Formatting %s...\n", volume);

    ensure_path_unmounted(volume);
    int result = format_volume(volume);

    if (is_cache) {
        while (head) {
            FILE* f = fopen_path(head->name, "wb");
            if (f) {
                fwrite(head->data, 1, head->st.st_size, f);
                fclose(f);
                chmod(head->name, head->st.st_mode);
                chown(head->name, head->st.st_uid, head->st.st_gid);
            }
            free(head->name);
            free(head->data);
            saved_log_file* temp = head->next;
            free(head);
            head = temp;
        }

        // Any part of the log we'd copied to cache is now gone.
        // Reset the pointer so we copy from the beginning of the temp
        // log.
        tmplog_offset = 0;
        copy_logs();
    }

    return result;
}

static const char**
prepend_title(const char* const* headers) {
    // count the number of lines in our title, plus the
    // caller-provided headers.
    int count = 3;   // our title has 3 lines
    const char* const* p;
    for (p = headers; *p; ++p, ++count);

    const char** new_headers = (const char**)malloc((count+1) * sizeof(char*));
    const char** h = new_headers;
    *(h++) = "Android system recovery <" EXPAND(RECOVERY_API_VERSION) "e>";
    *(h++) = recovery_version;
    *(h++) = "";
    for (p = headers; *p; ++p, ++h) *h = *p;
    *h = NULL;

    return new_headers;
}

static int
get_menu_selection(const char* const * headers, const char* const * items,
                   int menu_only, int initial_selection, Device* device) {
    // throw away keys pressed previously, so user doesn't
    // accidentally trigger menu items.
    ui->FlushKeys();

    ui->StartMenu(headers, items, initial_selection);
    int selected = initial_selection;
    int chosen_item = -1;

    while (chosen_item < 0) {
        int key = ui->WaitKey();
        int visible = ui->IsTextVisible();

        if (key == -1) {   // ui_wait_key() timed out
            if (ui->WasTextEverVisible()) {
                continue;
            } else {
                LOGI("timed out waiting for key input; rebooting.\n");
                ui->EndMenu();
                return 0; // XXX fixme
            }
        }

        int action = device->HandleMenuKey(key, visible);

        if (action < 0) {
            switch (action) {
                case Device::kHighlightUp:
                    --selected;
                    selected = ui->SelectMenu(selected);
                    break;
                case Device::kHighlightDown:
                    ++selected;
                    selected = ui->SelectMenu(selected);
                    break;
                case Device::kInvokeItem:
                    chosen_item = selected;
                    break;
                case Device::kNoAction:
                    break;
            }
        } else if (!menu_only) {
            chosen_item = action;
        }
    }

    ui->EndMenu();
    return chosen_item;
}

static int compare_string(const void* a, const void* b) {
    return strcmp(*(const char**)a, *(const char**)b);
}

// Returns a malloc'd path, or NULL.
static char*
browse_directory(const char* path, Device* device) {
    ensure_path_mounted(path);

    const char* MENU_HEADERS[] = { "Choose a package to install:",
                                   path,
                                   "",
                                   NULL };
    DIR* d;
    struct dirent* de;
    d = opendir(path);
    if (d == NULL) {
        LOGE("error opening %s: %s\n", path, strerror(errno));
        return NULL;
    }

    const char** headers = prepend_title(MENU_HEADERS);

    int d_size = 0;
    int d_alloc = 10;
    char** dirs = (char**)malloc(d_alloc * sizeof(char*));
    int z_size = 1;
    int z_alloc = 10;
    char** zips = (char**)malloc(z_alloc * sizeof(char*));
    zips[0] = strdup("../");

    while ((de = readdir(d)) != NULL) {
        int name_len = strlen(de->d_name);

        if (de->d_type == DT_DIR) {
            // skip "." and ".." entries
            if (name_len == 1 && de->d_name[0] == '.') continue;
            if (name_len == 2 && de->d_name[0] == '.' &&
                de->d_name[1] == '.') continue;

            if (d_size >= d_alloc) {
                d_alloc *= 2;
                dirs = (char**)realloc(dirs, d_alloc * sizeof(char*));
            }
            dirs[d_size] = (char*)malloc(name_len + 2);
            strcpy(dirs[d_size], de->d_name);
            dirs[d_size][name_len] = '/';
            dirs[d_size][name_len+1] = '\0';
            ++d_size;
        } else if (de->d_type == DT_REG &&
                   name_len >= 4 &&
                   strncasecmp(de->d_name + (name_len-4), ".zip", 4) == 0) {
            if (z_size >= z_alloc) {
                z_alloc *= 2;
                zips = (char**)realloc(zips, z_alloc * sizeof(char*));
            }
            zips[z_size++] = strdup(de->d_name);
        }
    }
    closedir(d);

    qsort(dirs, d_size, sizeof(char*), compare_string);
    qsort(zips, z_size, sizeof(char*), compare_string);

    // append dirs to the zips list
    if (d_size + z_size + 1 > z_alloc) {
        z_alloc = d_size + z_size + 1;
        zips = (char**)realloc(zips, z_alloc * sizeof(char*));
    }
    memcpy(zips + z_size, dirs, d_size * sizeof(char*));
    free(dirs);
    z_size += d_size;
    zips[z_size] = NULL;

    char* result;
    int chosen_item = 0;
    while (true) {
        chosen_item = get_menu_selection(headers, zips, 1, chosen_item, device);

        char* item = zips[chosen_item];
        int item_len = strlen(item);
        if (chosen_item == 0) {          // item 0 is always "../"
            // go up but continue browsing (if the caller is update_directory)
            result = NULL;
            break;
        }

        char new_path[PATH_MAX];
        strlcpy(new_path, path, PATH_MAX);
        strlcat(new_path, "/", PATH_MAX);
        strlcat(new_path, item, PATH_MAX);

        if (item[item_len-1] == '/') {
            // recurse down into a subdirectory
            new_path[strlen(new_path)-1] = '\0';  // truncate the trailing '/'
            result = browse_directory(new_path, device);
            if (result) break;
        } else {
            // selected a zip file: return the malloc'd path to the caller.
            result = strdup(new_path);
            break;
        }
    }

    int i;
    for (i = 0; i < z_size; ++i) free(zips[i]);
    free(zips);
    free(headers);

    return result;
}

static void
wipe_data(int confirm, Device* device) {
    if (confirm) {
        static const char** title_headers = NULL;

        if (title_headers == NULL) {
            const char* headers[] = { "Confirm wipe of all user data?",
                                      "  THIS CAN NOT BE UNDONE.",
                                      "",
                                      NULL };
            title_headers = prepend_title((const char**)headers);
        }

        const char* items[] = { " No",
                                " No",
                                " No",
                                " No",
                                " No",
                                " No",
                                " No",
                                " Yes -- delete all user data",   // [7]
                                " No",
                                " No",
                                " No",
                                NULL };

        int chosen_item = get_menu_selection(title_headers, items, 1, 0, device);
        if (chosen_item != 7) {
            return;
        }
    }

    ui->Print("\n-- Wiping data...\n");
    device->WipeData();
    erase_volume("/data");
    erase_volume("/cache");
    erase_persistent_partition();
    ui->Print("Data wipe complete.\n");
}

static void file_to_ui(const char* fn) {
    FILE *fp = fopen_path(fn, "re");
    if (fp == NULL) {
        ui->Print("  Unable to open %s: %s\n", fn, strerror(errno));
        return;
    }
    char line[1024];
    int ct = 0;
    redirect_stdio("/dev/null");
    while(fgets(line, sizeof(line), fp) != NULL) {
        ui->Print("%s", line);
        ct++;
        if (ct % 30 == 0) {
            // give the user time to glance at the entries
            ui->WaitKey();
        }
    }
    redirect_stdio(TEMPORARY_LOG_FILE);
    fclose(fp);
}

static void choose_recovery_file(Device* device) {
    int i;
    static const char** title_headers = NULL;
    char *filename;
    const char* headers[] = { "Select file to view",
                              "",
                              NULL };
    char* entries[KEEP_LOG_COUNT + 2];
    memset(entries, 0, sizeof(entries));

    for (i = 0; i < KEEP_LOG_COUNT; i++) {
        char *filename;
        if (asprintf(&filename, (i==0) ? LAST_LOG_FILE : (LAST_LOG_FILE ".%d"), i) == -1) {
            // memory allocation failure - return early. Should never happen.
            return;
        }
        if ((ensure_path_mounted(filename) != 0) || (access(filename, R_OK) == -1)) {
            free(filename);
            entries[i+1] = NULL;
            break;
        }
        entries[i+1] = filename;
    }

    entries[0] = strdup("Go back");
    title_headers = prepend_title((const char**)headers);

    while(1) {
        int chosen_item = get_menu_selection(title_headers, entries, 1, 0, device);
        if (chosen_item == 0) break;
        file_to_ui(entries[chosen_item]);
    }

    for (i = 0; i < KEEP_LOG_COUNT + 1; i++) {
        free(entries[i]);
    }
}

// Return REBOOT, SHUTDOWN, or REBOOT_BOOTLOADER.  Returning NO_ACTION
// means to take the default, which is to reboot or shutdown depending
// on if the --shutdown_after flag was passed to recovery.
static Device::BuiltinAction
prompt_and_wait(Device* device, int status) {
    const char* const* headers = prepend_title(device->GetMenuHeaders());

    for (;;) {
        finish_recovery(NULL);
        switch (status) {
            case INSTALL_SUCCESS:
            case INSTALL_NONE:
                ui->SetBackground(RecoveryUI::NO_COMMAND);
                break;

            case INSTALL_ERROR:
            case INSTALL_CORRUPT:
                ui->SetBackground(RecoveryUI::ERROR);
                break;
        }
        ui->SetProgressType(RecoveryUI::EMPTY);

        int chosen_item = get_menu_selection(headers, device->GetMenuItems(), 0, 0, device);

        // device-specific code may take some action here.  It may
        // return one of the core actions handled in the switch
        // statement below.
        Device::BuiltinAction chosen_action = device->InvokeMenuItem(chosen_item);

        int wipe_cache = 0;
        switch (chosen_action) {
            case Device::NO_ACTION:
                break;

            case Device::REBOOT:
            case Device::SHUTDOWN:
            case Device::REBOOT_BOOTLOADER:
                return chosen_action;

            case Device::WIPE_DATA:
                wipe_data(ui->IsTextVisible(), device);
                if (!ui->IsTextVisible()) return Device::NO_ACTION;
                break;

            case Device::WIPE_CACHE:
                ui->Print("\n-- Wiping cache...\n");
                erase_volume("/cache");
                ui->Print("Cache wipe complete.\n");
                if (!ui->IsTextVisible()) return Device::NO_ACTION;
                break;

            case Device::APPLY_EXT: {
                ensure_path_mounted(SDCARD_ROOT);
                char* path = browse_directory(SDCARD_ROOT, device);
                if (path == NULL) {
                    ui->Print("\n-- No package file selected.\n", path);
                    break;
                }

                ui->Print("\n-- Install %s ...\n", path);
                set_sdcard_update_bootloader_message();
                void* token = start_sdcard_fuse(path);

                int status = install_package(FUSE_SIDELOAD_HOST_PATHNAME, &wipe_cache,
                                             TEMPORARY_INSTALL_FILE, false);

                finish_sdcard_fuse(token);
                ensure_path_unmounted(SDCARD_ROOT);

                if (status == INSTALL_SUCCESS && wipe_cache) {
                    ui->Print("\n-- Wiping cache (at package request)...\n");
                    if (erase_volume("/cache")) {
                        ui->Print("Cache wipe failed.\n");
                    } else {
                        ui->Print("Cache wipe complete.\n");
                    }
                }

                if (status >= 0) {
                    if (status != INSTALL_SUCCESS) {
                        ui->SetBackground(RecoveryUI::ERROR);
                        ui->Print("Installation aborted.\n");
                    } else if (!ui->IsTextVisible()) {
                        return Device::NO_ACTION;  // reboot if logs aren't visible
                    } else {
                        ui->Print("\nInstall from sdcard complete.\n");
                    }
                }
                break;
            }

            case Device::APPLY_CACHE:
                ui->Print("\nAPPLY_CACHE is deprecated.\n");
                break;

            case Device::READ_RECOVERY_LASTLOG:
                choose_recovery_file(device);
                break;

            case Device::APPLY_ADB_SIDELOAD:
                status = apply_from_adb(ui, &wipe_cache, TEMPORARY_INSTALL_FILE);
                if (status >= 0) {
                    if (status != INSTALL_SUCCESS) {
                        ui->SetBackground(RecoveryUI::ERROR);
                        ui->Print("Installation aborted.\n");
                        copy_logs();
                    } else if (!ui->IsTextVisible()) {
                        return Device::NO_ACTION;  // reboot if logs aren't visible
                    } else {
                        ui->Print("\nInstall from ADB complete.\n");
                    }
                }
                break;
        }
    }
}

static void
print_property(const char *key, const char *name, void *cookie) {
    printf("%s=%s\n", key, name);
}

static void
load_locale_from_cache() {
    FILE* fp = fopen_path(LOCALE_FILE, "r");
    char buffer[80];
    if (fp != NULL) {
        fgets(buffer, sizeof(buffer), fp);
        int j = 0;
        unsigned int i;
        for (i = 0; i < sizeof(buffer) && buffer[i]; ++i) {
            if (!isspace(buffer[i])) {
                buffer[j++] = buffer[i];
            }
        }
        buffer[j] = 0;
        locale = strdup(buffer);
        check_and_fclose(fp, LOCALE_FILE);
    }
}

static RecoveryUI* gCurrentUI = NULL;

void
ui_print(const char* format, ...) {
    char buffer[256];

    va_list ap;
    va_start(ap, format);
    vsnprintf(buffer, sizeof(buffer), format, ap);
    va_end(ap);

    if (gCurrentUI != NULL) {
        gCurrentUI->Print("%s", buffer);
    } else {
        fputs(buffer, stdout);
    }
}

int
main(int argc, char **argv) {
    time_t start = time(NULL);

	//重定向标准输出和标准出错到/tmp/recovery.log 这个文件里
	//static const char *TEMPORARY_LOG_FILE = "/tmp/recovery.log";
    redirect_stdio(TEMPORARY_LOG_FILE);

    // If this binary is started with the single argument "--adbd",
    // instead of being the normal recovery binary, it turns into kind
    // of a stripped-down version of adbd that only supports the
    // 'sideload' command.  Note this must be a real argument, not
    // anything in the command file or bootloader control block; the
    // only way recovery should be run with this argument is when it
    // starts a copy of itself from the apply_from_adb() function.
    if (argc == 2 && strcmp(argv[1], "--adbd") == 0) {
        adb_main();
        return 0;
    }

    printf("Starting recovery (pid %d) on %s", getpid(), ctime(&start));
	//装载recovery的分区表recovery.fstab
    load_volume_table();
	//在recovery中挂载/cache/recovery/last_log这个文件
	//#define LAST_LOG_FILE "/cache/recovery/last_log"
    ensure_path_mounted(LAST_LOG_FILE);
    rotate_last_logs(KEEP_LOG_COUNT);
	//获取参数
	//这个参数也可能是从/cache/recovery/command文件中得到相应的命令
	//也就是可以往command这个文件写入对应的格式的命令即可
    get_args(&argc, &argv);

    const char *send_intent = NULL;
    const char *update_package = NULL;
    int wipe_data = 0, wipe_cache = 0, show_text = 0;
    bool just_exit = false;
    bool shutdown_after = false;

    int arg;
	//参数有擦除分区，OTA更新等
    while ((arg = getopt_long(argc, argv, "", OPTIONS, NULL)) != -1) {
        switch (arg) {
        case 's': send_intent = optarg; break;
        case 'u': update_package = optarg; break;
        case 'w': wipe_data = wipe_cache = 1; break;
        case 'c': wipe_cache = 1; break;
        case 't': show_text = 1; 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 'p': shutdown_after = true; break;
        case 'r': reason = optarg; break;
        case '?':
            LOGE("Invalid command argument\n");
            continue;
        }
    }
	//设置语言
    if (locale == NULL) {
        load_locale_from_cache();
    }
    printf("locale is [%s]\n", locale);
    printf("stage is [%s]\n", stage);
    printf("reason is [%s]\n", reason);
	//创建设备
    Device* device = make_device();
	//获取UI
    ui = device->GetUI();
	//设置当前的UI
    gCurrentUI = ui;
	//设置UI的语言信息
    ui->SetLocale(locale);
	//UI初始化
    ui->Init();

    int st_cur, st_max;
    if (stage != NULL && sscanf(stage, "%d/%d", &st_cur, &st_max) == 2) {
        ui->SetStage(st_cur, st_max);
    }
	//设置recovery的背景图
    ui->SetBackground(RecoveryUI::NONE);
	//设置界面上是否能够显示字符，使能ui->print函数开关
    if (show_text) ui->ShowText(true);
	//设置selinux权限，一般我会把selinux 给disabled
    struct selinux_opt seopts[] = {
      { SELABEL_OPT_PATH, "/file_contexts" }
    };

    sehandle = selabel_open(SELABEL_CTX_FILE, seopts, 1);

    if (!sehandle) {
        ui->Print("Warning: No file_contexts\n");
    }
	//虚函数，没有做什么流程
    device->StartRecovery();

    printf("Command:");
    for (arg = 0; arg < argc; arg++) {
        printf(" \"%s\"", argv[arg]);
    }
    printf("\n");
	//如果update_package(也就是要升级的OTA包)不为空的情况下
	//这里要对升级包的路径做一下路径转换，这里可以自由定制自己升级包的路径
    if (update_package) {
        // For backwards compatibility on the cache partition only, if
        // we're given an old 'root' path "CACHE:foo", change it to
        // "/cache/foo".

		//这里就是做转换的方法
		//先比较传进来的recovery参数的前6个byte是否是CACHE
		//如果是将其路径转化为/cache/CACHE: ......
        if (strncmp(update_package, "CACHE:", 6) == 0) {
            int len = strlen(update_package) + 10;
            char* modified_path = (char*)malloc(len);
            strlcpy(modified_path, "/cache/", len);
            strlcat(modified_path, update_package+6, len);
            printf("(replacing path \"%s\" with \"%s\")\n",
                   update_package, modified_path);
			//这个update_package就是转换后的路径
            update_package = modified_path;
        }
    }
    printf("\n");
    property_list(print_property, NULL);
	//获取属性，这里应该是从一个文件中找到ro.build.display.id
	//获取recovery的版本信息
    property_get("ro.build.display.id", recovery_version, "");
    printf("\n");

	//定义一个安装成功的标志位INSTALL_SUCCESS  ----> 其实是个枚举，值为0
    int status = INSTALL_SUCCESS;
	//判断转换后的OTA升级包的路径是否不为空，如果不为空
	//执行install_package 函数进行升级
    if (update_package != NULL) {
        status = install_package(update_package, &wipe_cache, TEMPORARY_INSTALL_FILE, true);
		//判断是否升级成功
        if (status == INSTALL_SUCCESS && wipe_cache) {
			//擦除这个路径，相当于删除了这个路径下的OTA升级包
            if (erase_volume("/cache")) {
                LOGE("Cache wipe (requested by package) failed.");
            }
        }
		//如果安装不成功
        if (status != INSTALL_SUCCESS) {
            ui->Print("Installation aborted.\n");

            // If this is an eng or userdebug build, then automatically
            // turn the text display on if the script fails so the error
            // message is visible.
            char buffer[PROPERTY_VALUE_MAX+1];
            property_get("ro.build.fingerprint", buffer, "");
            if (strstr(buffer, ":userdebug/") || strstr(buffer, ":eng/")) {
                ui->ShowText(true);
            }
        }
    }
	//如果跑的是格式化数据区，那么就走这个流程
	else if (wipe_data) {
        if (device->WipeData()) status = INSTALL_ERROR;
		//格式化/data分区
        if (erase_volume("/data")) status = INSTALL_ERROR;
        if (wipe_cache && erase_volume("/cache")) status = INSTALL_ERROR;
        if (erase_persistent_partition() == -1 ) status = INSTALL_ERROR;
        if (status != INSTALL_SUCCESS) ui->Print("Data wipe failed.\n");
    } 
	//格式化cache分区
	else if (wipe_cache) {
        if (wipe_cache && erase_volume("/cache")) status = INSTALL_ERROR;
        if (status != INSTALL_SUCCESS) ui->Print("Cache wipe failed.\n");
    } 
	else if (!just_exit) {
        status = INSTALL_NONE;  // No command specified
        ui->SetBackground(RecoveryUI::NO_COMMAND);
    }
	//如果安装失败或者。。。
    if (status == INSTALL_ERROR || status == INSTALL_CORRUPT) {
        copy_logs();
		//显示错误的LOGO
        ui->SetBackground(RecoveryUI::ERROR);
    }
    Device::BuiltinAction after = shutdown_after ? Device::SHUTDOWN : Device::REBOOT;
    if (status != INSTALL_SUCCESS || ui->IsTextVisible()) {
        Device::BuiltinAction temp = prompt_and_wait(device, status);
        if (temp != Device::NO_ACTION) after = temp;
    }
	
    // Save logs and clean up before rebooting or shutting down.
    //完成recovery升级
    finish_recovery(send_intent);

    switch (after) {
        case Device::SHUTDOWN:
            ui->Print("Shutting down...\n");
            property_set(ANDROID_RB_PROPERTY, "shutdown,");
            break;

        case Device::REBOOT_BOOTLOADER:
            ui->Print("Rebooting to bootloader...\n");
            property_set(ANDROID_RB_PROPERTY, "reboot,bootloader");
            break;

        default:
            ui->Print("Rebooting...\n");
            property_set(ANDROID_RB_PROPERTY, "reboot,");
            break;
    }
    sleep(5); // should reboot before this finishes
    return EXIT_SUCCESS;
}