http://blog.csdn.net/mu0206mu/article/details/7465514
http://blog.csdn.net/huangyabin001/article/category/2703721
Android系统Recovery工作原理之使用update.zip升级过程分析(七)---Recovery服务的核心install_package函数
一、 Recovery服务的核心install_package(升级update.zip特有)
和Recovery服务中的wipe_data、wipe_cache不同,install_package()是升级update.zip特有的一部分,也是最核心的部分。在这一步才真正开始对我们的update.zip包进行处理。下面就开始分析这一部分。还是先看图例:
这一部分的源码文件位于:/gingerbread0919/bootable/recovery/install.c。这是一个没有main函数的源码文件,还是把源码先贴出来如下:
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#include
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#include
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#include
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#include
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#include
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#include
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#include
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#include "common.h"
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#include "install.h"
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#include "mincrypt/rsa.h"
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#include "minui/minui.h"
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#include "minzip/SysUtil.h"
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#include "minzip/Zip.h"
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#include "mtdutils/mounts.h"
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#include "mtdutils/mtdutils.h"
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#include "roots.h"
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#include "verifier.h"
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#define ASSUMED_UPDATE_BINARY_NAME "META-INF/com/google/android/update-binary"
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#define PUBLIC_KEYS_FILE "/res/keys"
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static int
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try_update_binary(const char *path, ZipArchive *zip) {
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const ZipEntry* binary_entry =
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mzFindZipEntry(zip, ASSUMED_UPDATE_BINARY_NAME);
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if (binary_entry == NULL) {
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mzCloseZipArchive(zip);
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return INSTALL_CORRUPT;
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}
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char* binary = "/tmp/update_binary";
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unlink(binary);
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int fd = creat(binary, 0755);
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if (fd < 0) {
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mzCloseZipArchive(zip);
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LOGE("Can't make %s\n", binary);
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return 1;
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}
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bool ok = mzExtractZipEntryToFile(zip, binary_entry, fd);
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close(fd);
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mzCloseZipArchive(zip);
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if (!ok) {
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LOGE("Can't copy %s\n", ASSUMED_UPDATE_BINARY_NAME);
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return 1;
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}
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int pipefd[2];
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pipe(pipefd);
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char** args = malloc(sizeof(char*) * 5);
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args[0] = binary;
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args[1] = EXPAND(RECOVERY_API_VERSION);
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args[2] = malloc(10);
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sprintf(args[2], "%d", pipefd[1]);
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args[3] = (char*)path;
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args[4] = NULL;
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pid_t pid = fork();
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if (pid == 0) {
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close(pipefd[0]);
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execv(binary, args);
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fprintf(stdout, "E:Can't run %s (%s)\n", binary, strerror(errno));
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_exit(-1);
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}
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close(pipefd[1]);
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char buffer[1024];
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FILE* from_child = fdopen(pipefd[0], "r");
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while (fgets(buffer, sizeof(buffer), from_child) != NULL) {
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char* command = strtok(buffer, " \n");
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if (command == NULL) {
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continue;
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} else if (strcmp(command, "progress") == 0) {
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char* fraction_s = strtok(NULL, " \n");
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char* seconds_s = strtok(NULL, " \n");
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float fraction = strtof(fraction_s, NULL);
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int seconds = strtol(seconds_s, NULL, 10);
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ui_show_progress(fraction * (1-VERIFICATION_PROGRESS_FRACTION),
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seconds);
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} else if (strcmp(command, "set_progress") == 0) {
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char* fraction_s = strtok(NULL, " \n");
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float fraction = strtof(fraction_s, NULL);
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ui_set_progress(fraction);
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} else if (strcmp(command, "ui_print") == 0) {
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char* str = strtok(NULL, "\n");
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if (str) {
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ui_print("%s", str);
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} else {
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ui_print("\n");
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}
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} else {
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LOGE("unknown command [%s]\n", command);
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}
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}
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fclose(from_child);
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int status;
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waitpid(pid, &status, 0);
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if (!WIFEXITED(status) || WEXITSTATUS(status) != 0) {
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LOGE("Error in %s\n(Status %d)\n", path, WEXITSTATUS(status));
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return INSTALL_ERROR;
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}
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return INSTALL_SUCCESS;
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}
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static RSAPublicKey*
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load_keys(const char* filename, int* numKeys) {
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RSAPublicKey* out = NULL;
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*numKeys = 0;
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FILE* f = fopen(filename, "r");
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if (f == NULL) {
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LOGE("opening %s: %s\n", filename, strerror(errno));
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goto exit;
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}
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int i;
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bool done = false;
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while (!done) {
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++*numKeys;
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out = realloc(out, *numKeys * sizeof(RSAPublicKey));
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RSAPublicKey* key = out + (*numKeys - 1);
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if (fscanf(f, " { %i , 0x%x , { %u",
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&(key->len), &(key->n0inv), &(key->n[0])) != 3) {
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goto exit;
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}
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if (key->len != RSANUMWORDS) {
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LOGE("key length (%d) does not match expected size\n", key->len);
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goto exit;
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}
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for (i = 1; i < key->len; ++i) {
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if (fscanf(f, " , %u", &(key->n[i])) != 1) goto exit;
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}
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if (fscanf(f, " } , { %u", &(key->rr[0])) != 1) goto exit;
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for (i = 1; i < key->len; ++i) {
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if (fscanf(f, " , %u", &(key->rr[i])) != 1) goto exit;
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}
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fscanf(f, " } } ");
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switch (fgetc(f)) {
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case ',':
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break;
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case EOF:
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done = true;
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break;
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default:
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LOGE("unexpected character between keys\n");
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goto exit;
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}
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}
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fclose(f);
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return out;
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exit:
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if (f) fclose(f);
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free(out);
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*numKeys = 0;
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return NULL;
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}
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int
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install_package(const char *path)
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{
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ui_set_background(BACKGROUND_ICON_INSTALLING);
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ui_print("Finding update package...\n");
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ui_show_indeterminate_progress();
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LOGI("Update location: %s\n", path);
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if (ensure_path_mounted(path) != 0) {
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LOGE("Can't mount %s\n", path);
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return INSTALL_CORRUPT;
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}
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ui_print("Opening update package...\n");
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int numKeys;
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RSAPublicKey* loadedKeys = load_keys(PUBLIC_KEYS_FILE, &numKeys);
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if (loadedKeys == NULL) {
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LOGE("Failed to load keys\n");
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return INSTALL_CORRUPT;
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}
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LOGI("%d key(s) loaded from %s\n", numKeys, PUBLIC_KEYS_FILE);
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ui_print("Verifying update package...\n");
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ui_show_progress(
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VERIFICATION_PROGRESS_FRACTION,
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VERIFICATION_PROGRESS_TIME);
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int err;
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err = verify_file(path, loadedKeys, numKeys);
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free(loadedKeys);
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LOGI("verify_file returned %d\n", err);
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if (err != VERIFY_SUCCESS) {
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LOGE("signature verification failed\n");
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return INSTALL_CORRUPT;
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}
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ZipArchive zip;
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err = mzOpenZipArchive(path, &zip);
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if (err != 0) {
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LOGE("Can't open %s\n(%s)\n", path, err != -1 ? strerror(err) : "bad");
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return INSTALL_CORRUPT;
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}
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ui_print("Installing update...\n");
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return try_update_binary(path, &zip);
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}
下面顺着上面的流程图和源码来分析这一流程:
①ensure_path_mount():先判断所传的update.zip包路径所在的分区是否已经挂载。如果没有则先挂载。
②load_keys():加载公钥源文件,路径位于/res/keys。这个文件在Recovery镜像的根文件系统中。
③verify_file():对升级包update.zip包进行签名验证。
④mzOpenZipArchive():打开升级包,并将相关的信息拷贝到一个临时的ZipArchinve变量中。这一步并未对我们的update.zip包解压。
⑤try_update_binary():在这个函数中才是对我们的update.zip升级的地方。这个函数一开始先根据我们上一步获得的zip包信息,以及升级包的绝对路径将update_binary文件拷贝到内存文件系统的/tmp/update_binary中。以便后面使用。
⑥pipe():创建管道,用于下面的子进程和父进程之间的通信。
⑦fork():创建子进程。其中的子进程主要负责执行binary(execv(binary,args),即执行我们的安装命令脚本),父进程负责接受子进程发送的命令去更新ui显示(显示当前的进度)。子父进程间通信依靠管道。
⑧其中,在创建子进程后,父进程有两个作用。一是通过管道接受子进程发送的命令来更新UI显示。二是等待子进程退出并返回INSTALL SUCCESS。其中子进程在解析执行安装脚本的同时所发送的命令有以下几种:
progress :根据第二个参数secs(秒)来设置进度条。
set_progress :直接设置进度条,frac取值在0.0到0.1之间。
firmware <”hboot”|”radio”>:升级firmware时使用,在API V3中不再使用。
ui_print :在屏幕上显示字符串,即打印更新过程。
execv(binary,args)的作用就是去执行binary程序,这个程序的实质就是去解析update.zip包中的updater-script脚本中的命令并执行。由此,Recovery服务就进入了实际安装update.zip包的过程。
下一篇继续分析使用update-binary解析并执行updater-script的过程。
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