Android系統Recovery工作原理之使用update.zip升級過程分析(七)---Recovery服務的核心install_package函數
轉自:http://blog.csdn.net/mu0206mu/article/details/7465514
一、 Recovery服務的核心install_package(升級update.zip特有)
和Recovery服務中的wipe_data、wipe_cache不同,install_package()是升級update.zip特有的一部分,也是最核心的部分。在這一步才真正開始對我們的update.zip包進行處理。下面就開始分析這一部分。還是先看圖例:
這一部分的源碼文件位於:/gingerbread0919/bootable/recovery/install.c。這是一個沒有main函數的源碼文件,還是把源碼先貼出來如下:
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#include <ctype.h>
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#include <errno.h>
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#include <fcntl.h>
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#include <limits.h>
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#include <sys/stat.h>
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#include <sys/wait.h>
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#include <unistd.h>
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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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}
下面順着上面的流程圖和源碼來分析這一流程:
①ensure_path_mount():先判斷所傳的update.zip包路徑所在的分區是否已經掛載。如果沒有則先掛載。
②load_keys():加載公鑰源文件,路徑位於/res/keys。這個文件在Recovery鏡像的根文件系統中。
③verify_file():對升級包update.zip包進行簽名驗證。
④mzOpenZipArchive():打開升級包,並將相關的信息拷貝到一個臨時的ZipArchinve變量中。這一步並未對我們的update.zip包解壓。
⑤try_update_binary():在這個函數中才是對我們的update.zip升級的地方。這個函數一開始先根據我們上一步獲得的zip包信息,以及升級包的絕對路徑將update_binary文件拷貝到內存文件系統的/tmp/update_binary中。以便後面使用。
⑥pipe():創建管道,用於下面的子進程和父進程之間的通信。
⑦fork():創建子進程。其中的子進程主要負責執行binary(execv(binary,args),即執行我們的安裝命令腳本),父進程負責接受子進程發送的命令去更新ui顯示(顯示當前的進度)。子父進程間通信依靠管道。
⑧其中,在創建子進程後,父進程有兩個作用。一是通過管道接受子進程發送的命令來更新UI顯示。二是等待子進程退出並返回INSTALL SUCCESS。其中子進程在解析執行安裝腳本的同時所發送的命令有以下幾種:
progress <frac> <secs>:根據第二個參數secs(秒)來設置進度條。
set_progress <frac>:直接設置進度條,frac取值在0.0到0.1之間。
firmware <”hboot”|”radio”><filename>:升級firmware時使用,在API V3中不再使用。
ui_print <string>:在屏幕上顯示字符串,即打印更新過程。
execv(binary,args)的作用就是去執行binary程序,這個程序的實質就是去解析update.zip包中的updater-script腳本中的命令並執行。由此,Recovery服務就進入了實際安裝update.zip包的過程。
下一篇繼續分析使用update-binary解析並執行updater-script的過程。