Android之Recovery 2 --- update-binary

1、update-binary函数源码路径：/bootable/recovery/updater/updater.c
  先来看一下 bootable/recovery/updater/Android.mk

LOCAL_PATH := $(call my-dir)
# 依赖的源文件
updater_src_files := \
	install.c \
	blockimg.c \
	updater.c

include $(CLEAR_VARS)

LOCAL_MODULE_TAGS := eng

LOCAL_SRC_FILES := $(updater_src_files)

ifeq ($(TARGET_USERIMAGES_USE_EXT4), true)
LOCAL_CFLAGS += -DUSE_EXT4
LOCAL_CFLAGS += -Wno-unused-parameter
LOCAL_C_INCLUDES += system/extras/ext4_utils
LOCAL_STATIC_LIBRARIES += \
    libext4_utils_static \
    libsparse_static \
    libz
endif
# 依赖的一些静态库
LOCAL_STATIC_LIBRARIES += $(TARGET_RECOVERY_UPDATER_LIBS) $(TARGET_RECOVERY_UPDATER_EXTRA_LIBS)
LOCAL_STATIC_LIBRARIES += libapplypatch libedify libmtdutils libminzip libz
LOCAL_STATIC_LIBRARIES += libmincrypt libbz
LOCAL_STATIC_LIBRARIES += libcutils liblog libstdc++ libc
LOCAL_STATIC_LIBRARIES += libselinux
tune2fs_static_libraries := \
 libext2_com_err \
 libext2_blkid \
 libext2_quota \
 libext2_uuid_static \
 libext2_e2p \
 libext2fs
LOCAL_STATIC_LIBRARIES += libtune2fs $(tune2fs_static_libraries)

LOCAL_C_INCLUDES += external/e2fsprogs/misc
LOCAL_C_INCLUDES += $(LOCAL_PATH)/..

inc := $(call intermediates-dir-for,PACKAGING,updater_extensions)/register.inc

inc_dep_file := $(inc).dep.$(subst $(space),-,$(sort $(TARGET_RECOVERY_UPDATER_LIBS)))
$(inc_dep_file): stem := $(inc).dep
$(inc_dep_file) :
	$(hide) mkdir -p $(dir $@)
	$(hide) rm -f $(stem).*
	$(hide) touch $@

$(inc) : libs := $(TARGET_RECOVERY_UPDATER_LIBS)
$(inc) : $(inc_dep_file)
	$(hide) mkdir -p $(dir $@)
	$(hide) echo "" > $@
	$(hide) $(foreach lib,$(libs),echo "extern void Register_$(lib)(void);" >> $@;)
	$(hide) echo "void RegisterDeviceExtensions() {" >> $@
	$(hide) $(foreach lib,$(libs),echo "  Register_$(lib)();" >> $@;)
	$(hide) echo "}" >> $@

$(call intermediates-dir-for,EXECUTABLES,updater,,,$(TARGET_PREFER_32_BIT))/updater.o : $(inc)
LOCAL_C_INCLUDES += $(dir $(inc))

inc :=
inc_dep_file :=
# 生成的模块名字为 updater
LOCAL_MODULE := updater

LOCAL_FORCE_STATIC_EXECUTABLE := true
# 生成的模块为可执行文件
include $(BUILD_EXECUTABLE)

  再来看一下 bootable/recovery/updater/updater.c

#define SCRIPT_NAME "META-INF/com/google/android/updater-script"

int main(int argc, char** argv) {
    // Various things log information to stdout or stderr more or less
    // at random (though we've tried to standardize on stdout).  The
    // log file makes more sense if buffering is turned off so things
    // appear in the right order.
    setbuf(stdout, NULL);
    setbuf(stderr, NULL);

    if (argc != 4) {
        printf("unexpected number of arguments (%d)\n", argc);
        return 1;
    }

    char* version = argv[1];
    if ((version[0] != '1' && version[0] != '2' && version[0] != '3') ||
        version[1] != '\0') {
        // We support version 1, 2, or 3.
        printf("wrong updater binary API; expected 1, 2, or 3; "
                        "got %s\n",
                argv[1]);
        return 2;
    }

    // Set up the pipe for sending commands back to the parent process.

    int fd = atoi(argv[2]);
    FILE* cmd_pipe = fdopen(fd, "wb");
    setlinebuf(cmd_pipe);

    // Extract the script from the package.

    const char* package_filename = argv[3];
    MemMapping map;
    if (sysMapFile(package_filename, &map) != 0) {
        printf("failed to map package %s\n", argv[3]);
        return 3;
    }
    ZipArchive za;
    int err;
    err = mzOpenZipArchive(map.addr, map.length, &za);
    if (err != 0) {
        printf("failed to open package %s: %s\n",
               argv[3], strerror(err));
        return 3;
    }
	/* 查找安装脚本 SCRIPT_NAME 定义在上方*/
    const ZipEntry* script_entry = mzFindZipEntry(&za, SCRIPT_NAME);
    if (script_entry == NULL) {
        printf("failed to find %s in %s\n", SCRIPT_NAME, package_filename);
        return 4;
    }

    char* script = malloc(script_entry->uncompLen+1);
    if (!mzReadZipEntry(&za, script_entry, script, script_entry->uncompLen)) {
        printf("failed to read script from package\n");
        return 5;
    }
    script[script_entry->uncompLen] = '\0';

    // Configure edify's functions.
	/* 注册一些函数， 这些函数对应安装脚本中的指令 */
    RegisterBuiltins();
    RegisterInstallFunctions();
    RegisterBlockImageFunctions();
    RegisterDeviceExtensions();
    FinishRegistration();

    // Parse the script.

    Expr* root;
    int error_count = 0;
    /* 解析脚本，并执行对应动作 */
    int error = parse_string(script, &root, &error_count);
    if (error != 0 || error_count > 0) {
        printf("%d parse errors\n", error_count);
        return 6;
    }

    struct selinux_opt seopts[] = {
      { SELABEL_OPT_PATH, "/file_contexts" }
    };

    sehandle = selabel_open(SELABEL_CTX_FILE, seopts, 1);

    if (!sehandle) {
        fprintf(cmd_pipe, "ui_print Warning: No file_contexts\n");
    }

    // Evaluate the parsed script.

    UpdaterInfo updater_info;
    updater_info.cmd_pipe = cmd_pipe;
    updater_info.package_zip = &za;
    updater_info.version = atoi(version);
    updater_info.package_zip_addr = map.addr;
    updater_info.package_zip_len = map.length;

    State state;
    state.cookie = &updater_info;
    state.script = script;
    state.errmsg = NULL;

	/* 核查脚本以及结果并反馈回主进程 */
    char* result = Evaluate(&state, root);
    if (result == NULL) {
        if (state.errmsg == NULL) {
            printf("script aborted (no error message)\n");
            fprintf(cmd_pipe, "ui_print script aborted (no error message)\n");
        } else {
            printf("script aborted: %s\n", state.errmsg);
            char* line = strtok(state.errmsg, "\n");
            while (line) {
                fprintf(cmd_pipe, "ui_print %s\n", line);
                line = strtok(NULL, "\n");
            }
            fprintf(cmd_pipe, "ui_print\n");
        }
        free(state.errmsg);
        return 7;
    } else {
        fprintf(cmd_pipe, "ui_print script succeeded: result was [%s]\n", result);
        free(result);
    }

    if (updater_info.package_zip) {
        mzCloseZipArchive(updater_info.package_zip);
    }
    sysReleaseMap(&map);
    free(script);

    return 0;
}

2、parse_string函数源码路径bootable/recovery/edify/parser.y
   .y 文件属于Yacc Source，尚不熟悉，待续。。。