增加自定义property目录

打开文件system/core/init/property_service.c 增加函数

#define HOLD_PROPERTY_DIR  "/hold"
static int hold_properties_loaded = 0;


static void load_hold_properties()
{
    DIR* dir = opendir(HOLD_PROPERTY_DIR);
    int dir_fd;
    struct dirent*  entry;
    char value[PROP_VALUE_MAX];
    int fd, length;
    struct stat sb;

	if (dir == NULL) {

		//700为 /data/property的权限，这里改得和它一样，注意，这里不支持system()执行，因为sh还没有启动

//    	char tmp[100] = {0};
//    	sprintf(tmp,"mkdir %s && %s %s",HOLD_PROPERTY_DIR,"chmod 700",HOLD_PROPERTY_DIR);
//    	system(tmp);


		ERROR("hold:aaaa check mkdir %s\n",HOLD_PROPERTY_DIR);
//		if (mkdir(HOLD_PROPERTY_DIR, 0700) == -1) {
//
//			ERROR("hold:Unable mkdir %s\n", HOLD_PROPERTY_DIR);
//		}else{
//			ERROR("hold:has dir2 %s\n",HOLD_PROPERTY_DIR);
//			dir = opendir(HOLD_PROPERTY_DIR);
//		}
	}else{
		ERROR("hold:has dir %s\n",HOLD_PROPERTY_DIR);

	}

    if (dir) {
        dir_fd = dirfd(dir);
        while ((entry = readdir(dir)) != NULL) {
            if (strncmp("hold.", entry->d_name, strlen("hold.")))
                continue;
#if HAVE_DIRENT_D_TYPE
            if (entry->d_type != DT_REG)
                continue;
#endif
            /* open the file and read the property value */
            fd = openat(dir_fd, entry->d_name, O_RDONLY | O_NOFOLLOW);
            if (fd < 0) {
                ERROR("Unable to open hold property file \"%s\" errno: %d\n",
                      entry->d_name, errno);
                continue;
            }
            if (fstat(fd, &sb) < 0) {
                ERROR("fstat on hold file \"%s\" failed errno: %d\n", entry->d_name, errno);
                close(fd);
                continue;
            }

            // File must not be accessible to others, be owned by root/root, and
            // not be a hard link to any other file.
            if (((sb.st_mode & (S_IRWXG | S_IRWXO)) != 0)
                    || (sb.st_uid != 0)
                    || (sb.st_gid != 0)
                    || (sb.st_nlink != 1)) {
                ERROR("skipping insecure hold property file %s (uid=%u gid=%u nlink=%d mode=%o)\n",
                      entry->d_name, (unsigned int)sb.st_uid, (unsigned int)sb.st_gid,
                      sb.st_nlink, sb.st_mode);
                close(fd);
                continue;
            }

            length = read(fd, value, sizeof(value) - 1);
            if (length >= 0) {
                value[length] = 0;
                property_set(entry->d_name, value);
            } else {
                ERROR("Unable to read hold property file %s errno: %d\n",
                      entry->d_name, errno);
            }
            close(fd);
        }
        closedir(dir);
    } else {
        ERROR("hold:Unable to open hold property directory %s errno: %d\n", HOLD_PROPERTY_DIR, errno);
    }

    hold_properties_loaded = 1;
}

static void write_hold_property(const char *name, const char *value)
{
    char tempPath[PATH_MAX];
    char path[PATH_MAX];
    int fd;

    snprintf(tempPath, sizeof(tempPath), "%s/.temp.XXXXXX", HOLD_PROPERTY_DIR);
    fd = mkstemp(tempPath);
    if (fd < 0) {
        ERROR("Unable to write hold property to temp file %s errno: %d\n", tempPath, errno);
        return;
    }
    write(fd, value, strlen(value));
    fsync(fd);
    close(fd);

    snprintf(path, sizeof(path), "%s/%s", HOLD_PROPERTY_DIR, name);
    if (rename(tempPath, path)) {
        unlink(tempPath);
        ERROR("Unable to rename hold property file %s to %s\n", tempPath, path);
    }
}

然后修改几个地方

void property_init(void)
 {
     init_property_area();
@@ -550,6 +666,7 @@ void load_persist_props(void)
     load_override_properties();
     /* Read persistent properties after all default values have been loaded. */
     load_persistent_properties();
+    load_hold_properties();
 }

 void load_all_props(void)
@@ -563,6 +680,7 @@ void load_all_props(void)

     /* Read persistent properties after all default values have been loaded. */
     load_persistent_properties();
+    load_hold_properties();
 }

 static bool is_legal_property_name(const char* name, size_t namelen)
 {
     size_t i;
@@ -264,6 +289,13 @@ int property_set(const char *name, const char *value)
          * to prevent them from being overwritten by default values.
          */
         write_persistent_property(name, value);
+    }else if (hold_properties_loaded &&
+            strncmp("hold.", name, strlen("hold.")) == 0) {
+        /*
+         * Don't write properties to disk until after we have read all default properties
+         * to prevent them from being overwritten by default values.
+         */
+        write_hold_property(name, value);
     } else if (strcmp("selinux.reload_policy", name) == 0 &&
                strcmp("1", value) == 0) {
         selinux_reload_policy();
@@ -512,6 +544,90 @@ static void load_persistent_properties()
     persistent_properties_loaded = 1;
 }