sdcard.c

/*
 * Copyright (C) 2010 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.
 */

#define LOG_TAG "sdcard"

#include <ctype.h>
#include <dirent.h>
#include <errno.h>
#include <fcntl.h>
#include <inttypes.h>
#include <limits.h>
#include <linux/fuse.h>
#include <pthread.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/inotify.h>
#include <sys/mount.h>
#include <sys/param.h>
#include <sys/resource.h>
#include <sys/stat.h>
#include <sys/statfs.h>
#include <sys/time.h>
#include <sys/types.h>
#include <sys/uio.h>
#include <unistd.h>

#include <cutils/fs.h>
#include <cutils/hashmap.h>
#include <cutils/log.h>
#include <cutils/multiuser.h>
#include <cutils/properties.h>
#include <packagelistparser/packagelistparser.h>

#include <private/android_filesystem_config.h>

/* README
 *
 * What is this?
 *
 * sdcard is a program that uses FUSE to emulate FAT-on-sdcard style
 * directory permissions (all files are given fixed owner, group, and
 * permissions at creation, owner, group, and permissions are not
 * changeable, symlinks and hardlinks are not createable, etc.
 *
 * See usage() for command line options.
 *
 * It must be run as root, but will drop to requested UID/GID as soon as it
 * mounts a filesystem.  It will refuse to run if requested UID/GID are zero.
 *
 * Things I believe to be true:
 *
 * - ops that return a fuse_entry (LOOKUP, MKNOD, MKDIR, LINK, SYMLINK,
 * CREAT) must bump that node's refcount
 * - don't forget that FORGET can forget multiple references (req->nlookup)
 * - if an op that returns a fuse_entry fails writing the reply to the