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platform_system_core/sdcard/sdcard.c

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/*
* 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.
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>
#include <fcntl.h>
#include <sys/mount.h>
#include <sys/stat.h>
#include <sys/statfs.h>
#include <sys/uio.h>
#include <dirent.h>
#include <private/android_filesystem_config.h>
#include "fuse.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.
*
* usage: sdcard <path> <uid> <gid>
*
* It must be run as root, but will change to uid/gid as soon as it
* mounts a filesystem on /mnt/sdcard. It will refuse to run if uid or
* 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
* kernel, you must rollback the refcount to reflect the reference the
* kernel did not actually acquire
*
*
* Bugs:
*
* - need to move/rename node on RENAME
*/
#define FUSE_TRACE 0
#if FUSE_TRACE
#define TRACE(x...) fprintf(stderr,x)
#else
#define TRACE(x...) do {} while (0)
#endif
#define ERROR(x...) fprintf(stderr,x)
#define FUSE_UNKNOWN_INO 0xffffffff
#define MOUNT_POINT "/mnt/sdcard"
struct handle {
struct node *node;
int fd;
};
struct dirhandle {
struct node *node;
DIR *d;
};
struct node {
__u64 nid;
__u64 gen;
struct node *next;
struct node *child;
struct node *all;
struct node *parent;
__u32 refcount;
__u32 namelen;
char name[1];
};
struct fuse {
__u64 next_generation;
__u64 next_node_id;
int fd;
struct node *all;
struct node root;
char rootpath[1024];
};
#define PATH_BUFFER_SIZE 1024
char *node_get_path(struct node *node, char *buf, const char *name)
{
char *out = buf + PATH_BUFFER_SIZE - 1;
int len;
out[0] = 0;
if (name) {
len = strlen(name);
goto start;
}
while (node) {
name = node->name;
len = node->namelen;
node = node->parent;
start:
if ((len + 1) > (out - buf))
return 0;
out -= len;
memcpy(out, name, len);
out --;
out[0] = '/';
}
return out;
}
void attr_from_stat(struct fuse_attr *attr, struct stat *s)
{
attr->ino = s->st_ino;
attr->size = s->st_size;
attr->blocks = s->st_blocks;
attr->atime = s->st_atime;
attr->mtime = s->st_mtime;
attr->ctime = s->st_ctime;
attr->atimensec = s->st_atime_nsec;
attr->mtimensec = s->st_mtime_nsec;
attr->ctimensec = s->st_ctime_nsec;
attr->mode = s->st_mode;
attr->nlink = s->st_nlink;
/* force permissions to something reasonable:
* world readable
* writable by the sdcard group
*/
if (attr->mode & 0100) {
attr->mode = (attr->mode & (~0777)) | 0775;
} else {
attr->mode = (attr->mode & (~0777)) | 0664;
}
/* all files owned by root.sdcard */
attr->uid = 0;
attr->gid = AID_SDCARD_RW;
}
int node_get_attr(struct node *node, struct fuse_attr *attr)
{
int res;
struct stat s;
char *path, buffer[PATH_BUFFER_SIZE];
path = node_get_path(node, buffer, 0);
res = lstat(path, &s);
if (res < 0) {
ERROR("lstat('%s') errno %d\n", path, errno);
return -1;
}
attr_from_stat(attr, &s);
attr->ino = node->nid;
return 0;
}
struct node *node_create(struct node *parent, const char *name, __u64 nid, __u64 gen)
{
struct node *node;
int namelen = strlen(name);
node = calloc(1, sizeof(struct node) + namelen);
if (node == 0) {
return 0;
}
node->nid = nid;
node->gen = gen;
node->parent = parent;
node->next = parent->child;
parent->child = node;
memcpy(node->name, name, namelen + 1);
node->namelen = namelen;
parent->refcount++;
return node;
}
void fuse_init(struct fuse *fuse, int fd, const char *path)
{
fuse->fd = fd;
fuse->next_node_id = 2;
fuse->next_generation = 0;
fuse->all = &fuse->root;
fuse->root.nid = FUSE_ROOT_ID; /* 1 */
fuse->root.next = 0;
fuse->root.child = 0;
fuse->root.parent = 0;
fuse->root.all = 0;
fuse->root.refcount = 2;
strcpy(fuse->root.name, path);
fuse->root.namelen = strlen(fuse->root.name);
}
static inline void *id_to_ptr(__u64 nid)
{
return (void *) nid;
}
static inline __u64 ptr_to_id(void *ptr)
{
return (__u64) ptr;
}
struct node *lookup_by_inode(struct fuse *fuse, __u64 nid)
{
if (nid == FUSE_ROOT_ID) {
return &fuse->root;
} else {
return id_to_ptr(nid);
}
}
struct node *lookup_child_by_name(struct node *node, const char *name)
{
for (node = node->child; node; node = node->next) {
if (!strcmp(name, node->name)) {
return node;
}
}
return 0;
}
struct node *lookup_child_by_inode(struct node *node, __u64 nid)
{
for (node = node->child; node; node = node->next) {
if (node->nid == nid) {
return node;
}
}
return 0;
}
struct node *node_lookup(struct fuse *fuse, struct node *parent, const char *name,
struct fuse_attr *attr)
{
int res;
struct stat s;
char *path, buffer[PATH_BUFFER_SIZE];
struct node *node;
path = node_get_path(parent, buffer, name);
/* XXX error? */
res = lstat(path, &s);
if (res < 0)
return 0;
node = lookup_child_by_name(parent, name);
if (!node) {
node = node_create(parent, name, fuse->next_node_id++, fuse->next_generation++);
if (!node)
return 0;
node->nid = ptr_to_id(node);
node->all = fuse->all;
fuse->all = node;
}
attr_from_stat(attr, &s);
attr->ino = node->nid;
return node;
}
void node_release(struct node *node)
{
TRACE("RELEASE %p (%s) rc=%d\n", node, node->name, node->refcount);
node->refcount--;
if (node->refcount == 0) {
if (node->parent->child == node) {
node->parent->child = node->parent->child->next;
} else {
struct node *node2;
node2 = node->parent->child;
while (node2->next != node)
node2 = node2->next;
node2->next = node->next;
}
TRACE("DESTROY %p (%s)\n", node, node->name);
node_release(node->parent);
node->parent = 0;
node->next = 0;
/* TODO: remove debugging - poison memory */
memset(node, 0xef, sizeof(*node) + strlen(node->name));
free(node);
}
}
void fuse_status(struct fuse *fuse, __u64 unique, int err)
{
struct fuse_out_header hdr;
hdr.len = sizeof(hdr);
hdr.error = err;
hdr.unique = unique;
if (err) {
// ERROR("*** %d ***\n", err);
}
write(fuse->fd, &hdr, sizeof(hdr));
}
void fuse_reply(struct fuse *fuse, __u64 unique, void *data, int len)
{
struct fuse_out_header hdr;
struct iovec vec[2];
int res;
hdr.len = len + sizeof(hdr);
hdr.error = 0;
hdr.unique = unique;
vec[0].iov_base = &hdr;
vec[0].iov_len = sizeof(hdr);
vec[1].iov_base = data;
vec[1].iov_len = len;
res = writev(fuse->fd, vec, 2);
if (res < 0) {
ERROR("*** REPLY FAILED *** %d\n", errno);
}
}
void lookup_entry(struct fuse *fuse, struct node *node,
const char *name, __u64 unique)
{
struct fuse_entry_out out;
memset(&out, 0, sizeof(out));
node = node_lookup(fuse, node, name, &out.attr);
if (!node) {
fuse_status(fuse, unique, -ENOENT);
return;
}
node->refcount++;
// fprintf(stderr,"ACQUIRE %p (%s) rc=%d\n", node, node->name, node->refcount);
out.nodeid = node->nid;
out.generation = node->gen;
out.entry_valid = 10;
out.attr_valid = 10;
fuse_reply(fuse, unique, &out, sizeof(out));
}
void handle_fuse_request(struct fuse *fuse, struct fuse_in_header *hdr, void *data, unsigned len)
{
struct node *node;
if ((len < sizeof(*hdr)) || (hdr->len != len)) {
ERROR("malformed header\n");
return;
}
len -= hdr->len;
if (hdr->nodeid) {
node = lookup_by_inode(fuse, hdr->nodeid);
if (!node) {
fuse_status(fuse, hdr->unique, -ENOENT);
return;
}
} else {
node = 0;
}
switch (hdr->opcode) {
case FUSE_LOOKUP: { /* bytez[] -> entry_out */
TRACE("LOOKUP %llx %s\n", hdr->nodeid, (char*) data);
lookup_entry(fuse, node, (char*) data, hdr->unique);
return;
}
case FUSE_FORGET: {
struct fuse_forget_in *req = data;
TRACE("FORGET %llx (%s) #%lld\n", hdr->nodeid, node->name, req->nlookup);
/* no reply */
while (req->nlookup--)
node_release(node);
return;
}
case FUSE_GETATTR: { /* getattr_in -> attr_out */
struct fuse_getattr_in *req = data;
struct fuse_attr_out out;
TRACE("GETATTR flags=%x fh=%llx\n",req->getattr_flags, req->fh);
memset(&out, 0, sizeof(out));
node_get_attr(node, &out.attr);
out.attr_valid = 10;
fuse_reply(fuse, hdr->unique, &out, sizeof(out));
return;
}
case FUSE_SETATTR: { /* setattr_in -> attr_out */
struct fuse_setattr_in *req = data;
struct fuse_attr_out out;
TRACE("SETATTR fh=%llx id=%llx valid=%x\n",
req->fh, hdr->nodeid, req->valid);
/* XXX */
memset(&out, 0, sizeof(out));
node_get_attr(node, &out.attr);
out.attr_valid = 10;
fuse_reply(fuse, hdr->unique, &out, sizeof(out));
return;
}
// case FUSE_READLINK:
// case FUSE_SYMLINK:
case FUSE_MKNOD: { /* mknod_in, bytez[] -> entry_out */
struct fuse_mknod_in *req = data;
char *path, buffer[PATH_BUFFER_SIZE];
char *name = ((char*) data) + sizeof(*req);
int res;
TRACE("MKNOD %s @ %llx\n", name, hdr->nodeid);
path = node_get_path(node, buffer, name);
req->mode = (req->mode & (~0777)) | 0664;
res = mknod(path, req->mode, req->rdev); /* XXX perm?*/
if (res < 0) {
fuse_status(fuse, hdr->unique, -errno);
} else {
lookup_entry(fuse, node, name, hdr->unique);
}
return;
}
case FUSE_MKDIR: { /* mkdir_in, bytez[] -> entry_out */
struct fuse_mkdir_in *req = data;
struct fuse_entry_out out;
char *path, buffer[PATH_BUFFER_SIZE];
char *name = ((char*) data) + sizeof(*req);
int res;
TRACE("MKDIR %s @ %llx 0%o\n", name, hdr->nodeid, req->mode);
path = node_get_path(node, buffer, name);
req->mode = (req->mode & (~0777)) | 0775;
res = mkdir(path, req->mode);
if (res < 0) {
fuse_status(fuse, hdr->unique, -errno);
} else {
lookup_entry(fuse, node, name, hdr->unique);
}
return;
}
case FUSE_UNLINK: { /* bytez[] -> */
char *path, buffer[PATH_BUFFER_SIZE];
int res;
TRACE("UNLINK %s @ %llx\n", (char*) data, hdr->nodeid);
path = node_get_path(node, buffer, (char*) data);
res = unlink(path);
fuse_status(fuse, hdr->unique, res ? -errno : 0);
return;
}
case FUSE_RMDIR: { /* bytez[] -> */
char *path, buffer[PATH_BUFFER_SIZE];
int res;
TRACE("RMDIR %s @ %llx\n", (char*) data, hdr->nodeid);
path = node_get_path(node, buffer, (char*) data);
res = rmdir(path);
fuse_status(fuse, hdr->unique, res ? -errno : 0);
return;
}
case FUSE_RENAME: { /* rename_in, oldname, newname -> */
struct fuse_rename_in *req = data;
char *oldname = ((char*) data) + sizeof(*req);
char *newname = oldname + strlen(oldname) + 1;
char *oldpath, oldbuffer[PATH_BUFFER_SIZE];
char *newpath, newbuffer[PATH_BUFFER_SIZE];
struct node *newnode;
int res;
newnode = lookup_by_inode(fuse, req->newdir);
if (!newnode) {
fuse_status(fuse, hdr->unique, -ENOENT);
return;
}
oldpath = node_get_path(node, oldbuffer, oldname);
newpath = node_get_path(newnode, newbuffer, newname);
res = rename(oldpath, newpath);
fuse_status(fuse, hdr->unique, res ? -errno : 0);
return;
}
// case FUSE_LINK:
case FUSE_OPEN: { /* open_in -> open_out */
struct fuse_open_in *req = data;
struct fuse_open_out out;
char *path, buffer[PATH_BUFFER_SIZE];
struct handle *h;
h = malloc(sizeof(*h));
if (!h) {
fuse_status(fuse, hdr->unique, -ENOMEM);
return;
}
path = node_get_path(node, buffer, 0);
TRACE("OPEN %llx '%s' 0%o fh=%p\n", hdr->nodeid, path, req->flags, h);
h->fd = open(path, req->flags);
if (h->fd < 0) {
ERROR("ERROR\n");
fuse_status(fuse, hdr->unique, errno);
free(h);
return;
}
out.fh = ptr_to_id(h);
out.open_flags = 0;
out.padding = 0;
fuse_reply(fuse, hdr->unique, &out, sizeof(out));
return;
}
case FUSE_READ: { /* read_in -> byte[] */
char buffer[128 * 1024];
struct fuse_read_in *req = data;
struct handle *h = id_to_ptr(req->fh);
int res;
TRACE("READ %p(%d) %u@%llu\n", h, h->fd, req->size, req->offset);
if (req->size > sizeof(buffer)) {
fuse_status(fuse, hdr->unique, -EINVAL);
return;
}
res = pread(h->fd, buffer, req->size, req->offset);
if (res < 0) {
fuse_status(fuse, hdr->unique, errno);
return;
}
fuse_reply(fuse, hdr->unique, buffer, res);
return;
}
case FUSE_WRITE: { /* write_in, byte[write_in.size] -> write_out */
struct fuse_write_in *req = data;
struct fuse_write_out out;
struct handle *h = id_to_ptr(req->fh);
int res;
TRACE("WRITE %p(%d) %u@%llu\n", h, h->fd, req->size, req->offset);
res = pwrite(h->fd, ((char*) data) + sizeof(*req), req->size, req->offset);
if (res < 0) {
fuse_status(fuse, hdr->unique, errno);
return;
}
out.size = res;
fuse_reply(fuse, hdr->unique, &out, sizeof(out));
goto oops;
}
case FUSE_STATFS: { /* getattr_in -> attr_out */
struct statfs stat;
struct fuse_statfs_out out;
int res;
TRACE("STATFS\n");
if (statfs(fuse->root.name, &stat)) {
fuse_status(fuse, hdr->unique, -errno);
return;
}
memset(&out, 0, sizeof(out));
out.st.blocks = stat.f_blocks;
out.st.bfree = stat.f_bfree;
out.st.bavail = stat.f_bavail;
out.st.files = stat.f_files;
out.st.ffree = stat.f_ffree;
out.st.bsize = stat.f_bsize;
out.st.namelen = stat.f_namelen;
out.st.frsize = stat.f_frsize;
fuse_reply(fuse, hdr->unique, &out, sizeof(out));
return;
}
case FUSE_RELEASE: { /* release_in -> */
struct fuse_release_in *req = data;
struct handle *h = id_to_ptr(req->fh);
TRACE("RELEASE %p(%d)\n", h, h->fd);
close(h->fd);
free(h);
fuse_status(fuse, hdr->unique, 0);
return;
}
// case FUSE_FSYNC:
// case FUSE_SETXATTR:
// case FUSE_GETXATTR:
// case FUSE_LISTXATTR:
// case FUSE_REMOVEXATTR:
case FUSE_FLUSH:
fuse_status(fuse, hdr->unique, 0);
return;
case FUSE_OPENDIR: { /* open_in -> open_out */
struct fuse_open_in *req = data;
struct fuse_open_out out;
char *path, buffer[PATH_BUFFER_SIZE];
struct dirhandle *h;
h = malloc(sizeof(*h));
if (!h) {
fuse_status(fuse, hdr->unique, -ENOMEM);
return;
}
path = node_get_path(node, buffer, 0);
TRACE("OPENDIR %llx '%s'\n", hdr->nodeid, path);
h->d = opendir(path);
if (h->d == 0) {
ERROR("ERROR\n");
fuse_status(fuse, hdr->unique, -errno);
free(h);
return;
}
out.fh = ptr_to_id(h);
fuse_reply(fuse, hdr->unique, &out, sizeof(out));
return;
}
case FUSE_READDIR: {
struct fuse_read_in *req = data;
char buffer[8192];
struct fuse_dirent *fde = (struct fuse_dirent*) buffer;
struct dirent *de;
struct dirhandle *h = id_to_ptr(req->fh);
TRACE("READDIR %p\n", h);
de = readdir(h->d);
if (!de) {
fuse_status(fuse, hdr->unique, 0);
return;
}
fde->ino = FUSE_UNKNOWN_INO;
fde->off = 0;
fde->type = de->d_type;
fde->namelen = strlen(de->d_name);
memcpy(fde->name, de->d_name, fde->namelen + 1);
fuse_reply(fuse, hdr->unique, fde,
FUSE_DIRENT_ALIGN(sizeof(struct fuse_dirent) + fde->namelen));
return;
}
case FUSE_RELEASEDIR: { /* release_in -> */
struct fuse_release_in *req = data;
struct dirhandle *h = id_to_ptr(req->fh);
TRACE("RELEASEDIR %p\n",h);
closedir(h->d);
free(h);
fuse_status(fuse, hdr->unique, 0);
return;
}
// case FUSE_FSYNCDIR:
case FUSE_INIT: { /* init_in -> init_out */
struct fuse_init_in *req = data;
struct fuse_init_out out;
TRACE("INIT ver=%d.%d maxread=%d flags=%x\n",
req->major, req->minor, req->max_readahead, req->flags);
out.major = FUSE_KERNEL_VERSION;
out.minor = FUSE_KERNEL_MINOR_VERSION;
out.max_readahead = req->max_readahead;
out.flags = FUSE_ATOMIC_O_TRUNC;
out.max_background = 32;
out.congestion_threshold = 32;
out.max_write = 256 * 1024;
fuse_reply(fuse, hdr->unique, &out, sizeof(out));
return;
}
default: {
struct fuse_out_header h;
ERROR("NOTIMPL op=%d uniq=%llx nid=%llx\n",
hdr->opcode, hdr->unique, hdr->nodeid);
oops:
h.len = sizeof(h);
h.error = -ENOSYS;
h.unique = hdr->unique;
write(fuse->fd, &h, sizeof(h));
break;
}
}
}
void handle_fuse_requests(struct fuse *fuse)
{
unsigned char req[256 * 1024 + 128];
int len;
for (;;) {
len = read(fuse->fd, req, 8192);
if (len < 0) {
if (errno == EINTR)
continue;
ERROR("handle_fuse_requests: errno=%d\n", errno);
return;
}
handle_fuse_request(fuse, (void*) req, (void*) (req + sizeof(struct fuse_in_header)), len);
}
}
int main(int argc, char **argv)
{
struct fuse fuse;
char opts[256];
int fd;
int res;
unsigned uid;
unsigned gid;
const char *path;
if (argc != 4) {
ERROR("usage: sdcard <path> <uid> <gid>\n");
return -1;
}
uid = strtoul(argv[2], 0, 10);
gid = strtoul(argv[3], 0, 10);
if (!uid || !gid) {
ERROR("uid and gid must be nonzero\n");
return -1;
}
path = argv[1];
/* cleanup from previous instance, if necessary */
umount2(MOUNT_POINT, 2);
fd = open("/dev/fuse", O_RDWR);
if (fd < 0){
ERROR("cannot open fuse device (%d)\n", errno);
return -1;
}
sprintf(opts, "fd=%i,rootmode=40000,default_permissions,allow_other,"
"user_id=%d,group_id=%d", fd, uid, gid);
res = mount("/dev/fuse", MOUNT_POINT, "fuse", MS_NOSUID | MS_NODEV, opts);
if (res < 0) {
ERROR("cannot mount fuse filesystem (%d)\n", errno);
return -1;
}
if (setgid(gid) < 0) {
ERROR("cannot setgid!\n");
return -1;
}
if (setuid(uid) < 0) {
ERROR("cannot setuid!\n");
return -1;
}
fuse_init(&fuse, fd, path);
umask(0);
handle_fuse_requests(&fuse);
return 0;
}
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