sdcard.c revision 90749774edd0c0cab327b62ce43cb4dfd33e897d 
1/*
2 * Copyright (C) 2010 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17#include <stdio.h>
18#include <stdlib.h>
19#include <string.h>
20#include <unistd.h>
21#include <errno.h>
22#include <fcntl.h>
23#include <sys/mount.h>
24#include <sys/stat.h>
25#include <sys/statfs.h>
26#include <sys/uio.h>
27#include <dirent.h>
28
29#include <private/android_filesystem_config.h>
30
31#include "fuse.h"
32
33/* README
34 *
35 * What is this?
36 *
37 * sdcard is a program that uses FUSE to emulate FAT-on-sdcard style
38 * directory permissions (all files are given fixed owner, group, and
39 * permissions at creation, owner, group, and permissions are not
40 * changeable, symlinks and hardlinks are not createable, etc.
41 *
42 * usage:  sdcard <path> <uid> <gid>
43 *
44 * It must be run as root, but will change to uid/gid as soon as it
45 * mounts a filesystem on /mnt/sdcard.  It will refuse to run if uid or
46 * gid are zero.
47 *
48 *
49 * Things I believe to be true:
50 *
51 * - ops that return a fuse_entry (LOOKUP, MKNOD, MKDIR, LINK, SYMLINK,
52 * CREAT) must bump that node's refcount
53 * - don't forget that FORGET can forget multiple references (req->nlookup)
54 * - if an op that returns a fuse_entry fails writing the reply to the
55 * kernel, you must rollback the refcount to reflect the reference the
56 * kernel did not actually acquire
57 *
58 */
59
60#define FUSE_TRACE 0
61
62#if FUSE_TRACE
63#define TRACE(x...) fprintf(stderr,x)
64#else
65#define TRACE(x...) do {} while (0)
66#endif
67
68#define ERROR(x...) fprintf(stderr,x)
69
70#define FUSE_UNKNOWN_INO 0xffffffff
71
72#define MOUNT_POINT "/mnt/sdcard"
73
74struct handle {
75    struct node *node;
76    int fd;
77};
78
79struct dirhandle {
80    struct node *node;
81    DIR *d;
82};
83
84struct node {
85    __u64 nid;
86    __u64 gen;
87
88    struct node *next;          /* per-dir sibling list */
89    struct node *child;         /* first contained file by this dir */
90    struct node *all;           /* global node list */
91    struct node *parent;        /* containing directory */
92
93    __u32 refcount;
94    __u32 namelen;
95
96    char *name;
97};
98
99struct fuse {
100    __u64 next_generation;
101    __u64 next_node_id;
102
103    int fd;
104
105    struct node *all;
106
107    struct node root;
108    char rootpath[1024];
109};
110
111#define PATH_BUFFER_SIZE 1024
112
113/*
114 * Get the real-life absolute path to a node.
115 *   node: start at this node
116 *   buf: storage for returned string
117 *   name: append this string to path if set
118 */
119char *node_get_path(struct node *node, char *buf, const char *name)
120{
121    char *out = buf + PATH_BUFFER_SIZE - 1;
122    int len;
123    out[0] = 0;
124
125    if (name) {
126        len = strlen(name);
127        goto start;
128    }
129
130    while (node) {
131        name = node->name;
132        len = node->namelen;
133        node = node->parent;
134    start:
135        if ((len + 1) > (out - buf))
136            return 0;
137        out -= len;
138        memcpy(out, name, len);
139        out --;
140        out[0] = '/';
141    }
142
143    return out;
144}
145
146void attr_from_stat(struct fuse_attr *attr, struct stat *s)
147{
148    attr->ino = s->st_ino;
149    attr->size = s->st_size;
150    attr->blocks = s->st_blocks;
151    attr->atime = s->st_atime;
152    attr->mtime = s->st_mtime;
153    attr->ctime = s->st_ctime;
154    attr->atimensec = s->st_atime_nsec;
155    attr->mtimensec = s->st_mtime_nsec;
156    attr->ctimensec = s->st_ctime_nsec;
157    attr->mode = s->st_mode;
158    attr->nlink = s->st_nlink;
159
160        /* force permissions to something reasonable:
161         * world readable
162         * writable by the sdcard group
163         */
164    if (attr->mode & 0100) {
165        attr->mode = (attr->mode & (~0777)) | 0775;
166    } else {
167        attr->mode = (attr->mode & (~0777)) | 0664;
168    }
169
170        /* all files owned by root.sdcard */
171    attr->uid = 0;
172    attr->gid = AID_SDCARD_RW;
173}
174
175int node_get_attr(struct node *node, struct fuse_attr *attr)
176{
177    int res;
178    struct stat s;
179    char *path, buffer[PATH_BUFFER_SIZE];
180
181    path = node_get_path(node, buffer, 0);
182    res = lstat(path, &s);
183    if (res < 0) {
184        ERROR("lstat('%s') errno %d\n", path, errno);
185        return -1;
186    }
187
188    attr_from_stat(attr, &s);
189    attr->ino = node->nid;
190
191    return 0;
192}
193
194static void add_node_to_parent(struct node *node, struct node *parent) {
195    node->parent = parent;
196    node->next = parent->child;
197    parent->child = node;
198    parent->refcount++;
199}
200
201struct node *node_create(struct node *parent, const char *name, __u64 nid, __u64 gen)
202{
203    struct node *node;
204    int namelen = strlen(name);
205
206    node = calloc(1, sizeof(struct node));
207    if (node == 0) {
208        return 0;
209    }
210    node->name = malloc(namelen + 1);
211    if (node->name == 0) {
212        free(node);
213        return 0;
214    }
215
216    node->nid = nid;
217    node->gen = gen;
218    add_node_to_parent(node, parent);
219    memcpy(node->name, name, namelen + 1);
220    node->namelen = namelen;
221
222    return node;
223}
224
225static char *rename_node(struct node *node, const char *name)
226{
227    node->namelen = strlen(name);
228    char *newname = realloc(node->name, node->namelen + 1);
229    if (newname == 0)
230        return 0;
231    node->name = newname;
232    memcpy(node->name, name, node->namelen + 1);
233    return node->name;
234}
235
236void fuse_init(struct fuse *fuse, int fd, const char *path)
237{
238    fuse->fd = fd;
239    fuse->next_node_id = 2;
240    fuse->next_generation = 0;
241
242    fuse->all = &fuse->root;
243
244    fuse->root.nid = FUSE_ROOT_ID; /* 1 */
245    fuse->root.next = 0;
246    fuse->root.child = 0;
247    fuse->root.parent = 0;
248
249    fuse->root.all = 0;
250    fuse->root.refcount = 2;
251
252    fuse->root.name = 0;
253    rename_node(&fuse->root, path);
254}
255
256static inline void *id_to_ptr(__u64 nid)
257{
258    return (void *) nid;
259}
260
261static inline __u64 ptr_to_id(void *ptr)
262{
263    return (__u64) ptr;
264}
265
266
267struct node *lookup_by_inode(struct fuse *fuse, __u64 nid)
268{
269    if (nid == FUSE_ROOT_ID) {
270        return &fuse->root;
271    } else {
272        return id_to_ptr(nid);
273    }
274}
275
276struct node *lookup_child_by_name(struct node *node, const char *name)
277{
278    for (node = node->child; node; node = node->next) {
279        if (!strcmp(name, node->name)) {
280            return node;
281        }
282    }
283    return 0;
284}
285
286struct node *lookup_child_by_inode(struct node *node, __u64 nid)
287{
288    for (node = node->child; node; node = node->next) {
289        if (node->nid == nid) {
290            return node;
291        }
292    }
293    return 0;
294}
295
296static void dec_refcount(struct node *node) {
297    if (node->refcount > 0) {
298        node->refcount--;
299        TRACE("dec_refcount %p(%s) -> %d\n", node, node->name, node->refcount);
300    } else {
301        ERROR("Zero refcnt %p\n", node);
302    }
303 }
304
305static struct node *remove_child(struct node *parent, __u64 nid)
306{
307    struct node *prev = 0;
308    struct node *node;
309
310    for (node = parent->child; node; node = node->next) {
311        if (node->nid == nid) {
312            if (prev) {
313                prev->next = node->next;
314            } else {
315                parent->child = node->next;
316            }
317            node->next = 0;
318            node->parent = 0;
319            dec_refcount(parent);
320            return node;
321        }
322        prev = node;
323    }
324    return 0;
325}
326
327struct node *node_lookup(struct fuse *fuse, struct node *parent, const char *name,
328                         struct fuse_attr *attr)
329{
330    int res;
331    struct stat s;
332    char *path, buffer[PATH_BUFFER_SIZE];
333    struct node *node;
334
335    path = node_get_path(parent, buffer, name);
336        /* XXX error? */
337
338    res = lstat(path, &s);
339    if (res < 0)
340        return 0;
341
342    node = lookup_child_by_name(parent, name);
343    if (!node) {
344        node = node_create(parent, name, fuse->next_node_id++, fuse->next_generation++);
345        if (!node)
346            return 0;
347        node->nid = ptr_to_id(node);
348        node->all = fuse->all;
349        fuse->all = node;
350    }
351
352    attr_from_stat(attr, &s);
353    attr->ino = node->nid;
354
355    return node;
356}
357
358void node_release(struct node *node)
359{
360    TRACE("RELEASE %p (%s) rc=%d\n", node, node->name, node->refcount);
361    dec_refcount(node);
362    if (node->refcount == 0) {
363        if (node->parent->child == node) {
364            node->parent->child = node->parent->child->next;
365        } else {
366            struct node *node2;
367
368            node2 = node->parent->child;
369            while (node2->next != node)
370                node2 = node2->next;
371            node2->next = node->next;
372        }
373
374        TRACE("DESTROY %p (%s)\n", node, node->name);
375
376        node_release(node->parent);
377
378        node->parent = 0;
379        node->next = 0;
380
381            /* TODO: remove debugging - poison memory */
382        memset(node->name, 0xef, node->namelen);
383        free(node->name);
384        memset(node, 0xfc, sizeof(*node));
385        free(node);
386    }
387}
388
389void fuse_status(struct fuse *fuse, __u64 unique, int err)
390{
391    struct fuse_out_header hdr;
392    hdr.len = sizeof(hdr);
393    hdr.error = err;
394    hdr.unique = unique;
395    if (err) {
396//        ERROR("*** %d ***\n", err);
397    }
398    write(fuse->fd, &hdr, sizeof(hdr));
399}
400
401void fuse_reply(struct fuse *fuse, __u64 unique, void *data, int len)
402{
403    struct fuse_out_header hdr;
404    struct iovec vec[2];
405    int res;
406
407    hdr.len = len + sizeof(hdr);
408    hdr.error = 0;
409    hdr.unique = unique;
410
411    vec[0].iov_base = &hdr;
412    vec[0].iov_len = sizeof(hdr);
413    vec[1].iov_base = data;
414    vec[1].iov_len = len;
415
416    res = writev(fuse->fd, vec, 2);
417    if (res < 0) {
418        ERROR("*** REPLY FAILED *** %d\n", errno);
419    }
420}
421
422void lookup_entry(struct fuse *fuse, struct node *node,
423                  const char *name, __u64 unique)
424{
425    struct fuse_entry_out out;
426
427    memset(&out, 0, sizeof(out));
428
429    node = node_lookup(fuse, node, name, &out.attr);
430    if (!node) {
431        fuse_status(fuse, unique, -ENOENT);
432        return;
433    }
434
435    node->refcount++;
436//    fprintf(stderr,"ACQUIRE %p (%s) rc=%d\n", node, node->name, node->refcount);
437    out.nodeid = node->nid;
438    out.generation = node->gen;
439    out.entry_valid = 10;
440    out.attr_valid = 10;
441
442    fuse_reply(fuse, unique, &out, sizeof(out));
443}
444
445void handle_fuse_request(struct fuse *fuse, struct fuse_in_header *hdr, void *data, unsigned len)
446{
447    struct node *node;
448
449    if ((len < sizeof(*hdr)) || (hdr->len != len)) {
450        ERROR("malformed header\n");
451        return;
452    }
453
454    len -= hdr->len;
455
456    if (hdr->nodeid) {
457        node = lookup_by_inode(fuse, hdr->nodeid);
458        if (!node) {
459            fuse_status(fuse, hdr->unique, -ENOENT);
460            return;
461        }
462    } else {
463        node = 0;
464    }
465
466    switch (hdr->opcode) {
467    case FUSE_LOOKUP: { /* bytez[] -> entry_out */
468        TRACE("LOOKUP %llx %s\n", hdr->nodeid, (char*) data);
469        lookup_entry(fuse, node, (char*) data, hdr->unique);
470        return;
471    }
472    case FUSE_FORGET: {
473        struct fuse_forget_in *req = data;
474        TRACE("FORGET %llx (%s) #%lld\n", hdr->nodeid, node->name, req->nlookup);
475            /* no reply */
476        while (req->nlookup--)
477            node_release(node);
478        return;
479    }
480    case FUSE_GETATTR: { /* getattr_in -> attr_out */
481        struct fuse_getattr_in *req = data;
482        struct fuse_attr_out out;
483
484        TRACE("GETATTR flags=%x fh=%llx\n", req->getattr_flags, req->fh);
485
486        memset(&out, 0, sizeof(out));
487        node_get_attr(node, &out.attr);
488        out.attr_valid = 10;
489
490        fuse_reply(fuse, hdr->unique, &out, sizeof(out));
491        return;
492    }
493    case FUSE_SETATTR: { /* setattr_in -> attr_out */
494        struct fuse_setattr_in *req = data;
495        struct fuse_attr_out out;
496        char *path, buffer[PATH_BUFFER_SIZE];
497        int res = 0;
498
499        TRACE("SETATTR fh=%llx id=%llx valid=%x\n",
500              req->fh, hdr->nodeid, req->valid);
501
502        /* XXX: incomplete implementation -- truncate only.  chmod/chown
503         * should NEVER be implemented. */
504
505        path = node_get_path(node, buffer, 0);
506        if (req->valid & FATTR_SIZE)
507            res = truncate(path, req->size);
508
509        memset(&out, 0, sizeof(out));
510        node_get_attr(node, &out.attr);
511        out.attr_valid = 10;
512
513        if (res)
514            fuse_status(fuse, hdr->unique, -errno);
515        else
516            fuse_reply(fuse, hdr->unique, &out, sizeof(out));
517        return;
518    }
519//    case FUSE_READLINK:
520//    case FUSE_SYMLINK:
521    case FUSE_MKNOD: { /* mknod_in, bytez[] -> entry_out */
522        struct fuse_mknod_in *req = data;
523        char *path, buffer[PATH_BUFFER_SIZE];
524        char *name = ((char*) data) + sizeof(*req);
525        int res;
526        TRACE("MKNOD %s @ %llx\n", name, hdr->nodeid);
527        path = node_get_path(node, buffer, name);
528
529        req->mode = (req->mode & (~0777)) | 0664;
530        res = mknod(path, req->mode, req->rdev); /* XXX perm?*/
531        if (res < 0) {
532            fuse_status(fuse, hdr->unique, -errno);
533        } else {
534            lookup_entry(fuse, node, name, hdr->unique);
535        }
536        return;
537    }
538    case FUSE_MKDIR: { /* mkdir_in, bytez[] -> entry_out */
539        struct fuse_mkdir_in *req = data;
540        struct fuse_entry_out out;
541        char *path, buffer[PATH_BUFFER_SIZE];
542        char *name = ((char*) data) + sizeof(*req);
543        int res;
544        TRACE("MKDIR %s @ %llx 0%o\n", name, hdr->nodeid, req->mode);
545        path = node_get_path(node, buffer, name);
546
547        req->mode = (req->mode & (~0777)) | 0775;
548        res = mkdir(path, req->mode);
549        if (res < 0) {
550            fuse_status(fuse, hdr->unique, -errno);
551        } else {
552            lookup_entry(fuse, node, name, hdr->unique);
553        }
554        return;
555    }
556    case FUSE_UNLINK: { /* bytez[] -> */
557        char *path, buffer[PATH_BUFFER_SIZE];
558        int res;
559        TRACE("UNLINK %s @ %llx\n", (char*) data, hdr->nodeid);
560        path = node_get_path(node, buffer, (char*) data);
561        res = unlink(path);
562        fuse_status(fuse, hdr->unique, res ? -errno : 0);
563        return;
564    }
565    case FUSE_RMDIR: { /* bytez[] -> */
566        char *path, buffer[PATH_BUFFER_SIZE];
567        int res;
568        TRACE("RMDIR %s @ %llx\n", (char*) data, hdr->nodeid);
569        path = node_get_path(node, buffer, (char*) data);
570        res = rmdir(path);
571        fuse_status(fuse, hdr->unique, res ? -errno : 0);
572        return;
573    }
574    case FUSE_RENAME: { /* rename_in, oldname, newname ->  */
575        struct fuse_rename_in *req = data;
576        char *oldname = ((char*) data) + sizeof(*req);
577        char *newname = oldname + strlen(oldname) + 1;
578        char *oldpath, oldbuffer[PATH_BUFFER_SIZE];
579        char *newpath, newbuffer[PATH_BUFFER_SIZE];
580        struct node *target;
581        struct node *newparent;
582        int res;
583
584        TRACE("RENAME %s->%s @ %llx\n", oldname, newname, hdr->nodeid);
585
586        target = lookup_child_by_name(node, oldname);
587        if (!target) {
588            fuse_status(fuse, hdr->unique, -ENOENT);
589            return;
590        }
591        oldpath = node_get_path(node, oldbuffer, oldname);
592
593        newparent = lookup_by_inode(fuse, req->newdir);
594        if (!newparent) {
595            fuse_status(fuse, hdr->unique, -ENOENT);
596            return;
597        }
598        newpath = node_get_path(newparent, newbuffer, newname);
599
600        if (!remove_child(node, target->nid)) {
601            ERROR("RENAME remove_child not found");
602            fuse_status(fuse, hdr->unique, -ENOENT);
603            return;
604        }
605        if (!rename_node(target, newname)) {
606            fuse_status(fuse, hdr->unique, -ENOMEM);
607            return;
608        }
609        add_node_to_parent(target, newparent);
610
611        res = rename(oldpath, newpath);
612        TRACE("RENAME result %d\n", res);
613
614        fuse_status(fuse, hdr->unique, res ? -errno : 0);
615        return;
616    }
617//    case FUSE_LINK:
618    case FUSE_OPEN: { /* open_in -> open_out */
619        struct fuse_open_in *req = data;
620        struct fuse_open_out out;
621        char *path, buffer[PATH_BUFFER_SIZE];
622        struct handle *h;
623
624        h = malloc(sizeof(*h));
625        if (!h) {
626            fuse_status(fuse, hdr->unique, -ENOMEM);
627            return;
628        }
629
630        path = node_get_path(node, buffer, 0);
631        TRACE("OPEN %llx '%s' 0%o fh=%p\n", hdr->nodeid, path, req->flags, h);
632        h->fd = open(path, req->flags);
633        if (h->fd < 0) {
634            ERROR("ERROR\n");
635            fuse_status(fuse, hdr->unique, errno);
636            free(h);
637            return;
638        }
639        out.fh = ptr_to_id(h);
640        out.open_flags = 0;
641        out.padding = 0;
642        fuse_reply(fuse, hdr->unique, &out, sizeof(out));
643        return;
644    }
645    case FUSE_READ: { /* read_in -> byte[] */
646        char buffer[128 * 1024];
647        struct fuse_read_in *req = data;
648        struct handle *h = id_to_ptr(req->fh);
649        int res;
650        TRACE("READ %p(%d) %u@%llu\n", h, h->fd, req->size, req->offset);
651        if (req->size > sizeof(buffer)) {
652            fuse_status(fuse, hdr->unique, -EINVAL);
653            return;
654        }
655        res = pread64(h->fd, buffer, req->size, req->offset);
656        if (res < 0) {
657            fuse_status(fuse, hdr->unique, errno);
658            return;
659        }
660        fuse_reply(fuse, hdr->unique, buffer, res);
661        return;
662    }
663    case FUSE_WRITE: { /* write_in, byte[write_in.size] -> write_out */
664        struct fuse_write_in *req = data;
665        struct fuse_write_out out;
666        struct handle *h = id_to_ptr(req->fh);
667        int res;
668        TRACE("WRITE %p(%d) %u@%llu\n", h, h->fd, req->size, req->offset);
669        res = pwrite64(h->fd, ((char*) data) + sizeof(*req), req->size, req->offset);
670        if (res < 0) {
671            fuse_status(fuse, hdr->unique, errno);
672            return;
673        }
674        out.size = res;
675        fuse_reply(fuse, hdr->unique, &out, sizeof(out));
676        goto oops;
677    }
678    case FUSE_STATFS: { /* getattr_in -> attr_out */
679        struct statfs stat;
680        struct fuse_statfs_out out;
681        int res;
682
683        TRACE("STATFS\n");
684
685        if (statfs(fuse->root.name, &stat)) {
686            fuse_status(fuse, hdr->unique, -errno);
687            return;
688        }
689
690        memset(&out, 0, sizeof(out));
691        out.st.blocks = stat.f_blocks;
692        out.st.bfree = stat.f_bfree;
693        out.st.bavail = stat.f_bavail;
694        out.st.files = stat.f_files;
695        out.st.ffree = stat.f_ffree;
696        out.st.bsize = stat.f_bsize;
697        out.st.namelen = stat.f_namelen;
698        out.st.frsize = stat.f_frsize;
699        fuse_reply(fuse, hdr->unique, &out, sizeof(out));
700        return;
701    }
702    case FUSE_RELEASE: { /* release_in -> */
703        struct fuse_release_in *req = data;
704        struct handle *h = id_to_ptr(req->fh);
705        TRACE("RELEASE %p(%d)\n", h, h->fd);
706        close(h->fd);
707        free(h);
708        fuse_status(fuse, hdr->unique, 0);
709        return;
710    }
711//    case FUSE_FSYNC:
712//    case FUSE_SETXATTR:
713//    case FUSE_GETXATTR:
714//    case FUSE_LISTXATTR:
715//    case FUSE_REMOVEXATTR:
716    case FUSE_FLUSH:
717        fuse_status(fuse, hdr->unique, 0);
718        return;
719    case FUSE_OPENDIR: { /* open_in -> open_out */
720        struct fuse_open_in *req = data;
721        struct fuse_open_out out;
722        char *path, buffer[PATH_BUFFER_SIZE];
723        struct dirhandle *h;
724
725        h = malloc(sizeof(*h));
726        if (!h) {
727            fuse_status(fuse, hdr->unique, -ENOMEM);
728            return;
729        }
730
731        path = node_get_path(node, buffer, 0);
732        TRACE("OPENDIR %llx '%s'\n", hdr->nodeid, path);
733        h->d = opendir(path);
734        if (h->d == 0) {
735            ERROR("ERROR\n");
736            fuse_status(fuse, hdr->unique, -errno);
737            free(h);
738            return;
739        }
740        out.fh = ptr_to_id(h);
741        fuse_reply(fuse, hdr->unique, &out, sizeof(out));
742        return;
743    }
744    case FUSE_READDIR: {
745        struct fuse_read_in *req = data;
746        char buffer[8192];
747        struct fuse_dirent *fde = (struct fuse_dirent*) buffer;
748        struct dirent *de;
749        struct dirhandle *h = id_to_ptr(req->fh);
750        TRACE("READDIR %p\n", h);
751        de = readdir(h->d);
752        if (!de) {
753            fuse_status(fuse, hdr->unique, 0);
754            return;
755        }
756        fde->ino = FUSE_UNKNOWN_INO;
757        fde->off = 0;
758        fde->type = de->d_type;
759        fde->namelen = strlen(de->d_name);
760        memcpy(fde->name, de->d_name, fde->namelen + 1);
761        fuse_reply(fuse, hdr->unique, fde,
762                   FUSE_DIRENT_ALIGN(sizeof(struct fuse_dirent) + fde->namelen));
763        return;
764    }
765    case FUSE_RELEASEDIR: { /* release_in -> */
766        struct fuse_release_in *req = data;
767        struct dirhandle *h = id_to_ptr(req->fh);
768        TRACE("RELEASEDIR %p\n",h);
769        closedir(h->d);
770        free(h);
771        fuse_status(fuse, hdr->unique, 0);
772        return;
773    }
774//    case FUSE_FSYNCDIR:
775    case FUSE_INIT: { /* init_in -> init_out */
776        struct fuse_init_in *req = data;
777        struct fuse_init_out out;
778
779        TRACE("INIT ver=%d.%d maxread=%d flags=%x\n",
780                req->major, req->minor, req->max_readahead, req->flags);
781
782        out.major = FUSE_KERNEL_VERSION;
783        out.minor = FUSE_KERNEL_MINOR_VERSION;
784        out.max_readahead = req->max_readahead;
785        out.flags = FUSE_ATOMIC_O_TRUNC;
786        out.max_background = 32;
787        out.congestion_threshold = 32;
788        out.max_write = 256 * 1024;
789
790        fuse_reply(fuse, hdr->unique, &out, sizeof(out));
791        return;
792    }
793    default: {
794        struct fuse_out_header h;
795        ERROR("NOTIMPL op=%d uniq=%llx nid=%llx\n",
796                hdr->opcode, hdr->unique, hdr->nodeid);
797
798        oops:
799        h.len = sizeof(h);
800        h.error = -ENOSYS;
801        h.unique = hdr->unique;
802        write(fuse->fd, &h, sizeof(h));
803        break;
804    }
805    }
806}
807
808void handle_fuse_requests(struct fuse *fuse)
809{
810    unsigned char req[256 * 1024 + 128];
811    int len;
812
813    for (;;) {
814        len = read(fuse->fd, req, 8192);
815        if (len < 0) {
816            if (errno == EINTR)
817                continue;
818            ERROR("handle_fuse_requests: errno=%d\n", errno);
819            return;
820        }
821        handle_fuse_request(fuse, (void*) req, (void*) (req + sizeof(struct fuse_in_header)), len);
822    }
823}
824
825int main(int argc, char **argv)
826{
827    struct fuse fuse;
828    char opts[256];
829    int fd;
830    int res;
831    unsigned uid;
832    unsigned gid;
833    const char *path;
834
835    if (argc != 4) {
836        ERROR("usage: sdcard <path> <uid> <gid>\n");
837        return -1;
838    }
839
840    uid = strtoul(argv[2], 0, 10);
841    gid = strtoul(argv[3], 0, 10);
842    if (!uid || !gid) {
843        ERROR("uid and gid must be nonzero\n");
844        return -1;
845    }
846
847    path = argv[1];
848
849        /* cleanup from previous instance, if necessary */
850    umount2(MOUNT_POINT, 2);
851
852    fd = open("/dev/fuse", O_RDWR);
853    if (fd < 0){
854        ERROR("cannot open fuse device (%d)\n", errno);
855        return -1;
856    }
857
858    sprintf(opts, "fd=%i,rootmode=40000,default_permissions,allow_other,"
859            "user_id=%d,group_id=%d", fd, uid, gid);
860
861    res = mount("/dev/fuse", MOUNT_POINT, "fuse", MS_NOSUID | MS_NODEV, opts);
862    if (res < 0) {
863        ERROR("cannot mount fuse filesystem (%d)\n", errno);
864        return -1;
865    }
866
867    if (setgid(gid) < 0) {
868        ERROR("cannot setgid!\n");
869        return -1;
870    }
871    if (setuid(uid) < 0) {
872        ERROR("cannot setuid!\n");
873        return -1;
874    }
875
876    fuse_init(&fuse, fd, path);
877
878    umask(0);
879    handle_fuse_requests(&fuse);
880
881    return 0;
882}
883