sdcard.c revision 11ccdb3be67b22f677065715ace68aabf371acc7 
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}
199
200struct node *node_create(struct node *parent, const char *name, __u64 nid, __u64 gen)
201{
202    struct node *node;
203    int namelen = strlen(name);
204
205    node = calloc(1, sizeof(struct node));
206    if (node == 0) {
207        return 0;
208    }
209    node->name = malloc(namelen + 1);
210    if (node->name == 0) {
211        free(node);
212        return 0;
213    }
214
215    node->nid = nid;
216    node->gen = gen;
217    add_node_to_parent(node, parent);
218    memcpy(node->name, name, namelen + 1);
219    node->namelen = namelen;
220    parent->refcount++;
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 struct node *remove_child(struct node *parent, __u64 nid)
297{
298    struct node *prev = 0;
299    struct node *node;
300
301    for (node = parent->child; node; node = node->next) {
302        if (node->nid == nid) {
303            if (prev) {
304                prev->next = node->next;
305            } else {
306                parent->child = node->next;
307            }
308            node->next = 0;
309            node->parent = 0;
310            return node;
311        }
312        prev = node;
313    }
314    return 0;
315}
316
317struct node *node_lookup(struct fuse *fuse, struct node *parent, const char *name,
318                         struct fuse_attr *attr)
319{
320    int res;
321    struct stat s;
322    char *path, buffer[PATH_BUFFER_SIZE];
323    struct node *node;
324
325    path = node_get_path(parent, buffer, name);
326        /* XXX error? */
327
328    res = lstat(path, &s);
329    if (res < 0)
330        return 0;
331
332    node = lookup_child_by_name(parent, name);
333    if (!node) {
334        node = node_create(parent, name, fuse->next_node_id++, fuse->next_generation++);
335        if (!node)
336            return 0;
337        node->nid = ptr_to_id(node);
338        node->all = fuse->all;
339        fuse->all = node;
340    }
341
342    attr_from_stat(attr, &s);
343    attr->ino = node->nid;
344
345    return node;
346}
347
348void node_release(struct node *node)
349{
350    TRACE("RELEASE %p (%s) rc=%d\n", node, node->name, node->refcount);
351    node->refcount--;
352    if (node->refcount == 0) {
353        if (node->parent->child == node) {
354            node->parent->child = node->parent->child->next;
355        } else {
356            struct node *node2;
357
358            node2 = node->parent->child;
359            while (node2->next != node)
360                node2 = node2->next;
361            node2->next = node->next;
362        }
363
364        TRACE("DESTROY %p (%s)\n", node, node->name);
365
366        node_release(node->parent);
367
368        node->parent = 0;
369        node->next = 0;
370
371            /* TODO: remove debugging - poison memory */
372        memset(node->name, 0xef, node->namelen);
373        free(node->name);
374        memset(node, 0xef, sizeof(*node));
375        free(node);
376    }
377}
378
379void fuse_status(struct fuse *fuse, __u64 unique, int err)
380{
381    struct fuse_out_header hdr;
382    hdr.len = sizeof(hdr);
383    hdr.error = err;
384    hdr.unique = unique;
385    if (err) {
386//        ERROR("*** %d ***\n", err);
387    }
388    write(fuse->fd, &hdr, sizeof(hdr));
389}
390
391void fuse_reply(struct fuse *fuse, __u64 unique, void *data, int len)
392{
393    struct fuse_out_header hdr;
394    struct iovec vec[2];
395    int res;
396
397    hdr.len = len + sizeof(hdr);
398    hdr.error = 0;
399    hdr.unique = unique;
400
401    vec[0].iov_base = &hdr;
402    vec[0].iov_len = sizeof(hdr);
403    vec[1].iov_base = data;
404    vec[1].iov_len = len;
405
406    res = writev(fuse->fd, vec, 2);
407    if (res < 0) {
408        ERROR("*** REPLY FAILED *** %d\n", errno);
409    }
410}
411
412void lookup_entry(struct fuse *fuse, struct node *node,
413                  const char *name, __u64 unique)
414{
415    struct fuse_entry_out out;
416
417    memset(&out, 0, sizeof(out));
418
419    node = node_lookup(fuse, node, name, &out.attr);
420    if (!node) {
421        fuse_status(fuse, unique, -ENOENT);
422        return;
423    }
424
425    node->refcount++;
426//    fprintf(stderr,"ACQUIRE %p (%s) rc=%d\n", node, node->name, node->refcount);
427    out.nodeid = node->nid;
428    out.generation = node->gen;
429    out.entry_valid = 10;
430    out.attr_valid = 10;
431
432    fuse_reply(fuse, unique, &out, sizeof(out));
433}
434
435void handle_fuse_request(struct fuse *fuse, struct fuse_in_header *hdr, void *data, unsigned len)
436{
437    struct node *node;
438
439    if ((len < sizeof(*hdr)) || (hdr->len != len)) {
440        ERROR("malformed header\n");
441        return;
442    }
443
444    len -= hdr->len;
445
446    if (hdr->nodeid) {
447        node = lookup_by_inode(fuse, hdr->nodeid);
448        if (!node) {
449            fuse_status(fuse, hdr->unique, -ENOENT);
450            return;
451        }
452    } else {
453        node = 0;
454    }
455
456    switch (hdr->opcode) {
457    case FUSE_LOOKUP: { /* bytez[] -> entry_out */
458        TRACE("LOOKUP %llx %s\n", hdr->nodeid, (char*) data);
459        lookup_entry(fuse, node, (char*) data, hdr->unique);
460        return;
461    }
462    case FUSE_FORGET: {
463        struct fuse_forget_in *req = data;
464        TRACE("FORGET %llx (%s) #%lld\n", hdr->nodeid, node->name, req->nlookup);
465            /* no reply */
466        while (req->nlookup--)
467            node_release(node);
468        return;
469    }
470    case FUSE_GETATTR: { /* getattr_in -> attr_out */
471        struct fuse_getattr_in *req = data;
472        struct fuse_attr_out out;
473
474        TRACE("GETATTR flags=%x fh=%llx\n", req->getattr_flags, req->fh);
475
476        memset(&out, 0, sizeof(out));
477        node_get_attr(node, &out.attr);
478        out.attr_valid = 10;
479
480        fuse_reply(fuse, hdr->unique, &out, sizeof(out));
481        return;
482    }
483    case FUSE_SETATTR: { /* setattr_in -> attr_out */
484        struct fuse_setattr_in *req = data;
485        struct fuse_attr_out out;
486        char *path, buffer[PATH_BUFFER_SIZE];
487        int res = 0;
488
489        TRACE("SETATTR fh=%llx id=%llx valid=%x\n",
490              req->fh, hdr->nodeid, req->valid);
491
492        /* XXX: incomplete implementation -- truncate only.  chmod/chown
493         * should NEVER be implemented. */
494
495        path = node_get_path(node, buffer, 0);
496        if (req->valid & FATTR_SIZE)
497            res = truncate(path, req->size);
498
499        memset(&out, 0, sizeof(out));
500        node_get_attr(node, &out.attr);
501        out.attr_valid = 10;
502
503        if (res)
504            fuse_status(fuse, hdr->unique, -errno);
505        else
506            fuse_reply(fuse, hdr->unique, &out, sizeof(out));
507        return;
508    }
509//    case FUSE_READLINK:
510//    case FUSE_SYMLINK:
511    case FUSE_MKNOD: { /* mknod_in, bytez[] -> entry_out */
512        struct fuse_mknod_in *req = data;
513        char *path, buffer[PATH_BUFFER_SIZE];
514        char *name = ((char*) data) + sizeof(*req);
515        int res;
516        TRACE("MKNOD %s @ %llx\n", name, hdr->nodeid);
517        path = node_get_path(node, buffer, name);
518
519        req->mode = (req->mode & (~0777)) | 0664;
520        res = mknod(path, req->mode, req->rdev); /* XXX perm?*/
521        if (res < 0) {
522            fuse_status(fuse, hdr->unique, -errno);
523        } else {
524            lookup_entry(fuse, node, name, hdr->unique);
525        }
526        return;
527    }
528    case FUSE_MKDIR: { /* mkdir_in, bytez[] -> entry_out */
529        struct fuse_mkdir_in *req = data;
530        struct fuse_entry_out out;
531        char *path, buffer[PATH_BUFFER_SIZE];
532        char *name = ((char*) data) + sizeof(*req);
533        int res;
534        TRACE("MKDIR %s @ %llx 0%o\n", name, hdr->nodeid, req->mode);
535        path = node_get_path(node, buffer, name);
536
537        req->mode = (req->mode & (~0777)) | 0775;
538        res = mkdir(path, req->mode);
539        if (res < 0) {
540            fuse_status(fuse, hdr->unique, -errno);
541        } else {
542            lookup_entry(fuse, node, name, hdr->unique);
543        }
544        return;
545    }
546    case FUSE_UNLINK: { /* bytez[] -> */
547        char *path, buffer[PATH_BUFFER_SIZE];
548        int res;
549        TRACE("UNLINK %s @ %llx\n", (char*) data, hdr->nodeid);
550        path = node_get_path(node, buffer, (char*) data);
551        res = unlink(path);
552        fuse_status(fuse, hdr->unique, res ? -errno : 0);
553        return;
554    }
555    case FUSE_RMDIR: { /* bytez[] -> */
556        char *path, buffer[PATH_BUFFER_SIZE];
557        int res;
558        TRACE("RMDIR %s @ %llx\n", (char*) data, hdr->nodeid);
559        path = node_get_path(node, buffer, (char*) data);
560        res = rmdir(path);
561        fuse_status(fuse, hdr->unique, res ? -errno : 0);
562        return;
563    }
564    case FUSE_RENAME: { /* rename_in, oldname, newname ->  */
565        struct fuse_rename_in *req = data;
566        char *oldname = ((char*) data) + sizeof(*req);
567        char *newname = oldname + strlen(oldname) + 1;
568        char *oldpath, oldbuffer[PATH_BUFFER_SIZE];
569        char *newpath, newbuffer[PATH_BUFFER_SIZE];
570        struct node *target;
571        struct node *newparent;
572        int res;
573
574        TRACE("RENAME %s->%s @ %llx\n", oldname, newname, hdr->nodeid);
575
576        target = lookup_child_by_name(node, oldname);
577        if (!target) {
578            fuse_status(fuse, hdr->unique, -ENOENT);
579            return;
580        }
581        oldpath = node_get_path(node, oldbuffer, oldname);
582
583        newparent = lookup_by_inode(fuse, req->newdir);
584        if (!newparent) {
585            fuse_status(fuse, hdr->unique, -ENOENT);
586            return;
587        }
588        newpath = node_get_path(newparent, newbuffer, newname);
589
590        if (!remove_child(node, target->nid)) {
591            ERROR("RENAME remove_child not found");
592            fuse_status(fuse, hdr->unique, -ENOENT);
593            return;
594        }
595        if (!rename_node(target, newname)) {
596            fuse_status(fuse, hdr->unique, -ENOMEM);
597            return;
598        }
599        add_node_to_parent(target, newparent);
600
601        res = rename(oldpath, newpath);
602        TRACE("RENAME result %d\n", res);
603
604        fuse_status(fuse, hdr->unique, res ? -errno : 0);
605        return;
606    }
607//    case FUSE_LINK:
608    case FUSE_OPEN: { /* open_in -> open_out */
609        struct fuse_open_in *req = data;
610        struct fuse_open_out out;
611        char *path, buffer[PATH_BUFFER_SIZE];
612        struct handle *h;
613
614        h = malloc(sizeof(*h));
615        if (!h) {
616            fuse_status(fuse, hdr->unique, -ENOMEM);
617            return;
618        }
619
620        path = node_get_path(node, buffer, 0);
621        TRACE("OPEN %llx '%s' 0%o fh=%p\n", hdr->nodeid, path, req->flags, h);
622        h->fd = open(path, req->flags);
623        if (h->fd < 0) {
624            ERROR("ERROR\n");
625            fuse_status(fuse, hdr->unique, errno);
626            free(h);
627            return;
628        }
629        out.fh = ptr_to_id(h);
630        out.open_flags = 0;
631        out.padding = 0;
632        fuse_reply(fuse, hdr->unique, &out, sizeof(out));
633        return;
634    }
635    case FUSE_READ: { /* read_in -> byte[] */
636        char buffer[128 * 1024];
637        struct fuse_read_in *req = data;
638        struct handle *h = id_to_ptr(req->fh);
639        int res;
640        TRACE("READ %p(%d) %u@%llu\n", h, h->fd, req->size, req->offset);
641        if (req->size > sizeof(buffer)) {
642            fuse_status(fuse, hdr->unique, -EINVAL);
643            return;
644        }
645        res = pread(h->fd, buffer, req->size, req->offset);
646        if (res < 0) {
647            fuse_status(fuse, hdr->unique, errno);
648            return;
649        }
650        fuse_reply(fuse, hdr->unique, buffer, res);
651        return;
652    }
653    case FUSE_WRITE: { /* write_in, byte[write_in.size] -> write_out */
654        struct fuse_write_in *req = data;
655        struct fuse_write_out out;
656        struct handle *h = id_to_ptr(req->fh);
657        int res;
658        TRACE("WRITE %p(%d) %u@%llu\n", h, h->fd, req->size, req->offset);
659        res = pwrite(h->fd, ((char*) data) + sizeof(*req), req->size, req->offset);
660        if (res < 0) {
661            fuse_status(fuse, hdr->unique, errno);
662            return;
663        }
664        out.size = res;
665        fuse_reply(fuse, hdr->unique, &out, sizeof(out));
666        goto oops;
667    }
668    case FUSE_STATFS: { /* getattr_in -> attr_out */
669        struct statfs stat;
670        struct fuse_statfs_out out;
671        int res;
672
673        TRACE("STATFS\n");
674
675        if (statfs(fuse->root.name, &stat)) {
676            fuse_status(fuse, hdr->unique, -errno);
677            return;
678        }
679
680        memset(&out, 0, sizeof(out));
681        out.st.blocks = stat.f_blocks;
682        out.st.bfree = stat.f_bfree;
683        out.st.bavail = stat.f_bavail;
684        out.st.files = stat.f_files;
685        out.st.ffree = stat.f_ffree;
686        out.st.bsize = stat.f_bsize;
687        out.st.namelen = stat.f_namelen;
688        out.st.frsize = stat.f_frsize;
689        fuse_reply(fuse, hdr->unique, &out, sizeof(out));
690        return;
691    }
692    case FUSE_RELEASE: { /* release_in -> */
693        struct fuse_release_in *req = data;
694        struct handle *h = id_to_ptr(req->fh);
695        TRACE("RELEASE %p(%d)\n", h, h->fd);
696        close(h->fd);
697        free(h);
698        fuse_status(fuse, hdr->unique, 0);
699        return;
700    }
701//    case FUSE_FSYNC:
702//    case FUSE_SETXATTR:
703//    case FUSE_GETXATTR:
704//    case FUSE_LISTXATTR:
705//    case FUSE_REMOVEXATTR:
706    case FUSE_FLUSH:
707        fuse_status(fuse, hdr->unique, 0);
708        return;
709    case FUSE_OPENDIR: { /* open_in -> open_out */
710        struct fuse_open_in *req = data;
711        struct fuse_open_out out;
712        char *path, buffer[PATH_BUFFER_SIZE];
713        struct dirhandle *h;
714
715        h = malloc(sizeof(*h));
716        if (!h) {
717            fuse_status(fuse, hdr->unique, -ENOMEM);
718            return;
719        }
720
721        path = node_get_path(node, buffer, 0);
722        TRACE("OPENDIR %llx '%s'\n", hdr->nodeid, path);
723        h->d = opendir(path);
724        if (h->d == 0) {
725            ERROR("ERROR\n");
726            fuse_status(fuse, hdr->unique, -errno);
727            free(h);
728            return;
729        }
730        out.fh = ptr_to_id(h);
731        fuse_reply(fuse, hdr->unique, &out, sizeof(out));
732        return;
733    }
734    case FUSE_READDIR: {
735        struct fuse_read_in *req = data;
736        char buffer[8192];
737        struct fuse_dirent *fde = (struct fuse_dirent*) buffer;
738        struct dirent *de;
739        struct dirhandle *h = id_to_ptr(req->fh);
740        TRACE("READDIR %p\n", h);
741        de = readdir(h->d);
742        if (!de) {
743            fuse_status(fuse, hdr->unique, 0);
744            return;
745        }
746        fde->ino = FUSE_UNKNOWN_INO;
747        fde->off = 0;
748        fde->type = de->d_type;
749        fde->namelen = strlen(de->d_name);
750        memcpy(fde->name, de->d_name, fde->namelen + 1);
751        fuse_reply(fuse, hdr->unique, fde,
752                   FUSE_DIRENT_ALIGN(sizeof(struct fuse_dirent) + fde->namelen));
753        return;
754    }
755    case FUSE_RELEASEDIR: { /* release_in -> */
756        struct fuse_release_in *req = data;
757        struct dirhandle *h = id_to_ptr(req->fh);
758        TRACE("RELEASEDIR %p\n",h);
759        closedir(h->d);
760        free(h);
761        fuse_status(fuse, hdr->unique, 0);
762        return;
763    }
764//    case FUSE_FSYNCDIR:
765    case FUSE_INIT: { /* init_in -> init_out */
766        struct fuse_init_in *req = data;
767        struct fuse_init_out out;
768
769        TRACE("INIT ver=%d.%d maxread=%d flags=%x\n",
770                req->major, req->minor, req->max_readahead, req->flags);
771
772        out.major = FUSE_KERNEL_VERSION;
773        out.minor = FUSE_KERNEL_MINOR_VERSION;
774        out.max_readahead = req->max_readahead;
775        out.flags = FUSE_ATOMIC_O_TRUNC;
776        out.max_background = 32;
777        out.congestion_threshold = 32;
778        out.max_write = 256 * 1024;
779
780        fuse_reply(fuse, hdr->unique, &out, sizeof(out));
781        return;
782    }
783    default: {
784        struct fuse_out_header h;
785        ERROR("NOTIMPL op=%d uniq=%llx nid=%llx\n",
786                hdr->opcode, hdr->unique, hdr->nodeid);
787
788        oops:
789        h.len = sizeof(h);
790        h.error = -ENOSYS;
791        h.unique = hdr->unique;
792        write(fuse->fd, &h, sizeof(h));
793        break;
794    }
795    }
796}
797
798void handle_fuse_requests(struct fuse *fuse)
799{
800    unsigned char req[256 * 1024 + 128];
801    int len;
802
803    for (;;) {
804        len = read(fuse->fd, req, 8192);
805        if (len < 0) {
806            if (errno == EINTR)
807                continue;
808            ERROR("handle_fuse_requests: errno=%d\n", errno);
809            return;
810        }
811        handle_fuse_request(fuse, (void*) req, (void*) (req + sizeof(struct fuse_in_header)), len);
812    }
813}
814
815int main(int argc, char **argv)
816{
817    struct fuse fuse;
818    char opts[256];
819    int fd;
820    int res;
821    unsigned uid;
822    unsigned gid;
823    const char *path;
824
825    if (argc != 4) {
826        ERROR("usage: sdcard <path> <uid> <gid>\n");
827        return -1;
828    }
829
830    uid = strtoul(argv[2], 0, 10);
831    gid = strtoul(argv[3], 0, 10);
832    if (!uid || !gid) {
833        ERROR("uid and gid must be nonzero\n");
834        return -1;
835    }
836
837    path = argv[1];
838
839        /* cleanup from previous instance, if necessary */
840    umount2(MOUNT_POINT, 2);
841
842    fd = open("/dev/fuse", O_RDWR);
843    if (fd < 0){
844        ERROR("cannot open fuse device (%d)\n", errno);
845        return -1;
846    }
847
848    sprintf(opts, "fd=%i,rootmode=40000,default_permissions,allow_other,"
849            "user_id=%d,group_id=%d", fd, uid, gid);
850
851    res = mount("/dev/fuse", MOUNT_POINT, "fuse", MS_NOSUID | MS_NODEV, opts);
852    if (res < 0) {
853        ERROR("cannot mount fuse filesystem (%d)\n", errno);
854        return -1;
855    }
856
857    if (setgid(gid) < 0) {
858        ERROR("cannot setgid!\n");
859        return -1;
860    }
861    if (setuid(uid) < 0) {
862        ERROR("cannot setuid!\n");
863        return -1;
864    }
865
866    fuse_init(&fuse, fd, path);
867
868    umask(0);
869    handle_fuse_requests(&fuse);
870
871    return 0;
872}
873