Merge branch 'master'
[linux-2.6] / arch / um / drivers / cow_user.c
1 #include <stddef.h>
2 #include <string.h>
3 #include <errno.h>
4 /* _XOPEN_SOURCE is needed for pread, but we define _GNU_SOURCE, which defines
5  * that.
6  */
7 #include <unistd.h>
8 #include <byteswap.h>
9 #include <sys/time.h>
10 #include <sys/param.h>
11 #include <sys/user.h>
12
13 #include "os.h"
14
15 #include "cow.h"
16 #include "cow_sys.h"
17
18 #define PATH_LEN_V1 256
19
20 typedef __u32 time32_t;
21
22 struct cow_header_v1 {
23         __s32 magic;
24         __s32 version;
25         char backing_file[PATH_LEN_V1];
26         time32_t mtime;
27         __u64 size;
28         __s32 sectorsize;
29 } __attribute__((packed));
30
31 /* Define PATH_LEN_V3 as the usual value of MAXPATHLEN, just hard-code it in
32  * case other systems have different values for MAXPATHLEN.
33  *
34  * The same must hold for V2 - we want file format compatibility, not anything
35  * else.
36  */
37 #define PATH_LEN_V3 4096
38 #define PATH_LEN_V2 PATH_LEN_V3
39
40 struct cow_header_v2 {
41         __u32 magic;
42         __u32 version;
43         char backing_file[PATH_LEN_V2];
44         time32_t mtime;
45         __u64 size;
46         __s32 sectorsize;
47 } __attribute__((packed));
48
49 /* Changes from V2 -
50  *      PATH_LEN_V3 as described above
51  *      Explicitly specify field bit lengths for systems with different
52  *              lengths for the usual C types.  Not sure whether char or
53  *              time_t should be changed, this can be changed later without
54  *              breaking compatibility
55  *      Add alignment field so that different alignments can be used for the
56  *              bitmap and data
57  *      Add cow_format field to allow for the possibility of different ways
58  *              of specifying the COW blocks.  For now, the only value is 0,
59  *              for the traditional COW bitmap.
60  *      Move the backing_file field to the end of the header.  This allows
61  *              for the possibility of expanding it into the padding required
62  *              by the bitmap alignment.
63  *      The bitmap and data portions of the file will be aligned as specified
64  *              by the alignment field.  This is to allow COW files to be
65  *              put on devices with restrictions on access alignments, such as
66  *              /dev/raw, with a 512 byte alignment restriction.  This also
67  *              allows the data to be more aligned more strictly than on
68  *              sector boundaries.  This is needed for ubd-mmap, which needs
69  *              the data to be page aligned.
70  *      Fixed (finally!) the rounding bug
71  */
72
73 /* Until Dec2005, __attribute__((packed)) was left out from the below
74  * definition, leading on 64-bit systems to 4 bytes of padding after mtime, to
75  * align size to 8-byte alignment.  This shifted all fields above (no padding
76  * was present on 32-bit, no other padding was added).
77  *
78  * However, this _can be detected_: it means that cow_format (always 0 until
79  * now) is shifted onto the first 4 bytes of backing_file, where it is otherwise
80  * impossible to find 4 zeros. -bb */
81
82 struct cow_header_v3 {
83         __u32 magic;
84         __u32 version;
85         __u32 mtime;
86         __u64 size;
87         __u32 sectorsize;
88         __u32 alignment;
89         __u32 cow_format;
90         char backing_file[PATH_LEN_V3];
91 } __attribute__((packed));
92
93 /* This is the broken layout used by some 64-bit binaries. */
94 struct cow_header_v3_broken {
95         __u32 magic;
96         __u32 version;
97         __s64 mtime;
98         __u64 size;
99         __u32 sectorsize;
100         __u32 alignment;
101         __u32 cow_format;
102         char backing_file[PATH_LEN_V3];
103 };
104
105 /* COW format definitions - for now, we have only the usual COW bitmap */
106 #define COW_BITMAP 0
107
108 union cow_header {
109         struct cow_header_v1 v1;
110         struct cow_header_v2 v2;
111         struct cow_header_v3 v3;
112         struct cow_header_v3_broken v3_b;
113 };
114
115 #define COW_MAGIC 0x4f4f4f4d  /* MOOO */
116 #define COW_VERSION 3
117
118 #define DIV_ROUND(x, len) (((x) + (len) - 1) / (len))
119 #define ROUND_UP(x, align) DIV_ROUND(x, align) * (align)
120
121 void cow_sizes(int version, __u64 size, int sectorsize, int align,
122                int bitmap_offset, unsigned long *bitmap_len_out,
123                int *data_offset_out)
124 {
125         if(version < 3){
126                 *bitmap_len_out = (size + sectorsize - 1) / (8 * sectorsize);
127
128                 *data_offset_out = bitmap_offset + *bitmap_len_out;
129                 *data_offset_out = (*data_offset_out + sectorsize - 1) /
130                         sectorsize;
131                 *data_offset_out *= sectorsize;
132         }
133         else {
134                 *bitmap_len_out = DIV_ROUND(size, sectorsize);
135                 *bitmap_len_out = DIV_ROUND(*bitmap_len_out, 8);
136
137                 *data_offset_out = bitmap_offset + *bitmap_len_out;
138                 *data_offset_out = ROUND_UP(*data_offset_out, align);
139         }
140 }
141
142 static int absolutize(char *to, int size, char *from)
143 {
144         char save_cwd[256], *slash;
145         int remaining;
146
147         if(getcwd(save_cwd, sizeof(save_cwd)) == NULL) {
148                 cow_printf("absolutize : unable to get cwd - errno = %d\n",
149                            errno);
150                 return(-1);
151         }
152         slash = strrchr(from, '/');
153         if(slash != NULL){
154                 *slash = '\0';
155                 if(chdir(from)){
156                         *slash = '/';
157                         cow_printf("absolutize : Can't cd to '%s' - "
158                                    "errno = %d\n", from, errno);
159                         return(-1);
160                 }
161                 *slash = '/';
162                 if(getcwd(to, size) == NULL){
163                         cow_printf("absolutize : unable to get cwd of '%s' - "
164                                "errno = %d\n", from, errno);
165                         return(-1);
166                 }
167                 remaining = size - strlen(to);
168                 if(strlen(slash) + 1 > remaining){
169                         cow_printf("absolutize : unable to fit '%s' into %d "
170                                "chars\n", from, size);
171                         return(-1);
172                 }
173                 strcat(to, slash);
174         }
175         else {
176                 if(strlen(save_cwd) + 1 + strlen(from) + 1 > size){
177                         cow_printf("absolutize : unable to fit '%s' into %d "
178                                "chars\n", from, size);
179                         return(-1);
180                 }
181                 strcpy(to, save_cwd);
182                 strcat(to, "/");
183                 strcat(to, from);
184         }
185         chdir(save_cwd);
186         return(0);
187 }
188
189 int write_cow_header(char *cow_file, int fd, char *backing_file,
190                      int sectorsize, int alignment, unsigned long long *size)
191 {
192         struct cow_header_v3 *header;
193         unsigned long modtime;
194         int err;
195
196         err = cow_seek_file(fd, 0);
197         if(err < 0){
198                 cow_printf("write_cow_header - lseek failed, err = %d\n", -err);
199                 goto out;
200         }
201
202         err = -ENOMEM;
203         header = cow_malloc(sizeof(*header));
204         if(header == NULL){
205                 cow_printf("write_cow_header - failed to allocate COW V3 header\n");
206                 goto out;
207         }
208         header->magic = htonl(COW_MAGIC);
209         header->version = htonl(COW_VERSION);
210
211         err = -EINVAL;
212         if(strlen(backing_file) > sizeof(header->backing_file) - 1){
213                 /* Below, %zd is for a size_t value */
214                 cow_printf("Backing file name \"%s\" is too long - names are "
215                            "limited to %zd characters\n", backing_file,
216                            sizeof(header->backing_file) - 1);
217                 goto out_free;
218         }
219
220         if(absolutize(header->backing_file, sizeof(header->backing_file),
221                       backing_file))
222                 goto out_free;
223
224         err = os_file_modtime(header->backing_file, &modtime);
225         if(err < 0){
226                 cow_printf("write_cow_header - backing file '%s' mtime "
227                            "request failed, err = %d\n", header->backing_file,
228                            -err);
229                 goto out_free;
230         }
231
232         err = cow_file_size(header->backing_file, size);
233         if(err < 0){
234                 cow_printf("write_cow_header - couldn't get size of "
235                            "backing file '%s', err = %d\n",
236                            header->backing_file, -err);
237                 goto out_free;
238         }
239
240         header->mtime = htonl(modtime);
241         header->size = htonll(*size);
242         header->sectorsize = htonl(sectorsize);
243         header->alignment = htonl(alignment);
244         header->cow_format = COW_BITMAP;
245
246         err = cow_write_file(fd, header, sizeof(*header));
247         if(err != sizeof(*header)){
248                 cow_printf("write_cow_header - write of header to "
249                            "new COW file '%s' failed, err = %d\n", cow_file,
250                            -err);
251                 goto out_free;
252         }
253         err = 0;
254  out_free:
255         cow_free(header);
256  out:
257         return(err);
258 }
259
260 int file_reader(__u64 offset, char *buf, int len, void *arg)
261 {
262         int fd = *((int *) arg);
263
264         return(pread(fd, buf, len, offset));
265 }
266
267 /* XXX Need to sanity-check the values read from the header */
268
269 int read_cow_header(int (*reader)(__u64, char *, int, void *), void *arg,
270                     __u32 *version_out, char **backing_file_out,
271                     time_t *mtime_out, unsigned long long *size_out,
272                     int *sectorsize_out, __u32 *align_out,
273                     int *bitmap_offset_out)
274 {
275         union cow_header *header;
276         char *file;
277         int err, n;
278         unsigned long version, magic;
279
280         header = cow_malloc(sizeof(*header));
281         if(header == NULL){
282                 cow_printf("read_cow_header - Failed to allocate header\n");
283                 return(-ENOMEM);
284         }
285         err = -EINVAL;
286         n = (*reader)(0, (char *) header, sizeof(*header), arg);
287         if(n < offsetof(typeof(header->v1), backing_file)){
288                 cow_printf("read_cow_header - short header\n");
289                 goto out;
290         }
291
292         magic = header->v1.magic;
293         if(magic == COW_MAGIC) {
294                 version = header->v1.version;
295         }
296         else if(magic == ntohl(COW_MAGIC)){
297                 version = ntohl(header->v1.version);
298         }
299         /* No error printed because the non-COW case comes through here */
300         else goto out;
301
302         *version_out = version;
303
304         if(version == 1){
305                 if(n < sizeof(header->v1)){
306                         cow_printf("read_cow_header - failed to read V1 "
307                                    "header\n");
308                         goto out;
309                 }
310                 *mtime_out = header->v1.mtime;
311                 *size_out = header->v1.size;
312                 *sectorsize_out = header->v1.sectorsize;
313                 *bitmap_offset_out = sizeof(header->v1);
314                 *align_out = *sectorsize_out;
315                 file = header->v1.backing_file;
316         }
317         else if(version == 2){
318                 if(n < sizeof(header->v2)){
319                         cow_printf("read_cow_header - failed to read V2 "
320                                    "header\n");
321                         goto out;
322                 }
323                 *mtime_out = ntohl(header->v2.mtime);
324                 *size_out = ntohll(header->v2.size);
325                 *sectorsize_out = ntohl(header->v2.sectorsize);
326                 *bitmap_offset_out = sizeof(header->v2);
327                 *align_out = *sectorsize_out;
328                 file = header->v2.backing_file;
329         }
330         /* This is very subtle - see above at union cow_header definition */
331         else if(version == 3 && (*((int*)header->v3.backing_file) != 0)){
332                 if(n < sizeof(header->v3)){
333                         cow_printf("read_cow_header - failed to read V3 "
334                                    "header\n");
335                         goto out;
336                 }
337                 *mtime_out = ntohl(header->v3.mtime);
338                 *size_out = ntohll(header->v3.size);
339                 *sectorsize_out = ntohl(header->v3.sectorsize);
340                 *align_out = ntohl(header->v3.alignment);
341                 if (*align_out == 0) {
342                         cow_printf("read_cow_header - invalid COW header, "
343                                    "align == 0\n");
344                 }
345                 *bitmap_offset_out = ROUND_UP(sizeof(header->v3), *align_out);
346                 file = header->v3.backing_file;
347         }
348         else if(version == 3){
349                 cow_printf("read_cow_header - broken V3 file with"
350                            " 64-bit layout - recovering content.\n");
351
352                 if(n < sizeof(header->v3_b)){
353                         cow_printf("read_cow_header - failed to read V3 "
354                                    "header\n");
355                         goto out;
356                 }
357
358                 /* this was used until Dec2005 - 64bits are needed to represent
359                  * 2038+. I.e. we can safely do this truncating cast.
360                  *
361                  * Additionally, we must use ntohl() instead of ntohll(), since
362                  * the program used to use the former (tested - I got mtime
363                  * mismatch "0 vs whatever").
364                  *
365                  * Ever heard about bug-to-bug-compatibility ? ;-) */
366                 *mtime_out = (time32_t) ntohl(header->v3_b.mtime);
367
368                 *size_out = ntohll(header->v3_b.size);
369                 *sectorsize_out = ntohl(header->v3_b.sectorsize);
370                 *align_out = ntohl(header->v3_b.alignment);
371                 if (*align_out == 0) {
372                         cow_printf("read_cow_header - invalid COW header, "
373                                    "align == 0\n");
374                 }
375                 *bitmap_offset_out = ROUND_UP(sizeof(header->v3_b), *align_out);
376                 file = header->v3_b.backing_file;
377         }
378         else {
379                 cow_printf("read_cow_header - invalid COW version\n");
380                 goto out;
381         }
382         err = -ENOMEM;
383         *backing_file_out = cow_strdup(file);
384         if(*backing_file_out == NULL){
385                 cow_printf("read_cow_header - failed to allocate backing "
386                            "file\n");
387                 goto out;
388         }
389         err = 0;
390  out:
391         cow_free(header);
392         return(err);
393 }
394
395 int init_cow_file(int fd, char *cow_file, char *backing_file, int sectorsize,
396                   int alignment, int *bitmap_offset_out,
397                   unsigned long *bitmap_len_out, int *data_offset_out)
398 {
399         unsigned long long size, offset;
400         char zero = 0;
401         int err;
402
403         err = write_cow_header(cow_file, fd, backing_file, sectorsize,
404                                alignment, &size);
405         if(err)
406                 goto out;
407
408         *bitmap_offset_out = ROUND_UP(sizeof(struct cow_header_v3), alignment);
409         cow_sizes(COW_VERSION, size, sectorsize, alignment, *bitmap_offset_out,
410                   bitmap_len_out, data_offset_out);
411
412         offset = *data_offset_out + size - sizeof(zero);
413         err = cow_seek_file(fd, offset);
414         if(err < 0){
415                 cow_printf("cow bitmap lseek failed : err = %d\n", -err);
416                 goto out;
417         }
418
419         /* does not really matter how much we write it is just to set EOF
420          * this also sets the entire COW bitmap
421          * to zero without having to allocate it
422          */
423         err = cow_write_file(fd, &zero, sizeof(zero));
424         if(err != sizeof(zero)){
425                 cow_printf("Write of bitmap to new COW file '%s' failed, "
426                            "err = %d\n", cow_file, -err);
427                 if (err >= 0)
428                         err = -EINVAL;
429                 goto out;
430         }
431
432         return(0);
433
434  out:
435         return(err);
436 }
437
438 /*
439  * ---------------------------------------------------------------------------
440  * Local variables:
441  * c-file-style: "linux"
442  * End:
443  */