1 /*
2 * Copyright (C) 2007 Jeff Dike (jdike@{linux.intel,addtoit}.com)
3 * Licensed under the GPL
4 */
5
6 /*
7 * _XOPEN_SOURCE is needed for pread, but we define _GNU_SOURCE, which defines
8 * that.
9 */
10 #include <unistd.h>
11 #include <byteswap.h>
12 #include <errno.h>
13 #include <string.h>
14 #include <arpa/inet.h>
15 #include <asm/types.h>
16 #include "cow.h"
17 #include "cow_sys.h"
18
19 #define PATH_LEN_V1 256
20
21 typedef __u32 time32_t;
22
23 struct cow_header_v1 {
24 __s32 magic;
25 __s32 version;
26 char backing_file[PATH_LEN_V1];
27 time32_t mtime;
28 __u64 size;
29 __s32 sectorsize;
30 } __attribute__((packed));
31
32 /*
33 * Define PATH_LEN_V3 as the usual value of MAXPATHLEN, just hard-code it in
34 * case other systems have different values for MAXPATHLEN.
35 *
36 * The same must hold for V2 - we want file format compatibility, not anything
37 * else.
38 */
39 #define PATH_LEN_V3 4096
40 #define PATH_LEN_V2 PATH_LEN_V3
41
42 struct cow_header_v2 {
43 __u32 magic;
44 __u32 version;
45 char backing_file[PATH_LEN_V2];
46 time32_t mtime;
47 __u64 size;
48 __s32 sectorsize;
49 } __attribute__((packed));
50
51 /*
52 * Changes from V2 -
53 * PATH_LEN_V3 as described above
54 * Explicitly specify field bit lengths for systems with different
55 * lengths for the usual C types. Not sure whether char or
56 * time_t should be changed, this can be changed later without
57 * breaking compatibility
58 * Add alignment field so that different alignments can be used for the
59 * bitmap and data
60 * Add cow_format field to allow for the possibility of different ways
61 * of specifying the COW blocks. For now, the only value is 0,
62 * for the traditional COW bitmap.
63 * Move the backing_file field to the end of the header. This allows
64 * for the possibility of expanding it into the padding required
65 * by the bitmap alignment.
66 * The bitmap and data portions of the file will be aligned as specified
67 * by the alignment field. This is to allow COW files to be
68 * put on devices with restrictions on access alignments, such as
69 * /dev/raw, with a 512 byte alignment restriction. This also
70 * allows the data to be more aligned more strictly than on
71 * sector boundaries. This is needed for ubd-mmap, which needs
72 * the data to be page aligned.
73 * Fixed (finally!) the rounding bug
74 */
75
76 /*
77 * Until Dec2005, __attribute__((packed)) was left out from the below
78 * definition, leading on 64-bit systems to 4 bytes of padding after mtime, to
79 * align size to 8-byte alignment. This shifted all fields above (no padding
80 * was present on 32-bit, no other padding was added).
81 *
82 * However, this _can be detected_: it means that cow_format (always 0 until
83 * now) is shifted onto the first 4 bytes of backing_file, where it is otherwise
84 * impossible to find 4 zeros. -bb */
85
86 struct cow_header_v3 {
87 __u32 magic;
88 __u32 version;
89 __u32 mtime;
90 __u64 size;
91 __u32 sectorsize;
92 __u32 alignment;
93 __u32 cow_format;
94 char backing_file[PATH_LEN_V3];
95 } __attribute__((packed));
96
97 /* This is the broken layout used by some 64-bit binaries. */
98 struct cow_header_v3_broken {
99 __u32 magic;
100 __u32 version;
101 __s64 mtime;
102 __u64 size;
103 __u32 sectorsize;
104 __u32 alignment;
105 __u32 cow_format;
106 char backing_file[PATH_LEN_V3];
107 };
108
109 /* COW format definitions - for now, we have only the usual COW bitmap */
110 #define COW_BITMAP 0
111
112 union cow_header {
113 struct cow_header_v1 v1;
114 struct cow_header_v2 v2;
115 struct cow_header_v3 v3;
116 struct cow_header_v3_broken v3_b;
117 };
118
119 #define COW_MAGIC 0x4f4f4f4d /* MOOO */
120 #define COW_VERSION 3
121
122 #define DIV_ROUND(x, len) (((x) + (len) - 1) / (len))
123 #define ROUND_UP(x, align) DIV_ROUND(x, align) * (align)
124
cow_sizes(int version,__u64 size,int sectorsize,int align,int bitmap_offset,unsigned long * bitmap_len_out,int * data_offset_out)125 void cow_sizes(int version, __u64 size, int sectorsize, int align,
126 int bitmap_offset, unsigned long *bitmap_len_out,
127 int *data_offset_out)
128 {
129 if (version < 3) {
130 *bitmap_len_out = (size + sectorsize - 1) / (8 * sectorsize);
131
132 *data_offset_out = bitmap_offset + *bitmap_len_out;
133 *data_offset_out = (*data_offset_out + sectorsize - 1) /
134 sectorsize;
135 *data_offset_out *= sectorsize;
136 }
137 else {
138 *bitmap_len_out = DIV_ROUND(size, sectorsize);
139 *bitmap_len_out = DIV_ROUND(*bitmap_len_out, 8);
140
141 *data_offset_out = bitmap_offset + *bitmap_len_out;
142 *data_offset_out = ROUND_UP(*data_offset_out, align);
143 }
144 }
145
absolutize(char * to,int size,char * from)146 static int absolutize(char *to, int size, char *from)
147 {
148 char save_cwd[256], *slash;
149 int remaining;
150
151 if (getcwd(save_cwd, sizeof(save_cwd)) == NULL) {
152 cow_printf("absolutize : unable to get cwd - errno = %d\n",
153 errno);
154 return -1;
155 }
156 slash = strrchr(from, '/');
157 if (slash != NULL) {
158 *slash = '\0';
159 if (chdir(from)) {
160 *slash = '/';
161 cow_printf("absolutize : Can't cd to '%s' - "
162 "errno = %d\n", from, errno);
163 return -1;
164 }
165 *slash = '/';
166 if (getcwd(to, size) == NULL) {
167 cow_printf("absolutize : unable to get cwd of '%s' - "
168 "errno = %d\n", from, errno);
169 return -1;
170 }
171 remaining = size - strlen(to);
172 if (strlen(slash) + 1 > remaining) {
173 cow_printf("absolutize : unable to fit '%s' into %d "
174 "chars\n", from, size);
175 return -1;
176 }
177 strcat(to, slash);
178 }
179 else {
180 if (strlen(save_cwd) + 1 + strlen(from) + 1 > size) {
181 cow_printf("absolutize : unable to fit '%s' into %d "
182 "chars\n", from, size);
183 return -1;
184 }
185 strcpy(to, save_cwd);
186 strcat(to, "/");
187 strcat(to, from);
188 }
189 chdir(save_cwd);
190 return 0;
191 }
192
write_cow_header(char * cow_file,int fd,char * backing_file,int sectorsize,int alignment,unsigned long long * size)193 int write_cow_header(char *cow_file, int fd, char *backing_file,
194 int sectorsize, int alignment, unsigned long long *size)
195 {
196 struct cow_header_v3 *header;
197 unsigned long modtime;
198 int err;
199
200 err = cow_seek_file(fd, 0);
201 if (err < 0) {
202 cow_printf("write_cow_header - lseek failed, err = %d\n", -err);
203 goto out;
204 }
205
206 err = -ENOMEM;
207 header = cow_malloc(sizeof(*header));
208 if (header == NULL) {
209 cow_printf("write_cow_header - failed to allocate COW V3 "
210 "header\n");
211 goto out;
212 }
213 header->magic = htonl(COW_MAGIC);
214 header->version = htonl(COW_VERSION);
215
216 err = -EINVAL;
217 if (strlen(backing_file) > sizeof(header->backing_file) - 1) {
218 /* Below, %zd is for a size_t value */
219 cow_printf("Backing file name \"%s\" is too long - names are "
220 "limited to %zd characters\n", backing_file,
221 sizeof(header->backing_file) - 1);
222 goto out_free;
223 }
224
225 if (absolutize(header->backing_file, sizeof(header->backing_file),
226 backing_file))
227 goto out_free;
228
229 err = os_file_modtime(header->backing_file, &modtime);
230 if (err < 0) {
231 cow_printf("write_cow_header - backing file '%s' mtime "
232 "request failed, err = %d\n", header->backing_file,
233 -err);
234 goto out_free;
235 }
236
237 err = cow_file_size(header->backing_file, size);
238 if (err < 0) {
239 cow_printf("write_cow_header - couldn't get size of "
240 "backing file '%s', err = %d\n",
241 header->backing_file, -err);
242 goto out_free;
243 }
244
245 header->mtime = htonl(modtime);
246 header->size = htonll(*size);
247 header->sectorsize = htonl(sectorsize);
248 header->alignment = htonl(alignment);
249 header->cow_format = COW_BITMAP;
250
251 err = cow_write_file(fd, header, sizeof(*header));
252 if (err != sizeof(*header)) {
253 cow_printf("write_cow_header - write of header to "
254 "new COW file '%s' failed, err = %d\n", cow_file,
255 -err);
256 goto out_free;
257 }
258 err = 0;
259 out_free:
260 cow_free(header);
261 out:
262 return err;
263 }
264
file_reader(__u64 offset,char * buf,int len,void * arg)265 int file_reader(__u64 offset, char *buf, int len, void *arg)
266 {
267 int fd = *((int *) arg);
268
269 return pread(fd, buf, len, offset);
270 }
271
272 /* XXX Need to sanity-check the values read from the header */
273
read_cow_header(int (* reader)(__u64,char *,int,void *),void * arg,__u32 * version_out,char ** backing_file_out,time_t * mtime_out,unsigned long long * size_out,int * sectorsize_out,__u32 * align_out,int * bitmap_offset_out)274 int read_cow_header(int (*reader)(__u64, char *, int, void *), void *arg,
275 __u32 *version_out, char **backing_file_out,
276 time_t *mtime_out, unsigned long long *size_out,
277 int *sectorsize_out, __u32 *align_out,
278 int *bitmap_offset_out)
279 {
280 union cow_header *header;
281 char *file;
282 int err, n;
283 unsigned long version, magic;
284
285 header = cow_malloc(sizeof(*header));
286 if (header == NULL) {
287 cow_printf("read_cow_header - Failed to allocate header\n");
288 return -ENOMEM;
289 }
290 err = -EINVAL;
291 n = (*reader)(0, (char *) header, sizeof(*header), arg);
292 if (n < offsetof(typeof(header->v1), backing_file)) {
293 cow_printf("read_cow_header - short header\n");
294 goto out;
295 }
296
297 magic = header->v1.magic;
298 if (magic == COW_MAGIC)
299 version = header->v1.version;
300 else if (magic == ntohl(COW_MAGIC))
301 version = ntohl(header->v1.version);
302 /* No error printed because the non-COW case comes through here */
303 else goto out;
304
305 *version_out = version;
306
307 if (version == 1) {
308 if (n < sizeof(header->v1)) {
309 cow_printf("read_cow_header - failed to read V1 "
310 "header\n");
311 goto out;
312 }
313 *mtime_out = header->v1.mtime;
314 *size_out = header->v1.size;
315 *sectorsize_out = header->v1.sectorsize;
316 *bitmap_offset_out = sizeof(header->v1);
317 *align_out = *sectorsize_out;
318 file = header->v1.backing_file;
319 }
320 else if (version == 2) {
321 if (n < sizeof(header->v2)) {
322 cow_printf("read_cow_header - failed to read V2 "
323 "header\n");
324 goto out;
325 }
326 *mtime_out = ntohl(header->v2.mtime);
327 *size_out = ntohll(header->v2.size);
328 *sectorsize_out = ntohl(header->v2.sectorsize);
329 *bitmap_offset_out = sizeof(header->v2);
330 *align_out = *sectorsize_out;
331 file = header->v2.backing_file;
332 }
333 /* This is very subtle - see above at union cow_header definition */
334 else if (version == 3 && (*((int*)header->v3.backing_file) != 0)) {
335 if (n < sizeof(header->v3)) {
336 cow_printf("read_cow_header - failed to read V3 "
337 "header\n");
338 goto out;
339 }
340 *mtime_out = ntohl(header->v3.mtime);
341 *size_out = ntohll(header->v3.size);
342 *sectorsize_out = ntohl(header->v3.sectorsize);
343 *align_out = ntohl(header->v3.alignment);
344 if (*align_out == 0) {
345 cow_printf("read_cow_header - invalid COW header, "
346 "align == 0\n");
347 }
348 *bitmap_offset_out = ROUND_UP(sizeof(header->v3), *align_out);
349 file = header->v3.backing_file;
350 }
351 else if (version == 3) {
352 cow_printf("read_cow_header - broken V3 file with"
353 " 64-bit layout - recovering content.\n");
354
355 if (n < sizeof(header->v3_b)) {
356 cow_printf("read_cow_header - failed to read V3 "
357 "header\n");
358 goto out;
359 }
360
361 /*
362 * this was used until Dec2005 - 64bits are needed to represent
363 * 2038+. I.e. we can safely do this truncating cast.
364 *
365 * Additionally, we must use ntohl() instead of ntohll(), since
366 * the program used to use the former (tested - I got mtime
367 * mismatch "0 vs whatever").
368 *
369 * Ever heard about bug-to-bug-compatibility ? ;-) */
370 *mtime_out = (time32_t) ntohl(header->v3_b.mtime);
371
372 *size_out = ntohll(header->v3_b.size);
373 *sectorsize_out = ntohl(header->v3_b.sectorsize);
374 *align_out = ntohl(header->v3_b.alignment);
375 if (*align_out == 0) {
376 cow_printf("read_cow_header - invalid COW header, "
377 "align == 0\n");
378 }
379 *bitmap_offset_out = ROUND_UP(sizeof(header->v3_b), *align_out);
380 file = header->v3_b.backing_file;
381 }
382 else {
383 cow_printf("read_cow_header - invalid COW version\n");
384 goto out;
385 }
386 err = -ENOMEM;
387 *backing_file_out = cow_strdup(file);
388 if (*backing_file_out == NULL) {
389 cow_printf("read_cow_header - failed to allocate backing "
390 "file\n");
391 goto out;
392 }
393 err = 0;
394 out:
395 cow_free(header);
396 return err;
397 }
398
init_cow_file(int fd,char * cow_file,char * backing_file,int sectorsize,int alignment,int * bitmap_offset_out,unsigned long * bitmap_len_out,int * data_offset_out)399 int init_cow_file(int fd, char *cow_file, char *backing_file, int sectorsize,
400 int alignment, int *bitmap_offset_out,
401 unsigned long *bitmap_len_out, int *data_offset_out)
402 {
403 unsigned long long size, offset;
404 char zero = 0;
405 int err;
406
407 err = write_cow_header(cow_file, fd, backing_file, sectorsize,
408 alignment, &size);
409 if (err)
410 goto out;
411
412 *bitmap_offset_out = ROUND_UP(sizeof(struct cow_header_v3), alignment);
413 cow_sizes(COW_VERSION, size, sectorsize, alignment, *bitmap_offset_out,
414 bitmap_len_out, data_offset_out);
415
416 offset = *data_offset_out + size - sizeof(zero);
417 err = cow_seek_file(fd, offset);
418 if (err < 0) {
419 cow_printf("cow bitmap lseek failed : err = %d\n", -err);
420 goto out;
421 }
422
423 /*
424 * does not really matter how much we write it is just to set EOF
425 * this also sets the entire COW bitmap
426 * to zero without having to allocate it
427 */
428 err = cow_write_file(fd, &zero, sizeof(zero));
429 if (err != sizeof(zero)) {
430 cow_printf("Write of bitmap to new COW file '%s' failed, "
431 "err = %d\n", cow_file, -err);
432 if (err >= 0)
433 err = -EINVAL;
434 goto out;
435 }
436
437 return 0;
438 out:
439 return err;
440 }
441