xref: /openbmc/qemu/block/bochs.c (revision 05caa062)
1 /*
2  * Block driver for the various disk image formats used by Bochs
3  * Currently only for "growing" type in read-only mode
4  *
5  * Copyright (c) 2005 Alex Beregszaszi
6  *
7  * Permission is hereby granted, free of charge, to any person obtaining a copy
8  * of this software and associated documentation files (the "Software"), to deal
9  * in the Software without restriction, including without limitation the rights
10  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
11  * copies of the Software, and to permit persons to whom the Software is
12  * furnished to do so, subject to the following conditions:
13  *
14  * The above copyright notice and this permission notice shall be included in
15  * all copies or substantial portions of the Software.
16  *
17  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
18  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
19  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
20  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
21  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
22  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
23  * THE SOFTWARE.
24  */
25 #include "qemu/osdep.h"
26 #include "qapi/error.h"
27 #include "block/block-io.h"
28 #include "block/block_int.h"
29 #include "qemu/module.h"
30 #include "qemu/bswap.h"
31 #include "qemu/error-report.h"
32 
33 /**************************************************************/
34 
35 #define HEADER_MAGIC "Bochs Virtual HD Image"
36 #define HEADER_VERSION 0x00020000
37 #define HEADER_V1 0x00010000
38 #define HEADER_SIZE 512
39 
40 #define REDOLOG_TYPE "Redolog"
41 #define GROWING_TYPE "Growing"
42 
43 // not allocated: 0xffffffff
44 
45 // always little-endian
46 struct bochs_header {
47     char magic[32];     /* "Bochs Virtual HD Image" */
48     char type[16];      /* "Redolog" */
49     char subtype[16];   /* "Undoable" / "Volatile" / "Growing" */
50     uint32_t version;
51     uint32_t header;    /* size of header */
52 
53     uint32_t catalog;   /* num of entries */
54     uint32_t bitmap;    /* bitmap size */
55     uint32_t extent;    /* extent size */
56 
57     union {
58         struct {
59             uint32_t reserved;  /* for ??? */
60             uint64_t disk;      /* disk size */
61             char padding[HEADER_SIZE - 64 - 20 - 12];
62         } QEMU_PACKED redolog;
63         struct {
64             uint64_t disk;      /* disk size */
65             char padding[HEADER_SIZE - 64 - 20 - 8];
66         } QEMU_PACKED redolog_v1;
67         char padding[HEADER_SIZE - 64 - 20];
68     } extra;
69 } QEMU_PACKED;
70 
71 typedef struct BDRVBochsState {
72     CoMutex lock;
73     uint32_t *catalog_bitmap;
74     uint32_t catalog_size;
75 
76     uint32_t data_offset;
77 
78     uint32_t bitmap_blocks;
79     uint32_t extent_blocks;
80     uint32_t extent_size;
81 } BDRVBochsState;
82 
83 static int bochs_probe(const uint8_t *buf, int buf_size, const char *filename)
84 {
85     const struct bochs_header *bochs = (const void *)buf;
86 
87     if (buf_size < HEADER_SIZE)
88         return 0;
89 
90     if (!strcmp(bochs->magic, HEADER_MAGIC) &&
91         !strcmp(bochs->type, REDOLOG_TYPE) &&
92         !strcmp(bochs->subtype, GROWING_TYPE) &&
93         ((le32_to_cpu(bochs->version) == HEADER_VERSION) ||
94         (le32_to_cpu(bochs->version) == HEADER_V1)))
95         return 100;
96 
97     return 0;
98 }
99 
100 static int bochs_open(BlockDriverState *bs, QDict *options, int flags,
101                       Error **errp)
102 {
103     BDRVBochsState *s = bs->opaque;
104     uint32_t i;
105     struct bochs_header bochs;
106     int ret;
107 
108     GLOBAL_STATE_CODE();
109 
110     /* No write support yet */
111     bdrv_graph_rdlock_main_loop();
112     ret = bdrv_apply_auto_read_only(bs, NULL, errp);
113     bdrv_graph_rdunlock_main_loop();
114     if (ret < 0) {
115         return ret;
116     }
117 
118     ret = bdrv_open_file_child(NULL, options, "file", bs, errp);
119     if (ret < 0) {
120         return ret;
121     }
122 
123     GRAPH_RDLOCK_GUARD_MAINLOOP();
124 
125     ret = bdrv_pread(bs->file, 0, sizeof(bochs), &bochs, 0);
126     if (ret < 0) {
127         return ret;
128     }
129 
130     if (strcmp(bochs.magic, HEADER_MAGIC) ||
131         strcmp(bochs.type, REDOLOG_TYPE) ||
132         strcmp(bochs.subtype, GROWING_TYPE) ||
133         ((le32_to_cpu(bochs.version) != HEADER_VERSION) &&
134         (le32_to_cpu(bochs.version) != HEADER_V1))) {
135         error_setg(errp, "Image not in Bochs format");
136         return -EINVAL;
137     }
138 
139     if (le32_to_cpu(bochs.version) == HEADER_V1) {
140         bs->total_sectors = le64_to_cpu(bochs.extra.redolog_v1.disk) / 512;
141     } else {
142         bs->total_sectors = le64_to_cpu(bochs.extra.redolog.disk) / 512;
143     }
144 
145     /* Limit to 1M entries to avoid unbounded allocation. This is what is
146      * needed for the largest image that bximage can create (~8 TB). */
147     s->catalog_size = le32_to_cpu(bochs.catalog);
148     if (s->catalog_size > 0x100000) {
149         error_setg(errp, "Catalog size is too large");
150         return -EFBIG;
151     }
152 
153     s->catalog_bitmap = g_try_new(uint32_t, s->catalog_size);
154     if (s->catalog_size && s->catalog_bitmap == NULL) {
155         error_setg(errp, "Could not allocate memory for catalog");
156         return -ENOMEM;
157     }
158 
159     ret = bdrv_pread(bs->file, le32_to_cpu(bochs.header), s->catalog_size * 4,
160                      s->catalog_bitmap, 0);
161     if (ret < 0) {
162         goto fail;
163     }
164 
165     for (i = 0; i < s->catalog_size; i++)
166         le32_to_cpus(&s->catalog_bitmap[i]);
167 
168     s->data_offset = le32_to_cpu(bochs.header) + (s->catalog_size * 4);
169 
170     s->bitmap_blocks = 1 + (le32_to_cpu(bochs.bitmap) - 1) / 512;
171     s->extent_blocks = 1 + (le32_to_cpu(bochs.extent) - 1) / 512;
172 
173     s->extent_size = le32_to_cpu(bochs.extent);
174     if (s->extent_size < BDRV_SECTOR_SIZE) {
175         /* bximage actually never creates extents smaller than 4k */
176         error_setg(errp, "Extent size must be at least 512");
177         ret = -EINVAL;
178         goto fail;
179     } else if (!is_power_of_2(s->extent_size)) {
180         error_setg(errp, "Extent size %" PRIu32 " is not a power of two",
181                    s->extent_size);
182         ret = -EINVAL;
183         goto fail;
184     } else if (s->extent_size > 0x800000) {
185         error_setg(errp, "Extent size %" PRIu32 " is too large",
186                    s->extent_size);
187         ret = -EINVAL;
188         goto fail;
189     }
190 
191     if (s->catalog_size < DIV_ROUND_UP(bs->total_sectors,
192                                        s->extent_size / BDRV_SECTOR_SIZE))
193     {
194         error_setg(errp, "Catalog size is too small for this disk size");
195         ret = -EINVAL;
196         goto fail;
197     }
198 
199     qemu_co_mutex_init(&s->lock);
200     return 0;
201 
202 fail:
203     g_free(s->catalog_bitmap);
204     return ret;
205 }
206 
207 static void bochs_refresh_limits(BlockDriverState *bs, Error **errp)
208 {
209     bs->bl.request_alignment = BDRV_SECTOR_SIZE; /* No sub-sector I/O */
210 }
211 
212 static int64_t coroutine_fn GRAPH_RDLOCK
213 seek_to_sector(BlockDriverState *bs, int64_t sector_num)
214 {
215     BDRVBochsState *s = bs->opaque;
216     uint64_t offset = sector_num * 512;
217     uint64_t extent_index, extent_offset, bitmap_offset;
218     char bitmap_entry;
219     int ret;
220 
221     // seek to sector
222     extent_index = offset / s->extent_size;
223     extent_offset = (offset % s->extent_size) / 512;
224 
225     if (s->catalog_bitmap[extent_index] == 0xffffffff) {
226         return 0; /* not allocated */
227     }
228 
229     bitmap_offset = s->data_offset +
230         (512 * (uint64_t) s->catalog_bitmap[extent_index] *
231         (s->extent_blocks + s->bitmap_blocks));
232 
233     /* read in bitmap for current extent */
234     ret = bdrv_co_pread(bs->file, bitmap_offset + (extent_offset / 8), 1,
235                         &bitmap_entry, 0);
236     if (ret < 0) {
237         return ret;
238     }
239 
240     if (!((bitmap_entry >> (extent_offset % 8)) & 1)) {
241         return 0; /* not allocated */
242     }
243 
244     return bitmap_offset + (512 * (s->bitmap_blocks + extent_offset));
245 }
246 
247 static int coroutine_fn GRAPH_RDLOCK
248 bochs_co_preadv(BlockDriverState *bs, int64_t offset, int64_t bytes,
249                 QEMUIOVector *qiov, BdrvRequestFlags flags)
250 {
251     BDRVBochsState *s = bs->opaque;
252     uint64_t sector_num = offset >> BDRV_SECTOR_BITS;
253     int nb_sectors = bytes >> BDRV_SECTOR_BITS;
254     uint64_t bytes_done = 0;
255     QEMUIOVector local_qiov;
256     int ret;
257 
258     assert(QEMU_IS_ALIGNED(offset, BDRV_SECTOR_SIZE));
259     assert(QEMU_IS_ALIGNED(bytes, BDRV_SECTOR_SIZE));
260 
261     qemu_iovec_init(&local_qiov, qiov->niov);
262     qemu_co_mutex_lock(&s->lock);
263 
264     while (nb_sectors > 0) {
265         int64_t block_offset = seek_to_sector(bs, sector_num);
266         if (block_offset < 0) {
267             ret = block_offset;
268             goto fail;
269         }
270 
271         qemu_iovec_reset(&local_qiov);
272         qemu_iovec_concat(&local_qiov, qiov, bytes_done, 512);
273 
274         if (block_offset > 0) {
275             ret = bdrv_co_preadv(bs->file, block_offset, 512,
276                                  &local_qiov, 0);
277             if (ret < 0) {
278                 goto fail;
279             }
280         } else {
281             qemu_iovec_memset(&local_qiov, 0, 0, 512);
282         }
283         nb_sectors--;
284         sector_num++;
285         bytes_done += 512;
286     }
287 
288     ret = 0;
289 fail:
290     qemu_co_mutex_unlock(&s->lock);
291     qemu_iovec_destroy(&local_qiov);
292 
293     return ret;
294 }
295 
296 static void bochs_close(BlockDriverState *bs)
297 {
298     BDRVBochsState *s = bs->opaque;
299     g_free(s->catalog_bitmap);
300 }
301 
302 static BlockDriver bdrv_bochs = {
303     .format_name	= "bochs",
304     .instance_size	= sizeof(BDRVBochsState),
305     .bdrv_probe		= bochs_probe,
306     .bdrv_open		= bochs_open,
307     .bdrv_child_perm     = bdrv_default_perms,
308     .bdrv_refresh_limits = bochs_refresh_limits,
309     .bdrv_co_preadv = bochs_co_preadv,
310     .bdrv_close		= bochs_close,
311     .is_format          = true,
312 };
313 
314 static void bdrv_bochs_init(void)
315 {
316     bdrv_register(&bdrv_bochs);
317 }
318 
319 block_init(bdrv_bochs_init);
320