xref: /openbmc/qemu/block/bochs.c (revision 0399a381)
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-common.h"
26 #include "block/block_int.h"
27 #include "qemu/module.h"
28 
29 /**************************************************************/
30 
31 #define HEADER_MAGIC "Bochs Virtual HD Image"
32 #define HEADER_VERSION 0x00020000
33 #define HEADER_V1 0x00010000
34 #define HEADER_SIZE 512
35 
36 #define REDOLOG_TYPE "Redolog"
37 #define GROWING_TYPE "Growing"
38 
39 // not allocated: 0xffffffff
40 
41 // always little-endian
42 struct bochs_header_v1 {
43     char magic[32]; // "Bochs Virtual HD Image"
44     char type[16]; // "Redolog"
45     char subtype[16]; // "Undoable" / "Volatile" / "Growing"
46     uint32_t version;
47     uint32_t header; // size of header
48 
49     union {
50 	struct {
51 	    uint32_t catalog; // num of entries
52 	    uint32_t bitmap; // bitmap size
53 	    uint32_t extent; // extent size
54 	    uint64_t disk; // disk size
55 	    char padding[HEADER_SIZE - 64 - 8 - 20];
56 	} redolog;
57 	char padding[HEADER_SIZE - 64 - 8];
58     } extra;
59 };
60 
61 // always little-endian
62 struct bochs_header {
63     char magic[32]; // "Bochs Virtual HD Image"
64     char type[16]; // "Redolog"
65     char subtype[16]; // "Undoable" / "Volatile" / "Growing"
66     uint32_t version;
67     uint32_t header; // size of header
68 
69     union {
70 	struct {
71 	    uint32_t catalog; // num of entries
72 	    uint32_t bitmap; // bitmap size
73 	    uint32_t extent; // extent size
74 	    uint32_t reserved; // for ???
75 	    uint64_t disk; // disk size
76 	    char padding[HEADER_SIZE - 64 - 8 - 24];
77 	} redolog;
78 	char padding[HEADER_SIZE - 64 - 8];
79     } extra;
80 };
81 
82 typedef struct BDRVBochsState {
83     CoMutex lock;
84     uint32_t *catalog_bitmap;
85     int catalog_size;
86 
87     int data_offset;
88 
89     int bitmap_blocks;
90     int extent_blocks;
91     int extent_size;
92 } BDRVBochsState;
93 
94 static int bochs_probe(const uint8_t *buf, int buf_size, const char *filename)
95 {
96     const struct bochs_header *bochs = (const void *)buf;
97 
98     if (buf_size < HEADER_SIZE)
99 	return 0;
100 
101     if (!strcmp(bochs->magic, HEADER_MAGIC) &&
102 	!strcmp(bochs->type, REDOLOG_TYPE) &&
103 	!strcmp(bochs->subtype, GROWING_TYPE) &&
104 	((le32_to_cpu(bochs->version) == HEADER_VERSION) ||
105 	(le32_to_cpu(bochs->version) == HEADER_V1)))
106 	return 100;
107 
108     return 0;
109 }
110 
111 static int bochs_open(BlockDriverState *bs, QDict *options, int flags,
112                       Error **errp)
113 {
114     BDRVBochsState *s = bs->opaque;
115     int i;
116     struct bochs_header bochs;
117     struct bochs_header_v1 header_v1;
118     int ret;
119 
120     bs->read_only = 1; // no write support yet
121 
122     ret = bdrv_pread(bs->file, 0, &bochs, sizeof(bochs));
123     if (ret < 0) {
124         return ret;
125     }
126 
127     if (strcmp(bochs.magic, HEADER_MAGIC) ||
128         strcmp(bochs.type, REDOLOG_TYPE) ||
129         strcmp(bochs.subtype, GROWING_TYPE) ||
130 	((le32_to_cpu(bochs.version) != HEADER_VERSION) &&
131 	(le32_to_cpu(bochs.version) != HEADER_V1))) {
132         error_setg(errp, "Image not in Bochs format");
133         return -EINVAL;
134     }
135 
136     if (le32_to_cpu(bochs.version) == HEADER_V1) {
137       memcpy(&header_v1, &bochs, sizeof(bochs));
138       bs->total_sectors = le64_to_cpu(header_v1.extra.redolog.disk) / 512;
139     } else {
140       bs->total_sectors = le64_to_cpu(bochs.extra.redolog.disk) / 512;
141     }
142 
143     s->catalog_size = le32_to_cpu(bochs.extra.redolog.catalog);
144     s->catalog_bitmap = g_malloc(s->catalog_size * 4);
145 
146     ret = bdrv_pread(bs->file, le32_to_cpu(bochs.header), s->catalog_bitmap,
147                      s->catalog_size * 4);
148     if (ret < 0) {
149         goto fail;
150     }
151 
152     for (i = 0; i < s->catalog_size; i++)
153 	le32_to_cpus(&s->catalog_bitmap[i]);
154 
155     s->data_offset = le32_to_cpu(bochs.header) + (s->catalog_size * 4);
156 
157     s->bitmap_blocks = 1 + (le32_to_cpu(bochs.extra.redolog.bitmap) - 1) / 512;
158     s->extent_blocks = 1 + (le32_to_cpu(bochs.extra.redolog.extent) - 1) / 512;
159 
160     s->extent_size = le32_to_cpu(bochs.extra.redolog.extent);
161 
162     qemu_co_mutex_init(&s->lock);
163     return 0;
164 
165 fail:
166     g_free(s->catalog_bitmap);
167     return ret;
168 }
169 
170 static int64_t seek_to_sector(BlockDriverState *bs, int64_t sector_num)
171 {
172     BDRVBochsState *s = bs->opaque;
173     int64_t offset = sector_num * 512;
174     int64_t extent_index, extent_offset, bitmap_offset;
175     char bitmap_entry;
176 
177     // seek to sector
178     extent_index = offset / s->extent_size;
179     extent_offset = (offset % s->extent_size) / 512;
180 
181     if (s->catalog_bitmap[extent_index] == 0xffffffff) {
182 	return -1; /* not allocated */
183     }
184 
185     bitmap_offset = s->data_offset + (512 * s->catalog_bitmap[extent_index] *
186 	(s->extent_blocks + s->bitmap_blocks));
187 
188     /* read in bitmap for current extent */
189     if (bdrv_pread(bs->file, bitmap_offset + (extent_offset / 8),
190                    &bitmap_entry, 1) != 1) {
191         return -1;
192     }
193 
194     if (!((bitmap_entry >> (extent_offset % 8)) & 1)) {
195 	return -1; /* not allocated */
196     }
197 
198     return bitmap_offset + (512 * (s->bitmap_blocks + extent_offset));
199 }
200 
201 static int bochs_read(BlockDriverState *bs, int64_t sector_num,
202                     uint8_t *buf, int nb_sectors)
203 {
204     int ret;
205 
206     while (nb_sectors > 0) {
207         int64_t block_offset = seek_to_sector(bs, sector_num);
208         if (block_offset >= 0) {
209             ret = bdrv_pread(bs->file, block_offset, buf, 512);
210             if (ret != 512) {
211                 return -1;
212             }
213         } else
214             memset(buf, 0, 512);
215         nb_sectors--;
216         sector_num++;
217         buf += 512;
218     }
219     return 0;
220 }
221 
222 static coroutine_fn int bochs_co_read(BlockDriverState *bs, int64_t sector_num,
223                                       uint8_t *buf, int nb_sectors)
224 {
225     int ret;
226     BDRVBochsState *s = bs->opaque;
227     qemu_co_mutex_lock(&s->lock);
228     ret = bochs_read(bs, sector_num, buf, nb_sectors);
229     qemu_co_mutex_unlock(&s->lock);
230     return ret;
231 }
232 
233 static void bochs_close(BlockDriverState *bs)
234 {
235     BDRVBochsState *s = bs->opaque;
236     g_free(s->catalog_bitmap);
237 }
238 
239 static BlockDriver bdrv_bochs = {
240     .format_name	= "bochs",
241     .instance_size	= sizeof(BDRVBochsState),
242     .bdrv_probe		= bochs_probe,
243     .bdrv_open		= bochs_open,
244     .bdrv_read          = bochs_co_read,
245     .bdrv_close		= bochs_close,
246 };
247 
248 static void bdrv_bochs_init(void)
249 {
250     bdrv_register(&bdrv_bochs);
251 }
252 
253 block_init(bdrv_bochs_init);
254