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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 /* Limited driver for the Qcow2 filesystem, capable of extracting snapshot
18  * metadata from Qcow2 formatted image file.
19  *
20  * Similar functionality is implemented in block/qcow2.c, block/qcow2-snapshot.c
21  * and block.c. This separate implementation was made to further decouple the UI
22  * of the Android emulator from the underlying Qemu system. It allows the UI to
23  * show snapshot listings without having to fall back on Qemu's block driver
24  * system, which would pull in a lot of code irrelevant for the UI.
25  */
26 
27 #include <errno.h>
28 #include <fcntl.h>
29 #include <stdint.h>
30 #include <stdio.h>
31 #include <stdlib.h>
32 #include <string.h>
33 #include <time.h>
34 #include <unistd.h>
35 
36 #include "bswap.h"
37 #include "android/utils/debug.h"
38 #include "android/utils/system.h"
39 #include "android/snapshot.h"
40 
41 /* "Magic" sequence of four bytes required by spec to be the first four bytes
42  * of any Qcow file.
43  */
44 #define QCOW_MAGIC (('Q' << 24) | ('F' << 16) | ('I' << 8) | 0xfb)
45 #define QCOW_VERSION 2
46 
47 /* Reads 'nbyte' bytes from 'fd' into 'buf', retrying on interrupts.
48  * Exit()s if the read fails for any other reason.
49  */
50 static int
read_or_die(int fd,void * buf,size_t nbyte)51 read_or_die(int fd, void *buf, size_t nbyte)
52 {
53     int ret = 0;
54     do {
55         ret = read(fd, buf, nbyte);
56     }
57     while(ret < 0 && errno == EINTR);
58 
59     if (ret < 0) {
60         derror("read failed: %s", strerror(errno));
61         exit(1);
62     }
63 
64     return ret;
65 }
66 
67 /* Wrapper around lseek(), exit()s on error.
68  */
69 static off_t
seek_or_die(int fd,off_t offset,int whence)70 seek_or_die(int fd, off_t offset, int whence)
71 {
72     off_t ret = lseek(fd, offset, whence);
73     if (ret < 0) {
74         derror("seek failed: %s", strerror(errno));
75         exit(1);
76     }
77     return ret;
78 }
79 
80 
81 typedef struct SnapshotInfo {
82     char *id_str;
83     char *name;
84 
85     uint32_t date_sec;
86     uint32_t date_nsec;
87 
88     uint64_t vm_clock_nsec;
89     uint32_t vm_state_size;
90 } SnapshotInfo;
91 
92 static SnapshotInfo*
snapshot_info_alloc()93 snapshot_info_alloc()
94 {
95     return android_alloc(sizeof(SnapshotInfo));
96 }
97 
98 static void
snapshot_info_free(SnapshotInfo * info)99 snapshot_info_free( SnapshotInfo* info )
100 {
101     AFREE(info->id_str);
102     AFREE(info->name);
103     AFREE(info);
104 }
105 
106 
107 /* Reads a snapshot record from a qcow2-formatted file.
108  *
109  * The function assumes the file position of 'fd' points to the beginning of a
110  * QcowSnapshotHeader record. When the call returns, the file position of fd is
111  * at the place where the next QcowSnapshotHeader should start, if there is one.
112  *
113  * C.f. QCowSnapshotHeader in block/qcow2-snapshot.c for the complete layout of
114  * the header.
115  */
116 static void
snapshot_info_read(int fd,SnapshotInfo * info)117 snapshot_info_read( int fd, SnapshotInfo* info )
118 {
119     uint64_t start_offset = seek_or_die(fd, 0, SEEK_CUR);
120 
121     uint32_t extra_data_size;
122     uint16_t id_str_size, name_size;
123 
124     /* read fixed-length fields */
125     seek_or_die(fd, 12, SEEK_CUR);  /* skip l1 info */
126     read_or_die(fd, &id_str_size,         sizeof(id_str_size));
127     read_or_die(fd, &name_size,           sizeof(name_size));
128     read_or_die(fd, &info->date_sec,      sizeof(info->date_sec));
129     read_or_die(fd, &info->date_nsec,     sizeof(info->date_nsec));
130     read_or_die(fd, &info->vm_clock_nsec, sizeof(info->vm_clock_nsec));
131     read_or_die(fd, &info->vm_state_size, sizeof(info->vm_state_size));
132     read_or_die(fd, &extra_data_size,     sizeof(extra_data_size));
133 
134     /* convert to host endianness */
135     be16_to_cpus(&id_str_size);
136     be16_to_cpus(&name_size);
137     be32_to_cpus(&info->date_sec);
138     be32_to_cpus(&info->date_nsec);
139     be64_to_cpus(&info->vm_clock_nsec);
140     be32_to_cpus(&info->vm_state_size);
141     be32_to_cpus(&extra_data_size);
142     be32_to_cpus(&extra_data_size);
143 
144     /* read variable-length buffers*/
145     info->id_str = android_alloc(id_str_size + 1); // +1: manual null-termination
146     info->name   = android_alloc(name_size + 1);
147     seek_or_die(fd, extra_data_size, SEEK_CUR);  /* skip extra data */
148     read_or_die(fd, info->id_str, id_str_size);
149     read_or_die(fd, info->name, name_size);
150 
151     info->id_str[id_str_size] = '\0';
152     info->name[name_size] = '\0';
153 
154     /* headers are 8 byte aligned, ceil to nearest multiple of 8 */
155     uint64_t end_offset   = seek_or_die(fd, 0, SEEK_CUR);
156     uint32_t total_size   = end_offset - start_offset;
157     uint32_t aligned_size = ((total_size - 1) / 8 + 1) * 8;
158 
159     /* skip to start of next record */
160     seek_or_die(fd, start_offset + aligned_size, SEEK_SET);
161 }
162 
163 
164 #define NB_SUFFIXES 4
165 
166 /* Returns the size of a snapshot in a human-readable format.
167  *
168  * This function copyright (c) 2003 Fabrice Bellard
169  */
170 static char*
snapshot_format_size(char * buf,int buf_size,int64_t size)171 snapshot_format_size( char *buf, int buf_size, int64_t size )
172 {
173     static const char suffixes[NB_SUFFIXES] = "KMGT";
174     int64_t base;
175     int i;
176 
177     if (size <= 999) {
178         snprintf(buf, buf_size, "%" PRId64, size);
179     } else {
180         base = 1024;
181         for(i = 0; i < NB_SUFFIXES; i++) {
182             if (size < (10 * base)) {
183                 snprintf(buf, buf_size, "%0.1f%c",
184                          (double)size / base,
185                          suffixes[i]);
186                 break;
187             } else if (size < (1000 * base) || i == (NB_SUFFIXES - 1)) {
188                 snprintf(buf, buf_size, "%" PRId64 "%c",
189                          ((size + (base >> 1)) / base),
190                          suffixes[i]);
191                 break;
192             }
193             base = base * 1024;
194         }
195     }
196     return buf;
197 }
198 
199 static char*
snapshot_format_create_date(char * buf,size_t buf_size,time_t * time)200 snapshot_format_create_date( char *buf, size_t buf_size, time_t *time )
201 {
202     struct tm *tm;
203     tm = localtime(time);
204     strftime(buf, buf_size, "%Y-%m-%d %H:%M:%S", tm);
205     return buf;
206 }
207 
208 static char*
snapshot_format_vm_clock(char * buf,size_t buf_size,uint64_t vm_clock_nsec)209 snapshot_format_vm_clock( char *buf, size_t buf_size, uint64_t vm_clock_nsec )
210 {
211     uint64_t secs = vm_clock_nsec / 1000000000;
212     snprintf(buf, buf_size, "%02d:%02d:%02d.%03d",
213                             (int)(secs / 3600),
214                             (int)((secs / 60) % 60),
215                             (int)(secs % 60),
216                             (int)((vm_clock_nsec / 1000000) % 1000));
217     return buf;
218 }
219 
220 /* Prints a row of the snapshot table to stdout. */
221 static void
snapshot_info_print(SnapshotInfo * info)222 snapshot_info_print( SnapshotInfo *info )
223 {
224     char size_buf[8];
225     char date_buf[21];
226     char clock_buf[21];
227 
228     snapshot_format_size(size_buf, sizeof(size_buf), info->vm_state_size);
229     snapshot_format_create_date(date_buf, sizeof(date_buf),
230                                 (time_t*) &info->date_sec);
231     snapshot_format_vm_clock(clock_buf, sizeof(clock_buf), info->vm_clock_nsec);
232 
233     printf(" %-10s%-20s%7s%20s%15s\n",
234            info->id_str, info->name, size_buf, date_buf, clock_buf);
235 }
236 
237 /* Prints table of all snapshots recorded in the file 'fd'.
238  */
239 static void
snapshot_print_table(int fd,uint32_t nb_snapshots,uint64_t snapshots_offset)240 snapshot_print_table( int fd, uint32_t nb_snapshots, uint64_t snapshots_offset )
241 {
242     printf(" %-10s%-20s%7s%20s%15s\n",
243            "ID", "TAG", "VM SIZE", "DATE", "VM CLOCK");
244 
245     /* skip ahead to snapshot data */
246     seek_or_die(fd, snapshots_offset, SEEK_SET);
247 
248     /* iterate over snapshot records */
249     int i;
250     for (i = 0; i < nb_snapshots; i++) {
251         SnapshotInfo *info = snapshot_info_alloc();
252         snapshot_info_read(fd, info);
253         snapshot_info_print(info);
254 
255         snapshot_info_free(info);
256     }
257 }
258 
259 /* Validates that 'fd' starts with a correct Qcow 2 header. Prints an error and
260  * exit()s if validation fails.
261  */
262 static void
snapshot_validate_qcow_file(int fd)263 snapshot_validate_qcow_file( int fd )
264 {
265     /* read magic number and qcow version (2x4 bytes) */
266     uint32_t magic, version;
267     read_or_die(fd, &magic, sizeof(magic));
268     read_or_die(fd, &version, sizeof(version));
269     be32_to_cpus(&magic);
270     be32_to_cpus(&version);
271 
272     if (magic != QCOW_MAGIC) {
273         derror("Not a valid Qcow snapshot file (expected magic value '%08x', got '%08x').",
274                QCOW_MAGIC, magic);
275         exit(1);
276     }
277     if (version != QCOW_VERSION) {
278         derror("Unsupported Qcow version (need %d, got %d).",
279                QCOW_VERSION, version);
280         exit(1);
281     }
282 }
283 
284 /* Reads snapshot information from a Qcow2 file header.
285  *
286  * C.f. QCowHeader in block/qcow2.h for an exact listing of the header
287  * contents.
288  */
289 static void
snapshot_read_qcow_header(int fd,uint32_t * nb_snapshots,uint64_t * snapshots_offset)290 snapshot_read_qcow_header( int fd, uint32_t *nb_snapshots, uint64_t *snapshots_offset )
291 {
292     snapshot_validate_qcow_file(fd);
293 
294     /* skip non-snapshot related metadata (4x8 + 5x4 = 52 bytes)*/
295     seek_or_die(fd, 52, SEEK_CUR);
296 
297     read_or_die(fd, nb_snapshots, sizeof(*nb_snapshots));
298     read_or_die(fd, snapshots_offset, sizeof(*snapshots_offset));
299 
300     /* convert to host endianness */
301     be32_to_cpus(nb_snapshots);
302     be64_to_cpus(snapshots_offset);
303 }
304 
305 /* Prints a table with information on the snapshots in the qcow2-formatted file
306  * 'snapstorage', then exit()s.
307  */
308 void
snapshot_print_and_exit(const char * snapstorage)309 snapshot_print_and_exit( const char *snapstorage )
310 {
311     /* open snapshot file */
312     int fd = open(snapstorage, O_RDONLY);
313     if (fd < 0) {
314         derror("Could not open snapshot file '%s': %s", snapstorage, strerror(errno));
315         exit(1);
316     }
317 
318     /* read snapshot info from file header */
319     uint32_t nb_snapshots;
320     uint64_t snapshots_offset;
321     snapshot_read_qcow_header(fd, &nb_snapshots, &snapshots_offset);
322 
323     if (nb_snapshots > 0) {
324         printf("Snapshots in file '%s':\n", snapstorage);
325         snapshot_print_table(fd, nb_snapshots, snapshots_offset);
326     }
327     else {
328         printf("File '%s' contains no snapshots yet.\n", snapstorage);
329     }
330 
331     close(fd);
332     exit(0);
333 }
334