1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
|
/* This procedure examines a file system and figures out whether it is
* version 1 or version 2. It returns the result as an int. If the
* file system is neither, it returns -1. A typical call is:
*
* n = fsversion("/dev/hd1", "df");
*
* The first argument is the special file for the file system.
* The second is the program name, which is used in error messages.
*/
#include <sys/types.h>
#include <minix/config.h>
#include <minix/const.h>
#include <minix/minlib.h>
#include <minix/type.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdio.h>
#include <string.h>
#include "mfs/const.h"
static char super[SUPER_BLOCK_BYTES];
#define MAGIC_OFFSET_MFS 0x18
#define MAGIC_OFFSET_EXT 0x38
#define MAGIC_OFFSET_ISO9660 0x8000
#define MAGIC_VALUE_EXT2 0xef53
static int check_super(off_t offset, unsigned short magic)
{
return (memcmp(super + offset, &magic, sizeof(magic)) == 0) ? 1 : 0;
}
int fsversion(char *dev, char *prog)
{
int result = -1, fd;
if ((fd = open(dev, O_RDONLY)) < 0) {
std_err(prog);
std_err(" cannot open ");
perror(dev);
return(-1);
}
lseek(fd, (off_t) SUPER_BLOCK_BYTES, SEEK_SET); /* skip boot block */
if (read(fd, (char *) &super, sizeof(super)) != sizeof(super)) {
std_err(prog);
std_err(" cannot read super block on ");
perror(dev);
close(fd);
return(-1);
}
/* first check MFS, a valid MFS may look like EXT but not vice versa */
if (check_super(MAGIC_OFFSET_MFS, SUPER_MAGIC)) {
result = FSVERSION_MFS1;
goto done;
}
else if (check_super(MAGIC_OFFSET_MFS, SUPER_V2)) {
result = FSVERSION_MFS2;
goto done;
}
else if (check_super(MAGIC_OFFSET_MFS, SUPER_V3)) {
result = FSVERSION_MFS3;
goto done;
}
/* check ext2 */
if (check_super(MAGIC_OFFSET_EXT, MAGIC_VALUE_EXT2)) {
result = FSVERSION_EXT2;
goto done;
}
/* check ISO 9660 */
lseek(fd, (off_t) MAGIC_OFFSET_ISO9660, SEEK_SET);
if (read(fd, (char *) &super, sizeof(super)) == sizeof(super)) {
if (memcmp(super+1, "CD001", 5) == 0) {
result = FSVERSION_ISO9660;
goto done;
}
}
done:
close(fd);
return result;
}
|
