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
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
|
#include <com32.h>
#include <stdint.h>
#include <stdio.h>
#include <errno.h>
#include <unistd.h>
#include <string.h>
#include <syslinux/disk.h>
#include "utility.h"
static const char *bpbtypes[] = {
[0] = "unknown",
[1] = "2.0",
[2] = "3.0",
[3] = "3.2",
[4] = "3.4",
[5] = "4.0",
[6] = "8.0 (NT+)",
[7] = "7.0",
};
void error(const char *msg)
{
fputs(msg, stderr);
}
int guid_is0(const struct guid *guid)
{
return !*(const uint64_t *)guid && !*((const uint64_t *)guid + 1);
}
void wait_key(void)
{
int cnt;
char junk;
/* drain */
do {
errno = 0;
cnt = read(0, &junk, 1);
} while (cnt > 0 || (cnt < 0 && errno == EAGAIN));
/* wait */
do {
errno = 0;
cnt = read(0, &junk, 1);
} while (!cnt || (cnt < 0 && errno == EAGAIN));
}
void lba2chs(disk_chs *dst, const struct disk_info *di, uint64_t lba, uint32_t mode)
{
uint32_t c, h, s, t;
uint32_t cs, hs, ss;
/*
* Not much reason here, but if we have no valid CHS geometry, we assume
* "typical" ones to have something to return.
*/
if (di->cbios) {
cs = di->cyl;
hs = di->head;
ss = di->spt;
if (mode == l2c_cadd && cs < 1024 && di->lbacnt > cs*hs*ss)
cs++;
else if (mode == l2c_cmax)
cs = 1024;
} else {
if (di->disk & 0x80) {
cs = 1024;
hs = 255;
ss = 63;
} else {
cs = 80;
hs = 2;
ss = 18;
}
}
if (lba >= cs*hs*ss) {
s = ss;
h = hs - 1;
c = cs - 1;
} else {
s = ((uint32_t)lba % ss) + 1;
t = (uint32_t)lba / ss;
h = t % hs;
c = t / hs;
}
(*dst)[0] = h;
(*dst)[1] = s | ((c & 0x300) >> 2);
(*dst)[2] = c;
}
uint32_t get_file_lba(const char *filename)
{
com32sys_t inregs;
uint32_t lba;
/* Start with clean registers */
memset(&inregs, 0, sizeof(com32sys_t));
/* Put the filename in the bounce buffer */
strlcpy(__com32.cs_bounce, filename, __com32.cs_bounce_size);
/* Call comapi_open() which returns a structure pointer in SI
* to a structure whose first member happens to be the LBA.
*/
inregs.eax.w[0] = 0x0006;
inregs.esi.w[0] = OFFS(__com32.cs_bounce);
inregs.es = SEG(__com32.cs_bounce);
__com32.cs_intcall(0x22, &inregs, &inregs);
if ((inregs.eflags.l & EFLAGS_CF) || inregs.esi.w[0] == 0) {
return 0; /* Filename not found */
}
/* Since the first member is the LBA, we simply cast */
lba = *((uint32_t *) MK_PTR(inregs.ds, inregs.esi.w[0]));
/* Clean the registers for the next call */
memset(&inregs, 0, sizeof(com32sys_t));
/* Put the filename in the bounce buffer */
strlcpy(__com32.cs_bounce, filename, __com32.cs_bounce_size);
/* Call comapi_close() to free the structure */
inregs.eax.w[0] = 0x0008;
inregs.esi.w[0] = OFFS(__com32.cs_bounce);
inregs.es = SEG(__com32.cs_bounce);
__com32.cs_intcall(0x22, &inregs, &inregs);
return lba;
}
/* drive offset detection */
int drvoff_detect(int type, unsigned int *off)
{
if (bpbV40 <= type && type <= bpbVNT) {
*off = 0x24;
} else if (type == bpbV70) {
*off = 0x40;
} else
return 0;
return -1;
}
/*
* heuristics could certainly be improved
*/
int bpb_detect(const uint8_t *sec, const char *tag)
{
int a, b, c, jmp = -1, rev = 0;
/* media descriptor check */
if ((sec[0x15] & 0xF0) != 0xF0)
goto out;
if (sec[0] == 0xEB) /* jump short */
jmp = 2 + *(int8_t *)(sec + 1);
else if (sec[0] == 0xE9) /* jump near */
jmp = 3 + *(int16_t *)(sec + 1);
if (jmp < 0) /* no boot code at all ? */
goto nocode;
/* sanity */
if (jmp < 0x18 || jmp > 0x1F0)
goto out;
/* detect by jump */
if (jmp >= 0x18 && jmp < 0x1E)
rev = bpbV20;
else if (jmp >= 0x1E && jmp < 0x20)
rev = bpbV30;
else if (jmp >= 0x20 && jmp < 0x24)
rev = bpbV32;
else if (jmp >= 0x24 && jmp < 0x46)
rev = bpbV34;
/* TODO: some better V2 - V3.4 checks ? */
if (rev)
goto out;
/*
* BPB info:
* 2.0 == 0x0B - 0x17
* 3.0 == 2.0 + 0x18 - 0x1D
* 3.2 == 3.0 + 0x1E - 0x1F
* 3.4 ==!2.0 + 0x18 - 0x23
* 4.0 == 3.4 + 0x24 - 0x45
* NT ==~3.4 + 0x24 - 0x53
* 7.0 == 3.4 + 0x24 - 0x59
*/
nocode:
a = memcmp(sec + 0x03, "NTFS", 4);
b = memcmp(sec + 0x36, "FAT", 3);
c = memcmp(sec + 0x52, "FAT", 3); /* ext. DOS 7+ bs */
if ((sec[0x26] & 0xFE) == 0x28 && !b) {
rev = bpbV40;
} else if (sec[0x26] == 0x80 && !a) {
rev = bpbVNT;
} else if ((sec[0x42] & 0xFE) == 0x28 && !c) {
rev = bpbV70;
}
out:
printf("BPB detection (%s): %s\n", tag, bpbtypes[rev]);
return rev;
}
/* vim: set ts=8 sts=4 sw=4 noet: */
|
