aboutsummaryrefslogtreecommitdiffstats
path: root/dosutil/mdiskchk.c
blob: 47bb08e58dedc8740a1ec98951f02abd7900e48c (plain)
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
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
/* -*- c -*- ------------------------------------------------------------- *
 *
 *   Copyright 2003-2008 H. Peter Anvin - All Rights Reserved
 *   Portions copyright 2010 Shao Miller
 *
 *   This program is free software; you can redistribute it and/or modify
 *   it under the terms of the GNU General Public License as published by
 *   the Free Software Foundation, Inc., 53 Temple Place Ste 330,
 *   Boston MA 02111-1307, USA; either version 2 of the License, or
 *   (at your option) any later version; incorporated herein by reference.
 *
 * ----------------------------------------------------------------------- */

/*
 * mdiskchk.c
 *
 * DOS program to check for the existence of a memdisk.
 *
 * This program can be compiled for DOS with the OpenWatcom compiler
 * (http://www.openwatcom.org/):
 *
 * wcl -3 -osx -mt mdiskchk.c
 */

#include <ctype.h>
#include <stdio.h>
#include <string.h>
#include <i86.h>		/* For MK_FP() */

typedef unsigned long uint32_t;
typedef unsigned short uint16_t;
typedef unsigned char uint8_t;

/* Pull in MEMDISK common structures */
#include "../memdisk/mstructs.h"

struct memdiskinfo {
    struct mdi mdi;

    /* We add our own fields at the end */
    int cylinders;
    int heads;
    int sectors;
};

struct memdiskinfo *query_memdisk(int drive)
{
    static struct memdiskinfo mm;
    uint32_t _eax, _ebx, _ecx, _edx;
    uint16_t _es, _di;
    unsigned char _dl = drive;
    uint16_t bytes;

    __asm {
	.386;
	mov eax, 454d0800h;
	mov ecx, 444d0000h;
	mov edx, 53490000h;
	mov dl, _dl;
	mov ebx, 3f4b0000h;
	int 13h;
	mov _eax, eax;
	mov _ecx, ecx;
	mov _edx, edx;
	mov _ebx, ebx;
	mov _es, es;
	mov _di, di;
    }

    if (_eax >> 16 != 0x4d21 ||
	_ecx >> 16 != 0x4d45 || _edx >> 16 != 0x4944 || _ebx >> 16 != 0x4b53)
	return NULL;

    memset(&mm, 0, sizeof mm);

    bytes = *(uint16_t far *) MK_FP(_es, _di);

    /* 27 is the most we know how to handle */
    if (bytes > 27)
	bytes = 27;

    _fmemcpy((void far *)&mm, (void far *)MK_FP(_es, _di), bytes);

    mm.cylinders = ((_ecx >> 8) & 0xff) + ((_ecx & 0xc0) << 2) + 1;
    mm.heads = ((_edx >> 8) & 0xff) + 1;
    mm.sectors = (_ecx & 0x3f);

    return &mm;
}

const char *bootloadername(uint8_t id)
{
    static const struct {
	uint8_t id, mask;
	const char *name;
    } *lp, list[] = {
	{0x00, 0xf0, "LILO"}, 
	{0x10, 0xf0, "LOADLIN"},
	{0x31, 0xff, "SYSLINUX"},
	{0x32, 0xff, "PXELINUX"},
	{0x33, 0xff, "ISOLINUX"},
	{0x34, 0xff, "EXTLINUX"},
	{0x30, 0xf0, "SYSLINUX family"},
	{0x40, 0xf0, "Etherboot"},
	{0x50, 0xf0, "ELILO"},
	{0x70, 0xf0, "GrUB"},
	{0x80, 0xf0, "U-Boot"},
	{0xA0, 0xf0, "Gujin"},
	{0xB0, 0xf0, "Qemu"},
	{0x00, 0x00, "unknown"}
    };

    for (lp = list;; lp++) {
	if (((id ^ lp->id) & lp->mask) == 0)
	    return lp->name;
    }
}

/* The function type for an output function */
#define OUTPUT_FUNC_DECL(x) \
void x(const int d, const struct memdiskinfo * const m)
typedef OUTPUT_FUNC_DECL((*output_func));

/* Show MEMDISK information for the passed structure */
static OUTPUT_FUNC_DECL(normal_output)
{
    if (m == NULL)
	return;
    printf("Drive %02X is MEMDISK %u.%02u:\n"
	   "\tAddress = 0x%08lx, len = %lu sectors, chs = %u/%u/%u,\n"
	   "\tloader = 0x%02x (%s),\n"
	   "\tcmdline = %Fs\n",
	   d, m->mdi.version_major, m->mdi.version_minor,
	   m->mdi.diskbuf, m->mdi.disksize, m->cylinders, m->heads, m->sectors,
	   m->mdi.bootloaderid, bootloadername(m->mdi.bootloaderid),
	   MK_FP(m->mdi.cmdline.seg_off.segment,
		 m->mdi.cmdline.seg_off.offset));
}

/* Yield DOS SET command(s) as output for each MEMDISK kernel argument */
static OUTPUT_FUNC_DECL(batch_output)
{
    if (m != NULL) {
	char buf[256], *bc;
	const char far *c =
	    MK_FP(m->mdi.cmdline.seg_off.segment,
		  m->mdi.cmdline.seg_off.offset);
	const char *have_equals, is_set[] = "=1";

	while (*c != '\0') {
	    /* Skip whitespace */
	    while (isspace(*c))
		c++;
	    if (*c == '\0')
		/* Trailing whitespace.  That's enough processing */
		break;
	    /* Walk the kernel arguments while filling the buffer,
	     * looking for space or NUL or checking for a full buffer
	     */
	    bc = buf;
	    have_equals = is_set;
	    while ((*c != '\0') && !isspace(*c) &&
		   (bc < &buf[sizeof(buf) - 1])) {
		/* Check if the param is "x=y" */
		if (*c == '=')
		    /* "=1" not needed */
		    have_equals = &is_set[sizeof(is_set) - 1];
		*bc = *c;
		c++;
		bc++;
	    }
	    /* Found the end of the parameter and optional value sequence */
	    *bc = '\0';
	    printf("set %s%s\n", buf, have_equals);
	}
    }
}

/* We do not output batch file output by default.  We show MEMDISK info */
static output_func show_memdisk = normal_output;

/* A generic function type */
#define MDISKCHK_FUNC_DECL(x) \
void x(void)
typedef MDISKCHK_FUNC_DECL((*mdiskchk_func));

static MDISKCHK_FUNC_DECL(do_nothing)
{
    return;
}

static MDISKCHK_FUNC_DECL(show_usage)
{
    printf("\nUsage: mdiskchk [--safe-hooks] [--mbfts] [--batch-output]\n"
	   "\n"
	   "Action: --safe-hooks . . Will scan INT 13h \"safe hook\" chain\n"
	   "        --mbfts . . . .  Will scan memory for MEMDISK mBFTs\n"
	   "        --batch-output . Will output SET command output based\n"
	   "                         on MEMDISK kernel arguments\n"
	   "        --no-sequential  Suppresses probing all drive numbers\n");
}

/* Search memory for mBFTs and report them via the output method */
static MDISKCHK_FUNC_DECL(show_mbfts)
{
    const uint16_t far * const free_base_mem =
	MK_FP(0x0040, 0x0013);
    int seg;
    uint8_t chksum;
    uint32_t i;
    const struct mBFT far *mbft;
    struct memdiskinfo m;
    struct patch_area far *patch_area;

    for (seg = *free_base_mem / 16; seg < 0x9FFF; seg++) {
	mbft = MK_FP(seg, 0);
	/* Check for signature */
	if (mbft->acpi.signature[0] != 'm' ||
	    mbft->acpi.signature[1] != 'B' ||
	    mbft->acpi.signature[2] != 'F' ||
	    mbft->acpi.signature[3] != 'T')
	    continue;
	if (mbft->acpi.length != sizeof(struct mBFT))
	    continue;
	/* Check sum */
	chksum = 0;
	for (i = 0; i < sizeof(struct mBFT); i++)
	    chksum += ((const uint8_t far *)mbft)[i];
	if (chksum)
	    continue;
	/* Copy the MDI from the mBFT */
	_fmemcpy((void far *)&m, &mbft->mdi, sizeof(struct mdi));
	/* Adjust C/H/S since we actually know
	 * it directly for any MEMDISK with an mBFT
	 */
	patch_area = (struct patch_area far *)&mbft->mdi;
	m.cylinders = patch_area->cylinders;
	m.heads = patch_area->heads;
	m.sectors = patch_area->sectors;
	show_memdisk(patch_area->driveno, &m);
    }
}

/* Walk the "safe hook" chain as far as possible
 * and report MEMDISKs that we find via the output method
 */
static MDISKCHK_FUNC_DECL(show_safe_hooks)
{
    const real_addr_t far * const int13 =
	MK_FP(0x0000, 0x0013 * sizeof(real_addr_t));
    const struct safe_hook far *hook =
	MK_FP(int13->seg_off.segment, int13->seg_off.offset);

    while ((hook->signature[0] == '$') &&
	   (hook->signature[1] == 'I') &&
	   (hook->signature[2] == 'N') &&
	   (hook->signature[3] == 'T') &&
	   (hook->signature[4] == '1') &&
	   (hook->signature[5] == '3') &&
	   (hook->signature[6] == 'S') &&
	   (hook->signature[7] == 'F')) {
	/* Found a valid "safe hook" */
	if ((hook->vendor[0] == 'M') &&
	    (hook->vendor[1] == 'E') &&
	    (hook->vendor[2] == 'M') &&
	    (hook->vendor[3] == 'D') &&
	    (hook->vendor[4] == 'I') &&
	    (hook->vendor[5] == 'S') &&
	    (hook->vendor[6] == 'K')) {
	    /* Found a valid MEMDISK "safe hook".  It will have an mBFT */
	    const struct mBFT far *mbft;
	    struct memdiskinfo m;
	    struct patch_area far *patch_area;

	    /* Copy the MDI from the mBFT.  Offset is a misnomer here */
	    mbft = MK_FP(hook->mbft >> 4, 0);	/* Always aligned */
	    _fmemcpy((void far *)&m, &mbft->mdi, sizeof(struct mdi));
	    /* Adjust C/H/S since we actually know
	     * it directly for any MEMDISK with an mBFT
	     */
	    patch_area = (struct patch_area far *)&mbft->mdi;
	    m.cylinders = patch_area->cylinders;
	    m.heads = patch_area->heads;
	    m.sectors = patch_area->sectors;
	    show_memdisk(patch_area->driveno, &m);
	} /* if */
	/* Step to the next hook in the "safe hook" chain */
	hook = MK_FP(hook->old_hook.seg_off.segment,
		     hook->old_hook.seg_off.offset);
    } /* while */
}

int main(int argc, char *argv[])
{
    int d;
    int found = 0;
    int sequential_scan = 1;	/* Classic behaviour */
    const struct memdiskinfo *m;

    /* Default behaviour */
    mdiskchk_func usage = do_nothing,
	safe_hooks = do_nothing,
	mbfts = do_nothing;

    /* For each argument */
    while (--argc) {
	/* Argument should begin with one of these chars */
	if ((*argv[argc] != '/') && (*argv[argc] != '-')) {
	    /* It doesn't.  Print usage soon */
	    usage = show_usage;
	    break;
	}
	argv[argc]++;

	/* Next char might be '-' as in "--safe-hooks" */
	if (*argv[argc] == '-')
	    argv[argc]++;

	switch (*argv[argc]) {
	    case 'S':
	    case 's':
		safe_hooks = show_safe_hooks;
		break;
	    case 'M':
	    case 'm':
		mbfts = show_mbfts;
		break;
	    case 'B':
	    case 'b':
		show_memdisk = batch_output;
		break;
	    case 'N':
	    case 'n':
		sequential_scan = 0;
		break;
	    default:
		usage = show_usage;
	} /* switch */
   } /* while */

    safe_hooks();
    mbfts();
    if (!sequential_scan)
	goto skip_sequential;
    for (d = 0; d <= 0xff; d++) {
	m = query_memdisk(d);
	if (m != NULL) {
	    found++;
	    show_memdisk(d, m);
	}
    }
skip_sequential:
    usage();

    return found;
}