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2 - 1 
/*
2 
 * Debugging boot sector.  Reads the first directory
3 
 * sector from disk and displays it.
4 
 *
5 
 * It relies on the _volid field in the FAT header containing
6 
 * the LBA of the root directory.
7 
 */
8 
#include "x16.h"
9 
 
10 
#define DIROFF		0x00200		/* where to read the root directory (offset) */
11 
#define LOADSEG		(0x10000/16)	/* where to load code (64KB) */
12 
#define LOADOFF		0
13 
 
14 
/*
15 
 * FAT directory entry.
16 
 */
17 
#define Dname		0x00
18 
#define Dext		0x08
19 
#define Dattr		0x0B
20 
#define Dtime		0x16
21 
#define Ddate		0x18
22 
#define Dstart		0x1A
23 
#define Dlengthlo	0x1C
24 
#define Dlengthhi	0x1E
25 
 
26 
#define Dirsz		0x20
27 
 
28 
/*
29 
 * We keep data on the stack, indexed by rBP.
30 
 */
31 
#define Xdrive		0x00		/* boot drive, passed by BIOS in rDL */
32 
#define Xrootlo		0x02		/* offset of root directory */
33 
#define Xroothi		0x04
34 
#define Xrootsz		0x06		/* file data area */
35 
#define Xtotal		0x08		/* sum of allocated data above */
36 
#define Xdap		0x00		/* disc address packet */
37 
 
38 
TEXT _magic(SB), $0
39 
	BYTE $0xEB; BYTE $0x3C;		/* jmp .+ 0x3C  (_start0x3E) */
40 
	BYTE $0x90			/* nop */
41 
TEXT _version(SB), $0
42 
	BYTE $0x00; BYTE $0x00; BYTE $0x00; BYTE $0x00;
43 
	BYTE $0x00; BYTE $0x00; BYTE $0x00; BYTE $0x00
44 
TEXT _sectsize(SB), $0
45 
	BYTE $0x00; BYTE $0x00
46 
TEXT _clustsize(SB), $0
47 
	BYTE $0x00
48 
TEXT _nresrv(SB), $0
49 
	BYTE $0x00; BYTE $0x00
50 
TEXT _nfats(SB), $0
51 
	BYTE $0x00
52 
TEXT _rootsize(SB), $0
53 
	BYTE $0x00; BYTE $0x00
54 
TEXT _volsize(SB), $0
55 
	BYTE $0x00; BYTE $0x00
56 
TEXT _mediadesc(SB), $0
57 
	BYTE $0x00
58 
TEXT _fatsize(SB), $0
59 
	BYTE $0x00; BYTE $0x00
60 
TEXT _trksize(SB), $0
61 
	BYTE $0x00; BYTE $0x00
62 
TEXT _nheads(SB), $0
63 
	BYTE $0x00; BYTE $0x00
64 
TEXT _nhiddenlo(SB), $0
65 
	BYTE $0x00; BYTE $0x00
66 
TEXT _nhiddenhi(SB), $0
67 
	BYTE $0x00; BYTE $0x00;
68 
TEXT _bigvolsize(SB), $0
69 
	BYTE $0x00; BYTE $0x00; BYTE $0x00; BYTE $0x00;
70 
TEXT _driveno(SB), $0
71 
	BYTE $0x00
72 
TEXT _reserved0(SB), $0
73 
	BYTE $0x00
74 
TEXT _bootsig(SB), $0
75 
	BYTE $0x00
76 
TEXT _volid(SB), $0
77 
	BYTE $0x00; BYTE $0x00; BYTE $0x00; BYTE $0x00;
78 
TEXT _label(SB), $0
79 
	BYTE $0x00; BYTE $0x00; BYTE $0x00; BYTE $0x00;
80 
	BYTE $0x00; BYTE $0x00; BYTE $0x00; BYTE $0x00
81 
	BYTE $0x00; BYTE $0x00; BYTE $0x00
82 
TEXT _type(SB), $0
83 
	BYTE $0x00; BYTE $0x00; BYTE $0x00; BYTE $0x00;
84 
	BYTE $0x00; BYTE $0x00; BYTE $0x00; BYTE $0x00;
85 
 
86 
_start0x3E:
87 
	CLI
88 
	CLR(rAX)
89 
	MTSR(rAX, rSS)			/* 0000 -> rSS */
90 
	MTSR(rAX, rDS)			/* 0000 -> rDS, source segment */
91 
	MTSR(rAX, rES)
92 
	LWI(_magic-Xtotal(SB), rSP)
93 
	MW(rSP, rBP)			/* set the indexed-data pointer */
94 
 
95 
	SBPB(rDL, Xdrive)		/* save the boot drive */
96 
 
97 
	STI
98 
 
99 
	LWI(confidence(SB), rSI)	/* for that warm, fuzzy feeling */
100 
	CALL(BIOSputs(SB))
101 
 
102 
	LBI(0x41, rAH)			/* check extensions present */
103 
	LWI(0x55AA, rBX)
104 
	LXB(Xdrive, xBP, rDL)		/* drive */
105 
	SYSCALL(0x13)			/* CF set on failure */
106 
	JCS _jmp01
107 
	CMPI(0xAA55, rBX)
108 
	JNE _jmp01
109 
	ANDI(0x0001, rCX)
110 
	JEQ _jmp01
111 
 
112 
					/* rCX contains 0x0001 */
113 
	SBPWI(0x0010, Xdap+0)		/* reserved + packet size */
114 
	SBPW(rCX, Xdap+2)		/* reserved + # of blocks to transfer */
115 
 
116 
	DEC(rCX)
117 
	SBPW(rCX, Xdap+12)
118 
	SBPW(rCX, Xdap+14)
119 
 
120 
/* BIOSread will do this 	CALL(dreset(SB)) */
121 
 
122 
_jmp00:
123 
	LW(_volid(SB), rAX)		/* Xrootlo */
124 
	LW(_volid+2(SB), rDX)		/* Xroothi */
125 
 
126 
	LWI(_magic+DIROFF(SB), rBX)
127 
	CALL(BIOSread(SB))		/* read the root directory */
128 
 
129 
	CALL(printnl(SB))
130 
	LWI(_magic+DIROFF(SB), rBX)
131 
	LWI((512/2), rCX)
132 
	CALL(printbuf(SB))
133 
 
134 
xloop:
135 
	JMP xloop
136 
 
137 
 
138 
_jmp01:
139 
 
140 
TEXT buggery(SB), $0
141 
	LWI(error(SB), rSI)
142 
	CALL(BIOSputs(SB))
143 
 
144 
xbuggery:
145 
	JMP xbuggery
146 
 
147 
/*
148 
 * Read a sector from a disc. On entry:
149 
 *   rDX:rAX	sector number
150 
 *   rES:rBX	buffer address
151 
 */
152 
TEXT BIOSread(SB), $0
153 
	LWI(5, rDI)			/* retry count (ATAPI ZIPs suck) */
154 
_retry:
155 
	PUSHA				/* may be trashed by SYSCALL */
156 
 
157 
	SBPW(rBX, Xdap+4)		/* transfer buffer :offset */
158 
	MFSR(rES, rDI)			/* transfer buffer seg: */
159 
	SBPW(rDI, Xdap+6)
160 
	SBPW(rAX, Xdap+8)		/* LBA (64-bits) */
161 
	SBPW(rDX, Xdap+10)
162 
 
163 
	MW(rBP, rSI)			/* disk address packet */
164 
	LBI(0x42, rAH)			/* extended read */
165 
	LBPB(Xdrive, rDL)		/* form drive */
166 
	SYSCALL(0x13)			/* CF set on failure */
167 
	JCC _BIOSreadret
168 
 
169 
	POPA
170 
	DEC(rDI)			/* too many retries? */
171 
	JEQ _ioerror
172 
 
173 
	CALL(dreset(SB))
174 
	JMP _retry
175 
 
176 
_ioerror:
177 
	LWI(ioerror(SB), rSI)
178 
	CALL(BIOSputs(SB))
179 
	JMP xbuggery
180 
 
181 
_BIOSreadret:
182 
	POPA
183 
	RET
184 
 
185 
TEXT dreset(SB), $0
186 
	PUSHA
187 
	CLR(rAX)			/* rAH == 0 == reset disc system */
188 
	LBPB(Xdrive, rDL)
189 
	SYSCALL(0x13)
190 
	ORB(rAH, rAH)			/* status (0 == success) */
191 
	POPA
192 
	JNE _ioerror
193 
	RET
194 
 
195 
 
196 
TEXT printsharp(SB), $0
197 
	LWI(sharp(SB), rSI)
198 
_doprint:
199 
	CALL(BIOSputs(SB))
200 
	RET
201 
 
202 
TEXT printspace(SB), $0
203 
	LWI(space(SB), rSI)
204 
	JMP _doprint
205 
 
206 
TEXT printnl(SB), $0
207 
	LWI(nl(SB), rSI)
208 
	JMP _doprint
209 
 
210 
/*
211 
 * Output a string to the display.
212 
 * String argument is in rSI.
213 
 */
214 
TEXT BIOSputs(SB), $0
215 
	PUSHA
216 
	CLR(rBX)
217 
_BIOSputs:
218 
	LODSB
219 
	ORB(rAL, rAL)
220 
	JEQ _BIOSputsret
221 
 
222 
	LBI(0x0E, rAH)
223 
	SYSCALL(0x10)
224 
	JMP _BIOSputs
225 
 
226 
_BIOSputsret:
227 
	POPA
228 
	RET
229 
 
230 
/*
231 
 * Output a register to the display.
232 
 */
233 
TEXT printAX(SB), $0
234 
	PUSHW(rAX)
235 
	PUSHW(rBX)
236 
	PUSHW(rCX)
237 
	PUSHW(rDI)
238 
 
239 
	LWI(4, rCX)
240 
	LWI(numbuf+4(SB), rSI)
241 
 
242 
_nextchar:
243 
	DEC(rSI)
244 
	MW(rAX, rBX)
245 
	ANDI(0x000F, rBX)
246 
	ADDI(0x30, rBX)	/* 0x30 = '0' */
247 
	CMPI(0x39, rBX)	/* 0x39 = '9' */
248 
	JLE _dowrite
249 
	ADDI(0x07, rBX)	/* 0x07 = 'A'-(1+'9')*/
250 
 
251 
_dowrite:
252 
	SXB(rBL, 0, xSI)
253 
	SHRI(4, rAX)
254 
 
255 
	DEC(rCX)
256 
	JNE _nextchar
257 
 
258 
	LWI(numbuf(SB), rSI)
259 
	CALL(BIOSputs(SB))
260 
 
261 
	POPW(rDI)
262 
	POPW(rCX)
263 
	POPW(rBX)
264 
	POPW(rAX)
265 
 
266 
	CALL(printspace(SB))
267 
	RET
268 
 
269 
TEXT printDXAX(SB), $0
270 
	PUSHW(rAX)
271 
	MW(rDX, rAX)
272 
	CALL(printAX(SB))
273 
	POPW(rAX)
274 
	CALL(printAX(SB))
275 
	RET
276 
 
277 
TEXT printBX(SB), $0
278 
	PUSHW(rAX)
279 
	MW(rBX, rAX)
280 
	CALL(printAX(SB))
281 
	POPW(rAX)
282 
	RET
283 
 
284 
/*
285 
 * Output some number of words to the display
286 
 * rDS:rDI - buffer
287 
 * rCX: number of words
288 
 */
289 
TEXT printbuf(SB), $0
290 
	PUSHW(rAX)
291 
	PUSHW(rBX)
292 
	PUSHW(rCX)
293 
 
294 
_nextword:
295 
	LXW(0, xBX, rAX)
296 
	CALL(printAX(SB))
297 
	INC(rBX)
298 
	INC(rBX)
299 
	DEC(rCX)
300 
	JNE _nextword
301 
 
302 
	POPW(rCX)
303 
	POPW(rBX)
304 
	POPW(rAX)
305 
	RET
306 
 
307 
TEXT error(SB), $0
308 
	BYTE $'E';
309 
 
310 
TEXT ioerror(SB), $0
311 
	BYTE $'I';
312 
 
313 
TEXT nl(SB), $0
314 
	BYTE $'\r';
315 
	BYTE $'\n';
316 
	BYTE $'\z';
317 
 
318 
TEXT numbuf(SB), $0
319 
	BYTE $'X'; BYTE $'X'; BYTE $'X'; BYTE $'X';
320 
	BYTE $'\z';
321 
 
322 
TEXT space(SB), $0
323 
	BYTE $' ';
324 
	BYTE $'\z';
325 
 
326 
TEXT sharp(SB), $0
327 
	BYTE $'#'; BYTE $'\z';