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WebSVN – planix.SVN – Blame – /os/branches/feature_tlsv12/sys/src/boot/pc/pbsdebug.s – Rev 2

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/*
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 
	SBPB(rDL, Xdrive)		/* save the boot drive */
95 
 
96 
	/* VMware starts us at 7C0:0.  Move to 0:7C00 */
97 
	PUSHR(rAX)
98 
	LWI(_nxt(SB), rAX)
99 
	PUSHR(rAX)
100 
	BYTE $0xCB	/* FAR RET */
101 
 
102 
TEXT _nxt(SB), $0
103 
	STI
104 
	LWI(confidence(SB), rSI)	/* for that warm, fuzzy feeling */
105 
	CALL16(BIOSputs(SB))
106 
 
107 
	CALL16(dreset(SB))
108 
 
109 
_jmp00:
110 
	LW(_volid(SB), rAX)		/* Xrootlo */
111 
	LW(_volid+2(SB), rDX)		/* Xroothi */
112 
 
113 
	LWI(_magic+DIROFF(SB), rBX)
114 
	CALL16(BIOSread(SB))		/* read the root directory */
115 
 
116 
	CALL16(printnl(SB))
117 
	LWI(_magic+DIROFF(SB), rBX)
118 
	LWI((512/2), rCX)
119 
	CALL16(printbuf(SB))
120 
 
121 
xloop:
122 
	JMP xloop
123 
 
124 
 
125 
TEXT buggery(SB), $0
126 
	LWI(error(SB), rSI)
127 
	CALL16(BIOSputs(SB))
128 
 
129 
TEXT quietbuggery(SB), $0
130 
xbuggery:
131 
	JMP xbuggery
132 
 
133 
/*
134 
 * Read a sector from a disc. On entry:
135 
 *   rDX:rAX	sector number
136 
 *   rES:rBX	buffer address
137 
 * For BIOSCALL(0x13):
138 
 *   rAH	0x02
139 
 *   rAL	number of sectors to read (1)
140 
 *   rCH	low 8 bits of cylinder
141 
 *   rCL	high 2 bits of cylinder (7-6), sector (5-0)
142 
 *   rDH	head
143 
 *   rDL	drive
144 
 *   rES:rBX	buffer address
145 
 */
146 
TEXT BIOSread(SB), $0
147 
	LWI(5, rDI)			/* retry count (ATAPI ZIPs suck) */
148 
_retry:
149 
	PUSHA				/* may be trashed by BIOSCALL */
150 
	PUSHR(rBX)
151 
 
152 
	LW(_trksize(SB), rBX)
153 
	LW(_nheads(SB), rDI)
154 
	IMUL(rDI, rBX)
155 
	OR(rBX, rBX)
156 
	JZ _ioerror
157 
 
158 
_okay:
159 
	DIV(rBX)			/* cylinder -> rAX, track,sector -> rDX */
160 
 
161 
	MW(rAX, rCX)			/* save cylinder */
162 
	ROLI(0x08, rCX)			/* swap rC[HL] */
163 
	SHLBI(0x06, rCL)		/* move high bits up */
164 
 
165 
	MW(rDX, rAX)
166 
	CLR(rDX)
167 
	LW(_trksize(SB), rBX)
168 
 
169 
	DIV(rBX)			/* head -> rAX, sector -> rDX */
170 
 
171 
	INC(rDX)			/* sector numbers are 1-based */
172 
	ANDI(0x003F, rDX)		/* should not be necessary */
173 
	OR(rDX, rCX)
174 
 
175 
	MW(rAX, rDX)
176 
	SHLI(0x08, rDX)			/* form head */
177 
	LBPB(Xdrive, rDL)		/* form drive */
178 
 
179 
	POPR(rBX)
180 
	LWI(0x0201, rAX)		/* form command and sectors */
181 
	BIOSCALL(0x13)			/* CF set on failure */
182 
	JCC _BIOSreadret
183 
 
184 
	POPA
185 
	DEC(rDI)			/* too many retries? */
186 
	JEQ _ioerror
187 
 
188 
	CALL16(dreset(SB))
189 
	JMP _retry
190 
 
191 
_ioerror:
192 
	LWI(ioerror(SB), rSI)
193 
	CALL16(BIOSputs(SB))
194 
	JMP xbuggery
195 
 
196 
_BIOSreadret:
197 
	POPA
198 
	RET
199 
 
200 
TEXT dreset(SB), $0
201 
	PUSHA
202 
	CLR(rAX)			/* rAH == 0 == reset disc system */
203 
	LBPB(Xdrive, rDL)
204 
	BIOSCALL(0x13)
205 
	ORB(rAH, rAH)			/* status (0 == success) */
206 
	POPA
207 
	JNE _ioerror
208 
	RET
209 
 
210 
TEXT printsharp(SB), $0
211 
	LWI(sharp(SB), rSI)
212 
_doprint:
213 
	CALL16(BIOSputs(SB))
214 
	RET
215 
 
216 
TEXT printspace(SB), $0
217 
	LWI(space(SB), rSI)
218 
	JMP _doprint
219 
 
220 
TEXT printnl(SB), $0
221 
	LWI(nl(SB), rSI)
222 
	JMP _doprint
223 
 
224 
/*
225 
 * Output a string to the display.
226 
 * String argument is in rSI.
227 
 */
228 
TEXT BIOSputs(SB), $0
229 
	PUSHA
230 
	CLR(rBX)
231 
_BIOSputs:
232 
	LODSB
233 
	ORB(rAL, rAL)
234 
	JEQ _BIOSputsret
235 
 
236 
	LBI(0x0E, rAH)
237 
	BIOSCALL(0x10)
238 
	JMP _BIOSputs
239 
 
240 
_BIOSputsret:
241 
	POPA
242 
	RET
243 
 
244 
/*
245 
 * Output a register to the display.
246 
 */
247 
TEXT printAX(SB), $0
248 
	PUSHW(rAX)
249 
	PUSHW(rBX)
250 
	PUSHW(rCX)
251 
	PUSHW(rDI)
252 
 
253 
	LWI(4, rCX)
254 
	LWI(numbuf+4(SB), rSI)
255 
 
256 
_nextchar:
257 
	DEC(rSI)
258 
	MW(rAX, rBX)
259 
	ANDI(0x000F, rBX)
260 
	ADDI(0x30, rBX)	/* 0x30 = '0' */
261 
	CMPI(0x39, rBX)	/* 0x39 = '9' */
262 
	JLE _dowrite
263 
	ADDI(0x07, rBX)	/* 0x07 = 'A'-(1+'9')*/
264 
 
265 
_dowrite:
266 
	SXB(rBL, 0, xSI)
267 
	SHRI(4, rAX)
268 
 
269 
	DEC(rCX)
270 
	JNE _nextchar
271 
 
272 
	LWI(numbuf(SB), rSI)
273 
	CALL16(BIOSputs(SB))
274 
 
275 
	POPW(rDI)
276 
	POPW(rCX)
277 
	POPW(rBX)
278 
	POPW(rAX)
279 
 
280 
	CALL16(printspace(SB))
281 
	RET
282 
 
283 
TEXT printDXAX(SB), $0
284 
	PUSHW(rAX)
285 
	MW(rDX, rAX)
286 
	CALL16(printAX(SB))
287 
	POPW(rAX)
288 
	CALL16(printAX(SB))
289 
	RET
290 
 
291 
TEXT printBX(SB), $0
292 
	PUSHW(rAX)
293 
	MW(rBX, rAX)
294 
	CALL16(printAX(SB))
295 
	POPW(rAX)
296 
	RET
297 
 
298 
/*
299 
 * Output some number of words to the display
300 
 * rDS:rDI - buffer
301 
 * rCX: number of words
302 
 */
303 
TEXT printbuf(SB), $0
304 
	PUSHW(rAX)
305 
	PUSHW(rBX)
306 
	PUSHW(rCX)
307 
 
308 
_nextword:
309 
	LXW(0, xBX, rAX)
310 
	CALL16(printAX(SB))
311 
	INC(rBX)
312 
	INC(rBX)
313 
	DEC(rCX)
314 
	JNE _nextword
315 
 
316 
	POPW(rCX)
317 
	POPW(rBX)
318 
	POPW(rAX)
319 
	RET
320 
 
321 
TEXT error(SB), $0
322 
	BYTE $'E';
323 
 
324 
TEXT ioerror(SB), $0
325 
	BYTE $'I';
326 
 
327 
TEXT nl(SB), $0
328 
	BYTE $'\r';
329 
	BYTE $'\n';
330 
	BYTE $'\z';
331 
 
332 
TEXT numbuf(SB), $0
333 
	BYTE $'X'; BYTE $'X'; BYTE $'X'; BYTE $'X';
334 
	BYTE $'\z';
335 
 
336 
TEXT space(SB), $0
337 
	BYTE $' ';
338 
	BYTE $'\z';
339 
 
340 
TEXT sharp(SB), $0
341 
	BYTE $'#'; BYTE $'\z';
342 
 
343 
TEXT confidence(SB), $0
344 
	BYTE $'P'; BYTE $'\z'