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1.1 nbrk 1: #
2: # Copyright (c) 2005, Kohsuke Ohtani
3: # All rights reserved.
4: #
5: # Redistribution and use in source and binary forms, with or without
6: # modification, are permitted provided that the following conditions
7: # are met:
8: # 1. Redistributions of source code must retain the above copyright
9: # notice, this list of conditions and the following disclaimer.
10: # 2. Redistributions in binary form must reproduce the above copyright
11: # notice, this list of conditions and the following disclaimer in the
12: # documentation and/or other materials provided with the distribution.
13: # 3. Neither the name of the author nor the names of any co-contributors
14: # may be used to endorse or promote products derived from this software
15: # without specific prior written permission.
16: #
17: # THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
18: # ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19: # IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20: # ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
21: # FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
22: # DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
23: # OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
24: # HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
25: # LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
26: # OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
27: # SUCH DAMAGE.
28: #
29:
30: #
31: # mkboot.S - DOS utility to install boot sector into disk
32: #
33: # Usage: mkboot [drive]
34: # ex. mkboot a:
35: #
36: # Read image file "bootsect.bin" and write it to disk.
37: # Current boot sector is automatically saved as file "bootsect.dbg".
38: #
39: # Prerequisite: Correct BIOS Parameter Block (BPB) has already stored
40: # in the target disk device. Generally, this data is written by a format tool.
41: #
42: .code16
43: .text
44: .align 1
45:
46: #
47: # Entry point
48: #
49: main:
50: movw %cs, %ax
51: movw %ax, %ds
52: movw %ax, %es
53: cld
54:
55: call get_drive # Get drive information
56: jc dos_exit
57:
58: call read_file # Read boot sector file
59: jc dos_exit
60:
61: call read_bsec # Read actual boot sector
62: jc dos_exit
63:
64: call store_bpb # Copy BPB data
65: jc dos_exit
66:
67: # cmp $1, dbg_mode
68: # je skip_write
69:
70: call write_bsec # Write boot sector
71: jc dos_exit
72: skip_write:
73:
74: call debug_file # Put to file for debug
75: movw $msg_ok, %dx
76: call puts
77:
78: dos_exit:
79: movb $0x4c, %ah # Return to DOS
80: int $0x21
81: ret
82:
83: #
84: # Get specified drive
85: #
86: get_drive:
87: pushw %es
88: pushaw
89:
90: movb $0x62, %ah # Get DOS PSP
91: int $0x21
92:
93: movw %bx, %es
94: movb %es:(0x80), %al # Get parameter size
95: cmpb $0, %al # No parameter ?
96: je invalid_arg
97:
98: movb %es:(0x82), %al # Get drive character
99: cmpb $0x41, %al # A ?
100: jb invalid_arg
101: cmpb $0x5a, %al # Z ?
102: ja chk_low
103: subb $0x41, %al # - A
104: jmp drive_ok
105:
106: chk_low:
107: cmpb $0x61, %al # a ?
108: jb invalid_arg
109: cmpb $0x7a, %al # z ?
110: ja invalid_arg
111: subb $0x61, %al # - a
112:
113: drive_ok:
114: cmpb $2, %al
115: jb skip_verify
116:
117: movw $err_dbg, %dx
118: pushw %ax
119: call puts
120: movb $1, dbg_mode
121: popw %ax
122:
123: skip_verify:
124: movb %al, drive
125:
126: movb $0, phys_drive
127: cmp $2, %al
128: jb not_hdd
129: movb $0x80, phys_drive
130: not_hdd:
131: popaw
132: popw %es
133: clc
134: ret
135:
136: invalid_arg:
137: popaw
138: popw %es
139: movw $msg_usage, %dx
140: call puts
141: stc
142: ret
143:
144: #
145: # puts
146: #
147: puts:
148: movb $0x09, %ah
149: int $0x21
150: ret
151:
152: #
153: # Read file
154: #
155: read_file:
156: pushaw
157: movw $bsec_name, %dx
158: movb $0x3d, %ah # Open file
159: movb $0x80, %al
160: int $0x21
161: jc error_read
162:
163: movw %ax, %bx
164: movw $tmpSect, %dx
165: movw 512, %cx
166: movb $0x3f, %ah # Read file
167: int $0x21
168: jc error_read
169:
170: mov $0x3e, %ah # Close file
171: int $0x21
172:
173: movw $tmpSect, %bx
174: movw 510(%bx), %ax
175: cmpw $0xaa55, %ax
176: jne error_file
177: popaw
178: clc
179: ret
180:
181: error_file:
182: movw $err_bad_file, %dx
183: call puts
184: popaw
185: stc
186: ret
187:
188: error_read:
189: movw $err_not_found, %dx
190: call puts
191: popaw
192: stc
193: ret
194:
195: #
196: # Read boot sector image from disk
197: #
198: read_bsec:
199: pushaw
200: movw 5, %cx
201: retry_loop:
202: pushw %cx
203:
204: movw $dos_packet, %bx # bx = buffer address
205: movw $orgSect, %ax
206: movw %ax, 6(%bx)
207: movw %cs, %ax
208: movw %ax, 8(%bx)
209: movl $0, (%bx) # Sector = 0
210: movw $1, 4(%bx) # Num of sector = 1
211: movb drive, %al # al = drive number
212: movw $0xffff, %cx # Extended call
213: int $0x25
214: popw %ax
215:
216: popw %cx
217: jnc read_ok
218: loopw retry_loop
219:
220: movw $err_read, %dx
221: call puts
222: stc
223: read_ok:
224: popaw
225: ret
226:
227:
228: #
229: # Write boot sector image to disk
230: #
231: write_bsec:
232: pushaw
233: movw $dos_packet, %bx # bx = buffer address
234: movw $tmpSect, %ax
235: movw %ax, 6(%bx)
236: movw %cs, %ax
237: movw %ax, 8(%bx)
238: movl $0, (%bx) # Sector = 0
239: movw $1, 4(%bx) # Num of sector = 1
240: movb drive, %al # al = drive number
241: movw $0xffff, %cx # Extended call
242: int $0x26
243: popw %ax
244:
245: jnc write_ok
246:
247: movw $err_write, %dx
248: call puts
249: popaw
250: stc
251: write_ok:
252: popaw
253: ret
254:
255: #
256: # Store BPB from current disk BPB
257: #
258: store_bpb:
259: cld
260: movw $orgSect, %si
261: addw $3, %si # Skip jump instruction
262: addw $8, %si # Skip OEM ID
263: movw $tmpSect, %di
264: addw $3, %di
265: addw $8, %di
266: movw $0x33, %cx # Copy disk parameter
267: rep
268: movsb
269:
270: ### movw $tmpSect, %di # Update physical drive
271: ### addw $0x24, %di
272: ### movb phys_drive, %al
273: ### movb %al, (%di)
274:
275: clc
276: ret
277:
278: #
279: # Create new BPB file for debug
280: #
281: debug_file:
282: movw $dbg_name, %dx
283: movb $0x3c, %ah # Create file
284: movw $0, %cx
285: int $0x21
286: jc exit_debug
287:
288: movw %ax, %bx
289: movw $tmpSect, %dx
290: movw $512, %cx
291: movb $0x40, %ah # Read file
292: int $0x21
293: jc exit_debug
294:
295: movb $0x3e, %ah # Close file
296: int $0x21
297:
298: exit_debug:
299: ret
300:
301: #
302: # Data
303: #
304: drive: .byte 0
305: phys_drive: .byte 0
306: dbg_mode: .byte 0
307:
308: .align 4
309: dos_packet:
310: .long 0 # Sector
311: .word 1 # Number of sector
312: .word 0 # Buffer offset
313: .word 0 # Buffer segment
314:
315: bsec_name: .asciz "bootsect.bin"
316: dbg_name: .asciz "bootsect.dbg"
317:
318: msg_usage: .ascii "mkboot [drive]"
319: .byte 0xd,0xa,0x24
320: msg_ok: .ascii "System transferred"
321: .byte 0xd,0xa,0x24
322: err_dbg: .ascii "Warning: Write to HDD!"
323: .byte 0xd,0xa,0x24
324: err_not_found: .ascii "Error: bootsect.bin was not found"
325: .byte 0xd,0xa,0x24
326: err_bad_file: .ascii "Error: bootsect.bin is not valid"
327: .byte 0xd,0xa,0x24
328: err_read: .ascii "Error: Disk read errror"
329: .byte 0xd,0xa,0x24
330: err_write: .ascii "Error: Disk write errror"
331: .byte 0xd,0xa,0x24
332:
333: .align 16
334: orgSect: .fill 512,1,0
335: tmpSect: .fill 512,1,0
336: