Turbo Assembler Version 3.1 11/14/95 18:41:36 Page 1
boot.ASM
1 ; BOOTEASY, version 1.7.
2 ; Developed from BOOTANY, with many improvements.
3 ; The main idea was to simplify the installation
4 ; procedure and to remove unnecessary partition type switching.
5 ; Second hard disk switching added.
6 ; Author: Serge Vakulenko, <vak@kiae.su>
7
8 =003B F1_scancode equ 59 ; scancode of 'F1' key
9 =001C Enter_scancode equ 28 ; scancode of 'Enter' key
10 =0005 Timeout equ 5 ; wait up to 5 seconds for reply
11
12 =7C00 StdBase equ 7c00h ; address where DOS loads us
13 =0600 Base equ 600h ; address where we rewrite itself
14 =01BE Partab equ 1beh ; partition table offset
15 =0475 NumDisks equ 475h ; number of disk drives (BIOS data area)
16
17 =0000 BootIndicator equ 0 ; partition record: boot indicator
18 =0001 BeginHead equ 1 ; first partition sector: head number
19 =0002 BeginSector equ 2 ; sector and cylinder
20 =0004 SystemId equ 4 ; system type
21
22 ; -------------------------------
23
24 0000 dummy segment at 0
25 assume cs:dummy
26 org Base ; address where we rewrite itself
27 0600 BaseEntry:
28 org StdBase ; address where DOS loads us
29 7C00 StdBaseEntry:
30 7C00 dummy ends
31
32 ; -------------------------------
33
34 0000 code segment
35 assume cs:code, ds:code, es:code, ss:code
36 org 0
37 0000 Boot:
38 ;
39 ; Setup the stack and segment registers
40 ;
41 0000 33 C0 xor AX,AX ; Zero register
42 0002 8E C0 mov ES,AX ; ES := 0
43 0004 8E D8 mov DS,AX ; DS := 0
44 0006 8E D0 mov SS,AX ; disables intrs up to the next command
45 0008 BC 7C00 mov SP,StdBase ; SP at 7c00
46 ;
47 ; DOS loads this pgm at 0000:7C00. Any boot routine
48 ; we call also expects to execute there so the first
49 ; exercise is to move this code somewhere else.
50 ;
51 000B FC cld ; Clear direction
52 000C 8B F4 mov SI,SP ; Copy from 7c00h...
53 000E BF 0600 mov DI,Base ; ...to 600h...
54 0011 B9 0100 mov CX,256 ; ...512 bytes, or 256 words
55 0014 F2> A5 repne movsw ; Move itself to new location
56
57 0016 EA 00000667sr jmp FAR PTR BaseEntry+(Entry-Boot)
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boot.ASM
58
59 ; -------------------------------
60 ;
61 ; A valid function key was depressed (or defaulted)
62 ; Attempt to boot the corresponding partition.
63 ;
64 001B Load:
65 001B 8B D5 mov DX,BP ; restore drive number
66 001D 58 pop AX ; key '1'..'5'
67 001E A2 074Fr mov Base+default,AL ; save function key number
68 0021 3C 35 cmp AL,'5'
69 0023 74 23 je SwitchDrive
70 0025 B4 10 mov AH,16
71 0027 F6 E4 mul AH ; AX = key * 16
72 0029 05 04AE add AX,Base+Partab-'1'*16 ; subtract '1'
73 002C 8B F0 mov SI,AX
74 ;
75 ; Check if the partition is empty.
76 ;
77 002E 80 7C 04 00 cmp BYTE PTR SystemId[SI],0
78 0032 74 44 je Menu ; Empty - display menu again
79 0034 80 7C 04 05 cmp BYTE PTR SystemId[SI],05h
80 0038 74 3E je Menu ; DOS extended type - never load
81
82 003A C6 04 80 mov BYTE PTR BootIndicator[SI],80h ; Mark partition as bootable
83 003D E8 00DA call SaveBoot
84 ;
85 ; Read in and validate the partition's boot sector.
86 ;
87 0040 8A 74 01 mov DH,BeginHead[SI] ; head from partition table
88 0043 8B 4C 02 mov CX,BeginSector[SI]
89 0046 EB 08 jmp loadboot
90 ;
91 ; Read in the boot sector from second disk.
92 ;
93 0048 SwitchDrive:
94 0048 E8 00CF call SaveBoot
95 004B B9 0001 mov CX,0001h ; cylinder 0, sector 1
96 004E 32 D1 xor DL,CL ; (DL ^= 1) switch drive
97 0050 loadboot:
98 0050 BB 7C00 mov BX,StdBase ; ES already == 0
99 0053 B8 0201 mov AX,0201h ; function, # of sectors
100 0056 CD 13 int 13h ; read system boot record
101 0058 72 1E jc Menu ; exit if error
102 005A 81 BF 01FE AA55 cmp WORD PTR 510[BX],0aa55h ; test signature
103 0060 75 16 jne Menu ; reprompt if invalid
104 ;
105 ; Jump to secondary boot.
106 ; DL now contains boot disk number (80h or 81h);
107 ; ES:SI contains the address of partition table
108 ; entry to boot.
109 ;
110 0062 EA 00007C00sr jmp FAR PTR StdBaseEntry
111
112 ; -------------------------------
113 ;
114 ; The main entry to the boot
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boot.ASM
115 ;
116 0067 Entry:
117 0067 80 FA 81 cmp DL,81h ; DL contains current drive number
118 006A 74 02 je driveok ; is it valid?
119 006C B2 80 mov DL,80h ; no - use the default value
120 006E 8B EA driveok: mov BP,DX ; save the drive number
121 0070 42 inc DX ; 80h -> 81h, 81h -> 82h
122 0071 80 F2 B3 xor DL,80h+'3' ; 80h -> '2', 81h -> '1'
123 0074 88 16 0741r mov Base+diskNum,DL
124 ;
125 ; Display the menu
126 ;
127 0078 Menu:
128 0078 BF 07BE mov DI,Base+Partab ; set index
129 007B B9 0004 mov CX,4 ; set loop count
130 007E C6 06 0734r 31 mov Base+key,'1' ; set key number in message
131 0083 32 F6 xor DH,DH ; count of partitions
132 0085 menuloop:
133 0085 88 2D mov BYTE PTR BootIndicator[DI],CH ; Clear active flag
134 0087 8A 45 04 mov AL,SystemId[DI]
135 008A 3C 00 cmp AL,0 ; unused partition?
136 008C 74 23 je next
137 008E 3C 05 cmp AL,5 ; extended DOS partition?
138 0090 74 1F je next
139 0092 FE C6 inc DH ; increment partition count
140
141 0094 BE 0731r lea SI,Base+FkeyMsg ; get msg addr
142 0097 E8 0071 call Output
143
144 009A BE 074Fr lea SI,Base+nameTable-2
145 009D nameloop:
146 009D 46 inc SI
147 009E 46 inc SI
148 009F 8B 1C mov BX,[SI]
149 00A1 0A FF or BH,BH
150 00A3 74 05 je endnameloop
151 00A5 32 7D 04 xor BH,SystemId[DI]
152 00A8 75 F3 jne nameloop
153 00AA endnameloop:
154 00AA 8D B7 077Br lea SI,Base+namtab[BX]
155 00AE E8 005A call Output
156 00B1 next:
157 00B1 83 C7 10 add DI,16 ; next entry address
158 00B4 FE 06 0734r inc Base+key
159 00B8 E2 CB loop menuloop
160
161 00BA 80 3E 0475 02 cmp BYTE PTR DS:NumDisks,2 ; is the second disk present?
162 00BF 74 0B je have2disks ; have disk 2
163
164 00C1 BE 0742r lea SI,Base+defaultMsg ; prepare 'Default' message
165 00C4 0A F6 or DH,DH ; no disk 2; do we have valid partitions?
166 00C6 75 0A jne prompt ; several partitions, wait for reply
167
168 00C8 CD 18 int 18h ; no partitions, load ROM basic
169 00CA EB AC jmp Menu ; repeat, if no ROM basic
170 00CC have2disks:
171 00CC BE 0731r lea SI,Base+FkeyMsg ; print 'F5'
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boot.ASM
172 00CF E8 0039 call Output ; now SI points to "disk 2\nDefault..."
173 00D2 prompt:
174 00D2 E8 0036 call Output ; print 'Default' message
175 00D5 reprompt:
176 00D5 32 E4 xor AH,AH ; GetTickCount
177 00D7 CD 1A int 1ah ; BiosTimerService
178 00D9 8B DA mov BX,DX ; lo-order tick count
179 00DB 83 C3 60 add BX,192*Timeout/10 ; timeout value in ticks
180 ;
181 ; Get the reply
182 ;
183 00DE waitkey:
184 00DE B4 01 mov AH,1 ; keyboard status
185 00E0 CD 16 int 16h ; keybd bios service
186 00E2 B4 00 mov AH,0 ; GetTickCount
187 00E4 75 0B jnz reply ; jump if reply
188 00E6 CD 1A int 1ah ; BiosTimerService
189 00E8 3B D3 cmp DX,BX ; check for timeout
190 00EA 72 F2 jb waitkey ; wait for scancode
191 00EC loaddefault:
192 00EC A0 074Fr mov AL,Base+default ; prior system id
193 00EF EB 0A jmp testkey ; boot default system
194 00F1 reply:
195 00F1 CD 16 int 16h ; AH=0, keybd bios service
196 00F3 8A C4 mov AL,AH ; Copy to AL
197 00F5 3C 1C cmp AL,Enter_scancode
198 00F7 74 F3 je loaddefault
199 00F9 04 F6 add AL,'1'-F1_scancode ; Turn into index
200 00FB testkey:
201 00FB 3C 31 cmp AL,'1' ; max Function key
202 00FD 72 D6 jb reprompt ; Invalid code check
203 00FF 3C 35 cmp AL,'5' ; max Function key
204 0101 77 D2 jnbe reprompt ; if not F1..F5, branch
205 0103 50 push AX
206
207 0104 BE 072Fr lea SI,Base+newLine ; new line
208 0107 BB 061Br lea BX,Base+Load
209 010A 53 push BX ; call Output; jmp Load
210
211 ; -------------------------------
212 ;
213 ; Output line [SI] to screen, end of line marked with 80h
214 ;
215 010B Output:
216 010B FC cld ; reset direction flag
217 010C AC lodsb ; load argument from string
218 010D 50 push AX ; save byte
219 010E 24 7F and AL,7fh ; insure valid character
220 0110 B4 0E mov AH,14 ; write tty
221 0112 CD 10 int 10h ; bios video service
222 0114 58 pop AX ; restore byte
223 0115 A8 80 test AL,80h ; test for end of string
224 0117 74 F2 jz Output ; do until end of string
225 0119 C3 ret ; return to caller
226
227 ; -------------------------------
228 ;
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boot.ASM
229 ; Save boot block default partition settings
230 ;
231 011A SaveBoot:
232 011A 56 push SI
233 011B B8 0301 mov AX,0301h ; write sector
234 011E BB 0600 mov BX,Base ; ES already == 0
235 0121 B9 0001 mov CX,0001h ; cylinder 0, sector 1
236 0124 32 F6 xor DH,DH ; drive #, head 0
237 0126 CD 13 int 13h ; replace boot record
238 0128 5E pop SI
239 0129 C6 06 074Fr 3F mov Base+default,'?' ; reset default
240 012E C3 ret
241
242 ; -------------------------------
243
244 012F 0D 8A newLine db 13,10+80h
245 0131 0D 0A 46 FkeyMsg db 13,10,'F'
246 0134 30 20 2E 20 2E 20 2E+ key db '0 . . .',' '+80h,'disk '
247 A0 64 69 73 6B 20
248 0141 31 diskNum db '1'
249 0142 0D 0A 0A 44 65 66 61+ defaultMsg db 13,10,10,'Default: F'
250 75 6C 74 3A 20 46
251 014F 3F A0 default db '?',' '+80h
252
253 0151 00 01 nameTable db dos -namtab, 1
254 0153 00 04 db dos -namtab, 4
255 0155 00 06 db dos -namtab, 6
256 0157 03 07 db hpfs -namtab, 7
257 0159 07 0A db os2 -namtab, 0Ah
258 015B 0A 63 db unix -namtab, 63h
259 015D 0E 64 db novell -namtab, 64h
260 015F 0E 65 db novell -namtab, 65h
261 0161 14 80 db minix -namtab, 80h
262 0163 19 81 db linux -namtab, 81h
263 0165 19 82 db linux -namtab, 82h
264 0167 19 83 db linux -namtab, 83h
265 0169 1E 93 db amoeba -namtab, 93h
266 016B 24 A5 db freebsd -namtab, 0A5h
267 016D 2B 9F db bsdi -namtab, 9fh
268 016F 2F 75 db pcix -namtab, 75h
269 0171 33 52 db cpm -namtab, 52h
270 0173 33 DB db cpm -namtab, 0dbh
271 0175 36 40 db venix -namtab, 40h
272 0177 3B F2 db dossec -namtab, 0F2h
273 0179 41 00 db noname -namtab, 0
274
275 017B namtab:
276 017B 44 6F F3 dos db 'Do','s'+80h
277 017E 48 70 66 F3 hpfs db 'Hpf','s'+80h
278 0182 4F 73 B2 os2 db 'Os','2'+80h
279 0185 55 6E 69 F8 unix db 'Uni','x'+80h
280 0189 4E 6F 76 65 6C EC novell db 'Novel','l'+80h
281 018F 4D 69 6E 69 F8 minix db 'Mini','x'+80h
282 0194 4C 69 6E 75 F8 linux db 'Linu','x'+80h
283 0199 41 6D 6F 65 62 E1 amoeba db 'Amoeb','a'+80h
284 019F 46 72 65 65 42 53 C4 freebsd db 'FreeBS','D'+80h
285 01A6 42 53 44 E9 bsdi db 'BSD','i'+80h
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boot.ASM
286 01AA 50 63 69 F8 pcix db 'Pci','x'+80h
287 01AE 43 70 ED cpm db 'Cp','m'+80h
288 01B1 56 65 6E 69 F8 venix db 'Veni','x'+80h
289 01B6 44 6F 73 73 65 E3 dossec db 'Dosse','c'+80h
290 01BC 3F BF noname db '?','?'+80h
291
292 =01BE used equ $ - Boot
293 01BE 01*(00) db (1beh - used + 1) dup (0) ; error if code too big
294 01BF 3F*(00) db 63 dup (0) ; clear rest of record
295 01FE AA55 dw 0aa55h ; magic
296
297 0200 code ends
298 end
Turbo Assembler Version 3.1 11/14/95 18:41:36 Page 7
Symbol Table
Symbol Name Type Value Cref (defined at #)
??DATE Text "11/14/95"
??FILENAME Text "boot "
??TIME Text "18:41:35"
??VERSION Number 030A
@CPU Text 0101H
@CURSEG Text CODE #24 #34
@FILENAME Text BOOT
@WORDSIZE Text 2 #24 #34
AMOEBA Byte CODE:0199 265 #283
BASE Number 0600 #13 26 53 67 72 123 128 130 141 144 154 158 164 171 192 +
207 208 234 239
BASEENTRY Near DUMMY:0600 #27 57
BEGINHEAD Number 0001 #18 87
BEGINSECTOR Number 0002 #19 88
BOOT Near CODE:0000 #37 57 292
BOOTINDICATOR Number 0000 #17 82 133
BSDI Byte CODE:01A6 267 #285
CPM Byte CODE:01AE 269 270 #287
DEFAULT Byte CODE:014F 67 192 239 #251
DEFAULTMSG Byte CODE:0142 164 #249
DISKNUM Byte CODE:0141 123 #248
DOS Byte CODE:017B 253 254 255 #276
DOSSEC Byte CODE:01B6 272 #289
DRIVEOK Near CODE:006E 118 #120
ENDNAMELOOP Near CODE:00AA 150 #153
ENTER_SCANCODE Number 001C #9 197
ENTRY Near CODE:0067 57 #116
F1_SCANCODE Number 003B #8 199
FKEYMSG Byte CODE:0131 141 171 #245
FREEBSD Byte CODE:019F 266 #284
HAVE2DISKS Near CODE:00CC 162 #170
HPFS Byte CODE:017E 256 #277
KEY Byte CODE:0134 130 158 #246
LINUX Byte CODE:0194 262 263 264 #282
LOAD Near CODE:001B #64 208
LOADBOOT Near CODE:0050 89 #97
LOADDEFAULT Near CODE:00EC #191 198
MENU Near CODE:0078 78 80 101 103 #127 169
MENULOOP Near CODE:0085 #132 159
MINIX Byte CODE:018F 261 #281
NAMELOOP Near CODE:009D #145 152
NAMETABLE Byte CODE:0151 144 #253
NAMTAB Near CODE:017B 154 253 254 255 256 257 258 259 260 261 262 263 264 265 +
266 267 268 269 270 271 272 273 #275
NEWLINE Byte CODE:012F 207 #244
NEXT Near CODE:00B1 136 138 #156
NONAME Byte CODE:01BC 273 #290
NOVELL Byte CODE:0189 259 260 #280
NUMDISKS Number 0475 #15 161
OS2 Byte CODE:0182 257 #278
OUTPUT Near CODE:010B 142 155 172 174 #215 224
PARTAB Number 01BE #14 72 128
PCIX Byte CODE:01AA 268 #286
PROMPT Near CODE:00D2 166 #173
Turbo Assembler Version 3.1 11/14/95 18:41:36 Page 8
Symbol Table
REPLY Near CODE:00F1 187 #194
REPROMPT Near CODE:00D5 #175 202 204
SAVEBOOT Near CODE:011A 83 94 #231
STDBASE Number 7C00 #12 28 45 98
STDBASEENTRY Near DUMMY:7C00 #29 110
SWITCHDRIVE Near CODE:0048 69 #93
SYSTEMID Number 0004 #20 77 79 134 151
TESTKEY Near CODE:00FB 193 #200
TIMEOUT Number 0005 #10 179
UNIX Byte CODE:0185 258 #279
USED Number 01BE #292 293
VENIX Byte CODE:01B1 271 #288
WAITKEY Near CODE:00DE #183 190
Groups & Segments Bit Size Align Combine Class Cref (defined at #)
CODE 16 0200 Para none #34 35 35 35 35
DUMMY 16 7C00 AT 0000 #24 25