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1.1 root 1: /*
2: * Ported to boot 386BSD by Julian Elischer ([email protected]) Sept 1992
3: *
4: * Mach Operating System
5: * Copyright (c) 1992, 1991 Carnegie Mellon University
6: * All Rights Reserved.
7: *
8: * Permission to use, copy, modify and distribute this software and its
9: * documentation is hereby granted, provided that both the copyright
10: * notice and this permission notice appear in all copies of the
11: * software, derivative works or modified versions, and any portions
12: * thereof, and that both notices appear in supporting documentation.
13: *
14: * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
15: * CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR
16: * ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
17: *
18: * Carnegie Mellon requests users of this software to return to
19: *
20: * Software Distribution Coordinator or [email protected]
21: * School of Computer Science
22: * Carnegie Mellon University
23: * Pittsburgh PA 15213-3890
24: *
25: * any improvements or extensions that they make and grant Carnegie Mellon
26: * the rights to redistribute these changes.
27: */
28:
29: /*
30: * HISTORY
31: * $Log: start.S,v $
32: * Revision 1.1 1993/03/21 18:08:42 cgd
33: * after 0.2.2 "stable" patches applied
34: *
35: * Revision 2.2 92/04/04 11:36:29 rpd
36: * Fix Intel Copyright as per B. Davies authorization.
37: * [92/04/03 rvb]
38: * Need to zero dh on hd path; at least for an adaptec card.
39: * [92/01/14 rvb]
40: *
41: * From 2.5 boot:
42: * Flush digit printing.
43: * Fuse floppy and hd boot by using Int 21 to tell
44: * boot type (slightly dubious since Int 21 is DOS
45: * not BIOS)
46: * [92/03/30 mg32]
47: *
48: * Revision 2.2 91/04/02 14:42:04 mbj
49: * Fix the BIG boot bug. We had missed a necessary data
50: * before a xor that was clearing a register used later
51: * as an index register.
52: * [91/03/01 rvb]
53: * Remember floppy type for swapgeneric
54: * Add Intel copyright
55: * [90/02/09 rvb]
56: *
57: */
58:
59:
60: /*
61: Copyright 1988, 1989, 1990, 1991, 1992
62: by Intel Corporation, Santa Clara, California.
63:
64: All Rights Reserved
65:
66: Permission to use, copy, modify, and distribute this software and
67: its documentation for any purpose and without fee is hereby
68: granted, provided that the above copyright notice appears in all
69: copies and that both the copyright notice and this permission notice
70: appear in supporting documentation, and that the name of Intel
71: not be used in advertising or publicity pertaining to distribution
72: of the software without specific, written prior permission.
73:
74: INTEL DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE
75: INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS,
76: IN NO EVENT SHALL INTEL BE LIABLE FOR ANY SPECIAL, INDIRECT, OR
77: CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
78: LOSS OF USE, DATA OR PROFITS, WHETHER IN ACTION OF CONTRACT,
79: NEGLIGENCE, OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION
80: WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
81: */
82: #include "asm.h"
83:
84: .file "start.s"
85:
86: BOOTSEG = 0x9000 # boot will be loaded at 640k-64k
87: BOOTSTACK = 0xe000 # boot stack
88: SIGNATURE = 0xaa55
89: LOADSZ = 14 # size of unix boot
90: PARTSTART = 0x1be # starting address of partition table
91: NUMPART = 4 # number of partitions in partition table
92: PARTSZ = 16 # each partition table entry is 16 bytes
93: BSDPART = 0xA5 # value of boot_ind, means bootable partition
94: BOOTABLE = 0x80 # value of boot_ind, means bootable partition
95:
96: .text
97:
98: ENTRY(boot1)
99:
100: # boot1 is loaded at 0x0:0x7c00
101: # ljmp to the next instruction to set up %cs
102: data32
103: ljmp $0x7c0, $start
104:
105: start:
106: # set up %ds
107: mov %cs, %ax
108: mov %ax, %ds
109:
110:
111: # set up %ss and %esp
112: data32
113: mov $BOOTSEG, %eax
114: mov %ax, %ss
115: data32
116: mov $BOOTSTACK, %esp
117:
118: /*** set up %es, (where we will load boot2 to) ***/
119: mov %ax, %es
120:
121: #ifdef DEBUG
122: data32
123: mov $one, %esi
124: data32
125: call message
126: #endif
127: # get the boot drive id
128: movb $0x33, %ah
129: movb $0x05, %al
130: int $0x21
131:
132: cmpb $0x80, %dl
133: data32
134: jge hd
135:
136: fd:
137: # reset the disk system
138: #ifdef DEBUG
139: data32
140: mov $two, %esi
141: data32
142: call message
143: #endif
144: movb $0x0, %ah
145: int $0x13
146: data32
147: mov $0x0001, %ecx # cyl 0, sector 1
148: data32
149: #ifdef DEBUG
150: data32
151: mov $three, %esi
152: data32
153: call message
154: #endif
155: jmp load
156:
157: hd: /**** load sector 0 into the BOOTSEG ****/
158: #ifdef DEBUG
159: data32
160: mov $four, %esi
161: data32
162: call message
163: #endif
164: data32
165: mov $0x0201, %eax
166: xor %ebx, %ebx # %bx = 0
167: data32
168: mov $0x0001, %ecx
169: #ifdef DEBUG
170: data32
171: mov $five, %esi
172: data32
173: call message
174: #endif
175: data32
176: andl $0xff, %edx
177: /*mov $0x0080, %edx*/
178: int $0x13
179: data32
180: jb read_error
181:
182: /***# find the bootable partition *****/
183: data32
184: mov $PARTSTART, %ebx
185: data32
186: mov $NUMPART, %ecx
187: again:
188: addr16
189: movb %es:4(%ebx), %al
190: cmpb $BSDPART, %al
191: data32
192: je found
193: data32
194: add $PARTSZ, %ebx
195: data32
196: loop again
197: data32
198: mov $enoboot, %esi
199: data32
200: jmp err_stop
201:
202:
203: /*
204: # BIOS call "INT 0x13 Function 0x2" to read sectors from disk into memory
205: # Call with %ah = 0x2
206: # %al = number of sectors
207: # %ch = cylinder
208: # %cl = sector
209: # %dh = head
210: # %dl = drive (0x80 for hard disk, 0x0 for floppy disk)
211: # %es:%bx = segment:offset of buffer
212: # Return:
213: # %al = 0x0 on success; err code on failure
214: */
215:
216: found:
217: addr16
218: movb %es:1(%ebx), %dh /* head */
219: addr16
220: xor %ecx, %ecx
221: addr16
222: movw %es:2(%ebx), %ecx /*sect,cyl (+ 2 bytes junk in top word )*/
223:
224: load:
225: movb $0x2, %ah /* function 2 */
226: movb $LOADSZ, %al /* number of blocks */
227: xor %ebx, %ebx /* %bx = 0, put it at 0 in the BOOTSEG */
228: int $0x13
229: data32
230: jb read_error
231:
232: # ljmp to the second stage boot loader (boot2).
233: # After ljmp, %cs is BOOTSEG and boot1 (512 bytes) will be used
234: # as an internal buffer "intbuf".
235:
236: #ifdef DEBUG
237: data32
238: mov $six, %esi
239: data32
240: call message
241: #endif
242: data32
243: ljmp $BOOTSEG, $EXT(boot2)
244:
245: #
246: # read_error
247: #
248:
249: read_error:
250:
251: data32
252: mov $eread, %esi
253: err_stop:
254: data32
255: call message
256: data32
257: jmp stop
258:
259: #
260: # message: write the error message in %ds:%esi to console
261: #
262:
263: message:
264: # Use BIOS "int 10H Function 0Eh" to write character in teletype mode
265: # %ah = 0xe %al = character
266: # %bh = page %bl = foreground color (graphics modes)
267:
268: data32
269: push %eax
270: data32
271: push %ebx
272: data32
273: mov $0x0001, %ebx
274: cld
275:
276: nextb:
277: lodsb # load a byte into %al
278: cmpb $0x0, %al
279: data32
280: je done
281: movb $0xe, %ah
282: int $0x10 # display a byte
283: data32
284: jmp nextb
285: done:
286: data32
287: pop %ebx
288: data32
289: pop %eax
290: data32
291: ret
292:
293: stop: hlt
294: data32
295: jmp stop # halt doesnt actually halt forever
296:
297: /* error messages */
298:
299: #ifdef DEBUG
300: one: String "1\r\n\0"
301: two: String "2\r\n\0"
302: three: String "3\r\n\0"
303: four: String "4\r\n\0"
304: five: String "5\r\n\0"
305: six: String "6\r\n\0"
306: seven: String "7\r\n\0"
307: #endif DEBUG
308: eread: String "Read error\r\n\0"
309: enoboot: String "No bootable partition\r\n\0"
310: endofcode:
311: /* throw in a partition in case we are block0 as well */
312: /* flag,head,sec,cyl,typ,ehead,esect,ecyl,start,len */
313: . = EXT(boot1) + PARTSTART
314: .byte 0x0,0,0,0,0,0,0,0
315: .long 0,0
316: .byte 0x0,0,0,0,0,0,0,0
317: .long 0,0
318: .byte 0x0,0,0,0,0,0,0,0
319: .long 0,0
320: .byte BOOTABLE,0,1,0,BSDPART,255,255,255
321: .long 0,50000
322: /* the last 2 bytes in the sector 0 contain the signature */
323: . = EXT(boot1) + 0x1fe
324: .value SIGNATURE
325: ENTRY(disklabel)
326: . = EXT(boot1) + 0x400
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