2 * Copyright (c) 2007 Yahoo!, Inc.
4 * Written by: John Baldwin <jhb@FreeBSD.org>
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
9 * 1. Redistributions of source code must retain the above copyright
10 * notice, this list of conditions and the following disclaimer.
11 * 2. Redistributions in binary form must reproduce the above copyright
12 * notice, this list of conditions and the following disclaimer in the
13 * documentation and/or other materials provided with the distribution.
14 * 3. Neither the name of the author nor the names of any co-contributors
15 * may be used to endorse or promote products derived from this software
16 * without specific prior written permission.
18 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
19 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
20 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
21 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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24 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
25 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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32 * Partly from: src/sys/boot/i386/boot2/boot1.S 1.31
35 /* Memory Locations */
36 .set MEM_REL,0x700 # Relocation address
37 .set MEM_ARG,0x900 # Arguments
38 .set MEM_ORG,0x7c00 # Origin
39 .set MEM_BUF,0x8cec # Load area
40 .set MEM_BTX,0x9000 # BTX start
41 .set MEM_JMP,0x9010 # BTX entry point
42 .set MEM_USR,0xa000 # Client start
43 .set BDA_BOOT,0x472 # Boot howto flag
46 .set SIZ_PAG,0x1000 # Page size
47 .set SIZ_SEC,0x200 # Sector size
48 .set COPY_BLKS,0x8 # Number of blocks
49 # to copy for boot2 (<= 15)
50 .set COPY_BLK_SZ,0x8000 # Copy in 32k blocks; must be
51 # a multiple of 16 bytes
57 * Copy BTX and boot2 to the right locations and start it all up.
61 * Setup the segment registers to flat addressing (segment 0) and setup the
62 * stack to end just below the start of our code.
64 start: xor %cx,%cx # Zero
68 mov $start,%sp # stack
71 * BTX is right after us at 'end'. We read the length of BTX out of
72 * its header to find boot2. We need to copy boot2 to MEM_USR and BTX
73 * to MEM_BTX. Since those might overlap, we have to copy boot2
74 * backwards first and then copy BTX. We aren't sure exactly how long
75 * boot2 is, but it's currently under 256kB so we'll copy 8 blocks of 32kB
76 * each; this can be adjusted via COPY_BLK and COPY_BLK_SZ above.
79 mov 0xa(%bx),%si # Get BTX length and set
80 add %bx,%si # %si to start of boot2
81 dec %si # Set %ds:%si to point at the
82 mov %si,%ax # last byte we want to copy
83 shr $4,%ax # from boot2, with %si made as
84 add $(COPY_BLKS*COPY_BLK_SZ/16),%ax # small as possible.
87 mov $MEM_USR/16,%ax # Set %es:(-1) to point at
88 add $(COPY_BLKS*COPY_BLK_SZ/16),%ax # the last byte we
89 mov %ax,%es # want to copy boot2 into.
90 mov $COPY_BLKS,%bx # Copy COPY_BLKS 32k blocks
92 add $COPY_BLK_SZ,%si # Adjust %ds:%si to point at
93 mov %ds,%ax # the end of the next 32k to
94 sub $COPY_BLK_SZ/16,%ax # copy from boot2
96 mov $COPY_BLK_SZ-1,%di # Adjust %es:%di to point at
97 mov %es,%ax # the end of the next 32k into
98 sub $COPY_BLK_SZ/16,%ax # which we want boot2 copied
100 mov $COPY_BLK_SZ,%cx # Copy 32k
105 mov %cx,%ds # Reset %ds and %es
108 mov 0xa(%bx),%cx # Get BTX length and set
109 mov %bx,%si # %si to end of BTX
110 mov $MEM_BTX,%di # %di -> end of BTX at
111 add %cx,%si # MEM_BTX
118 * Enable A20 so we can access memory above 1 meg.
119 * Use the zero-valued %cx as a timeout for embedded hardware which do not
120 * have a keyboard controller.
122 seta20: cli # Disable interrupts
123 seta20.1: dec %cx # Timeout?
125 inb $0x64,%al # Get status
126 testb $0x2,%al # Busy?
128 movb $0xd1,%al # Command: Write
129 outb %al,$0x64 # output port
130 seta20.2: inb $0x64,%al # Get status
131 testb $0x2,%al # Busy?
133 movb $0xdf,%al # Enable
135 seta20.3: sti # Enable interrupts
138 * Save drive number from BIOS so boot2 can see it and start BTX.
141 jmp start+MEM_JMP-MEM_ORG # Start BTX