* Copyright (c) 1990 The Regents of the University of California.
* This code is derived from software contributed to Berkeley by
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* must display the following acknowledgement:
* This product includes software developed by the University of
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* @(#)fdbootblk.c 7.2 (Berkeley) 5/4/91
* Written 10/6/90 by William F. Jolitz
* Initial block boot for AT/386 with typical stupid NEC controller
* Goal is to read in sucessive 7.5Kbytes of bootstrap to
* No attempt is made to handle disk errors.
/*#include "/sys/i386/isa/isa.h"
#include "/sys/i386/isa/fdreg.h"*/
#define NOP inb $0x84,%al
#define start RELOC+0x400
/* mumbo-jumbo to pacify DOS, in the hope of getting diskcopy to work */
.byte
1 # sectors per allocation
.word
15 # additional sectors for bootstrap
.word
0 # number of DOS fat sectors
.word
0 # number of DOS rootdir entries
.byte
0xf0 # media descriptor
.word
0 # number of sectors per a DOS fat entry
.word
18 # number of sectors per track
.word
2 # number of heads
.long 0 # number of hidden sectors
.long 2880-18 # logical sectors per volume
.ascii
"Release 0.1" # volume label
/* step 0 force descriptors to bottom of address space */
.byte
0xb8,0x30,0x00 /* mov $0x30,%ax */
.byte
0xbc,0x00,0x01 /* mov $0x100,%sp */
/* obtain BIOS parameters for hard disk XXX */
movb $
0x9f,%ah
/* write to 0x9ff00 XXX */
.byte
0xf, 0xb4, 0x36 ; .word
0x41*4 /* lfs 0x41*4, %si */
.byte
0xf, 0xb4, 0x36 ; .word
0x46*4 /* lfs 0x46*4, %si */
/* step 1 load new descriptor table */
.byte
0x2E,0x0F,1,0x16 /* word aword cs lgdt GDTptr */
.word BIOSRELOC
+0xa4 #GDTptr
/* step 2 turn on protected mode */
/* step 3 reload segment descriptors */
ljmp $
0x8,$ BIOSRELOC
+0xb3 /* would be nice if .-RELOC+0x7c00 worked */
/* Global Descriptor Table contains three descriptors:
* 0x08: Code: code segment starts at 0 and extents for 4 gigabytes
* 0x10: Data: data segment starts at 0 and extends for 4 gigabytes
NullDesc
: .word
0,0,0,0 # null descriptor - not used
CodeDesc
: .word
0xFFFF # limit at maximum: (bits 15:0)
.byte
0,0,0 # base at 0: (bits 23:0)
.byte
0x9f # present/priv level 0/code/conforming/readable
.byte
0xcf # page granular/default 32-bit/limit(bits 19:16)
.byte
0 # base at 0: (bits 31:24)
DataDesc
: .word
0xFFFF # limit at maximum: (bits 15:0)
.byte
0,0,0 # base at 0: (bits 23:0)
.byte
0x93 # present/priv level 0/data/expand-up/writeable
.byte
0xcf # page granular/default 32-bit/limit(bits 19:16)
.byte
0 # base at 0: (bits 31:24)
/* Global Descriptor Table pointer
* contains 6-byte pointer information for LGDT
GDTptr
: .word
0x17 # limit to three 8 byte selectors(null,code,data)
.long BIOSRELOC
+0x8c # GDT -- arrgh, gas again!
readcmd
: .byte
0xe6,0,0,0,0,2,18,0x1b,0xff
/* step 4 relocate to final bootstrap address. */
/* step 5 load remaining 15 sectors off disk */
movb $
0x20,%al
# do a eoi
/* Set read/write bytes */
movb $
0x0c,%dl
# outb(0xC,0x46); outb(0xB,0x46);
movb $
0x04,%dl
# outb(0x4, addr);
movb
%ch
,%al
# outb(0x4, addr>>8);
rorl $
8,%ecx
# outb(0x81, addr>>16);
movb $
0x05,%dl
# outb(0x5, 0);
movb $
2,%al
# outb(0x5,2);
movb $
2,%al
# outb(0x0A,2);
/* issue read command to fdc */
/* watch the icu looking for an interrupt signalling completion */
movb $
0x20,%al
# do a eoi
/* extract the status bytes after the read. must we do this? */
addw $
0x200,%edi
# next addr to load to
/* for clever bootstrap, dig out boot unit and cylinder */
/* fd controller is major device 2 */
/* sorry, no flags at this point! */
call
%eax
/* main (dev, unit, off) */
/* remaining space usable for a disk label */
.word
0xaa55 /* signature -- used by BIOS ROM */
ebootblk
: /* MUST BE EXACTLY 0x200 BIG FOR SURE */