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rnordier 1998-12-05 11:58:33 +00:00
parent 97f6d04b8b
commit e625ce3562
1 changed files with 23 additions and 17 deletions
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40
sys/boot/i386/boot0/boot0.s
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@ -13,21 +13,29 @@
# purpose.
#
# $Id: boot0.s,v 1.4 1998/10/19 19:13:53 rnordier Exp $
# $Id: boot0.s,v 1.5 1998/11/29 14:09:00 rnordier Exp $
# A 512-byte boot manager.
.set LOAD,0x7c00 # Load address
.set ORIGIN,0x600 # Execution address
.set PRT_OFF,0x1be # Partition table
.set FAKE,0x810 # Partition entry
.set NHRDRV,0x475 # Number of hard drives
.set ORIGIN,0x600 # Execution address
.set DSKPKT,0x800 # Disk packet
.set FAKE,0x810 # Partition entry
.set LOAD,0x7c00 # Load address
.set PRT_OFF,0x1be # Partition table
.set TBL0SZ,0x3 # Table 0 size
.set TBL1SZ,0xa # Table 1 size
.set MAGIC,0xaa55 # Magic: bootable
.set KEY_ENTER,0x1c # Enter key scan code
.set KEY_F1,0x3b # F1 key scan code
.set _NXTDRV,-0x47 # Drive number
.set _OPT,-0x46 # Default option
.set _FLAG,-0x45 # Flags
.set _FLAGS,-0x45 # Flags
.set _TICKS,-0x44 # Timeout ticks
.set _FAKE,0x10 # Fake partition entry
.set _MNUOPT,0x1c # Menu options
@ -93,7 +101,7 @@ main.5: movwir(prompt,_si) # Display
callwi(putkey) # key
xorb %ah,%ah # BIOS: Get
int $0x1a # system time
movl %edx,%edi # Save
movl %edx,%edi # Save ticks
main.6: movb $0x1,%ah # BIOS: Check
int $0x16 # for keypress
jnz main.9 # Have one
@ -109,9 +117,9 @@ main.8: movb $0x7,%al # Signal
main.9: xorb %ah,%ah # BIOS: Get
int $0x16 # keypress
movb %ah,%al # Scan code
cmpb $0x1c,%al # Enter pressed?
cmpb $KEY_ENTER,%al # Enter pressed?
je main.7 # No
subb $0x3b,%al # Less F1 scan code
subb $KEY_F1,%al # Less F1 scan code
cmpb $0x4,%al # F1..F5?
ja main.8 # No
main.10: cwtl # Option
@ -127,7 +135,7 @@ main.10: cwtl # Option
shlb $0x4,%al # Point to
addwia(partbl) # partition
xchgl %esi,%eax # entry
tstbi1(0x40,_FLAG,_bp_) # No updates?
tstbi1(0x40,_FLAGS,_bp_) # No updates?
jnz main.11 # Yes
movbi0(0x80,_si_) # Flag active
pushl %esi # Save
@ -140,7 +148,7 @@ main.11: movwir(LOAD,_bx) # Address for read
movwir(0x201,_ax) # Read sector
callwi(intx13) # from disk
jc main.8 # If error
cmpwi2(0xaa55,0x1fe,_bx_) # Bootable?
cmpwi2(MAGIC,0x1fe,_bx_) # Bootable?
jne main.8 # No
movwir(crlf,_si) # Leave some
callwi(puts) # space
@ -184,7 +192,7 @@ intx13: cli # Disable interrupts
movw1r(0x2,_si_,_cx) # Load cylinder:sector
o16 # Load
movw1r(0x8,_si_,_di) # offset
movwir(break,_si) # Packet pointer
movwir(DSKPKT,_si) # Packet pointer
movbi0(0x10,_si_) # Packet size
movbr1(_al,0x2,_si_) # Block count
movwr1(_bx,0x4,_si_) # Transfer
@ -192,7 +200,7 @@ intx13: cli # Disable interrupts
o16 # LBA
movwr1(_di,0x8,_si_) # address
sti # Enable interrupts
tstbi1(0x80,_FLAG,_bp_) # Try for extensions?
tstbi1(0x80,_FLAGS,_bp_) # Use packet interface?
jz intx13.1 # No
orb $0x40,%ah # Use disk packet
decl %eax # Verify off
@ -235,12 +243,10 @@ os_bsd: .ascii "BS"; .byte 'D'|0x80
.org PRT_OFF-0xb,0x90
drive: .ascii "Drive "
drvnum: .byte 0x0
nxtdrv: .byte 0x0 # Next drive number
opt: .byte 0x0 # Option
flags: .byte FLAGS # Flags
ticks: .word TICKS # Delay
partbl: .fill 0x40,0x1,0x0 # Partition table
.word 0xaa55 # Magic number
break: # Uninitialized data
.word MAGIC # Magic number