diff options
Diffstat (limited to 'sys/boot/i386/boot2/boot1.S')
| -rw-r--r-- | sys/boot/i386/boot2/boot1.S | 250 |
1 files changed, 250 insertions, 0 deletions
diff --git a/sys/boot/i386/boot2/boot1.S b/sys/boot/i386/boot2/boot1.S new file mode 100644 index 0000000..b84ddf3 --- /dev/null +++ b/sys/boot/i386/boot2/boot1.S @@ -0,0 +1,250 @@ +# +# Copyright (c) 1998 Robert Nordier +# All rights reserved. +# +# Redistribution and use in source and binary forms are freely +# permitted provided that the above copyright notice and this +# paragraph and the following disclaimer are duplicated in all +# such forms. +# +# This software is provided "AS IS" and without any express or +# implied warranties, including, without limitation, the implied +# warranties of merchantability and fitness for a particular +# purpose. +# + +# $Id:$ + + .set MEM_REL,0x600 # Relocation address + .set MEM_ARG,0x800 # Arguments + .set MEM_PKT,0x810 # Disk packet + .set MEM_ORG,0x7c00 # Origin + .set MEM_BUF,0x8c00 # Load area + .set MEM_BTX,0x9000 # BTX start + .set MEM_JMP,0x9010 # BTX entry point + .set MEM_USR,0xa000 # Client start + + .set PRT_OFF,0x1be # Partition offset + .set PRT_NUM,0x4 # Partitions + .set PRT_BSD,0xa5 # Partition type + + .set SIZ_PAG,0x1000 # Page size + .set SIZ_SEC,0x200 # Sector size + + .globl start + .globl xread + +start: jmp main # Start recognizably + + .org 0x4,0x90 + +xread: pushl %cs # Address + popl %ds # data +xread.1: movwir(MEM_PKT,_si) # Packet + movbr1(_al,0x2,_si_) # Blocks to read + o16 # Transfer + movwr1(_bx,0x4,_si_) # buffer + o16 # LBA + movwr1(_cx,0x8,_si_) # address + callwi(read) # Read from disk + lret # To caller + +main: cld # String ops inc + xorl %eax,%eax # Zero + movl %ax,%es # Address + movl %ax,%ds # data + movl %ax,%ss # Set up + movwir(start,_sp) # stack + movl %esp,%esi # Source + movwir(MEM_REL,_di) # Destination + movwir(0x100,_cx) # Word count + rep # Copy + movsl # code + movb $0x10,%cl # Words to clear + rep # Zero + stosl # them + movbi1(0x10,-0x10,_di_) # Set packet size + cmpb $0x80,%dl # Hard drive? + jb main.4 # No + movwir(part4,_si) # Read master + movb $0x1,%al # boot + callwi(nread) # record + xorl %eax,%eax # Pass number +main.1: movwir(MEM_BUF+PRT_OFF,_si) # Partition table + movb $0x1,%dh # Partition +main.2: cmpbi1(PRT_BSD,0x4,_si_) # Our partition type? + jne main.3 # No + tstbi0(0x80,_si_) # Active? + jnz main.5 # Yes + testb %al,%al # Second pass? + jnz main.5 # Yes +main.3: addl $0x10,%esi # Next entry + incb %dh # Partition + cmpb $0x1+PRT_NUM,%dh # Done? + jb main.2 # No + incl %eax # Pass + cmpb $0x2,%al # Done? + jb main.1 # No + movwir(msg_part,_si) # Message + jmp error # Error +main.4: xorl %edx,%edx # Partition:drive + movwir(part4,_si) # Partition pointer +main.5: movwrm(_dx,MEM_ARG) # Save args + movb $0x10,%al # Sector count + callwi(nread) # Read disk + movwir(MEM_BTX,_bx) # BTX + movw1r(0xa,_bx_,_si) # Point past + addl %ebx,%esi # it + movwir(MEM_USR+SIZ_PAG,_di) # Client page 1 + movwir(MEM_BTX+0xd*SIZ_SEC,_cx) # Byte + subl %esi,%ecx # count + rep # Relocate + movsb # client + subl %edi,%ecx # Byte count + xorb %al,%al # Zero + rep # assumed + stosb # bss + callwi(seta20) # Enable A20 + jmpnwi(start+MEM_JMP-MEM_ORG) # Start BTX + +# Enable A20 + +seta20: inb $0x64,%al # Get status + testb $0x2,%al # Busy? + jnz seta20 # Yes + movb $0xd1,%al # Command: Write + outb %al,$0x64 # output port +seta20.1: inb $0x64,%al # Get status + testb $0x2,%al # Busy? + jnz seta20.1 # Yes + movb $0xdf,%al # Enable + outb %al,$0x60 # A20 + ret # To caller + +# Read from disk + +nread: xorw %bx,%bx # Transfer + movb $MEM_BUF>>0x8,%bh # buffer + o16 # LBA + movw1r(0x8,_si_,_cx) # address + pushl %cs # Read from + callwi(xread.1) # disk + jnc return # If success + movwir(msg_read,_si) # Message + +# Error exit + +error: callwi(putstr) # Display message + movwir(msg_boot,_si) # Display + callwi(putstr) # prompt + xorb %ah,%ah # BIOS: Get + int $0x16 # keypress + int $0x19 # BIOS: Reboot + +# Display string + +putstr.0: movwir(0x7,_bx) # Page:attribute + movb $0xe,%ah # BIOS: Display + int $0x10 # character +putstr: lodsb # Get char + testb %al,%al # End of string? + jne putstr.0 # No + +return: ret # Generic return + +# Read from disk + +read: testb %dh,%dh # Try for extensions? + jz read.3 # No + movwir(0x55aa,_bx) # Magic + pushl %edx # Save + movb $0x41,%ah # BIOS: Check + int $0x13 # extensions present + popl %edx # Restore + jc read.3 # If error + cmpwir(0xaa55,_bx) # Magic? + jne read.3 # No + testb $0x1,%cl # Packet interface? + jz read.3 # No + movb $0x42,%ah # BIOS: Extended + int $0x13 # read + ret # To caller + +read.1: movb $0x1,%ah # Invalid + stc # parameter +read.2: ret # To caller + +read.3: pushl %edx # Save + movb $0x8,%ah # BIOS: Get drive + int $0x13 # parameters + movb %dh,%ch # Max head number + popl %edx # Restore + jc read.2 # If error + andb $0x3f,%cl # Sectors per track + jz read.1 # If zero + o16 # Get + movw1r(0x8,_si_,_ax) # LBA + pushl %edx # Save + movzbw %cl,%bx # Divide by + xorw %dx,%dx # sectors + divw %bx,%ax # per track + movb %ch,%bl # Max head number + movb %dl,%ch # Sector number + incl %ebx # Divide by + xorb %dl,%dl # number of + divw %bx,%ax # heads + movb %dl,%bh # Head number + popl %edx # Restore + o16 # Cylinder number + cmpl $0x3ff,%eax # supportable? + ja read.1 # No + xchgb %al,%ah # Set up cylinder + rorb $0x2,%al # number + orb %ch,%al # Merge + incl %eax # sector + xchgl %eax,%ecx # number + movb %bh,%dh # Head number + subb %ah,%al # Sectors this track + movb1r(0x2,_si_,_ah) # Blocks to read + cmpb %ah,%al # To read + jb read.4 # this + movb %ah,%al # track +read.4: movwir(0x5,_bp) # Try count +read.5: lesw1r(0x4,_si_,_bx) # Transfer buffer + pushl %eax # Save + movb $0x2,%ah # BIOS: Conventional + int $0x13 # read + popl %ebx # Restore + jnc read.6 # If success + decl %ebp # Retry? + jz read.7 # No + xorb %ah,%ah # BIOS: Reset + int $0x13 # disk system + movl %ebx,%eax # Block count + jmp read.5 # Continue +read.6: movzbw %bl,%ax # Sectors read + o16 # Adjust + addwr1(_ax,0x8,_si_) # LBA, + shlb %bl # buffer + addbr1(_bl,0x5,_si_) # pointer, + subbr1(_al,0x2,_si_) # block count + ja read.3 # If not done +read.7: ret # To caller + +# Messages + +msg_read: .asciz "Read error" +msg_part: .asciz "No bootable partition" +msg_boot: .asciz "\r\nHit return to reboot: " + + .org PRT_OFF,0x90 + +# Partition table + + .fill 0x30,0x1,0x0 +part4: .byte 0x80, 0x00, 0x01, 0x00 + .byte 0xa5, 0xff, 0xff, 0xff + .byte 0x00, 0x00, 0x00, 0x00 + .byte 0x50, 0xc3, 0x00, 0x00 + + .word 0xaa55 # Magic number |
