# # 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: boot0.s,v 1.4 1998/10/19 19:13:53 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 TBL0SZ,0x3 # Table 0 size .set TBL1SZ,0xa # Table 1 size .set _NXTDRV,-0x47 # Drive number .set _OPT,-0x46 # Default option .set _FLAG,-0x45 # Flags .set _TICKS,-0x44 # Timeout ticks .set _FAKE,0x10 # Fake partition entry .set _MNUOPT,0x1c # Menu options .globl start # Entry point start: cld # String ops inc xorl %eax,%eax # Zero movl %eax,%es # Address movl %eax,%ds # data movl %eax,%ss # Set up movwir(LOAD,_sp) # stack movl %esp,%esi # Source movwir(start,_di) # Destination movwir(0x100,_cx) # Word count rep # Relocate movsl # code movl %edi,%ebp # Address variables movb $0x10,%cl # Words to clear rep # Zero stosl # them incb1(-0xe,_di_) # Sector number jmpnwi(main-LOAD+ORIGIN) # To relocated code main: movbr1(_dl,_FAKE,_bp_) # Save drive number callwi(putn) # To new line movwir(partbl,_bx) # Partition table xorl %edx,%edx # Item main.1: movbr0(_dh,_bx_) # Mark inactive movb1r(0x4,_bx_,_al) # Load type movwir(tables,_di) # Lookup tables movb $TBL0SZ,%cl # Entries repne # Exclude scasb # partition? je main.3 # Yes movb $TBL1SZ,%cl # Entries repne # Known scasb # type? jne main.2 # No addwir(TBL1SZ,_di) # Adjust main.2: movb0r(_di_,_cl) # Partition addl %ecx,%edi # description callwi(putx) # Display it main.3: addwir(0x10,_bx) # Next entry incl %edx # Next item cmpb $0x4,%dl # Done? jb main.1 # No movb1r(_FAKE,_bp_,_al) # Drive number subb $0x80-0x1,%al # Does next cmpbmr(NHRDRV,_al) # drive exist? jb main.4 # Yes decb %al # Already drive 0? jz main.5 # Yes xorb %al,%al # Drive 0 main.4: addb $'0'|0x80,%al # Save movbr1(_al,_NXTDRV,_bp_) # it movwir(drive,_di) # Display callwi(putx) # item main.5: movwir(prompt,_si) # Display callwi(putstr) # prompt movb1r(_OPT,_bp_,_dl) # Display decl %esi # default callwi(putkey) # key xorb %ah,%ah # BIOS: Get int $0x1a # system time movl %edx,%edi # Save main.6: movb $0x1,%ah # BIOS: Check int $0x16 # for keypress jnz main.9 # Have one xorb %ah,%ah # BIOS: Get int $0x1a # system time subl %edi,%edx # Elapsed time cmpw1r(_TICKS,_bp_,_dx) # Timeout? jb main.6 # No main.7: movb1r(_OPT,_bp_,_al) # Load default jmp main.10 # Join common code main.8: movb $0x7,%al # Signal callwi(putchr) # error main.9: xorb %ah,%ah # BIOS: Get int $0x16 # keypress movb %ah,%al # Scan code cmpb $0x1c,%al # Enter pressed? je main.7 # No subb $0x3b,%al # Less F1 scan code cmpb $0x4,%al # F1..F5? ja main.8 # No main.10: cwtl # Option btwr1(_ax,_MNUOPT,_bp_) # enabled? jnc main.8 # No movwir(FAKE,_si) # Partition entry movb1r(_NXTDRV,_bp_,_dl) # Next drive subb $'0',%dl # number cmpb $0x4,%al # F5 pressed? je main.11 # Yes movb0r(_si_,_dl) # Drive number movbr1(_al,_OPT,_bp_) # Save option shlb $0x4,%al # Point to addwia(partbl) # partition xchgl %esi,%eax # entry tstbi1(0x40,_FLAG,_bp_) # No updates? jnz main.11 # Yes movbi0(0x80,_si_) # Flag active pushl %esi # Save xchgl %esi,%eax # Fake partition entry movwir(start,_bx) # Data to write movwir(0x301,_ax) # Write sector callwi(intx13) # to disk popl %esi # Restore 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? jne main.8 # No movwir(crlf,_si) # Leave some callwi(puts) # space jmp *%ebx # Invoke bootstrap # Display routines putkey: movb $'F',%al # Display callwi(putchr) # 'F' movb $'1',%al # Prepare addb %dl,%al # digit jmp putstr.1 # Display the rest putx: btswr1(_dx,_MNUOPT,_bp_) # Enable menu option movwir(item,_si) # Display callwi(putkey) # key movl %edi,%esi # Display the rest puts: callwi(putstr) # Display string putn: movwir(crlf,_si) # To next line putstr: lodsb # Get byte testb $0x80,%al # End of string? jnz putstr.2 # Yes putstr.1: callwi(putchr) # Display char jmp putstr # Continue putstr.2: andb $~0x80,%al # Clear MSB putchr: pushl %ebx # Save movwir(0x7,_bx) # Page:attribute movb $0xe,%ah # BIOS: Display int $0x10 # character popl %ebx # Restore ret # To caller # Disk I/O routine intx13: cli # Disable interrupts movb1r(0x1,_si_,_dh) # Load head movw1r(0x2,_si_,_cx) # Load cylinder:sector o16 # Load movw1r(0x8,_si_,_di) # offset movwir(break,_si) # Packet pointer movbi0(0x10,_si_) # Packet size movbr1(_al,0x2,_si_) # Block count movwr1(_bx,0x4,_si_) # Transfer movws1(_es,0x6,_si_) # buffer o16 # LBA movwr1(_di,0x8,_si_) # address sti # Enable interrupts tstbi1(0x80,_FLAG,_bp_) # Try for extensions? jz intx13.1 # No orb $0x40,%ah # Use disk packet decl %eax # Verify off intx13.1: int $0x13 # BIOS: Disk I/O ret # To caller # Menu strings item: .ascii " "; .byte ' '|0x80 prompt: .ascii "\nDefault:"; .byte ' '|0x80 crlf: .ascii "\r"; .byte '\n'|0x80 # Partition type tables tables: .byte 0x0, 0x5, 0xf .byte 0x1, 0x4, 0x6, 0xb, 0xc, 0xe, 0x63, 0x83 .byte 0xa5, 0xa6 .byte os_misc-. # Unknown .byte os_dos-. # DOS .byte os_dos-. # DOS .byte os_dos-. # DOS .byte os_dos-. # Windows .byte os_dos-. # Windows .byte os_dos-. # Windows .byte os_unix-. # UNIX .byte os_linux-. # Linux .byte os_freebsd-. # FreeBSD .byte os_bsd-. # OpenBSD os_misc: .ascii "?"; .byte '?'|0x80 os_dos: .ascii "DO"; .byte 'S'|0x80 os_unix: .ascii "UNI"; .byte 'X'|0x80 os_linux: .ascii "Linu"; .byte 'x'|0x80 os_freebsd: .ascii "Free" os_bsd: .ascii "BS"; .byte 'D'|0x80 .org PRT_OFF-0xb,0x90 drive: .ascii "Drive " drvnum: .byte 0x0 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