Date: Mon, 19 Apr 2004 12:56:38 -0400 From: John Baldwin <jhb@FreeBSD.org> To: obrien@FreeBSD.org Cc: cvs-all@FreeBSD.org Subject: Re: cvs commit: src/sys/boot/i386/boot0 boot0ext.s src/sys/boot/i386/boot0ext Makefile Message-ID: <200404191256.38119.jhb@FreeBSD.org> In-Reply-To: <20040418190408.GA68131@dragon.nuxi.com> References: <200403261846.i2QIkVuT063179@repoman.freebsd.org> <200403311543.59571.jhb@FreeBSD.org> <20040418190408.GA68131@dragon.nuxi.com>
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--Boundary-00=_GTAhA9QyODzJCyf Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline On Sunday 18 April 2004 03:04 pm, David O'Brien wrote: > On Wed, Mar 31, 2004 at 03:43:59PM -0500, John Baldwin wrote: > > Also, the 2 sector boot0 does start up and > > then load the larger version of itself as you suggest above. > > Since http://perforce.freebsd.org is dead, and getting a randome single > file out of perforce is a total farse; could you please email me your > latest 2-sector boot0.s? > > thanks, Attached. It lives in the relatively small jhb_boot branch, btw, so you could add something like: //depot/user/jhb/boot/sys/boot/i386/boot0/... //obrien_foo/boot0/... to your client view to just get the boot0 directory. -- John Baldwin <jhb@FreeBSD.org> <>< http://www.FreeBSD.org/~jhb/ "Power Users Use the Power to Serve" = http://www.FreeBSD.org --Boundary-00=_GTAhA9QyODzJCyf Content-Type: application/octet-stream; name="boot0.s" Content-Transfer-Encoding: 7bit Content-Disposition: attachment; filename="boot0.s" # # 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. # # $FreeBSD: src/sys/boot/i386/boot0/boot0.s,v 1.29 2003/12/11 20:40:12 jhb Exp $ # A 1024-byte boot manager. .set NHRDRV,0x475 # Number of hard drives .set ORIGIN,0x600 # Execution address .set SECTOR_SIZE,0x200 # Length of a sector .set NUM_SECTORS,2 # Total length in sectors .set FAKE,ORIGIN+(SECTOR_SIZE*NUM_SECTORS) # Partition entry .set LOAD,0x7c00 # Load address .set PRT_OFF,0x1be # Partition table .set TBL0SZ,table0_end-table0 # Table 0 size .set TBL1SZ,table1_end-table1 # 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 KEY_1,0x02 # #1 key scan code # # Flag bits # .set FL_PACKET,0x80 # Packet mode .set FL_NOUPDATE,0x40 # Don't save selection .set FL_SETDRV,0x20 # Override drive number # # Addresses in the sector of embedded data values. # Accessed with negative offsets from the end of the relocated sectors (%bp). # .set _PRT_END,(FAKE-(ORIGIN+SECTOR_SIZE*(NUM_SECTORS-1))) .set _NXTDRV,-(_PRT_END+0x48) # Next drive .set _OPT,-(_PRT_END+0x47) # Default option .set _SETDRV,-(_PRT_END+0x46) # Drive to force .set _FLAGS,-(_PRT_END+0x45) # Flags .set _TICKS,-(_PRT_END+0x44) # Timeout ticks .set _FAKE,0x0 # Fake partition entry .set _MNUOPT,0xc # Menu options .globl start # Entry point .code16 # This runs in real mode # # Initialise segments and registers to known values. # segments start at 0. # The stack is immediately below the address we were loaded to. # # Note that this section of code is used as the first signature check in # boot0cfg(8). # start: cld # String ops inc xorw %ax,%ax # Zero movw %ax,%es # Address movw %ax,%ds # data movw %ax,%ss # Set up movw $LOAD,%sp # stack # # End signature code # # # Set address for variable space beyond code, and clear it. # Notice that this is also used to point to the values embedded in the block, # by using negative offsets. # movw $fake,%bp # Address variables movw %bp,%di # %di used in stosw movw $0x8,%cx # Words to clear rep # Zero stosw # them incb -0xe(%di) # Sector number 1 # # Check what flags were loaded with us; specifically, use a predefined Drive. # If what the bios gives us is bad, use the '0' in the block instead, as well. # testb $FL_SETDRV,LOAD+flags-start # Set number drive? jnz boot.1 # Yes testb %dl,%dl # Drive number valid? js boot.2 # Possibly (0x80 set) boot.1: movb LOAD+setdrv-start,%dl # Drive number to use boot.2: # # Reload all of boot0 (including the extra sectors) into memory at the # relocation address. # push %dx # Save drive number movw $start,%bx # Origin we were linked for movw %bp,%si # Fake PTE movw $0x200+NUM_SECTORS,%ax # Read in all callw intx13 # of boot0 pop %dx # Restore # # Relocate to the new copy of the code. # jmp main+ORIGIN-LOAD # To relocated code # # Whatever we decided to use, now store it into the fake # partition entry that lives in the data space above us. # main: movb %dl,_FAKE(%bp) # Save drive number callw putn # To new line pushw %dx # Save drive number # # Start out with a pointer to the 4th byte of the first table entry # so that after 4 iterations it's beyond the end of the sector. # and beyond a 256 byte boundary and has overflowed 8 bits (see next comment). # (remember that the table starts 2 bytes earlier than you would expect # as the bootable flag is after it in the block) # movw $(partbl+0x4),%bx # Partition table (+4) xorw %dx,%dx # Item number # # Loop around on the partition table, printing values until we # pass a 256 byte boundary. The end of loop test is at main.5. # main.3: movb %ch,-0x4(%bx) # Zero active flag (ch == 0) btw %dx,_FLAGS(%bp) # Entry enabled? jnc main.5 # No # # If any of the entries in the table are # the same as the 'type' in the slice table entry, # then this is an empty or non bootable partition. Skip it. # movb (%bx),%al # Load type movw $tables,%di # Lookup tables movb $TBL0SZ,%cl # Number of entries repne # Exclude scasb # partition? je main.5 # Yes # # Now scan the table of known types # movb $TBL1SZ,%cl # Number of entries repne # Known scasb # type? jne main.4 # No # # If it matches get the matching element in the # next array. If it doesn't, we are already # pointing at its first element which points to a "?". # addw $TBL1SZ,%di # Adjust main.4: movb (%di),%cl # Partition addw %cx,%di # description callw putx # Display it main.5: incw %dx # Next item addb $0x10,%bl # Next entry jnc main.3 # Till done # # Passed a 256 byte boundary.. # table is finished. # Add one to the drive number and check it is valid, # popw %ax # Drive number subb $0x80-0x1,%al # Does next cmpb NHRDRV,%al # drive exist? (from BIOS?) jb main.6 # Yes # If not then if there is only one drive, # Don't display drive as an option. # decw %ax # Already drive 0? jz main.7 # Yes # If it was illegal or we cycled through them, # then go back to drive 0. # xorb %al,%al # Drive 0 # # Whatever drive we selected, make it an ascii digit and save it back # to the "next drive" location in the loaded block in case we # want to save it for next time. # This also is part of the printed drive string so add 0x80 to indicate # end of string. # main.6: addb $'0'|0x80,%al # Save next movb %al,_NXTDRV(%bp) # drive number movw $drive,%di # Display callw putx # item # # Now that we've printed the drive (if we needed to), display a prompt. # Get ready for the input by noting the time. # main.7: movw $prompt,%si # Display callw putstr # prompt movb _OPT(%bp),%dl # Display decw %si # default callw putkey # key xorb %ah,%ah # BIOS: Get int $0x1a # system time movw %dx,%di # Ticks when addw _TICKS(%bp),%di # timeout # # Busy loop, looking for keystrokes but # keeping one eye on the time. # main.8: movb $0x1,%ah # BIOS: Check int $0x16 # for keypress jnz main.11 # Have one xorb %ah,%ah # BIOS: Get int $0x1a # system time cmpw %di,%dx # Timeout? jb main.8 # No # # If timed out or defaulting, come here. # main.9: movb _OPT(%bp),%al # Load default jmp main.12 # Join common code # # User's last try was bad, beep in displeasure. # Since nothing was printed, just continue on as if the user # hadn't done anything. This gives the effect of the user getting a beep # for all bad keystrokes but no action until either the timeout # occurs or the user hits a good key. # main.10: movb $0x7,%al # Signal callw putchr # error # # Get the keystroke. # main.11: xorb %ah,%ah # BIOS: Get int $0x16 # keypress movb %ah,%al # Scan code # # If it's CR act as if timed out. # cmpb $KEY_ENTER,%al # Enter pressed? je main.9 # Yes # # Otherwise check if legal # If not ask again. # subb $KEY_F1,%al # Less F1 scan code cmpb $0x4,%al # F1..F5? jna main.12 # Yes subb $(KEY_1 - KEY_F1),%al # Less #1 scan code cmpb $0x4,%al # #1..#5? ja main.10 # No # # We have a selection. # but if it's a bad selection go back to complain. # The bits in MNUOPT were set when the options were printed. # Anything not printed is not an option. # main.12: cbtw # Option btw %ax,_MNUOPT(%bp) # enabled? jnc main.10 # No # # Save the info in the original tables # for rewriting to the disk. # movb %al,_OPT(%bp) # Save option movw $fake,%si # Partition for write movb (%si),%dl # Drive number movw %si,%bx # Partition for read cmpb $0x4,%al # F5/#5 pressed? pushf # Save je main.13 # Yes shlb $0x4,%al # Point to addw $partbl,%ax # selected xchgw %bx,%ax # partition movb $0x80,(%bx) # Flag active # # If not asked to do a write-back (flags 0x40) don't do one. # main.13: pushw %bx # Save testb $FL_NOUPDATE,_FLAGS(%bp) # Skip update? jnz main.14 # Yes movw $start,%bx # Data to write movw $0x301,%ax # Write 1 sector callw intx13 # to disk main.14: popw %si # Restore popf # Restore # # If going to next drive, replace drive with selected one. # Remember to un-ascii it. Hey 0x80 is already set, cool! # jne main.15 # If not F5/#5 movb _NXTDRV(%bp),%dl # Next drive subb $'0',%dl # number # # load selected bootsector to the LOAD location in RAM. # If it fails to read or isn't marked bootable, treat it # as a bad selection. # main.15: movw $LOAD,%bx # Address for read movw $0x201,%ax # Read 1 sector callw intx13 # from disk jc main.10 # If error cmpw $MAGIC,0x1fe(%bx) # Bootable? jne main.10 # No callw putn # Leave some space jmp *%bx # Invoke bootstrap # # Display routines # putkey: movb $'F',%al # Display callw putchr # 'F' movb $'1',%al # Prepare addb %dl,%al # digit jmp putstr.1 # Display the rest # # Display the option and note that it is a valid option. # That last point is a bit tricky.. # putx: btsw %dx,_MNUOPT(%bp) # Enable menu option movw $item,%si # Display callw putkey # key movw %di,%si # Display the rest puts: callw putstr # Display string putn: movw $crlf,%si # To next line putstr: lodsb # Get byte testb $0x80,%al # End of string? jnz putstr.2 # Yes putstr.1: callw putchr # Display char jmp putstr # Continue putstr.2: andb $~0x80,%al # Clear MSB putchr: pushw %bx # Save movw $0x7,%bx # Page:attribute movb $0xe,%ah # BIOS: Display int $0x10 # character popw %bx # Restore retw # To caller # One-sector disk I/O routine # # Calling conventions: (assumes %si -> partition table entry) # # 0x1(%si) - byte - head # 0x2(%si) - word - cylinder/sector # 0x8(%si) - long - LBA to use if needed # %ah - byte - operation, 2 = read, 3 = write # %al - byte - sector count # %dl - byte - drive number # %es:(%bx) - void - buffer to use for transfer # # If the head == 0xff, and cylinder/sector == 0xffff, then try # to use the EDD stuff with the LBA offset instead of CHS. However, # use CHS if at all possible. intx13: movb 0x1(%si),%dh # Load head movw 0x2(%si),%cx # Load cylinder:sector pushw %si # Save movw %sp,%di # Save cmpb $0xff,%dh # Might we need LBA? jne intx13.2 # No, just use CHS cmpw $0xffff,%cx # Do we need LBA? jne intx13.2 # No testb $FL_PACKET,_FLAGS(%bp) # Try the packet interface? jz intx13.2 # No pushw %cx # Save pushw %bx # Save movw $0x55aa,%bx # Magic pushw %ax # Save movb $0x41,%ah # BIOS: EDD extensions int $0x13 # present? popw %ax # Restore jc intx13.1 # Not present, use CHS cmpw $0xaa55,%bx # Magic? jne intx13.1 # Not present, use CHS testb $0x1,%cl # Packet mode available? jz intx13.1 # No, use CHS orb $0x40,%ah # Use disk packet intx13.1: popw %bx # Restore popw %cx # Restore testb $0x40,%ah # Using packet mode? jz intx13.2 # No, so skip the rest pushl $0x0 # Set the pushl 0x8(%si) # LBA address pushw %es # Set the transfer pushw %bx # buffer address push $0x0 # Punch a hole in the stack push $0x10 # Packet size movw %sp,%si # Packet pointer xchgb %al,0x2(%si) # Set the block count in the # packet and zero %al, # turning verify off for writes intx13.2: int $0x13 # BIOS: Disk I/O movw %di,%sp # Restore popw %si # Restore retw # To caller .org PRT_OFF-0xe,0x90 # # These values are sometimes changed before writing back to the drive # Be especially careful that nxtdrv: must come after drive:, as it # is part of the same string. # # Note that the 'drive' string variable is used as the second signature # check in boot0cfg(8). # version_minor: .byte 0x1 # minor version version_major: .byte 0x1 # major version drive: .ascii "Drive " nxtdrv: .byte 0x0 # Next drive number opt: .byte 0x0 # Option setdrv: .byte 0x80 # Drive to force flags: .byte FLAGS # Flags ticks: .word TICKS # Delay # # here is the 64 byte partition table that fdisk would fiddle with. # partbl: .fill 0x40,0x1,0x0 # Partition table .word MAGIC # Magic number # # start of sector two.. ugh # .org SECTOR_SIZE,0x90 # Menu strings item: .ascii " "; .byte ' '|0x80 prompt: .ascii "\nDefault:"; .byte ' '|0x80 crlf: .ascii "\r"; .byte '\n'|0x80 # Partition type tables tables: # # These entries identify invalid or NON BOOT types and partitions. # table0: .byte 0x0, 0x5, 0xf table0_end: # # These values indicate bootable types we know the names of # table1: .byte 0x1, 0x4, 0x6, 0x7, 0xb, 0xc, 0xe, 0x42, 0x63, 0x83 .byte 0x9f, 0xa5, 0xa6, 0xa9 table1_end: # # These are offsets that match the known names above and point to the strings # that will be printed. # .byte os_misc-. # Unknown .byte os_dos-. # DOS .byte os_dos-. # DOS .byte os_dos-. # DOS .byte os_nt-. # NT/XP or OS/2 .byte os_windows-. # Windows 32-bit FAT .byte os_windows-. # Windows 32-bit FAT ext int 13 .byte os_windows-. # Windows .byte os_windows-. # Windows 2000 dyn ext .byte os_unix-. # UNIX .byte os_linux-. # Linux .byte os_bsdos-. # BSD/OS .byte os_freebsd-. # FreeBSD .byte os_openbsd-. # OpenBSD .byte os_netbsd-. # NetBSD # # And here are the strings themselves. 0x80 or'd into a byte indicates # the end of the string. (not so great for Russians but...) # os_misc: .ascii "Unknow"; .byte 'n'|0x80 os_dos: .ascii "Do"; .byte 's'|0x80 os_nt: .ascii "Windows NT/X"; .byte 'P'|0x80 os_windows: .ascii "Window"; .byte 's'|0x80 os_unix: .ascii "UNI"; .byte 'X'|0x80 os_linux: .ascii "Linu"; .byte 'x'|0x80 os_freebsd: .ascii "FreeBS"; .byte 'D'|0x80 os_openbsd: .ascii "OpenBS"; .byte 'D'|0x80 os_netbsd: .ascii "NetBS"; .byte 'D'|0x80 os_bsdos: .ascii "BSD/O"; .byte 'S'|0x80 # # Fake partition entry created at the end of the table used when loading # boot0 at the very beginning and when loading an MBR from another disk when # F5 is pressed. # .org SECTOR_SIZE*NUM_SECTORS, 0x0 fake: --Boundary-00=_GTAhA9QyODzJCyf--
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