--- src/sys/boot/i386/boot0/Attic/boot0.S 2004/07/18 18:26:33 1.4 +++ src/sys/boot/i386/boot0/Attic/boot0.S 2004/07/18 23:39:59 1.5 @@ -1,28 +1,27 @@ -# -# 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 1.26 2003/06/01 20:41:04 obrien Exp $ -# $DragonFly$ - -# A 512-byte boot manager. - - .set NHRDRV,0x475 # Number of hard drives - .set ORIGIN,0x600 # Execution address - .set FAKE,0x800 # Partition entry - .set LOAD,0x7c00 # Load address - +/* + * 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 1.26 2003/06/01 20:41:04 obrien Exp $ + * $DragonFly$ + */ + +#include "../bootasm.h" + + /* + * A 512-byte boot manager. + */ .set PRT_OFF,0x1be # Partition table .set TBL0SZ,0x3 # Table 0 size @@ -35,10 +34,11 @@ .set KEY_F1,0x3b # F1 key scan code .set KEY_1,0x02 # #1 key scan code -# -# Addresses in the sector of embedded data values. -# Accessed with negative offsets from the end of the relocated sector (%ebp). -# + /* + * Addresses in the sector of embedded data values. Accessed + * with negative offsets from the end of the relocated sector + * (%ebp). + */ .set _NXTDRV,-0x48 # Next drive .set _OPT,-0x47 # Default option .set _SETDRV,-0x46 # Drive to force @@ -50,11 +50,11 @@ .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. -# + /* + * Initialise segments and registers to known values. + * segments start at 0. The stack is immediately below the + * address we were loaded to. + */ start: cld # String ops inc xorw %ax,%ax # Zero movw %ax,%es # Address @@ -62,83 +62,95 @@ start: cld # String ops inc movw %ax,%ss # Set up movw $LOAD,%sp # stack -# -# Copy this code to the address it was linked for -# + /* + * Copy this code to the address it was linked for + */ movw %sp,%si # Source movw $start,%di # Destination movw $0x100,%cx # Word count rep # Relocate movsw # 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. -# + + /* + * 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 %di,%bp # Address variables movb $0x8,%cl # Words to clear rep # Zero stosw # them -# -# Relocate to the new copy of the code. -# + + /* + * Relocate to the new copy of the code. + */ incb -0xe(%di) # Sector number - jmp main-LOAD+ORIGIN # To relocated code -# -# 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. -# + jmp main-LOAD+BOOT0_ORIGIN # To relocated code + + /* + * 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. + */ main: testb $0x20,_FLAGS(%bp) # Set number drive? jnz main.1 # Yes testb %dl,%dl # Drive number valid? js main.2 # Possibly (0x80 set) main.1: movb _SETDRV(%bp),%dl # Drive number to use -# -# Whatever we decided to use, now store it into the fake -# partition entry that lives in the data space above us. -# + + /* + * Whatever we decided to use, now store it into the fake + * partition entry that lives in the data space above us. + */ main.2: 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) -# + + /* + * 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. -# + + /* + * 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. -# + + /* + * 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 -# + + /* + * 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 "?". -# + + /* + * 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 @@ -146,39 +158,47 @@ main.4: movb (%di),%cl # Partition 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, -# + + /* + * 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. -# + + /* + * 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. -# + + /* + * 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. -# + + /* + * 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. -# + + /* + * 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 @@ -188,10 +208,11 @@ main.7: movw $prompt,%si # Display 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. -# + + /* + * 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 @@ -199,54 +220,61 @@ main.8: movb $0x1,%ah # BIOS: Check int $0x1a # system time cmpw %di,%dx # Timeout? jb main.8 # No -# -# If timed out or defaulting, come here. -# + + /* + * 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. -# + + /* + * 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. -# + + /* + * 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. -# + + /* + * 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. -# + + /* + * 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. -# + + /* + * 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. -# + + /* + * 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 @@ -258,9 +286,10 @@ main.12: cbtw # Option 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. -# + + /* + * If not asked to do a write-back (flags 0x40) don't do one. + */ main.13: pushw %bx # Save testb $0x40,_FLAGS(%bp) # No updates? jnz main.14 # Yes @@ -269,19 +298,21 @@ main.13: pushw %bx # Save 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! -# + + /* + * 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 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. -# XXX what does %si carry? -# + + /* + * 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. + * XXX what does %si carry? + */ main.15: movw $LOAD,%bx # Address for read movb $0x2,%ah # Read sector callw intx13 # from disk @@ -293,20 +324,20 @@ main.15: movw $LOAD,%bx # Address for callw puts # space popw %si # Restore jmp *%bx # Invoke bootstrap -# -# Display routines -# + /* + * 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.. -# + /* + * 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 @@ -330,14 +361,15 @@ putchr: pusha # Save popa # Restore retw # To caller -# One-sector disk I/O routine -# -# Setup for both the packet and non-packet interfaces then select one or -# the other. -# -# Don't trust the BIOS to keep registers intact across the call, use -# pusha/popa. - + /* + * One-sector disk I/O routine + * + * Setup for both the packet and non-packet interfaces + * then select one or the other. + * + * Don't trust the BIOS to keep registers intact across + * the call, use pusha/popa. + */ intx13: movb 0x1(%si),%dh # (nonpkt) head movw 0x2(%si),%cx # (nonpkt) cylinder:sector movb $0x1,%al # (nonpkt) Sector count @@ -360,28 +392,35 @@ intx13.1: int $0x13 # BIOS: Disk I/O popa # Restore registers retw -# Menu strings + /* + * Menu strings + */ item: .ascii " "; .byte ' '|0x80 prompt: .ascii "\nDefault:"; .byte ' '|0x80 crlf: .ascii "\r"; .byte '\n'|0x80 -# Partition type tables + /* + * Partition type tables + */ tables: -# -# These entries identify invalid or NON BOOT types and partitions. -# + /* + * These entries identify invalid or NON BOOT types and + * partitions. + */ .byte 0x0, 0x5, 0xf -# -# These values indicate bootable types we know the names of -# + + /* + * These values indicate bootable types we know the names of. + */ .byte 0x1, 0x4, 0x6, 0xb, 0xc, 0xe, 0x83 .byte 0x9f, 0xa5, 0xa6, 0xa9 -# -# These are offsets that match the known names above and point to the strings -# that will be printed. -# + + /* + * 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 @@ -394,10 +433,12 @@ tables: .byte os_freebsd-. # FreeBSD .byte os_bsd-. # OpenBSD .byte os_bsd-. # 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...) -# + + /* + * 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 "?"; .byte '?'|0x80 os_dos: .ascii "DO"; .byte 'S'|0x80 os_linux: .ascii "Linu"; .byte 'x'|0x80 @@ -408,11 +449,11 @@ os_bsd: .ascii "BS"; .byte 'D'|0x80 .word B0MAGIC # Magic number -# -# 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. -# + /* + * 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. + */ drive: .ascii "Drive " nxtdrv: .byte 0x0 # Next drive number opt: .byte 0x0 # Option @@ -420,8 +461,9 @@ 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. -# + /* + * here is the 64 byte partition table that fdisk would + * fiddle with. + */ partbl: .fill 0x40,0x1,0x0 # Partition table .word MAGIC # Magic number