diff options
Diffstat (limited to 'sys/boot/i386')
| -rw-r--r-- | sys/boot/i386/boot0/boot0ext.S | 414 |
1 files changed, 210 insertions, 204 deletions
diff --git a/sys/boot/i386/boot0/boot0ext.S b/sys/boot/i386/boot0/boot0ext.S index b61c4b9..a63de25 100644 --- a/sys/boot/i386/boot0/boot0ext.S +++ b/sys/boot/i386/boot0/boot0ext.S @@ -1,21 +1,21 @@ -# -# 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. -# +/* + * 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. + * + * $FreeBSD$ + */ -# $FreeBSD$ - -# A 1024-byte boot manager. +/* A 1024-byte boot manager. */ .set NHRDRV,0x475 # Number of hard drives .set ORIGIN,0x600 # Execution address @@ -36,16 +36,16 @@ .set KEY_F1,0x3b # F1 key scan code .set KEY_1,0x02 # #1 key scan code -# -# Flag bits -# +/* + * 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). -# +/* + * 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 @@ -58,104 +58,105 @@ .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). -# +/* + * 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. -# +/* + * 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. -# +/* + * 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. -# +/* + * 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. -# +/* + * 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. -# +/* + * 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) -# +/* + * 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 @@ -163,39 +164,41 @@ 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 @@ -205,10 +208,10 @@ 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 @@ -216,54 +219,54 @@ 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 @@ -275,9 +278,9 @@ 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 $FL_NOUPDATE,_FLAGS(%bp) # Skip update? jnz main.14 # Yes @@ -286,18 +289,18 @@ 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/#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. -# +/* + * 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 @@ -307,9 +310,9 @@ main.15: movw $LOAD,%bx # Address for read callw putn # Leave some space jmp *%bx # Invoke bootstrap -# -# Display routines -# +/* + * Display routines + */ putkey: movb $'F',%al # Display callw putchr # 'F' @@ -317,10 +320,10 @@ putkey: movb $'F',%al # Display 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 @@ -344,21 +347,23 @@ putchr: pushw %bx # Save 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. +/* + * 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 @@ -403,14 +408,14 @@ intx13.2: int $0x13 # BIOS: Disk I/O 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). -# +/* + * 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 " @@ -420,40 +425,41 @@ 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 -# -# start of sector two.. ugh -# +/* + * start of sector two.. ugh + */ .org SECTOR_SIZE,0x90 -# 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. + */ table0: .byte 0x0, 0x5, 0xf table0_end: -# -# These values indicate bootable types we know the names of -# +/* + * 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. -# +/* + * 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 @@ -469,10 +475,10 @@ table1_end: .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...) -# +/* + * 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 @@ -484,10 +490,10 @@ 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. -# +/* + * 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: |
