| /* |
| * Copyright (c) 2008 Luigi Rizzo (mostly documentation) |
| * Copyright (c) 2002 Bruce M. Simpson |
| * 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. |
| * |
| * $FreeBSD$ |
| */ |
| |
| /* build options: */ |
| #ifdef SIO /* use serial console on COM1. */ |
| #endif |
| |
| #ifdef PXE /* enable PXE/INT18 booting with F6 */ |
| #define SAVE_MORE_MEMORY |
| #endif |
| |
| #ifdef CHECK_DRIVE /* make sure we boot from a HD. */ |
| #endif |
| |
| #ifdef ONLY_F_KEYS /* Only F1..F6, no digits on console */ |
| #endif |
| |
| #ifdef VOLUME_SERIAL /* support Volume serial number */ |
| #define B0_BASE 0x1ae /* move the internal data area */ |
| #define SAVE_MEMORY |
| #else |
| #define B0_BASE 0x1b2 |
| #endif |
| |
| #ifdef TEST /* enable some test code */ |
| #define SAVE_MEMORY |
| #define SAVE_MORE_MEMORY |
| #endif |
| |
| /* |
| * Note - this code uses many tricks to save space and fit in one sector. |
| * This includes using side effects of certain instructions, reusing |
| * register values from previous operations, etc. |
| * Be extremely careful when changing the code, even for simple things. |
| */ |
| |
| /* |
| * BOOT BLOCK STRUCTURE |
| * |
| * This code implements a Master Boot Record (MBR) for an Intel/PC disk. |
| * It is 512 bytes long and it is normally loaded by the BIOS (or another |
| * bootloader) at 0:0x7c00. This code depends on %cs:%ip being 0:0x7c00 |
| * |
| * The initial chunk of instructions is used as a signature by external |
| * tools (e.g. boot0cfg) which can manipulate the block itself. |
| * |
| * The area at offset 0x1b2 contains a magic string ('Drive '), also |
| * used as a signature to detect the block, and some variables that can |
| * be updated by boot0cfg (and optionally written back to the disk). |
| * These variables control the operation of the bootloader itself, |
| * e.g. which partitions to enable, the timeout, the use of LBA |
| * (called 'packet') or CHS mode, whether to force a drive number, |
| * and whether to write back the user's selection back to disk. |
| * |
| * As in every Master Boot Record, the partition table is at 0x1be, |
| * made of four 16-byte entries each containing: |
| * |
| * OFF SIZE DESCRIPTION |
| * 0 1 status (0x80: bootable, 0: non bootable) |
| * 1 3 start sector CHS |
| * 8:head, 6:sector, 2:cyl bit 9..8, 8:cyl bit 7..0 |
| * 4 1 partition type |
| * 5 3 end sector CHS |
| * 8 4 LBA of first sector |
| * 12 4 partition size in sectors |
| * |
| * and followed by the two bytes 0x55, 0xAA (MBR signature). |
| */ |
| |
| |
| /* |
| * BOOT BLOCK OPERATION |
| * |
| * On entry, the registers contain the following values: |
| * |
| * %cs:%ip 0:0x7c00 |
| * %dl drive number (0x80, 0x81, ... ) |
| * %si pointer to the partition table from which we were loaded. |
| * Some boot code (e.g. syslinux) use this info to relocate |
| * themselves, so we want to pass a valid one to the next stage. |
| * NOTE: the use of %si is not a standard. |
| * |
| * This boot block first relocates itself at a different address (0:0x600), |
| * to free the space at 0:0x7c00 for the next stage boot block. |
| * |
| * It then initializes some memory at 0:0x800 and above (pointed by %bp) |
| * to store the original drive number (%dl) passed to us, and to construct a |
| * fake partition entry. The latter is used by the disk I/O routine and, |
| * in some cases, passed in %si to the next stage boot code. |
| * |
| * The variables at 0x1b2 are accessed as negative offsets from %bp. |
| * |
| * After the relocation, the code scans the partition table printing |
| * out enabled partition or disks, and waits for user input. |
| * |
| * When a partition is selected, or a timeout expires, the currently |
| * selected partition is used to load the next stage boot code, |
| * %dl and %si are set appropriately as when we were called, and |
| * control is transferred to the newly loaded code at 0:0x7c00. |
| */ |
| |
| /* |
| * CONSTANTS |
| * |
| * NHRDRV is the address in segment 0 where the BIOS writes the |
| * total number of hard disks in the system. |
| * LOAD is the original load address and cannot be changed. |
| * ORIGIN is the relocation address. If you change it, you also need |
| * to change the value passed to the linker in the Makefile |
| * PRT_OFF is the location of the partition table (from the MBR standard). |
| * B0_OFF is the location of the data area, known to boot0cfg so |
| * it cannot be changed. Computed as a negative offset from 0x200 |
| * MAGIC is the signature of a boot block. |
| */ |
| |
| .set NHRDRV,0x475 # Number of hard drives |
| .set ORIGIN,0x600 # Execution address |
| .set LOAD,0x7c00 # Load address |
| |
| .set PRT_OFF,0x1be # Partition table |
| .set B0_OFF,(B0_BASE-0x200) # Offset of boot0 data |
| |
| .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 |
| |
| .set ASCII_BEL,'#' # ASCII code for <BEL> |
| .set ASCII_CR,0x0D # ASCII code for <CR> |
| |
| /* |
| * Offsets of variables in the block at B0_OFF, and in the volatile |
| * data area, computed as displacement from %bp. |
| * We need to define them as constant as the assembler cannot |
| * compute them in its single pass. |
| */ |
| .set _NXTDRV, B0_OFF+6 # Next drive |
| .set _OPT, B0_OFF+7 # Default option |
| .set _SETDRV, B0_OFF+8 # Drive to force |
| .set _FLAGS, B0_OFF+9 # Flags |
| .set SETDRV, 0x20 # the 'setdrv' flag |
| .set NOUPDATE, 0x40 # the 'noupdate' flag |
| .set USEPACKET, 0x80 # the 'packet' flag |
| |
| /* ticks is at a fixed position */ |
| .set _TICKS, (PRT_OFF - 0x200 - 2) # Timeout ticks |
| .set _MNUOPT, 0x10 # Saved menu entries |
| |
| .set TLEN, (desc_ofs - bootable_ids) # size of bootable ids |
| .globl start # Entry point |
| .code16 # This runs in real mode |
| |
| /* |
| * MAIN ENTRY POINT |
| * Initialise segments and registers to known values. |
| * segments start at 0. |
| * The stack is immediately below the address we were loaded to. |
| * NOTE: the initial section of the code (up to movw $LOAD,%sp) |
| * is used by boot0cfg, together with the 'Drive ' string and |
| * the 0x55, 0xaa at the end, as an identifier for version 1.0 |
| * of the boot code. Do not change it. |
| * In version 1.0 the parameter table (_NEXTDRV etc) is at 0x1b9 |
| */ |
| 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 |
| |
| /* |
| * Copy this code to the address it was linked for, 0x600 by default. |
| */ |
| movw %sp,%si # Source |
| movw $start,%di # Destination |
| movw $0x100,%cx # Word count |
| rep # Relocate |
| movsw # code |
| /* |
| * After the code, (i.e. at %di+0, 0x800) create a partition entry, |
| * initialized to LBA 0 / CHS 0:0:1. |
| * Set %bp to point to the partition and also, with negative offsets, |
| * to the variables embedded in the bootblock (nextdrv and so on). |
| */ |
| movw %di,%bp # Address variables |
| movb $0x8,%cl # Words to clear |
| rep # Zero |
| stosw # them |
| incb -0xe(%di) # Set the S field to 1 |
| |
| jmp main-LOAD+ORIGIN # Jump to relocated code |
| |
| main: |
| #if defined(SIO) && COMSPEED != 0 |
| /* |
| * Init the serial port. bioscom preserves the driver number in DX. |
| */ |
| movw $COMSPEED,%ax # defined by Makefile |
| callw bioscom |
| #endif |
| |
| /* |
| * If the 'setdrv' flag is set in the boot sector, use the drive |
| * number from the boot sector at 'setdrv_num'. |
| * Optionally, do the same if the BIOS gives us an invalid number |
| * (note though that the override prevents booting from a floppy |
| * or a ZIP/flash drive in floppy emulation). |
| * The test costs 4 bytes of code so it is disabled by default. |
| */ |
| testb $SETDRV,_FLAGS(%bp) # Set drive number? |
| #ifndef CHECK_DRIVE /* disable drive checks */ |
| jz save_curdrive # no, use the default |
| #else |
| jnz disable_update # Yes |
| testb %dl,%dl # Drive number valid? |
| js save_curdrive # Possibly (0x80 set) |
| #endif |
| /* |
| * Disable updates if the drive number is forced. |
| */ |
| disable_update: orb $NOUPDATE,_FLAGS(%bp) # Disable updates |
| movb _SETDRV(%bp),%dl # Use stored drive number |
| |
| /* |
| * Whatever drive we decided to use, store it at (%bp). The byte |
| * is normally used for the state of the partition (0x80 or 0x00), |
| * but we abuse it as it is very convenient to access at offset 0. |
| * The value is read back after 'check_selection' |
| */ |
| save_curdrive: movb %dl, (%bp) # Save drive number |
| pushw %dx # Also in the stack |
| #ifdef TEST /* test code, print internal bios drive */ |
| rolb $1, %dl |
| movw $drive, %si |
| call putkey |
| #endif |
| callw putn # Print a newline |
| /* |
| * 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. We use the latter trick to check for |
| * end of the loop without using an extra register (see start.5). |
| */ |
| 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. |
| */ |
| read_entry: movb %ch,-0x4(%bx) # Zero active flag (ch == 0) |
| btw %dx,_FLAGS(%bp) # Entry enabled? |
| jnc next_entry # No |
| movb (%bx),%al # Load type |
| test %al, %al # skip empty partition |
| jz next_entry |
| /* |
| * Scan the table of bootable ids, which starts at %di and has |
| * length TLEN. On a match, %di points to the element following the |
| * match; the corresponding offset to the description is $(TLEN-1) |
| * bytes ahead. We use a count of TLEN+1 so if we don't find a match |
| * within the first TLEN entries, we hit the 'unknown' entry. |
| */ |
| movw $bootable_ids,%di # Lookup tables |
| movb $(TLEN+1),%cl # Number of entries |
| repne # Locate |
| scasb # type |
| /* |
| * Get the matching element in the next array. |
| * The byte at $(TLEN-1)(%di) contains the offset of the description |
| * string from %di, so we add the number and print the string. |
| */ |
| addw $(TLEN-1), %di # Adjust |
| movb (%di),%cl # Partition |
| addw %cx,%di # description |
| callw putx # Display it |
| |
| next_entry: incw %dx # Next item |
| addb $0x10,%bl # Next entry |
| jnc read_entry # Till done |
| /* |
| * We are past a 256 byte boundary: the partition table is finished. |
| * Add one to the drive number and check it is valid. |
| * Note that if we started from a floppy, %dl was 0 so we still |
| * get an entry for the next drive, which is the first Hard Disk. |
| */ |
| popw %ax # Drive number |
| subb $0x80-0x1,%al # Does next |
| cmpb NHRDRV,%al # drive exist? (from BIOS?) |
| jb print_drive # Yes |
| /* |
| * If this is the only drive, don't display it as an option. |
| */ |
| decw %ax # Already drive 0? |
| jz print_prompt # Yes |
| /* |
| * If it was illegal or we cycled through them, 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 "nxtdrv" location in case we want to save it to disk. |
| * This digit is also part of the printed drive string, so add 0x80 |
| * to indicate end of string. |
| */ |
| print_drive: addb $'0'|0x80,%al # Save next |
| movb %al,_NXTDRV(%bp) # drive number |
| movw $drive,%di # Display |
| callw putx # item |
| /* |
| * Menu is complete, display a prompt followed by current selection. |
| * 'decw %si' makes the register point to the space after 'Boot: ' |
| * so we do not see an extra CRLF on the screen. |
| */ |
| print_prompt: movw $prompt,%si # Display |
| callw putstr # prompt |
| movb _OPT(%bp),%dl # Display |
| decw %si # default |
| callw putkey # key |
| jmp start_input # Skip beep |
| |
| /* |
| * Here we have the code waiting for user input or a timeout. |
| */ |
| beep: movb $ASCII_BEL,%al # Input error, print or beep |
| callw putchr |
| |
| start_input: |
| /* |
| * Actual Start of input loop. Take note of time |
| */ |
| xorb %ah,%ah # BIOS: Get |
| int $0x1a # system time |
| movw %dx,%di # Ticks when |
| addw _TICKS(%bp),%di # timeout |
| read_key: |
| /* |
| * Busy loop, looking for keystrokes but keeping one eye on the time. |
| */ |
| #ifndef SIO |
| movb $0x1,%ah # BIOS: Check |
| int $0x16 # for keypress |
| #else /* SIO */ |
| movb $0x03,%ah # BIOS: Read COM |
| call bioscom |
| testb $0x01,%ah # Check line status |
| # (bit 1 indicates input) |
| #endif /* SIO */ |
| jnz got_key # Have input |
| xorb %ah,%ah # BIOS: int 0x1a, 00 |
| int $0x1a # get system time |
| cmpw %di,%dx # Timeout? |
| jb read_key # No |
| |
| /* |
| * Timed out or default selection |
| */ |
| use_default: movb _OPT(%bp),%al # Load default |
| orb $NOUPDATE,_FLAGS(%bp) # Disable updates |
| jmp check_selection # Join common code |
| |
| /* |
| * Get the keystroke. |
| * ENTER or CR confirm the current selection (same as a timeout). |
| * Otherwise convert F1..F6 (or '1'..'6') to 0..5 and check if the |
| * selection is valid. |
| * The SIO code uses ascii chars, the console code uses scancodes. |
| */ |
| got_key: |
| #ifndef SIO |
| xorb %ah,%ah # BIOS: int 0x16, 00 |
| int $0x16 # get keypress |
| movb %ah,%al # move scan code to %al |
| cmpb $KEY_ENTER,%al |
| #else |
| movb $0x02,%ah # BIOS: Receive |
| call bioscom |
| cmpb $ASCII_CR,%al |
| #endif |
| je use_default # enter -> default |
| /* |
| * Check if the key is acceptable, and loop back if not. |
| * The console (non-SIO) code looks at scancodes and accepts |
| * both F1..F6 and 1..6 (the latter costs 6 bytes of code), |
| * relying on the fact that F1..F6 have higher scancodes than 1..6 |
| * The SIO code only takes 1..6 |
| */ |
| #ifdef SIO /* SIO mode, use ascii values */ |
| subb $'1',%al # Subtract '1' ascii code |
| #else /* console mode -- use scancodes */ |
| subb $KEY_F1,%al /* Subtract F1 scan code */ |
| #if !defined(ONLY_F_KEYS) |
| cmpb $0x5,%al # F1..F6 |
| jna 3f # Yes |
| subb $(KEY_1 - KEY_F1),%al # Less #1 scan code |
| 3: |
| #endif /* ONLY_F_KEYS */ |
| #endif /* SIO */ |
| check_selection: |
| cmpb $0x5,%al # F1..F6 or 1..6 ? |
| #ifdef PXE /* enable PXE/INT18 using F6 */ |
| jne 1f; |
| int $0x18 # found F6, try INT18 |
| 1: |
| #endif /* PXE */ |
| jae beep # Not in F1..F5, beep |
| |
| /* |
| * We have a selection. 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. |
| */ |
| cbtw # Extend (%ah=0 used later) |
| btw %ax,_MNUOPT(%bp) # Option enabled? |
| jnc beep # No |
| /* |
| * Save the info in the original tables |
| * for rewriting to the disk. |
| */ |
| movb %al,_OPT(%bp) # Save option |
| |
| /* |
| * Make %si and %bx point to the fake partition at LBA 0 (CHS 0:0:1). |
| * Because the correct address is already in %bp, just use it. |
| * Set %dl with the drive number saved in byte 0. |
| * If we have pressed F5 or 5, then this is a good, fake value |
| * to present to the next stage boot code. |
| */ |
| movw %bp,%si # Partition for write |
| movb (%si),%dl # Drive number, saved above |
| movw %si,%bx # Partition for read |
| cmpb $0x4,%al # F5/#5 pressed? |
| pushf # Save results for later |
| je 1f # Yes, F5 |
| |
| /* |
| * F1..F4 was pressed, so make %bx point to the currently |
| * selected partition, and leave the drive number unchanged. |
| */ |
| 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. |
| * Around the call, save the partition pointer to %bx and |
| * restore to %si which is where the next stage expects it. |
| */ |
| 1: pushw %bx # Save |
| testb $NOUPDATE,_FLAGS(%bp) # No updates? |
| jnz 2f # skip update |
| movw $start,%bx # Data to write |
| movb $0x3,%ah # Write sector |
| callw intx13 # to disk |
| 2: popw %si # Restore |
| |
| /* |
| * If going to next drive, replace drive with selected one. |
| * Remember to un-ascii it. Hey 0x80 is already set, cool! |
| */ |
| popf # Restore %al test results |
| jne 3f # If not F5/#5 |
| movb _NXTDRV(%bp),%dl # Next drive |
| subb $'0',%dl # number |
| /* |
| * Load selected bootsector to the LOAD location in RAM. If read |
| * fails or there is no 0x55aa marker, treat it as a bad selection. |
| */ |
| 3: movw $LOAD,%bx # Address for read |
| movb $0x2,%ah # Read sector |
| callw intx13 # from disk |
| jc beep # If error |
| cmpw $MAGIC,0x1fe(%bx) # Bootable? |
| jne beep # No |
| pushw %si # Save ptr to selected part. |
| callw putn # Leave some space |
| popw %si # Restore, next stage uses it |
| jmp *%bx # Invoke bootstrap |
| |
| /* |
| * Display routines |
| * putkey prints the option selected in %dl (F1..F5 or 1..5) followed by |
| * the string at %si |
| * putx: print the option in %dl followed by the string at %di |
| * also record the drive as valid. |
| * putn: print a crlf |
| * putstr: print the string at %si |
| * putchr: print the char in al |
| */ |
| |
| /* |
| * Display the option and record the drive as valid in the options. |
| * That last point is done using the btsw instruction which does |
| * a test and set. We don't care for the test part. |
| */ |
| putx: btsw %dx,_MNUOPT(%bp) # Enable menu option |
| movw $item,%si # Display |
| callw putkey # key |
| movw %di,%si # Display the rest |
| callw putstr # Display string |
| |
| putn: movw $crlf,%si # To next line |
| jmp putstr |
| |
| putkey: |
| #ifndef SIO |
| movb $'F',%al # Display |
| callw putchr # 'F' |
| #endif |
| movb $'1',%al # Prepare |
| addb %dl,%al # digit |
| |
| putstr.1: callw putchr # Display char |
| putstr: lodsb # Get byte |
| testb $0x80,%al # End of string? |
| jz putstr.1 # No |
| andb $~0x80,%al # Clear MSB then print last |
| |
| putchr: |
| #ifndef SIO |
| pushw %bx # Save |
| movw $0x7,%bx # Page:attribute |
| movb $0xe,%ah # BIOS: Display |
| int $0x10 # character |
| popw %bx # Restore |
| #else /* SIO */ |
| movb $0x01,%ah # BIOS: Send character |
| bioscom: |
| pushw %dx # Save |
| xorw %dx,%dx # Use COM1 |
| int $0x14 # BIOS: Serial I/O |
| popw %dx # Restore |
| #endif /* SIO */ |
| retw # To caller |
| |
| /* One-sector disk I/O routine */ |
| |
| /* |
| * %dl: drive, %si partition entry, %es:%bx transfer buffer. |
| * Load the CHS values and possibly the LBA address from the block |
| * at %si, and use the appropriate method to load the sector. |
| * Don't use packet mode for a floppy. |
| */ |
| intx13: # Prepare CHS parameters |
| movb 0x1(%si),%dh # Load head |
| movw 0x2(%si),%cx # Load cylinder:sector |
| movb $0x1,%al # Sector count |
| pushw %si # Save |
| movw %sp,%di # Save |
| #ifndef CHECK_DRIVE /* floppy support */ |
| testb %dl, %dl # is this a floppy ? |
| jz 1f # Yes, use CHS mode |
| #endif |
| testb $USEPACKET,_FLAGS(%bp) # Use packet interface? |
| jz 1f # No |
| pushl $0x0 # Set the |
| pushl 0x8(%si) # LBA address |
| pushw %es # Set the transfer |
| pushw %bx # buffer address |
| push $0x1 # Block count |
| push $0x10 # Packet size |
| movw %sp,%si # Packet pointer |
| decw %ax # Verify off |
| orb $0x40,%ah # Use disk packet |
| 1: int $0x13 # BIOS: Disk I/O |
| movw %di,%sp # Restore |
| popw %si # Restore |
| retw # To caller |
| |
| /* |
| * Various menu strings. 'item' goes after 'prompt' to save space. |
| * Also use shorter versions to make room for the PXE/INT18 code. |
| */ |
| prompt: |
| #ifdef PXE |
| .ascii "\nF6 PXE\r" |
| #endif |
| .ascii "\nBoot:" |
| item: .ascii " "; .byte ' '|0x80 |
| crlf: .ascii "\r"; .byte '\n'|0x80 |
| |
| /* Partition type tables */ |
| |
| bootable_ids: |
| /* |
| * These values indicate bootable types we know about. |
| * Corresponding descriptions are at desc_ofs: |
| * Entries don't need to be sorted. |
| */ |
| .byte 0x83, 0xa5, 0xa6, 0xa9, 0x06, 0x07, 0x0b |
| #ifndef SAVE_MORE_MEMORY |
| .byte 0x05 # extended partition |
| #endif |
| #ifndef SAVE_MEMORY /* other DOS partitions */ |
| .byte 0x01 # FAT12 |
| .byte 0x04 # FAT16 < 32M |
| #endif |
| |
| desc_ofs: |
| /* |
| * Offsets that match the known types above, used to point to the |
| * actual partition name. The last entry must point to os_misc, |
| * which is used for non-matching names. |
| */ |
| .byte os_linux-. # 131, Linux |
| .byte os_freebsd-. # 165, FreeBSD |
| .byte os_bsd-. # 166, OpenBSD |
| .byte os_bsd-. # 169, NetBSD |
| .byte os_dos-. # 6, FAT16 >= 32M |
| .byte os_win-. # 7, NTFS |
| .byte os_win-. # 11, FAT32 |
| |
| #ifndef SAVE_MORE_MEMORY |
| .byte os_ext-. # 5, DOS Ext |
| #endif |
| #ifndef SAVE_MEMORY |
| .byte os_dos-. # 1, FAT12 DOS |
| .byte os_dos-. # 4, FAT16 <32M |
| #endif |
| .byte os_misc-. # Unknown |
| |
| /* |
| * And here are the strings themselves. The last byte of |
| * the string has bit 7 set. |
| */ |
| os_misc: .byte '?'|0x80 |
| os_dos: |
| #ifndef SAVE_MORE_MEMORY /* 'DOS' remapped to 'WIN' if no room */ |
| .ascii "DO"; .byte 'S'|0x80 |
| #endif |
| os_win: .ascii "Wi"; .byte 'n'|0x80 |
| os_linux: .ascii "Linu"; .byte 'x'|0x80 |
| os_freebsd: .ascii "Free" |
| os_bsd: .ascii "BS"; .byte 'D'|0x80 |
| #ifndef SAVE_MORE_MEMORY |
| os_ext: .ascii "EX"; .byte 'T'|0x80 |
| #endif |
| |
| .org (0x200 + B0_OFF),0x90 |
| /* |
| * The boot0 version 1.0 parameter table. |
| * Do not move it nor change the "Drive " string, boot0cfg |
| * uses its offset and content to identify the boot sector. |
| * The other fields 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 |
| setdrv_num: .byte 0x80 # Drive to force |
| flags: .byte FLAGS # Flags |
| #ifdef VOLUME_SERIAL |
| .byte 0xa8,0xa8,0xa8,0xa8 # Volume Serial Number |
| #endif |
| ticks: .word TICKS # Delay |
| |
| .org PRT_OFF |
| /* |
| * Here is the 64 byte partition table that fdisk would fiddle with. |
| */ |
| partbl: .fill 0x40,0x1,0x0 # Partition table |
| .word MAGIC # Magic number |
| .org 0x200 # again, safety check |
| endblock: |