Skip site navigation (1)Skip section navigation (2)
Date:      Sat, 2 May 2009 23:35:51 +0200
From:      Anders Nordby <anders@FreeBSD.org>
To:        Luigi Rizzo <luigi@FreeBSD.org>, svn-src-stable-7@freebsd.org
Subject:   Re: svn commit: r187198 - in stable/7: sys/boot/i386/boot0 usr.sbin/boot0cfg
Message-ID:  <20090502213551.GA52946@fupp.net>
In-Reply-To: <200901132228.n0DMSnai018184@svn.freebsd.org>
References:  <200901132228.n0DMSnai018184@svn.freebsd.org>

next in thread | previous in thread | raw e-mail | index | archive | help
Hi,

It seems that recent commits to boot0cfg and/or loader in RELENG_7,
makes the -s for boot0cfg not work anymore. At least, in my setup,
currdev and loaddev in loader is always set to disk0s1a (the first
partition), no matter if I try to boot another partition. Did you try
boot0cfg -s option since doing your updates?

Regards,
Anders.

On Tue, Jan 13, 2009 at 10:28:49PM +0000, Luigi Rizzo wrote:
> Author: luigi
> Date: Tue Jan 13 22:28:48 2009
> New Revision: 187198
> URL: http://svn.freebsd.org/changeset/base/187198
> 
> Log:
>   MFC: a number of small fixes and enhancements to the boot0 code,
>   and matching modifications to boot0cfg.
>   
>   The most noticeable features are preserving the 4-byte volume ID
>   that certain Windows versions put in the MBR, and an option (F6)
>   to boot through INT18 that on some modern BIOSes invokes PXE.
> 
> Modified:
>   stable/7/sys/boot/i386/boot0/boot0.S
>   stable/7/usr.sbin/boot0cfg/boot0cfg.8
>   stable/7/usr.sbin/boot0cfg/boot0cfg.c
> 
> Modified: stable/7/sys/boot/i386/boot0/boot0.S
> ==============================================================================
> --- stable/7/sys/boot/i386/boot0/boot0.S	Tue Jan 13 22:15:47 2009	(r187197)
> +++ stable/7/sys/boot/i386/boot0/boot0.S	Tue Jan 13 22:28:48 2009	(r187198)
> @@ -1,4 +1,5 @@
>  /*
> + * Copyright (c) 2008 Luigi Rizzo (mostly documentation)
>   * Copyright (c) 2002 Bruce M. Simpson
>   * Copyright (c) 1998 Robert Nordier
>   * All rights reserved.
> @@ -16,50 +17,166 @@
>   * $FreeBSD$
>   */
>  
> -/* A 512-byte boot manager. */
> -#ifdef SIO
> -/* ... using a serial console on COM1. */
> +/* 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 FAKE,0x800 		# Partition entry
>  		.set LOAD,0x7c00		# Load address
>  
>  		.set PRT_OFF,0x1be		# Partition table
> -
> -		.set TBL0SZ,0x3 		# Table 0 size
> -		.set TBL1SZ,0xa 		# Table 1 size
> +		.set B0_OFF,(B0_BASE-0x200)	# Offset of boot0 data
>  
>  		.set MAGIC,0xaa55		# Magic: bootable
> -		.set B0MAGIC,0xbb66		# Identification
>  
>  		.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,0x07		# ASCII code for <BEL>
> +		.set ASCII_BEL,'#'		# ASCII code for <BEL>
>  		.set ASCII_CR,0x0D		# ASCII code for <CR>
>  
>  /*
> - * 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
> -		.set _FLAGS,-0x45		# Flags
> -		.set _TICKS,-0x44		# Timeout ticks
> -		.set _FAKE,0x0			# Fake partition entry
> -		.set _MNUOPT,0xc		# Menu options
> + * 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
> @@ -69,7 +186,7 @@ start:		cld				# String ops inc
>  		movw $LOAD,%sp			#  stack
>  
>  /*
> - * Copy this code to the address it was linked for
> +	 * Copy this code to the address it was linked for, 0x600 by default.
>   */
>  		movw %sp,%si			# Source
>  		movw $start,%di			# Destination
> @@ -77,248 +194,301 @@ start:		cld				# String ops inc
>  		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.
> +	 * 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
> -/*
> - * Relocate to the new copy of the code.
> - */
> -		incb -0xe(%di)			# Sector number
> -		jmp main-LOAD+ORIGIN		# To relocated code
> +		incb -0xe(%di)			# Set the S field to 1
> +
> +		jmp main-LOAD+ORIGIN		# Jump to relocated code
>  
>  main:
>  #if defined(SIO) && COMSPEED != 0
>  /*
> - * Initialize the serial port.  bioscom preserves the driver number in DX.
> +	 * Init the serial port. bioscom preserves the driver number in DX.
>   */
>  		movw $COMSPEED,%ax		# defined by Makefile
>  		callw bioscom
>  #endif
> +
>  /*
> - * Check what flags were loaded with us, specifically if a predefined drive
> - * number should be used.  If what the bios gives us is bad, use the '0' in
> - * the block instead.
> - */
> -		testb $0x20,_FLAGS(%bp)		# Set drive number?
> -		jnz main.1			# Yes
> +	 * 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 main.2			# Possibly (0x80 set)
> +		js save_curdrive		# Possibly (0x80 set)
> +#endif
>  /*
> - * Only update the boot-sector when there is a valid drive number or
> - * the drive number is set manually.
> +	 * Disable updates if the drive number is forced.
>   */
> -		orb $0x40,_FLAGS(%bp)		# Disable updates
> -main.1:		movb _SETDRV(%bp),%dl		# Drive number to use
> +disable_update:	orb $NOUPDATE,_FLAGS(%bp)	# Disable updates
> +		movb _SETDRV(%bp),%dl		# Use stored drive number
> +
>  /*
> - * 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
> +	 * 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 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.
> +	 * 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. The end of loop test is at main.5.
> +	 * pass a 256 byte boundary.
>   */
> -main.3:		movb %ch,-0x4(%bx)		# Zero active flag (ch == 0)
> +read_entry:	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.
> - */
> +		jnc next_entry			# No
>  		movb (%bx),%al			# Load type
> -		movw $tables,%di		# Lookup tables
> -		movb $TBL0SZ,%cl		# Number of entries
> -		repne				# Exclude
> -		scasb				#  partition?
> -		je main.5			# Yes
> +		test %al, %al			# skip empty partition
> +		jz next_entry
>  /*
> - * Now scan the table of known types
> +	 * 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.
>   */
> -		movb $TBL1SZ+1,%cl		# Number of entries
> +		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 $TBL1SZ-1, %di		# Adjust
> +		addw $(TLEN-1), %di		# Adjust
>  		movb (%di),%cl			# Partition
>  		addw %cx,%di			#  description
>  		callw putx			# Display it
> -main.5:		incw %dx			# Next item
> +
> +next_entry:	incw %dx			# Next item
>  		addb $0x10,%bl			# Next entry
> -		jnc main.3			# Till done
> +		jnc read_entry			# Till done
>  /*
> - * Passed a 256 byte boundary; the table is finished.
> +	 * 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 main.6			# Yes
> +		jb print_drive			# Yes
>  /*
>   * If this is the only drive, don't display it as an option.
>   */
>  		decw %ax			# Already drive 0?
> -		jz main.7			# Yes
> +		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
> - * "next drive" location in the loaded block in case we want to save it later
> - * for next time.  This also is part of the printed drive string so add 0x80
> +	 * 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.
>   */
> -main.6:		addb $'0'|0x80,%al		# Save next
> +print_drive:	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.
> +	 * 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.
>   */
> -main.7:		movw $prompt,%si		# Display
> +print_prompt:	movw $prompt,%si		# Display
>  		callw putstr			#  prompt
>  		movb _OPT(%bp),%dl		# Display
>  		decw %si			#  default
>  		callw putkey			#  key
> -		jmp main.7_1			# Skip beep
> +		jmp start_input			# Skip beep
> +
>  /*
> - * Users's last try was bad, beep in displeasure.
> + * Here we have the code waiting for user input or a timeout.
>   */
> -main.10:	movb $ASCII_BEL,%al		# Signal
> -		callw putchr			#  beep!
> +beep:		movb $ASCII_BEL,%al		# Input error, print or beep
> +		callw putchr
> +
> +start_input:
>  /*
> - * Start of input loop.  Take note of time
> +	 * Actual Start of input loop.  Take note of time
>   */
> -main.7_1:	xorb %ah,%ah			# BIOS: Get
> +		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.
>   */
> -main.8:
>  #ifndef SIO
>  		movb $0x1,%ah			# BIOS: Check
>  		int $0x16			#  for keypress
> -		jnz main.11			# Have one
>  #else /* SIO */
>  		movb $0x03,%ah			# BIOS: Read COM
>  		call bioscom
>  		testb $0x01,%ah			# Check line status
> -		jnz main.11 			# (bit 1 indicates input)
> +						# (bit 1 indicates input)
>  #endif /* SIO */
> -		xorb %ah,%ah			# BIOS: Get
> -		int $0x1a			#  system time
> +		jnz got_key 			# Have input
> +		xorb %ah,%ah			# BIOS: int 0x1a, 00
> +		int $0x1a			#  get system time
>  		cmpw %di,%dx			# Timeout?
> -		jb main.8			# No
> +		jb read_key			# No
> +
>  /*
> - * If timed out or defaulting, come here.
> +	 * Timed out or default selection
>   */
> -main.9:		movb _OPT(%bp),%al		# Load default
> -		jmp main.12			# Join common code
> +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.
>   */
> -main.11:
> +got_key:
>  #ifndef SIO
> -		xorb %ah,%ah			# BIOS: Get
> -		int $0x16			#  keypress
> -		movb %ah,%al			# Scan code
> +		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
>  /*
> - * If it's CR act as if timed out.
> - */
> -#ifndef SIO
> -		cmpb $KEY_ENTER,%al		# Enter pressed?
> -#else
> -		cmpb $ASCII_CR,%al		# Enter pressed?
> -#endif
> -		je main.9			# Yes
> -/*
> - * Otherwise check if legal. If not ask again.
> - */
> -#ifndef SIO
> -		subb $KEY_F1,%al		# Less F1 scan code
> -		cmpb $0x4,%al			# F1..F5?
> -		jna main.12			# Yes
> +	 * 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
> -#else
> -		subb $'1',%al			# Less '1' ascii character
> -#endif
> -		cmpb $0x4,%al			# #1..#5?
> -		ja main.10			# No
> +	3:
> +#endif /* ONLY_F_KEYS */
> +#endif /* SIO */
> +		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
> +
> +check_selection:
>  /*
>   * 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.
>   */
> -main.12:	cbtw				# Option
> -		btw %ax,_MNUOPT(%bp)	 	#  enabled?
> -		jnc main.10			# No
> +		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
> -		movw $FAKE,%si			# Partition for write
> -		movb (%si),%dl			# Drive number
> +
> +	/*
> +	 * 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
> -		je main.13			# Yes
> +		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.
>   */
> -main.13:	pushw %bx			# Save
> -		testb $0x40,_FLAGS(%bp)		# No updates?
> -		jnz main.14			# Yes
> +	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
> -main.14:	popw %si			# Restore
> -		popf				# Restore
> +	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!
>   */
> -		jne main.15			# If not F5/#5
> +		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 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 read
> +	 * fails or there is no 0x55aa marker, treat it as a bad selection.
>   */
> -main.15:	movw $LOAD,%bx			# Address for read
> +	3:	movw $LOAD,%bx			# Address for read
>  		movb $0x2,%ah			# Read sector
>  		callw intx13			#  from disk
> -		jc main.10			# If error
> +		jc beep				# If error
>  		cmpw $MAGIC,0x1fe(%bx)		# Bootable?
> -		jne main.10			# No
> +		jne beep			# No
>  		pushw %si			# Save ptr to selected part.
>  		callw putn			# Leave some space
>  		popw %si			# Restore, next stage uses it
> @@ -326,64 +496,80 @@ main.15:	movw $LOAD,%bx			# Address for 
>  
>  /*
>   * 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
>   */
> -putkey:
> -#ifndef SIO
> -		movb $'F',%al			# Display
> -		callw putchr			#  'F'
> -#endif
> -		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 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
> -
> -puts:		callw putstr			# Display string
> +		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?
> -		jnz putstr.2			# Yes
> -putstr.1:	callw putchr			# Display char
> -		jmp putstr			# Continue
> -putstr.2:	andb $~0x80,%al 		# Clear MSB
> +		jz putstr.1			# No
> +		andb $~0x80,%al 		# Clear MSB then print last 
>  
> -#ifndef SIO
>  putchr:
> +#ifndef SIO
>  		pushw %bx			# Save
>  		movw $0x7,%bx	 		# Page:attribute
>  		movb $0xe,%ah			# BIOS: Display
>  		int $0x10			#  character
>  		popw %bx			# Restore
> -		retw				# To caller
>  #else /* SIO */
> -putchr:
>  		movb $0x01,%ah			# BIOS: Send
>  bioscom:
>  		pushw %dx			# Save
>  		xorw %dx,%dx 			# Use COM1
>  		int $0x14			#  Character
>  		popw %dx			# Restore
> -		retw				# To caller
>  #endif /* SIO */
> +		retw				# To caller
>  
>  /* One-sector disk I/O routine */
>  
> -intx13:		movb 0x1(%si),%dh		# Load head
> +/*
> + * %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
> -		testb $0x80,_FLAGS(%bp)		# Use packet interface?
> -		jz intx13.1			# No
> +#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
> @@ -393,73 +579,104 @@ intx13:		movb 0x1(%si),%dh		# Load head
>  		movw %sp,%si			# Packet pointer
>  		decw %ax			# Verify off
>  		orb $0x40,%ah			# Use disk packet
> -intx13.1:	int $0x13			# BIOS: Disk I/O
> +	1:	int $0x13			# BIOS: Disk I/O
>  		movw %di,%sp			# Restore
>  		popw %si			# Restore
>  		retw				# To caller
>  
> -/* Menu strings */
> -
> +/*
> + * 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
> -prompt:		.ascii "\nDefault:"; .byte ' '|0x80
>  crlf:		.ascii "\r";	     .byte '\n'|0x80
>  
>  /* Partition type tables */
>  
> -tables:
> +bootable_ids:
>  /*
> - * These entries identify invalid or NON BOOT types and partitions.
> - */
> -		.byte 0x0, 0x5, 0xf
> +	 * 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:
>  /*
> - * These values indicate bootable types we know the names of.
> - */
> -		.byte 0x1, 0x6, 0x7, 0xb, 0xc, 0xe, 0x83
> -		.byte 0xa5, 0xa6, 0xa9
> -/*
> - * These are offsets that match the known names above and point to the strings
> - * that will be printed. os_misc will be used if the search of the above table
> - * runs over.
> - */
> -		.byte os_dos-.			# DOS
> -		.byte os_dos-.			# DOS
> -		.byte os_dos-.			# Windows
> -		.byte os_dos-.			# Windows
> -		.byte os_dos-.			# Windows
> -		.byte os_dos-.			# Windows
> -		.byte os_linux-.		# Linux
> -		.byte os_freebsd-.		# FreeBSD
> -		.byte os_bsd-.			# OpenBSD
> -		.byte os_bsd-.			# NetBSD
> +	 * 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. 0x80 or'd into a byte indicates
> - * the end of the string. (not so great for Russians but...)
> +	 * And here are the strings themselves. The last byte of
> +	 * the string has bit 7 set.
>   */
> -os_misc:	.ascii "?";    .byte '?'|0x80
> -os_dos:		.ascii "DO";   .byte 'S'|0x80
> +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 PRT_OFF-0xe,0x90
> -
> -		.word B0MAGIC			# Magic number
> -
> +		.org (0x200 + B0_OFF),0x90
>  /*
> - * These values are sometimes changed before writing back to the drive
> + * 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:		.byte 0x80			# Drive to force
> +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:
> 
> Modified: stable/7/usr.sbin/boot0cfg/boot0cfg.8
> ==============================================================================
> --- stable/7/usr.sbin/boot0cfg/boot0cfg.8	Tue Jan 13 22:15:47 2009	(r187197)
> +++ stable/7/usr.sbin/boot0cfg/boot0cfg.8	Tue Jan 13 22:28:48 2009	(r187198)
> @@ -24,7 +24,7 @@
>  .\"
>  .\" $FreeBSD$
>  .\"
> -.Dd June 7, 2007
> +.Dd January 13, 2009
>  .Dt BOOT0CFG 8
>  .Os
>  .Sh NAME
> @@ -35,7 +35,9 @@
>  .Op Fl Bv
>  .Op Fl b Ar boot0
>  .Op Fl d Ar drive
> +.Op Fl e Ar bell character
>  .Op Fl f Ar file
> +.Op Fl i Ar volume-id
>  .Op Fl m Ar mask
>  .Op Fl o Ar options
>  .Op Fl s Ar slice
> @@ -96,10 +98,17 @@ which contains the specified
>  Typically this will be 0x80 for the first hard drive, 0x81 for the
>  second hard drive, and so on; however any integer between 0 and 0xff
>  is acceptable here.
> +.It Fl e Ar bell character
> +Set the character to be printed in case of input error.
>  .It Fl f Ar file
>  Specify that a backup copy of the preexisting MBR should be written to
>  .Ar file .
>  This file is created if it does not exist, and replaced if it does.
> +.It Fl i Ar volume-id
> +Specifies a volume-id (in the form XXXX-XXXX) to be saved at location
> +0x1b8 in the MBR. This information is sometimes used by NT, XP and Vista
> +to identify the disk drive. The option is only compatible with version 2.00
> +of the 512-byte boot block.
>  .It Fl m Ar mask
>  Specify slices to be enabled/disabled, where
>  .Ar mask
> @@ -144,6 +153,21 @@ Set the timeout value to
>  .It Fl v
>  Verbose: display information about the slices defined, etc.
>  .El
> +.Sh NOTE
> +Protection mechanisms in the
> +.Xr geom 4
> +subsystem might prevent
> +.Nm
> +from being able to update the MBR on a mounted disk.
> +Instructions for temporarily disabling these protection mechanisms
> +can be found in the
> +.Xr geom 4
> +manpage. Specifically, do a
> +.Pp
> +.Dl sysctl kern.geom.debugflags=0x10
> +.Pp
> +to allow writing to the MBR, and restore it to 0 afterwards.
> +.Pp
>  .Sh FILES
>  .Bl -tag -width /boot/boot0sio -compact
>  .It Pa /boot/boot0
> @@ -177,16 +201,6 @@ to install the default MBR:
>  .Sh AUTHORS
>  .An Robert Nordier Aq rnordier@FreeBSD.org .
>  .Sh BUGS
> -Protection mechanisms in the
> -.Xr geom 4
> -subsystem might prevent
> -.Nm
> -from being able to update the MBR on a mounted disk.
> -Instructions for temporarily disabling these protection mechanisms
> -can be found in the
> -.Xr geom 4
> -manpage.
> -.Pp
>  Use of the
>  .Sq packet
>  option may cause
> @@ -195,6 +209,6 @@ to fail, depending on the nature of BIOS
>  .Pp
>  Use of the
>  .Sq setdrv
> -option with an incorrect -d operand may cause the MBR to be written
> -to the wrong disk.
> -Be careful!
> +option with an incorrect -d operand may cause the boot0 code
> +to write the MBR to the wrong disk, thus trashing its previous
> +content.  Be careful.
> 
> Modified: stable/7/usr.sbin/boot0cfg/boot0cfg.c
> ==============================================================================
> --- stable/7/usr.sbin/boot0cfg/boot0cfg.c	Tue Jan 13 22:15:47 2009	(r187197)
> +++ stable/7/usr.sbin/boot0cfg/boot0cfg.c	Tue Jan 13 22:28:48 2009	(r187198)
> @@ -1,4 +1,5 @@
>  /*
> + * Copyright (c) 2008 Luigi Rizzo
>   * Copyright (c) 1999 Robert Nordier
>   * All rights reserved.
>   *
> @@ -44,13 +45,34 @@ __FBSDID("$FreeBSD$");
>  
>  #define MBRSIZE         512     /* master boot record size */
>  
> -#define OFF_VERSION	0x1b0	/* offset: version number */
> -#define OFF_OPT		0x1b9	/* offset: default boot option */
> -#define OFF_DRIVE	0x1ba	/* offset: setdrv drive */
> -#define OFF_FLAGS       0x1bb   /* offset: option flags */
> -#define OFF_TICKS       0x1bc   /* offset: clock ticks */
> +#define OFF_VERSION	0x1b0	/* offset: version number, only boot0version */
> +#define OFF_SERIAL	0x1b8	/* offset: volume serial number */
>  #define OFF_PTBL        0x1be   /* offset: partition table */
>  #define OFF_MAGIC       0x1fe   /* offset: magic number */
> +/*
> + * Offsets to the parameters of the 512-byte boot block.
> + * For historical reasons they are set as macros
> + */
> +struct opt_offsets {
> +	int opt;
> +	int drive;
> +	int flags;
> +	int ticks;
> +};
> +
> +struct opt_offsets b0_ofs[] = {
> +	{ 0x0, 0x0, 0x0, 0x0 },		/* no boot block */
> +	{ 0x1b9, 0x1ba, 0x1bb, 0x1bc },	/* original block */
> +	{ 0x1b5, 0x1b6, 0x1b7, 0x1bc },	/* NT_SERIAL block */
> +};
> +
> +int b0_ver;		/* boot block version set by boot0bs */
> +
> +#define OFF_OPT		(b0_ofs[b0_ver].opt)	/* default boot option */
> +#define OFF_DRIVE	(b0_ofs[b0_ver].drive)	/* setdrv drive */
> +#define OFF_FLAGS       (b0_ofs[b0_ver].flags)	/* option flags */
> +#define OFF_TICKS       (b0_ofs[b0_ver].ticks)	/* clock ticks */
> +
>  
>  #define cv2(p)  ((p)[0] | (p)[1] << 010)
>  
> @@ -82,8 +104,12 @@ static int boot0bs(const u_int8_t *);
> 
> *** DIFF OUTPUT TRUNCATED AT 1000 LINES ***
> _______________________________________________
> svn-src-stable-7@freebsd.org mailing list
> http://lists.freebsd.org/mailman/listinfo/svn-src-stable-7
> To unsubscribe, send any mail to "svn-src-stable-7-unsubscribe@freebsd.org"


-- 
Anders.



Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?20090502213551.GA52946>