Re: kern/66248: [panic] bootloader is confused by booting from USB flash, trashes main drives boot block

Not sure, but this may want to go into 4.11?
Is the bug in that as well?


Peter Edwards wrote:

>The following reply was made to PR kern/66248; it has been noted by GNATS.
>
>From: Peter Edwards <peadar_at_freebsd.org>
>To: freebsd-gnats-submit_at_FreeBSD.org, bremner_at_unb.ca
>Cc: julian_at_elischer.org, imp_at_bsdimp.org
>Subject: Re: kern/66248: [panic] bootloader is confused by booting from USB
> flash, trashes main drives boot block
>Date: Wed, 05 Jan 2005 20:53:02 +0000
>
> This is a multi-part message in MIME format.
> --------------070200040205060401080901
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> 
> The following patch, applied before the one above, shrinks boot0 enough 
> to squeeze the previous patch in without undeffing the BEL stuff.
> 
> FWIW: The patch to fix the bug looks good to me.
> I someone gives a go-ahead, I'll commit a combined patch: I certainly 
> don't want to make a commit to boot0 and have half the FreeBSD community 
> left without a bootable machine, unless I can pass the book :-)
> 
> 
> --------------070200040205060401080901
> Content-Type: text/plain;
>  name="boot0.smaller.patch"
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>  filename="boot0.smaller.patch"
> 
> Index: boot0.S
> ===================================================================
> RCS file: /usr/cvs/FreeBSD-CVS/src/sys/boot/i386/boot0/boot0.S,v
> retrieving revision 1.12
> diff -u -w -r1.12 boot0.S
> --- boot0.S	24 Nov 2004 15:39:04 -0000	1.12
> +++ boot0.S	5 Jan 2005 20:44:32 -0000
> _at__at_ -29,7 +29,7 _at__at_
>  		.set PRT_OFF,0x1be		# Partition table
>  
>  		.set TBL0SZ,0x3 		# Table 0 size
> -		.set TBL1SZ,0xb 		# Table 1 size
> +		.set TBL1SZ,0xc 		# Table 1 size
>  
>  		.set MAGIC,0xaa55		# Magic: bootable
>  		.set B0MAGIC,0xbb66		# Identification
> _at__at_ -148,13 +148,8 _at__at_
>  		movb $TBL1SZ,%cl		# Number of entries
>  		repne				# Known
>  		scasb				#  type?
> -		jne main.4			# No
> -/*
> - * If it matches get the matching element in the next array.  If it doesn't,
> - * we are already pointing at its first element which points to a "?".
> - */
> -		addw $TBL1SZ,%di		# Adjust
> -main.4:		movb (%di),%cl			# Partition
> +		addw $TBL1SZ - 1, %di		# Adjust
> +		movb (%di),%cl			# Partition
>  		addw %cx,%di			#  description
>  		callw putx			# Display it
>  main.5:		incw %dx			# Next item
> _at__at_ -314,8 +309,7 _at__at_
>  		cmpw $MAGIC,0x1fe(%bx)		# Bootable?
>  		jne main.10			# No
>  		pushw %si			# Save
> -		movw $crlf,%si			# Leave some
> -		callw puts			#  space
> +		callw putn			# Leave some space
>  		popw %si			# Restore
>  		jmp *%bx			# Invoke bootstrap
>  
> _at__at_ -408,14 +402,14 _at__at_
>  		.byte 0x0, 0x5, 0xf
>  /*
>   * These values indicate bootable types we know the names of.
> + * The value of the last entry is unimportant: it indicates "everything else"
>   */
>  		.byte 0x1, 0x4, 0x6, 0xb, 0xc, 0xe, 0x83
> -		.byte 0x9f, 0xa5, 0xa6, 0xa9
> +		.byte 0x9f, 0xa5, 0xa6, 0xa9, 0xff
>  /*
>   * These are offsets that match the known names above and point to the strings
>   * that will be printed.
>   */
> -		.byte os_misc-. 		# Unknown
>  		.byte os_dos-.			# DOS
>  		.byte os_dos-.			# DOS
>  		.byte os_dos-.			# DOS
> _at__at_ -427,6 +421,7 _at__at_
>  		.byte os_freebsd-.		# FreeBSD
>  		.byte os_bsd-.			# OpenBSD
>  		.byte os_bsd-.			# NetBSD
> +		.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...)
> 
> --------------070200040205060401080901--
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