linux-kernel - Re: [patch 16/19] x86 setup: handle boot loaders which set up the stack incorrectly

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Message-ID: <473BF4C5.4080909@zytor.com>
Date:	Wed, 14 Nov 2007 23:27:01 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Greg KH <gregkh@...e.de>
CC:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [patch 16/19] x86 setup: handle boot loaders which set up the
 stack incorrectly

Greg KH wrote:
> -stable review patch.  If anyone has any objections, please let us know.
> 
> ------------------
> From: H. Peter Anvin <hpa@...or.com>
> 
> patch 6b6815c6d5d1dc209701d1661a7a0e09a295db2f in mainline.
> 
> Apparently some specific versions of LILO enter the kernel with a
> stack pointer that doesn't match the rest of the segments.  Make our
> best attempt at untangling the resulting mess.
> 
> Signed-off-by: H. Peter Anvin <hpa@...or.com>
> Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>

Just FYI:

It has been reported that while this patch fixes old LILO, and possibly 
some other boot loaders (unknown), it has also broken older versions of 
SYSLINUX: they still boot, but the command line is truncated (exactly 
how much depends on the BIOS, but typical values are around 130 bytes.)

This is definitely traceable to a bug in SYSLINUX that was already fixed 
in release 3.50 (the current version of SYSLINUX is 3.52).

I have chosen to leave the patch in mainline, rather than trying yet 
another recipe and hope it doesn't break on some other random 
combination of bootloaders, since:

a) SYSLINUX is generally easily updated, compared to other bootloaders;
b) The failure mode is less severe (it still boots.)

... however, you may choose to call differently.

	-hpa
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