From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43)
	id 1NqGka-00089S-Az
	for qemu-devel@nongnu.org; Fri, 12 Mar 2010 21:06:48 -0500
Received: from [199.232.76.173] (port=43769 helo=monty-python.gnu.org)
	by lists.gnu.org with esmtp (Exim 4.43) id 1NqGkZ-00088i-AK
	for qemu-devel@nongnu.org; Fri, 12 Mar 2010 21:06:47 -0500
Received: from Debian-exim by monty-python.gnu.org with spam-scanned (Exim
	4.60) (envelope-from <av1474@comtv.ru>) id 1NqGkW-00079H-Gd
	for qemu-devel@nongnu.org; Fri, 12 Mar 2010 21:06:47 -0500
Received: from fe01x03-cgp.akado.ru ([77.232.31.164]:63480 helo=akado.ru)
	by monty-python.gnu.org with esmtp (Exim 4.60)
	(envelope-from <av1474@comtv.ru>) id 1NqGkW-00079B-4r
	for qemu-devel@nongnu.org; Fri, 12 Mar 2010 21:06:44 -0500
Date: Sat, 13 Mar 2010 05:06:31 +0300 (MSK)
From: malc <av1474@comtv.ru>
In-Reply-To: <201003130045.22664.paul@codesourcery.com>
Message-ID: <alpine.LNX.2.00.1003130504460.1405@linmac>
References: <alpine.LNX.2.00.1003130314190.6704@linmac>
	<201003130045.22664.paul@codesourcery.com>
MIME-Version: 1.0
Content-Type: TEXT/PLAIN; charset=US-ASCII
Subject: [Qemu-devel] Re: linux-user issues
List-Id: qemu-devel.nongnu.org
List-Unsubscribe: <http://lists.nongnu.org/mailman/listinfo/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=unsubscribe>
List-Archive: <http://lists.gnu.org/pipermail/qemu-devel>
List-Post: <mailto:qemu-devel@nongnu.org>
List-Help: <mailto:qemu-devel-request@nongnu.org?subject=help>
List-Subscribe: <http://lists.nongnu.org/mailman/listinfo/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=subscribe>
To: Paul Brook <paul@codesourcery.com>
Cc: qemu-devel@nongnu.org, Aurelien Jarno <aurelien@aurel32.net>

On Sat, 13 Mar 2010, Paul Brook wrote:

> > a) elfload.c:859
> > 
> >    #define TARGET_ELF_PAGESTART(_v) ((_v) & ~(unsigned
> >  long)(TARGET_ELF_EXEC_PAGESIZE-1))
> > 
> >    This means that for 64bit guest on a 32bit host the _v's value is
> >    silently reduced to 32bit, the cast should be abi_ulong.
> > 
> > b) mmap.c:428
> > 
> >    real_start = start & qemu_host_page_mask;
> > 
> >    Same thing basically qemu_host_page_mask is unsigned long and so
> >    the upper bits are sliently cleared. Again qemu_host_page_mask
> >    should probably be abi_ulong.
> > 
> > The above two make elf binary with one of the segments above 4G load
> > and run on 32bit guest only to fail well into execution and without
> > any indication that it shouldn't have been allowed to run in the first
> > place.
> 
> I'd be amazed if these are the only two issues, and expect 64-bit guests on 
> 32-bit hosts to be generally unsafe.

These are the two issues i've been bitten by while trying to solve
x86_64's far jumps, if you are okay with code silently misbehaving
fine by me.

-- 
mailto:av1474@comtv.ru