linux-kernel - Re: 2.6.23-rc3-mm1 - memory layout change? - lost support for MAP_32BIT?

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Date:	Thu, 23 Aug 2007 11:32:33 -0600
From:	Zan Lynx <zlynx@....org>
To:	Jiri Kosina <jkosina@...e.cz>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: 2.6.23-rc3-mm1 - memory layout change?  - lost support for
	MAP_32BIT? - mono crashes

On Thu, 2007-08-23 at 11:28 +0200, Jiri Kosina wrote:
> On Wed, 22 Aug 2007, Zan Lynx wrote:
> 
> > After installing this new wonder kernel on my AMD-64 laptop, I 
> > discovered that Beagle wouldn't start.  While enjoying how fast my 
> > system felt ( :) ) I also discovered that Evolution wouldn't start 
> > because it was built with mono integration.
> [...]
> > Mono claims to mmap with the MAP_32BIT option.
> > In -rc3-mm1 strace shows mono's mmap like this:
> > mmap(NULL, 65536, PROT_READ|PROT_WRITE|PROT_EXEC, MAP_PRIVATE|MAP_ANONYMOUS|MAP_32BIT, -1, 0) = 0x7fa21f5cb000
> 
> Hi Zan,
> 
> thanks for an excellent bugreport. Rather than throwing the whole 
> pie-randomization and flexmmap support away, could you please test the 
> patch below and let me know whether it fixes all your issues? Thanks.
> 
> 
> From: Jiri Kosina <jkosina@...e.cz>
> 
> Handle MAP_32BIT flags properly in x86_64 flexmmap
> 
> We need to handle MAP_32BIT flags of mmap() properly for 64bit 
> applications with filexible mmap layout.
> 
> This patch introduces x86_64-specific version of 
> arch_get_unmapped_area_topdown() which differs from the generic one in 
> handling of the MAP_32BIT flag -- when this flag is passed to mmap(), we 
> stick back to the legacy layout for this particular mmap, which gives 
> proper 32bit range.
> 
> Signed-off-by: Jiri Kosina <jkosina@...e.cz>
[snip patch]

This does fix the mono problem.  Thank you.
-- 
Zan Lynx <zlynx@....org>

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