Re: parisc: fix mmap(MAP_FIXED|MAP_SHARED) to already mmapped address

From: Helge Deller <deller@gmx.de>
To: Carlos O'Donell <carlos@systemhalted.org>
Cc: Aaro Koskinen <aaro.koskinen@iki.fi>,
	Mike Frysinger <vapier@gentoo.org>,
	John David Anglin <dave.anglin@bell.net>,
	linux-parisc <linux-parisc@vger.kernel.org>
Subject: Re: parisc: fix mmap(MAP_FIXED|MAP_SHARED) to already mmapped address
Date: Wed, 02 Apr 2014 23:09:46 +0200	[thread overview]
Message-ID: <533C7C9A.5080703@gmx.de> (raw)
In-Reply-To: <CAE2sS1jZTzccFy_uWri++cgVz+AYVfY0_aFqXFxnJXZV3d1a0g@mail.gmail.com>

On 04/02/2014 09:09 PM, Carlos O'Donell wrote:
> On Tue, Apr 1, 2014 at 2:49 PM, Helge Deller <deller@gmx.de> wrote:
>> Yes.
>> But it's not a kernel bug. Kernel 3.14 and previous stable releases are OK.
>>
>> I did proposed a glibc change in my previous mail (http://www.spinics.net/lists/linux-parisc/msg05384.html).
>> Debian bug report with patch is here:
>> https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=741243
>>
>> And this is what I proposed:
>>
>> A trivial FIX/workaround would be to change libc-mmap.h like this:
>> #ifdef __hppa__
>> #define MAP_FIXED_ALIGNMENT 4096
>> #else
>> #define MAP_FIXED_ALIGNMENT SHMLBA
>> #endif
>>
>> That works because then the new aligned address is then the same as the original
>> (the mmap call returns 4k aligned addresses, so it stays unchanged), but I'm not sure
>> if such a patch would be acceptable.
>> Do you have another idea/proposal?
> 
> The responsibility for fixing this falls to me, but I've been busy.

No problem.

> If someone wants to propose a patch for glibc please email
> libc-alpha@sourceware.org, TO me, and I'll review and commit the patch
> granted that you show you've done the appropriate testing.
> 
> Otherwise I'll get to this at some point in the next couple of weeks :-(

Hi Carlos,

I'm not really sure if my patch is the best way to go. Technically it's correct
and it's tested since all our debian buildservers currently run with this patch.
But all other options would probably involve more code changes.

So, I think I'm happy if you can look at it at some point when you find time.
Your input would be very valuable here.

Helge