[oe] some possible fixes in the OE web pages

[Roman I Khimov]

В сообщении от Четверг 13 мая 2010 10:40:37 автор Martin Jansa написал:
> On Thu, May 13, 2010 at 09:53:54AM +0400, Roman I Khimov wrote:
> > В сообщении от Четверг 13 мая 2010 01:30:53 автор Robert P. J. Day 
написал:
> > > * on http://wiki.openembedded.net/index.php/OEandYourDistro#Ubuntu,
> > > there's a reference to configuring for qemu-arm:
> > >
> > >   echo 128 > /proc/sys/vm/mmap_min_addr
> > >
> > > from memory, i always simply set that to zero on fedora.  is there
> > > something magic about the value 128?  at the moment, it's at the
> > > default value of 65536 on this ubuntu system.
> >
> > With current qemu in OE mmap_min_addr tricks are not needed at all.
> 
> On some systems (I have report from fedora and kubuntu) it still needs 0
> in mmap_min_addr :/.
> 
> Investigating why, but it's slow because it doesn't fail on my box.
> 
> My guess is that this chunk from
> http://git.qemu.org/qemu.git/tree/linux-user/main.c
> cannot work on systems where normal user is not allowed to read
> /proc/sys/vm/mmap_min_addr and mmap_min_addr is not initialized with
> sane value.

Just checked with Ubuntu and Fedora, it really isn't possible to read 
/proc/sys/vm/mmap_min_addr as regular user, although it has 644 permissions on 
it. "Security"? Damn.

[after 15 minutes]

OK, actually there is a useful entry on Launchpad:
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/568844

The real solution is in the kernel, it should be fixed for latest Ubuntu and 
hopefully Fedora will catch up on this issue too.

http://git.kernel.org/?p=linux/kernel/git/jmorris/security-
testing-2.6.git;a=commitdiff;h=822cceec7248013821d655545ea45d1c6a9d15b3

Interesting that openSUSE with 2.6.31 kernel doesn't have such problems... And 
our main build machine with Debian stable + 2.6.30 kernel works fine too. 
Probably this check got introduced in 2.6.32.

Well, as the problem is in the kernel really, I think everyone having this 
problem should push distro maintainers to update kernels with the tiny fix 
mentioned above. But as a workaround, yep, "0" setting might work (beware that 
it might also not work as in here:
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/423513
).