From: dwalker@fifo99.com
To: Michael Ellerman <mpe@ellerman.id.au>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Paul Mackerras <paulus@samba.org>,
linuxppc-dev@lists.ozlabs.org
Subject: Re: simple_alloc space tramples initrd
Date: Mon, 11 Jan 2016 08:49:17 -0800 [thread overview]
Message-ID: <20160111164916.GA18065@fifo99.com> (raw)
In-Reply-To: <1452481774.31943.3.camel@ellerman.id.au>
On Mon, Jan 11, 2016 at 02:09:34PM +1100, Michael Ellerman wrote:
> On Fri, 2016-01-08 at 09:45 -0800, dwalker@fifo99.com wrote:
> > Hi,
> >
> > A powerpc machine I'm working on has this problem where the
> > simple_alloc_init() area is trampling the initrd. The two are placed fairly
> > close together.
>
> Which machine / platform?
It's not upstream yet. I'm still putting the patches together, that's when this
issue came up. I can send an RFC if you want to look at the patches.
> > I have a fix for this proposed to add a section into
> > arch/powerpc/boot/zImage.lds.S called "mallocarea" to account for this space,
> > but not all powerpc platforms use simple_alloc_init(). So for those platforms
> > it's a waste.
>
> Yeah I don't really like the sound of that. We could do it if it was behind a
> CONFIG option, but hopefully there is a better solution.
>
> > Another alternative is to alter the bootloader to place more space between
> > the kernel image and initrd image.
> >
> > I wanted to get some feedback on the right way to fix this. It seems like it
> > could be a generic issue on powerpc, or it's possibly already fixed someplace
> > and I just haven't noticed.
>
> I don't really know that code very well. But ideally either the boot loader
> gives you space, or the platform boot code is smart enough to detect that there
> is insufficient room and puts the heap somewhere else.
It seems like the kernel should be able to handle it. I believe the bootloader passes
the initrd location , but I don't think it's evaluated till later in the boot up. For
simple_alloc_init() it seems all platforms just assume the space is empty without checking.
Daniel
next prev parent reply other threads:[~2016-01-11 16:57 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-01-08 17:45 simple_alloc space tramples initrd dwalker
2016-01-11 3:09 ` Michael Ellerman
2016-01-11 16:49 ` dwalker [this message]
2016-01-11 22:17 ` Michael Ellerman
2016-01-11 23:07 ` dwalker
2016-01-11 23:37 ` Michael Ellerman
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