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From: "Oliver O'Halloran" <oohall@gmail.com>
To: Segher Boessenkool <segher@kernel.crashing.org>
Cc: linuxppc-dev <linuxppc-dev@lists.ozlabs.org>,
	Alexey Kardashevskiy <aik@ozlabs.ru>,
	stable <stable@vger.kernel.org>
Subject: Re: [PATCH] powerpc/boot: Fix the initrd being overwritten under qemu
Date: Wed, 23 Oct 2019 23:44:41 +1100	[thread overview]
Message-ID: <CAOSf1CGjVt1v4RcazXTLkbm=fsswF8a5nqsLZod4=YwymLXPvg@mail.gmail.com> (raw)
In-Reply-To: <20191023112102.GN28442@gate.crashing.org>

On Wed, Oct 23, 2019 at 10:21 PM Segher Boessenkool
<segher@kernel.crashing.org> wrote:
>
> On Wed, Oct 23, 2019 at 12:36:35PM +1100, Oliver O'Halloran wrote:
> > When booting under OF the zImage expects the initrd address and size to be
> > passed to it using registers r3 and r4. SLOF (guest firmware used by QEMU)
> > currently doesn't do this so the zImage is not aware of the initrd
> > location.  This can result in initrd corruption either though the zImage
> > extracting the vmlinux over the initrd, or by the vmlinux overwriting the
> > initrd when relocating itself.
> >
> > QEMU does put the linux,initrd-start and linux,initrd-end properties into
> > the devicetree to vmlinux to find the initrd. We can work around the SLOF
> > bug by also looking those properties in the zImage.
>
> This is not a bug.  What boot protocol requires passing the initrd start
> and size in GPR3, GPR4?
>
> The CHRP binding (what SLOF implements) requires passing two zeroes here.
> And ePAPR requires passing the address of a device tree and a zero, plus
> something in GPR6 to allow distinguishing what it does.

This is what is assumed by the zImage.pseries. I have no idea where
that assumption comes from,A B

> As Alexey says, initramfs works just fine, so please use that?  initrd was
> deprecated when this code was written already.

That's not what Alexey said and the distinction between an initrd and
an initramfs is completely arbitrary.

>
>
> Segher

WARNING: multiple messages have this Message-ID (diff)
From: "Oliver O'Halloran" <oohall@gmail.com>
To: Segher Boessenkool <segher@kernel.crashing.org>
Cc: Alexey Kardashevskiy <aik@ozlabs.ru>,
	linuxppc-dev <linuxppc-dev@lists.ozlabs.org>,
	stable <stable@vger.kernel.org>
Subject: Re: [PATCH] powerpc/boot: Fix the initrd being overwritten under qemu
Date: Wed, 23 Oct 2019 23:44:41 +1100	[thread overview]
Message-ID: <CAOSf1CGjVt1v4RcazXTLkbm=fsswF8a5nqsLZod4=YwymLXPvg@mail.gmail.com> (raw)
In-Reply-To: <20191023112102.GN28442@gate.crashing.org>

On Wed, Oct 23, 2019 at 10:21 PM Segher Boessenkool
<segher@kernel.crashing.org> wrote:
>
> On Wed, Oct 23, 2019 at 12:36:35PM +1100, Oliver O'Halloran wrote:
> > When booting under OF the zImage expects the initrd address and size to be
> > passed to it using registers r3 and r4. SLOF (guest firmware used by QEMU)
> > currently doesn't do this so the zImage is not aware of the initrd
> > location.  This can result in initrd corruption either though the zImage
> > extracting the vmlinux over the initrd, or by the vmlinux overwriting the
> > initrd when relocating itself.
> >
> > QEMU does put the linux,initrd-start and linux,initrd-end properties into
> > the devicetree to vmlinux to find the initrd. We can work around the SLOF
> > bug by also looking those properties in the zImage.
>
> This is not a bug.  What boot protocol requires passing the initrd start
> and size in GPR3, GPR4?
>
> The CHRP binding (what SLOF implements) requires passing two zeroes here.
> And ePAPR requires passing the address of a device tree and a zero, plus
> something in GPR6 to allow distinguishing what it does.

This is what is assumed by the zImage.pseries. I have no idea where
that assumption comes from,A B

> As Alexey says, initramfs works just fine, so please use that?  initrd was
> deprecated when this code was written already.

That's not what Alexey said and the distinction between an initrd and
an initramfs is completely arbitrary.

>
>
> Segher

  reply	other threads:[~2019-10-23 12:44 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-23  1:36 [PATCH] powerpc/boot: Fix the initrd being overwritten under qemu Oliver O'Halloran
2019-10-23  1:36 ` Oliver O'Halloran
2019-10-23  7:00 ` Alexey Kardashevskiy
2019-10-23 11:21 ` Segher Boessenkool
2019-10-23 11:21   ` Segher Boessenkool
2019-10-23 12:44   ` Oliver O'Halloran [this message]
2019-10-23 12:44     ` Oliver O'Halloran
2019-10-24  1:31   ` Alexey Kardashevskiy
2019-10-24  1:47     ` Alexey Kardashevskiy
2019-10-24 17:45     ` Segher Boessenkool
2019-10-24 17:45       ` Segher Boessenkool
2019-10-25  0:03       ` Alexey Kardashevskiy
2019-10-25  0:03         ` Alexey Kardashevskiy

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