linux-kernel - Re: [PATCH v9 0/5] arm64: ptdump: View the second stage page-tables

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <ZtVW-CQ-G84lHUE5@google.com>
Date: Mon, 2 Sep 2024 06:11:04 +0000
From: Sebastian Ene <sebastianene@...gle.com>
To: Marc Zyngier <maz@...nel.org>
Cc: akpm@...ux-foundation.org, alexghiti@...osinc.com, ankita@...dia.com,
	ardb@...nel.org, catalin.marinas@....com,
	christophe.leroy@...roup.eu, james.morse@....com,
	vdonnefort@...gle.com, mark.rutland@....com, oliver.upton@...ux.dev,
	rananta@...gle.com, ryan.roberts@....com, shahuang@...hat.com,
	suzuki.poulose@....com, will@...nel.org, yuzenghui@...wei.com,
	kvmarm@...ts.linux.dev, linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org, kernel-team@...roid.com
Subject: Re: [PATCH v9 0/5] arm64: ptdump: View the second stage page-tables

On Fri, Aug 30, 2024 at 04:00:11PM +0100, Marc Zyngier wrote:
> On Fri, 30 Aug 2024 15:44:39 +0100,
> Marc Zyngier <maz@...nel.org> wrote:

Hello Marc,

> > 
> > Hi Seb,
> 
> [...]
> 
> > I've been giving this a go on my test systems with 16k pages, and it
> > doesn't really work as advertised:
> > 
> > root@...ette:/sys/kernel/debug/kvm# cat 2573-13/stage2_*
> > 2
> > ---[ Guest IPA ]---
> > 0x0000000000000000-0x0000000008000000         128M 
> > 0x0000000008000000-0x00000000090a0000       17024K 3
> > 0x00000000090a0000-0x00000000090a4000          16K 3   R W X AF    
> > 0x00000000090a4000-0x000000000a000000       15728K 3
> > 
> > Only 16kB mapped? This is a full Linux guest running the Debian
> > installer, and just the kernel is about 20MB (the VM has 4GB of RAM,
> > and is using QEMU as the VMM)
> > 
> > So clearly something isn't playing as expected. Also, this '128M'
> > without a level being displayed makes me wonder. It is probably the
> > QEMU flash, but then the rest of the addresses don't make much sense
> > (RAM on QEMU is at 1GB, not at 128MB.
> > 
> > On another system with kvmtool, I get something similar:
> > 
> > root@...denum:/home/maz# cat /sys/kernel/debug/kvm/*/stage2_*
> > 2
> > ---[ Guest IPA ]---
> > 0x0000000000000000-0x0000000001020000       16512K 3
> > 0x0000000001020000-0x0000000001024000          16K 3   R W X AF    
> > 0x0000000001024000-0x0000000002000000       16240K 3
> > 
> > and kvmtool places the RAM at 2GB. Clearly not what we're seeing here.
> > 
> > Could you please verify this?

Ughh, this doesn't look right. I will give it a spin with a different
granule, thanks for bringing me to attention. I will look first at
mm/ptdump.c if it works as intended.
 

> 
> For the record, on a 4kB host, I get much more plausible results:
> 
> root@...-leg-emma:/home/maz# cat /sys/kernel/debug/kvm/632-12/stage2_*
> 3
> ---[ Guest IPA ]---
> 0x0000000000000000-0x0000000000200000           2M 2   R     AF BLK
> 0x0000000000200000-0x0000000040000000        1022M 2
> 0x0000000040000000-0x0000000040200000           2M 2   R W X AF BLK
> 0x0000000040200000-0x0000000044000000          62M 2
> 0x0000000044000000-0x0000000044200000           2M 2   R W X AF BLK
> 0x0000000044200000-0x0000000047600000          52M 2
> 0x0000000047600000-0x0000000047800000           2M 2   R W   AF BLK
> 0x0000000047800000-0x0000000047e00000           6M 2   R W X AF BLK
> 0x0000000047e00000-0x0000000048000000           2M 2   R W   AF BLK
> 0x0000000048000000-0x00000000b9c00000        1820M 2
> 0x00000000b9c00000-0x00000000b9e00000           2M 2   R W X AF BLK
> 0x00000000b9e00000-0x00000000bb800000          26M 2
> 0x00000000bb800000-0x00000000bba00000           2M 2   R W X AF BLK
> 0x00000000bba00000-0x00000000bbe00000           4M 2   R W   AF BLK
> 0x00000000bbe00000-0x00000000bc200000           4M 2   R W X AF BLK
> 0x00000000bc200000-0x00000000bc800000           6M 2   R W   AF BLK
> 0x00000000bc800000-0x00000000be400000          28M 2
> 0x00000000be400000-0x00000000bf800000          20M 2   R W X AF BLK
> 0x00000000bf800000-0x00000000bfe00000           6M 2   R W   AF BLK
> 0x00000000bfe00000-0x00000000c0000000           2M 2   R W X AF BLK
> 
> So 16kB is the one that needs investigating, and I strongly suspect
> that 64kB is in the same boat...
> 
> Thanks,
> 
> 	M. (signing off for the day)
> 

Thanks,
Sebastian

> -- 
> Without deviation from the norm, progress is not possible.