linux-kernel - Re: [PATCH v3 31/41] powerpc/32: Dismantle EXC_XFER

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Date:   Sun, 1 Aug 2021 11:39:07 +1000 (AEST)
From:   Finn Thain <fthain@...ux-m68k.org>
To:     Christophe Leroy <christophe.leroy@...roup.eu>
cc:     linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
        Nick Piggin <npiggin@...il.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Paul Mackerras <paulus@...ba.org>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Stan Johnson <userm57@...oo.com>
Subject: Re: [PATCH v3 31/41] powerpc/32: Dismantle
 EXC_XFER_STD/LITE/TEMPLATE

On Sat, 31 Jul 2021, Christophe Leroy wrote:

> > We found that reducing memory with the kernel parameter 'mem=464M' 
> > would prevent the crash.
> > 
> > Below are Stan's notes from the 'git bisect' run. They include an 
> > additional failure mode that might be of interest. We've also observed 
> > "Kernel attempted to write user page (c6207c) - exploit attempt?" and 
> > "kernel BUG at arch/powerpc/kernel/interrupt.c:49!".
> > 
> 
> Interesting.  Can you provide detailed log of thoose two BUGs ?
> 

I've attached the dmesg output which Stan sent me a few days ago. It 
contains results for 3 different builds run on two different machines 
(Wallstreet-1 and Wallstreet-2).

$ grep Linux.version WS-1-dmesg
[    0.000000] Linux version 5.12.0-pmac (johnson@...nkPad) (powerpc-linux-gnu-gcc (Debian 8.3.0-2) 8.3.0, GNU ld (GNU Binutils for Debian) 2.31.1) #6 SMP Sat Jul 24 11:49:36 MDT 2021
[    0.000000] Linux version 5.13.0-pmac (johnson@...nkPad) (powerpc-linux-gnu-gcc (Debian 8.3.0-2) 8.3.0, GNU ld (GNU Binutils for Debian) 2.31.1) #5 SMP Sat Jul 24 11:00:06 MDT 2021
[    0.000000] Linux version 5.14.0-rc2-pmac-00323-gd8079fac1681 (johnson@...nkPad) (powerpc-linux-gnu-gcc (Debian 8.3.0-2) 8.3.0, GNU ld (GNU Binutils for Debian) 2.31.1) #7 SMP Sun Jul 25 09:14:32 MDT 2021

$ grep Linux.version WS-2-dmesg
[    0.000000] Linux version 5.12.0-pmac (johnson@...nkPad) (powerpc-linux-gnu-gcc (Debian 8.3.0-2) 8.3.0, GNU ld (GNU Binutils for Debian) 2.31.1) #6 SMP Sat Jul 24 11:49:36 MDT 2021
[    0.000000] Linux version 5.13.0-pmac (johnson@...nkPad) (powerpc-linux-gnu-gcc (Debian 8.3.0-2) 8.3.0, GNU ld (GNU Binutils for Debian) 2.31.1) #5 SMP Sat Jul 24 11:00:06 MDT 2021
[    0.000000] Linux version 5.14.0-rc2-pmac-00323-gd8079fac1681 (johnson@...nkPad) (powerpc-linux-gnu-gcc (Debian 8.3.0-2) 8.3.0, GNU ld (GNU Binutils for Debian) 2.31.1) #7 SMP Sun Jul 25 09:14:32 MDT 2021
View attachment "WS-1-dmesg" of type "text/plain" (60788 bytes)

View attachment "WS-2-dmesg" of type "text/plain" (66122 bytes)