linux-kernel - Re: POWER9 crash due to STRICT_KERNEL_RWX (WAS: Re: Linux-next POWER9 NULL pointer NIP...)

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Message-Id: <1587106774.1oa2whm69m.naveen@linux.ibm.com>
Date:   Fri, 17 Apr 2020 12:31:20 +0530
From:   "Naveen N. Rao" <naveen.n.rao@...ux.ibm.com>
To:     Qian Cai <cai@....pw>, Michael Ellerman <mpe@...erman.id.au>,
        Russell Currey <ruscur@...sell.cc>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>,
        Nicholas Piggin <npiggin@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>
Subject: Re: POWER9 crash due to STRICT_KERNEL_RWX (WAS: Re: Linux-next POWER9
 NULL pointer NIP...)

Hi Qian,

Qian Cai wrote:
> OK, reverted the commit,
> 
> c55d7b5e6426 (“powerpc: Remove STRICT_KERNEL_RWX incompatibility with RELOCATABLE”)
> 
> or set STRICT_KERNEL_RWX=n fixed the crash below and also mentioned in this thread,
> 
> https://lore.kernel.org/lkml/15AC5B0E-A221-4B8C-9039-FA96B8EF7C88@lca.pw/

Do you see any errors logged in dmesg when you see the crash?  
STRICT_KERNEL_RWX changes how patch_instruction() works, so it would be 
interesting to see if there are any ftrace-related errors thrown before 
the crash.


- Naveen