linux-kernel - Re: [PATCH] powerpc/32: Fix boot failure with CONFIG

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Date:   Thu, 29 Apr 2021 19:49:21 +0200
From:   Jonathan Neuschäfer <j.neuschaefer@....net>
To:     Christophe Leroy <christophe.leroy@...roup.eu>
Cc:     Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>, j.neuschaefer@....net,
        jniethe5@...il.com, linux-kernel@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH] powerpc/32: Fix boot failure with CONFIG_STACKPROTECTOR

On Thu, Apr 29, 2021 at 04:52:09PM +0000, Christophe Leroy wrote:
> Commit 7c95d8893fb5 ("powerpc: Change calling convention for
> create_branch() et. al.") complexified the frame of function
> do_feature_fixups(), leading to GCC setting up a stack
> guard when CONFIG_STACKPROTECTOR is selected.
> 
> The problem is that do_feature_fixups() is called very early
> while 'current' in r2 is not set up yet and the code is still
> not at the final address used at link time.
> 
> So, like other instrumentation, stack protection needs to be
> deactivated for feature-fixups.c and code-patching.c
> 
> Reported-by: Jonathan Neuschaefer <j.neuschaefer@....net>
> Fixes: 7c95d8893fb5 ("powerpc: Change calling convention for create_branch() et. al.")
> Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
> ---

Thank you for looking into this issue. This patch does indeed fix my
issue.

Tested-by: Jonathan Neuschaefer <j.neuschaefer@....net>


Thanks again,
Jonathan

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