linux-kernel - Re: CONFIG_PAGE_TABLE_ISOLATION=y on x86_64 causes gcc to segfault when building x86

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Date:   Wed, 3 Jan 2018 12:57:45 +0100 (CET)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Lars Wendler <wendler.lars@....de>
cc:     LKML <linux-kernel@...r.kernel.org>, x86@...nel.org,
        Borislav Betkov <bp@...en8.de>,
        Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Greg KH <gregkh@...uxfoundation.org>
Subject: Re: CONFIG_PAGE_TABLE_ISOLATION=y on x86_64 causes gcc to segfault
 when building x86_32 binaries

Lars,

On Wed, 3 Jan 2018, Lars Wendler wrote:

Thanks for the report.

> I already had a conversation with Thomas Gleixner about this issue and
> he asked me to post it here.
> 
> After upgrading my system to vanilla 4.14.11 kernel with
> CONFIG_PAGE_TABLE_ISOLATION=y I could no longer build any 32bit
> binaries because gcc (7.2.0) segfaults.

That's a 64bit binary, right?

> This only happens with CONFIG_PAGE_TABLE_ISOLATION=y
> I can get rid of this issue by setting CONFIG_PAGE_TABLE_ISOLATION=n
> _or_ adding pti=off to the kernel command line (the latter was
> suggested by Thomas).
> 
> Please find attached the kernel's config together with the dmesg output
> of the kernel that produces segfaults and the one with pti=off. I also
> attached a config.log file from a build where gcc segfaulted.
> 
> If you need more information, please don't hesitate to ask.

will do.

Thanks,

	tglx