linux-kernel - Re: x86/stack protector: X86_32_LAZY_GS=n hangs kernel on old processors

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Message-ID: <CAP8WD_Z+yYXiRUZt4eMo2+zOSPFhsw=XiqJQUqVZFGGnGoWdPg@mail.gmail.com>
Date:   Tue, 13 Feb 2018 11:57:41 -0500
From:   tedheadster <tedheadster@...il.com>
To:     Tejun Heo <tj@...nel.org>
Cc:     jeremy@...source.com, rusty@...tcorp.com.au, mingo@...e.hu,
        Kees Cook <keescook@...omium.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: x86/stack protector: X86_32_LAZY_GS=n hangs kernel on old processors

> On Tue, Feb 13, 2018 at 11:40:17AM -0500, tedheadster wrote:
>>   in your patch "x86: make lazy %gs optional on x86_32" were you able
>> to test it on really old processors? In 4.16.0-rc1, X86_32_LAZY_GS got
>> toggled from 'y' to 'n' in my default config because of changes to the
>> stack protector code. It hangs my ancient i486 test machine right
>> after 'Booting the kernel'.
>
> I didn't have access to an i486 at the time or ever since, so it
> wasn't tested there.  If this is specific to i486, flagging it so in
> the config probably isn't the end of the world at this point.

Tejun,
  I will be able to test this on other 32bit hardware at the end of
the week. Hopefully I'll be able to identify which processors it does
not work on (i486/i586/i686).

- Matthew