From: David Laight <David.Laight@ACULAB.COM>
To: 'Uros Bizjak' <ubizjak@gmail.com>
Cc: Brian Gerst <brgerst@gmail.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"x86@kernel.org" <x86@kernel.org>,
"Ingo Molnar" <mingo@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
"Borislav Petkov" <bp@alien8.de>,
"H . Peter Anvin" <hpa@zytor.com>,
Peter Zijlstra <peterz@infradead.org>
Subject: RE: [PATCH v2 00/11] x86-64: Stack protector and percpu improvements
Date: Mon, 30 Oct 2023 09:05:48 +0000 [thread overview]
Message-ID: <1eb4f2c46e1642519a40924ed3fe3ccc@AcuMS.aculab.com> (raw)
In-Reply-To: <CAFULd4ZBGzceGbRaVLuMJ+qkoUpMv-rdBZB_D=Mni5RAWzgQBQ@mail.gmail.com>
From: Uros Bizjak
> Sent: 30 October 2023 08:07
>
> On Sun, Oct 29, 2023 at 10:42 PM David Laight <David.Laight@aculab.com> wrote:
> >
> > From: Brian Gerst
> > > Sent: 26 October 2023 17:01
> > >
> > > Currently, x86-64 uses an unusual percpu layout, where the percpu section
> > > is linked at absolute address 0. The reason behind this is that older GCC
> > > versions placed the stack protector (if enabled) at a fixed offset from the
> > > GS segment base. Since the GS segement is also used for percpu variables,
> > > this forced the current layout.
> > >
> > > GCC since version 8.1 supports a configurable location for the stack
> > > protector value, which allows removal of the restriction on how the percpu
> > > section is linked. This allows the percpu section to be linked
> > > normally, like most other architectures. In turn, this allows removal
> > > of code that was needed to support the zero-based percpu section.
> >
> > I didn't think the minimum gcc version was anything like 8.1.
> > I'm using 7.5.0 and I don't think that is the oldest version.
>
> Please see previous discussion regarding modernizing stack protector
> on x86_64 [1]
>
> [1] https://lore.kernel.org/lkml/20211113124035.9180-1-brgerst@gmail.com/
>
> and x86_32 [2]
>
> [2] https://lore.kernel.org/lkml/cover.1601925251.git.luto@kernel.org/
>
> The conclusion in [2] is:
>
> "I'm all in favour of simply requiring GCC-8.1 to build a more secure
> x86_64 kernel. Gives people an incentive to not use ancient compilers.
>
> And if you do want to use your ancient compiler, we'll still build, you
> just don't get to have stackprotector."
I didn't see a patch that limited 'stackprotector' to gcc >= 8.1
Without that anyone who already has it enabled and is using an
older compiler will get very broken kernels.
David
>
> and in [1]:
>
> "Ack. We did this for 32-bit and got few complaints. Let’s finish the job."
>
> Uros.
-
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next prev parent reply other threads:[~2023-10-30 9:06 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-10-26 16:00 [PATCH v2 00/11] x86-64: Stack protector and percpu improvements Brian Gerst
2023-10-26 16:00 ` [PATCH v2 01/11] x86/stackprotector/32: Remove stack protector test script Brian Gerst
2023-10-26 17:59 ` Uros Bizjak
2023-10-26 16:00 ` [PATCH v2 02/11] x86/stackprotector/64: " Brian Gerst
2023-10-26 18:06 ` Uros Bizjak
2023-10-26 16:00 ` [PATCH v2 03/11] x86/boot: Disable stack protector for early boot code Brian Gerst
2023-10-26 16:00 ` [PATCH v2 04/11] x86/pvh: Use fixed_percpu_data for early boot GSBASE Brian Gerst
2023-10-26 16:00 ` [PATCH v2 05/11] x86/stackprotector/64: Convert stack protector to normal percpu variable Brian Gerst
2023-10-26 18:16 ` Uros Bizjak
2023-10-29 1:26 ` kernel test robot
2023-10-29 6:56 ` Brian Gerst
2023-10-29 17:00 ` Brian Gerst
2023-10-30 15:24 ` Nick Desaulniers
2023-10-30 17:19 ` Brian Gerst
2023-11-01 21:21 ` Fangrui Song
2023-10-26 16:00 ` [PATCH v2 06/11] x86/percpu/64: Remove fixed_percpu_data Brian Gerst
2023-10-26 18:28 ` Uros Bizjak
2023-10-26 16:00 ` [PATCH v2 07/11] x86/percpu/64: Use relative percpu offsets Brian Gerst
2023-10-26 18:47 ` Uros Bizjak
2023-10-27 2:09 ` Brian Gerst
2023-10-27 6:09 ` Uros Bizjak
2023-10-26 16:00 ` [PATCH v2 08/11] x86/boot/64: Remove inverse relocations Brian Gerst
2023-10-26 16:00 ` [PATCH v2 09/11] x86/percpu/64: Remove INIT_PER_CPU macros Brian Gerst
2023-10-26 18:48 ` Uros Bizjak
2023-10-26 16:00 ` [PATCH v2 10/11] percpu: Remove PER_CPU_FIRST_SECTION Brian Gerst
2023-10-26 18:51 ` Uros Bizjak
2023-10-26 16:01 ` [PATCH v2 11/11] kallsyms: Remove KALLSYMS_ABSOLUTE_PERCPU Brian Gerst
2023-10-29 21:42 ` [PATCH v2 00/11] x86-64: Stack protector and percpu improvements David Laight
2023-10-29 23:19 ` Brian Gerst
2023-10-30 8:06 ` Uros Bizjak
2023-10-30 9:05 ` David Laight [this message]
2023-10-30 9:10 ` Uros Bizjak
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