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Message-ID: <a094c7da294a4827994af72249262593@AcuMS.aculab.com>
Date: Sun, 29 Oct 2023 21:42:41 +0000
From: David Laight <David.Laight@...LAB.COM>
To: 'Brian Gerst' <brgerst@...il.com>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"x86@...nel.org" <x86@...nel.org>
CC: Ingo Molnar <mingo@...nel.org>,
Thomas Gleixner <tglx@...utronix.de>,
Borislav Petkov <bp@...en8.de>,
"H . Peter Anvin" <hpa@...or.com>,
"Peter Zijlstra" <peterz@...radead.org>,
Uros Bizjak <ubizjak@...il.com>
Subject: RE: [PATCH v2 00/11] x86-64: Stack protector and percpu improvements
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.
David
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