From: "H. Peter Anvin" <hpa@zytor.com>
To: Andy Lutomirski <luto@kernel.org>,
Brian Gerst <brgerst@gmail.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
the arch/x86 maintainers <x86@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@kernel.org>
Subject: Re: [PATCH 3/3] x86_64: Use relative per-cpu offsets
Date: Sat, 13 Nov 2021 20:24:11 -0800 [thread overview]
Message-ID: <47ea5a6a-025d-bcf2-d23a-be96cbcd36d3@zytor.com> (raw)
In-Reply-To: <719e0170-7645-4787-8c3a-676f34068c27@www.fastmail.com>
On 11/13/21 17:18, Andy Lutomirski wrote:
>
>
> On Sat, Nov 13, 2021, at 4:40 AM, Brian Gerst wrote:
>> The per-cpu section is currently linked at virtual address 0, because
>> older compilers hardcoded the stack protector canary value at a fixed
>> offset from the start of the GS segment. Use a standard relative offset
>> as the GS base when the stack protector is disabled, or a newer compiler
>> is used that supports a configurable location for the stack canary.
>
> Can you explain the benefit? Also, I think we should consider dropping support for the fixed model like we did on x86_32.
>
It would seem that UNLESS the fixed model is dropped, the benefit is
probably negative.
-hpa
next prev parent reply other threads:[~2021-11-14 4:24 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-13 12:40 [PATCH 0/3] x86-64: Stack protector and percpu improvements Brian Gerst
2021-11-13 12:40 ` [PATCH 1/3] x86-64: Use per-cpu stack canary if supported by compiler Brian Gerst
2021-11-13 12:40 ` [PATCH 2/3] x86/relocs: Make absolute percpu relocations conditional Brian Gerst
2021-11-13 12:40 ` [PATCH 3/3] x86_64: Use relative per-cpu offsets Brian Gerst
2021-11-14 1:18 ` Andy Lutomirski
2021-11-14 4:24 ` H. Peter Anvin [this message]
2021-11-14 4:54 ` Brian Gerst
2021-11-14 11:03 ` Peter Zijlstra
2021-11-14 18:29 ` Brian Gerst
2021-11-15 18:12 ` Andy Lutomirski
2021-11-15 20:44 ` Peter Zijlstra
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