linux-kernel - Re: Rust kernel policy

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Message-ID: <6E8DAA21-2CCE-4E53-A5A8-3B82D4A2334C@zytor.com>
Date: Thu, 20 Feb 2025 04:01:28 -0800
From: "H. Peter Anvin" <hpa@...or.com>
To: Alexey Dobriyan <adobriyan@...il.com>
CC: Kees Cook <kees@...nel.org>,
        Miguel Ojeda <miguel.ojeda.sandonis@...il.com>,
        Christoph Hellwig <hch@...radead.org>,
        rust-for-linux <rust-for-linux@...r.kernel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Greg KH <gregkh@...uxfoundation.org>, David Airlie <airlied@...il.com>,
        linux-kernel@...r.kernel.org, ksummit@...ts.linux.dev
Subject: Re: Rust kernel policy

On February 19, 2025 10:32:15 PM PST, Alexey Dobriyan <adobriyan@...il.com> wrote:
>On Wed, Feb 19, 2025 at 11:33:56AM -0800, H. Peter Anvin wrote:
>> b. Can we use existing mature tools, such as C++, to *immediately* improve the quality (not just memory safety!) of our 37-year-old, 35-million line code base and allow for further centralized improvements without the major lag required for compiler extensions to be requested and implemented in gcc (and clang) *and* dealing with the maturity issue?
>
>We can't and for technical reasons:
>
>* g++ requires C99 initializers to be in declaration order,
>  even in cases where there is no reason to do so.
>
>* g++ doesn't support __seg_gs at all:
>
>	$ echo -n -e 'int __seg_gs gs;' | g++ -xc++ - -S -o /dev/null
>	<stdin>:1:14: error: expected initializer before ‘gs’
>
>  x86 added this to improve codegen quality so this would be step backwards.

Ok, so those are obvious problems, and I agree that having to rely on the legacy implementation of gs: is undesirable as anything than a transaction crutch.