linux-kernel - Re: [RFC PATCH 0/4] x86/percpu: Use segment qualifiers

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAHk-=wg6P8pPg-x4BPUQj-wE0xC7HkGzFk89ftuji8MVo+RRxw@mail.gmail.com>
Date:   Sun, 1 Oct 2023 10:07:15 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Uros Bizjak <ubizjak@...il.com>
Cc:     x86@...nel.org, linux-kernel@...r.kernel.org,
        Andy Lutomirski <luto@...nel.org>,
        Ingo Molnar <mingo@...nel.org>, Nadav Amit <namit@...are.com>,
        Brian Gerst <brgerst@...il.com>,
        Denys Vlasenko <dvlasenk@...hat.com>,
        "H . Peter Anvin" <hpa@...or.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Borislav Petkov <bp@...en8.de>,
        Josh Poimboeuf <jpoimboe@...hat.com>
Subject: Re: [RFC PATCH 0/4] x86/percpu: Use segment qualifiers

On Sun, 1 Oct 2023 at 06:16, Uros Bizjak <ubizjak@...il.com> wrote:
>
> This patchset resurrect the work of Richard Henderson [1] and Nadav Amit [2]
> to introduce named address spaces compiler extension [3,4] into the linux kernel.

So apparently the extension has been around for a while (since gcc-6),
but I don't actually find any single major _user_ of it.

Debian code search finds exactly one case of it outside of the
compilers themselves:

  #  define THREAD_SELF \
    (*(struct pthread *__seg_fs *) offsetof (struct pthread, header.self))

in glibc/sysdeps/x86_64/nptl/tls.h, and even that isn't very widely
used (it seems to be a pthread_mutex implementation helper).

So the coverage testing of this thing seems very weak. Do we have any
other reason to believe that this is likely to actually be reliable
enough to use?

                     Linus