linux-kernel - Re: [patch V3 01/13] entry: Provide generic syscall entry functionality

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 for Android: free password hash cracker in your pocket

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

Message-ID: <875zakq56t.fsf@nanos.tec.linutronix.de>
Date:   Sat, 18 Jul 2020 16:16:26 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Andy Lutomirski <luto@...nel.org>
Cc:     Kees Cook <keescook@...omium.org>,
        LKML <linux-kernel@...r.kernel.org>, X86 ML <x86@...nel.org>,
        linux-arch <linux-arch@...r.kernel.org>,
        Will Deacon <will@...nel.org>, Arnd Bergmann <arnd@...db.de>,
        Mark Rutland <mark.rutland@....com>,
        Keno Fischer <keno@...iacomputing.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        kvm list <kvm@...r.kernel.org>,
        Gabriel Krisman Bertazi <krisman@...labora.com>
Subject: Re: [patch V3 01/13] entry: Provide generic syscall entry functionality

Andy Lutomirski <luto@...nel.org> writes:
> On Fri, Jul 17, 2020 at 12:29 PM Thomas Gleixner <tglx@...utronix.de> wrote:
>> The alternative is to play nasty games with TIF_IA32, TIF_ADDR32 and
>> TIF_X32 to free up bits for 32bit and make the flags field 64 bit on 64
>> bit kernels, but I prefer to do the above seperation.
>
> I'm all for cleaning it up, but I don't think any nasty games would be
> needed regardless.  IMO at least the following flags are nonsense and
> don't belong in TIF_anything at all:
>
> TIF_IA32, TIF_X32: can probably be deleted.  Someone would just need
> to finish the work.
> TIF_ADDR32: also probably removable, but I'm less confident.
> TIF_FORCED_TF: This is purely a ptrace artifact and could easily go
> somewhere else entirely.
>
> So getting those five bits back would be straightforward.
>
> FWIW, TIF_USER_RETURN_NOTIFY is a bit of an odd duck: it's an
> entry/exit word *and* a context switch word.  The latter is because
> it's logically a per-cpu flag, not a per-task flag, and the context
> switch code moves it around so it's always set on the running task.

Gah, I missed the context switch thing of that. That stuff is hideous.

Thanks,

       tglx