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From:   Andy Lutomirski <luto@kernel.org>
Date:   Fri, 30 Nov 2018 15:46:22 -0800
Message-ID: <CALCETrWcUQC_aeHRwVF0yr8GATndRU9277rQQ+caOcR1uJ1W9g@mail.gmail.com>
Subject: Re: [PATCH v2] signal: add procfd_signal() syscall
To:     Christian Brauner <christian@brauner.io>
Cc:     Arnd Bergmann <arnd@arndb.de>,
        Daniel Colascione <dancol@google.com>,
        Andrew Lutomirski <luto@kernel.org>,
        "Eric W. Biederman" <ebiederm@xmission.com>,
        Florian Weimer <fweimer@redhat.com>,
        LKML <linux-kernel@vger.kernel.org>,
        "Serge E. Hallyn" <serge@hallyn.com>, Jann Horn <jannh@google.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Oleg Nesterov <oleg@redhat.com>,
        Aleksa Sarai <cyphar@cyphar.com>,
        Al Viro <viro@zeniv.linux.org.uk>,
        Linux FS Devel <linux-fsdevel@vger.kernel.org>,
        Linux API <linux-api@vger.kernel.org>,
        Tim Murray <timmurray@google.com>,
        linux-man <linux-man@vger.kernel.org>,
        Kees Cook <keescook@chromium.org>
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On Fri, Nov 30, 2018 at 3:40 PM Christian Brauner <christian@brauner.io> wrote:
>
> On December 1, 2018 12:12:53 PM GMT+13:00, Arnd Bergmann <arnd@arndb.de> wrote:
> >On Sat, Dec 1, 2018 at 12:05 AM Daniel Colascione <dancol@google.com>
> >wrote:
> >> On Fri, Nov 30, 2018 at 2:26 PM Christian Brauner
> ><christian@brauner.io> wrote:
> >> > On December 1, 2018 11:09:58 AM GMT+13:00, Arnd Bergmann
> ><arnd@arndb.de> wrote:
> >> >
> >> > One humble point I would like to make is that what I care about
> >most is a sensible way forward without having to redo essential parts
> >of how syscalls work.
> >> > I don't want to introduce a sane, small syscall that ends up
> >breaking all over the place because we decided to fix past mistakes
> >that technically have nothing to do with the patch itself.
> >> > However, I do sympathize and understand these concerns.
> >>
> >> IMHO, it's fine to just replicate all the splits we have for the
> >> existing signal system calls. It's ugly, but once it's done, it'll be
> >> done for a long time. I can't see a need to add even more signal
> >> system calls after this one.
> >
> >We definitely need waitid_time64() and rt_sigtimedwait_time64()
> >in the very near future.
>
> Right, I remember you pointing this out in a prior mail.
> Thanks for working on this for such a long time now, Arnd!
> Can we agree to move on with the procfd syscall given the current constraints?
> I just don't want to see the syscall being
> blocked by a generic problem whose
> ultimate solution is to get rid of weird
> architectural constraints.

Creating and using a copy_siginfo_from_user64() function would work
for everyone, no?