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From:   Daniel Colascione <dancol@google.com>
Date:   Mon, 25 Mar 2019 09:58:38 -0700
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Subject: Re: [PATCH 0/4] pid: add pidctl()
To:     David Howells <dhowells@redhat.com>
Cc:     Christian Brauner <christian@brauner.io>,
        Jann Horn <jannh@google.com>, khlebnikov@yandex-team.ru,
        Andy Lutomirski <luto@kernel.org>,
        "Serge E. Hallyn" <serge@hallyn.com>,
        "Eric W. Biederman" <ebiederm@xmission.com>,
        Linux API <linux-api@vger.kernel.org>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        Arnd Bergmann <arnd@arndb.de>,
        Kees Cook <keescook@chromium.org>,
        Alexey Dobriyan <adobriyan@gmail.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Michael Kerrisk-manpages <mtk.manpages@gmail.com>,
        bl0pbl33p@gmail.com, "Dmitry V. Levin" <ldv@altlinux.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Oleg Nesterov <oleg@redhat.com>,
        nagarathnam.muthusamy@oracle.com, Aleksa Sarai <cyphar@cyphar.com>,
        Al Viro <viro@zeniv.linux.org.uk>,
        Joel Fernandes <joel@joelfernandes.org>
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On Mon, Mar 25, 2019 at 9:56 AM David Howells <dhowells@redhat.com> wrote:
> Daniel Colascione <dancol@google.com> wrote:
>
> > System calls are cheap.
>
> Only to a point.  x86_64 will have an issue when we hit syscall 512.  We're
> currently at 427.

IIRC, a while ago, someone proposed restarting system call numbering
above (again, IIRC) 1024 for both 32- and 64-bit varieties to
establish a clean slate and sidestep this problem.