Date: Fri, 31 Jul 2015 15:08:28 -0700
From: josh@joshtriplett.org
To: Andy Lutomirski <luto@amacapital.net>
Cc: Kees Cook <keescook@chromium.org>, David Drysdale <drysdale@google.com>,
        Ingo Molnar <mingo@kernel.org>, Linux API <linux-api@vger.kernel.org>,
        Michael Kerrisk <mtk.manpages@gmail.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Arnd Bergmann <arnd@arndb.de>, Shuah Khan <shuahkh@osg.samsung.com>,
        Jonathan Corbet <corbet@lwn.net>, Eric B Munson <emunson@akamai.com>,
        Randy Dunlap <rdunlap@infradead.org>,
        Andrea Arcangeli <aarcange@redhat.com>,
        Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>,
        "H. Peter Anvin" <hpa@zytor.com>, Oleg Nesterov <oleg@redhat.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Al Viro <viro@zeniv.linux.org.uk>,
        Rusty Russell <rusty@rustcorp.com.au>,
        Peter Zijlstra <peterz@infradead.org>, Vivek Goyal <vgoyal@redhat.com>,
        Alexei Starovoitov <ast@plumgrid.com>,
        David Herrmann <dh.herrmann@gmail.com>,
        "Theodore Ts'o" <tytso@mit.edu>, Milosz Tanski <milosz@adfin.com>,
        Fam Zheng <famz@redhat.com>,
        Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
        "linux-doc@vger.kernel.org" <linux-doc@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Peter Zijlstra <a.p.zijlstra@chello.nl>
Subject: Re: [PATCHv2 1/1] Documentation: describe how to add a system call
Message-ID: <20150731220828.GA30890@cloud>
References: <1438242731-27756-2-git-send-email-drysdale@google.com>
 <20150730083831.GA22182@gmail.com>
 <CAHse=S-Wgv8JKu72FQaivou1PAwyexqjn_sjtMu3n=ezX0x-vg@mail.gmail.com>
 <CAGXu5j+5KHy68ELU6PmNWaj7mQBXTbRQGXqJFwsXHt9n0LPw8Q@mail.gmail.com>
 <20150730190434.GD16452@x>
 <CAGXu5jJwtVgPmmMHiR0M27he3ma7exfSH8OBNdLMFQcbbtzUfg@mail.gmail.com>
 <20150731010234.GA7265@x>
 <CAGXu5jLethUkiq1QEZg-uRkOzofa6M8WCT8T7qAByWy5L4xHBw@mail.gmail.com>
 <20150731205941.GA30362@cloud>
 <CALCETrUkMXvFRKdTH7ekY7FyGvbKDDJbf7L0shgs5R-Hep6bVA@mail.gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <CALCETrUkMXvFRKdTH7ekY7FyGvbKDDJbf7L0shgs5R-Hep6bVA@mail.gmail.com>
User-Agent: Mutt/1.5.20 (2009-06-14)
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1327
Lines: 25

On Fri, Jul 31, 2015 at 02:19:29PM -0700, Andy Lutomirski wrote:
> On Fri, Jul 31, 2015 at 1:59 PM,  <josh@joshtriplett.org> wrote:
> > Agreed.  I think the proposal above would be a net improvement, but
> > ideally you'd want something that's annotated and generates automatic
> > marshalling code.
> >
> 
> I assume this is idle musing.  If, however, we were to actually do
> this, I'd suggest we seriously consider speaking the Cap'n Proto
> serialization format.  It's quite nice, it encodes and decodes *very*
> quickly and, unlike TLV schemes, you don't have to read it in order,
> making the read-side code less awkward.

That seems like *massive* overkill for a kernel<->userspace syscall
interface.  I was more thinking about having a few standardized marshal
types, and incrementally adding more when more patterns show up.  For a
first pass, just automatically running copy_from_user and
copy_param_struct on appropriate sets of __user parameters identified as
such in a structured text file seems quite sufficient.  (Plus
automatically generating syscalls.h from that.)
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/