linux-kernel - Re: [PATCH v1 2/2] signal: add procfd

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Date:   Mon, 19 Nov 2018 16:34:00 -0800
From:   Andy Lutomirski <luto@...nel.org>
To:     Christian Brauner <christian@...uner.io>
Cc:     Andrew Lutomirski <luto@...nel.org>,
        Tycho Andersen <tycho@...ho.ws>,
        Daniel Colascione <dancol@...gle.com>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        LKML <linux-kernel@...r.kernel.org>,
        "Serge E. Hallyn" <serge@...lyn.com>, Jann Horn <jannh@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Oleg Nesterov <oleg@...hat.com>,
        Aleksa Sarai <cyphar@...har.com>,
        Al Viro <viro@...iv.linux.org.uk>,
        Linux FS Devel <linux-fsdevel@...r.kernel.org>,
        Linux API <linux-api@...r.kernel.org>,
        Tim Murray <timmurray@...gle.com>,
        linux-man <linux-man@...r.kernel.org>,
        Kees Cook <keescook@...omium.org>
Subject: Re: [PATCH v1 2/2] signal: add procfd_signal() syscall

On Mon, Nov 19, 2018 at 4:33 PM Christian Brauner <christian@...uner.io> wrote:
>
> On Mon, Nov 19, 2018 at 04:27:49PM -0800, Andy Lutomirski wrote:
> > On Mon, Nov 19, 2018 at 3:07 PM Tycho Andersen <tycho@...ho.ws> wrote:
> > > > These tools also care about ioctls. Adding a system call is a pain,
> > > > but the solution is to make adding system calls less of a pain, not to
> > > > permanently make the Linux ABI worse.
> > >
> > > For user-defined values of "worse" :)
> > >
> >
> > I tend to agree with Tycho here.  But I'm wondering if it might be
> > worth considering a better ioctl.
> >
> > /me dons flame-proof hat
> >
> > We could do:
> >
> > long better_ioctl(int fd, u32 nr, const void *inbuf, size_t inlen,
> > const void *outbuf, size_t outlen);
>
> I'm the writer of this patch so take this with a grain of salt.
> I think it is a bad idea to stop this patch and force us to introduce a
> new type of ioctl().

I agree completely.

> An ioctl() is also not easy to use for this task because we want to add
> a siginfo_t argument which I actually think provides value and makes
> this interface more useful.
>

You could always have a struct procfd_kill and pass a pointer to
*that*.  But sure, it's ugly.