linux-kernel - Re: [PATCH 2/5] pidfd: add pidfd

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Date:   Fri, 26 Jul 2019 10:24:13 +0200
From:   Christian Brauner <christian@...uner.io>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Oleg Nesterov <oleg@...hat.com>,
        "Eric W . Biederman" <ebiederm@...ssion.com>,
        Kees Cook <keescook@...omium.org>,
        Joel Fernandes <joel@...lfernandes.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Tejun Heo <tj@...nel.org>, David Howells <dhowells@...hat.com>,
        Jann Horn <jannh@...gle.com>,
        Andy Lutomirski <luto@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Aleksa Sarai <cyphar@...har.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Al Viro <viro@...iv.linux.org.uk>,
        Android Kernel Team <kernel-team@...roid.com>,
        Linux API <linux-api@...r.kernel.org>
Subject: Re: [PATCH 2/5] pidfd: add pidfd_wait()

On Fri, Jul 26, 2019 at 10:19:55AM +0200, Arnd Bergmann wrote:
> On Wed, Jul 24, 2019 at 4:47 PM Christian Brauner <christian@...uner.io> wrote:
> 
> > +
> > +static int copy_rusage_to_user_any(struct rusage *kru, struct rusage __user *ru)
> > +{
> > +#ifdef CONFIG_COMPAT
> > +       if (in_compat_syscall())
> > +               return put_compat_rusage(kru, (struct compat_rusage __user *)ru);
> > +#endif
> > +       return copy_to_user(ru, kru, sizeof(*kru));
> > +}
> 
> I think this code needs a check for COMPAT_USE_64BIT_TIME in order
> to handle x32 correctly.

Similar to waitid(), indeed.

> 
> It would be nice to introduce it in a separate patch, and then use it
> to kill off
> compat_sys_getrusage() and compat_sys_wait4(), and possibly even
> compat_sys_waitid() in combination with your copy_siginfo_to_user_any().
> That could be done as a cleanup patch afterwards, or as part of your series.

Right, but we won't go the syscall route but instead go the P_PIDFD
route for waitid(). :)

Christian