linux-kernel - Re: [PATCH v8 2/3] pid: Introduce pidfd

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Message-ID: <20200117231448.btck3qzepvtz5lcp@yavin>
Date:   Sat, 18 Jan 2020 10:14:48 +1100
From:   Aleksa Sarai <cyphar@...har.com>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     Sargun Dhillon <sargun@...gun.me>, linux-kernel@...r.kernel.org,
        containers@...ts.linux-foundation.org, linux-api@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, tycho@...ho.ws, jannh@...gle.com,
        christian.brauner@...ntu.com, oleg@...hat.com, luto@...capital.net,
        viro@...iv.linux.org.uk, gpascutto@...illa.com,
        ealvarez@...illa.com, fweimer@...hat.com, jld@...illa.com,
        arnd@...db.de
Subject: Re: [PATCH v8 2/3] pid: Introduce pidfd_getfd syscall

On 2020-01-17, Matthew Wilcox <willy@...radead.org> wrote:
> On Fri, Jan 03, 2020 at 08:29:27AM -0800, Sargun Dhillon wrote:
> > +SYSCALL_DEFINE3(pidfd_getfd, int, pidfd, int, fd,
> > +		unsigned int, flags)
> > +{
> > +	struct pid *pid;
> > +	struct fd f;
> > +	int ret;
> > +
> > +	/* flags is currently unused - make sure it's unset */
> > +	if (flags)
> > +		return -EINVAL;
> 
> Is EINVAL the right errno here?  Often we use ENOSYS for bad flags to
> syscalls.

I don't think that's right -- every syscall I've seen gives you -EINVAL
for invalid flags (not to mention -ENOSYS would mean userspace would be
confused as to whether the syscall is actually supported by the kernel).

-- 
Aleksa Sarai
Senior Software Engineer (Containers)
SUSE Linux GmbH
<https://www.cyphar.com/>

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