# Re: \[PATCH v2 2/5\] pid: add pidfd\_open()

- From: Christian Brauner \<christian@brauner.io\>
- Date: 2019-03-29 23:55:28 
- List: linux-api
- Page: https://ratatoskr.run/linux-api/2019/03/5555078
- Thread: https://ratatoskr.run/linux-api/2019/03/5554749/t.md

```text
On Sat, Mar 30, 2019 at 12:45:46AM +0100, Jann Horn wrote:
> On Fri, Mar 29, 2019 at 4:54 PM Christian Brauner [ref] wrote:
> > /* Introduction */
> > This adds the pidfd_open() syscall.
> > pidfd_open() allows to retrieve file descriptors for a given pid. This
> > includes both file descriptors for processes and file descriptors for
> > threads.
> 
> Looks good to me, overall. Apart from a few nits below:
> Reviewed-by: Jann Horn <jannh@google.com>

Thanks! Will fixup the nits and add your Reviewed-by!

> 
> [...]
> > diff --git a/kernel/pid.c b/kernel/pid.c
> > index 20881598bdfa..8c9e15e0e463 100644
> > --- a/kernel/pid.c
> > +++ b/kernel/pid.c
> [...]
> > +static struct file *pidfd_open_proc_pid(const struct file *procf, pid_t pid,
> > +                                       const struct pid *pidfd_pid)
> > +{
> > +       char name[12]; /* int to strlen + \0 but with */
> 
> nit: comment suddenly ends at "but with"?

Will fix.

> 
> [...]
> > +}
> > +
> > +static inline int pidfd_to_procfd(int procfd, struct file *pidfd_file)
> > +{
> > +       long fd;
> 
> nit: This should probably be an int?

Yes.

> 
> [...]
> > +       return fd;
> > +}
> [...]
> > +static long pidfd_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
> > +{
> > +       int procfd = arg;
> 
> nit: I think it'd be semantically cleaner to move this assignment into
> the switch case, but I don't feel about it strongly.

Agreed.

> 
> > +       switch (cmd) {
> > +       case PIDFD_GET_PROCFD:
> > +               return pidfd_to_procfd(procfd, file);
> > +       default:
> > +               return -ENOTTY;
> > +       }
> > +}
```