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

- From: Jürg Billeter \<hidden\>
- Date: 2019-03-30 12:00:30 
- List: linux-api
- Page: https://ratatoskr.run/linux-api/2019/03/5555579
- Thread: https://ratatoskr.run/linux-api/2019/03/5554749/t.md

```text
On Fri, 2019-03-29 at 16:54 +0100, Christian Brauner wrote:
> diff --git a/include/uapi/linux/wait.h b/include/uapi/linux/wait.h
> index ac49a220cf2a..d6c7c0701997 100644
> --- a/include/uapi/linux/wait.h
> +++ b/include/uapi/linux/wait.h
> @@ -18,5 +18,7 @@
>  #define P_PID		1
>  #define P_PGID		2
>  
> +/* Get a file descriptor for /proc/<pid> of the corresponding pidfd
> */
> +#define PIDFD_GET_PROCFD _IOR('p', 1, int)
>  
>  #endif /* _UAPI_LINUX_WAIT_H */

This is missing an entry in Documentation/ioctl/ioctl-number.txt and is
actually conflicting with existing entries.

However, I'd actually prefer a syscall to allow strict whitelisting via
seccomp and avoid the other ioctl disadvantages that Daniel has already
mentioned.

Cheers,
Jürg
```