Re: [PATCH v3 2/4] pid: Add PIDFD_IOCTL_GETFD to fetch file descriptors from processes

[Christian Brauner]

On Tue, Dec 17, 2019 at 09:54:40AM +0100, Arnd Bergmann wrote:
> On Tue, Dec 17, 2019 at 3:50 AM Sargun Dhillon <sargun@xxxxxxxxx> wrote:
> > On Mon, Dec 16, 2019 at 5:50 PM Christian Brauner <christian.brauner@xxxxxxxxxx> wrote:
> Finally, there is the question whether this should be an ioctl
> operation at all, or
> if it would better be done as a proper syscall. Functionally the two
> are the same
> here, but doing such a fundamental operation as an ioctl doesn't feel
> quite right
> to me. As a system call, this could be something like
> 
> int pidfd_get_fd(int pidfd, int their_fd, int flags);
> 
> along the lines of dup3().

Thanks for taking a look, Arnd!

Yeah, Oleg hinted at this in the first version as well. I originally
disagreed but we can sure also do this as a separate syscall.
What we should keep in mind is that people already brought up adding new
fds to a task. Which is not a problem just something to remember as it
might potentially mean another syscall.

Christian