[PATCH v3] kcmp: Support selection of SYS_kcmp without CHECKPOINT_RESTORE

[Emil Velikov]

On Fri, 5 Feb 2021 at 22:01, Chris Wilson <chris at chris-wilson.co.uk> wrote:
>
> Userspace has discovered the functionality offered by SYS_kcmp and has
> started to depend upon it. In particular, Mesa uses SYS_kcmp for
> os_same_file_description() in order to identify when two fd (e.g. device
> or dmabuf)

As you rightfully point out, SYS_kcmp is a bit of a two edged sword.
While you mention the CONFIG issue, there is also a portability aspect
(mesa runs on more than just linux) and as well as sandbox filtering
of the extra syscall.

Last time I looked, the latter was still an issue and mesa was using
SYS_kcmp to compare device node fds.
A far shorter and more portable solution is possible, so let me
prepare a Mesa patch.

-Emil