[LTP] userfaultfd: Add helper for checking UFFD feature support

[linuxtestproject.agent@gmail.com]

Hi Ricardo,

--- [PATCH 1/3] ---

On Thu, 7 May 2026 14:28:53 +0200, Ricardo Branco wrote:
> [PATCH 1/3] userfaultfd: Add helper for checking UFFD feature support

> +	uffd = SAFE_USERFAULTFD(O_CLOEXEC | O_NONBLOCK, false);
> +
> +	uffdio_api.api = UFFD_API;
> +	SAFE_IOCTL(uffd, UFFDIO_API, &uffdio_api);

If SAFE_IOCTL calls tst_brk(TBROK) here, the local `uffd` is not
closed before the test runner takes over; the cleanup functions only
track the global `uffd`. Close it before the SAFE_IOCTL call, or
restructure to guarantee SAFE_CLOSE on all exit paths.

--- [PATCH 2/3] ---

On Thu, 7 May 2026 14:28:54 +0200, Ricardo Branco wrote:
> [PATCH 2/3] userfaultfd: Use two-step handshake to probe features

> Fixes: 1840ee23d172b5ab04cca7c2acfa48755b041911

This commit is not reachable in the local git history (grafted shallow
clone). Please verify the Fixes: tag resolves correctly against the
upstream LTP tree.

Pre-existing issues noticed in the surrounding code (not introduced
by this patch):

- testcases/kernel/syscalls/userfaultfd/userfaultfd06.c:142 — no
  .min_kver set; UFFD_FEATURE_POISON requires Linux 6.6.

---
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