[LTP] [PATCH] userfaultfd: Use two-step handshake to probe features

[Ricardo Branco]

userfaultfd05 and userfaultfd06 assume that
UFFD_FEATURE_PAGEFAULT_FLAG_WP and UFFD_FEATURE_POISON are available
when setting up userfaultfd.

On kernels where either feature is unavailable at runtime,
UFFDIO_API fails with EINVAL and the tests end up as TBROK instead of
being skipped.

Fix this by using the required two-step handshake and skip with TCONF
if the required feature bit is absent.

Also remove userfaultfd05's needs_kconfigs check, since runtime
feature probing is sufficient here.

Link: https://github.com/linux-test-project/ltp/issues/1289

Signed-off-by: Ricardo Branco <rbranco@suse.de>
---
 testcases/kernel/syscalls/userfaultfd/userfaultfd05.c | 11 +++++++----
 testcases/kernel/syscalls/userfaultfd/userfaultfd06.c | 10 +++++++---
 2 files changed, 14 insertions(+), 7 deletions(-)

diff --git a/testcases/kernel/syscalls/userfaultfd/userfaultfd05.c b/testcases/kernel/syscalls/userfaultfd/userfaultfd05.c
index e25a227cf..5412f12e1 100644
--- a/testcases/kernel/syscalls/userfaultfd/userfaultfd05.c
+++ b/testcases/kernel/syscalls/userfaultfd/userfaultfd05.c
@@ -89,7 +89,14 @@ static void run(void)
 	set_pages();
 
 	uffd = SAFE_USERFAULTFD(O_CLOEXEC | O_NONBLOCK, false);
+	uffdio_api.api = UFFD_API;
+	uffdio_api.features = 0;
+	SAFE_IOCTL(uffd, UFFDIO_API, &uffdio_api);
+	if (!(uffdio_api.features & UFFD_FEATURE_PAGEFAULT_FLAG_WP))
+		tst_brk(TCONF, "UFFD_FEATURE_PAGEFAULT_FLAG_WP not supported");
+	SAFE_CLOSE(uffd);
 
+	uffd = SAFE_USERFAULTFD(O_CLOEXEC | O_NONBLOCK, false);
 	uffdio_api.api = UFFD_API;
 	uffdio_api.features = UFFD_FEATURE_PAGEFAULT_FLAG_WP;
 
@@ -124,8 +131,4 @@ static void run(void)
 static struct tst_test test = {
 	.test_all = run,
 	.min_kver = "5.7",
-	.needs_kconfigs = (const char *[]) {
-		"CONFIG_HAVE_ARCH_USERFAULTFD_WP=y",
-		NULL
-	}
 };
diff --git a/testcases/kernel/syscalls/userfaultfd/userfaultfd06.c b/testcases/kernel/syscalls/userfaultfd/userfaultfd06.c
index 5b1252c35..7ad682f5a 100644
--- a/testcases/kernel/syscalls/userfaultfd/userfaultfd06.c
+++ b/testcases/kernel/syscalls/userfaultfd/userfaultfd06.c
@@ -100,15 +100,19 @@ static void run(void)
 	set_pages();
 
 	uffd = SAFE_USERFAULTFD(O_CLOEXEC | O_NONBLOCK, false);
+	uffdio_api.api = UFFD_API;
+	uffdio_api.features = 0;
+	SAFE_IOCTL(uffd, UFFDIO_API, &uffdio_api);
+	if (!(uffdio_api.features & UFFD_FEATURE_POISON))
+		tst_brk(TCONF, "UFFD_FEATURE_POISON not supported");
+	SAFE_CLOSE(uffd);
 
+	uffd = SAFE_USERFAULTFD(O_CLOEXEC | O_NONBLOCK, false);
 	uffdio_api.api = UFFD_API;
 	uffdio_api.features = UFFD_FEATURE_POISON;
 
 	SAFE_IOCTL(uffd, UFFDIO_API, &uffdio_api);
 
-	if (!(uffdio_api.features & UFFD_FEATURE_POISON))
-		tst_brk(TCONF, "UFFD_FEATURE_POISON not supported");
-
 	uffdio_register.range.start = (unsigned long) page;
 	uffdio_register.range.len = page_size;
 	uffdio_register.mode = UFFDIO_REGISTER_MODE_MISSING;
-- 
2.53.0