userfaultfd: Do not use min_kver as gate for test

Do not use .min_kver to decide whether the test should run and instead
check for the presence of /dev/userfaultfd at runtime.

Closes: #1285
Reviewed-by: Martin Doucha <mdoucha@suse.cz>
Reviewed-by: Cyril Hrubis <chrubis@suse.cz>
Reviewed-by: Petr Vorel <pvorel@suse.cz>
Signed-off-by: Ricardo Branco <rbranco@suse.de>

Author: ricardobranco777

testcases/kernel/syscalls/userfaultfd/userfaultfd03.c

@@ -13,6 +13,7 @@
 
 #include "config.h"
 #include <poll.h>
+#include <unistd.h>
 #include "tst_test.h"
 #include "tst_safe_macros.h"
 #include "tst_safe_pthread.h"
@@ -23,6 +24,15 @@ static char *page;
 static void *copy_page;
 static int uffd;
 
+static void setup(void)
+{
+	if (access("/dev/userfaultfd", F_OK) != 0) {
+		int res = (tst_kvercmp(6, 1, 0) < 0) ? TCONF : TBROK;
+
+		tst_brk(res, "/dev/userfaultfd not found");
+	}
+}
+
 static int open_userfaultfd(int flags)
 {
 	int fd, fd2;
@@ -117,6 +127,10 @@ static void run(void)
 
 static struct tst_test test = {
 	.needs_root = 1,
+	.setup = setup,
 	.test_all = run,
-	.min_kver = "5.11",
+	.needs_kconfigs = (const char *[]) {
+		"CONFIG_USERFAULTFD=y",
+		NULL
+	}
 };