kselftest: fix TAP output for skipped tests

According to the TAP specification, a skipped test must be marked as "ok"
and annotated with the SKIP directive, for example

   ok 23 # skip Insufficient flogiston pressure.
   (https://testanything.org/tap-specification.html)

Fix the kselftest infrastructure to match this.

For ksft_exit_skip, it is preferrable to emit a dummy plan line that
indicates the whole test was skipped, but this is not always possible
because of ksft_exit_skip being used as a "shortcut" by the tests.
In that case, print the test counts and a normal "ok" line.  The format
is now the same independent of whether msg is NULL or not (but it is
never NULL in any caller right now).
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

tools/testing/selftests/kselftest.h

@@ -128,7 +128,7 @@ static inline void ksft_test_result_skip(const char *msg, ...)
 	ksft_cnt.ksft_xskip++;
 
 	va_start(args, msg);
-	printf("not ok %d # SKIP ", ksft_test_num());
+	printf("ok %d # SKIP ", ksft_test_num());
 	errno = saved_errno;
 	vprintf(msg, args);
 	va_end(args);
@@ -190,18 +190,30 @@ static inline int ksft_exit_xpass(void)
 
 static inline int ksft_exit_skip(const char *msg, ...)
 {
-	if (msg) {
-		int saved_errno = errno;
-		va_list args;
+	int saved_errno = errno;
+	va_list args;
 
-		va_start(args, msg);
-		printf("not ok %d # SKIP ", 1 + ksft_test_num());
+	va_start(args, msg);
+
+	/*
+	 * FIXME: several tests misuse ksft_exit_skip so produce
+	 * something sensible if some tests have already been run
+	 * or a plan has been printed.  Those tests should use
+	 * ksft_test_result_skip or ksft_exit_fail_msg instead.
+	 */
+	if (ksft_plan || ksft_test_num()) {
+		ksft_cnt.ksft_xskip++;
+		printf("ok %d # SKIP ", 1 + ksft_test_num());
+	} else {
+		printf("1..0 # SKIP ");
+	}
+	if (msg) {
 		errno = saved_errno;
 		vprintf(msg, args);
 		va_end(args);
-	} else {
-		ksft_print_cnts();
 	}
+	if (ksft_test_num())
+		ksft_print_cnts();
 	exit(KSFT_SKIP);
 }
 

tools/testing/selftests/kselftest/runner.sh

@@ -77,7 +77,7 @@ run_one()
 		echo "ok $test_num $TEST_HDR_MSG") ||
 		(rc=$?;	\
 		if [ $rc -eq $skip_rc ]; then	\
-			echo "not ok $test_num $TEST_HDR_MSG # SKIP"
+			echo "ok $test_num $TEST_HDR_MSG # SKIP"
 		elif [ $rc -eq $timeout_rc ]; then \
 			echo "#"
 			echo "not ok $test_num $TEST_HDR_MSG # TIMEOUT"