Re: [PATCH 2/4] selftests/sigaltstack: Fix the sas test on old kernels

The handling for old kernels was wrong.  Fix it.

Reported-by: Ingo Molnar <redacted>
Cc: Stas Sergeev <redacted>
Cc: Al Viro <viro-RmSDqhL/yNMiFSDQTTA3OLVCufUGDwFn@public.gmane.org>
Cc: Andrew Morton <akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>
Cc: Andy Lutomirski <redacted>
Cc: Borislav Petkov <redacted>
Cc: Brian Gerst <redacted>
Cc: Denys Vlasenko <redacted>
Cc: H. Peter Anvin <redacted>
Cc: Linus Torvalds <torvalds-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>
Cc: Oleg Nesterov <redacted>
Cc: Pavel Emelyanov <redacted>
Cc: Peter Zijlstra <redacted>
Cc: Shuah Khan <redacted>
Cc: Thomas Gleixner <redacted>
Cc: linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Cc: linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Signed-off-by: Andy Lutomirski <redacted>
---
  tools/testing/selftests/sigaltstack/sas.c | 21 ++++++++++++++-------
  1 file changed, 14 insertions(+), 7 deletions(-)

diff --git a/tools/testing/selftests/sigaltstack/sas.c b/tools/testing/selftests/sigaltstack/sas.c
index 57da8bfde60b..a98c3ef8141f 100644
--- a/tools/testing/selftests/sigaltstack/sas.c
+++ b/tools/testing/selftests/sigaltstack/sas.c

@@ -15,6 +15,7 @@
  #include <alloca.h>
  #include <string.h>
  #include <assert.h>
+#include <errno.h>
  
  #ifndef SS_AUTODISARM
  #define SS_AUTODISARM  (1 << 4)

@@ -117,13 +118,19 @@ int main(void)
  	stk.ss_flags = SS_ONSTACK | SS_AUTODISARM;
  	err = sigaltstack(&stk, NULL);
  	if (err) {
-		perror("[FAIL]\tsigaltstack(SS_ONSTACK | SS_AUTODISARM)");
-		stk.ss_flags = SS_ONSTACK;
-	}
-	err = sigaltstack(&stk, NULL);
-	if (err) {
-		perror("[FAIL]\tsigaltstack(SS_ONSTACK)");
-		return EXIT_FAILURE;
+		if (errno == EINVAL) {
+			printf("[NOTE]\tThe running kernel doesn't support SS_AUTODISARM\n");
+			/*
+			 * If test cases for the !SS_AUTODISARM variant were
+			 * added, we could still run them.  We don't have any
+			 * test cases like that yet, so just exit and report
+			 * success.
+			 */