linux-kernel - [PATCH v3 2/4] userfaultfd: selftest: Skip test if userfaultfd() syscall not supported

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Date:   Tue, 28 Aug 2018 14:26:06 -0300
From:   Thiago Jung Bauermann <bauerman@...ux.ibm.com>
To:     linux-kselftest@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, Shuah Khan <shuah@...nel.org>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Mike Rapoport <rppt@...ux.vnet.ibm.com>,
        Prakash Sangappa <prakash.sangappa@...cle.com>,
        Thiago Jung Bauermann <bauerman@...ux.ibm.com>
Subject: [PATCH v3 2/4] userfaultfd: selftest: Skip test if userfaultfd() syscall not supported

Since there's no point in doing anything in this case, immediately exit the
process.

And take the opportunity to improve the error message.

Before:

  # ./userfaultfd shmem 10 10
  nr_pages: 160, nr_pages_per_cpu: 40
  userfaultfd syscall not available in this kernel
  # echo $?
  1

After:

  # ./userfaultfd shmem 10 10
  nr_pages: 160, nr_pages_per_cpu: 40
  userfaultfd syscall not available in this kernel: Function not implemented
  # echo $?
  4

Suggested-by: Mike Rapoport <rppt@...ux.vnet.ibm.com>
Signed-off-by: Thiago Jung Bauermann <bauerman@...ux.ibm.com>
Acked-by: Mike Rapoport <rppt@...ux.vnet.ibm.com>
---
 tools/testing/selftests/vm/userfaultfd.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/tools/testing/selftests/vm/userfaultfd.c b/tools/testing/selftests/vm/userfaultfd.c
index e4099afe7557..d728bd1cb33c 100644
--- a/tools/testing/selftests/vm/userfaultfd.c
+++ b/tools/testing/selftests/vm/userfaultfd.c
@@ -636,9 +636,11 @@ static int userfaultfd_open(int features)
 
 	uffd = syscall(__NR_userfaultfd, O_CLOEXEC | O_NONBLOCK);
 	if (uffd < 0) {
-		fprintf(stderr,
-			"userfaultfd syscall not available in this kernel\n");
-		return 1;
+		int errnum = errno;
+
+		perror("userfaultfd syscall not available in this kernel");
+
+		exit(errnum == ENOSYS ? KSFT_SKIP : 1);
 	}
 	uffd_flags = fcntl(uffd, F_GETFD, NULL);