[PATCH v3 0/4] userfaultfd: selftest: Improve behavior with older kernels

[PATCH v3 0/4] userfaultfd: selftest: Improve behavior with older kernels

[Thiago Jung Bauermann]

Hello,

This version of the series is unchanged from v2 except for the last patch
which is completely new, and is provided by Mike Rapoport.

Original series description:

> A tester ran the upstream selftest on a distro kernel and sounded the
> alarm when it reported failures for features which aren't included in
> that kernel.
> 
> This patch set improves the test behavior in that scenario.

Changes since v2:

- Added Mike Rapoport's Reviewed-by's and Acked-by's to patches 1-3. 
- Replaced patch 4/4 by the one provided by Mike Rapoport.

Changes since v1:

- Patch "userfaultfd: selftest: Skip test if userfaultfd() syscall
  not supported"
  - New patch, suggested by Mike Rapoport.

- Patch "userfaultfd: selftest: Skip test if a feature isn't supported"
  - Try running other tests even if one (or more) of them returns KSFT_SKIP.

- Patch "userfaultfd: selftest: Cope if shmem doesn't support zeropage"
  - Ignore lack of UFFDIO_ZEROPAGE in userfaultfd_events_test() and
    userfaultfd_stress().
  - Make userfaultfd_zeropage_test() return KSFT_SKIP if UFFDIO_ZEROPAGE
    isn't supported.

Mike Rapoport (1):
  userfaultfd: selftest: make supported range ioctl verification more
    robust

Thiago Jung Bauermann (3):
  userfaultfd: selftest: Fix checking of userfaultfd_open() result
  userfaultfd: selftest: Skip test if userfaultfd() syscall not
    supported
  userfaultfd: selftest: Skip test if a feature isn't supported

 tools/testing/selftests/vm/userfaultfd.c | 113 +++++++++++++++++++------------
 1 file changed, 69 insertions(+), 44 deletions(-)

[PATCH v3 1/4] userfaultfd: selftest: Fix checking of userfaultfd_open() result

[Thiago Jung Bauermann]

If the userfaultfd test is run on a kernel with CONFIG_USERFAULTFD=n, it
will report that the system call is not available yet go ahead and continue
anyway:

  # ./userfaultfd anon 30 1
  nr_pages: 480, nr_pages_per_cpu: 120
  userfaultfd syscall not available in this kernel
  bounces: 0, mode:, register failure

This is because userfaultfd_open() returns 0 on success and 1 on error but
all callers assume that it returns < 0 on error.

Since the convention of the test as a whole is the one used by
userfault_open(), fix its callers instead. Now the test behaves correctly:

  # ./userfaultfd anon 30 1
  nr_pages: 480, nr_pages_per_cpu: 120
  userfaultfd syscall not available in this kernel

Signed-off-by: Thiago Jung Bauermann <bauerman@linux.ibm.com>
Reviewed-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
---
 tools/testing/selftests/vm/userfaultfd.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/tools/testing/selftests/vm/userfaultfd.c b/tools/testing/selftests/vm/userfaultfd.c
index 7b8171e3128a..e4099afe7557 100644
--- a/tools/testing/selftests/vm/userfaultfd.c
+++ b/tools/testing/selftests/vm/userfaultfd.c
@@ -859,7 +859,7 @@ static int userfaultfd_zeropage_test(void)
 	if (uffd_test_ops->release_pages(area_dst))
 		return 1;
 
-	if (userfaultfd_open(0) < 0)
+	if (userfaultfd_open(0))
 		return 1;
 	uffdio_register.range.start = (unsigned long) area_dst;
 	uffdio_register.range.len = nr_pages * page_size;
@@ -902,7 +902,7 @@ static int userfaultfd_events_test(void)
 
 	features = UFFD_FEATURE_EVENT_FORK | UFFD_FEATURE_EVENT_REMAP |
 		UFFD_FEATURE_EVENT_REMOVE;
-	if (userfaultfd_open(features) < 0)
+	if (userfaultfd_open(features))
 		return 1;
 	fcntl(uffd, F_SETFL, uffd_flags | O_NONBLOCK);
 
@@ -961,7 +961,7 @@ static int userfaultfd_sig_test(void)
 		return 1;
 
 	features = UFFD_FEATURE_EVENT_FORK|UFFD_FEATURE_SIGBUS;
-	if (userfaultfd_open(features) < 0)
+	if (userfaultfd_open(features))
 		return 1;
 	fcntl(uffd, F_SETFL, uffd_flags | O_NONBLOCK);
 
@@ -1027,7 +1027,7 @@ static int userfaultfd_stress(void)
 	if (!area_dst)
 		return 1;
 
-	if (userfaultfd_open(0) < 0)
+	if (userfaultfd_open(0))
 		return 1;
 
 	count_verify = malloc(nr_pages * sizeof(unsigned long long));

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

[Thiago Jung Bauermann]

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@linux.vnet.ibm.com>
Signed-off-by: Thiago Jung Bauermann <bauerman@linux.ibm.com>
Acked-by: Mike Rapoport <rppt@linux.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);
 

[PATCH v3 3/4] userfaultfd: selftest: Skip test if a feature isn't supported

[Thiago Jung Bauermann]

If userfaultfd runs on a system that doesn't support some feature it is
trying to test, it currently ends with error code 1 which indicates
test failure:

  # ./userfaultfd anon 10 10
  nr_pages: 160, nr_pages_per_cpu: 80
  bounces: 9, mode: rnd poll, userfaults: 7 59
  bounces: 8, mode: poll, userfaults: 0 0
  bounces: 7, mode: rnd racing ver, userfaults: 45 2
  bounces: 6, mode: racing ver, userfaults: 3 1
  bounces: 5, mode: rnd ver, userfaults: 55 32
  bounces: 4, mode: ver, userfaults: 69 0
  bounces: 3, mode: rnd racing, userfaults: 1 1
  bounces: 2, mode: racing, userfaults: 65 0
  bounces: 1, mode: rnd, userfaults: 44 1
  bounces: 0, mode:, userfaults: 3 2
  testing UFFDIO_ZEROPAGE: done.
  testing signal delivery: UFFDIO_API
  # echo $?
  1

Make each test return KSFT_SKIP instead, which is more accurate since it is
not a real test failure and try to run the other tests which may still
work:

  # ./userfaultfd anon 10 10
  nr_pages: 160, nr_pages_per_cpu: 80
  bounces: 9, mode: rnd poll, userfaults: 65 27
  bounces: 8, mode: poll, userfaults: 0 0
  bounces: 7, mode: rnd racing ver, userfaults: 60 29
  bounces: 6, mode: racing ver, userfaults: 58 1
  bounces: 5, mode: rnd ver, userfaults: 69 3
  bounces: 4, mode: ver, userfaults: 35 27
  bounces: 3, mode: rnd racing, userfaults: 44 0
  bounces: 2, mode: racing, userfaults: 40 25
  bounces: 1, mode: rnd, userfaults: 2 1
  bounces: 0, mode:, userfaults: 0 1
  testing UFFDIO_ZEROPAGE: done.
  testing signal delivery: UFFDIO_API: Invalid argument
  testing events (fork, remap, remove): userfaults: 160
  # echo $?
  0

While at it, also improve the error message of the ioctl(UFFDIO_API) call.

Signed-off-by: Thiago Jung Bauermann <bauerman@linux.ibm.com>
Acked-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
---
 tools/testing/selftests/vm/userfaultfd.c | 42 +++++++++++++++++++++++---------
 1 file changed, 30 insertions(+), 12 deletions(-)

diff --git a/tools/testing/selftests/vm/userfaultfd.c b/tools/testing/selftests/vm/userfaultfd.c
index d728bd1cb33c..c84e44ddf314 100644
--- a/tools/testing/selftests/vm/userfaultfd.c
+++ b/tools/testing/selftests/vm/userfaultfd.c
@@ -647,8 +647,11 @@ static int userfaultfd_open(int features)
 	uffdio_api.api = UFFD_API;
 	uffdio_api.features = features;
 	if (ioctl(uffd, UFFDIO_API, &uffdio_api)) {
-		fprintf(stderr, "UFFDIO_API\n");
-		return 1;
+		int errnum = errno;
+
+		perror("UFFDIO_API");
+
+		return errnum == EINVAL ? KSFT_SKIP : 1;
 	}
 	if (uffdio_api.api != UFFD_API) {
 		fprintf(stderr, "UFFDIO_API error %Lu\n", uffdio_api.api);
@@ -854,6 +857,7 @@ static int userfaultfd_zeropage_test(void)
 {
 	struct uffdio_register uffdio_register;
 	unsigned long expected_ioctls;
+	int err;
 
 	printf("testing UFFDIO_ZEROPAGE: ");
 	fflush(stdout);
@@ -861,8 +865,10 @@ static int userfaultfd_zeropage_test(void)
 	if (uffd_test_ops->release_pages(area_dst))
 		return 1;
 
-	if (userfaultfd_open(0))
-		return 1;
+	err = userfaultfd_open(0);
+	if (err)
+		return err;
+
 	uffdio_register.range.start = (unsigned long) area_dst;
 	uffdio_register.range.len = nr_pages * page_size;
 	uffdio_register.mode = UFFDIO_REGISTER_MODE_MISSING;
@@ -904,8 +910,10 @@ static int userfaultfd_events_test(void)
 
 	features = UFFD_FEATURE_EVENT_FORK | UFFD_FEATURE_EVENT_REMAP |
 		UFFD_FEATURE_EVENT_REMOVE;
-	if (userfaultfd_open(features))
-		return 1;
+	err = userfaultfd_open(features);
+	if (err)
+		return err;
+
 	fcntl(uffd, F_SETFL, uffd_flags | O_NONBLOCK);
 
 	uffdio_register.range.start = (unsigned long) area_dst;
@@ -963,8 +971,9 @@ static int userfaultfd_sig_test(void)
 		return 1;
 
 	features = UFFD_FEATURE_EVENT_FORK|UFFD_FEATURE_SIGBUS;
-	if (userfaultfd_open(features))
-		return 1;
+	err = userfaultfd_open(features);
+	if (err)
+		return err;
 	fcntl(uffd, F_SETFL, uffd_flags | O_NONBLOCK);
 
 	uffdio_register.range.start = (unsigned long) area_dst;
@@ -1029,8 +1038,9 @@ static int userfaultfd_stress(void)
 	if (!area_dst)
 		return 1;
 
-	if (userfaultfd_open(0))
-		return 1;
+	err = userfaultfd_open(0);
+	if (err)
+		return err;
 
 	count_verify = malloc(nr_pages * sizeof(unsigned long long));
 	if (!count_verify) {
@@ -1201,8 +1211,16 @@ static int userfaultfd_stress(void)
 		return err;
 
 	close(uffd);
-	return userfaultfd_zeropage_test() || userfaultfd_sig_test()
-		|| userfaultfd_events_test();
+
+	err = userfaultfd_zeropage_test();
+	if (err && err != KSFT_SKIP)
+		return err;
+
+	err = userfaultfd_sig_test();
+	if (err && err != KSFT_SKIP)
+		return err;
+
+	return userfaultfd_events_test();
 }
 
 /*

[PATCH v3 4/4] userfaultfd: selftest: make supported range ioctl verification more robust

[Thiago Jung Bauermann]

From: Mike Rapoport <rppt@linux.vnet.ibm.com>

When userfaultfd tests runs on older kernel that does not support
UFFDIO_ZEROPAGE for shared memory it fails at the ioctl verification.

Split out the verification that supported ioctls are superset of the
expected ioctls and relax the checks for UFFDIO_ZEROPAGE for shared memory
areas.

Signed-off-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Signed-off-by: Thiago Jung Bauermann <bauerman@linux.ibm.com>
---
 tools/testing/selftests/vm/userfaultfd.c | 63 +++++++++++++++++---------------
 1 file changed, 34 insertions(+), 29 deletions(-)

diff --git a/tools/testing/selftests/vm/userfaultfd.c b/tools/testing/selftests/vm/userfaultfd.c
index c84e44ddf314..676cbedff3db 100644
--- a/tools/testing/selftests/vm/userfaultfd.c
+++ b/tools/testing/selftests/vm/userfaultfd.c
@@ -271,6 +271,32 @@ static int my_bcmp(char *str1, char *str2, size_t n)
 	return 0;
 }
 
+static int verify_ioctls(unsigned long supported_ioctls)
+{
+	unsigned long expected_ioctls = uffd_test_ops->expected_ioctls;
+
+	if ((supported_ioctls & expected_ioctls) == expected_ioctls)
+		return 0;
+
+	/*
+	 * For older kernels shared memory may not have UFFDIO_ZEROPAGE.
+	 * In this case we just mask it out from the
+	 * expected_ioctls. The userfaultfd_zeropage_test will then
+	 * verify that an attempt to use UFFDIO_ZEROPAGE returns
+	 * EINVAL
+	 */
+	if (test_type == TEST_SHMEM) {
+		expected_ioctls &= ~(1 << _UFFDIO_ZEROPAGE);
+		if ((supported_ioctls & expected_ioctls) == expected_ioctls) {
+			uffd_test_ops->expected_ioctls = expected_ioctls;
+			return 0;
+		}
+	}
+
+	fprintf(stderr, "unexpected missing ioctl\n");
+	return 1;
+}
+
 static void *locking_thread(void *arg)
 {
 	unsigned long cpu = (unsigned long) arg;
@@ -856,7 +882,6 @@ static int uffdio_zeropage(int ufd, unsigned long offset)
 static int userfaultfd_zeropage_test(void)
 {
 	struct uffdio_register uffdio_register;
-	unsigned long expected_ioctls;
 	int err;
 
 	printf("testing UFFDIO_ZEROPAGE: ");
@@ -875,12 +900,8 @@ static int userfaultfd_zeropage_test(void)
 	if (ioctl(uffd, UFFDIO_REGISTER, &uffdio_register))
 		fprintf(stderr, "register failure\n"), exit(1);
 
-	expected_ioctls = uffd_test_ops->expected_ioctls;
-	if ((uffdio_register.ioctls & expected_ioctls) !=
-	    expected_ioctls)
-		fprintf(stderr,
-			"unexpected missing ioctl for anon memory\n"),
-			exit(1);
+	if (verify_ioctls(uffdio_register.ioctls))
+		return 1;
 
 	if (uffdio_zeropage(uffd, 0)) {
 		if (my_bcmp(area_dst, zeropage, page_size))
@@ -895,7 +916,6 @@ static int userfaultfd_zeropage_test(void)
 static int userfaultfd_events_test(void)
 {
 	struct uffdio_register uffdio_register;
-	unsigned long expected_ioctls;
 	unsigned long userfaults;
 	pthread_t uffd_mon;
 	int err, features;
@@ -922,12 +942,8 @@ static int userfaultfd_events_test(void)
 	if (ioctl(uffd, UFFDIO_REGISTER, &uffdio_register))
 		fprintf(stderr, "register failure\n"), exit(1);
 
-	expected_ioctls = uffd_test_ops->expected_ioctls;
-	if ((uffdio_register.ioctls & expected_ioctls) !=
-	    expected_ioctls)
-		fprintf(stderr,
-			"unexpected missing ioctl for anon memory\n"),
-			exit(1);
+	if (verify_ioctls(uffdio_register.ioctls))
+		return 1;
 
 	if (pthread_create(&uffd_mon, &attr, uffd_poll_thread, NULL))
 		perror("uffd_poll_thread create"), exit(1);
@@ -957,7 +973,6 @@ static int userfaultfd_events_test(void)
 static int userfaultfd_sig_test(void)
 {
 	struct uffdio_register uffdio_register;
-	unsigned long expected_ioctls;
 	unsigned long userfaults;
 	pthread_t uffd_mon;
 	int err, features;
@@ -982,12 +997,8 @@ static int userfaultfd_sig_test(void)
 	if (ioctl(uffd, UFFDIO_REGISTER, &uffdio_register))
 		fprintf(stderr, "register failure\n"), exit(1);
 
-	expected_ioctls = uffd_test_ops->expected_ioctls;
-	if ((uffdio_register.ioctls & expected_ioctls) !=
-	    expected_ioctls)
-		fprintf(stderr,
-			"unexpected missing ioctl for anon memory\n"),
-			exit(1);
+	if (verify_ioctls(uffdio_register.ioctls))
+		return 1;
 
 	if (faulting_process(1))
 		fprintf(stderr, "faulting process failed\n"), exit(1);
@@ -1088,8 +1099,6 @@ static int userfaultfd_stress(void)
 
 	err = 0;
 	while (bounces--) {
-		unsigned long expected_ioctls;
-
 		printf("bounces: %d, mode:", bounces);
 		if (bounces & BOUNCE_RANDOM)
 			printf(" rnd");
@@ -1115,13 +1124,9 @@ static int userfaultfd_stress(void)
 			fprintf(stderr, "register failure\n");
 			return 1;
 		}
-		expected_ioctls = uffd_test_ops->expected_ioctls;
-		if ((uffdio_register.ioctls & expected_ioctls) !=
-		    expected_ioctls) {
-			fprintf(stderr,
-				"unexpected missing ioctl for anon memory\n");
+
+		if (verify_ioctls(uffdio_register.ioctls))
 			return 1;
-		}
 
 		if (area_dst_alias) {
 			uffdio_register.range.start = (unsigned long)