diff mbox series

[v2,7/9] userfaultfd/selftests: reinitialize test context in each test

Message ID 20210413051721.2896915-8-axelrasmussen@google.com
State New
Headers show
Series [v2,1/9] userfaultfd/hugetlbfs: avoid including userfaultfd_k.h in hugetlb.h | expand

Commit Message

Axel Rasmussen April 13, 2021, 5:17 a.m. UTC 
Currently, the context (fds, mmap-ed areas, etc.) are global. Each test
mutates this state in some way, in some cases really "clobbering it"
(e.g., the events test mremap-ing area_dst over the top of area_src, or
the minor faults tests overwriting the count_verify values in the test
areas). We run the tests in a particular order, each test is careful to
make the right assumptions about its starting state, etc.

But, this is fragile. It's better for a test's success or failure to not
depend on what some other prior test case did to the global state.

To that end, clear and reinitialize the test context at the start of
each test case, so whatever prior test cases did doesn't affect future
tests.

This is particularly relevant to this series because the events test's
mremap of area_dst screws up assumptions the minor fault test was
relying on. This wasn't a problem for hugetlb, as we don't mremap in
that case.

Signed-off-by: Axel Rasmussen <axelrasmussen@google.com>
---
 tools/testing/selftests/vm/userfaultfd.c | 221 +++++++++++++----------
 1 file changed, 127 insertions(+), 94 deletions(-)

Comments

Axel Rasmussen April 15, 2021, 6:03 p.m. UTC | #1 
On Tue, Apr 13, 2021 at 1:15 PM Peter Xu <peterx@redhat.com> wrote:
>

> On Mon, Apr 12, 2021 at 10:17:19PM -0700, Axel Rasmussen wrote:

> > Currently, the context (fds, mmap-ed areas, etc.) are global. Each test

> > mutates this state in some way, in some cases really "clobbering it"

> > (e.g., the events test mremap-ing area_dst over the top of area_src, or

> > the minor faults tests overwriting the count_verify values in the test

> > areas). We run the tests in a particular order, each test is careful to

> > make the right assumptions about its starting state, etc.

> >

> > But, this is fragile. It's better for a test's success or failure to not

> > depend on what some other prior test case did to the global state.

> >

> > To that end, clear and reinitialize the test context at the start of

> > each test case, so whatever prior test cases did doesn't affect future

> > tests.

> >

> > This is particularly relevant to this series because the events test's

> > mremap of area_dst screws up assumptions the minor fault test was

> > relying on. This wasn't a problem for hugetlb, as we don't mremap in

> > that case.

> >

> > Signed-off-by: Axel Rasmussen <axelrasmussen@google.com>

> > ---

> >  tools/testing/selftests/vm/userfaultfd.c | 221 +++++++++++++----------

> >  1 file changed, 127 insertions(+), 94 deletions(-)

> >

> > diff --git a/tools/testing/selftests/vm/userfaultfd.c b/tools/testing/selftests/vm/userfaultfd.c

> > index 1f65c4ab7994..0ff01f437a39 100644

> > --- a/tools/testing/selftests/vm/userfaultfd.c

> > +++ b/tools/testing/selftests/vm/userfaultfd.c

> > @@ -89,7 +89,8 @@ static int shm_fd;

> >  static int huge_fd;

> >  static char *huge_fd_off0;

> >  static unsigned long long *count_verify;

> > -static int uffd, uffd_flags, finished, *pipefd;

> > +static int uffd = -1;

> > +static int uffd_flags, finished, *pipefd;

> >  static char *area_src, *area_src_alias, *area_dst, *area_dst_alias;

> >  static char *zeropage;

> >  pthread_attr_t attr;

> > @@ -342,6 +343,121 @@ static struct uffd_test_ops hugetlb_uffd_test_ops = {

> >

> >  static struct uffd_test_ops *uffd_test_ops;

> >

> > +static int userfaultfd_open(uint64_t *features)

> > +{

> > +     struct uffdio_api uffdio_api;

> > +

> > +     uffd = syscall(__NR_userfaultfd, O_CLOEXEC | O_NONBLOCK);

>

> Keep UFFD_USER_MODE_ONLY?

>

> [...]

>

> > @@ -961,10 +1045,9 @@ static int userfaultfd_zeropage_test(void)

> >       printf("testing UFFDIO_ZEROPAGE: ");

> >       fflush(stdout);

> >

> > -     uffd_test_ops->release_pages(area_dst);

> > -

> > -     if (userfaultfd_open(0))

> > +     if (uffd_test_ctx_clear() || uffd_test_ctx_init(0))

> >               return 1;

>

> Would it look even nicer to init() at the entry of each test, and clear() after

> finish one test?


I slightly prefer clearing at the beginning, as it means we don't need
to depend on the previous test being correct for this test to
function. And, we don't need more complex error handling in the test
cases to make sure we don't mess things up for the next test.

But, two things we can do to clean this up as-is:

The initialization function can just call clear itself, so tests don't
need to worry about it.

And, with err(), we don't need these functions to return an int any more.

I'll send a version like that, we can see how it looks.

>

> > +

> >       uffdio_register.range.start = (unsigned long) area_dst;

> >       uffdio_register.range.len = nr_pages * page_size;

> >       uffdio_register.mode = UFFDIO_REGISTER_MODE_MISSING;

>

> The rest looks good to me.  Thanks,

>

> --

> Peter Xu

>
diff mbox series

Patch

diff --git a/tools/testing/selftests/vm/userfaultfd.c b/tools/testing/selftests/vm/userfaultfd.c
index 1f65c4ab7994..0ff01f437a39 100644
--- a/tools/testing/selftests/vm/userfaultfd.c
+++ b/tools/testing/selftests/vm/userfaultfd.c
@@ -89,7 +89,8 @@  static int shm_fd;
 static int huge_fd;
 static char *huge_fd_off0;
 static unsigned long long *count_verify;
-static int uffd, uffd_flags, finished, *pipefd;
+static int uffd = -1;
+static int uffd_flags, finished, *pipefd;
 static char *area_src, *area_src_alias, *area_dst, *area_dst_alias;
 static char *zeropage;
 pthread_attr_t attr;
@@ -342,6 +343,121 @@  static struct uffd_test_ops hugetlb_uffd_test_ops = {
 
 static struct uffd_test_ops *uffd_test_ops;
 
+static int userfaultfd_open(uint64_t *features)
+{
+	struct uffdio_api uffdio_api;
+
+	uffd = syscall(__NR_userfaultfd, O_CLOEXEC | O_NONBLOCK);
+	if (uffd < 0)
+		err("userfaultfd syscall not available in this kernel");
+	uffd_flags = fcntl(uffd, F_GETFD, NULL);
+
+	uffdio_api.api = UFFD_API;
+	uffdio_api.features = *features;
+	if (ioctl(uffd, UFFDIO_API, &uffdio_api))
+		err("UFFDIO_API failed.\nPlease make sure to "
+		    "run with either root or ptrace capability.");
+	if (uffdio_api.api != UFFD_API)
+		err("UFFDIO_API error: %" PRIu64, (uint64_t)uffdio_api.api);
+
+	*features = uffdio_api.features;
+	return 0;
+}
+
+static int uffd_test_ctx_init_ext(uint64_t *features)
+{
+	unsigned long nr, cpu;
+
+	uffd_test_ops->allocate_area((void **)&area_src);
+	if (!area_src)
+		return 1;
+	uffd_test_ops->allocate_area((void **)&area_dst);
+	if (!area_dst)
+		return 1;
+
+	uffd_test_ops->release_pages(area_src);
+	uffd_test_ops->release_pages(area_dst);
+
+	if (userfaultfd_open(features))
+		return 1;
+
+	count_verify = malloc(nr_pages * sizeof(unsigned long long));
+	if (!count_verify)
+		err("count_verify");
+
+	for (nr = 0; nr < nr_pages; nr++) {
+		*area_mutex(area_src, nr) =
+			(pthread_mutex_t)PTHREAD_MUTEX_INITIALIZER;
+		count_verify[nr] = *area_count(area_src, nr) = 1;
+		/*
+		 * In the transition between 255 to 256, powerpc will
+		 * read out of order in my_bcmp and see both bytes as
+		 * zero, so leave a placeholder below always non-zero
+		 * after the count, to avoid my_bcmp to trigger false
+		 * positives.
+		 */
+		*(area_count(area_src, nr) + 1) = 1;
+	}
+
+	pipefd = malloc(sizeof(int) * nr_cpus * 2);
+	if (!pipefd)
+		err("pipefd");
+	for (cpu = 0; cpu < nr_cpus; cpu++)
+		if (pipe2(&pipefd[cpu * 2], O_CLOEXEC | O_NONBLOCK))
+			err("pipe");
+
+	return 0;
+}
+
+static inline int uffd_test_ctx_init(uint64_t features)
+{
+	return uffd_test_ctx_init_ext(&features);
+}
+
+static inline int munmap_area(void **area)
+{
+	if (*area)
+		if (munmap(*area, nr_pages * page_size))
+			err("munmap");
+
+	*area = NULL;
+	return 0;
+}
+
+static int uffd_test_ctx_clear(void)
+{
+	int ret = 0;
+	size_t i;
+
+	if (pipefd) {
+		for (i = 0; i < nr_cpus * 2; ++i) {
+			if (close(pipefd[i]))
+				err("close pipefd");
+		}
+		free(pipefd);
+		pipefd = NULL;
+	}
+
+	if (count_verify) {
+		free(count_verify);
+		count_verify = NULL;
+	}
+
+	if (uffd != -1) {
+		if (close(uffd))
+			err("close uffd");
+		uffd = -1;
+	}
+
+	huge_fd_off0 = NULL;
+	ret |= munmap_area((void **)&area_src);
+	ret |= munmap_area((void **)&area_src_alias);
+	ret |= munmap_area((void **)&area_dst);
+	ret |= munmap_area((void **)&area_dst_alias);
+
+	return ret;
+}
+
 static int my_bcmp(char *str1, char *str2, size_t n)
 {
 	unsigned long i;
@@ -726,40 +842,6 @@  static int stress(struct uffd_stats *uffd_stats)
 	return 0;
 }
 
-static int userfaultfd_open_ext(uint64_t *features)
-{
-	struct uffdio_api uffdio_api;
-
-	uffd = syscall(__NR_userfaultfd, O_CLOEXEC | O_NONBLOCK | UFFD_USER_MODE_ONLY);
-	if (uffd < 0) {
-		fprintf(stderr,
-			"userfaultfd syscall not available in this kernel\n");
-		return 1;
-	}
-	uffd_flags = fcntl(uffd, F_GETFD, NULL);
-
-	uffdio_api.api = UFFD_API;
-	uffdio_api.features = *features;
-	if (ioctl(uffd, UFFDIO_API, &uffdio_api)) {
-		fprintf(stderr, "UFFDIO_API failed.\nPlease make sure to "
-			"run with either root or ptrace capability.\n");
-		return 1;
-	}
-	if (uffdio_api.api != UFFD_API) {
-		fprintf(stderr, "UFFDIO_API error: %" PRIu64 "\n",
-			(uint64_t)uffdio_api.api);
-		return 1;
-	}
-
-	*features = uffdio_api.features;
-	return 0;
-}
-
-static int userfaultfd_open(uint64_t features)
-{
-	return userfaultfd_open_ext(&features);
-}
-
 sigjmp_buf jbuf, *sigbuf;
 
 static void sighndl(int sig, siginfo_t *siginfo, void *ptr)
@@ -868,6 +950,8 @@  static int faulting_process(int signal_test)
 			  MREMAP_MAYMOVE | MREMAP_FIXED, area_src);
 	if (area_dst == MAP_FAILED)
 		err("mremap");
+	/* Reset area_src since we just clobbered it */
+	area_src = NULL;
 
 	for (; nr < nr_pages; nr++) {
 		count = *area_count(area_dst, nr);
@@ -961,10 +1045,9 @@  static int userfaultfd_zeropage_test(void)
 	printf("testing UFFDIO_ZEROPAGE: ");
 	fflush(stdout);
 
-	uffd_test_ops->release_pages(area_dst);
-
-	if (userfaultfd_open(0))
+	if (uffd_test_ctx_clear() || uffd_test_ctx_init(0))
 		return 1;
+
 	uffdio_register.range.start = (unsigned long) area_dst;
 	uffdio_register.range.len = nr_pages * page_size;
 	uffdio_register.mode = UFFDIO_REGISTER_MODE_MISSING;
@@ -981,7 +1064,6 @@  static int userfaultfd_zeropage_test(void)
 		if (my_bcmp(area_dst, zeropage, page_size))
 			err("zeropage is not zero");
 
-	close(uffd);
 	printf("done.\n");
 	return 0;
 }
@@ -999,12 +1081,11 @@  static int userfaultfd_events_test(void)
 	printf("testing events (fork, remap, remove): ");
 	fflush(stdout);
 
-	uffd_test_ops->release_pages(area_dst);
-
 	features = UFFD_FEATURE_EVENT_FORK | UFFD_FEATURE_EVENT_REMAP |
 		UFFD_FEATURE_EVENT_REMOVE;
-	if (userfaultfd_open(features))
+	if (uffd_test_ctx_clear() || uffd_test_ctx_init(features))
 		return 1;
+
 	fcntl(uffd, F_SETFL, uffd_flags | O_NONBLOCK);
 
 	uffdio_register.range.start = (unsigned long) area_dst;
@@ -1037,8 +1118,6 @@  static int userfaultfd_events_test(void)
 	if (pthread_join(uffd_mon, NULL))
 		return 1;
 
-	close(uffd);
-
 	uffd_stats_report(&stats, 1);
 
 	return stats.missing_faults != nr_pages;
@@ -1058,11 +1137,10 @@  static int userfaultfd_sig_test(void)
 	printf("testing signal delivery: ");
 	fflush(stdout);
 
-	uffd_test_ops->release_pages(area_dst);
-
 	features = UFFD_FEATURE_EVENT_FORK|UFFD_FEATURE_SIGBUS;
-	if (userfaultfd_open(features))
+	if (uffd_test_ctx_clear() || uffd_test_ctx_init(features))
 		return 1;
+
 	fcntl(uffd, F_SETFL, uffd_flags | O_NONBLOCK);
 
 	uffdio_register.range.start = (unsigned long) area_dst;
@@ -1126,9 +1204,7 @@  static int userfaultfd_minor_test(void)
 	printf("testing minor faults: ");
 	fflush(stdout);
 
-	uffd_test_ops->release_pages(area_dst);
-
-	if (userfaultfd_open_ext(&features))
+	if (uffd_test_ctx_clear() || uffd_test_ctx_init_ext(&features))
 		return 1;
 	/* If kernel reports the feature isn't supported, skip the test. */
 	if (!(features & UFFD_FEATURE_MINOR_HUGETLBFS)) {
@@ -1183,8 +1259,6 @@  static int userfaultfd_minor_test(void)
 	if (pthread_join(uffd_mon, NULL))
 		return 1;
 
-	close(uffd);
-
 	uffd_stats_report(&stats, 1);
 
 	return stats.missing_faults != 0 || stats.minor_faults != nr_pages;
@@ -1196,50 +1270,10 @@  static int userfaultfd_stress(void)
 	char *tmp_area;
 	unsigned long nr;
 	struct uffdio_register uffdio_register;
-	unsigned long cpu;
 	struct uffd_stats uffd_stats[nr_cpus];
 
-	uffd_test_ops->allocate_area((void **)&area_src);
-	if (!area_src)
-		return 1;
-	uffd_test_ops->allocate_area((void **)&area_dst);
-	if (!area_dst)
-		return 1;
-
-	if (userfaultfd_open(0))
-		return 1;
-
-	count_verify = malloc(nr_pages * sizeof(unsigned long long));
-	if (!count_verify) {
-		perror("count_verify");
-		return 1;
-	}
-
-	for (nr = 0; nr < nr_pages; nr++) {
-		*area_mutex(area_src, nr) = (pthread_mutex_t)
-			PTHREAD_MUTEX_INITIALIZER;
-		count_verify[nr] = *area_count(area_src, nr) = 1;
-		/*
-		 * In the transition between 255 to 256, powerpc will
-		 * read out of order in my_bcmp and see both bytes as
-		 * zero, so leave a placeholder below always non-zero
-		 * after the count, to avoid my_bcmp to trigger false
-		 * positives.
-		 */
-		*(area_count(area_src, nr) + 1) = 1;
-	}
-
-	pipefd = malloc(sizeof(int) * nr_cpus * 2);
-	if (!pipefd) {
-		perror("pipefd");
+	if (uffd_test_ctx_init(0))
 		return 1;
-	}
-	for (cpu = 0; cpu < nr_cpus; cpu++) {
-		if (pipe2(&pipefd[cpu*2], O_CLOEXEC | O_NONBLOCK)) {
-			perror("pipe");
-			return 1;
-		}
-	}
 
 	if (posix_memalign(&area, page_size, page_size))
 		err("out of memory");
@@ -1360,7 +1394,6 @@  static int userfaultfd_stress(void)
 		uffd_stats_report(uffd_stats, nr_cpus);
 	}
 
-	close(uffd);
 	return userfaultfd_zeropage_test() || userfaultfd_sig_test()
 		|| userfaultfd_events_test() || userfaultfd_minor_test();
 }