[PATCH 0/5] userfaultfd/selftests: A few cleanups

[PATCH 0/5] userfaultfd/selftests: A few cleanups

[Peter Xu]

Based on v5.12-rc2-mmots-2021-03-08-21-54.

I wanted to cleanup userfaultfd.c fault handling for a long time. If it's not
cleaned, when the new code grows the file it'll also grow the size that needs
to be cleaned...  This is my attempt to cleanup the userfaultfd selftest on
fault handling, to use an err() macro instead of either fprintf() or perror()
then another exit() call.

The huge cleanup is done in the last patch.  The first 4 patches are some other
standalone cleanups for the same file, so I put them together.

Please review, thanks.

Peter Xu (5):
  userfaultfd/selftests: Use user mode only
  userfaultfd/selftests: Remove the time() check on delayed uffd
  userfaultfd/selftests: Dropping VERIFY check in locking_thread
  userfaultfd/selftests: Only dump counts if mode enabled
  userfaultfd/selftests: Unify error handling

 tools/testing/selftests/vm/userfaultfd.c | 742 +++++++----------------
 1 file changed, 235 insertions(+), 507 deletions(-)

-- 
2.26.2

[PATCH 1/5] userfaultfd/selftests: Use user mode only

[Peter Xu]

Userfaultfd selftest does not need to handle kernel initiated fault.  Set user
mode so it can be run even if unprivileged_userfaultfd=0 (which is the default).

Signed-off-by: Peter Xu <peterx@redhat.com>
---
 tools/testing/selftests/vm/userfaultfd.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/testing/selftests/vm/userfaultfd.c b/tools/testing/selftests/vm/userfaultfd.c
index f31e9a4edc55..6dab8ef034a0 100644
--- a/tools/testing/selftests/vm/userfaultfd.c
+++ b/tools/testing/selftests/vm/userfaultfd.c
@@ -381,7 +381,7 @@ static int userfaultfd_open(uint64_t *features)
 {
 	struct uffdio_api uffdio_api;
 
-	uffd = syscall(__NR_userfaultfd, O_CLOEXEC | O_NONBLOCK);
+	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");
-- 
2.26.2

[PATCH 2/5] userfaultfd/selftests: Remove the time() check on delayed uffd

[Peter Xu]

There seems to have no guarantee that time() will return the same for the two
calls even if there's no delay, e.g. when a fault is accidentally crossing the
changing of a second.  Meanwhile, this message is also not helping that much
since delay could happen with a lot of reasons, e.g., schedule latency of
resolving thread.  It may not mean an issue with uffd.

Neither do I saw this error triggered either in the past runs.  Even if it
triggers, it'll be drown in all the rest of test logs.  Remove it.

Signed-off-by: Peter Xu <peterx@redhat.com>
---
 tools/testing/selftests/vm/userfaultfd.c | 8 --------
 1 file changed, 8 deletions(-)

diff --git a/tools/testing/selftests/vm/userfaultfd.c b/tools/testing/selftests/vm/userfaultfd.c
index 6dab8ef034a0..5cde062f07bc 100644
--- a/tools/testing/selftests/vm/userfaultfd.c
+++ b/tools/testing/selftests/vm/userfaultfd.c
@@ -568,7 +568,6 @@ static void *locking_thread(void *arg)
 	unsigned long long count;
 	char randstate[64];
 	unsigned int seed;
-	time_t start;
 
 	if (bounces & BOUNCE_RANDOM) {
 		seed = (unsigned int) time(NULL) - bounces;
@@ -605,7 +604,6 @@ static void *locking_thread(void *arg)
 			page_nr += 1;
 		page_nr %= nr_pages;
 
-		start = time(NULL);
 		if (bounces & BOUNCE_VERIFY) {
 			count = *area_count(area_dst, page_nr);
 			if (!count) {
@@ -668,12 +666,6 @@ static void *locking_thread(void *arg)
 		count++;
 		*area_count(area_dst, page_nr) = count_verify[page_nr] = count;
 		pthread_mutex_unlock(area_mutex(area_dst, page_nr));
-
-		if (time(NULL) - start > 1)
-			fprintf(stderr,
-				"userfault too slow %ld "
-				"possible false positive with overcommit\n",
-				time(NULL) - start);
 	}
 
 	return NULL;
-- 
2.26.2

[PATCH 3/5] userfaultfd/selftests: Dropping VERIFY check in locking_thread

[Peter Xu]

It tries to check against all zeros and looped for quite a few times.  However
after that we'll verify the same page with count_verify, while count_verify can
never be zero.  So it means if it's a zero page we'll detect it anyways with
below code.

There's yet another place we conditionally check the fault flag - just do it
unconditionally.

Signed-off-by: Peter Xu <peterx@redhat.com>
---
 tools/testing/selftests/vm/userfaultfd.c | 55 +-----------------------
 1 file changed, 1 insertion(+), 54 deletions(-)

diff --git a/tools/testing/selftests/vm/userfaultfd.c b/tools/testing/selftests/vm/userfaultfd.c
index 5cde062f07bc..cf0cd4cb327d 100644
--- a/tools/testing/selftests/vm/userfaultfd.c
+++ b/tools/testing/selftests/vm/userfaultfd.c
@@ -603,58 +603,6 @@ static void *locking_thread(void *arg)
 		} else
 			page_nr += 1;
 		page_nr %= nr_pages;
-
-		if (bounces & BOUNCE_VERIFY) {
-			count = *area_count(area_dst, page_nr);
-			if (!count) {
-				fprintf(stderr,
-					"page_nr %lu wrong count %Lu %Lu\n",
-					page_nr, count,
-					count_verify[page_nr]);
-				exit(1);
-			}
-
-
-			/*
-			 * We can't use bcmp (or memcmp) because that
-			 * returns 0 erroneously if the memory is
-			 * changing under it (even if the end of the
-			 * page is never changing and always
-			 * different).
-			 */
-#if 1
-			if (!my_bcmp(area_dst + page_nr * page_size, zeropage,
-				     page_size)) {
-				fprintf(stderr,
-					"my_bcmp page_nr %lu wrong count %Lu %Lu\n",
-					page_nr, count, count_verify[page_nr]);
-				exit(1);
-			}
-#else
-			unsigned long loops;
-
-			loops = 0;
-			/* uncomment the below line to test with mutex */
-			/* pthread_mutex_lock(area_mutex(area_dst, page_nr)); */
-			while (!bcmp(area_dst + page_nr * page_size, zeropage,
-				     page_size)) {
-				loops += 1;
-				if (loops > 10)
-					break;
-			}
-			/* uncomment below line to test with mutex */
-			/* pthread_mutex_unlock(area_mutex(area_dst, page_nr)); */
-			if (loops) {
-				fprintf(stderr,
-					"page_nr %lu all zero thread %lu %p %lu\n",
-					page_nr, cpu, area_dst + page_nr * page_size,
-					loops);
-				if (loops > 10)
-					exit(1);
-			}
-#endif
-		}
-
 		pthread_mutex_lock(area_mutex(area_dst, page_nr));
 		count = *area_count(area_dst, page_nr);
 		if (count != count_verify[page_nr]) {
@@ -786,8 +734,7 @@ static void uffd_handle_page_fault(struct uffd_msg *msg,
 		stats->minor_faults++;
 	} else {
 		/* Missing page faults */
-		if (bounces & BOUNCE_VERIFY &&
-		    msg->arg.pagefault.flags & UFFD_PAGEFAULT_FLAG_WRITE) {
+		if (msg->arg.pagefault.flags & UFFD_PAGEFAULT_FLAG_WRITE) {
 			fprintf(stderr, "unexpected write fault\n");
 			exit(1);
 		}
-- 
2.26.2

[PATCH 4/5] userfaultfd/selftests: Only dump counts if mode enabled

[Peter Xu]

WP and MINOR modes are conditionally enabled on specific memory types.  This
patch avoids dumping tons of zeros for those cases when the modes are not
supported at all.

Signed-off-by: Peter Xu <peterx@redhat.com>
---
 tools/testing/selftests/vm/userfaultfd.c | 30 ++++++++++++++++--------
 1 file changed, 20 insertions(+), 10 deletions(-)

diff --git a/tools/testing/selftests/vm/userfaultfd.c b/tools/testing/selftests/vm/userfaultfd.c
index cf0cd4cb327d..5f89d258024a 100644
--- a/tools/testing/selftests/vm/userfaultfd.c
+++ b/tools/testing/selftests/vm/userfaultfd.c
@@ -173,16 +173,26 @@ static void uffd_stats_report(struct uffd_stats *stats, int n_cpus)
 		minor_total += stats[i].minor_faults;
 	}
 
-	printf("userfaults: %llu missing (", miss_total);
-	for (i = 0; i < n_cpus; i++)
-		printf("%lu+", stats[i].missing_faults);
-	printf("\b), %llu wp (", wp_total);
-	for (i = 0; i < n_cpus; i++)
-		printf("%lu+", stats[i].wp_faults);
-	printf("\b), %llu minor (", minor_total);
-	for (i = 0; i < n_cpus; i++)
-		printf("%lu+", stats[i].minor_faults);
-	printf("\b)\n");
+	printf("userfaults: ");
+	if (miss_total) {
+		printf("%llu missing (", miss_total);
+		for (i = 0; i < n_cpus; i++)
+			printf("%lu+", stats[i].missing_faults);
+		printf("\b) ");
+	}
+	if (wp_total) {
+		printf("%llu wp (", wp_total);
+		for (i = 0; i < n_cpus; i++)
+			printf("%lu+", stats[i].wp_faults);
+		printf("\b) ");
+	}
+	if (minor_total) {
+		printf("%llu minor (", minor_total);
+		for (i = 0; i < n_cpus; i++)
+			printf("%lu+", stats[i].minor_faults);
+		printf("\b)");
+	}
+	printf("\n");
 }
 
 static int anon_release_pages(char *rel_area)
-- 
2.26.2

[PATCH 5/5] userfaultfd/selftests: Unify error handling

[Peter Xu]

Introduce err()/_err() and replace all the different ways to fail the program,
mostly "fprintf" and "perror" with tons of exit() calls. Always stop the test
program at any failure.

Signed-off-by: Peter Xu <peterx@redhat.com>
---
 tools/testing/selftests/vm/userfaultfd.c | 649 ++++++++---------------
 1 file changed, 214 insertions(+), 435 deletions(-)

diff --git a/tools/testing/selftests/vm/userfaultfd.c b/tools/testing/selftests/vm/userfaultfd.c
index 5f89d258024a..f6c86b036d0f 100644
--- a/tools/testing/selftests/vm/userfaultfd.c
+++ b/tools/testing/selftests/vm/userfaultfd.c
@@ -142,11 +142,18 @@ static void usage(void)
 	exit(1);
 }
 
-#define uffd_error(code, fmt, ...)                                             \
-	do {                                                                   \
-		fprintf(stderr, fmt, ##__VA_ARGS__);                           \
-		fprintf(stderr, ": %" PRId64 "\n", (int64_t)(code));           \
-		exit(1);                                                       \
+#define _err(fmt, ...)						\
+	do {							\
+		int ret = errno;				\
+		fprintf(stderr, "ERROR: " fmt, ##__VA_ARGS__);	\
+		fprintf(stderr, " (errno=%d, line=%d)\n",	\
+			ret, __LINE__);				\
+	} while (0)
+
+#define err(fmt, ...)				\
+	do {					\
+		_err(fmt, ##__VA_ARGS__);	\
+		exit(1);			\
 	} while (0)
 
 static void uffd_stats_reset(struct uffd_stats *uffd_stats,
@@ -195,44 +202,28 @@ static void uffd_stats_report(struct uffd_stats *stats, int n_cpus)
 	printf("\n");
 }
 
-static int anon_release_pages(char *rel_area)
+static void anon_release_pages(char *rel_area)
 {
-	int ret = 0;
-
-	if (madvise(rel_area, nr_pages * page_size, MADV_DONTNEED)) {
-		perror("madvise");
-		ret = 1;
-	}
-
-	return ret;
+	if (madvise(rel_area, nr_pages * page_size, MADV_DONTNEED))
+		err("madvise(MADV_DONTNEED) failed");
 }
 
 static void anon_allocate_area(void **alloc_area)
 {
-	if (posix_memalign(alloc_area, page_size, nr_pages * page_size)) {
-		fprintf(stderr, "out of memory\n");
-		*alloc_area = NULL;
-	}
+	if (posix_memalign(alloc_area, page_size, nr_pages * page_size))
+		err("posix_memalign() failed");
 }
 
 static void noop_alias_mapping(__u64 *start, size_t len, unsigned long offset)
 {
 }
 
-/* HugeTLB memory */
-static int hugetlb_release_pages(char *rel_area)
+static void hugetlb_release_pages(char *rel_area)
 {
-	int ret = 0;
-
 	if (fallocate(huge_fd, FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE,
-				rel_area == huge_fd_off0 ? 0 :
-				nr_pages * page_size,
-				nr_pages * page_size)) {
-		perror("fallocate");
-		ret = 1;
-	}
-
-	return ret;
+		      rel_area == huge_fd_off0 ? 0 : nr_pages * page_size,
+		      nr_pages * page_size))
+		err("fallocate() failed");
 }
 
 static void hugetlb_allocate_area(void **alloc_area)
@@ -245,20 +236,16 @@ static void hugetlb_allocate_area(void **alloc_area)
 			   MAP_HUGETLB,
 			   huge_fd, *alloc_area == area_src ? 0 :
 			   nr_pages * page_size);
-	if (*alloc_area == MAP_FAILED) {
-		perror("mmap of hugetlbfs file failed");
-		goto fail;
-	}
+	if (*alloc_area == MAP_FAILED)
+		err("mmap of hugetlbfs file failed");
 
 	if (map_shared) {
 		area_alias = mmap(NULL, nr_pages * page_size, PROT_READ | PROT_WRITE,
 				  MAP_SHARED | MAP_HUGETLB,
 				  huge_fd, *alloc_area == area_src ? 0 :
 				  nr_pages * page_size);
-		if (area_alias == MAP_FAILED) {
-			perror("mmap of hugetlb file alias failed");
-			goto fail_munmap;
-		}
+		if (area_alias == MAP_FAILED)
+			err("mmap of hugetlb file alias failed");
 	}
 
 	if (*alloc_area == area_src) {
@@ -267,18 +254,9 @@ static void hugetlb_allocate_area(void **alloc_area)
 	} else {
 		alloc_area_alias = &area_dst_alias;
 	}
+
 	if (area_alias)
 		*alloc_area_alias = area_alias;
-
-	return;
-
-fail_munmap:
-	if (munmap(*alloc_area, nr_pages * page_size) < 0) {
-		perror("hugetlb munmap");
-		exit(1);
-	}
-fail:
-	*alloc_area = NULL;
 }
 
 static void hugetlb_alias_mapping(__u64 *start, size_t len, unsigned long offset)
@@ -294,17 +272,10 @@ static void hugetlb_alias_mapping(__u64 *start, size_t len, unsigned long offset
 	*start = (unsigned long) area_dst_alias + offset;
 }
 
-/* Shared memory */
-static int shmem_release_pages(char *rel_area)
+static void shmem_release_pages(char *rel_area)
 {
-	int ret = 0;
-
-	if (madvise(rel_area, nr_pages * page_size, MADV_REMOVE)) {
-		perror("madvise");
-		ret = 1;
-	}
-
-	return ret;
+	if (madvise(rel_area, nr_pages * page_size, MADV_REMOVE))
+		err("madvise(MADV_REMOVE) failed");
 }
 
 static void shmem_allocate_area(void **alloc_area)
@@ -315,32 +286,18 @@ static void shmem_allocate_area(void **alloc_area)
 
 	*alloc_area = mmap(NULL, nr_pages * page_size, PROT_READ | PROT_WRITE,
 			   MAP_SHARED, shm_fd, offset);
-	if (*alloc_area == MAP_FAILED) {
-		perror("mmap of memfd failed");
-		goto fail;
-	}
+	if (*alloc_area == MAP_FAILED)
+		err("mmap of memfd failed");
 
 	area_alias = mmap(NULL, nr_pages * page_size, PROT_READ | PROT_WRITE,
 			  MAP_SHARED, shm_fd, offset);
-	if (area_alias == MAP_FAILED) {
-		perror("mmap of memfd alias failed");
-		goto fail_munmap;
-	}
+	if (area_alias == MAP_FAILED)
+		err("mmap of memfd alias failed");
 
 	if (is_src)
 		area_src_alias = area_alias;
 	else
 		area_dst_alias = area_alias;
-
-	return;
-
-fail_munmap:
-	if (munmap(*alloc_area, nr_pages * page_size) < 0) {
-		perror("munmap of memfd failed\n");
-		exit(1);
-	}
-fail:
-	*alloc_area = NULL;
 }
 
 static void shmem_alias_mapping(__u64 *start, size_t len, unsigned long offset)
@@ -351,7 +308,7 @@ static void shmem_alias_mapping(__u64 *start, size_t len, unsigned long offset)
 struct uffd_test_ops {
 	unsigned long expected_ioctls;
 	void (*allocate_area)(void **alloc_area);
-	int (*release_pages)(char *rel_area);
+	void (*release_pages)(char *rel_area);
 	void (*alias_mapping)(__u64 *start, size_t len, unsigned long offset);
 };
 
@@ -392,25 +349,17 @@ static int userfaultfd_open(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;
-	}
+	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)) {
-		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;
-	}
+	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;
@@ -427,20 +376,15 @@ static int uffd_test_ctx_init_ext(uint64_t *features)
 	if (!area_dst)
 		return 1;
 
-	if (uffd_test_ops->release_pages(area_src))
-		return 1;
-
-	if (uffd_test_ops->release_pages(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) {
-		perror("count_verify");
-		return 1;
-	}
+	if (!count_verify)
+		err("count_verify");
 
 	for (nr = 0; nr < nr_pages; nr++) {
 		*area_mutex(area_src, nr) =
@@ -457,16 +401,11 @@ static int uffd_test_ctx_init_ext(uint64_t *features)
 	}
 
 	pipefd = malloc(sizeof(int) * nr_cpus * 2);
-	if (!pipefd) {
-		perror("pipefd");
-		return 1;
-	}
-	for (cpu = 0; cpu < nr_cpus; cpu++) {
-		if (pipe2(&pipefd[cpu * 2], O_CLOEXEC | O_NONBLOCK)) {
-			perror("pipe");
-			return 1;
-		}
-	}
+	if (!pipefd)
+		err("pipefd");
+	for (cpu = 0; cpu < nr_cpus; cpu++)
+		if (pipe2(&pipefd[cpu * 2], O_CLOEXEC | O_NONBLOCK))
+			err("pipe");
 
 	return 0;
 }
@@ -478,12 +417,9 @@ static inline int uffd_test_ctx_init(uint64_t features)
 
 static inline int munmap_area(void **area)
 {
-	if (*area) {
-		if (munmap(*area, nr_pages * page_size)) {
-			perror("munmap");
-			return 1;
-		}
-	}
+	if (*area)
+		if (munmap(*area, nr_pages * page_size))
+			err("munmap");
 
 	*area = NULL;
 	return 0;
@@ -496,10 +432,8 @@ static int uffd_test_ctx_clear(void)
 
 	if (pipefd) {
 		for (i = 0; i < nr_cpus * 2; ++i) {
-			if (close(pipefd[i])) {
-				perror("close pipefd");
-				ret = 1;
-			}
+			if (close(pipefd[i]))
+				err("close pipefd");
 		}
 		free(pipefd);
 		pipefd = NULL;
@@ -511,10 +445,8 @@ static int uffd_test_ctx_clear(void)
 	}
 
 	if (uffd != -1) {
-		if (close(uffd)) {
-			perror("close uffd");
-			ret = 1;
-		}
+		if (close(uffd))
+			err("close uffd");
 		uffd = -1;
 	}
 
@@ -546,11 +478,8 @@ static void wp_range(int ufd, __u64 start, __u64 len, bool wp)
 	/* Undo write-protect, do wakeup after that */
 	prms.mode = wp ? UFFDIO_WRITEPROTECT_MODE_WP : 0;
 
-	if (ioctl(ufd, UFFDIO_WRITEPROTECT, &prms)) {
-		fprintf(stderr, "clear WP failed for address 0x%" PRIx64 "\n",
-			(uint64_t)start);
-		exit(1);
-	}
+	if (ioctl(ufd, UFFDIO_WRITEPROTECT, &prms))
+		err("clear WP failed: address=0x%"PRIx64, (uint64_t)start);
 }
 
 static void continue_range(int ufd, __u64 start, __u64 len)
@@ -561,12 +490,9 @@ static void continue_range(int ufd, __u64 start, __u64 len)
 	req.range.len = len;
 	req.mode = 0;
 
-	if (ioctl(ufd, UFFDIO_CONTINUE, &req)) {
-		fprintf(stderr,
-			"UFFDIO_CONTINUE failed for address 0x%" PRIx64 "\n",
-			(uint64_t)start);
-		exit(1);
-	}
+	if (ioctl(ufd, UFFDIO_CONTINUE, &req))
+		err("UFFDIO_CONTINUE failed for address 0x%" PRIx64,
+		    (uint64_t)start);
 }
 
 static void *locking_thread(void *arg)
@@ -585,10 +511,8 @@ static void *locking_thread(void *arg)
 			seed += cpu;
 		bzero(&rand, sizeof(rand));
 		bzero(&randstate, sizeof(randstate));
-		if (initstate_r(seed, randstate, sizeof(randstate), &rand)) {
-			fprintf(stderr, "srandom_r error\n");
-			exit(1);
-		}
+		if (initstate_r(seed, randstate, sizeof(randstate), &rand))
+			err("initstate_r failed");
 	} else {
 		page_nr = -bounces;
 		if (!(bounces & BOUNCE_RACINGFAULTS))
@@ -597,16 +521,12 @@ static void *locking_thread(void *arg)
 
 	while (!finished) {
 		if (bounces & BOUNCE_RANDOM) {
-			if (random_r(&rand, &rand_nr)) {
-				fprintf(stderr, "random_r 1 error\n");
-				exit(1);
-			}
+			if (random_r(&rand, &rand_nr))
+				err("random_r failed");
 			page_nr = rand_nr;
 			if (sizeof(page_nr) > sizeof(rand_nr)) {
-				if (random_r(&rand, &rand_nr)) {
-					fprintf(stderr, "random_r 2 error\n");
-					exit(1);
-				}
+				if (random_r(&rand, &rand_nr))
+					err("random_r failed");
 				page_nr |= (((unsigned long) rand_nr) << 16) <<
 					   16;
 			}
@@ -615,12 +535,9 @@ static void *locking_thread(void *arg)
 		page_nr %= nr_pages;
 		pthread_mutex_lock(area_mutex(area_dst, page_nr));
 		count = *area_count(area_dst, page_nr);
-		if (count != count_verify[page_nr]) {
-			fprintf(stderr,
-				"page_nr %lu memory corruption %Lu %Lu\n",
-				page_nr, count,
-				count_verify[page_nr]); exit(1);
-		}
+		if (count != count_verify[page_nr])
+			err("page_nr %lu memory corruption %llu %llu",
+			    page_nr, count, count_verify[page_nr]);
 		count++;
 		*area_count(area_dst, page_nr) = count_verify[page_nr] = count;
 		pthread_mutex_unlock(area_mutex(area_dst, page_nr));
@@ -637,22 +554,21 @@ static void retry_copy_page(int ufd, struct uffdio_copy *uffdio_copy,
 				     offset);
 	if (ioctl(ufd, UFFDIO_COPY, uffdio_copy)) {
 		/* real retval in ufdio_copy.copy */
-		if (uffdio_copy->copy != -EEXIST) {
-			uffd_error(uffdio_copy->copy,
-				   "UFFDIO_COPY retry error");
-		}
-	} else
-		uffd_error(uffdio_copy->copy, "UFFDIO_COPY retry unexpected");
+		if (uffdio_copy->copy != -EEXIST)
+			err("UFFDIO_COPY retry error: %"PRId64,
+			    (int64_t)uffdio_copy->copy);
+	} else {
+		err("UFFDIO_COPY retry unexpected: %"PRId64,
+		    (int64_t)uffdio_copy->copy);
+	}
 }
 
 static int __copy_page(int ufd, unsigned long offset, bool retry)
 {
 	struct uffdio_copy uffdio_copy;
 
-	if (offset >= nr_pages * page_size) {
-		fprintf(stderr, "unexpected offset %lu\n", offset);
-		exit(1);
-	}
+	if (offset >= nr_pages * page_size)
+		err("unexpected offset %lu\n", offset);
 	uffdio_copy.dst = (unsigned long) area_dst + offset;
 	uffdio_copy.src = (unsigned long) area_src + offset;
 	uffdio_copy.len = page_size;
@@ -664,9 +580,10 @@ static int __copy_page(int ufd, unsigned long offset, bool retry)
 	if (ioctl(ufd, UFFDIO_COPY, &uffdio_copy)) {
 		/* real retval in ufdio_copy.copy */
 		if (uffdio_copy.copy != -EEXIST)
-			uffd_error(uffdio_copy.copy, "UFFDIO_COPY error");
+			err("UFFDIO_COPY error: %"PRId64,
+			    (int64_t)uffdio_copy.copy);
 	} else if (uffdio_copy.copy != page_size) {
-		uffd_error(uffdio_copy.copy, "UFFDIO_COPY unexpected copy");
+		err("UFFDIO_COPY error: %"PRId64, (int64_t)uffdio_copy.copy);
 	} else {
 		if (test_uffdio_copy_eexist && retry) {
 			test_uffdio_copy_eexist = false;
@@ -695,11 +612,10 @@ static int uffd_read_msg(int ufd, struct uffd_msg *msg)
 		if (ret < 0) {
 			if (errno == EAGAIN)
 				return 1;
-			perror("blocking read error");
+			err("blocking read error");
 		} else {
-			fprintf(stderr, "short read\n");
+			err("short read");
 		}
-		exit(1);
 	}
 
 	return 0;
@@ -710,10 +626,8 @@ static void uffd_handle_page_fault(struct uffd_msg *msg,
 {
 	unsigned long offset;
 
-	if (msg->event != UFFD_EVENT_PAGEFAULT) {
-		fprintf(stderr, "unexpected msg event %u\n", msg->event);
-		exit(1);
-	}
+	if (msg->event != UFFD_EVENT_PAGEFAULT)
+		err("unexpected msg event %u", msg->event);
 
 	if (msg->arg.pagefault.flags & UFFD_PAGEFAULT_FLAG_WP) {
 		/* Write protect page faults */
@@ -744,10 +658,8 @@ static void uffd_handle_page_fault(struct uffd_msg *msg,
 		stats->minor_faults++;
 	} else {
 		/* Missing page faults */
-		if (msg->arg.pagefault.flags & UFFD_PAGEFAULT_FLAG_WRITE) {
-			fprintf(stderr, "unexpected write fault\n");
-			exit(1);
-		}
+		if (msg->arg.pagefault.flags & UFFD_PAGEFAULT_FLAG_WRITE)
+			err("unexpected write fault");
 
 		offset = (char *)(unsigned long)msg->arg.pagefault.address - area_dst;
 		offset &= ~(page_size-1);
@@ -774,32 +686,20 @@ static void *uffd_poll_thread(void *arg)
 
 	for (;;) {
 		ret = poll(pollfd, 2, -1);
-		if (!ret) {
-			fprintf(stderr, "poll error %d\n", ret);
-			exit(1);
-		}
-		if (ret < 0) {
-			perror("poll");
-			exit(1);
-		}
+		if (ret <= 0)
+			err("poll error: %d", ret);
 		if (pollfd[1].revents & POLLIN) {
-			if (read(pollfd[1].fd, &tmp_chr, 1) != 1) {
-				fprintf(stderr, "read pipefd error\n");
-				exit(1);
-			}
+			if (read(pollfd[1].fd, &tmp_chr, 1) != 1)
+				err("read pipefd error");
 			break;
 		}
-		if (!(pollfd[0].revents & POLLIN)) {
-			fprintf(stderr, "pollfd[0].revents %d\n",
-				pollfd[0].revents);
-			exit(1);
-		}
+		if (!(pollfd[0].revents & POLLIN))
+			err("pollfd[0].revents %d", pollfd[0].revents);
 		if (uffd_read_msg(uffd, &msg))
 			continue;
 		switch (msg.event) {
 		default:
-			fprintf(stderr, "unexpected msg event %u\n",
-				msg.event); exit(1);
+			err("unexpected msg event %u\n", msg.event);
 			break;
 		case UFFD_EVENT_PAGEFAULT:
 			uffd_handle_page_fault(&msg, stats);
@@ -813,10 +713,8 @@ static void *uffd_poll_thread(void *arg)
 			uffd_reg.range.start = msg.arg.remove.start;
 			uffd_reg.range.len = msg.arg.remove.end -
 				msg.arg.remove.start;
-			if (ioctl(uffd, UFFDIO_UNREGISTER, &uffd_reg.range)) {
-				fprintf(stderr, "remove failure\n");
-				exit(1);
-			}
+			if (ioctl(uffd, UFFDIO_UNREGISTER, &uffd_reg.range))
+				err("remove failure");
 			break;
 		case UFFD_EVENT_REMAP:
 			area_dst = (char *)(unsigned long)msg.arg.remap.to;
@@ -919,9 +817,7 @@ static int stress(struct uffd_stats *uffd_stats)
 	 * UFFDIO_COPY without writing zero pages into area_dst
 	 * because the background threads already completed).
 	 */
-	if (uffd_test_ops->release_pages(area_src))
-		return 1;
-
+	uffd_test_ops->release_pages(area_src);
 
 	finished = 1;
 	for (cpu = 0; cpu < nr_cpus; cpu++)
@@ -931,10 +827,8 @@ static int stress(struct uffd_stats *uffd_stats)
 	for (cpu = 0; cpu < nr_cpus; cpu++) {
 		char c;
 		if (bounces & BOUNCE_POLL) {
-			if (write(pipefd[cpu*2+1], &c, 1) != 1) {
-				fprintf(stderr, "pipefd write error\n");
-				return 1;
-			}
+			if (write(pipefd[cpu*2+1], &c, 1) != 1)
+				err("pipefd write error");
 			if (pthread_join(uffd_threads[cpu],
 					 (void *)&uffd_stats[cpu]))
 				return 1;
@@ -1000,10 +894,8 @@ static int faulting_process(int signal_test)
 		memset(&act, 0, sizeof(act));
 		act.sa_sigaction = sighndl;
 		act.sa_flags = SA_SIGINFO;
-		if (sigaction(SIGBUS, &act, 0)) {
-			perror("sigaction");
-			return 1;
-		}
+		if (sigaction(SIGBUS, &act, 0))
+			err("sigaction");
 		lastnr = (unsigned long)-1;
 	}
 
@@ -1013,10 +905,8 @@ static int faulting_process(int signal_test)
 
 		if (signal_test) {
 			if (sigsetjmp(*sigbuf, 1) != 0) {
-				if (steps == 1 && nr == lastnr) {
-					fprintf(stderr, "Signal repeated\n");
-					return 1;
-				}
+				if (steps == 1 && nr == lastnr)
+					err("Signal repeated");
 
 				lastnr = nr;
 				if (signal_test == 1) {
@@ -1041,12 +931,9 @@ static int faulting_process(int signal_test)
 		}
 
 		count = *area_count(area_dst, nr);
-		if (count != count_verify[nr]) {
-			fprintf(stderr,
-				"nr %lu memory corruption %Lu %Lu\n",
-				nr, count,
-				count_verify[nr]);
-	        }
+		if (count != count_verify[nr])
+			err("nr %lu memory corruption %llu %llu\n",
+			    nr, count, count_verify[nr]);
 		/*
 		 * Trigger write protection if there is by writing
 		 * the same value back.
@@ -1062,20 +949,16 @@ static int faulting_process(int signal_test)
 
 	area_dst = mremap(area_dst, nr_pages * page_size,  nr_pages * page_size,
 			  MREMAP_MAYMOVE | MREMAP_FIXED, area_src);
-	if (area_dst == MAP_FAILED) {
-		perror("mremap");
-		exit(1);
-	}
+	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);
 		if (count != count_verify[nr]) {
-			fprintf(stderr,
-				"nr %lu memory corruption %Lu %Lu\n",
-				nr, count,
-				count_verify[nr]); exit(1);
+			err("nr %lu memory corruption %llu %llu\n",
+			    nr, count, count_verify[nr]);
 		}
 		/*
 		 * Trigger write protection if there is by writing
@@ -1084,15 +967,11 @@ static int faulting_process(int signal_test)
 		*area_count(area_dst, nr) = count;
 	}
 
-	if (uffd_test_ops->release_pages(area_dst))
-		return 1;
+	uffd_test_ops->release_pages(area_dst);
 
-	for (nr = 0; nr < nr_pages; nr++) {
-		if (my_bcmp(area_dst + nr * page_size, zeropage, page_size)) {
-			fprintf(stderr, "nr %lu is not zero\n", nr);
-			exit(1);
-		}
-	}
+	for (nr = 0; nr < nr_pages; nr++)
+		if (my_bcmp(area_dst + nr * page_size, zeropage, page_size))
+			err("nr %lu is not zero", nr);
 
 	return 0;
 }
@@ -1105,13 +984,12 @@ static void retry_uffdio_zeropage(int ufd,
 				     uffdio_zeropage->range.len,
 				     offset);
 	if (ioctl(ufd, UFFDIO_ZEROPAGE, uffdio_zeropage)) {
-		if (uffdio_zeropage->zeropage != -EEXIST) {
-			uffd_error(uffdio_zeropage->zeropage,
-				   "UFFDIO_ZEROPAGE retry error");
-		}
+		if (uffdio_zeropage->zeropage != -EEXIST)
+			err("UFFDIO_ZEROPAGE error: %"PRId64,
+			    (int64_t)uffdio_zeropage->zeropage);
 	} else {
-		uffd_error(uffdio_zeropage->zeropage,
-			   "UFFDIO_ZEROPAGE retry unexpected");
+		err("UFFDIO_ZEROPAGE error: %"PRId64,
+		    (int64_t)uffdio_zeropage->zeropage);
 	}
 }
 
@@ -1124,10 +1002,8 @@ static int __uffdio_zeropage(int ufd, unsigned long offset, bool retry)
 
 	has_zeropage = uffd_test_ops->expected_ioctls & (1 << _UFFDIO_ZEROPAGE);
 
-	if (offset >= nr_pages * page_size) {
-		fprintf(stderr, "unexpected offset %lu\n", offset);
-		exit(1);
-	}
+	if (offset >= nr_pages * page_size)
+		err("unexpected offset %lu", offset);
 	uffdio_zeropage.range.start = (unsigned long) area_dst + offset;
 	uffdio_zeropage.range.len = page_size;
 	uffdio_zeropage.mode = 0;
@@ -1135,14 +1011,13 @@ static int __uffdio_zeropage(int ufd, unsigned long offset, bool retry)
 	res = uffdio_zeropage.zeropage;
 	if (ret) {
 		/* real retval in ufdio_zeropage.zeropage */
-		if (has_zeropage) {
-			uffd_error(res, "UFFDIO_ZEROPAGE %s",
-				   res == -EEXIST ? "-EEXIST" : "error");
-		} else if (res != -EINVAL)
-			uffd_error(res, "UFFDIO_ZEROPAGE not -EINVAL");
+		if (has_zeropage)
+			err("UFFDIO_ZEROPAGE error: %"PRId64, (int64_t)res);
+		else if (res != -EINVAL)
+			err("UFFDIO_ZEROPAGE not -EINVAL");
 	} else if (has_zeropage) {
 		if (res != page_size) {
-			uffd_error(res, "UFFDIO_ZEROPAGE unexpected");
+			err("UFFDIO_ZEROPAGE unexpected size");
 		} else {
 			if (test_uffdio_zeropage_eexist && retry) {
 				test_uffdio_zeropage_eexist = false;
@@ -1152,7 +1027,7 @@ static int __uffdio_zeropage(int ufd, unsigned long offset, bool retry)
 			return 1;
 		}
 	} else
-		uffd_error(res, "UFFDIO_ZEROPAGE succeeded");
+		err("UFFDIO_ZEROPAGE succeeded");
 
 	return 0;
 }
@@ -1179,25 +1054,16 @@ static int userfaultfd_zeropage_test(void)
 	uffdio_register.mode = UFFDIO_REGISTER_MODE_MISSING;
 	if (test_uffdio_wp)
 		uffdio_register.mode |= UFFDIO_REGISTER_MODE_WP;
-	if (ioctl(uffd, UFFDIO_REGISTER, &uffdio_register)) {
-		fprintf(stderr, "register failure\n");
-		exit(1);
-	}
+	if (ioctl(uffd, UFFDIO_REGISTER, &uffdio_register))
+		err("register failure");
 
 	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 ((uffdio_register.ioctls & expected_ioctls) != expected_ioctls)
+		err("unexpected missing ioctl for anon memory");
 
-	if (uffdio_zeropage(uffd, 0)) {
-		if (my_bcmp(area_dst, zeropage, page_size)) {
-			fprintf(stderr, "zeropage is not zero\n");
-			exit(1);
-		}
-	}
+	if (uffdio_zeropage(uffd, 0))
+		if (my_bcmp(area_dst, zeropage, page_size))
+			err("zeropage is not zero");
 
 	printf("done.\n");
 	return 0;
@@ -1228,41 +1094,28 @@ static int userfaultfd_events_test(void)
 	uffdio_register.mode = UFFDIO_REGISTER_MODE_MISSING;
 	if (test_uffdio_wp)
 		uffdio_register.mode |= UFFDIO_REGISTER_MODE_WP;
-	if (ioctl(uffd, UFFDIO_REGISTER, &uffdio_register)) {
-		fprintf(stderr, "register failure\n");
-		exit(1);
-	}
+	if (ioctl(uffd, UFFDIO_REGISTER, &uffdio_register))
+		err("register failure");
 
 	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 ((uffdio_register.ioctls & expected_ioctls) != expected_ioctls)
+		err("unexpected missing ioctl for anon memory");
 
-	if (pthread_create(&uffd_mon, &attr, uffd_poll_thread, &stats)) {
-		perror("uffd_poll_thread create");
-		exit(1);
-	}
+	if (pthread_create(&uffd_mon, &attr, uffd_poll_thread, &stats))
+		err("uffd_poll_thread create");
 
 	pid = fork();
-	if (pid < 0) {
-		perror("fork");
-		exit(1);
-	}
+	if (pid < 0)
+		err("fork");
 
 	if (!pid)
 		exit(faulting_process(0));
 
 	waitpid(pid, &err, 0);
-	if (err) {
-		fprintf(stderr, "faulting process failed\n");
-		exit(1);
-	}
-
-	if (write(pipefd[1], &c, sizeof(c)) != sizeof(c)) {
-		perror("pipe write");
-		exit(1);
-	}
+	if (err)
+		err("faulting process failed");
+	if (write(pipefd[1], &c, sizeof(c)) != sizeof(c))
+		err("pipe write");
 	if (pthread_join(uffd_mon, NULL))
 		return 1;
 
@@ -1296,56 +1149,39 @@ static int userfaultfd_sig_test(void)
 	uffdio_register.mode = UFFDIO_REGISTER_MODE_MISSING;
 	if (test_uffdio_wp)
 		uffdio_register.mode |= UFFDIO_REGISTER_MODE_WP;
-	if (ioctl(uffd, UFFDIO_REGISTER, &uffdio_register)) {
-		fprintf(stderr, "register failure\n");
-		exit(1);
-	}
+	if (ioctl(uffd, UFFDIO_REGISTER, &uffdio_register))
+		err("register failure");
 
 	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 ((uffdio_register.ioctls & expected_ioctls) != expected_ioctls)
+		err("unexpected missing ioctl for anon memory");
 
-	if (faulting_process(1)) {
-		fprintf(stderr, "faulting process failed\n");
-		exit(1);
-	}
+	if (faulting_process(1))
+		err("faulting process failed");
 
-	if (uffd_test_ops->release_pages(area_dst))
-		return 1;
+	uffd_test_ops->release_pages(area_dst);
 
-	if (pthread_create(&uffd_mon, &attr, uffd_poll_thread, &stats)) {
-		perror("uffd_poll_thread create");
-		exit(1);
-	}
+	if (pthread_create(&uffd_mon, &attr, uffd_poll_thread, &stats))
+		err("uffd_poll_thread create");
 
 	pid = fork();
-	if (pid < 0) {
-		perror("fork");
-		exit(1);
-	}
+	if (pid < 0)
+		err("fork");
 
 	if (!pid)
 		exit(faulting_process(2));
 
 	waitpid(pid, &err, 0);
-	if (err) {
-		fprintf(stderr, "faulting process failed\n");
-		exit(1);
-	}
-
-	if (write(pipefd[1], &c, sizeof(c)) != sizeof(c)) {
-		perror("pipe write");
-		exit(1);
-	}
+	if (err)
+		err("faulting process failed");
+	if (write(pipefd[1], &c, sizeof(c)) != sizeof(c))
+		err("pipe write");
 	if (pthread_join(uffd_mon, (void **)&userfaults))
 		return 1;
 
 	printf("done.\n");
 	if (userfaults)
-		fprintf(stderr, "Signal test failed, userfaults: %ld\n",
-			userfaults);
+		err("Signal test failed, userfaults: %ld", userfaults);
 	return userfaults != 0;
 }
 
@@ -1387,17 +1223,13 @@ static int userfaultfd_minor_test(void)
 	uffdio_register.range.start = (unsigned long)area_dst_alias;
 	uffdio_register.range.len = nr_pages * page_size;
 	uffdio_register.mode = UFFDIO_REGISTER_MODE_MINOR;
-	if (ioctl(uffd, UFFDIO_REGISTER, &uffdio_register)) {
-		perror("register failure");
-		exit(1);
-	}
+	if (ioctl(uffd, UFFDIO_REGISTER, &uffdio_register))
+		err("register failure");
 
 	expected_ioctls = uffd_test_ops->expected_ioctls;
 	expected_ioctls |= 1 << _UFFDIO_CONTINUE;
-	if ((uffdio_register.ioctls & expected_ioctls) != expected_ioctls) {
-		fprintf(stderr, "unexpected missing ioctl(s)\n");
-		exit(1);
-	}
+	if ((uffdio_register.ioctls & expected_ioctls) != expected_ioctls)
+		err("unexpected missing ioctl(s)");
 
 	/*
 	 * After registering with UFFD, populate the non-UFFD-registered side of
@@ -1408,10 +1240,8 @@ static int userfaultfd_minor_test(void)
 		       page_size);
 	}
 
-	if (pthread_create(&uffd_mon, &attr, uffd_poll_thread, &stats)) {
-		perror("uffd_poll_thread create");
-		exit(1);
-	}
+	if (pthread_create(&uffd_mon, &attr, uffd_poll_thread, &stats))
+		err("uffd_poll_thread create");
 
 	/*
 	 * Read each of the pages back using the UFFD-registered mapping. We
@@ -1420,26 +1250,19 @@ static int userfaultfd_minor_test(void)
 	 * page's contents, and then issuing a CONTINUE ioctl.
 	 */
 
-	if (posix_memalign(&expected_page, page_size, page_size)) {
-		fprintf(stderr, "out of memory\n");
-		return 1;
-	}
+	if (posix_memalign(&expected_page, page_size, page_size))
+		err("out of memory");
 
 	for (p = 0; p < nr_pages; ++p) {
 		expected_byte = ~((uint8_t)(p % ((uint8_t)-1)));
 		memset(expected_page, expected_byte, page_size);
 		if (my_bcmp(expected_page, area_dst_alias + (p * page_size),
-			    page_size)) {
-			fprintf(stderr,
-				"unexpected page contents after minor fault\n");
-			exit(1);
-		}
+			    page_size))
+			err("unexpected page contents after minor fault");
 	}
 
-	if (write(pipefd[1], &c, sizeof(c)) != sizeof(c)) {
-		perror("pipe write");
-		exit(1);
-	}
+	if (write(pipefd[1], &c, sizeof(c)) != sizeof(c))
+		err("pipe write");
 	if (pthread_join(uffd_mon, NULL))
 		return 1;
 
@@ -1454,16 +1277,13 @@ static int userfaultfd_stress(void)
 	char *tmp_area;
 	unsigned long nr;
 	struct uffdio_register uffdio_register;
-	int err;
 	struct uffd_stats uffd_stats[nr_cpus];
 
 	if (uffd_test_ctx_init(0))
 		return 1;
 
-	if (posix_memalign(&area, page_size, page_size)) {
-		fprintf(stderr, "out of memory\n");
-		return 1;
-	}
+	if (posix_memalign(&area, page_size, page_size))
+		err("out of memory");
 	zeropage = area;
 	bzero(zeropage, page_size);
 
@@ -1472,7 +1292,6 @@ static int userfaultfd_stress(void)
 	pthread_attr_init(&attr);
 	pthread_attr_setstacksize(&attr, 16*1024*1024);
 
-	err = 0;
 	while (bounces--) {
 		unsigned long expected_ioctls;
 
@@ -1501,25 +1320,18 @@ static int userfaultfd_stress(void)
 		uffdio_register.mode = UFFDIO_REGISTER_MODE_MISSING;
 		if (test_uffdio_wp)
 			uffdio_register.mode |= UFFDIO_REGISTER_MODE_WP;
-		if (ioctl(uffd, UFFDIO_REGISTER, &uffdio_register)) {
-			fprintf(stderr, "register failure\n");
-			return 1;
-		}
+		if (ioctl(uffd, UFFDIO_REGISTER, &uffdio_register))
+			err("register failure");
 		expected_ioctls = uffd_test_ops->expected_ioctls;
 		if ((uffdio_register.ioctls & expected_ioctls) !=
-		    expected_ioctls) {
-			fprintf(stderr,
-				"unexpected missing ioctl for anon memory\n");
-			return 1;
-		}
+		    expected_ioctls)
+			err("unexpected missing ioctl for anon memory");
 
 		if (area_dst_alias) {
 			uffdio_register.range.start = (unsigned long)
 				area_dst_alias;
-			if (ioctl(uffd, UFFDIO_REGISTER, &uffdio_register)) {
-				fprintf(stderr, "register failure alias\n");
-				return 1;
-			}
+			if (ioctl(uffd, UFFDIO_REGISTER, &uffdio_register))
+				err("register failure alias");
 		}
 
 		/*
@@ -1546,8 +1358,7 @@ static int userfaultfd_stress(void)
 		 * MADV_DONTNEED only after the UFFDIO_REGISTER, so it's
 		 * required to MADV_DONTNEED here.
 		 */
-		if (uffd_test_ops->release_pages(area_dst))
-			return 1;
+		uffd_test_ops->release_pages(area_dst);
 
 		uffd_stats_reset(uffd_stats, nr_cpus);
 
@@ -1561,33 +1372,22 @@ static int userfaultfd_stress(void)
 				 nr_pages * page_size, false);
 
 		/* unregister */
-		if (ioctl(uffd, UFFDIO_UNREGISTER, &uffdio_register.range)) {
-			fprintf(stderr, "unregister failure\n");
-			return 1;
-		}
+		if (ioctl(uffd, UFFDIO_UNREGISTER, &uffdio_register.range))
+			err("unregister failure");
 		if (area_dst_alias) {
 			uffdio_register.range.start = (unsigned long) area_dst;
 			if (ioctl(uffd, UFFDIO_UNREGISTER,
-				  &uffdio_register.range)) {
-				fprintf(stderr, "unregister failure alias\n");
-				return 1;
-			}
+				  &uffdio_register.range))
+				err("unregister failure alias");
 		}
 
 		/* verification */
-		if (bounces & BOUNCE_VERIFY) {
-			for (nr = 0; nr < nr_pages; nr++) {
-				if (*area_count(area_dst, nr) != count_verify[nr]) {
-					fprintf(stderr,
-						"error area_count %Lu %Lu %lu\n",
-						*area_count(area_src, nr),
-						count_verify[nr],
-						nr);
-					err = 1;
-					bounces = 0;
-				}
-			}
-		}
+		if (bounces & BOUNCE_VERIFY)
+			for (nr = 0; nr < nr_pages; nr++)
+				if (*area_count(area_dst, nr) != count_verify[nr])
+					err("error area_count %llu %llu %lu\n",
+					    *area_count(area_src, nr),
+					    count_verify[nr], nr);
 
 		/* prepare next bounce */
 		tmp_area = area_src;
@@ -1601,9 +1401,6 @@ static int userfaultfd_stress(void)
 		uffd_stats_report(uffd_stats, nr_cpus);
 	}
 
-	if (err)
-		return err;
-
 	return userfaultfd_zeropage_test() || userfaultfd_sig_test()
 		|| userfaultfd_events_test() || userfaultfd_minor_test();
 }
@@ -1654,7 +1451,7 @@ static void set_test_type(const char *type)
 		uffd_test_ops = &shmem_uffd_test_ops;
 		test_uffdio_minor = true;
 	} else {
-		fprintf(stderr, "Unknown test type: %s\n", type); exit(1);
+		err("Unknown test type: %s", type);
 	}
 
 	if (test_type == TEST_HUGETLB)
@@ -1662,15 +1459,11 @@ static void set_test_type(const char *type)
 	else
 		page_size = sysconf(_SC_PAGE_SIZE);
 
-	if (!page_size) {
-		fprintf(stderr, "Unable to determine page size\n");
-		exit(2);
-	}
+	if (!page_size)
+		err("Unable to determine page size");
 	if ((unsigned long) area_count(NULL, 0) + sizeof(unsigned long long) * 2
-	    > page_size) {
-		fprintf(stderr, "Impossible to run this test\n");
-		exit(2);
-	}
+	    > page_size)
+		err("Impossible to run this test");
 }
 
 static void sigalrm(int sig)
@@ -1687,10 +1480,8 @@ int main(int argc, char **argv)
 	if (argc < 4)
 		usage();
 
-	if (signal(SIGALRM, sigalrm) == SIG_ERR) {
-		fprintf(stderr, "failed to arm SIGALRM");
-		exit(1);
-	}
+	if (signal(SIGALRM, sigalrm) == SIG_ERR)
+		err("failed to arm SIGALRM");
 	alarm(ALARM_INTERVAL_SECS);
 
 	set_test_type(argv[1]);
@@ -1699,13 +1490,13 @@ int main(int argc, char **argv)
 	nr_pages_per_cpu = atol(argv[2]) * 1024*1024 / page_size /
 		nr_cpus;
 	if (!nr_pages_per_cpu) {
-		fprintf(stderr, "invalid MiB\n");
+		_err("invalid MiB");
 		usage();
 	}
 
 	bounces = atoi(argv[3]);
 	if (bounces <= 0) {
-		fprintf(stderr, "invalid bounces\n");
+		_err("invalid bounces");
 		usage();
 	}
 	nr_pages = nr_pages_per_cpu * nr_cpus;
@@ -1714,32 +1505,20 @@ int main(int argc, char **argv)
 		if (argc < 5)
 			usage();
 		huge_fd = open(argv[4], O_CREAT | O_RDWR, 0755);
-		if (huge_fd < 0) {
-			fprintf(stderr, "Open of %s failed", argv[4]);
-			perror("open");
-			exit(1);
-		}
-		if (ftruncate(huge_fd, 0)) {
-			fprintf(stderr, "ftruncate %s to size 0 failed", argv[4]);
-			perror("ftruncate");
-			exit(1);
-		}
+		if (huge_fd < 0)
+			err("Open of %s failed", argv[4]);
+		if (ftruncate(huge_fd, 0))
+			err("ftruncate %s to size 0 failed", argv[4]);
 	} else if (test_type == TEST_SHMEM) {
 		shm_fd = memfd_create(argv[0], 0);
-		if (shm_fd < 0) {
-			perror("memfd_create");
-			exit(1);
-		}
-		if (ftruncate(shm_fd, nr_pages * page_size * 2)) {
-			perror("ftruncate");
-			exit(1);
-		}
+		if (shm_fd < 0)
+			err("memfd_create");
+		if (ftruncate(shm_fd, nr_pages * page_size * 2))
+			err("ftruncate");
 		if (fallocate(shm_fd,
 			      FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE, 0,
-			      nr_pages * page_size * 2)) {
-			perror("fallocate");
-			exit(1);
-		}
+			      nr_pages * page_size * 2))
+			err("fallocate");
 	}
 	printf("nr_pages: %lu, nr_pages_per_cpu: %lu\n",
 	       nr_pages, nr_pages_per_cpu);
-- 
2.26.2

Re: [PATCH 0/5] userfaultfd/selftests: A few cleanups

[Axel Rasmussen]

These look like good cleanups to me! I reviewed all of the patches,
and tried out the resulting selftest program, it seems to work
correctly. So, for what it's worth:

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


On Tue, Mar 9, 2021 at 4:45 PM Peter Xu <peterx@redhat.com> wrote:
>
> Based on v5.12-rc2-mmots-2021-03-08-21-54.
>
> I wanted to cleanup userfaultfd.c fault handling for a long time. If it's not
> cleaned, when the new code grows the file it'll also grow the size that needs
> to be cleaned...  This is my attempt to cleanup the userfaultfd selftest on
> fault handling, to use an err() macro instead of either fprintf() or perror()
> then another exit() call.
>
> The huge cleanup is done in the last patch.  The first 4 patches are some other
> standalone cleanups for the same file, so I put them together.
>
> Please review, thanks.
>
> Peter Xu (5):
>   userfaultfd/selftests: Use user mode only
>   userfaultfd/selftests: Remove the time() check on delayed uffd
>   userfaultfd/selftests: Dropping VERIFY check in locking_thread
>   userfaultfd/selftests: Only dump counts if mode enabled
>   userfaultfd/selftests: Unify error handling
>
>  tools/testing/selftests/vm/userfaultfd.c | 742 +++++++----------------
>  1 file changed, 235 insertions(+), 507 deletions(-)
>
> --
> 2.26.2
>
>