1 files changed, 471 insertions, 0 deletions
diff --git a/tools/testing/selftests/mm/uffd-stress.c b/tools/testing/selftests/mm/uffd-stress.c
new file mode 100644
index 0000000000..469e0476af
--- /dev/null
+++ b/tools/testing/selftests/mm/uffd-stress.c
@@ -0,0 +1,471 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Stress userfaultfd syscall.
+ *
+ *  Copyright (C) 2015  Red Hat, Inc.
+ *
+ * This test allocates two virtual areas and bounces the physical
+ * memory across the two virtual areas (from area_src to area_dst)
+ * using userfaultfd.
+ *
+ * There are three threads running per CPU:
+ *
+ * 1) one per-CPU thread takes a per-page pthread_mutex in a random
+ *    page of the area_dst (while the physical page may still be in
+ *    area_src), and increments a per-page counter in the same page,
+ *    and checks its value against a verification region.
+ *
+ * 2) another per-CPU thread handles the userfaults generated by
+ *    thread 1 above. userfaultfd blocking reads or poll() modes are
+ *    exercised interleaved.
+ *
+ * 3) one last per-CPU thread transfers the memory in the background
+ *    at maximum bandwidth (if not already transferred by thread
+ *    2). Each cpu thread takes cares of transferring a portion of the
+ *    area.
+ *
+ * When all threads of type 3 completed the transfer, one bounce is
+ * complete. area_src and area_dst are then swapped. All threads are
+ * respawned and so the bounce is immediately restarted in the
+ * opposite direction.
+ *
+ * per-CPU threads 1 by triggering userfaults inside
+ * pthread_mutex_lock will also verify the atomicity of the memory
+ * transfer (UFFDIO_COPY).
+ */
+
+#include "uffd-common.h"
+
+#ifdef __NR_userfaultfd
+
+#define BOUNCE_RANDOM		(1<<0)
+#define BOUNCE_RACINGFAULTS	(1<<1)
+#define BOUNCE_VERIFY		(1<<2)
+#define BOUNCE_POLL		(1<<3)
+static int bounces;
+
+/* exercise the test_uffdio_*_eexist every ALARM_INTERVAL_SECS */
+#define ALARM_INTERVAL_SECS 10
+static char *zeropage;
+pthread_attr_t attr;
+
+#define swap(a, b) \
+	do { typeof(a) __tmp = (a); (a) = (b); (b) = __tmp; } while (0)
+
+const char *examples =
+	"# Run anonymous memory test on 100MiB region with 99999 bounces:\n"
+	"./uffd-stress anon 100 99999\n\n"
+	"# Run share memory test on 1GiB region with 99 bounces:\n"
+	"./uffd-stress shmem 1000 99\n\n"
+	"# Run hugetlb memory test on 256MiB region with 50 bounces:\n"
+	"./uffd-stress hugetlb 256 50\n\n"
+	"# Run the same hugetlb test but using private file:\n"
+	"./uffd-stress hugetlb-private 256 50\n\n"
+	"# 10MiB-~6GiB 999 bounces anonymous test, "
+	"continue forever unless an error triggers\n"
+	"while ./uffd-stress anon $[RANDOM % 6000 + 10] 999; do true; done\n\n";
+
+static void usage(void)
+{
+	fprintf(stderr, "\nUsage: ./uffd-stress <test type> <MiB> <bounces>\n\n");
+	fprintf(stderr, "Supported <test type>: anon, hugetlb, "
+		"hugetlb-private, shmem, shmem-private\n\n");
+	fprintf(stderr, "Examples:\n\n");
+	fprintf(stderr, "%s", examples);
+	exit(1);
+}
+
+static void uffd_stats_reset(struct uffd_args *args, unsigned long n_cpus)
+{
+	int i;
+
+	for (i = 0; i < n_cpus; i++) {
+		args[i].cpu = i;
+		args[i].apply_wp = test_uffdio_wp;
+		args[i].missing_faults = 0;
+		args[i].wp_faults = 0;
+		args[i].minor_faults = 0;
+	}
+}
+
+static void *locking_thread(void *arg)
+{
+	unsigned long cpu = (unsigned long) arg;
+	unsigned long page_nr;
+	unsigned long long count;
+
+	if (!(bounces & BOUNCE_RANDOM)) {
+		page_nr = -bounces;
+		if (!(bounces & BOUNCE_RACINGFAULTS))
+			page_nr += cpu * nr_pages_per_cpu;
+	}
+
+	while (!finished) {
+		if (bounces & BOUNCE_RANDOM) {
+			if (getrandom(&page_nr, sizeof(page_nr), 0) != sizeof(page_nr))
+				err("getrandom failed");
+		} else
+			page_nr += 1;
+		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])
+			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));
+	}
+
+	return NULL;
+}
+
+static int copy_page_retry(int ufd, unsigned long offset)
+{
+	return __copy_page(ufd, offset, true, test_uffdio_wp);
+}
+
+pthread_mutex_t uffd_read_mutex = PTHREAD_MUTEX_INITIALIZER;
+
+static void *uffd_read_thread(void *arg)
+{
+	struct uffd_args *args = (struct uffd_args *)arg;
+	struct uffd_msg msg;
+
+	pthread_mutex_unlock(&uffd_read_mutex);
+	/* from here cancellation is ok */
+
+	for (;;) {
+		if (uffd_read_msg(uffd, &msg))
+			continue;
+		uffd_handle_page_fault(&msg, args);
+	}
+
+	return NULL;
+}
+
+static void *background_thread(void *arg)
+{
+	unsigned long cpu = (unsigned long) arg;
+	unsigned long page_nr, start_nr, mid_nr, end_nr;
+
+	start_nr = cpu * nr_pages_per_cpu;
+	end_nr = (cpu+1) * nr_pages_per_cpu;
+	mid_nr = (start_nr + end_nr) / 2;
+
+	/* Copy the first half of the pages */
+	for (page_nr = start_nr; page_nr < mid_nr; page_nr++)
+		copy_page_retry(uffd, page_nr * page_size);
+
+	/*
+	 * If we need to test uffd-wp, set it up now.  Then we'll have
+	 * at least the first half of the pages mapped already which
+	 * can be write-protected for testing
+	 */
+	if (test_uffdio_wp)
+		wp_range(uffd, (unsigned long)area_dst + start_nr * page_size,
+			nr_pages_per_cpu * page_size, true);
+
+	/*
+	 * Continue the 2nd half of the page copying, handling write
+	 * protection faults if any
+	 */
+	for (page_nr = mid_nr; page_nr < end_nr; page_nr++)
+		copy_page_retry(uffd, page_nr * page_size);
+
+	return NULL;
+}
+
+static int stress(struct uffd_args *args)
+{
+	unsigned long cpu;
+	pthread_t locking_threads[nr_cpus];
+	pthread_t uffd_threads[nr_cpus];
+	pthread_t background_threads[nr_cpus];
+
+	finished = 0;
+	for (cpu = 0; cpu < nr_cpus; cpu++) {
+		if (pthread_create(&locking_threads[cpu], &attr,
+				   locking_thread, (void *)cpu))
+			return 1;
+		if (bounces & BOUNCE_POLL) {
+			if (pthread_create(&uffd_threads[cpu], &attr, uffd_poll_thread, &args[cpu]))
+				err("uffd_poll_thread create");
+		} else {
+			if (pthread_create(&uffd_threads[cpu], &attr,
+					   uffd_read_thread,
+					   (void *)&args[cpu]))
+				return 1;
+			pthread_mutex_lock(&uffd_read_mutex);
+		}
+		if (pthread_create(&background_threads[cpu], &attr,
+				   background_thread, (void *)cpu))
+			return 1;
+	}
+	for (cpu = 0; cpu < nr_cpus; cpu++)
+		if (pthread_join(background_threads[cpu], NULL))
+			return 1;
+
+	/*
+	 * Be strict and immediately zap area_src, the whole area has
+	 * been transferred already by the background treads. The
+	 * area_src could then be faulted in a racy way by still
+	 * running uffdio_threads reading zeropages after we zapped
+	 * area_src (but they're guaranteed to get -EEXIST from
+	 * UFFDIO_COPY without writing zero pages into area_dst
+	 * because the background threads already completed).
+	 */
+	uffd_test_ops->release_pages(area_src);
+
+	finished = 1;
+	for (cpu = 0; cpu < nr_cpus; cpu++)
+		if (pthread_join(locking_threads[cpu], NULL))
+			return 1;
+
+	for (cpu = 0; cpu < nr_cpus; cpu++) {
+		char c;
+		if (bounces & BOUNCE_POLL) {
+			if (write(pipefd[cpu*2+1], &c, 1) != 1)
+				err("pipefd write error");
+			if (pthread_join(uffd_threads[cpu],
+					 (void *)&args[cpu]))
+				return 1;
+		} else {
+			if (pthread_cancel(uffd_threads[cpu]))
+				return 1;
+			if (pthread_join(uffd_threads[cpu], NULL))
+				return 1;
+		}
+	}
+
+	return 0;
+}
+
+static int userfaultfd_stress(void)
+{
+	void *area;
+	unsigned long nr;
+	struct uffd_args args[nr_cpus];
+	uint64_t mem_size = nr_pages * page_size;
+
+	memset(args, 0, sizeof(struct uffd_args) * nr_cpus);
+
+	if (uffd_test_ctx_init(UFFD_FEATURE_WP_UNPOPULATED, NULL))
+		err("context init failed");
+
+	if (posix_memalign(&area, page_size, page_size))
+		err("out of memory");
+	zeropage = area;
+	bzero(zeropage, page_size);
+
+	pthread_mutex_lock(&uffd_read_mutex);
+
+	pthread_attr_init(&attr);
+	pthread_attr_setstacksize(&attr, 16*1024*1024);
+
+	while (bounces--) {
+		printf("bounces: %d, mode:", bounces);
+		if (bounces & BOUNCE_RANDOM)
+			printf(" rnd");
+		if (bounces & BOUNCE_RACINGFAULTS)
+			printf(" racing");
+		if (bounces & BOUNCE_VERIFY)
+			printf(" ver");
+		if (bounces & BOUNCE_POLL)
+			printf(" poll");
+		else
+			printf(" read");
+		printf(", ");
+		fflush(stdout);
+
+		if (bounces & BOUNCE_POLL)
+			fcntl(uffd, F_SETFL, uffd_flags | O_NONBLOCK);
+		else
+			fcntl(uffd, F_SETFL, uffd_flags & ~O_NONBLOCK);
+
+		/* register */
+		if (uffd_register(uffd, area_dst, mem_size,
+				  true, test_uffdio_wp, false))
+			err("register failure");
+
+		if (area_dst_alias) {
+			if (uffd_register(uffd, area_dst_alias, mem_size,
+					  true, test_uffdio_wp, false))
+				err("register failure alias");
+		}
+
+		/*
+		 * The madvise done previously isn't enough: some
+		 * uffd_thread could have read userfaults (one of
+		 * those already resolved by the background thread)
+		 * and it may be in the process of calling
+		 * UFFDIO_COPY. UFFDIO_COPY will read the zapped
+		 * area_src and it would map a zero page in it (of
+		 * course such a UFFDIO_COPY is perfectly safe as it'd
+		 * return -EEXIST). The problem comes at the next
+		 * bounce though: that racing UFFDIO_COPY would
+		 * generate zeropages in the area_src, so invalidating
+		 * the previous MADV_DONTNEED. Without this additional
+		 * MADV_DONTNEED those zeropages leftovers in the
+		 * area_src would lead to -EEXIST failure during the
+		 * next bounce, effectively leaving a zeropage in the
+		 * area_dst.
+		 *
+		 * Try to comment this out madvise to see the memory
+		 * corruption being caught pretty quick.
+		 *
+		 * khugepaged is also inhibited to collapse THP after
+		 * MADV_DONTNEED only after the UFFDIO_REGISTER, so it's
+		 * required to MADV_DONTNEED here.
+		 */
+		uffd_test_ops->release_pages(area_dst);
+
+		uffd_stats_reset(args, nr_cpus);
+
+		/* bounce pass */
+		if (stress(args))
+			return 1;
+
+		/* Clear all the write protections if there is any */
+		if (test_uffdio_wp)
+			wp_range(uffd, (unsigned long)area_dst,
+				 nr_pages * page_size, false);
+
+		/* unregister */
+		if (uffd_unregister(uffd, area_dst, mem_size))
+			err("unregister failure");
+		if (area_dst_alias) {
+			if (uffd_unregister(uffd, area_dst_alias, mem_size))
+				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])
+					err("error area_count %llu %llu %lu\n",
+					    *area_count(area_src, nr),
+					    count_verify[nr], nr);
+
+		/* prepare next bounce */
+		swap(area_src, area_dst);
+
+		swap(area_src_alias, area_dst_alias);
+
+		uffd_stats_report(args, nr_cpus);
+	}
+
+	return 0;
+}
+
+static void set_test_type(const char *type)
+{
+	if (!strcmp(type, "anon")) {
+		test_type = TEST_ANON;
+		uffd_test_ops = &anon_uffd_test_ops;
+	} else if (!strcmp(type, "hugetlb")) {
+		test_type = TEST_HUGETLB;
+		uffd_test_ops = &hugetlb_uffd_test_ops;
+		map_shared = true;
+	} else if (!strcmp(type, "hugetlb-private")) {
+		test_type = TEST_HUGETLB;
+		uffd_test_ops = &hugetlb_uffd_test_ops;
+	} else if (!strcmp(type, "shmem")) {
+		map_shared = true;
+		test_type = TEST_SHMEM;
+		uffd_test_ops = &shmem_uffd_test_ops;
+	} else if (!strcmp(type, "shmem-private")) {
+		test_type = TEST_SHMEM;
+		uffd_test_ops = &shmem_uffd_test_ops;
+	}
+}
+
+static void parse_test_type_arg(const char *raw_type)
+{
+	uint64_t features = UFFD_API_FEATURES;
+
+	set_test_type(raw_type);
+
+	if (!test_type)
+		err("failed to parse test type argument: '%s'", raw_type);
+
+	if (test_type == TEST_HUGETLB)
+		page_size = default_huge_page_size();
+	else
+		page_size = sysconf(_SC_PAGE_SIZE);
+
+	if (!page_size)
+		err("Unable to determine page size");
+	if ((unsigned long) area_count(NULL, 0) + sizeof(unsigned long long) * 2
+	    > page_size)
+		err("Impossible to run this test");
+
+	/*
+	 * Whether we can test certain features depends not just on test type,
+	 * but also on whether or not this particular kernel supports the
+	 * feature.
+	 */
+
+	if (userfaultfd_open(&features))
+		err("Userfaultfd open failed");
+
+	test_uffdio_wp = test_uffdio_wp &&
+		(features & UFFD_FEATURE_PAGEFAULT_FLAG_WP);
+
+	close(uffd);
+	uffd = -1;
+}
+
+static void sigalrm(int sig)
+{
+	if (sig != SIGALRM)
+		abort();
+	test_uffdio_copy_eexist = true;
+	alarm(ALARM_INTERVAL_SECS);
+}
+
+int main(int argc, char **argv)
+{
+	size_t bytes;
+
+	if (argc < 4)
+		usage();
+
+	if (signal(SIGALRM, sigalrm) == SIG_ERR)
+		err("failed to arm SIGALRM");
+	alarm(ALARM_INTERVAL_SECS);
+
+	parse_test_type_arg(argv[1]);
+	bytes = atol(argv[2]) * 1024 * 1024;
+
+	nr_cpus = sysconf(_SC_NPROCESSORS_ONLN);
+
+	nr_pages_per_cpu = bytes / page_size / nr_cpus;
+	if (!nr_pages_per_cpu) {
+		_err("invalid MiB");
+		usage();
+	}
+
+	bounces = atoi(argv[3]);
+	if (bounces <= 0) {
+		_err("invalid bounces");
+		usage();
+	}
+	nr_pages = nr_pages_per_cpu * nr_cpus;
+
+	printf("nr_pages: %lu, nr_pages_per_cpu: %lu\n",
+	       nr_pages, nr_pages_per_cpu);
+	return userfaultfd_stress();
+}
+
+#else /* __NR_userfaultfd */
+
+#warning "missing __NR_userfaultfd definition"
+
+int main(void)
+{
+	printf("skip: Skipping userfaultfd test (missing __NR_userfaultfd)\n");
+	return KSFT_SKIP;
+}
+
+#endif /* __NR_userfaultfd */