[RFC PATCH 2/2] selftests/kskm: Introduce SKSM basic test

[Mathieu Desnoyers <mathieu.desnoyers@efficios.com>]

Introduce a basic selftest for SKSM. See ./basic_test -h for
options.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Olivier Dion <odion@efficios.com>
Cc: linux-mm@kvack.org
---
 tools/testing/selftests/sksm/.gitignore   |   2 +
 tools/testing/selftests/sksm/Makefile     |  14 ++
 tools/testing/selftests/sksm/basic_test.c | 217 ++++++++++++++++++++++
 3 files changed, 233 insertions(+)
 create mode 100644 tools/testing/selftests/sksm/.gitignore
 create mode 100644 tools/testing/selftests/sksm/Makefile
 create mode 100644 tools/testing/selftests/sksm/basic_test.c

diff --git a/tools/testing/selftests/sksm/.gitignore b/tools/testing/selftests/sksm/.gitignore
new file mode 100644
index 000000000000..0f5b0baa91e7
--- /dev/null
+++ b/tools/testing/selftests/sksm/.gitignore
@@ -0,0 +1,2 @@
+# SPDX-License-Identifier: GPL-2.0-only
+basic_test
diff --git a/tools/testing/selftests/sksm/Makefile b/tools/testing/selftests/sksm/Makefile
new file mode 100644
index 000000000000..ec1a10783bda
--- /dev/null
+++ b/tools/testing/selftests/sksm/Makefile
@@ -0,0 +1,14 @@
+# SPDX-License-Identifier: GPL-2.0+ OR MIT
+
+top_srcdir = ../../../..
+
+CFLAGS += -O2 -Wall -g -I./ $(KHDR_INCLUDES) -L$(OUTPUT) -Wl,-rpath=./ \
+	  $(CLANG_FLAGS) -I$(top_srcdir)/tools/include
+LDLIBS += -lpthread
+
+TEST_GEN_PROGS = basic_test
+
+include ../lib.mk
+
+$(OUTPUT)/%: %.c
+	$(CC) $(CFLAGS) $< $(LDLIBS) -o $@
diff --git a/tools/testing/selftests/sksm/basic_test.c b/tools/testing/selftests/sksm/basic_test.c
new file mode 100644
index 000000000000..1a7571a999d2
--- /dev/null
+++ b/tools/testing/selftests/sksm/basic_test.c
@@ -0,0 +1,217 @@
+// SPDX-License-Identifier: LGPL-2.1
+/*
+ * Basic test for SKSM.
+ */
+
+#include <stdlib.h>
+#include <sys/mman.h>
+#include <stdio.h>
+#include <errno.h>
+#include <string.h>
+#include <unistd.h>
+#include <poll.h>
+
+#ifndef MADV_MERGE
+#define MADV_MERGE	26
+#endif
+
+#define PAGE_SIZE	4096
+
+#define WRITE_ONCE(x, val) ((*(volatile typeof(x) *) &(x)) = (val))
+
+static int opt_stop_at = 0, opt_pause = 0;
+
+struct test_page {
+	char array[PAGE_SIZE] __attribute__((aligned(PAGE_SIZE)));
+};
+
+struct test_page2 {
+	char array[2 * PAGE_SIZE] __attribute__((aligned(PAGE_SIZE)));
+};
+
+/* identical to zero page. */
+static struct test_page zero;
+
+/* a1 and a2 are identical. */
+static struct test_page a1 = {
+	.array[0] = 0x42,
+	.array[1] = 0x42,
+};
+
+static struct test_page a2 = {
+	.array[0] = 0x42,
+	.array[1] = 0x42,
+};
+
+/* b1 and b2 are identical. */
+static struct test_page2 b1 = {
+	.array[0] = 0x43,
+	.array[1] = 0x43,
+	.array[PAGE_SIZE] = 0x44,
+	.array[PAGE_SIZE + 1] = 0x44,
+};
+
+static struct test_page2 b2 = {
+	.array[0] = 0x43,
+	.array[1] = 0x43,
+	.array[PAGE_SIZE] = 0x44,
+	.array[PAGE_SIZE + 1] = 0x44,
+};
+
+static void touch_pages(void *p, size_t len)
+{
+	size_t i;
+
+	for (i = 0; i < len; i += PAGE_SIZE)
+		WRITE_ONCE(((char *)p)[i], ((char *)p)[i]);
+}
+
+static void test_step(char step)
+{
+	printf("\nTest step: <%c>\n", step);
+	if (opt_pause) {
+		printf("Press ENTER to continue...\n");
+		getchar();
+	}
+	if (opt_stop_at == step) {
+		poll(NULL, 0, -1);
+		exit(0);
+	}
+}
+
+static void show_usage(int argc, char **argv)
+{
+	printf("Usage : %s <OPTIONS>\n",
+		argv[0]);
+	printf("OPTIONS:\n");
+	printf("	[-s stop_at] Stop test at step A, B, C, D, E, or F and wait forever.\n");
+	printf("	[-p] Pause test between steps (await newline from the console).\n");
+	printf("	[-h] Show this help.\n");
+	printf("\n");
+}
+
+int main(int argc, char **argv)
+{
+	int i;
+
+	for (i = 1; i < argc; i++) {
+		if (argv[i][0] != '-')
+			continue;
+		switch (argv[i][1]) {
+		case 's':
+			if (argc < i + 2) {
+				show_usage(argc, argv);
+				return -1;
+			}
+			opt_stop_at = *argv[i + 1];
+			switch (opt_stop_at) {
+			case 'A':
+			case 'B':
+			case 'C':
+			case 'D':
+			case 'E':
+			case 'F':
+				break;
+			default:
+				show_usage(argc, argv);
+				return -1;
+			}
+			i++;
+			break;
+		case 'p':
+			opt_pause = 1;
+			i++;
+			break;
+		case 'h':
+			show_usage(argc, argv);
+			return 0;
+		default:
+			show_usage(argc, argv);
+			return -1;
+		}
+	}
+
+
+	printf("PID: %d\n", getpid());
+	printf("Shared mapping (write-protected)\n");
+
+	test_step('A');
+
+	printf("madvise MADV_MERGE a1\n");
+	if (madvise(&a1, sizeof(a1), MADV_MERGE))
+		goto error;
+	printf("madvise MADV_MERGE a2\n");
+	if (madvise(&a2, sizeof(a2), MADV_MERGE))
+		goto error;
+	printf("madvise MADV_MERGE b1\n");
+	if (madvise(&b1, sizeof(b1), MADV_MERGE))
+		goto error;
+	printf("madvise MADV_MERGE b2\n");
+	if (madvise(&b2, sizeof(b2), MADV_MERGE))
+		goto error;
+	printf("madvise MADV_MERGE zero\n");
+	if (madvise(&zero, sizeof(zero), MADV_MERGE))
+		goto error;
+
+	test_step('B');
+
+	printf("Trigger COW\n");
+	touch_pages(&zero, sizeof(zero));
+	touch_pages(&a1, sizeof(a1));
+	touch_pages(&a2, sizeof(a2));
+	touch_pages(&b1, sizeof(b1));
+	touch_pages(&b2, sizeof(b2));
+
+	test_step('C');
+
+	printf("madvise MADV_MERGE a1\n");
+	if (madvise(&a1, sizeof(a1), MADV_MERGE))
+		goto error;
+	printf("madvise MADV_MERGE a2\n");
+	if (madvise(&a2, sizeof(a2), MADV_MERGE))
+		goto error;
+	printf("madvise MADV_MERGE b1\n");
+	if (madvise(&b1, sizeof(b1), MADV_MERGE))
+		goto error;
+	printf("madvise MADV_MERGE b2\n");
+	if (madvise(&b2, sizeof(b2), MADV_MERGE))
+		goto error;
+	printf("madvise MADV_MERGE zero\n");
+	if (madvise(&zero, sizeof(zero), MADV_MERGE))
+		goto error;
+
+	test_step('D');
+
+	printf("Trigger COW\n");
+	touch_pages(&zero, sizeof(zero));
+	touch_pages(&a1, sizeof(a1));
+	touch_pages(&a2, sizeof(a2));
+	touch_pages(&b1, sizeof(b1));
+	touch_pages(&b2, sizeof(b2));
+
+	test_step('E');
+
+	printf("madvise MADV_MERGE a1\n");
+	if (madvise(&a1, sizeof(a1), MADV_MERGE))
+		goto error;
+	printf("madvise MADV_MERGE a2\n");
+	if (madvise(&a2, sizeof(a2), MADV_MERGE))
+		goto error;
+	printf("madvise MADV_MERGE b1\n");
+	if (madvise(&b1, sizeof(b1), MADV_MERGE))
+		goto error;
+	printf("madvise MADV_MERGE b2\n");
+	if (madvise(&b2, sizeof(b2), MADV_MERGE))
+		goto error;
+	printf("madvise MADV_MERGE zero\n");
+	if (madvise(&zero, sizeof(zero), MADV_MERGE))
+		goto error;
+
+	test_step('F');
+
+	return 0;
+
+error:
+	perror("madvise");
+	return -1;
+}
-- 
2.39.5