[PATCH] selftests/vm: Add tests validating mremap mirror functionality

[Anshuman Khandual]

This adds two tests to validate mirror functionality with mremap()
system call on shared and private anon mappings. After the commit
dba58d3b8c5 ("mm/mremap: fail map duplication attempts for private
mappings"), any attempt to mirror private anon mapping will fail.

Suggested-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Signed-off-by: Anshuman Khandual <khandual@xxxxxxxxxxxxxxxxxx>
Reviewed-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
---
Changes in V4:

- Folded these two test files into just one as per Mike
- Did some renaming of functions, cleans ups etc

Changes in V3: (https://patchwork.kernel.org/patch/10013469/)

- Fail any attempts to mirror an existing anon private mapping
- Updated run_vmtests to include these new mremap tests
- Updated the commit message

Changes in V2: (https://patchwork.kernel.org/patch/9861259/)

- Added a test for private anon mappings
- Used sysconf(_SC_PAGESIZE) instead of hard coding page size
- Used MREMAP_MAYMOVE instead of hard coding the flag value 1

Original V1: (https://patchwork.kernel.org/patch/9854415/)

 tools/testing/selftests/vm/Makefile        |  1 +
 tools/testing/selftests/vm/mremap_mirror.c | 96 ++++++++++++++++++++++++++++++
 tools/testing/selftests/vm/run_vmtests     | 10 ++++
 3 files changed, 107 insertions(+)
 create mode 100644 tools/testing/selftests/vm/mremap_mirror.c

diff --git a/tools/testing/selftests/vm/Makefile b/tools/testing/selftests/vm/Makefile
index cbb29e4..27f1967 100644
--- a/tools/testing/selftests/vm/Makefile
+++ b/tools/testing/selftests/vm/Makefile
@@ -17,6 +17,7 @@ TEST_GEN_FILES += transhuge-stress
 TEST_GEN_FILES += userfaultfd
 TEST_GEN_FILES += mlock-random-test
 TEST_GEN_FILES += virtual_address_range
+TEST_GEN_FILES += mremap_mirror
 
 TEST_PROGS := run_vmtests
 
diff --git a/tools/testing/selftests/vm/mremap_mirror.c b/tools/testing/selftests/vm/mremap_mirror.c
new file mode 100644
index 0000000..41cdba5
--- /dev/null
+++ b/tools/testing/selftests/vm/mremap_mirror.c
@@ -0,0 +1,96 @@
+/*
+ * Test to verify mirror functionality with mremap() system
+ * call for shared and private anon mappings. In shared anon
+ * mapping case, the 'mirrored' buffer will match element to
+ * element with that of the original one. But any attempts
+ * to create a mirror buffer for an anon private one should
+ * just fail.
+ *
+ * Copyright (C) 2017 Anshuman Khandual, IBM Corporation
+ *
+ * Licensed under GPL V2
+ */
+#define _GNU_SOURCE
+#include <stdio.h>
+#include <string.h>
+#include <unistd.h>
+#include <errno.h>
+#include <sys/mman.h>
+#include <sys/time.h>
+
+#define PATTERN		0xbe
+#define NR_PAGES	10
+
+int test_mirror_shared(char *old, char *new, unsigned long size)
+{
+	unsigned long i;
+
+	for (i = 0; i < size; i++) {
+		if (new[i] != old[i]) {
+			printf("Mismatch at new[%lu] expected \
+				%d received %d\n", i, old[i], new[i]);
+			return 1;
+		}
+	}
+	return 0;
+}
+
+int mirror_anon_shared(unsigned long alloc_size)
+{
+	char *ptr, *mirror_ptr;
+
+	ptr = mmap(NULL, alloc_size, PROT_READ | PROT_WRITE,
+			MAP_SHARED | MAP_ANONYMOUS, -1, 0);
+	if (ptr == MAP_FAILED) {
+		perror("map() failed");
+		return -1;
+	}
+	memset(ptr, PATTERN, alloc_size);
+
+	mirror_ptr =  (char *) mremap(ptr, 0, alloc_size, MREMAP_MAYMOVE);
+	if (mirror_ptr == MAP_FAILED) {
+		perror("mremap() failed");
+		return -1;
+	}
+
+	if (test_mirror_shared(ptr, mirror_ptr, alloc_size))
+		return 1;
+
+	return 0;
+}
+
+int  mirror_anon_private(unsigned long alloc_size)
+{
+	char *ptr, *mirror_ptr;
+
+	ptr = mmap(NULL, alloc_size, PROT_READ | PROT_WRITE,
+			MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
+	if (ptr == MAP_FAILED) {
+		perror("map() failed");
+		return -1;
+	}
+	memset(ptr, PATTERN, alloc_size);
+
+	mirror_ptr =  (char *) mremap(ptr, 0, alloc_size, MREMAP_MAYMOVE);
+	if (mirror_ptr == MAP_FAILED)
+		return 0;
+
+	printf("Mirror attempt on private anon mapping should have failed\n");
+	return 1;
+}
+
+int main(int argc, char *argv[])
+{
+	unsigned long alloc_size;
+	int ret;
+
+	alloc_size = sysconf(_SC_PAGESIZE) * NR_PAGES;
+	ret = mirror_anon_private(alloc_size);
+	if (ret)
+		return ret;
+
+	ret = mirror_anon_shared(alloc_size);
+	if (ret)
+		return ret;
+	return 0;
+}
diff --git a/tools/testing/selftests/vm/run_vmtests b/tools/testing/selftests/vm/run_vmtests
index 07548a1..7214aa2 100755
--- a/tools/testing/selftests/vm/run_vmtests
+++ b/tools/testing/selftests/vm/run_vmtests
@@ -176,4 +176,14 @@ else
 	echo "[PASS]"
 fi
 
+echo "-----------------------------"
+echo "mremap_mirror"
+echo "-----------------------------"
+./mremap_mirror
+if [ $? -ne 0 ]; then
+	echo "[FAIL]"
+	exitcode=1
+else
+	echo "[PASS]"
+fi
 exit $exitcode
-- 
1.8.5.2