[PATCH v3 3/3] selftests/nommu: add nommu mmap and mremap behavior tests

[Hajime Tazaki <thehajime@gmail.com>]

Introduce a kselftest utility to validate memory mapping capabilities
under nommu kernels, aligned with
Documentation/admin-guide/mm/nommu-mmap.rst.

The test implements basic checks into a generic architecture-agnostic
test matrix applicable across nommu targets. It evaluates:

1. MAP_FIXED allocation rejections.
2. Standard MAP_PRIVATE and MAP_ANONYMOUS allocation resilience.
3. Regular file mappings via standard filesystem storage.
4. Block device subsystem mappings (gracefully skipping if node is
   missing).
5. Shared vs Private backing discrepancies under nommu conditions.
6. mremap limits, ensuring non-expandable restrictions behave properly.

Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: David Hildenbrand <david@kernel.org>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: "Liam R. Howlett" <liam@infradead.org>
Cc: Vlastimil Babka <vbabka@kernel.org>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: linux-kselftest@vger.kernel.org
Cc: linux-mm@kvack.org
Cc: linux-um@lists.infradead.org
Closes: https://sashiko.dev/#/patchset/20260825015945.141739-1-thehajime@gmail.com
Assisted-by: Gemini:Pro [AI_Reviewer] [Sashiko_Linter]
Assisted-by: cubic.dev:unspecified
Signed-off-by: Hajime Tazaki <thehajime@gmail.com>

--

v2 => v3
- remove unnecessary modifications
- address Sashiko review

rfc => v2
- prepare a different TARGETS for tests (mm/nommu)
- drop shrink fix tests
- drop mmap /dev/zero tests
- https://lore.kernel.org/linux-mm/20260825015945.141739-3-thehajime@gmail.com/

rfc:
- https://lore.kernel.org/linux-mm/20260813063401.1786548-1-thehajime@gmail.com/
---
 tools/testing/selftests/nommu/Makefile        |   8 +
 tools/testing/selftests/nommu/local.mk        |   7 +
 .../testing/selftests/nommu/nommu_mmap_test.c | 258 +++++++++++++
 .../selftests/nommu/nommu_mremap_test.c       | 362 ++++++++++++++++++
 4 files changed, 635 insertions(+)
 create mode 100644 tools/testing/selftests/nommu/Makefile
 create mode 100644 tools/testing/selftests/nommu/local.mk
 create mode 100644 tools/testing/selftests/nommu/nommu_mmap_test.c
 create mode 100644 tools/testing/selftests/nommu/nommu_mremap_test.c

diff --git a/tools/testing/selftests/nommu/Makefile b/tools/testing/selftests/nommu/Makefile
new file mode 100644
index 000000000000..8e7cd7315c53
--- /dev/null
+++ b/tools/testing/selftests/nommu/Makefile
@@ -0,0 +1,8 @@
+# SPDX-License-Identifier: GPL-2.0
+# Makefile for nommu selftests
+
+TEST_GEN_PROGS += nommu_mmap_test
+TEST_GEN_PROGS += nommu_mremap_test
+
+include ../lib.mk
+include local.mk
diff --git a/tools/testing/selftests/nommu/local.mk b/tools/testing/selftests/nommu/local.mk
new file mode 100644
index 000000000000..0bd1300f00f4
--- /dev/null
+++ b/tools/testing/selftests/nommu/local.mk
@@ -0,0 +1,7 @@
+# detect if users request NOMMU build or not
+# User can set NOMMU to 1 to build/test for NOMMU platforms
+NOMMU ?= 0
+ifeq ($(NOMMU),1)
+CFLAGS += -DNOMMU
+export NOMMU
+endif
diff --git a/tools/testing/selftests/nommu/nommu_mmap_test.c b/tools/testing/selftests/nommu/nommu_mmap_test.c
new file mode 100644
index 000000000000..8d396638da56
--- /dev/null
+++ b/tools/testing/selftests/nommu/nommu_mmap_test.c
@@ -0,0 +1,258 @@
+// SPDX-License-Identifier: GPL-2.0
+#define _GNU_SOURCE
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/mman.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <errno.h>
+#include <string.h>
+#include <limits.h>
+#include "kselftest.h"
+
+#include <sys/vfs.h>
+#ifndef RAMFS_MAGIC
+#define RAMFS_MAGIC 0x858458f6
+#endif
+
+static size_t ps;
+
+struct test_case_t {
+	const char *name;
+	const char *pathname;
+	int open_flags;
+	int mmap_prot;
+	int mmap_flags;
+	int exp_err;
+	int (*resolve_exp_err)(const char *path);
+};
+
+static int get_shm_expected_error(const char *path)
+{
+	struct statfs fs;
+
+	if (statfs(path, &fs) == 0) {
+		if (fs.f_type == RAMFS_MAGIC)
+			return 0; /* ramfs succeed with contiguous memory */
+	}
+	 /* hostfs, etc returns ENODEV due to lack of contiguous allocation */
+	return ENODEV;
+}
+
+static struct test_case_t test_cases[] = {
+	{
+		.name = "anonymous private allocation",
+		.pathname = NULL,
+		.open_flags = O_CREAT | O_RDWR | O_EXCL,
+		.mmap_prot = PROT_READ | PROT_WRITE,
+		.mmap_flags = MAP_ANONYMOUS | MAP_PRIVATE,
+		.exp_err = 0,
+		.resolve_exp_err = NULL,
+	},
+	{
+		.name = "non-anonymous private file mapping (rw-)",
+		.pathname = "/tmp/ksft.nommu-reg-XXXXXX",
+		.open_flags = O_CREAT | O_RDWR | O_EXCL,
+		.mmap_prot = PROT_READ | PROT_WRITE,
+		.mmap_flags = MAP_PRIVATE,
+		.exp_err = 0,
+		.resolve_exp_err = NULL,
+	},
+	{
+		.name = "non-anonymous private file mapping (r--)",
+		.pathname = "/tmp/ksft.nommu-reg-XXXXXX",
+		.open_flags = O_CREAT | O_RDWR | O_EXCL,
+		.mmap_prot = PROT_READ,
+		.mmap_flags = MAP_PRIVATE,
+		.exp_err = 0,
+		.resolve_exp_err = NULL,
+	},
+	{
+		.name = "non-anonymous shared file mapping (rw-)",
+		.pathname = "/tmp/ksft.nommu-shm-XXXXXX",
+		.open_flags = O_CREAT | O_RDWR | O_EXCL,
+		.mmap_prot = PROT_READ | PROT_WRITE,
+		.mmap_flags = MAP_SHARED,
+		.exp_err = 0,
+#ifdef NOMMU
+		.resolve_exp_err = get_shm_expected_error,
+#else
+		.resolve_exp_err = NULL,
+#endif
+	},
+	{
+		.name = "non-anonymous shared file mapping (r--)",
+		.pathname = "/tmp/ksft.nommu-shm-XXXXXX",
+		.open_flags = O_CREAT | O_RDWR | O_EXCL,
+		.mmap_prot = PROT_READ,
+		.mmap_flags = MAP_SHARED,
+		.exp_err = 0,
+#ifdef NOMMU
+		.resolve_exp_err = get_shm_expected_error,
+#else
+		.resolve_exp_err = 0,
+#endif
+	},
+};
+
+static int run_mapping_matrix_test(struct test_case_t *tcase)
+{
+	int fd;
+	void *ptr;
+	char path_buf[PATH_MAX];
+	const char *path = tcase->pathname;
+	int rc = KSFT_PASS;
+	int expected_error;
+
+	ksft_print_msg("[RUN] Testing: %s\n", tcase->name);
+
+	if (tcase->pathname == NULL) {
+		fd = -1;
+	} else if (strstr(tcase->pathname, "XXXXXX")) {
+		strncpy(path_buf, tcase->pathname, sizeof(path_buf) - 1);
+		path_buf[sizeof(path_buf) - 1] = '\0';
+		fd = mkstemp(path_buf);
+		if (fd < 0) {
+			ksft_test_result_skip("Failed to setup temp node: %s\n",
+					      tcase->pathname);
+			return KSFT_SKIP;
+		}
+		if (ftruncate(fd, ps) != 0) {
+			ksft_test_result_fail("ftruncate failed for: %s\n",
+					      tcase->pathname);
+			close(fd);
+			unlink(path_buf);
+			return KSFT_FAIL;
+		}
+		path = path_buf;
+	} else {
+		fd = open(tcase->pathname, tcase->open_flags, 0600);
+		if (fd < 0) {
+			ksft_test_result_skip("Device node not accessible: %s\n",
+				       tcase->pathname);
+			return KSFT_SKIP;
+		}
+	}
+
+	expected_error = tcase->exp_err;
+	if (tcase->resolve_exp_err && fd >= 0)
+		expected_error = tcase->resolve_exp_err(path);
+
+	ptr = mmap(NULL, ps, tcase->mmap_prot, tcase->mmap_flags, fd, 0);
+
+	if (expected_error != 0) {
+		if (ptr != MAP_FAILED) {
+			ksft_test_result_fail("%s: mmap unexpectedly succeeded (exp error %d)\n",
+					      tcase->name, expected_error);
+			munmap(ptr, ps);
+			rc = KSFT_FAIL;
+			goto cleanup;
+		}
+		if (errno != expected_error) {
+			ksft_test_result_fail("%s: mmap failed with %d (%s), but expected %d\n",
+					      tcase->name, errno, strerror(errno), expected_error);
+			rc = KSFT_FAIL;
+			goto cleanup;
+		}
+		ksft_test_result_pass("%s: Correctly rejected with expected error %s(%d)\n",
+				      tcase->name, strerror(expected_error), expected_error);
+		rc = KSFT_PASS;
+		goto cleanup;
+	}
+
+	if (ptr == MAP_FAILED) {
+		ksft_test_result_fail("%s: mmap failed unexpectedly: %s\n",
+				      tcase->name, strerror(errno));
+		rc = KSFT_FAIL;
+		goto cleanup;
+	}
+
+	ksft_test_result_pass("%s: mmap validation successfully passed\n", tcase->name);
+	munmap(ptr, ps);
+
+cleanup:
+	if (fd >= 0) {
+		close(fd);
+		if (tcase->pathname && strstr(tcase->pathname, "XXXXXX"))
+			unlink(path_buf);
+	}
+	return rc;
+}
+
+static int test_map_fixed(void)
+{
+	void *fixed_addr;
+	void *ptr;
+
+	ksft_print_msg("[RUN] Testing MAP_FIXED behavior\n");
+
+	fixed_addr = mmap(NULL, ps, PROT_READ | PROT_WRITE,
+			MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
+	if (fixed_addr == MAP_FAILED) {
+		ksft_test_result_skip("Unable to reserve test address: %s\n",
+				strerror(errno));
+		return KSFT_SKIP;
+	}
+
+	if (munmap(fixed_addr, ps)) {
+		ksft_test_result_fail("Unable to release test address: %s\n",
+				strerror(errno));
+		return KSFT_FAIL;
+	}
+
+	ptr = mmap(fixed_addr, ps, PROT_READ | PROT_WRITE,
+		MAP_PRIVATE | MAP_ANONYMOUS | MAP_FIXED, -1, 0);
+
+#ifdef NOMMU
+	if (ptr == MAP_FAILED && (errno == ENODEV || errno == EINVAL)) {
+		ksft_test_result_pass("MAP_FIXED correctly rejected under nommu\n");
+		return KSFT_PASS;
+	}
+	if (ptr != MAP_FAILED) {
+		ksft_test_result_fail("MAP_FIXED unexpectedly allowed under nommu\n");
+		munmap(ptr, ps);
+		return KSFT_FAIL;
+	}
+	ksft_test_result_fail("MAP_FIXED failed under NOMMU: %s\n",
+			      strerror(errno));
+	return KSFT_FAIL;
+#else
+	if (ptr != MAP_FAILED) {
+		ksft_test_result_pass("MAP_FIXED successfully allocated under MMU\n");
+		munmap(ptr, ps);
+		return KSFT_PASS;
+	}
+	ksft_test_result_fail("MAP_FIXED failed allocation under MMU\n");
+	return KSFT_FAIL;
+#endif
+}
+
+int main(int argc, char **argv)
+{
+	int result = KSFT_PASS;
+	int i, rc;
+
+	ps = sysconf(_SC_PAGESIZE);
+	ksft_print_header();
+	ksft_set_plan(ARRAY_SIZE(test_cases) + 1);
+
+#ifdef NOMMU
+	ksft_print_msg("Running strict MMAP test criteria under nommu architecture\n");
+#else
+	ksft_print_msg("Running MMAP test criteria under MMU architecture\n");
+#endif
+
+	if (test_map_fixed() == KSFT_FAIL)
+		result = KSFT_FAIL;
+
+	for (i = 0; i < (int)ARRAY_SIZE(test_cases); i++) {
+		rc = run_mapping_matrix_test(&test_cases[i]);
+		if (rc == KSFT_FAIL)
+			result = KSFT_FAIL;
+	}
+
+	if (result == KSFT_PASS)
+		ksft_finished();
+
+	ksft_exit_fail();
+}
diff --git a/tools/testing/selftests/nommu/nommu_mremap_test.c b/tools/testing/selftests/nommu/nommu_mremap_test.c
new file mode 100644
index 000000000000..2aaca59085fb
--- /dev/null
+++ b/tools/testing/selftests/nommu/nommu_mremap_test.c
@@ -0,0 +1,362 @@
+// SPDX-License-Identifier: GPL-2.0
+#define _GNU_SOURCE
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/mman.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <errno.h>
+#include <string.h>
+#include <limits.h>
+#include "kselftest.h"
+
+#include <sys/vfs.h>
+#ifndef RAMFS_MAGIC
+#define RAMFS_MAGIC 0x858458f6
+#endif
+
+static size_t ps;
+
+static long get_fs_type(const char *path)
+{
+	struct statfs fs;
+
+	if (statfs(path, &fs) == 0)
+		return fs.f_type;
+
+	return 0;
+}
+
+static void munmap_shrink_test(void)
+{
+	void *addr;
+	int ret;
+
+	/* munmap shrink test */
+	for (int i = 0; i < 4; i++) {
+		addr = mmap(NULL, ps * 4, PROT_READ | PROT_WRITE,
+			    MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
+		if (addr == MAP_FAILED) {
+			ksft_test_result_fail("mmap failed: %s(%d)\n", strerror(errno), errno);
+			return;
+		}
+		ret = munmap((char *)addr + ps * i, ps);
+		if (ret != 0) {
+			ksft_test_result_fail("memory %p isn't unmapped at %p\n",
+					addr, (char *)addr + ps * i);
+			return;
+		}
+
+		if (i == 0) {
+			if (munmap(addr +  ps, ps * 3))
+				goto error;
+		} else if (i == 1) {
+			if (munmap(addr, ps) || munmap(addr + (ps * 2), ps * 2))
+				goto error;
+		} else if (i == 2) {
+			if (munmap(addr, ps * 2) || munmap(addr + (ps * 3), ps))
+				goto error;
+		} else if (i == 3) {
+			if (munmap(addr, ps * 3))
+				goto error;
+		}
+	}
+
+	ksft_test_result_pass("%s success\n", __func__);
+	return;
+error:
+	for (int j = 0; j < 4; j++)
+		munmap((char *)addr + j * ps, ps);
+	ksft_test_result_fail("%s clean up failures\n", __func__);
+}
+
+static size_t page_align(size_t len)
+{
+	return (len + ps - 1) / ps * ps;
+}
+
+static void mremap_shrink_test(void)
+{
+	void *addr, *addr2;
+	size_t current_len;
+	size_t old_len, new_len;
+	struct param {
+		size_t old;
+		size_t new;
+	} params[] = {
+		/* should not happen any shrink */
+		{ .old = ps * 4 - 1, .new = ps * 4 - 2 },
+		/* should not happen any shrink */
+		{ .old = ps * 4 - 1, .new = ps * 4 },
+		{ .old = ps * 4, .new = ps * 2 },
+		/* should not happen any shrink */
+		{ .old = ps * 2, .new = ps * 2 - 2 },
+		{ .old = ps * 2 - 2, .new = ps * 1 },
+	};
+
+	/* mremap shrink test */
+	current_len = page_align(ps * 4 - 1);
+	addr = mmap(NULL, ps * 4 - 1, PROT_READ | PROT_WRITE,
+		    MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
+	if (addr == MAP_FAILED) {
+		ksft_test_result_fail("mmap failed: %s(%d)\n", strerror(errno), errno);
+		return;
+	}
+
+	for (int i = 0; i < ARRAY_SIZE(params); i++) {
+		old_len = params[i].old;
+		new_len = params[i].new;
+		current_len = page_align(new_len);
+		addr2 = mremap(addr, old_len, new_len, MREMAP_MAYMOVE);
+		if (addr2 == MAP_FAILED) {
+			ksft_test_result_fail("memory %p isn't remapped at %p\n", addr, addr2);
+			munmap(addr, page_align(old_len));
+			return;
+		}
+
+		addr = addr2;
+	}
+
+	if (munmap(addr, current_len)) {
+		ksft_test_result_fail("%s cleanup failed: %s\n",
+				      __func__, strerror(errno));
+		return;
+	}
+	ksft_test_result_pass("%s success\n", __func__);
+}
+
+static int get_shared_writable_file_expected_error(const char *path)
+{
+	if (get_fs_type(path) == RAMFS_MAGIC)
+		return EPERM; /* ramfs failed */
+
+	return 0;
+}
+
+struct mremap_case_t {
+	const char *name;
+	const char *pathname;
+	int open_flags;
+	int mmap_prot;
+	int mmap_flags;
+	int exp_err;
+	int (*resolve_exp_err)(const char *path);
+	unsigned int old_pages;
+	unsigned int new_pages;
+};
+
+static struct mremap_case_t mremap_cases[] = {
+	{
+		.name = "anonymous shrink (r--)",
+		.pathname = NULL,
+		.open_flags = O_CREAT | O_RDWR | O_EXCL,
+		.mmap_prot = PROT_READ,
+		.mmap_flags = MAP_ANONYMOUS | MAP_PRIVATE,
+		.exp_err = 0,
+		.resolve_exp_err = 0,
+	},
+	{
+		.name = "shared file shrink (r--)",
+		.pathname = "/tmp/ksft.nommu-remap-XXXXXX",
+		.open_flags = O_CREAT | O_RDWR | O_EXCL,
+		.mmap_prot = PROT_READ,
+		.mmap_flags = MAP_SHARED,
+		.exp_err = 0,
+#ifdef NOMMU
+		.resolve_exp_err = get_shared_writable_file_expected_error,
+#else
+		.resolve_exp_err = 0,
+#endif
+	},
+	{
+		.name = "private file unchanged length (r-)",
+		.pathname = "/tmp/ksft.nommu-remap-XXXXXX",
+		.open_flags = O_CREAT | O_RDWR | O_EXCL,
+		.mmap_prot = PROT_READ,
+		.mmap_flags = MAP_PRIVATE,
+#ifdef NOMMU
+		.exp_err = EPERM,
+#else
+		.exp_err = 0,
+#endif
+		.resolve_exp_err = 0,
+		.old_pages = 4,
+		.new_pages = 4,
+	},
+	{
+		.name = "private file unchanged length (rw-)",
+		.pathname = "/tmp/ksft.nommu-remap-XXXXXX",
+		.open_flags = O_CREAT | O_RDWR | O_EXCL,
+		.mmap_prot = PROT_READ | PROT_WRITE,
+		.mmap_flags = MAP_PRIVATE,
+		.exp_err = 0,
+		.resolve_exp_err = 0,
+		.old_pages = 4,
+		.new_pages = 4,
+	},
+	{
+		.name = "private file growth (r-)",
+		.pathname = "/tmp/ksft.nommu-remap-XXXXXX",
+		.open_flags = O_CREAT | O_RDWR | O_EXCL,
+		.mmap_prot = PROT_READ,
+		.mmap_flags = MAP_PRIVATE,
+#ifdef NOMMU
+		.exp_err = EPERM,
+#else
+		.exp_err = 0,
+#endif
+		.resolve_exp_err = 0,
+		.old_pages = 4,
+		.new_pages = 8,
+	},
+	{
+		.name = "private file growth (rw-)",
+		.pathname = "/tmp/ksft.nommu-remap-XXXXXX",
+		.open_flags = O_CREAT | O_RDWR | O_EXCL,
+		.mmap_prot = PROT_READ | PROT_WRITE,
+		.mmap_flags = MAP_PRIVATE,
+#ifdef NOMMU
+		.exp_err = ENOMEM,
+#else
+		.exp_err = 0,
+#endif
+		.resolve_exp_err = 0,
+		.old_pages = 4,
+		.new_pages = 8,
+	},
+};
+
+static int run_mremap_test(struct mremap_case_t *tcase)
+{
+	int fd = -1;
+	void *addr, *addr2;
+	char pb[PATH_MAX];
+	const char *path = tcase->pathname;
+	int rc = KSFT_PASS;
+	int expected_error;
+	unsigned int old_pages = tcase->old_pages ?: 4;
+	unsigned int new_pages = tcase->new_pages ?: 2;
+	unsigned int file_pages = old_pages > new_pages ?
+				  old_pages : new_pages;
+
+	ksft_print_msg("[RUN] Testing mremap: %s\n", tcase->name);
+
+	if (tcase->pathname && strstr(tcase->pathname, "XXXXXX")) {
+		strncpy(pb, tcase->pathname, sizeof(pb) - 1);
+		pb[sizeof(pb) - 1] = '\0';
+		fd = mkstemp(pb);
+		if (fd < 0) {
+			ksft_test_result_skip("Failed to setup file backing\n");
+			return KSFT_SKIP;
+		}
+		if (ftruncate(fd, ps * file_pages) != 0) {
+			ksft_test_result_fail("Failed to setup file backing\n");
+			close(fd);
+			unlink(pb);
+			return KSFT_FAIL;
+		}
+
+#ifdef NOMMU
+		if ((tcase->mmap_flags & MAP_SHARED) && get_fs_type(pb) != RAMFS_MAGIC) {
+			ksft_test_result_skip("Skip the test under non-ramfs filesystem (%s)\n",
+					      pb);
+			close(fd);
+			unlink(pb);
+			return KSFT_SKIP;
+		}
+#endif
+		path = pb;
+	} else if (tcase->pathname) {
+		fd = open(tcase->pathname, tcase->open_flags, 0600);
+		if (fd < 0) {
+			ksft_test_result_skip("Backing node not accessible\n");
+			return KSFT_SKIP;
+		}
+
+#ifdef NOMMU
+		if ((tcase->mmap_flags & MAP_SHARED) &&
+		    get_fs_type(tcase->pathname) != RAMFS_MAGIC) {
+			ksft_test_result_skip("Skip the test under non-ramfs filesystem (%s)\n",
+					      tcase->pathname);
+			close(fd);
+			return KSFT_SKIP;
+		}
+#endif
+	}
+
+	addr = mmap(NULL, ps * old_pages, tcase->mmap_prot,
+		    tcase->mmap_flags, fd, 0);
+	if (addr == MAP_FAILED) {
+		ksft_print_msg("mmap mapping failed %s(%d)\n", strerror(errno), errno);
+		rc = KSFT_FAIL;
+		goto out;
+	}
+
+	expected_error = tcase->exp_err;
+	if (tcase->resolve_exp_err && fd >= 0)
+		expected_error = tcase->resolve_exp_err(path);
+
+	addr2 = mremap(addr, ps * old_pages, ps * new_pages,
+		       MREMAP_MAYMOVE);
+
+	if (expected_error != 0) {
+		if (addr2 != MAP_FAILED) {
+			ksft_print_msg("Expected error %d, but mremap unexpectedly succeeded\n",
+				       expected_error);
+			rc = KSFT_FAIL;
+		} else if (errno != expected_error) {
+			ksft_print_msg("Expected error %d, got %s(%d)\n",
+				       expected_error, strerror(errno), errno);
+			rc = KSFT_FAIL;
+		} else {
+			ksft_print_msg("%s/%s: Handled expected error path (errno=%d)\n",
+				       __func__, tcase->name, expected_error);
+		}
+	} else if (addr2 == MAP_FAILED) {
+		ksft_print_msg("mremap shrink failed unexpectedly: %s\n",
+			       strerror(errno));
+		rc = KSFT_FAIL;
+	} else {
+		ksft_print_msg("%s/%s step successful\n", __func__, tcase->name);
+	}
+
+	/* clean up */
+	if (munmap(addr2 == MAP_FAILED ? addr : addr2,
+		   addr2 == MAP_FAILED ? ps * old_pages : ps * new_pages)) {
+		ksft_print_msg("munmap failed: %s\n", strerror(errno));
+		rc = KSFT_FAIL;
+	}
+
+out:
+	if (fd >= 0) {
+		close(fd);
+		if (tcase->pathname && strstr(tcase->pathname, "XXXXXX"))
+			unlink(pb);
+	}
+
+	ksft_test_result_report(rc, "%s:%s\n", __func__, tcase->name);
+	return rc;
+}
+
+int main(int argc, char **argv)
+{
+	int res = KSFT_PASS;
+	int i;
+
+	ps = sysconf(_SC_PAGESIZE);
+	ksft_print_header();
+	ksft_set_plan(ARRAY_SIZE(mremap_cases) + 2);
+
+	munmap_shrink_test();
+	mremap_shrink_test();
+
+	for (i = 0; i < (int)ARRAY_SIZE(mremap_cases); i++) {
+		if (run_mremap_test(&mremap_cases[i]) == KSFT_FAIL)
+			res = KSFT_FAIL;
+	}
+
+	if (res == KSFT_PASS)
+		ksft_finished();
+
+	ksft_exit_fail();
+}
-- 
2.43.0