[LTP] [PATCH v3 6/7] mremap08: Extract test from mremap05

[Andrea Cervesato]

From: Andrea Cervesato <andrea.cervesato@suse.com>

Extract a new test from mremap05 that verifies the behavior of the
MREMAP_FIXED flag when:

- MREMAP_FIXED | MREMAP_MAYMOVE can move a mapping to a new, free
  address, preserving its content.
- MREMAP_FIXED | MREMAP_MAYMOVE unmaps a previously existing mapping
  at the target address range and replaces it with the moved mapping.

Reviewed-by: Cyril Hrubis <chrubis@suse.cz>
Signed-off-by: Andrea Cervesato <andrea.cervesato@suse.com>
---
 runtest/syscalls                            |   1 +
 testcases/kernel/syscalls/mremap/.gitignore |   1 +
 testcases/kernel/syscalls/mremap/mremap08.c | 127 ++++++++++++++++++++++++++++
 3 files changed, 129 insertions(+)

diff --git a/runtest/syscalls b/runtest/syscalls
index b024d4c43..ede795a48 100644
--- a/runtest/syscalls
+++ b/runtest/syscalls
@@ -946,6 +946,7 @@ mremap04 mremap04
 mremap05 mremap05
 mremap06 mremap06
 mremap07 mremap07
+mremap08 mremap08
 
 mseal01 mseal01
 mseal02 mseal02
diff --git a/testcases/kernel/syscalls/mremap/.gitignore b/testcases/kernel/syscalls/mremap/.gitignore
index 292899e03..dd4bf4e8e 100644
--- a/testcases/kernel/syscalls/mremap/.gitignore
+++ b/testcases/kernel/syscalls/mremap/.gitignore
@@ -5,3 +5,4 @@
 /mremap05
 /mremap06
 /mremap07
+/mremap08
diff --git a/testcases/kernel/syscalls/mremap/mremap08.c b/testcases/kernel/syscalls/mremap/mremap08.c
new file mode 100644
index 000000000..a2c589447
--- /dev/null
+++ b/testcases/kernel/syscalls/mremap/mremap08.c
@@ -0,0 +1,127 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (c) 2026 Linux Test Project
+ */
+
+/*\
+ * Verify the behavior of the ``MREMAP_FIXED`` flag of :manpage:`mremap(2)`:
+ *
+ * - ``MREMAP_FIXED | MREMAP_MAYMOVE`` can move a mapping to a new, free
+ *   address, preserving its content.
+ * - ``MREMAP_FIXED | MREMAP_MAYMOVE`` unmaps a previously existing mapping at
+ *   the target address range and replaces it with the moved mapping.
+ */
+
+#define _GNU_SOURCE
+#include <sys/mman.h>
+#include "tst_test.h"
+
+static int pagesize;
+
+static struct tcase {
+	size_t old_pages;
+	size_t new_pages;
+	int flags;
+	int free_dst;
+	const char *msg;
+} tcases[] = {
+	{
+		.old_pages = 1,
+		.new_pages = 1,
+		.flags = MREMAP_FIXED | MREMAP_MAYMOVE,
+		.free_dst = 1,
+		.msg = "move mapping to free address",
+	},
+	{
+		.old_pages = 1,
+		.new_pages = 1,
+		.flags = MREMAP_FIXED | MREMAP_MAYMOVE,
+		.free_dst = 0,
+		.msg = "move mapping onto an occupied address",
+	},
+};
+
+static void *get_test_area(size_t size, int free_area)
+{
+	void *p;
+
+	p = SAFE_MMAP(NULL, size, PROT_READ | PROT_WRITE,
+		      MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
+
+	if (free_area)
+		SAFE_MUNMAP(p, size);
+
+	return p;
+}
+
+static void setup(void)
+{
+	pagesize = getpagesize();
+}
+
+static void fill_pattern(char *addr, size_t pages, char *new_addr, int free_dst)
+{
+	size_t i;
+
+	for (i = 0; i < pages; i++)
+		addr[i * pagesize] = (char)(0x1 + i);
+
+	if (!free_dst)
+		*new_addr = 0x7f;
+}
+
+static int check_pattern(char *addr, size_t pages)
+{
+	size_t i;
+
+	for (i = 0; i < pages; i++) {
+		char got = addr[i * pagesize];
+		char exp = (char)(0x1 + i);
+
+		if (got != exp)
+			return 1;
+	}
+
+	return 0;
+}
+
+static void run(unsigned int n)
+{
+	struct tcase *tc = &tcases[n];
+	char *old_address;
+	char *new_address;
+	char *ret;
+	size_t old_size = tc->old_pages * pagesize;
+	size_t new_size = tc->new_pages * pagesize;
+
+	old_address = get_test_area(old_size, 0);
+	new_address = get_test_area(new_size, tc->free_dst);
+
+	fill_pattern(old_address, tc->old_pages, new_address, tc->free_dst);
+
+	TESTPTR(mremap(old_address, old_size, new_size, tc->flags, new_address));
+	ret = TST_RET_PTR;
+
+	if (ret == MAP_FAILED) {
+		tst_res(TFAIL | TTERRNO, "%s failed", tc->msg);
+		SAFE_MUNMAP(old_address, old_size);
+		if (!tc->free_dst)
+			SAFE_MUNMAP(new_address, new_size);
+		return;
+	}
+
+	if (ret != new_address)
+		tst_res(TFAIL, "%s: ret %p, expected %p", tc->msg, ret, new_address);
+	else if (check_pattern(ret, tc->new_pages))
+		tst_res(TFAIL, "%s: pattern mismatch", tc->msg);
+	else
+		tst_res(TPASS, "%s", tc->msg);
+
+	SAFE_MUNMAP(ret, new_size);
+}
+
+static struct tst_test test = {
+	.setup = setup,
+	.test = run,
+	.tcnt = ARRAY_SIZE(tcases),
+};

-- 
2.51.0