Tests: Validate unmapping 0x0 doesn't crash the Kernel

Previously unmapping any offset starting at 0x0 would assert in the
kernel, add a regression test to validate the fix.

Co-authored-by: Federico Guerinoni <guerinoni.federico@gmail.com>

1 files changed, 17 insertions, 0 deletions

diff --git a/Tests/Kernel/TestMunMap.cpp b/Tests/Kernel/TestMunMap.cpp
new file mode 100644
index 0000000000..206c7c3556
--- /dev/null
+++ b/Tests/Kernel/TestMunMap.cpp
@@ -0,0 +1,17 @@
+/*
+ * Copyright (c) 2021, Brian Gianforcaro <bgianf@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <LibTest/TestCase.h>
+#include <errno.h>
+#include <sys/mman.h>
+
+TEST_CASE(munmap_zero_page)
+{
+    // munmap of the unmapped zero page should always fail.
+    auto res = munmap(0x0, 0xF);
+    EXPECT_EQ(res, -1);
+    EXPECT_EQ(errno, EINVAL);
+}