Tests/Kernel: Add tests for verifying proper loop device support

Author: https://github.com/supercomputer7
Commit: https://github.com/SerenityOS/serenity/commit/ec6e7077fe
Pull-request: https://github.com/SerenityOS/serenity/pull/23138
Reviewed-by: https://github.com/ADKaster ✅
Reviewed-by: https://github.com/Hendiadyoin1
Reviewed-by: https://github.com/gmta

Meta/build-root-filesystem.sh

@@ -110,6 +110,10 @@ if [ -f mnt/usr/Tests/Kernel/TestProcFSWrite ]; then
     chown 0:0 mnt/usr/Tests/Kernel/TestProcFSWrite
     chmod 4755 mnt/usr/Tests/Kernel/TestProcFSWrite
 fi
+if [ -f mnt/usr/Tests/Kernel/TestLoopDevice ]; then
+    chown 0:0 mnt/usr/Tests/Kernel/TestLoopDevice
+    chmod 4755 mnt/usr/Tests/Kernel/TestLoopDevice
+fi
 
 if [ -f mnt/res/kernel.map ]; then
     chmod 0400 mnt/res/kernel.map

Tests/Kernel/CMakeLists.txt

@@ -50,6 +50,7 @@ set(LIBTEST_BASED_SOURCES
     TestKernelFilePermissions.cpp
     TestKernelPledge.cpp
     TestKernelUnveil.cpp
+    TestLoopDevice.cpp
     TestMemoryDeviceMmap.cpp
     TestMunMap.cpp
     TestProcFS.cpp

Tests/Kernel/TestLoopDevice.cpp

@@ -0,0 +1,55 @@
+/*
+ * Copyright (c) 2024, Liav A. <liavalb@hotmail.co.il>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <AK/ByteString.h>
+#include <AK/StringView.h>
+#include <Kernel/API/Ioctl.h>
+#include <LibTest/TestCase.h>
+#include <fcntl.h>
+#include <sys/ioctl.h>
+#include <unistd.h>
+
+static int open_loop_device(int loop_device_index)
+{
+    auto loop_device_path = ByteString::formatted("/dev/loop/{}", loop_device_index);
+    return open(loop_device_path.view().characters_without_null_termination(), O_RDONLY);
+}
+
+TEST_CASE(create_attach_and_destory_loop_device)
+{
+    constexpr char const* test_path = "/tmp/create_attach_and_destory_loop_device_test";
+
+    int devctl_fd = open("/dev/devctl", O_RDONLY);
+    VERIFY(devctl_fd >= 0);
+    auto cleanup_devctl_fd_guard = ScopeGuard([&] {
+        close(devctl_fd);
+    });
+
+    u8 buf[0x1000];
+    memset(buf, 0, sizeof(buf));
+    int fd = open(test_path, O_RDWR | O_CREAT, 0644);
+    VERIFY(fd >= 0);
+    auto cleanup_fd_guard = ScopeGuard([&] {
+        close(fd);
+        unlink(test_path);
+    });
+    auto rc = write(fd, buf, sizeof(buf));
+    VERIFY(rc == sizeof(buf));
+
+    int value = fd;
+    auto create_result = ioctl(devctl_fd, DEVCTL_CREATE_LOOP_DEVICE, &value);
+    EXPECT_EQ(create_result, 0);
+
+    auto loop_device_index = value;
+    auto loop_device_fd_or_error = open_loop_device(loop_device_index);
+    EXPECT(loop_device_fd_or_error >= 0);
+    auto cleanup_loop_device_fd_guard = ScopeGuard([&] {
+        close(loop_device_fd_or_error);
+    });
+
+    auto destroy_result = ioctl(devctl_fd, DEVCTL_DESTROY_LOOP_DEVICE, &loop_device_index);
+    EXPECT_EQ(destroy_result, 0);
+}