From 6d65da93e3c5d9c934dc5d4ae03b95d7609b2198 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Herv=C3=A9=20Poussineau?= <hpoussin@reactos.org>
Date: Tue, 13 Sep 2022 23:46:04 +0200
Subject: [PATCH] [FS_REC] Add FATX recognizer

CORE-16373
---
 drivers/filesystems/fs_rec/CMakeLists.txt |   1 +
 drivers/filesystems/fs_rec/fatx.c         | 130 ++++++++++++++++++++++
 drivers/filesystems/fs_rec/fs_rec.c       |  17 +++
 drivers/filesystems/fs_rec/fs_rec.h       |   8 ++
 4 files changed, 156 insertions(+)
 create mode 100644 drivers/filesystems/fs_rec/fatx.c

diff --git a/drivers/filesystems/fs_rec/CMakeLists.txt b/drivers/filesystems/fs_rec/CMakeLists.txt
index 2d309ef7447..c231d3d378d 100644
--- a/drivers/filesystems/fs_rec/CMakeLists.txt
+++ b/drivers/filesystems/fs_rec/CMakeLists.txt
@@ -4,6 +4,7 @@ list(APPEND SOURCE
     cdfs.c
     ext2.c
     fat.c
+    fatx.c
     ffs.c
     fs_rec.c
     ntfs.c
diff --git a/drivers/filesystems/fs_rec/fatx.c b/drivers/filesystems/fs_rec/fatx.c
new file mode 100644
index 00000000000..165cac292e1
--- /dev/null
+++ b/drivers/filesystems/fs_rec/fatx.c
@@ -0,0 +1,130 @@
+/*
+ * PROJECT:     ReactOS File System Recognizer
+ * LICENSE:     GPL-2.0-or-later (https://spdx.org/licenses/GPL-2.0-or-later)
+ * PURPOSE:     FATX Recognizer
+ * COPYRIGHT:   Copyright 2022 Hervé Poussineau
+ */
+
+/* INCLUDES *****************************************************************/
+
+#include "fs_rec.h"
+
+#define NDEBUG
+#include <debug.h>
+
+/* TYPES ****************************************************************/
+
+#include <pshpack1.h>
+typedef struct _FATX_BOOT_SECTOR
+{
+    UCHAR SysType[4];
+    ULONG VolumeId;
+    ULONG SectorsPerCluster;
+    USHORT FatCount;
+    ULONG Reserved;
+    UCHAR Unused[4078];
+} FATX_BOOT_SECTOR, *PFATX_BOOT_SECTOR;
+#include <poppack.h>
+
+/* FUNCTIONS ****************************************************************/
+
+BOOLEAN
+NTAPI
+FsRecIsFatxVolume(IN PFATX_BOOT_SECTOR BootSector)
+{
+    BOOLEAN Result = TRUE;
+
+    PAGED_CODE();
+
+    if (BootSector->SysType[0] != 'F' ||
+        BootSector->SysType[1] != 'A' ||
+        BootSector->SysType[2] != 'T' ||
+        BootSector->SysType[3] != 'X')
+    {
+        /* Fail */
+        Result = FALSE;
+    }
+    else if (BootSector->SectorsPerCluster != 1 &&
+             BootSector->SectorsPerCluster != 2 &&
+             BootSector->SectorsPerCluster != 4 &&
+             BootSector->SectorsPerCluster != 8 &&
+             BootSector->SectorsPerCluster != 16 &&
+             BootSector->SectorsPerCluster != 32 &&
+             BootSector->SectorsPerCluster != 64 &&
+             BootSector->SectorsPerCluster != 128)
+    {
+        /* Fail */
+        Result = FALSE;
+    }
+
+    /* Return the result */
+    return Result;
+}
+
+NTSTATUS
+NTAPI
+FsRecFatxFsControl(IN PDEVICE_OBJECT DeviceObject,
+                   IN PIRP Irp)
+{
+    PIO_STACK_LOCATION Stack;
+    NTSTATUS Status;
+    PDEVICE_OBJECT MountDevice;
+    PFATX_BOOT_SECTOR Bpb = NULL;
+    ULONG SectorSize;
+    LARGE_INTEGER Offset = {{0, 0}};
+    BOOLEAN DeviceError = FALSE;
+    PAGED_CODE();
+
+    /* Get the I/O Stack and check the function type */
+    Stack = IoGetCurrentIrpStackLocation(Irp);
+    switch (Stack->MinorFunction)
+    {
+        case IRP_MN_MOUNT_VOLUME:
+
+            /* Assume failure */
+            Status = STATUS_UNRECOGNIZED_VOLUME;
+
+            /* Get the device object and request the sector size */
+            MountDevice = Stack->Parameters.MountVolume.DeviceObject;
+            if (FsRecGetDeviceSectorSize(MountDevice, &SectorSize))
+            {
+                /* Try to read the BPB */
+                if (FsRecReadBlock(MountDevice,
+                                   &Offset,
+                                   512,
+                                   SectorSize,
+                                   (PVOID)&Bpb,
+                                   &DeviceError))
+                {
+                    /* Check if it's an actual FAT volume */
+                    if (FsRecIsFatxVolume(Bpb))
+                    {
+                        /* It is! */
+                        Status = STATUS_FS_DRIVER_REQUIRED;
+                    }
+                }
+
+                /* Free the boot sector if we have one */
+                ExFreePool(Bpb);
+            }
+
+            break;
+
+        case IRP_MN_LOAD_FILE_SYSTEM:
+
+            /* Load the file system */
+            Status = FsRecLoadFileSystem(DeviceObject,
+                                         L"\\Registry\\Machine\\System\\CurrentControlSet\\Services\\vfatfs");
+            break;
+
+        default:
+
+            /* Invalid request */
+            Status = STATUS_INVALID_DEVICE_REQUEST;
+    }
+
+    /* Return Status */
+    return Status;
+}
+
+/* EOF */
diff --git a/drivers/filesystems/fs_rec/fs_rec.c b/drivers/filesystems/fs_rec/fs_rec.c
index e350fac5ceb..1dd5b4d2697 100644
--- a/drivers/filesystems/fs_rec/fs_rec.c
+++ b/drivers/filesystems/fs_rec/fs_rec.c
@@ -182,6 +182,12 @@ FsRecFsControl(IN PDEVICE_OBJECT DeviceObject,
             Status = FsRecFfsFsControl(DeviceObject, Irp);
             break;
 
+        case FS_TYPE_FATX:
+
+            /* Send FATX command */
+            Status = FsRecFatxFsControl(DeviceObject, Irp);
+            break;
+
         default:
 
             /* Unrecognized FS */
@@ -468,6 +474,17 @@ DriverEntry(IN PDRIVER_OBJECT DriverObject,
                              0);
     if (NT_SUCCESS(Status)) DeviceCount++;
 
+    /* Register FATX */
+    Status = FsRecRegisterFs(DriverObject,
+                             NULL,
+                             NULL,
+                             L"\\FatX",
+                             L"\\FileSystem\\FatXRecognizer",
+                             FS_TYPE_FATX,
+                             FILE_DEVICE_DISK_FILE_SYSTEM,
+                             0);
+    if (NT_SUCCESS(Status)) DeviceCount++;
+
     /* Return appropriate Status */
     return (DeviceCount > 0) ? STATUS_SUCCESS : STATUS_IMAGE_ALREADY_LOADED;
 }
diff --git a/drivers/filesystems/fs_rec/fs_rec.h b/drivers/filesystems/fs_rec/fs_rec.h
index 4e062e2ff4b..fe56d1ac18f 100644
--- a/drivers/filesystems/fs_rec/fs_rec.h
+++ b/drivers/filesystems/fs_rec/fs_rec.h
@@ -177,6 +177,7 @@ typedef enum _FILE_SYSTEM_TYPE
     FS_TYPE_BTRFS,
     FS_TYPE_REISERFS,
     FS_TYPE_FFS,
+    FS_TYPE_FATX,
 } FILE_SYSTEM_TYPE, *PFILE_SYSTEM_TYPE;
 
 /* FS Recognizer State */
@@ -252,6 +253,13 @@ FsRecFfsFsControl(
     IN PIRP Irp
 );
 
+NTSTATUS
+NTAPI
+FsRecFatxFsControl(
+    IN PDEVICE_OBJECT DeviceObject,
+    IN PIRP Irp
+);
+
 BOOLEAN
 NTAPI
 FsRecGetDeviceSectors(