Added file format file format subsystem for loop devices

The loop device module is extended by a file format subsystem to allow the
implementation of various disk file formats. The file format drivers are
implemented as own kernel modules and registered by the subsystem. The
subsystem takes control over the specified file format at loop creation and
calls the corresponding file format driver functions.

At the moment, the file format subsystem can handle ...

  - read
  - write
  - discard
  - flush
  - sector size

... operations of loop devices.

The file format of each loop device can be specified by the LOOP_CONFIGURE
LOOP_SET_STATUS or LOOP_SET_STATUS64 ioctl with the corresponding data
structure loop_info or respectively loop_info64.

1 files changed, 125 insertions, 0 deletions

diff --git a/uapi/linux/loop.h b/uapi/linux/loop.h
new file mode 100644
index 0000000..f93f6ad
--- /dev/null
+++ b/uapi/linux/loop.h
@@ -0,0 +1,125 @@
+/* SPDX-License-Identifier: GPL-1.0+ WITH Linux-syscall-note */
+/*
+ * include/linux/loop.h
+ *
+ * Written by Theodore Ts'o, 3/29/93.
+ *
+ * Copyright 1993 by Theodore Ts'o.  Redistribution of this file is
+ * permitted under the GNU General Public License.
+ */
+#ifndef _UAPI_LINUX_XLOOP_H
+#define _UAPI_LINUX_XLOOP_H
+
+
+#define XLO_NAME_SIZE     64
+#define XLO_KEY_SIZE      32
+
+
+/*
+ * xloop flags
+ */
+enum {
+	XLO_FLAGS_READ_ONLY	=  1,
+	XLO_FLAGS_AUTOCLEAR	=  4,
+	XLO_FLAGS_PARTSCAN	=  8,
+	XLO_FLAGS_DIRECT_IO	= 16,
+};
+
+/* XLO_FLAGS that can be set using XLOOP_SET_STATUS(64) */
+#define XLOOP_SET_STATUS_SETTABLE_FLAGS (XLO_FLAGS_AUTOCLEAR | XLO_FLAGS_PARTSCAN)
+
+/* XLO_FLAGS that can be cleared using XLOOP_SET_STATUS(64) */
+#define XLOOP_SET_STATUS_CLEARABLE_FLAGS (XLO_FLAGS_AUTOCLEAR)
+
+/* XLO_FLAGS that can be set using XLOOP_CONFIGURE */
+#define XLOOP_CONFIGURE_SETTABLE_FLAGS (XLO_FLAGS_READ_ONLY | XLO_FLAGS_AUTOCLEAR \
+				       | XLO_FLAGS_PARTSCAN | XLO_FLAGS_DIRECT_IO)
+
+#include <asm/posix_types.h>  /* for __kernel_old_dev_t */
+#include <linux/types.h>	  /* for __u64 */
+
+/* Backwards compatibility version */
+struct xloop_info {
+	int                xlo_number;                    /* ioctl r/o */
+	__kernel_old_dev_t xlo_device;                    /* ioctl r/o */
+	unsigned long      xlo_inode;                     /* ioctl r/o */
+	__kernel_old_dev_t xlo_rdevice;                   /* ioctl r/o */
+	int                xlo_offset;
+	int                xlo_encrypt_type;
+	int                xlo_encrypt_key_size;          /* ioctl w/o */
+	int                xlo_flags;
+	char               xlo_name[XLO_NAME_SIZE];
+	unsigned char      xlo_encrypt_key[XLO_KEY_SIZE]; /* ioctl w/o */
+	unsigned long      xlo_init[2];
+	char               reserved[4];
+	int                xlo_file_fmt_type;
+};
+
+struct xloop_info64 {
+	__u64              xlo_device;                     /* ioctl r/o */
+	__u64              xlo_inode;                      /* ioctl r/o */
+	__u64              xlo_rdevice;                    /* ioctl r/o */
+	__u64              xlo_offset;
+	__u64              xlo_sizelimit;  /* bytes, 0 == max available */
+	__u32              xlo_number;                     /* ioctl r/o */
+	__u32              xlo_encrypt_type;
+	__u32              xlo_encrypt_key_size;           /* ioctl w/o */
+	__u32              xlo_flags;
+	__u8               xlo_file_name[XLO_NAME_SIZE];
+	__u8               xlo_crypt_name[XLO_NAME_SIZE];
+	__u8               xlo_encrypt_key[XLO_KEY_SIZE];  /* ioctl w/o */
+	__u64              xlo_init[2];
+	__u32              xlo_file_fmt_type;
+};
+
+/**
+ * struct xloop_config - Complete configuration for a xloop device.
+ * @fd: fd of the file to be used as a backing file for the xloop device.
+ * @block_size: block size to use; ignored if 0.
+ * @info: struct xloop_info64 to configure the xloop device with.
+ *
+ * This structure is used with the XLOOP_CONFIGURE ioctl, and can be used to
+ * atomically setup and configure all xloop device parameters at once.
+ */
+struct xloop_config {
+	__u32               fd;
+	__u32               block_size;
+	struct xloop_info64	info;
+	__u64               __reserved[8];
+};
+
+/*
+ * xloop filter types
+ */
+#define XLO_CRYPT_NONE        0
+#define XLO_CRYPT_XOR         1
+#define XLO_CRYPT_DES         2
+#define XLO_CRYPT_FISH2       3  /* Twofish encryption */
+#define XLO_CRYPT_BLOW        4
+#define XLO_CRYPT_CAST128     5
+#define XLO_CRYPT_IDEA        6
+#define XLO_CRYPT_DUMMY       9
+#define XLO_CRYPT_SKIPJACK   10
+#define XLO_CRYPT_CRYPTOAPI  18
+#define MAX_XLO_CRYPT        20
+
+/*
+ * IOCTL commands --- we will commandeer 0x4C ('L')
+ */
+#define XLOOP_SET_FD         0x4C00
+#define XLOOP_CLR_FD         0x4C01
+#define XLOOP_SET_STATUS     0x4C02
+#define XLOOP_GET_STATUS     0x4C03
+#define XLOOP_SET_STATUS64   0x4C04
+#define XLOOP_GET_STATUS64   0x4C05
+#define XLOOP_CHANGE_FD      0x4C06
+#define XLOOP_SET_CAPACITY   0x4C07
+#define XLOOP_SET_DIRECT_IO  0x4C08
+#define XLOOP_SET_BLOCK_SIZE 0x4C09
+#define XLOOP_CONFIGURE      0x4C0A
+
+/* /dev/xloop-control interface */
+#define XLOOP_CTL_ADD        0x4C80
+#define XLOOP_CTL_REMOVE     0x4C81
+#define XLOOP_CTL_GET_FREE   0x4C82
+#endif /* _UAPI_LINUX_XLOOP_H */