// SPDX-License-Identifier: GPL-2.0

  /*
   *  linux/fs/ioctl.c
   *
   *  Copyright (C) 1991, 1992  Linus Torvalds
   */

  #include <linux/syscalls.h>
  #include <linux/mm.h>

  #include <linux/capability.h>

  #include <linux/compat.h>

  #include <linux/file.h>
  #include <linux/fs.h>
  #include <linux/security.h>

  #include <linux/export.h>

  #include <linux/uaccess.h>

  #include <linux/writeback.h>
  #include <linux/buffer_head.h>

  #include <linux/falloc.h>

  #include <linux/sched/signal.h>

  #include <linux/fiemap.h>

  #include "internal.h"

  #include <asm/ioctls.h>

  /* So that the fiemap access checks can't overflow on 32 bit machines. */
  #define FIEMAP_MAX_EXTENTS	(UINT_MAX / sizeof(struct fiemap_extent))

  /**
   * vfs_ioctl - call filesystem specific ioctl methods

   * @filp:	open file to invoke ioctl method on
   * @cmd:	ioctl command to execute
   * @arg:	command-specific argument for ioctl

   *
   * Invokes filesystem specific ->unlocked_ioctl, if one exists; otherwise

   * returns -ENOTTY.
   *
   * Returns 0 on success, -errno on error.
   */

  long vfs_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)

  {
  	int error = -ENOTTY;

  	if (!filp->f_op->unlocked_ioctl)

  		goto out;

  	error = filp->f_op->unlocked_ioctl(filp, cmd, arg);
  	if (error == -ENOIOCTLCMD)

  		error = -ENOTTY;

   out:
  	return error;
  }

  EXPORT_SYMBOL(vfs_ioctl);

  static int ioctl_fibmap(struct file *filp, int __user *p)
  {

  	struct inode *inode = file_inode(filp);

  	struct super_block *sb = inode->i_sb;

  	int error, ur_block;
  	sector_t block;

  	if (!capable(CAP_SYS_RAWIO))
  		return -EPERM;

  
  	error = get_user(ur_block, p);
  	if (error)
  		return error;

  	if (ur_block < 0)
  		return -EINVAL;

  	block = ur_block;
  	error = bmap(inode, &block);

  	if (block > INT_MAX) {
  		error = -ERANGE;
  		pr_warn_ratelimited("[%s/%d] FS: %s File: %pD4 would truncate fibmap result
  ",
  				    current->comm, task_pid_nr(current),
  				    sb->s_id, filp);
  	}

  	if (error)
  		ur_block = 0;
  	else
  		ur_block = block;
  
  	if (put_user(ur_block, p))
  		error = -EFAULT;
  
  	return error;

  }

  /**
   * fiemap_fill_next_extent - Fiemap helper function
   * @fieinfo:	Fiemap context passed into ->fiemap
   * @logical:	Extent logical start offset, in bytes
   * @phys:	Extent physical start offset, in bytes
   * @len:	Extent length, in bytes
   * @flags:	FIEMAP_EXTENT flags that describe this extent
   *
   * Called from file system ->fiemap callback. Will populate extent
   * info as passed in via arguments and copy to user memory. On
   * success, extent count on fieinfo is incremented.
   *
   * Returns 0 on success, -errno on error, 1 if this was the last
   * extent that will fit in user array.
   */
  #define SET_UNKNOWN_FLAGS	(FIEMAP_EXTENT_DELALLOC)
  #define SET_NO_UNMOUNTED_IO_FLAGS	(FIEMAP_EXTENT_DATA_ENCRYPTED)
  #define SET_NOT_ALIGNED_FLAGS	(FIEMAP_EXTENT_DATA_TAIL|FIEMAP_EXTENT_DATA_INLINE)
  int fiemap_fill_next_extent(struct fiemap_extent_info *fieinfo, u64 logical,
  			    u64 phys, u64 len, u32 flags)
  {
  	struct fiemap_extent extent;

  	struct fiemap_extent __user *dest = fieinfo->fi_extents_start;

  
  	/* only count the extents */
  	if (fieinfo->fi_extents_max == 0) {
  		fieinfo->fi_extents_mapped++;
  		return (flags & FIEMAP_EXTENT_LAST) ? 1 : 0;
  	}
  
  	if (fieinfo->fi_extents_mapped >= fieinfo->fi_extents_max)
  		return 1;
  
  	if (flags & SET_UNKNOWN_FLAGS)
  		flags |= FIEMAP_EXTENT_UNKNOWN;
  	if (flags & SET_NO_UNMOUNTED_IO_FLAGS)
  		flags |= FIEMAP_EXTENT_ENCODED;
  	if (flags & SET_NOT_ALIGNED_FLAGS)
  		flags |= FIEMAP_EXTENT_NOT_ALIGNED;
  
  	memset(&extent, 0, sizeof(extent));
  	extent.fe_logical = logical;
  	extent.fe_physical = phys;
  	extent.fe_length = len;
  	extent.fe_flags = flags;
  
  	dest += fieinfo->fi_extents_mapped;
  	if (copy_to_user(dest, &extent, sizeof(extent)))
  		return -EFAULT;
  
  	fieinfo->fi_extents_mapped++;
  	if (fieinfo->fi_extents_mapped == fieinfo->fi_extents_max)
  		return 1;
  	return (flags & FIEMAP_EXTENT_LAST) ? 1 : 0;
  }
  EXPORT_SYMBOL(fiemap_fill_next_extent);
  
  /**

   * fiemap_prep - check validity of requested flags for fiemap
   * @inode:	Inode to operate on

   * @fieinfo:	Fiemap context passed into ->fiemap

   * @start:	Start of the mapped range
   * @len:	Length of the mapped range, can be truncated by this function.
   * @supported_flags:	Set of fiemap flags that the file system understands

   *

   * This function must be called from each ->fiemap instance to validate the
   * fiemap request against the file system parameters.

   *

   * Returns 0 on success, or a negative error on failure.

   */

  int fiemap_prep(struct inode *inode, struct fiemap_extent_info *fieinfo,
  		u64 start, u64 *len, u32 supported_flags)

  {

  	u64 maxbytes = inode->i_sb->s_maxbytes;

  	u32 incompat_flags;

  	int ret = 0;

  	if (*len == 0)

  		return -EINVAL;

  	if (start > maxbytes)

  		return -EFBIG;
  
  	/*
  	 * Shrink request scope to what the fs can actually handle.
  	 */

  	if (*len > maxbytes || (maxbytes - *len) < start)
  		*len = maxbytes - start;

  	supported_flags |= FIEMAP_FLAG_SYNC;

  	supported_flags &= FIEMAP_FLAGS_COMPAT;
  	incompat_flags = fieinfo->fi_flags & ~supported_flags;
  	if (incompat_flags) {
  		fieinfo->fi_flags = incompat_flags;
  		return -EBADR;
  	}

  
  	if (fieinfo->fi_flags & FIEMAP_FLAG_SYNC)
  		ret = filemap_write_and_wait(inode->i_mapping);
  	return ret;

  }

  EXPORT_SYMBOL(fiemap_prep);

  static int ioctl_fiemap(struct file *filp, struct fiemap __user *ufiemap)

  {
  	struct fiemap fiemap;
  	struct fiemap_extent_info fieinfo = { 0, };

  	struct inode *inode = file_inode(filp);

  	int error;
  
  	if (!inode->i_op->fiemap)
  		return -EOPNOTSUPP;

  	if (copy_from_user(&fiemap, ufiemap, sizeof(fiemap)))

  		return -EFAULT;
  
  	if (fiemap.fm_extent_count > FIEMAP_MAX_EXTENTS)
  		return -EINVAL;

  	fieinfo.fi_flags = fiemap.fm_flags;
  	fieinfo.fi_extents_max = fiemap.fm_extent_count;

  	fieinfo.fi_extents_start = ufiemap->fm_extents;

  	error = inode->i_op->fiemap(inode, &fieinfo, fiemap.fm_start,
  			fiemap.fm_length);

  	fiemap.fm_flags = fieinfo.fi_flags;
  	fiemap.fm_mapped_extents = fieinfo.fi_extents_mapped;

  	if (copy_to_user(ufiemap, &fiemap, sizeof(fiemap)))

  		error = -EFAULT;
  
  	return error;
  }

  static long ioctl_file_clone(struct file *dst_file, unsigned long srcfd,
  			     u64 off, u64 olen, u64 destoff)
  {
  	struct fd src_file = fdget(srcfd);

  	loff_t cloned;

  	int ret;
  
  	if (!src_file.file)
  		return -EBADF;

  	ret = -EXDEV;
  	if (src_file.file->f_path.mnt != dst_file->f_path.mnt)
  		goto fdput;

  	cloned = vfs_clone_file_range(src_file.file, off, dst_file, destoff,

  				      olen, 0);

  	if (cloned < 0)
  		ret = cloned;
  	else if (olen && cloned != olen)
  		ret = -EINVAL;
  	else
  		ret = 0;

  fdput:

  	fdput(src_file);
  	return ret;
  }

  static long ioctl_file_clone_range(struct file *file,
  				   struct file_clone_range __user *argp)

  {
  	struct file_clone_range args;
  
  	if (copy_from_user(&args, argp, sizeof(args)))
  		return -EFAULT;
  	return ioctl_file_clone(file, args.src_fd, args.src_offset,
  				args.src_length, args.dest_offset);
  }

  #ifdef CONFIG_BLOCK

  static inline sector_t logical_to_blk(struct inode *inode, loff_t offset)
  {
  	return (offset >> inode->i_blkbits);
  }
  
  static inline loff_t blk_to_logical(struct inode *inode, sector_t blk)
  {
  	return (blk << inode->i_blkbits);
  }

  /**
   * __generic_block_fiemap - FIEMAP for block based inodes (no locking)

   * @inode: the inode to map
   * @fieinfo: the fiemap info struct that will be passed back to userspace
   * @start: where to start mapping in the inode
   * @len: how much space to map
   * @get_block: the fs's get_block function

   *
   * This does FIEMAP for block based inodes.  Basically it will just loop
   * through get_block until we hit the number of extents we want to map, or we
   * go past the end of the file and hit a hole.
   *
   * If it is possible to have data blocks beyond a hole past @inode->i_size, then
   * please do not use this function, it will stop at the first unmapped block

   * beyond i_size.
   *
   * If you use this function directly, you need to do your own locking. Use
   * generic_block_fiemap if you want the locking done for you.

   */

  static int __generic_block_fiemap(struct inode *inode,

  			   struct fiemap_extent_info *fieinfo, loff_t start,
  			   loff_t len, get_block_t *get_block)

  {

  	struct buffer_head map_bh;
  	sector_t start_blk, last_blk;
  	loff_t isize = i_size_read(inode);

  	u64 logical = 0, phys = 0, size = 0;
  	u32 flags = FIEMAP_EXTENT_MERGED;

  	bool past_eof = false, whole_file = false;
  	int ret = 0;

  	ret = fiemap_prep(inode, fieinfo, start, &len, FIEMAP_FLAG_SYNC);

  	if (ret)

  		return ret;

  	/*
  	 * Either the i_mutex or other appropriate locking needs to be held
  	 * since we expect isize to not change at all through the duration of
  	 * this call.
  	 */
  	if (len >= isize) {
  		whole_file = true;
  		len = isize;
  	}

  	/*
  	 * Some filesystems can't deal with being asked to map less than
  	 * blocksize, so make sure our len is at least block length.
  	 */
  	if (logical_to_blk(inode, len) == 0)
  		len = blk_to_logical(inode, 1);

  	start_blk = logical_to_blk(inode, start);
  	last_blk = logical_to_blk(inode, start + len - 1);

  
  	do {
  		/*
  		 * we set b_size to the total size we want so it will map as
  		 * many contiguous blocks as possible at once
  		 */

  		memset(&map_bh, 0, sizeof(struct buffer_head));
  		map_bh.b_size = len;

  		ret = get_block(inode, start_blk, &map_bh, 0);

  		if (ret)
  			break;
  
  		/* HOLE */

  		if (!buffer_mapped(&map_bh)) {

  			start_blk++;
  
  			/*

  			 * We want to handle the case where there is an

  			 * allocated block at the front of the file, and then
  			 * nothing but holes up to the end of the file properly,
  			 * to make sure that extent at the front gets properly
  			 * marked with FIEMAP_EXTENT_LAST
  			 */
  			if (!past_eof &&

  			    blk_to_logical(inode, start_blk) >= isize)

  				past_eof = 1;

  			/*

  			 * First hole after going past the EOF, this is our

  			 * last extent
  			 */

  			if (past_eof && size) {

  				flags = FIEMAP_EXTENT_MERGED|FIEMAP_EXTENT_LAST;
  				ret = fiemap_fill_next_extent(fieinfo, logical,
  							      phys, size,
  							      flags);

  			} else if (size) {
  				ret = fiemap_fill_next_extent(fieinfo, logical,
  							      phys, size, flags);
  				size = 0;

  			}

  			/* if we have holes up to/past EOF then we're done */

  			if (start_blk > last_blk || past_eof || ret)

  				break;

  		} else {

  			/*

  			 * We have gone over the length of what we wanted to

  			 * map, and it wasn't the entire file, so add the extent
  			 * we got last time and exit.
  			 *
  			 * This is for the case where say we want to map all the
  			 * way up to the second to the last block in a file, but
  			 * the last block is a hole, making the second to last
  			 * block FIEMAP_EXTENT_LAST.  In this case we want to
  			 * see if there is a hole after the second to last block
  			 * so we can mark it properly.  If we found data after
  			 * we exceeded the length we were requesting, then we
  			 * are good to go, just add the extent to the fieinfo
  			 * and break
  			 */

  			if (start_blk > last_blk && !whole_file) {

  				ret = fiemap_fill_next_extent(fieinfo, logical,
  							      phys, size,
  							      flags);
  				break;
  			}
  
  			/*
  			 * if size != 0 then we know we already have an extent
  			 * to add, so add it.
  			 */
  			if (size) {

  				ret = fiemap_fill_next_extent(fieinfo, logical,
  							      phys, size,
  							      flags);
  				if (ret)
  					break;
  			}
  
  			logical = blk_to_logical(inode, start_blk);

  			phys = blk_to_logical(inode, map_bh.b_blocknr);
  			size = map_bh.b_size;

  			flags = FIEMAP_EXTENT_MERGED;

  			start_blk += logical_to_blk(inode, size);
  
  			/*

  			 * If we are past the EOF, then we need to make sure as
  			 * soon as we find a hole that the last extent we found
  			 * is marked with FIEMAP_EXTENT_LAST

  			 */

  			if (!past_eof && logical + size >= isize)
  				past_eof = true;

  		}
  		cond_resched();

  		if (fatal_signal_pending(current)) {
  			ret = -EINTR;
  			break;
  		}

  	} while (1);

  	/* If ret is 1 then we just hit the end of the extent array */

  	if (ret == 1)
  		ret = 0;
  
  	return ret;
  }

  
  /**
   * generic_block_fiemap - FIEMAP for block based inodes
   * @inode: The inode to map
   * @fieinfo: The mapping information
   * @start: The initial block to map
   * @len: The length of the extect to attempt to map
   * @get_block: The block mapping function for the fs
   *
   * Calls __generic_block_fiemap to map the inode, after taking
   * the inode's mutex lock.
   */
  
  int generic_block_fiemap(struct inode *inode,
  			 struct fiemap_extent_info *fieinfo, u64 start,
  			 u64 len, get_block_t *get_block)
  {
  	int ret;

  	inode_lock(inode);

  	ret = __generic_block_fiemap(inode, fieinfo, start, len, get_block);

  	inode_unlock(inode);

  	return ret;
  }

  EXPORT_SYMBOL(generic_block_fiemap);

  #endif  /*  CONFIG_BLOCK  */

  /*
   * This provides compatibility with legacy XFS pre-allocation ioctls
   * which predate the fallocate syscall.
   *
   * Only the l_start, l_len and l_whence fields of the 'struct space_resv'
   * are used here, rest are ignored.
   */

  static int ioctl_preallocate(struct file *filp, int mode, void __user *argp)

  {

  	struct inode *inode = file_inode(filp);

  	struct space_resv sr;
  
  	if (copy_from_user(&sr, argp, sizeof(sr)))
  		return -EFAULT;
  
  	switch (sr.l_whence) {
  	case SEEK_SET:
  		break;
  	case SEEK_CUR:
  		sr.l_start += filp->f_pos;
  		break;
  	case SEEK_END:
  		sr.l_start += i_size_read(inode);
  		break;
  	default:
  		return -EINVAL;
  	}

  	return vfs_fallocate(filp, mode | FALLOC_FL_KEEP_SIZE, sr.l_start,
  			sr.l_len);

  }

  /* on ia32 l_start is on a 32-bit boundary */
  #if defined CONFIG_COMPAT && defined(CONFIG_X86_64)
  /* just account for different alignment */

  static int compat_ioctl_preallocate(struct file *file, int mode,
  				    struct space_resv_32 __user *argp)

  {
  	struct inode *inode = file_inode(file);
  	struct space_resv_32 sr;
  
  	if (copy_from_user(&sr, argp, sizeof(sr)))
  		return -EFAULT;
  
  	switch (sr.l_whence) {
  	case SEEK_SET:
  		break;
  	case SEEK_CUR:
  		sr.l_start += file->f_pos;
  		break;
  	case SEEK_END:
  		sr.l_start += i_size_read(inode);
  		break;
  	default:
  		return -EINVAL;
  	}

  	return vfs_fallocate(file, mode | FALLOC_FL_KEEP_SIZE, sr.l_start, sr.l_len);

  }
  #endif

  static int file_ioctl(struct file *filp, unsigned int cmd, int __user *p)

  {

  	switch (cmd) {

  	case FIBMAP:

  		return ioctl_fibmap(filp, p);

  	case FS_IOC_RESVSP:
  	case FS_IOC_RESVSP64:

  		return ioctl_preallocate(filp, 0, p);
  	case FS_IOC_UNRESVSP:
  	case FS_IOC_UNRESVSP64:
  		return ioctl_preallocate(filp, FALLOC_FL_PUNCH_HOLE, p);
  	case FS_IOC_ZERO_RANGE:
  		return ioctl_preallocate(filp, FALLOC_FL_ZERO_RANGE, p);

  	}

  	return -ENOIOCTLCMD;

  }

  static int ioctl_fionbio(struct file *filp, int __user *argp)
  {
  	unsigned int flag;
  	int on, error;
  
  	error = get_user(on, argp);
  	if (error)
  		return error;
  	flag = O_NONBLOCK;
  #ifdef __sparc__
  	/* SunOS compatibility item. */
  	if (O_NONBLOCK != O_NDELAY)
  		flag |= O_NDELAY;
  #endif

  	spin_lock(&filp->f_lock);

  	if (on)
  		filp->f_flags |= flag;
  	else
  		filp->f_flags &= ~flag;

  	spin_unlock(&filp->f_lock);

  	return error;
  }
  
  static int ioctl_fioasync(unsigned int fd, struct file *filp,
  			  int __user *argp)
  {
  	unsigned int flag;
  	int on, error;
  
  	error = get_user(on, argp);
  	if (error)
  		return error;
  	flag = on ? FASYNC : 0;
  
  	/* Did FASYNC state change ? */
  	if ((flag ^ filp->f_flags) & FASYNC) {

  		if (filp->f_op->fasync)

  			/* fasync() adjusts filp->f_flags */

  			error = filp->f_op->fasync(fd, filp, on);

  		else

  			error = -ENOTTY;
  	}

  	return error < 0 ? error : 0;

  }

  static int ioctl_fsfreeze(struct file *filp)
  {

  	struct super_block *sb = file_inode(filp)->i_sb;

  	if (!ns_capable(sb->s_user_ns, CAP_SYS_ADMIN))

  		return -EPERM;
  
  	/* If filesystem doesn't support freeze feature, return. */

  	if (sb->s_op->freeze_fs == NULL && sb->s_op->freeze_super == NULL)

  		return -EOPNOTSUPP;

  	/* Freeze */

  	if (sb->s_op->freeze_super)
  		return sb->s_op->freeze_super(sb);

  	return freeze_super(sb);

  }
  
  static int ioctl_fsthaw(struct file *filp)
  {

  	struct super_block *sb = file_inode(filp)->i_sb;

  	if (!ns_capable(sb->s_user_ns, CAP_SYS_ADMIN))

  		return -EPERM;

  	/* Thaw */

  	if (sb->s_op->thaw_super)
  		return sb->s_op->thaw_super(sb);

  	return thaw_super(sb);

  }

  static int ioctl_file_dedupe_range(struct file *file,
  				   struct file_dedupe_range __user *argp)

  {

  	struct file_dedupe_range *same = NULL;
  	int ret;
  	unsigned long size;
  	u16 count;
  
  	if (get_user(count, &argp->dest_count)) {
  		ret = -EFAULT;
  		goto out;
  	}
  
  	size = offsetof(struct file_dedupe_range __user, info[count]);

  	if (size > PAGE_SIZE) {
  		ret = -ENOMEM;
  		goto out;
  	}

  
  	same = memdup_user(argp, size);
  	if (IS_ERR(same)) {
  		ret = PTR_ERR(same);
  		same = NULL;
  		goto out;
  	}

  	same->dest_count = count;

  	ret = vfs_dedupe_file_range(file, same);
  	if (ret)
  		goto out;
  
  	ret = copy_to_user(argp, same, size);
  	if (ret)
  		ret = -EFAULT;
  
  out:
  	kfree(same);
  	return ret;
  }

  /*

   * do_vfs_ioctl() is not for drivers and not intended to be EXPORT_SYMBOL()'d.

   * It's just a simple helper for sys_ioctl and compat_sys_ioctl.

   *
   * When you add any new common ioctls to the switches above and below,
   * please ensure they have compatible arguments in compat mode.

   */

  static int do_vfs_ioctl(struct file *filp, unsigned int fd,
  			unsigned int cmd, unsigned long arg)

  {

  	void __user *argp = (void __user *)arg;

  	struct inode *inode = file_inode(filp);

  
  	switch (cmd) {

  	case FIOCLEX:
  		set_close_on_exec(fd, 1);

  		return 0;

  	case FIONCLEX:
  		set_close_on_exec(fd, 0);

  		return 0;

  	case FIONBIO:

  		return ioctl_fionbio(filp, argp);

  
  	case FIOASYNC:

  		return ioctl_fioasync(fd, filp, argp);

  
  	case FIOQSIZE:

  		if (S_ISDIR(inode->i_mode) || S_ISREG(inode->i_mode) ||
  		    S_ISLNK(inode->i_mode)) {
  			loff_t res = inode_get_bytes(inode);

  			return copy_to_user(argp, &res, sizeof(res)) ?
  					    -EFAULT : 0;
  		}
  
  		return -ENOTTY;

  
  	case FIFREEZE:

  		return ioctl_fsfreeze(filp);

  
  	case FITHAW:

  		return ioctl_fsthaw(filp);

  	case FS_IOC_FIEMAP:

  		return ioctl_fiemap(filp, argp);

  
  	case FIGETBSZ:

  		/* anon_bdev filesystems may not have a block size */
  		if (!inode->i_sb->s_blocksize)
  			return -EINVAL;

  		return put_user(inode->i_sb->s_blocksize, (int __user *)argp);

  	case FICLONE:
  		return ioctl_file_clone(filp, arg, 0, 0, 0);
  
  	case FICLONERANGE:
  		return ioctl_file_clone_range(filp, argp);

  	case FIDEDUPERANGE:
  		return ioctl_file_dedupe_range(filp, argp);

  	case FIONREAD:
  		if (!S_ISREG(inode->i_mode))
  			return vfs_ioctl(filp, cmd, arg);
  
  		return put_user(i_size_read(inode) - filp->f_pos,
  				(int __user *)argp);

  	default:

  		if (S_ISREG(inode->i_mode))

  			return file_ioctl(filp, cmd, argp);

  		break;

  	}

  
  	return -ENOIOCTLCMD;

  }

  SYSCALL_DEFINE3(ioctl, unsigned int, fd, unsigned int, cmd, unsigned long, arg)

  {

  	struct fd f = fdget(fd);

  	int error;

  
  	if (!f.file)
  		return -EBADF;

  	error = security_file_ioctl(f.file, cmd, arg);

  	if (error)
  		goto out;
  
  	error = do_vfs_ioctl(f.file, fd, cmd, arg);
  	if (error == -ENOIOCTLCMD)
  		error = vfs_ioctl(f.file, cmd, arg);
  
  out:

  	fdput(f);

  	return error;
  }

  #ifdef CONFIG_COMPAT
  /**
   * compat_ptr_ioctl - generic implementation of .compat_ioctl file operation
   *
   * This is not normally called as a function, but instead set in struct
   * file_operations as
   *
   *     .compat_ioctl = compat_ptr_ioctl,
   *
   * On most architectures, the compat_ptr_ioctl() just passes all arguments
   * to the corresponding ->ioctl handler. The exception is arch/s390, where
   * compat_ptr() clears the top bit of a 32-bit pointer value, so user space
   * pointers to the second 2GB alias the first 2GB, as is the case for
   * native 32-bit s390 user space.
   *
   * The compat_ptr_ioctl() function must therefore be used only with ioctl
   * functions that either ignore the argument or pass a pointer to a
   * compatible data type.
   *
   * If any ioctl command handled by fops->unlocked_ioctl passes a plain
   * integer instead of a pointer, or any of the passed data types
   * is incompatible between 32-bit and 64-bit architectures, a proper
   * handler is required instead of compat_ptr_ioctl.
   */
  long compat_ptr_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
  {
  	if (!file->f_op->unlocked_ioctl)
  		return -ENOIOCTLCMD;
  
  	return file->f_op->unlocked_ioctl(file, cmd, (unsigned long)compat_ptr(arg));
  }
  EXPORT_SYMBOL(compat_ptr_ioctl);

  
  COMPAT_SYSCALL_DEFINE3(ioctl, unsigned int, fd, unsigned int, cmd,

  		       compat_ulong_t, arg)

  {

  	struct fd f = fdget(fd);

  	int error;

  	if (!f.file)

  		return -EBADF;

  
  	/* RED-PEN how should LSM module know it's handling 32bit? */
  	error = security_file_ioctl(f.file, cmd, arg);
  	if (error)

  		goto out;

  
  	switch (cmd) {

  	/* FICLONE takes an int argument, so don't use compat_ptr() */

  	case FICLONE:

  		error = ioctl_file_clone(f.file, arg, 0, 0, 0);
  		break;

  #if defined(CONFIG_X86_64)

  	/* these get messy on amd64 due to alignment differences */

  	case FS_IOC_RESVSP_32:
  	case FS_IOC_RESVSP64_32:
  		error = compat_ioctl_preallocate(f.file, 0, compat_ptr(arg));

  		break;

  	case FS_IOC_UNRESVSP_32:
  	case FS_IOC_UNRESVSP64_32:
  		error = compat_ioctl_preallocate(f.file, FALLOC_FL_PUNCH_HOLE,
  				compat_ptr(arg));

  		break;

  	case FS_IOC_ZERO_RANGE_32:
  		error = compat_ioctl_preallocate(f.file, FALLOC_FL_ZERO_RANGE,
  				compat_ptr(arg));

  		break;

  #endif

  	/*
  	 * everything else in do_vfs_ioctl() takes either a compatible
  	 * pointer argument or no argument -- call it with a modified
  	 * argument.
  	 */

  	default:

  		error = do_vfs_ioctl(f.file, fd, cmd,
  				     (unsigned long)compat_ptr(arg));
  		if (error != -ENOIOCTLCMD)
  			break;
  
  		if (f.file->f_op->compat_ioctl)

  			error = f.file->f_op->compat_ioctl(f.file, cmd, arg);

  		if (error == -ENOIOCTLCMD)
  			error = -ENOTTY;
  		break;

  	}

   out:

  	fdput(f);

  	return error;
  }

  #endif