fs/ntfs3: Add compression

This patch adds different types of NTFS-applicable compressions:
- lznt
- lzx
- xpress
Latter two (lzx, xpress) implement Windows Compact OS feature and
were taken from ntfs-3g system comression plugin authored by Eric Biggers
(https://github.com/ebiggers/ntfs-3g-system-compression)
which were ported to ntfs3 and adapted to Linux Kernel environment.

Signed-off-by: Konstantin Komarov <almaz.alexandrovich@paragon-software.com>

6 files changed, 2000 insertions, 0 deletions

diff --git a/fs/ntfs3/lib/decompress_common.c b/fs/ntfs3/lib/decompress_common.c
new file mode 100644
index 000000000000..83c9e93aea77
--- /dev/null
+++ b/fs/ntfs3/lib/decompress_common.c
@@ -0,0 +1,332 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * decompress_common.c - Code shared by the XPRESS and LZX decompressors
+ *
+ * Copyright (C) 2015 Eric Biggers
+ *
+ * This program is free software: you can redistribute it and/or modify it under
+ * the terms of the GNU General Public License as published by the Free Software
+ * Foundation, either version 2 of the License, or (at your option) any later
+ * version.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+ * FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more
+ * details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "decompress_common.h"
+
+/*
+ * make_huffman_decode_table() -
+ *
+ * Build a decoding table for a canonical prefix code, or "Huffman code".
+ *
+ * This is an internal function, not part of the library API!
+ *
+ * This takes as input the length of the codeword for each symbol in the
+ * alphabet and produces as output a table that can be used for fast
+ * decoding of prefix-encoded symbols using read_huffsym().
+ *
+ * Strictly speaking, a canonical prefix code might not be a Huffman
+ * code.  But this algorithm will work either way; and in fact, since
+ * Huffman codes are defined in terms of symbol frequencies, there is no
+ * way for the decompressor to know whether the code is a true Huffman
+ * code or not until all symbols have been decoded.
+ *
+ * Because the prefix code is assumed to be "canonical", it can be
+ * reconstructed directly from the codeword lengths.  A prefix code is
+ * canonical if and only if a longer codeword never lexicographically
+ * precedes a shorter codeword, and the lexicographic ordering of
+ * codewords of the same length is the same as the lexicographic ordering
+ * of the corresponding symbols.  Consequently, we can sort the symbols
+ * primarily by codeword length and secondarily by symbol value, then
+ * reconstruct the prefix code by generating codewords lexicographically
+ * in that order.
+ *
+ * This function does not, however, generate the prefix code explicitly.
+ * Instead, it directly builds a table for decoding symbols using the
+ * code.  The basic idea is this: given the next 'max_codeword_len' bits
+ * in the input, we can look up the decoded symbol by indexing a table
+ * containing 2**max_codeword_len entries.  A codeword with length
+ * 'max_codeword_len' will have exactly one entry in this table, whereas
+ * a codeword shorter than 'max_codeword_len' will have multiple entries
+ * in this table.  Precisely, a codeword of length n will be represented
+ * by 2**(max_codeword_len - n) entries in this table.  The 0-based index
+ * of each such entry will contain the corresponding codeword as a prefix
+ * when zero-padded on the left to 'max_codeword_len' binary digits.
+ *
+ * That's the basic idea, but we implement two optimizations regarding
+ * the format of the decode table itself:
+ *
+ * - For many compression formats, the maximum codeword length is too
+ *   long for it to be efficient to build the full decoding table
+ *   whenever a new prefix code is used.  Instead, we can build the table
+ *   using only 2**table_bits entries, where 'table_bits' is some number
+ *   less than or equal to 'max_codeword_len'.  Then, only codewords of
+ *   length 'table_bits' and shorter can be directly looked up.  For
+ *   longer codewords, the direct lookup instead produces the root of a
+ *   binary tree.  Using this tree, the decoder can do traditional
+ *   bit-by-bit decoding of the remainder of the codeword.  Child nodes
+ *   are allocated in extra entries at the end of the table; leaf nodes
+ *   contain symbols.  Note that the long-codeword case is, in general,
+ *   not performance critical, since in Huffman codes the most frequently
+ *   used symbols are assigned the shortest codeword lengths.
+ *
+ * - When we decode a symbol using a direct lookup of the table, we still
+ *   need to know its length so that the bitstream can be advanced by the
+ *   appropriate number of bits.  The simple solution is to simply retain
+ *   the 'lens' array and use the decoded symbol as an index into it.
+ *   However, this requires two separate array accesses in the fast path.
+ *   The optimization is to store the length directly in the decode
+ *   table.  We use the bottom 11 bits for the symbol and the top 5 bits
+ *   for the length.  In addition, to combine this optimization with the
+ *   previous one, we introduce a special case where the top 2 bits of
+ *   the length are both set if the entry is actually the root of a
+ *   binary tree.
+ *
+ * @decode_table:
+ *	The array in which to create the decoding table.  This must have
+ *	a length of at least ((2**table_bits) + 2 * num_syms) entries.
+ *
+ * @num_syms:
+ *	The number of symbols in the alphabet; also, the length of the
+ *	'lens' array.  Must be less than or equal to 2048.
+ *
+ * @table_bits:
+ *	The order of the decode table size, as explained above.  Must be
+ *	less than or equal to 13.
+ *
+ * @lens:
+ *	An array of length @num_syms, indexable by symbol, that gives the
+ *	length of the codeword, in bits, for that symbol.  The length can
+ *	be 0, which means that the symbol does not have a codeword
+ *	assigned.
+ *
+ * @max_codeword_len:
+ *	The longest codeword length allowed in the compression format.
+ *	All entries in 'lens' must be less than or equal to this value.
+ *	This must be less than or equal to 23.
+ *
+ * @working_space
+ *	A temporary array of length '2 * (max_codeword_len + 1) +
+ *	num_syms'.
+ *
+ * Returns 0 on success, or -1 if the lengths do not form a valid prefix
+ * code.
+ */
+int make_huffman_decode_table(u16 decode_table[], const u32 num_syms,
+			      const u32 table_bits, const u8 lens[],
+			      const u32 max_codeword_len,
+			      u16 working_space[])
+{
+	const u32 table_num_entries = 1 << table_bits;
+	u16 * const len_counts = &working_space[0];
+	u16 * const offsets = &working_space[1 * (max_codeword_len + 1)];
+	u16 * const sorted_syms = &working_space[2 * (max_codeword_len + 1)];
+	int left;
+	void *decode_table_ptr;
+	u32 sym_idx;
+	u32 codeword_len;
+	u32 stores_per_loop;
+	u32 decode_table_pos;
+	u32 len;
+	u32 sym;
+
+	/* Count how many symbols have each possible codeword length.
+	 * Note that a length of 0 indicates the corresponding symbol is not
+	 * used in the code and therefore does not have a codeword.
+	 */
+	for (len = 0; len <= max_codeword_len; len++)
+		len_counts[len] = 0;
+	for (sym = 0; sym < num_syms; sym++)
+		len_counts[lens[sym]]++;
+
+	/* We can assume all lengths are <= max_codeword_len, but we
+	 * cannot assume they form a valid prefix code.  A codeword of
+	 * length n should require a proportion of the codespace equaling
+	 * (1/2)^n.  The code is valid if and only if the codespace is
+	 * exactly filled by the lengths, by this measure.
+	 */
+	left = 1;
+	for (len = 1; len <= max_codeword_len; len++) {
+		left <<= 1;
+		left -= len_counts[len];
+		if (left < 0) {
+			/* The lengths overflow the codespace; that is, the code
+			 * is over-subscribed.
+			 */
+			return -1;
+		}
+	}
+
+	if (left) {
+		/* The lengths do not fill the codespace; that is, they form an
+		 * incomplete set.
+		 */
+		if (left == (1 << max_codeword_len)) {
+			/* The code is completely empty.  This is arguably
+			 * invalid, but in fact it is valid in LZX and XPRESS,
+			 * so we must allow it.  By definition, no symbols can
+			 * be decoded with an empty code.  Consequently, we
+			 * technically don't even need to fill in the decode
+			 * table.  However, to avoid accessing uninitialized
+			 * memory if the algorithm nevertheless attempts to
+			 * decode symbols using such a code, we zero out the
+			 * decode table.
+			 */
+			memset(decode_table, 0,
+			       table_num_entries * sizeof(decode_table[0]));
+			return 0;
+		}
+		return -1;
+	}
+
+	/* Sort the symbols primarily by length and secondarily by symbol order.
+	 */
+
+	/* Initialize 'offsets' so that offsets[len] for 1 <= len <=
+	 * max_codeword_len is the number of codewords shorter than 'len' bits.
+	 */
+	offsets[1] = 0;
+	for (len = 1; len < max_codeword_len; len++)
+		offsets[len + 1] = offsets[len] + len_counts[len];
+
+	/* Use the 'offsets' array to sort the symbols.  Note that we do not
+	 * include symbols that are not used in the code.  Consequently, fewer
+	 * than 'num_syms' entries in 'sorted_syms' may be filled.
+	 */
+	for (sym = 0; sym < num_syms; sym++)
+		if (lens[sym])
+			sorted_syms[offsets[lens[sym]]++] = sym;
+
+	/* Fill entries for codewords with length <= table_bits
+	 * --- that is, those short enough for a direct mapping.
+	 *
+	 * The table will start with entries for the shortest codeword(s), which
+	 * have the most entries.  From there, the number of entries per
+	 * codeword will decrease.
+	 */
+	decode_table_ptr = decode_table;
+	sym_idx = 0;
+	codeword_len = 1;
+	stores_per_loop = (1 << (table_bits - codeword_len));
+	for (; stores_per_loop != 0; codeword_len++, stores_per_loop >>= 1) {
+		u32 end_sym_idx = sym_idx + len_counts[codeword_len];
+
+		for (; sym_idx < end_sym_idx; sym_idx++) {
+			u16 entry;
+			u16 *p;
+			u32 n;
+
+			entry = ((u32)codeword_len << 11) | sorted_syms[sym_idx];
+			p = (u16 *)decode_table_ptr;
+			n = stores_per_loop;
+
+			do {
+				*p++ = entry;
+			} while (--n);
+
+			decode_table_ptr = p;
+		}
+	}
+
+	/* If we've filled in the entire table, we are done.  Otherwise,
+	 * there are codewords longer than table_bits for which we must
+	 * generate binary trees.
+	 */
+	decode_table_pos = (u16 *)decode_table_ptr - decode_table;
+	if (decode_table_pos != table_num_entries) {
+		u32 j;
+		u32 next_free_tree_slot;
+		u32 cur_codeword;
+
+		/* First, zero out the remaining entries.  This is
+		 * necessary so that these entries appear as
+		 * "unallocated" in the next part.  Each of these entries
+		 * will eventually be filled with the representation of
+		 * the root node of a binary tree.
+		 */
+		j = decode_table_pos;
+		do {
+			decode_table[j] = 0;
+		} while (++j != table_num_entries);
+
+		/* We allocate child nodes starting at the end of the
+		 * direct lookup table.  Note that there should be
+		 * 2*num_syms extra entries for this purpose, although
+		 * fewer than this may actually be needed.
+		 */
+		next_free_tree_slot = table_num_entries;
+
+		/* Iterate through each codeword with length greater than
+		 * 'table_bits', primarily in order of codeword length
+		 * and secondarily in order of symbol.
+		 */
+		for (cur_codeword = decode_table_pos << 1;
+		     codeword_len <= max_codeword_len;
+		     codeword_len++, cur_codeword <<= 1) {
+			u32 end_sym_idx = sym_idx + len_counts[codeword_len];
+
+			for (; sym_idx < end_sym_idx; sym_idx++, cur_codeword++) {
+				/* 'sorted_sym' is the symbol represented by the
+				 * codeword.
+				 */
+				u32 sorted_sym = sorted_syms[sym_idx];
+				u32 extra_bits = codeword_len - table_bits;
+				u32 node_idx = cur_codeword >> extra_bits;
+
+				/* Go through each bit of the current codeword
+				 * beyond the prefix of length @table_bits and
+				 * walk the appropriate binary tree, allocating
+				 * any slots that have not yet been allocated.
+				 *
+				 * Note that the 'pointer' entry to the binary
+				 * tree, which is stored in the direct lookup
+				 * portion of the table, is represented
+				 * identically to other internal (non-leaf)
+				 * nodes of the binary tree; it can be thought
+				 * of as simply the root of the tree.  The
+				 * representation of these internal nodes is
+				 * simply the index of the left child combined
+				 * with the special bits 0xC000 to distingush
+				 * the entry from direct mapping and leaf node
+				 * entries.
+				 */
+				do {
+					/* At least one bit remains in the
+					 * codeword, but the current node is an
+					 * unallocated leaf.  Change it to an
+					 * internal node.
+					 */
+					if (decode_table[node_idx] == 0) {
+						decode_table[node_idx] =
+							next_free_tree_slot | 0xC000;
+						decode_table[next_free_tree_slot++] = 0;
+						decode_table[next_free_tree_slot++] = 0;
+					}
+
+					/* Go to the left child if the next bit
+					 * in the codeword is 0; otherwise go to
+					 * the right child.
+					 */
+					node_idx = decode_table[node_idx] & 0x3FFF;
+					--extra_bits;
+					node_idx += (cur_codeword >> extra_bits) & 1;
+				} while (extra_bits != 0);
+
+				/* We've traversed the tree using the entire
+				 * codeword, and we're now at the entry where
+				 * the actual symbol will be stored.  This is
+				 * distinguished from internal nodes by not
+				 * having its high two bits set.
+				 */
+				decode_table[node_idx] = sorted_sym;
+			}
+		}
+	}
+	return 0;
+}
diff --git a/fs/ntfs3/lib/decompress_common.h b/fs/ntfs3/lib/decompress_common.h
new file mode 100644
index 000000000000..66297f398403
--- /dev/null
+++ b/fs/ntfs3/lib/decompress_common.h
@@ -0,0 +1,352 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+/*
+ * decompress_common.h - Code shared by the XPRESS and LZX decompressors
+ *
+ * Copyright (C) 2015 Eric Biggers
+ *
+ * This program is free software: you can redistribute it and/or modify it under
+ * the terms of the GNU General Public License as published by the Free Software
+ * Foundation, either version 2 of the License, or (at your option) any later
+ * version.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+ * FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more
+ * details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <linux/string.h>
+#include <linux/compiler.h>
+#include <linux/types.h>
+#include <linux/slab.h>
+#include <asm/unaligned.h>
+
+
+/* "Force inline" macro (not required, but helpful for performance)  */
+#define forceinline __always_inline
+
+/* Enable whole-word match copying on selected architectures  */
+#if defined(__i386__) || defined(__x86_64__) || defined(__ARM_FEATURE_UNALIGNED)
+#  define FAST_UNALIGNED_ACCESS
+#endif
+
+/* Size of a machine word  */
+#define WORDBYTES (sizeof(size_t))
+
+static forceinline void
+copy_unaligned_word(const void *src, void *dst)
+{
+	put_unaligned(get_unaligned((const size_t *)src), (size_t *)dst);
+}
+
+
+/* Generate a "word" with platform-dependent size whose bytes all contain the
+ * value 'b'.
+ */
+static forceinline size_t repeat_byte(u8 b)
+{
+	size_t v;
+
+	v = b;
+	v |= v << 8;
+	v |= v << 16;
+	v |= v << ((WORDBYTES == 8) ? 32 : 0);
+	return v;
+}
+
+/* Structure that encapsulates a block of in-memory data being interpreted as a
+ * stream of bits, optionally with interwoven literal bytes.  Bits are assumed
+ * to be stored in little endian 16-bit coding units, with the bits ordered high
+ * to low.
+ */
+struct input_bitstream {
+
+	/* Bits that have been read from the input buffer.  The bits are
+	 * left-justified; the next bit is always bit 31.
+	 */
+	u32 bitbuf;
+
+	/* Number of bits currently held in @bitbuf.  */
+	u32 bitsleft;
+
+	/* Pointer to the next byte to be retrieved from the input buffer.  */
+	const u8 *next;
+
+	/* Pointer to just past the end of the input buffer.  */
+	const u8 *end;
+};
+
+/* Initialize a bitstream to read from the specified input buffer.  */
+static forceinline void init_input_bitstream(struct input_bitstream *is,
+					     const void *buffer, u32 size)
+{
+	is->bitbuf = 0;
+	is->bitsleft = 0;
+	is->next = buffer;
+	is->end = is->next + size;
+}
+
+/* Ensure the bit buffer variable for the bitstream contains at least @num_bits
+ * bits.  Following this, bitstream_peek_bits() and/or bitstream_remove_bits()
+ * may be called on the bitstream to peek or remove up to @num_bits bits.  Note
+ * that @num_bits must be <= 16.
+ */
+static forceinline void bitstream_ensure_bits(struct input_bitstream *is,
+					      u32 num_bits)
+{
+	if (is->bitsleft < num_bits) {
+		if (is->end - is->next >= 2) {
+			is->bitbuf |= (u32)get_unaligned_le16(is->next)
+					<< (16 - is->bitsleft);
+			is->next += 2;
+		}
+		is->bitsleft += 16;
+	}
+}
+
+/* Return the next @num_bits bits from the bitstream, without removing them.
+ * There must be at least @num_bits remaining in the buffer variable, from a
+ * previous call to bitstream_ensure_bits().
+ */
+static forceinline u32
+bitstream_peek_bits(const struct input_bitstream *is, const u32 num_bits)
+{
+	return (is->bitbuf >> 1) >> (sizeof(is->bitbuf) * 8 - num_bits - 1);
+}
+
+/* Remove @num_bits from the bitstream.  There must be at least @num_bits
+ * remaining in the buffer variable, from a previous call to
+ * bitstream_ensure_bits().
+ */
+static forceinline void
+bitstream_remove_bits(struct input_bitstream *is, u32 num_bits)
+{
+	is->bitbuf <<= num_bits;
+	is->bitsleft -= num_bits;
+}
+
+/* Remove and return @num_bits bits from the bitstream.  There must be at least
+ * @num_bits remaining in the buffer variable, from a previous call to
+ * bitstream_ensure_bits().
+ */
+static forceinline u32
+bitstream_pop_bits(struct input_bitstream *is, u32 num_bits)
+{
+	u32 bits = bitstream_peek_bits(is, num_bits);
+
+	bitstream_remove_bits(is, num_bits);
+	return bits;
+}
+
+/* Read and return the next @num_bits bits from the bitstream.  */
+static forceinline u32
+bitstream_read_bits(struct input_bitstream *is, u32 num_bits)
+{
+	bitstream_ensure_bits(is, num_bits);
+	return bitstream_pop_bits(is, num_bits);
+}
+
+/* Read and return the next literal byte embedded in the bitstream.  */
+static forceinline u8
+bitstream_read_byte(struct input_bitstream *is)
+{
+	if (unlikely(is->end == is->next))
+		return 0;
+	return *is->next++;
+}
+
+/* Read and return the next 16-bit integer embedded in the bitstream.  */
+static forceinline u16
+bitstream_read_u16(struct input_bitstream *is)
+{
+	u16 v;
+
+	if (unlikely(is->end - is->next < 2))
+		return 0;
+	v = get_unaligned_le16(is->next);
+	is->next += 2;
+	return v;
+}
+
+/* Read and return the next 32-bit integer embedded in the bitstream.  */
+static forceinline u32
+bitstream_read_u32(struct input_bitstream *is)
+{
+	u32 v;
+
+	if (unlikely(is->end - is->next < 4))
+		return 0;
+	v = get_unaligned_le32(is->next);
+	is->next += 4;
+	return v;
+}
+
+/* Read into @dst_buffer an array of literal bytes embedded in the bitstream.
+ * Return either a pointer to the byte past the last written, or NULL if the
+ * read overflows the input buffer.
+ */
+static forceinline void *bitstream_read_bytes(struct input_bitstream *is,
+					      void *dst_buffer, size_t count)
+{
+	if ((size_t)(is->end - is->next) < count)
+		return NULL;
+	memcpy(dst_buffer, is->next, count);
+	is->next += count;
+	return (u8 *)dst_buffer + count;
+}
+
+/* Align the input bitstream on a coding-unit boundary.  */
+static forceinline void bitstream_align(struct input_bitstream *is)
+{
+	is->bitsleft = 0;
+	is->bitbuf = 0;
+}
+
+extern int make_huffman_decode_table(u16 decode_table[], const u32 num_syms,
+				     const u32 num_bits, const u8 lens[],
+				     const u32 max_codeword_len,
+				     u16 working_space[]);
+
+
+/* Reads and returns the next Huffman-encoded symbol from a bitstream.  If the
+ * input data is exhausted, the Huffman symbol is decoded as if the missing bits
+ * are all zeroes.
+ */
+static forceinline u32 read_huffsym(struct input_bitstream *istream,
+					 const u16 decode_table[],
+					 u32 table_bits,
+					 u32 max_codeword_len)
+{
+	u32 entry;
+	u32 key_bits;
+
+	bitstream_ensure_bits(istream, max_codeword_len);
+
+	/* Index the decode table by the next table_bits bits of the input.  */
+	key_bits = bitstream_peek_bits(istream, table_bits);
+	entry = decode_table[key_bits];
+	if (entry < 0xC000) {
+		/* Fast case: The decode table directly provided the
+		 * symbol and codeword length.  The low 11 bits are the
+		 * symbol, and the high 5 bits are the codeword length.
+		 */
+		bitstream_remove_bits(istream, entry >> 11);
+		return entry & 0x7FF;
+	}
+	/* Slow case: The codeword for the symbol is longer than
+	 * table_bits, so the symbol does not have an entry
+	 * directly in the first (1 << table_bits) entries of the
+	 * decode table.  Traverse the appropriate binary tree
+	 * bit-by-bit to decode the symbol.
+	 */
+	bitstream_remove_bits(istream, table_bits);
+	do {
+		key_bits = (entry & 0x3FFF) + bitstream_pop_bits(istream, 1);
+	} while ((entry = decode_table[key_bits]) >= 0xC000);
+	return entry;
+}
+
+/*
+ * Copy an LZ77 match at (dst - offset) to dst.
+ *
+ * The length and offset must be already validated --- that is, (dst - offset)
+ * can't underrun the output buffer, and (dst + length) can't overrun the output
+ * buffer.  Also, the length cannot be 0.
+ *
+ * @bufend points to the byte past the end of the output buffer.  This function
+ * won't write any data beyond this position.
+ *
+ * Returns dst + length.
+ */
+static forceinline u8 *lz_copy(u8 *dst, u32 length, u32 offset, const u8 *bufend,
+			       u32 min_length)
+{
+	const u8 *src = dst - offset;
+
+	/*
+	 * Try to copy one machine word at a time.  On i386 and x86_64 this is
+	 * faster than copying one byte at a time, unless the data is
+	 * near-random and all the matches have very short lengths.  Note that
+	 * since this requires unaligned memory accesses, it won't necessarily
+	 * be faster on every architecture.
+	 *
+	 * Also note that we might copy more than the length of the match.  For
+	 * example, if a word is 8 bytes and the match is of length 5, then
+	 * we'll simply copy 8 bytes.  This is okay as long as we don't write
+	 * beyond the end of the output buffer, hence the check for (bufend -
+	 * end >= WORDBYTES - 1).
+	 */
+#ifdef FAST_UNALIGNED_ACCESS
+	u8 * const end = dst + length;
+
+	if (bufend - end >= (ptrdiff_t)(WORDBYTES - 1)) {
+
+		if (offset >= WORDBYTES) {
+			/* The source and destination words don't overlap.  */
+
+			/* To improve branch prediction, one iteration of this
+			 * loop is unrolled.  Most matches are short and will
+			 * fail the first check.  But if that check passes, then
+			 * it becomes increasing likely that the match is long
+			 * and we'll need to continue copying.
+			 */
+
+			copy_unaligned_word(src, dst);
+			src += WORDBYTES;
+			dst += WORDBYTES;
+
+			if (dst < end) {
+				do {
+					copy_unaligned_word(src, dst);
+					src += WORDBYTES;
+					dst += WORDBYTES;
+				} while (dst < end);
+			}
+			return end;
+		} else if (offset == 1) {
+
+			/* Offset 1 matches are equivalent to run-length
+			 * encoding of the previous byte.  This case is common
+			 * if the data contains many repeated bytes.
+			 */
+			size_t v = repeat_byte(*(dst - 1));
+
+			do {
+				put_unaligned(v, (size_t *)dst);
+				src += WORDBYTES;
+				dst += WORDBYTES;
+			} while (dst < end);
+			return end;
+		}
+		/*
+		 * We don't bother with special cases for other 'offset <
+		 * WORDBYTES', which are usually rarer than 'offset == 1'.  Extra
+		 * checks will just slow things down.  Actually, it's possible
+		 * to handle all the 'offset < WORDBYTES' cases using the same
+		 * code, but it still becomes more complicated doesn't seem any
+		 * faster overall; it definitely slows down the more common
+		 * 'offset == 1' case.
+		 */
+	}
+#endif /* FAST_UNALIGNED_ACCESS */
+
+	/* Fall back to a bytewise copy.  */
+
+	if (min_length >= 2) {
+		*dst++ = *src++;
+		length--;
+	}
+	if (min_length >= 3) {
+		*dst++ = *src++;
+		length--;
+	}
+	do {
+		*dst++ = *src++;
+	} while (--length);
+
+	return dst;
+}
diff --git a/fs/ntfs3/lib/lib.h b/fs/ntfs3/lib/lib.h
new file mode 100644
index 000000000000..f508fbad2e71
--- /dev/null
+++ b/fs/ntfs3/lib/lib.h
@@ -0,0 +1,26 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * Adapted for linux kernel by Alexander Mamaev:
+ * - remove implementations of get_unaligned_
+ * - assume GCC is always defined
+ * - ISO C90
+ * - linux kernel code style
+ */
+
+
+/* globals from xpress_decompress.c */
+struct xpress_decompressor *xpress_allocate_decompressor(void);
+void xpress_free_decompressor(struct xpress_decompressor *d);
+int xpress_decompress(struct xpress_decompressor *__restrict d,
+		      const void *__restrict compressed_data,
+		      size_t compressed_size,
+		      void *__restrict uncompressed_data,
+		      size_t uncompressed_size);
+
+/* globals from lzx_decompress.c */
+struct lzx_decompressor *lzx_allocate_decompressor(void);
+void lzx_free_decompressor(struct lzx_decompressor *d);
+int lzx_decompress(struct lzx_decompressor *__restrict d,
+		   const void *__restrict compressed_data,
+		   size_t compressed_size, void *__restrict uncompressed_data,
+		   size_t uncompressed_size);
diff --git a/fs/ntfs3/lib/lzx_decompress.c b/fs/ntfs3/lib/lzx_decompress.c
new file mode 100644
index 000000000000..77a381a693d1
--- /dev/null
+++ b/fs/ntfs3/lib/lzx_decompress.c
@@ -0,0 +1,683 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * lzx_decompress.c - A decompressor for the LZX compression format, which can
+ * be used in "System Compressed" files.  This is based on the code from wimlib.
+ * This code only supports a window size (dictionary size) of 32768 bytes, since
+ * this is the only size used in System Compression.
+ *
+ * Copyright (C) 2015 Eric Biggers
+ *
+ * This program is free software: you can redistribute it and/or modify it under
+ * the terms of the GNU General Public License as published by the Free Software
+ * Foundation, either version 2 of the License, or (at your option) any later
+ * version.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+ * FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more
+ * details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "decompress_common.h"
+#include "lib.h"
+
+/* Number of literal byte values  */
+#define LZX_NUM_CHARS			256
+
+/* The smallest and largest allowed match lengths  */
+#define LZX_MIN_MATCH_LEN		2
+#define LZX_MAX_MATCH_LEN		257
+
+/* Number of distinct match lengths that can be represented  */
+#define LZX_NUM_LENS			(LZX_MAX_MATCH_LEN - LZX_MIN_MATCH_LEN + 1)
+
+/* Number of match lengths for which no length symbol is required  */
+#define LZX_NUM_PRIMARY_LENS		7
+#define LZX_NUM_LEN_HEADERS		(LZX_NUM_PRIMARY_LENS + 1)
+
+/* Valid values of the 3-bit block type field  */
+#define LZX_BLOCKTYPE_VERBATIM		1
+#define LZX_BLOCKTYPE_ALIGNED		2
+#define LZX_BLOCKTYPE_UNCOMPRESSED	3
+
+/* Number of offset slots for a window size of 32768  */
+#define LZX_NUM_OFFSET_SLOTS		30
+
+/* Number of symbols in the main code for a window size of 32768  */
+#define LZX_MAINCODE_NUM_SYMBOLS	\
+	(LZX_NUM_CHARS + (LZX_NUM_OFFSET_SLOTS * LZX_NUM_LEN_HEADERS))
+
+/* Number of symbols in the length code  */
+#define LZX_LENCODE_NUM_SYMBOLS		(LZX_NUM_LENS - LZX_NUM_PRIMARY_LENS)
+
+/* Number of symbols in the precode  */
+#define LZX_PRECODE_NUM_SYMBOLS		20
+
+/* Number of bits in which each precode codeword length is represented  */
+#define LZX_PRECODE_ELEMENT_SIZE	4
+
+/* Number of low-order bits of each match offset that are entropy-encoded in
+ * aligned offset blocks
+ */
+#define LZX_NUM_ALIGNED_OFFSET_BITS	3
+
+/* Number of symbols in the aligned offset code  */
+#define LZX_ALIGNEDCODE_NUM_SYMBOLS	(1 << LZX_NUM_ALIGNED_OFFSET_BITS)
+
+/* Mask for the match offset bits that are entropy-encoded in aligned offset
+ * blocks
+ */
+#define LZX_ALIGNED_OFFSET_BITMASK	((1 << LZX_NUM_ALIGNED_OFFSET_BITS) - 1)
+
+/* Number of bits in which each aligned offset codeword length is represented  */
+#define LZX_ALIGNEDCODE_ELEMENT_SIZE	3
+
+/* Maximum lengths (in bits) of the codewords in each Huffman code  */
+#define LZX_MAX_MAIN_CODEWORD_LEN	16
+#define LZX_MAX_LEN_CODEWORD_LEN	16
+#define LZX_MAX_PRE_CODEWORD_LEN	((1 << LZX_PRECODE_ELEMENT_SIZE) - 1)
+#define LZX_MAX_ALIGNED_CODEWORD_LEN	((1 << LZX_ALIGNEDCODE_ELEMENT_SIZE) - 1)
+
+/* The default "filesize" value used in pre/post-processing.  In the LZX format
+ * used in cabinet files this value must be given to the decompressor, whereas
+ * in the LZX format used in WIM files and system-compressed files this value is
+ * fixed at 12000000.
+ */
+#define LZX_DEFAULT_FILESIZE		12000000
+
+/* Assumed block size when the encoded block size begins with a 0 bit.  */
+#define LZX_DEFAULT_BLOCK_SIZE		32768
+
+/* Number of offsets in the recent (or "repeat") offsets queue.  */
+#define LZX_NUM_RECENT_OFFSETS		3
+
+/* These values are chosen for fast decompression.  */
+#define LZX_MAINCODE_TABLEBITS		11
+#define LZX_LENCODE_TABLEBITS		10
+#define LZX_PRECODE_TABLEBITS		6
+#define LZX_ALIGNEDCODE_TABLEBITS	7
+
+#define LZX_READ_LENS_MAX_OVERRUN	50
+
+/* Mapping: offset slot => first match offset that uses that offset slot.
+ */
+static const u32 lzx_offset_slot_base[LZX_NUM_OFFSET_SLOTS + 1] = {
+	0,	1,	2,	3,	4,	/* 0  --- 4  */
+	6,	8,	12,	16,	24,	/* 5  --- 9  */
+	32,	48,	64,	96,	128,	/* 10 --- 14 */
+	192,	256,	384,	512,	768,	/* 15 --- 19 */
+	1024,	1536,	2048,	3072,	4096,   /* 20 --- 24 */
+	6144,	8192,	12288,	16384,	24576,	/* 25 --- 29 */
+	32768,					/* extra     */
+};
+
+/* Mapping: offset slot => how many extra bits must be read and added to the
+ * corresponding offset slot base to decode the match offset.
+ */
+static const u8 lzx_extra_offset_bits[LZX_NUM_OFFSET_SLOTS] = {
+	0,	0,	0,	0,	1,
+	1,	2,	2,	3,	3,
+	4,	4,	5,	5,	6,
+	6,	7,	7,	8,	8,
+	9,	9,	10,	10,	11,
+	11,	12,	12,	13,	13,
+};
+
+/* Reusable heap-allocated memory for LZX decompression  */
+struct lzx_decompressor {
+
+	/* Huffman decoding tables, and arrays that map symbols to codeword
+	 * lengths
+	 */
+
+	u16 maincode_decode_table[(1 << LZX_MAINCODE_TABLEBITS) +
+					(LZX_MAINCODE_NUM_SYMBOLS * 2)];
+	u8 maincode_lens[LZX_MAINCODE_NUM_SYMBOLS + LZX_READ_LENS_MAX_OVERRUN];
+
+
+	u16 lencode_decode_table[(1 << LZX_LENCODE_TABLEBITS) +
+					(LZX_LENCODE_NUM_SYMBOLS * 2)];
+	u8 lencode_lens[LZX_LENCODE_NUM_SYMBOLS + LZX_READ_LENS_MAX_OVERRUN];
+
+
+	u16 alignedcode_decode_table[(1 << LZX_ALIGNEDCODE_TABLEBITS) +
+					(LZX_ALIGNEDCODE_NUM_SYMBOLS * 2)];
+	u8 alignedcode_lens[LZX_ALIGNEDCODE_NUM_SYMBOLS];
+
+	u16 precode_decode_table[(1 << LZX_PRECODE_TABLEBITS) +
+				 (LZX_PRECODE_NUM_SYMBOLS * 2)];
+	u8 precode_lens[LZX_PRECODE_NUM_SYMBOLS];
+
+	/* Temporary space for make_huffman_decode_table()  */
+	u16 working_space[2 * (1 + LZX_MAX_MAIN_CODEWORD_LEN) +
+			  LZX_MAINCODE_NUM_SYMBOLS];
+};
+
+static void undo_e8_translation(void *target, s32 input_pos)
+{
+	s32 abs_offset, rel_offset;
+
+	abs_offset = get_unaligned_le32(target);
+	if (abs_offset >= 0) {
+		if (abs_offset < LZX_DEFAULT_FILESIZE) {
+			/* "good translation" */
+			rel_offset = abs_offset - input_pos;
+			put_unaligned_le32(rel_offset, target);
+		}
+	} else {
+		if (abs_offset >= -input_pos) {
+			/* "compensating translation" */
+			rel_offset = abs_offset + LZX_DEFAULT_FILESIZE;
+			put_unaligned_le32(rel_offset, target);
+		}
+	}
+}
+
+/*
+ * Undo the 'E8' preprocessing used in LZX.  Before compression, the
+ * uncompressed data was preprocessed by changing the targets of suspected x86
+ * CALL instructions from relative offsets to absolute offsets.  After
+ * match/literal decoding, the decompressor must undo the translation.
+ */
+static void lzx_postprocess(u8 *data, u32 size)
+{
+	/*
+	 * A worthwhile optimization is to push the end-of-buffer check into the
+	 * relatively rare E8 case.  This is possible if we replace the last six
+	 * bytes of data with E8 bytes; then we are guaranteed to hit an E8 byte
+	 * before reaching end-of-buffer.  In addition, this scheme guarantees
+	 * that no translation can begin following an E8 byte in the last 10
+	 * bytes because a 4-byte offset containing E8 as its high byte is a
+	 * large negative number that is not valid for translation.  That is
+	 * exactly what we need.
+	 */
+	u8 *tail;
+	u8 saved_bytes[6];
+	u8 *p;
+
+	if (size <= 10)
+		return;
+
+	tail = &data[size - 6];
+	memcpy(saved_bytes, tail, 6);
+	memset(tail, 0xE8, 6);
+	p = data;
+	for (;;) {
+		while (*p != 0xE8)
+			p++;
+		if (p >= tail)
+			break;
+		undo_e8_translation(p + 1, p - data);
+		p += 5;
+	}
+	memcpy(tail, saved_bytes, 6);
+}
+
+/* Read a Huffman-encoded symbol using the precode.  */
+static forceinline u32 read_presym(const struct lzx_decompressor *d,
+					struct input_bitstream *is)
+{
+	return read_huffsym(is, d->precode_decode_table,
+			    LZX_PRECODE_TABLEBITS, LZX_MAX_PRE_CODEWORD_LEN);
+}
+
+/* Read a Huffman-encoded symbol using the main code.  */
+static forceinline u32 read_mainsym(const struct lzx_decompressor *d,
+					 struct input_bitstream *is)
+{
+	return read_huffsym(is, d->maincode_decode_table,
+			    LZX_MAINCODE_TABLEBITS, LZX_MAX_MAIN_CODEWORD_LEN);
+}
+
+/* Read a Huffman-encoded symbol using the length code.  */
+static forceinline u32 read_lensym(const struct lzx_decompressor *d,
+					struct input_bitstream *is)
+{
+	return read_huffsym(is, d->lencode_decode_table,
+			    LZX_LENCODE_TABLEBITS, LZX_MAX_LEN_CODEWORD_LEN);
+}
+
+/* Read a Huffman-encoded symbol using the aligned offset code.  */