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Message-ID: <20210128090455.3576502-7-almaz.alexandrovich@paragon-software.com>
Date: Thu, 28 Jan 2021 12:04:51 +0300
From: Konstantin Komarov <almaz.alexandrovich@...agon-software.com>
To: <linux-fsdevel@...r.kernel.org>
CC: <viro@...iv.linux.org.uk>, <linux-kernel@...r.kernel.org>,
<pali@...nel.org>, <dsterba@...e.cz>, <aaptel@...e.com>,
<willy@...radead.org>, <rdunlap@...radead.org>, <joe@...ches.com>,
<mark@...mstone.com>, <nborisov@...e.com>,
<linux-ntfs-dev@...ts.sourceforge.net>, <anton@...era.com>,
<dan.carpenter@...cle.com>, <hch@....de>, <ebiggers@...nel.org>,
<andy.lavr@...il.com>,
Konstantin Komarov <almaz.alexandrovich@...agon-software.com>
Subject: [PATCH v19 06/10] 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@...agon-software.com>
---
fs/ntfs3/lib/decompress_common.c | 332 +++++++++++++++
fs/ntfs3/lib/decompress_common.h | 352 ++++++++++++++++
fs/ntfs3/lib/lib.h | 26 ++
fs/ntfs3/lib/lzx_decompress.c | 683 +++++++++++++++++++++++++++++++
fs/ntfs3/lib/xpress_decompress.c | 155 +++++++
fs/ntfs3/lznt.c | 452 ++++++++++++++++++++
6 files changed, 2000 insertions(+)
create mode 100644 fs/ntfs3/lib/decompress_common.c
create mode 100644 fs/ntfs3/lib/decompress_common.h
create mode 100644 fs/ntfs3/lib/lib.h
create mode 100644 fs/ntfs3/lib/lzx_decompress.c
create mode 100644 fs/ntfs3/lib/xpress_decompress.c
create mode 100644 fs/ntfs3/lznt.c
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. */
+static forceinline u32 read_alignedsym(const struct lzx_decompressor *d,
+ struct input_bitstream *is)
+{
+ return read_huffsym(is, d->alignedcode_decode_table,
+ LZX_ALIGNEDCODE_TABLEBITS,
+ LZX_MAX_ALIGNED_CODEWORD_LEN);
+}
+
+/*
+ * Read the precode from the compressed input bitstream, then use it to decode
+ * @num_lens codeword length values.
+ *
+ * @is: The input bitstream.
+ *
+ * @lens: An array that contains the length values from the previous time
+ * the codeword lengths for this Huffman code were read, or all 0's
+ * if this is the first time. This array must have at least
+ * (@num_lens + LZX_READ_LENS_MAX_OVERRUN) entries.
+ *
+ * @num_lens: Number of length values to decode.
+ *
+ * Returns 0 on success, or -1 if the data was invalid.
+ */
+static int lzx_read_codeword_lens(struct lzx_decompressor *d,
+ struct input_bitstream *is,
+ u8 *lens, u32 num_lens)
+{
+ u8 *len_ptr = lens;
+ u8 *lens_end = lens + num_lens;
+ int i;
+
+ /* Read the lengths of the precode codewords. These are given
+ * explicitly.
+ */
+ for (i = 0; i < LZX_PRECODE_NUM_SYMBOLS; i++) {
+ d->precode_lens[i] =
+ bitstream_read_bits(is, LZX_PRECODE_ELEMENT_SIZE);
+ }
+
+ /* Make the decoding table for the precode. */
+ if (make_huffman_decode_table(d->precode_decode_table,
+ LZX_PRECODE_NUM_SYMBOLS,
+ LZX_PRECODE_TABLEBITS,
+ d->precode_lens,
+ LZX_MAX_PRE_CODEWORD_LEN,
+ d->working_space))
+ return -1;
+
+ /* Decode the codeword lengths. */
+ do {
+ u32 presym;
+ u8 len;
+
+ /* Read the next precode symbol. */
+ presym = read_presym(d, is);
+ if (presym < 17) {
+ /* Difference from old length */
+ len = *len_ptr - presym;
+ if ((s8)len < 0)
+ len += 17;
+ *len_ptr++ = len;
+ } else {
+ /* Special RLE values */
+
+ u32 run_len;
+
+ if (presym == 17) {
+ /* Run of 0's */
+ run_len = 4 + bitstream_read_bits(is, 4);
+ len = 0;
+ } else if (presym == 18) {
+ /* Longer run of 0's */
+ run_len = 20 + bitstream_read_bits(is, 5);
+ len = 0;
+ } else {
+ /* Run of identical lengths */
+ run_len = 4 + bitstream_read_bits(is, 1);
+ presym = read_presym(d, is);
+ if (presym > 17)
+ return -1;
+ len = *len_ptr - presym;
+ if ((s8)len < 0)
+ len += 17;
+ }
+
+ do {
+ *len_ptr++ = len;
+ } while (--run_len);
+ /* Worst case overrun is when presym == 18,
+ * run_len == 20 + 31, and only 1 length was remaining.
+ * So LZX_READ_LENS_MAX_OVERRUN == 50.
+ *
+ * Overrun while reading the first half of maincode_lens
+ * can corrupt the previous values in the second half.
+ * This doesn't really matter because the resulting
+ * lengths will still be in range, and data that
+ * generates overruns is invalid anyway.
+ */
+ }
+ } while (len_ptr < lens_end);
+
+ return 0;
+}
+
+/*
+ * Read the header of an LZX block and save the block type and (uncompressed)
+ * size in *block_type_ret and *block_size_ret, respectively.
+ *
+ * If the block is compressed, also update the Huffman decode @tables with the
+ * new Huffman codes. If the block is uncompressed, also update the match
+ * offset @queue with the new match offsets.
+ *
+ * Return 0 on success, or -1 if the data was invalid.
+ */
+static int lzx_read_block_header(struct lzx_decompressor *d,
+ struct input_bitstream *is,
+ int *block_type_ret,
+ u32 *block_size_ret,
+ u32 recent_offsets[])
+{
+ int block_type;
+ u32 block_size;
+ int i;
+
+ bitstream_ensure_bits(is, 4);
+
+ /* The first three bits tell us what kind of block it is, and should be
+ * one of the LZX_BLOCKTYPE_* values.
+ */
+ block_type = bitstream_pop_bits(is, 3);
+
+ /* Read the block size. */
+ if (bitstream_pop_bits(is, 1)) {
+ block_size = LZX_DEFAULT_BLOCK_SIZE;
+ } else {
+ block_size = 0;
+ block_size |= bitstream_read_bits(is, 8);
+ block_size <<= 8;
+ block_size |= bitstream_read_bits(is, 8);
+ }
+
+ switch (block_type) {
+
+ case LZX_BLOCKTYPE_ALIGNED:
+
+ /* Read the aligned offset code and prepare its decode table.
+ */
+
+ for (i = 0; i < LZX_ALIGNEDCODE_NUM_SYMBOLS; i++) {
+ d->alignedcode_lens[i] =
+ bitstream_read_bits(is,
+ LZX_ALIGNEDCODE_ELEMENT_SIZE);
+ }
+
+ if (make_huffman_decode_table(d->alignedcode_decode_table,
+ LZX_ALIGNEDCODE_NUM_SYMBOLS,
+ LZX_ALIGNEDCODE_TABLEBITS,
+ d->alignedcode_lens,
+ LZX_MAX_ALIGNED_CODEWORD_LEN,
+ d->working_space))
+ return -1;
+
+ /* Fall though, since the rest of the header for aligned offset
+ * blocks is the same as that for verbatim blocks.
+ */
+ fallthrough;
+
+ case LZX_BLOCKTYPE_VERBATIM:
+
+ /* Read the main code and prepare its decode table.
+ *
+ * Note that the codeword lengths in the main code are encoded
+ * in two parts: one part for literal symbols, and one part for
+ * match symbols.
+ */
+
+ if (lzx_read_codeword_lens(d, is, d->maincode_lens,
+ LZX_NUM_CHARS))
+ return -1;
+
+ if (lzx_read_codeword_lens(d, is,
+ d->maincode_lens + LZX_NUM_CHARS,
+ LZX_MAINCODE_NUM_SYMBOLS - LZX_NUM_CHARS))
+ return -1;
+
+ if (make_huffman_decode_table(d->maincode_decode_table,
+ LZX_MAINCODE_NUM_SYMBOLS,
+ LZX_MAINCODE_TABLEBITS,
+ d->maincode_lens,
+ LZX_MAX_MAIN_CODEWORD_LEN,
+ d->working_space))
+ return -1;
+
+ /* Read the length code and prepare its decode table. */
+
+ if (lzx_read_codeword_lens(d, is, d->lencode_lens,
+ LZX_LENCODE_NUM_SYMBOLS))
+ return -1;
+
+ if (make_huffman_decode_table(d->lencode_decode_table,
+ LZX_LENCODE_NUM_SYMBOLS,
+ LZX_LENCODE_TABLEBITS,
+ d->lencode_lens,
+ LZX_MAX_LEN_CODEWORD_LEN,
+ d->working_space))
+ return -1;
+
+ break;
+
+ case LZX_BLOCKTYPE_UNCOMPRESSED:
+
+ /* Before reading the three recent offsets from the uncompressed
+ * block header, the stream must be aligned on a 16-bit
+ * boundary. But if the stream is *already* aligned, then the
+ * next 16 bits must be discarded.
+ */
+ bitstream_ensure_bits(is, 1);
+ bitstream_align(is);
+
+ recent_offsets[0] = bitstream_read_u32(is);
+ recent_offsets[1] = bitstream_read_u32(is);
+ recent_offsets[2] = bitstream_read_u32(is);
+
+ /* Offsets of 0 are invalid. */
+ if (recent_offsets[0] == 0 || recent_offsets[1] == 0 ||
+ recent_offsets[2] == 0)
+ return -1;
+ break;
+
+ default:
+ /* Unrecognized block type. */
+ return -1;
+ }
+
+ *block_type_ret = block_type;
+ *block_size_ret = block_size;
+ return 0;
+}
+
+/* Decompress a block of LZX-compressed data. */
+static int lzx_decompress_block(const struct lzx_decompressor *d,
+ struct input_bitstream *is,
+ int block_type, u32 block_size,
+ u8 * const out_begin, u8 *out_next,
+ u32 recent_offsets[])
+{
+ u8 * const block_end = out_next + block_size;
+ u32 ones_if_aligned = 0U - (block_type == LZX_BLOCKTYPE_ALIGNED);
+
+ do {
+ u32 mainsym;
+ u32 match_len;
+ u32 match_offset;
+ u32 offset_slot;
+ u32 num_extra_bits;
+
+ mainsym = read_mainsym(d, is);
+ if (mainsym < LZX_NUM_CHARS) {
+ /* Literal */
+ *out_next++ = mainsym;
+ continue;
+ }
+
+ /* Match */
+
+ /* Decode the length header and offset slot. */
+ mainsym -= LZX_NUM_CHARS;
+ match_len = mainsym % LZX_NUM_LEN_HEADERS;
+ offset_slot = mainsym / LZX_NUM_LEN_HEADERS;
+
+ /* If needed, read a length symbol to decode the full length. */
+ if (match_len == LZX_NUM_PRIMARY_LENS)
+ match_len += read_lensym(d, is);
+ match_len += LZX_MIN_MATCH_LEN;
+
+ if (offset_slot < LZX_NUM_RECENT_OFFSETS) {
+ /* Repeat offset */
+
+ /* Note: This isn't a real LRU queue, since using the R2
+ * offset doesn't bump the R1 offset down to R2. This
+ * quirk allows all 3 recent offsets to be handled by
+ * the same code. (For R0, the swap is a no-op.)
+ */
+ match_offset = recent_offsets[offset_slot];
+ recent_offsets[offset_slot] = recent_offsets[0];
+ recent_offsets[0] = match_offset;
+ } else {
+ /* Explicit offset */
+
+ /* Look up the number of extra bits that need to be read
+ * to decode offsets with this offset slot.
+ */
+ num_extra_bits = lzx_extra_offset_bits[offset_slot];
+
+ /* Start with the offset slot base value. */
+ match_offset = lzx_offset_slot_base[offset_slot];
+
+ /* In aligned offset blocks, the low-order 3 bits of
+ * each offset are encoded using the aligned offset
+ * code. Otherwise, all the extra bits are literal.
+ */
+
+ if ((num_extra_bits & ones_if_aligned) >= LZX_NUM_ALIGNED_OFFSET_BITS) {
+ match_offset +=
+ bitstream_read_bits(is, num_extra_bits -
+ LZX_NUM_ALIGNED_OFFSET_BITS)
+ << LZX_NUM_ALIGNED_OFFSET_BITS;
+ match_offset += read_alignedsym(d, is);
+ } else {
+ match_offset += bitstream_read_bits(is, num_extra_bits);
+ }
+
+ /* Adjust the offset. */
+ match_offset -= (LZX_NUM_RECENT_OFFSETS - 1);
+
+ /* Update the recent offsets. */
+ recent_offsets[2] = recent_offsets[1];
+ recent_offsets[1] = recent_offsets[0];
+ recent_offsets[0] = match_offset;
+ }
+
+ /* Validate the match, then copy it to the current position. */
+
+ if (match_len > (size_t)(block_end - out_next))
+ return -1;
+
+ if (match_offset > (size_t)(out_next - out_begin))
+ return -1;
+
+ out_next = lz_copy(out_next, match_len, match_offset,
+ block_end, LZX_MIN_MATCH_LEN);
+
+ } while (out_next != block_end);
+
+ return 0;
+}
+
+/*
+ * lzx_allocate_decompressor - Allocate an LZX decompressor
+ *
+ * Return the pointer to the decompressor on success, or return NULL and set
+ * errno on failure.
+ */
+struct lzx_decompressor *lzx_allocate_decompressor(void)
+{
+ return kmalloc(sizeof(struct lzx_decompressor), GFP_NOFS);
+}
+
+/*
+ * lzx_decompress - Decompress a buffer of LZX-compressed data
+ *
+ * @decompressor: A decompressor allocated with lzx_allocate_decompressor()
+ * @compressed_data: The buffer of data to decompress
+ * @compressed_size: Number of bytes of compressed data
+ * @uncompressed_data: The buffer in which to store the decompressed data
+ * @uncompressed_size: The number of bytes the data decompresses into
+ *
+ * Return 0 on success, or return -1 and set errno on failure.
+ */
+int lzx_decompress(struct lzx_decompressor *decompressor,
+ const void *compressed_data, size_t compressed_size,
+ void *uncompressed_data, size_t uncompressed_size)
+{
+ struct lzx_decompressor *d = decompressor;
+ u8 * const out_begin = uncompressed_data;
+ u8 *out_next = out_begin;
+ u8 * const out_end = out_begin + uncompressed_size;
+ struct input_bitstream is;
+ u32 recent_offsets[LZX_NUM_RECENT_OFFSETS] = {1, 1, 1};
+ int e8_status = 0;
+
+ init_input_bitstream(&is, compressed_data, compressed_size);
+
+ /* Codeword lengths begin as all 0's for delta encoding purposes. */
+ memset(d->maincode_lens, 0, LZX_MAINCODE_NUM_SYMBOLS);
+ memset(d->lencode_lens, 0, LZX_LENCODE_NUM_SYMBOLS);
+
+ /* Decompress blocks until we have all the uncompressed data. */
+
+ while (out_next != out_end) {
+ int block_type;
+ u32 block_size;
+
+ if (lzx_read_block_header(d, &is, &block_type, &block_size,
+ recent_offsets))
+ goto invalid;
+
+ if (block_size < 1 || block_size > (size_t)(out_end - out_next))
+ goto invalid;
+
+ if (block_type != LZX_BLOCKTYPE_UNCOMPRESSED) {
+
+ /* Compressed block */
+
+ if (lzx_decompress_block(d,
+ &is,
+ block_type,
+ block_size,
+ out_begin,
+ out_next,
+ recent_offsets))
+ goto invalid;
+
+ e8_status |= d->maincode_lens[0xe8];
+ out_next += block_size;
+ } else {
+ /* Uncompressed block */
+
+ out_next = bitstream_read_bytes(&is, out_next,
+ block_size);
+ if (!out_next)
+ goto invalid;
+
+ if (block_size & 1)
+ bitstream_read_byte(&is);
+
+ e8_status = 1;
+ }
+ }
+
+ /* Postprocess the data unless it cannot possibly contain 0xe8 bytes. */
+ if (e8_status)
+ lzx_postprocess(uncompressed_data, uncompressed_size);
+
+ return 0;
+
+invalid:
+ return -1;
+}
+
+/*
+ * lzx_free_decompressor - Free an LZX decompressor
+ *
+ * @decompressor: A decompressor that was allocated with
+ * lzx_allocate_decompressor(), or NULL.
+ */
+void lzx_free_decompressor(struct lzx_decompressor *decompressor)
+{
+ kfree(decompressor);
+}
diff --git a/fs/ntfs3/lib/xpress_decompress.c b/fs/ntfs3/lib/xpress_decompress.c
new file mode 100644
index 000000000000..3d98f36a981e
--- /dev/null
+++ b/fs/ntfs3/lib/xpress_decompress.c
@@ -0,0 +1,155 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * xpress_decompress.c - A decompressor for the XPRESS compression format
+ * (Huffman variant), which can be used in "System Compressed" files. This is
+ * based on the code from wimlib.
+ *
+ * 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"
+
+#define XPRESS_NUM_SYMBOLS 512
+#define XPRESS_MAX_CODEWORD_LEN 15
+#define XPRESS_MIN_MATCH_LEN 3
+
+/* This value is chosen for fast decompression. */
+#define XPRESS_TABLEBITS 12
+
+/* Reusable heap-allocated memory for XPRESS decompression */
+struct xpress_decompressor {
+
+ /* The Huffman decoding table */
+ u16 decode_table[(1 << XPRESS_TABLEBITS) + 2 * XPRESS_NUM_SYMBOLS];
+
+ /* An array that maps symbols to codeword lengths */
+ u8 lens[XPRESS_NUM_SYMBOLS];
+
+ /* Temporary space for make_huffman_decode_table() */
+ u16 working_space[2 * (1 + XPRESS_MAX_CODEWORD_LEN) +
+ XPRESS_NUM_SYMBOLS];
+};
+
+/*
+ * xpress_allocate_decompressor - Allocate an XPRESS decompressor
+ *
+ * Return the pointer to the decompressor on success, or return NULL and set
+ * errno on failure.
+ */
+struct xpress_decompressor *xpress_allocate_decompressor(void)
+{
+ return kmalloc(sizeof(struct xpress_decompressor), GFP_NOFS);
+}
+
+/*
+ * xpress_decompress - Decompress a buffer of XPRESS-compressed data
+ *
+ * @decompressor: A decompressor that was allocated with
+ * xpress_allocate_decompressor()
+ * @compressed_data: The buffer of data to decompress
+ * @compressed_size: Number of bytes of compressed data
+ * @uncompressed_data: The buffer in which to store the decompressed data
+ * @uncompressed_size: The number of bytes the data decompresses into
+ *
+ * Return 0 on success, or return -1 and set errno on failure.
+ */
+int xpress_decompress(struct xpress_decompressor *decompressor,
+ const void *compressed_data, size_t compressed_size,
+ void *uncompressed_data, size_t uncompressed_size)
+{
+ struct xpress_decompressor *d = decompressor;
+ const u8 * const in_begin = compressed_data;
+ u8 * const out_begin = uncompressed_data;
+ u8 *out_next = out_begin;
+ u8 * const out_end = out_begin + uncompressed_size;
+ struct input_bitstream is;
+ u32 i;
+
+ /* Read the Huffman codeword lengths. */
+ if (compressed_size < XPRESS_NUM_SYMBOLS / 2)
+ goto invalid;
+ for (i = 0; i < XPRESS_NUM_SYMBOLS / 2; i++) {
+ d->lens[i*2 + 0] = in_begin[i] & 0xF;
+ d->lens[i*2 + 1] = in_begin[i] >> 4;
+ }
+
+ /* Build a decoding table for the Huffman code. */
+ if (make_huffman_decode_table(d->decode_table, XPRESS_NUM_SYMBOLS,
+ XPRESS_TABLEBITS, d->lens,
+ XPRESS_MAX_CODEWORD_LEN,
+ d->working_space))
+ goto invalid;
+
+ /* Decode the matches and literals. */
+
+ init_input_bitstream(&is, in_begin + XPRESS_NUM_SYMBOLS / 2,
+ compressed_size - XPRESS_NUM_SYMBOLS / 2);
+
+ while (out_next != out_end) {
+ u32 sym;
+ u32 log2_offset;
+ u32 length;
+ u32 offset;
+
+ sym = read_huffsym(&is, d->decode_table,
+ XPRESS_TABLEBITS, XPRESS_MAX_CODEWORD_LEN);
+ if (sym < 256) {
+ /* Literal */
+ *out_next++ = sym;
+ } else {
+ /* Match */
+ length = sym & 0xf;
+ log2_offset = (sym >> 4) & 0xf;
+
+ bitstream_ensure_bits(&is, 16);
+
+ offset = ((u32)1 << log2_offset) |
+ bitstream_pop_bits(&is, log2_offset);
+
+ if (length == 0xf) {
+ length += bitstream_read_byte(&is);
+ if (length == 0xf + 0xff)
+ length = bitstream_read_u16(&is);
+ }
+ length += XPRESS_MIN_MATCH_LEN;
+
+ if (offset > (size_t)(out_next - out_begin))
+ goto invalid;
+
+ if (length > (size_t)(out_end - out_next))
+ goto invalid;
+
+ out_next = lz_copy(out_next, length, offset, out_end,
+ XPRESS_MIN_MATCH_LEN);
+ }
+ }
+ return 0;
+
+invalid:
+ return -1;
+}
+
+/*
+ * xpress_free_decompressor - Free an XPRESS decompressor
+ *
+ * @decompressor: A decompressor that was allocated with
+ * xpress_allocate_decompressor(), or NULL.
+ */
+void xpress_free_decompressor(struct xpress_decompressor *decompressor)
+{
+ kfree(decompressor);
+}
diff --git a/fs/ntfs3/lznt.c b/fs/ntfs3/lznt.c
new file mode 100644
index 000000000000..73dc108c3204
--- /dev/null
+++ b/fs/ntfs3/lznt.c
@@ -0,0 +1,452 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ *
+ * Copyright (C) 2019-2020 Paragon Software GmbH, All rights reserved.
+ *
+ */
+#include <linux/blkdev.h>
+#include <linux/buffer_head.h>
+#include <linux/fs.h>
+#include <linux/nls.h>
+
+#include "debug.h"
+#include "ntfs.h"
+#include "ntfs_fs.h"
+
+// clang-format off
+/* src buffer is zero */
+#define LZNT_ERROR_ALL_ZEROS 1
+#define LZNT_CHUNK_SIZE 0x1000
+// clang-format on
+
+struct lznt_hash {
+ const u8 *p1;
+ const u8 *p2;
+};
+
+struct lznt {
+ const u8 *unc;
+ const u8 *unc_end;
+ const u8 *best_match;
+ size_t max_len;
+ bool std;
+
+ struct lznt_hash hash[LZNT_CHUNK_SIZE];
+};
+
+static inline size_t get_match_len(const u8 *ptr, const u8 *end, const u8 *prev,
+ size_t max_len)
+{
+ size_t len = 0;
+
+ while (ptr + len < end && ptr[len] == prev[len] && ++len < max_len)
+ ;
+ return len;
+}
+
+static size_t longest_match_std(const u8 *src, struct lznt *ctx)
+{
+ size_t hash_index;
+ size_t len1 = 0, len2 = 0;
+ const u8 **hash;
+
+ hash_index =
+ ((40543U * ((((src[0] << 4) ^ src[1]) << 4) ^ src[2])) >> 4) &
+ (LZNT_CHUNK_SIZE - 1);
+
+ hash = &(ctx->hash[hash_index].p1);
+
+ if (hash[0] >= ctx->unc && hash[0] < src && hash[0][0] == src[0] &&
+ hash[0][1] == src[1] && hash[0][2] == src[2]) {
+ len1 = 3;
+ if (ctx->max_len > 3)
+ len1 += get_match_len(src + 3, ctx->unc_end,
+ hash[0] + 3, ctx->max_len - 3);
+ }
+
+ if (hash[1] >= ctx->unc && hash[1] < src && hash[1][0] == src[0] &&
+ hash[1][1] == src[1] && hash[1][2] == src[2]) {
+ len2 = 3;
+ if (ctx->max_len > 3)
+ len2 += get_match_len(src + 3, ctx->unc_end,
+ hash[1] + 3, ctx->max_len - 3);
+ }
+
+ /* Compare two matches and select the best one */
+ if (len1 < len2) {
+ ctx->best_match = hash[1];
+ len1 = len2;
+ } else {
+ ctx->best_match = hash[0];
+ }
+
+ hash[1] = hash[0];
+ hash[0] = src;
+ return len1;
+}
+
+static size_t longest_match_best(const u8 *src, struct lznt *ctx)
+{
+ size_t max_len;
+ const u8 *ptr;
+
+ if (ctx->unc >= src || !ctx->max_len)
+ return 0;
+
+ max_len = 0;
+ for (ptr = ctx->unc; ptr < src; ++ptr) {
+ size_t len =
+ get_match_len(src, ctx->unc_end, ptr, ctx->max_len);
+ if (len >= max_len) {
+ max_len = len;
+ ctx->best_match = ptr;
+ }
+ }
+
+ return max_len >= 3 ? max_len : 0;
+}
+
+static const size_t s_max_len[] = {
+ 0x1002, 0x802, 0x402, 0x202, 0x102, 0x82, 0x42, 0x22, 0x12,
+};
+
+static const size_t s_max_off[] = {
+ 0x10, 0x20, 0x40, 0x80, 0x100, 0x200, 0x400, 0x800, 0x1000,
+};
+
+static inline u16 make_pair(size_t offset, size_t len, size_t index)
+{
+ return ((offset - 1) << (12 - index)) |
+ ((len - 3) & (((1 << (12 - index)) - 1)));
+}
+
+static inline size_t parse_pair(u16 pair, size_t *offset, size_t index)
+{
+ *offset = 1 + (pair >> (12 - index));
+ return 3 + (pair & ((1 << (12 - index)) - 1));
+}
+
+/*
+ * compress_chunk
+ *
+ * returns one of the three values:
+ * 0 - ok, 'cmpr' contains 'cmpr_chunk_size' bytes of compressed data
+ * 1 - input buffer is full zero
+ * -2 - the compressed buffer is too small to hold the compressed data
+ */
+static inline int compress_chunk(size_t (*match)(const u8 *, struct lznt *),
+ const u8 *unc, const u8 *unc_end, u8 *cmpr,
+ u8 *cmpr_end, size_t *cmpr_chunk_size,
+ struct lznt *ctx)
+{
+ size_t cnt = 0;
+ size_t idx = 0;
+ const u8 *up = unc;
+ u8 *cp = cmpr + 3;
+ u8 *cp2 = cmpr + 2;
+ u8 not_zero = 0;
+ /* Control byte of 8-bit values: ( 0 - means byte as is, 1 - short pair ) */
+ u8 ohdr = 0;
+ u8 *last;
+ u16 t16;
+
+ if (unc + LZNT_CHUNK_SIZE < unc_end)
+ unc_end = unc + LZNT_CHUNK_SIZE;
+
+ last = min(cmpr + LZNT_CHUNK_SIZE + sizeof(short), cmpr_end);
+
+ ctx->unc = unc;
+ ctx->unc_end = unc_end;
+ ctx->max_len = s_max_len[0];
+
+ while (up < unc_end) {
+ size_t max_len;
+
+ while (unc + s_max_off[idx] < up)
+ ctx->max_len = s_max_len[++idx];
+
+ // Find match
+ max_len = up + 3 <= unc_end ? (*match)(up, ctx) : 0;
+
+ if (!max_len) {
+ if (cp >= last)
+ goto NotCompressed;
+ not_zero |= *cp++ = *up++;
+ } else if (cp + 1 >= last) {
+ goto NotCompressed;
+ } else {
+ t16 = make_pair(up - ctx->best_match, max_len, idx);
+ *cp++ = t16;
+ *cp++ = t16 >> 8;
+
+ ohdr |= 1 << cnt;
+ up += max_len;
+ }
+
+ cnt = (cnt + 1) & 7;
+ if (!cnt) {
+ *cp2 = ohdr;
+ ohdr = 0;
+ cp2 = cp;
+ cp += 1;
+ }
+ }
+
+ if (cp2 < last)
+ *cp2 = ohdr;
+ else
+ cp -= 1;
+
+ *cmpr_chunk_size = cp - cmpr;
+
+ t16 = (*cmpr_chunk_size - 3) | 0xB000;
+ cmpr[0] = t16;
+ cmpr[1] = t16 >> 8;
+
+ return not_zero ? 0 : LZNT_ERROR_ALL_ZEROS;
+
+NotCompressed:
+
+ if ((cmpr + LZNT_CHUNK_SIZE + sizeof(short)) > last)
+ return -2;
+
+ /*
+ * Copy non cmpr data
+ * 0x3FFF == ((LZNT_CHUNK_SIZE + 2 - 3) | 0x3000)
+ */
+ cmpr[0] = 0xff;
+ cmpr[1] = 0x3f;
+
+ memcpy(cmpr + sizeof(short), unc, LZNT_CHUNK_SIZE);
+ *cmpr_chunk_size = LZNT_CHUNK_SIZE + sizeof(short);
+
+ return 0;
+}
+
+static inline ssize_t decompress_chunk(u8 *unc, u8 *unc_end, const u8 *cmpr,
+ const u8 *cmpr_end)
+{
+ u8 *up = unc;
+ u8 ch = *cmpr++;
+ size_t bit = 0;
+ size_t index = 0;
+ u16 pair;
+ size_t offset, length;
+
+ /* Do decompression until pointers are inside range */
+ while (up < unc_end && cmpr < cmpr_end) {
+ /* Correct index */
+ while (unc + s_max_off[index] < up)
+ index += 1;
+
+ /* Check the current flag for zero */
+ if (!(ch & (1 << bit))) {
+ /* Just copy byte */
+ *up++ = *cmpr++;
+ goto next;
+ }
+
+ /* Check for boundary */
+ if (cmpr + 1 >= cmpr_end)
+ return -EINVAL;
+
+ /* Read a short from little endian stream */
+ pair = cmpr[1];
+ pair <<= 8;
+ pair |= cmpr[0];
+
+ cmpr += 2;
+
+ /* Translate packed information into offset and length */
+ length = parse_pair(pair, &offset, index);
+
+ /* Check offset for boundary */
+ if (unc + offset > up)
+ return -EINVAL;
+
+ /* Truncate the length if necessary */
+ if (up + length >= unc_end)
+ length = unc_end - up;
+
+ /* Now we copy bytes. This is the heart of LZ algorithm. */
+ for (; length > 0; length--, up++)
+ *up = *(up - offset);
+
+next:
+ /* Advance flag bit value */
+ bit = (bit + 1) & 7;
+
+ if (!bit) {
+ if (cmpr >= cmpr_end)
+ break;
+
+ ch = *cmpr++;
+ }
+ }
+
+ /* return the size of uncompressed data */
+ return up - unc;
+}
+
+/*
+ * 0 - standard compression
+ * !0 - best compression, requires a lot of cpu
+ */
+struct lznt *get_lznt_ctx(int level)
+{
+ struct lznt *r = ntfs_zalloc(level ? offsetof(struct lznt, hash) :
+ sizeof(struct lznt));
+
+ if (r)
+ r->std = !level;
+ return r;
+}
+
+/*
+ * compress_lznt
+ *
+ * Compresses "unc" into "cmpr"
+ * +x - ok, 'cmpr' contains 'final_compressed_size' bytes of compressed data
+ * 0 - input buffer is full zero
+ */
+size_t compress_lznt(const void *unc, size_t unc_size, void *cmpr,
+ size_t cmpr_size, struct lznt *ctx)
+{
+ int err;
+ size_t (*match)(const u8 *src, struct lznt *ctx);
+ u8 *p = cmpr;
+ u8 *end = p + cmpr_size;
+ const u8 *unc_chunk = unc;
+ const u8 *unc_end = unc_chunk + unc_size;
+ bool is_zero = true;
+
+ if (ctx->std) {
+ match = &longest_match_std;
+ memset(ctx->hash, 0, sizeof(ctx->hash));
+ } else {
+ match = &longest_match_best;
+ }
+
+ /* compression cycle */
+ for (; unc_chunk < unc_end; unc_chunk += LZNT_CHUNK_SIZE) {
+ cmpr_size = 0;
+ err = compress_chunk(match, unc_chunk, unc_end, p, end,
+ &cmpr_size, ctx);
+ if (err < 0)
+ return unc_size;
+
+ if (is_zero && err != LZNT_ERROR_ALL_ZEROS)
+ is_zero = false;
+
+ p += cmpr_size;
+ }
+
+ if (p <= end - 2)
+ p[0] = p[1] = 0;
+
+ return is_zero ? 0 : PtrOffset(cmpr, p);
+}
+
+/*
+ * decompress_lznt
+ *
+ * decompresses "cmpr" into "unc"
+ */
+ssize_t decompress_lznt(const void *cmpr, size_t cmpr_size, void *unc,
+ size_t unc_size)
+{
+ const u8 *cmpr_chunk = cmpr;
+ const u8 *cmpr_end = cmpr_chunk + cmpr_size;
+ u8 *unc_chunk = unc;
+ u8 *unc_end = unc_chunk + unc_size;
+ u16 chunk_hdr;
+
+ if (cmpr_size < sizeof(short))
+ return -EINVAL;
+
+ /* read chunk header */
+ chunk_hdr = cmpr_chunk[1];
+ chunk_hdr <<= 8;
+ chunk_hdr |= cmpr_chunk[0];
+
+ /* loop through decompressing chunks */
+ for (;;) {
+ size_t chunk_size_saved;
+ size_t unc_use;
+ size_t cmpr_use = 3 + (chunk_hdr & (LZNT_CHUNK_SIZE - 1));
+
+ /* Check that the chunk actually fits the supplied buffer */
+ if (cmpr_chunk + cmpr_use > cmpr_end)
+ return -EINVAL;
+
+ /* First make sure the chunk contains compressed data */
+ if (chunk_hdr & 0x8000) {
+ /* Decompress a chunk and return if we get an error */
+ ssize_t err =
+ decompress_chunk(unc_chunk, unc_end,
+ cmpr_chunk + sizeof(chunk_hdr),
+ cmpr_chunk + cmpr_use);
+ if (err < 0)
+ return err;
+ unc_use = err;
+ } else {
+ /* This chunk does not contain compressed data */
+ unc_use = unc_chunk + LZNT_CHUNK_SIZE > unc_end ?
+ unc_end - unc_chunk :
+ LZNT_CHUNK_SIZE;
+
+ if (cmpr_chunk + sizeof(chunk_hdr) + unc_use >
+ cmpr_end) {
+ return -EINVAL;
+ }
+
+ memcpy(unc_chunk, cmpr_chunk + sizeof(chunk_hdr),
+ unc_use);
+ }
+
+ /* Advance pointers */
+ cmpr_chunk += cmpr_use;
+ unc_chunk += unc_use;
+
+ /* Check for the end of unc buffer */
+ if (unc_chunk >= unc_end)
+ break;
+
+ /* Proceed the next chunk */
+ if (cmpr_chunk > cmpr_end - 2)
+ break;
+
+ chunk_size_saved = LZNT_CHUNK_SIZE;
+
+ /* read chunk header */
+ chunk_hdr = cmpr_chunk[1];
+ chunk_hdr <<= 8;
+ chunk_hdr |= cmpr_chunk[0];
+
+ if (!chunk_hdr)
+ break;
+
+ /* Check the size of unc buffer */
+ if (unc_use < chunk_size_saved) {
+ size_t t1 = chunk_size_saved - unc_use;
+ u8 *t2 = unc_chunk + t1;
+
+ /* 'Zero' memory */
+ if (t2 >= unc_end)
+ break;
+
+ memset(unc_chunk, 0, t1);
+ unc_chunk = t2;
+ }
+ }
+
+ /* Check compression boundary */
+ if (cmpr_chunk > cmpr_end)
+ return -EINVAL;
+
+ /*
+ * The unc size is just a difference between current
+ * pointer and original one
+ */
+ return PtrOffset(unc, unc_chunk);
+}
--
2.25.4
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