// SPDX-License-Identifier: GPL-2.0
/*
*
* Copyright (C) 2019-2021 Paragon Software GmbH, All rights reserved.
*
*/
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/stddef.h>
#include <linux/string.h>
#include <linux/types.h>
#include "debug.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
*
* Return:
* * 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;
}
/*
* get_lznt_ctx
* @level: 0 - Standard compression.
* !0 - Best compression, requires a lot of cpu.
*/
struct lznt *get_lznt_ctx(int level)
{
struct lznt *r = kzalloc(level ? offsetof(struct lznt, hash) :
sizeof(struct lznt),
GFP_NOFS);
if (r)
r->std = !level;
return r;
}
/*
* compress_lznt - Compresses @unc into @cmpr
*
* Return:
* * +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 - Decompress @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);
}
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