454 lines
9.4 KiB
C
454 lines
9.4 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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*
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* Copyright (C) 2019-2021 Paragon Software GmbH, All rights reserved.
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*
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*/
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#include <linux/kernel.h>
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#include <linux/slab.h>
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#include <linux/stddef.h>
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#include <linux/string.h>
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#include <linux/types.h>
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#include "debug.h"
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#include "ntfs_fs.h"
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// clang-format off
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/* Src buffer is zero. */
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#define LZNT_ERROR_ALL_ZEROS 1
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#define LZNT_CHUNK_SIZE 0x1000
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// clang-format on
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struct lznt_hash {
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const u8 *p1;
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const u8 *p2;
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};
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struct lznt {
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const u8 *unc;
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const u8 *unc_end;
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const u8 *best_match;
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size_t max_len;
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bool std;
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struct lznt_hash hash[LZNT_CHUNK_SIZE];
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};
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static inline size_t get_match_len(const u8 *ptr, const u8 *end, const u8 *prev,
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size_t max_len)
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{
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size_t len = 0;
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while (ptr + len < end && ptr[len] == prev[len] && ++len < max_len)
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;
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return len;
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}
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static size_t longest_match_std(const u8 *src, struct lznt *ctx)
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{
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size_t hash_index;
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size_t len1 = 0, len2 = 0;
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const u8 **hash;
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hash_index =
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((40543U * ((((src[0] << 4) ^ src[1]) << 4) ^ src[2])) >> 4) &
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(LZNT_CHUNK_SIZE - 1);
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hash = &(ctx->hash[hash_index].p1);
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if (hash[0] >= ctx->unc && hash[0] < src && hash[0][0] == src[0] &&
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hash[0][1] == src[1] && hash[0][2] == src[2]) {
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len1 = 3;
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if (ctx->max_len > 3)
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len1 += get_match_len(src + 3, ctx->unc_end,
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hash[0] + 3, ctx->max_len - 3);
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}
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if (hash[1] >= ctx->unc && hash[1] < src && hash[1][0] == src[0] &&
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hash[1][1] == src[1] && hash[1][2] == src[2]) {
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len2 = 3;
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if (ctx->max_len > 3)
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len2 += get_match_len(src + 3, ctx->unc_end,
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hash[1] + 3, ctx->max_len - 3);
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}
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/* Compare two matches and select the best one. */
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if (len1 < len2) {
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ctx->best_match = hash[1];
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len1 = len2;
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} else {
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ctx->best_match = hash[0];
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}
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hash[1] = hash[0];
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hash[0] = src;
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return len1;
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}
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static size_t longest_match_best(const u8 *src, struct lznt *ctx)
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{
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size_t max_len;
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const u8 *ptr;
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if (ctx->unc >= src || !ctx->max_len)
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return 0;
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max_len = 0;
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for (ptr = ctx->unc; ptr < src; ++ptr) {
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size_t len =
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get_match_len(src, ctx->unc_end, ptr, ctx->max_len);
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if (len >= max_len) {
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max_len = len;
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ctx->best_match = ptr;
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}
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}
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return max_len >= 3 ? max_len : 0;
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}
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static const size_t s_max_len[] = {
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0x1002, 0x802, 0x402, 0x202, 0x102, 0x82, 0x42, 0x22, 0x12,
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};
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static const size_t s_max_off[] = {
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0x10, 0x20, 0x40, 0x80, 0x100, 0x200, 0x400, 0x800, 0x1000,
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};
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static inline u16 make_pair(size_t offset, size_t len, size_t index)
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{
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return ((offset - 1) << (12 - index)) |
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((len - 3) & (((1 << (12 - index)) - 1)));
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}
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static inline size_t parse_pair(u16 pair, size_t *offset, size_t index)
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{
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*offset = 1 + (pair >> (12 - index));
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return 3 + (pair & ((1 << (12 - index)) - 1));
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}
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/*
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* compress_chunk
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*
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* Return:
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* * 0 - Ok, @cmpr contains @cmpr_chunk_size bytes of compressed data.
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* * 1 - Input buffer is full zero.
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* * -2 - The compressed buffer is too small to hold the compressed data.
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*/
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static inline int compress_chunk(size_t (*match)(const u8 *, struct lznt *),
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const u8 *unc, const u8 *unc_end, u8 *cmpr,
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u8 *cmpr_end, size_t *cmpr_chunk_size,
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struct lznt *ctx)
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{
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size_t cnt = 0;
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size_t idx = 0;
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const u8 *up = unc;
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u8 *cp = cmpr + 3;
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u8 *cp2 = cmpr + 2;
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u8 not_zero = 0;
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/* Control byte of 8-bit values: ( 0 - means byte as is, 1 - short pair ). */
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u8 ohdr = 0;
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u8 *last;
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u16 t16;
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if (unc + LZNT_CHUNK_SIZE < unc_end)
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unc_end = unc + LZNT_CHUNK_SIZE;
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last = min(cmpr + LZNT_CHUNK_SIZE + sizeof(short), cmpr_end);
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ctx->unc = unc;
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ctx->unc_end = unc_end;
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ctx->max_len = s_max_len[0];
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while (up < unc_end) {
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size_t max_len;
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while (unc + s_max_off[idx] < up)
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ctx->max_len = s_max_len[++idx];
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/* Find match. */
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max_len = up + 3 <= unc_end ? (*match)(up, ctx) : 0;
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if (!max_len) {
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if (cp >= last)
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goto NotCompressed;
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not_zero |= *cp++ = *up++;
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} else if (cp + 1 >= last) {
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goto NotCompressed;
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} else {
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t16 = make_pair(up - ctx->best_match, max_len, idx);
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*cp++ = t16;
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*cp++ = t16 >> 8;
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ohdr |= 1 << cnt;
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up += max_len;
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}
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cnt = (cnt + 1) & 7;
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if (!cnt) {
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*cp2 = ohdr;
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ohdr = 0;
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cp2 = cp;
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cp += 1;
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}
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}
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if (cp2 < last)
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*cp2 = ohdr;
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else
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cp -= 1;
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*cmpr_chunk_size = cp - cmpr;
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t16 = (*cmpr_chunk_size - 3) | 0xB000;
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cmpr[0] = t16;
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cmpr[1] = t16 >> 8;
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return not_zero ? 0 : LZNT_ERROR_ALL_ZEROS;
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NotCompressed:
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if ((cmpr + LZNT_CHUNK_SIZE + sizeof(short)) > last)
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return -2;
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/*
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* Copy non cmpr data.
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* 0x3FFF == ((LZNT_CHUNK_SIZE + 2 - 3) | 0x3000)
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*/
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cmpr[0] = 0xff;
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cmpr[1] = 0x3f;
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memcpy(cmpr + sizeof(short), unc, LZNT_CHUNK_SIZE);
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*cmpr_chunk_size = LZNT_CHUNK_SIZE + sizeof(short);
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return 0;
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}
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static inline ssize_t decompress_chunk(u8 *unc, u8 *unc_end, const u8 *cmpr,
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const u8 *cmpr_end)
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{
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u8 *up = unc;
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u8 ch = *cmpr++;
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size_t bit = 0;
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size_t index = 0;
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u16 pair;
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size_t offset, length;
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/* Do decompression until pointers are inside range. */
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while (up < unc_end && cmpr < cmpr_end) {
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/* Correct index */
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while (unc + s_max_off[index] < up)
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index += 1;
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/* Check the current flag for zero. */
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if (!(ch & (1 << bit))) {
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/* Just copy byte. */
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*up++ = *cmpr++;
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goto next;
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}
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/* Check for boundary. */
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if (cmpr + 1 >= cmpr_end)
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return -EINVAL;
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/* Read a short from little endian stream. */
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pair = cmpr[1];
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pair <<= 8;
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pair |= cmpr[0];
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cmpr += 2;
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/* Translate packed information into offset and length. */
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length = parse_pair(pair, &offset, index);
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/* Check offset for boundary. */
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if (unc + offset > up)
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return -EINVAL;
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/* Truncate the length if necessary. */
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if (up + length >= unc_end)
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length = unc_end - up;
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/* Now we copy bytes. This is the heart of LZ algorithm. */
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for (; length > 0; length--, up++)
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*up = *(up - offset);
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next:
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/* Advance flag bit value. */
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bit = (bit + 1) & 7;
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if (!bit) {
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if (cmpr >= cmpr_end)
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break;
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ch = *cmpr++;
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}
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}
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/* Return the size of uncompressed data. */
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return up - unc;
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}
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/*
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* get_lznt_ctx
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* @level: 0 - Standard compression.
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* !0 - Best compression, requires a lot of cpu.
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*/
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struct lznt *get_lznt_ctx(int level)
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{
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struct lznt *r = kzalloc(level ? offsetof(struct lznt, hash) :
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sizeof(struct lznt),
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GFP_NOFS);
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if (r)
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r->std = !level;
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return r;
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}
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/*
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* compress_lznt - Compresses @unc into @cmpr
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*
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* Return:
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* * +x - Ok, @cmpr contains 'final_compressed_size' bytes of compressed data.
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* * 0 - Input buffer is full zero.
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*/
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size_t compress_lznt(const void *unc, size_t unc_size, void *cmpr,
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size_t cmpr_size, struct lznt *ctx)
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{
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int err;
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size_t (*match)(const u8 *src, struct lznt *ctx);
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u8 *p = cmpr;
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u8 *end = p + cmpr_size;
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const u8 *unc_chunk = unc;
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const u8 *unc_end = unc_chunk + unc_size;
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bool is_zero = true;
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if (ctx->std) {
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match = &longest_match_std;
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memset(ctx->hash, 0, sizeof(ctx->hash));
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} else {
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match = &longest_match_best;
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}
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/* Compression cycle. */
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for (; unc_chunk < unc_end; unc_chunk += LZNT_CHUNK_SIZE) {
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cmpr_size = 0;
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err = compress_chunk(match, unc_chunk, unc_end, p, end,
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&cmpr_size, ctx);
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if (err < 0)
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return unc_size;
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if (is_zero && err != LZNT_ERROR_ALL_ZEROS)
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is_zero = false;
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p += cmpr_size;
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}
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if (p <= end - 2)
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p[0] = p[1] = 0;
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return is_zero ? 0 : PtrOffset(cmpr, p);
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}
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/*
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* decompress_lznt - Decompress @cmpr into @unc.
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*/
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ssize_t decompress_lznt(const void *cmpr, size_t cmpr_size, void *unc,
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size_t unc_size)
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{
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const u8 *cmpr_chunk = cmpr;
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const u8 *cmpr_end = cmpr_chunk + cmpr_size;
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u8 *unc_chunk = unc;
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u8 *unc_end = unc_chunk + unc_size;
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u16 chunk_hdr;
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if (cmpr_size < sizeof(short))
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return -EINVAL;
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/* Read chunk header. */
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chunk_hdr = cmpr_chunk[1];
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chunk_hdr <<= 8;
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chunk_hdr |= cmpr_chunk[0];
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/* Loop through decompressing chunks. */
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for (;;) {
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size_t chunk_size_saved;
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size_t unc_use;
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size_t cmpr_use = 3 + (chunk_hdr & (LZNT_CHUNK_SIZE - 1));
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/* Check that the chunk actually fits the supplied buffer. */
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if (cmpr_chunk + cmpr_use > cmpr_end)
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return -EINVAL;
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/* First make sure the chunk contains compressed data. */
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if (chunk_hdr & 0x8000) {
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/* Decompress a chunk and return if we get an error. */
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ssize_t err =
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decompress_chunk(unc_chunk, unc_end,
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cmpr_chunk + sizeof(chunk_hdr),
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cmpr_chunk + cmpr_use);
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if (err < 0)
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return err;
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unc_use = err;
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} else {
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/* This chunk does not contain compressed data. */
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unc_use = unc_chunk + LZNT_CHUNK_SIZE > unc_end ?
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unc_end - unc_chunk :
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LZNT_CHUNK_SIZE;
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if (cmpr_chunk + sizeof(chunk_hdr) + unc_use >
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cmpr_end) {
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return -EINVAL;
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}
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memcpy(unc_chunk, cmpr_chunk + sizeof(chunk_hdr),
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unc_use);
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}
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/* Advance pointers. */
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cmpr_chunk += cmpr_use;
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unc_chunk += unc_use;
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/* Check for the end of unc buffer. */
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if (unc_chunk >= unc_end)
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break;
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/* Proceed the next chunk. */
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if (cmpr_chunk > cmpr_end - 2)
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break;
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chunk_size_saved = LZNT_CHUNK_SIZE;
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/* Read chunk header. */
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chunk_hdr = cmpr_chunk[1];
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chunk_hdr <<= 8;
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chunk_hdr |= cmpr_chunk[0];
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if (!chunk_hdr)
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break;
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/* Check the size of unc buffer. */
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if (unc_use < chunk_size_saved) {
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size_t t1 = chunk_size_saved - unc_use;
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u8 *t2 = unc_chunk + t1;
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/* 'Zero' memory. */
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if (t2 >= unc_end)
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break;
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memset(unc_chunk, 0, t1);
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unc_chunk = t2;
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}
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}
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/* Check compression boundary. */
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if (cmpr_chunk > cmpr_end)
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return -EINVAL;
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/*
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* The unc size is just a difference between current
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* pointer and original one.
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*/
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return PtrOffset(unc, unc_chunk);
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}
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