#include <string.h>
-#ifdef __SSE2__
-# include <emmintrin.h>
-#endif
-
/* Huffman decoding tables and maps from symbols to code lengths. */
struct lzx_tables {
return match_len;
}
-static void
-undo_call_insn_translation(u32 *call_insn_target, s32 input_pos)
-{
- s32 abs_offset;
- s32 rel_offset;
-
- abs_offset = le32_to_cpu(*call_insn_target);
- if (abs_offset >= 0) {
- if (abs_offset < LZX_WIM_MAGIC_FILESIZE) {
- /* "good translation" */
- rel_offset = abs_offset - input_pos;
-
- *call_insn_target = cpu_to_le32(rel_offset);
- }
- } else {
- if (abs_offset >= -input_pos) {
- /* "compensating translation" */
- rel_offset = abs_offset + LZX_WIM_MAGIC_FILESIZE;
-
- *call_insn_target = cpu_to_le32(rel_offset);
- }
- }
-}
-
-/* Undo the 'E8' preprocessing, where the targets of x86 CALL instructions were
- * changed from relative offsets to absolute offsets.
- *
- * Note that this call instruction preprocessing can and will be used on any
- * data even if it is not actually x86 machine code. In fact, this type of
- * preprocessing appears to always be used in LZX-compressed resources in WIM
- * files; there is no bit to indicate whether it is used or not, unlike in the
- * LZX compressed format as used in cabinet files, where a bit is reserved for
- * that purpose.
- *
- * Call instruction preprocessing is disabled in the last 6 bytes of the
- * uncompressed data, which really means the 5-byte call instruction cannot
- * start in the last 10 bytes of the uncompressed data. This is one of the
- * errors in the LZX documentation.
- *
- * Call instruction preprocessing does not appear to be disabled after the
- * 32768th chunk of a WIM stream, which is apparently is yet another difference
- * from the LZX compression used in cabinet files.
- *
- * Call instruction processing is supposed to take the file size as a parameter,
- * as it is used in calculating the translated jump targets. But in WIM files,
- * this file size is always the same (LZX_WIM_MAGIC_FILESIZE == 12000000).*/
-static void
-undo_call_insn_preprocessing(u8 *uncompressed_data, size_t uncompressed_size)
-{
-#ifdef __SSE2__
-
- /* SSE2 vectorized implementation for x86_64. This speeds up LZX
- * decompression by about 5-8% overall. (Usually --- the performance
- * actually regresses slightly in the degenerate case that the data
- * consists entirely of 0xe8 bytes.) */
- __m128i *p128 = (__m128i *)uncompressed_data;
- u32 valid_mask = 0xFFFFFFFF;
-
- if (uncompressed_size >= 32 &&
- ((uintptr_t)uncompressed_data % 16 == 0))
- {
- __m128i * const end128 = p128 + uncompressed_size / 16 - 1;
-
- /* Create a vector of all 0xe8 bytes */
- const __m128i e8_bytes = _mm_set1_epi8(0xe8);
-
- /* Iterate through the 16-byte vectors in the input. */
- do {
- /* Compare the current 16-byte vector with the vector of
- * all 0xe8 bytes. This produces 0xff where the byte is
- * 0xe8 and 0x00 where it is not. */
- __m128i cmpresult = _mm_cmpeq_epi8(*p128, e8_bytes);
-
- /* Map the comparison results into a single 16-bit
- * number. It will contain a 1 bit when the
- * corresponding byte in the current 16-byte vector is
- * an e8 byte. Note: the low-order bit corresponds to
- * the first (lowest address) byte. */
- u32 e8_mask = _mm_movemask_epi8(cmpresult);
-
- if (!e8_mask) {
- /* If e8_mask is 0, then none of these 16 bytes
- * have value 0xe8. No e8 translation is
- * needed, and there is no restriction that
- * carries over to the next 16 bytes. */
- valid_mask = 0xFFFFFFFF;
- } else {
- /* At least one byte has value 0xe8.
- *
- * The AND with valid_mask accounts for the fact
- * that we can't start an e8 translation that
- * overlaps the previous one. */
- while ((e8_mask &= valid_mask)) {
-
- /* Count the number of trailing zeroes
- * in e8_mask. This will produce the
- * index of the byte, within the 16, at
- * which the next e8 translation should
- * be done. */
- u32 bit = __builtin_ctz(e8_mask);
-
- /* Do the e8 translation. */
- u8 *p8 = (u8 *)p128 + bit;
- undo_call_insn_translation((s32 *)(p8 + 1),
- p8 - uncompressed_data);
-
- /* Don't start an e8 translation in the
- * next 4 bytes. */
- valid_mask &= ~((u32)0x1F << bit);
- }
- /* Moving on to the next vector. Shift and set
- * valid_mask accordingly. */
- valid_mask >>= 16;
- valid_mask |= 0xFFFF0000;
- }
- } while (++p128 < end128);
- }
-
- u8 *p8 = (u8 *)p128;
- while (!(valid_mask & 1)) {
- p8++;
- valid_mask >>= 1;
- }
-#else /* __SSE2__ */
- u8 *p8 = uncompressed_data;
-#endif /* !__SSE2__ */
-
- if (uncompressed_size > 10) {
- /* Finish any bytes that weren't processed by the vectorized
- * implementation. */
- u8 *p8_end = uncompressed_data + uncompressed_size - 10;
- do {
- if (*p8 == 0xe8) {
- undo_call_insn_translation((s32 *)(p8 + 1),
- p8 - uncompressed_data);
- p8 += 5;
- } else {
- p8++;
- }
- } while (p8 < p8_end);
- }
-}
-
/*
* Decompresses an LZX-compressed block of data from which the header has already
* been read.
}
}
if (e8_preprocessing_done)
- undo_call_insn_preprocessing(uncompressed_data, uncompressed_size);
+ lzx_undo_e8_preprocessing(uncompressed_data, uncompressed_size);
return 0;
}
git://wimlib.net / wimlib / blobdiff