1 files changed, 574 insertions, 0 deletions

diff --git a/lib/xz/xz_dec_bcj.c b/lib/xz/xz_dec_bcj.c
new file mode 100644
index 0000000000..ef449e97d1
--- /dev/null
+++ b/lib/xz/xz_dec_bcj.c
@@ -0,0 +1,574 @@
+/*
+ * Branch/Call/Jump (BCJ) filter decoders
+ *
+ * Authors: Lasse Collin <lasse.collin@tukaani.org>
+ *          Igor Pavlov <https://7-zip.org/>
+ *
+ * This file has been put into the public domain.
+ * You can do whatever you want with this file.
+ */
+
+#include "xz_private.h"
+
+/*
+ * The rest of the file is inside this ifdef. It makes things a little more
+ * convenient when building without support for any BCJ filters.
+ */
+#ifdef XZ_DEC_BCJ
+
+struct xz_dec_bcj {
+	/* Type of the BCJ filter being used */
+	enum {
+		BCJ_X86 = 4,        /* x86 or x86-64 */
+		BCJ_POWERPC = 5,    /* Big endian only */
+		BCJ_IA64 = 6,       /* Big or little endian */
+		BCJ_ARM = 7,        /* Little endian only */
+		BCJ_ARMTHUMB = 8,   /* Little endian only */
+		BCJ_SPARC = 9       /* Big or little endian */
+	} type;
+
+	/*
+	 * Return value of the next filter in the chain. We need to preserve
+	 * this information across calls, because we must not call the next
+	 * filter anymore once it has returned XZ_STREAM_END.
+	 */
+	enum xz_ret ret;
+
+	/* True if we are operating in single-call mode. */
+	bool single_call;
+
+	/*
+	 * Absolute position relative to the beginning of the uncompressed
+	 * data (in a single .xz Block). We care only about the lowest 32
+	 * bits so this doesn't need to be uint64_t even with big files.
+	 */
+	uint32_t pos;
+
+	/* x86 filter state */
+	uint32_t x86_prev_mask;
+
+	/* Temporary space to hold the variables from struct xz_buf */
+	uint8_t *out;
+	size_t out_pos;
+	size_t out_size;
+
+	struct {
+		/* Amount of already filtered data in the beginning of buf */
+		size_t filtered;
+
+		/* Total amount of data currently stored in buf  */
+		size_t size;
+
+		/*
+		 * Buffer to hold a mix of filtered and unfiltered data. This
+		 * needs to be big enough to hold Alignment + 2 * Look-ahead:
+		 *
+		 * Type         Alignment   Look-ahead
+		 * x86              1           4
+		 * PowerPC          4           0
+		 * IA-64           16           0
+		 * ARM              4           0
+		 * ARM-Thumb        2           2
+		 * SPARC            4           0
+		 */
+		uint8_t buf[16];
+	} temp;
+};
+
+#ifdef XZ_DEC_X86
+/*
+ * This is used to test the most significant byte of a memory address
+ * in an x86 instruction.
+ */
+static inline int bcj_x86_test_msbyte(uint8_t b)
+{
+	return b == 0x00 || b == 0xFF;
+}
+
+static size_t bcj_x86(struct xz_dec_bcj *s, uint8_t *buf, size_t size)
+{
+	static const bool mask_to_allowed_status[8]
+		= { true, true, true, false, true, false, false, false };
+
+	static const uint8_t mask_to_bit_num[8] = { 0, 1, 2, 2, 3, 3, 3, 3 };
+
+	size_t i;
+	size_t prev_pos = (size_t)-1;
+	uint32_t prev_mask = s->x86_prev_mask;
+	uint32_t src;
+	uint32_t dest;
+	uint32_t j;
+	uint8_t b;
+
+	if (size <= 4)
+		return 0;
+
+	size -= 4;
+	for (i = 0; i < size; ++i) {
+		if ((buf[i] & 0xFE) != 0xE8)
+			continue;
+
+		prev_pos = i - prev_pos;
+		if (prev_pos > 3) {
+			prev_mask = 0;
+		} else {
+			prev_mask = (prev_mask << (prev_pos - 1)) & 7;
+			if (prev_mask != 0) {
+				b = buf[i + 4 - mask_to_bit_num[prev_mask]];
+				if (!mask_to_allowed_status[prev_mask]
+						|| bcj_x86_test_msbyte(b)) {
+					prev_pos = i;
+					prev_mask = (prev_mask << 1) | 1;
+					continue;
+				}
+			}
+		}
+
+		prev_pos = i;
+
+		if (bcj_x86_test_msbyte(buf[i + 4])) {
+			src = get_unaligned_le32(buf + i + 1);
+			while (true) {
+				dest = src - (s->pos + (uint32_t)i + 5);
+				if (prev_mask == 0)
+					break;
+
+				j = mask_to_bit_num[prev_mask] * 8;
+				b = (uint8_t)(dest >> (24 - j));
+				if (!bcj_x86_test_msbyte(b))
+					break;
+
+				src = dest ^ (((uint32_t)1 << (32 - j)) - 1);
+			}
+
+			dest &= 0x01FFFFFF;
+			dest |= (uint32_t)0 - (dest & 0x01000000);
+			put_unaligned_le32(dest, buf + i + 1);
+			i += 4;
+		} else {
+			prev_mask = (prev_mask << 1) | 1;
+		}
+	}
+
+	prev_pos = i - prev_pos;
+	s->x86_prev_mask = prev_pos > 3 ? 0 : prev_mask << (prev_pos - 1);
+	return i;
+}
+#endif
+
+#ifdef XZ_DEC_POWERPC
+static size_t bcj_powerpc(struct xz_dec_bcj *s, uint8_t *buf, size_t size)
+{
+	size_t i;
+	uint32_t instr;
+
+	for (i = 0; i + 4 <= size; i += 4) {
+		instr = get_unaligned_be32(buf + i);
+		if ((instr & 0xFC000003) == 0x48000001) {
+			instr &= 0x03FFFFFC;
+			instr -= s->pos + (uint32_t)i;
+			instr &= 0x03FFFFFC;
+			instr |= 0x48000001;
+			put_unaligned_be32(instr, buf + i);
+		}
+	}
+
+	return i;
+}
+#endif
+
+#ifdef XZ_DEC_IA64
+static size_t bcj_ia64(struct xz_dec_bcj *s, uint8_t *buf, size_t size)
+{
+	static const uint8_t branch_table[32] = {
+		0, 0, 0, 0, 0, 0, 0, 0,
+		0, 0, 0, 0, 0, 0, 0, 0,
+		4, 4, 6, 6, 0, 0, 7, 7,
+		4, 4, 0, 0, 4, 4, 0, 0
+	};
+
+	/*
+	 * The local variables take a little bit stack space, but it's less
+	 * than what LZMA2 decoder takes, so it doesn't make sense to reduce
+	 * stack usage here without doing that for the LZMA2 decoder too.
+	 */
+
+	/* Loop counters */
+	size_t i;
+	size_t j;
+
+	/* Instruction slot (0, 1, or 2) in the 128-bit instruction word */
+	uint32_t slot;
+
+	/* Bitwise offset of the instruction indicated by slot */
+	uint32_t bit_pos;
+
+	/* bit_pos split into byte and bit parts */
+	uint32_t byte_pos;
+	uint32_t bit_res;
+
+	/* Address part of an instruction */
+	uint32_t addr;
+
+	/* Mask used to detect which instructions to convert */
+	uint32_t mask;
+
+	/* 41-bit instruction stored somewhere in the lowest 48 bits */
+	uint64_t instr;
+
+	/* Instruction normalized with bit_res for easier manipulation */
+	uint64_t norm;
+
+	for (i = 0; i + 16 <= size; i += 16) {
+		mask = branch_table[buf[i] & 0x1F];
+		for (slot = 0, bit_pos = 5; slot < 3; ++slot, bit_pos += 41) {
+			if (((mask >> slot) & 1) == 0)
+				continue;
+
+			byte_pos = bit_pos >> 3;
+			bit_res = bit_pos & 7;
+			instr = 0;
+			for (j = 0; j < 6; ++j)
+				instr |= (uint64_t)(buf[i + j + byte_pos])
+						<< (8 * j);
+
+			norm = instr >> bit_res;
+
+			if (((norm >> 37) & 0x0F) == 0x05
+					&& ((norm >> 9) & 0x07) == 0) {
+				addr = (norm >> 13) & 0x0FFFFF;
+				addr |= ((uint32_t)(norm >> 36) & 1) << 20;
+				addr <<= 4;
+				addr -= s->pos + (uint32_t)i;
+				addr >>= 4;
+
+				norm &= ~((uint64_t)0x8FFFFF << 13);
+				norm |= (uint64_t)(addr & 0x0FFFFF) << 13;
+				norm |= (uint64_t)(addr & 0x100000)
+						<< (36 - 20);
+
+				instr &= (1 << bit_res) - 1;
+				instr |= norm << bit_res;
+
+				for (j = 0; j < 6; j++)
+					buf[i + j + byte_pos]
+						= (uint8_t)(instr >> (8 * j));
+			}
+		}
+	}
+
+	return i;
+}
+#endif
+
+#ifdef XZ_DEC_ARM
+static size_t bcj_arm(struct xz_dec_bcj *s, uint8_t *buf, size_t size)
+{
+	size_t i;
+	uint32_t addr;
+
+	for (i = 0; i + 4 <= size; i += 4) {
+		if (buf[i + 3] == 0xEB) {
+			addr = (uint32_t)buf[i] | ((uint32_t)buf[i + 1] << 8)
+					| ((uint32_t)buf[i + 2] << 16);
+			addr <<= 2;
+			addr -= s->pos + (uint32_t)i + 8;
+			addr >>= 2;
+			buf[i] = (uint8_t)addr;
+			buf[i + 1] = (uint8_t)(addr >> 8);
+			buf[i + 2] = (uint8_t)(addr >> 16);
+		}
+	}
+
+	return i;
+}
+#endif
+
+#ifdef XZ_DEC_ARMTHUMB
+static size_t bcj_armthumb(struct xz_dec_bcj *s, uint8_t *buf, size_t size)
+{
+	size_t i;
+	uint32_t addr;
+
+	for (i = 0; i + 4 <= size; i += 2) {
+		if ((buf[i + 1] & 0xF8) == 0xF0
+				&& (buf[i + 3] & 0xF8) == 0xF8) {
+			addr = (((uint32_t)buf[i + 1] & 0x07) << 19)
+					| ((uint32_t)buf[i] << 11)
+					| (((uint32_t)buf[i + 3] & 0x07) << 8)
+					| (uint32_t)buf[i + 2];
+			addr <<= 1;
+			addr -= s->pos + (uint32_t)i + 4;
+			addr >>= 1;
+			buf[i + 1] = (uint8_t)(0xF0 | ((addr >> 19) & 0x07));
+			buf[i] = (uint8_t)(addr >> 11);
+			buf[i + 3] = (uint8_t)(0xF8 | ((addr >> 8) & 0x07));
+			buf[i + 2] = (uint8_t)addr;
+			i += 2;
+		}
+	}
+
+	return i;
+}
+#endif
+
+#ifdef XZ_DEC_SPARC
+static size_t bcj_sparc(struct xz_dec_bcj *s, uint8_t *buf, size_t size)
+{
+	size_t i;
+	uint32_t instr;
+
+	for (i = 0; i + 4 <= size; i += 4) {
+		instr = get_unaligned_be32(buf + i);
+		if ((instr >> 22) == 0x100 || (instr >> 22) == 0x1FF) {
+			instr <<= 2;
+			instr -= s->pos + (uint32_t)i;
+			instr >>= 2;
+			instr = ((uint32_t)0x40000000 - (instr & 0x400000))
+					| 0x40000000 | (instr & 0x3FFFFF);
+			put_unaligned_be32(instr, buf + i);
+		}
+	}
+
+	return i;
+}
+#endif
+
+/*
+ * Apply the selected BCJ filter. Update *pos and s->pos to match the amount
+ * of data that got filtered.
+ *
+ * NOTE: This is implemented as a switch statement to avoid using function
+ * pointers, which could be problematic in the kernel boot code, which must
+ * avoid pointers to static data (at least on x86).
+ */
+static void bcj_apply(struct xz_dec_bcj *s,
+		      uint8_t *buf, size_t *pos, size_t size)
+{
+	size_t filtered;
+
+	buf += *pos;
+	size -= *pos;
+
+	switch (s->type) {
+#ifdef XZ_DEC_X86
+	case BCJ_X86:
+		filtered = bcj_x86(s, buf, size);
+		break;
+#endif
+#ifdef XZ_DEC_POWERPC
+	case BCJ_POWERPC:
+		filtered = bcj_powerpc(s, buf, size);
+		break;
+#endif
+#ifdef XZ_DEC_IA64
+	case BCJ_IA64:
+		filtered = bcj_ia64(s, buf, size);
+		break;
+#endif
+#ifdef XZ_DEC_ARM
+	case BCJ_ARM:
+		filtered = bcj_arm(s, buf, size);
+		break;
+#endif
+#ifdef XZ_DEC_ARMTHUMB
+	case BCJ_ARMTHUMB:
+		filtered = bcj_armthumb(s, buf, size);
+		break;
+#endif
+#ifdef XZ_DEC_SPARC
+	case BCJ_SPARC:
+		filtered = bcj_sparc(s, buf, size);
+		break;
+#endif
+	default:
+		/* Never reached but silence compiler warnings. */
+		filtered = 0;
+		break;
+	}
+
+	*pos += filtered;
+	s->pos += filtered;
+}
+
+/*
+ * Flush pending filtered data from temp to the output buffer.
+ * Move the remaining mixture of possibly filtered and unfiltered
+ * data to the beginning of temp.
+ */
+static void bcj_flush(struct xz_dec_bcj *s, struct xz_buf *b)
+{
+	size_t copy_size;
+
+	copy_size = min_t(size_t, s->temp.filtered, b->out_size - b->out_pos);
+	memcpy(b->out + b->out_pos, s->temp.buf, copy_size);
+	b->out_pos += copy_size;
+
+	s->temp.filtered -= copy_size;
+	s->temp.size -= copy_size;
+	memmove(s->temp.buf, s->temp.buf + copy_size, s->temp.size);
+}
+
+/*
+ * The BCJ filter functions are primitive in sense that they process the
+ * data in chunks of 1-16 bytes. To hide this issue, this function does
+ * some buffering.
+ */
+XZ_EXTERN enum xz_ret xz_dec_bcj_run(struct xz_dec_bcj *s,
+				     struct xz_dec_lzma2 *lzma2,
+				     struct xz_buf *b)
+{
+	size_t out_start;
+
+	/*
+	 * Flush pending already filtered data to the output buffer. Return
+	 * immediately if we couldn't flush everything, or if the next
+	 * filter in the chain had already returned XZ_STREAM_END.
+	 */
+	if (s->temp.filtered > 0) {
+		bcj_flush(s, b);
+		if (s->temp.filtered > 0)
+			return XZ_OK;
+
+		if (s->ret == XZ_STREAM_END)
+			return XZ_STREAM_END;
+	}
+
+	/*
+	 * If we have more output space than what is currently pending in
+	 * temp, copy the unfiltered data from temp to the output buffer
+	 * and try to fill the output buffer by decoding more data from the
+	 * next filter in the chain. Apply the BCJ filter on the new data
+	 * in the output buffer. If everything cannot be filtered, copy it
+	 * to temp and rewind the output buffer position accordingly.
+	 *
+	 * This needs to be always run when temp.size == 0 to handle a special
+	 * case where the output buffer is full and the next filter has no
+	 * more output coming but hasn't returned XZ_STREAM_END yet.
+	 */
+	if (s->temp.size < b->out_size - b->out_pos || s->temp.size == 0) {
+		out_start = b->out_pos;
+		memcpy(b->out + b->out_pos, s->temp.buf, s->temp.size);
+		b->out_pos += s->temp.size;
+
+		s->ret = xz_dec_lzma2_run(lzma2, b);
+		if (s->ret != XZ_STREAM_END
+				&& (s->ret != XZ_OK || s->single_call))
+			return s->ret;
+
+		bcj_apply(s, b->out, &out_start, b->out_pos);
+
+		/*
+		 * As an exception, if the next filter returned XZ_STREAM_END,
+		 * we can do that too, since the last few bytes that remain
+		 * unfiltered are meant to remain unfiltered.
+		 */
+		if (s->ret == XZ_STREAM_END)
+			return XZ_STREAM_END;
+
+		s->temp.size = b->out_pos - out_start;
+		b->out_pos -= s->temp.size;
+		memcpy(s->temp.buf, b->out + b->out_pos, s->temp.size);
+
+		/*
+		 * If there wasn't enough input to the next filter to fill
+		 * the output buffer with unfiltered data, there's no point
+		 * to try decoding more data to temp.
+		 */
+		if (b->out_pos + s->temp.size < b->out_size)
+			return XZ_OK;
+	}
+
+	/*
+	 * We have unfiltered data in temp. If the output buffer isn't full
+	 * yet, try to fill the temp buffer by decoding more data from the
+	 * next filter. Apply the BCJ filter on temp. Then we hopefully can
+	 * fill the actual output buffer by copying filtered data from temp.
+	 * A mix of filtered and unfiltered data may be left in temp; it will
+	 * be taken care on the next call to this function.
+	 */
+	if (b->out_pos < b->out_size) {
+		/* Make b->out{,_pos,_size} temporarily point to s->temp. */
+		s->out = b->out;
+		s->out_pos = b->out_pos;
+		s->out_size = b->out_size;
+		b->out = s->temp.buf;
+		b->out_pos = s->temp.size;
+		b->out_size = sizeof(s->temp.buf);
+
+		s->ret = xz_dec_lzma2_run(lzma2, b);
+
+		s->temp.size = b->out_pos;
+		b->out = s->out;
+		b->out_pos = s->out_pos;
+		b->out_size = s->out_size;
+
+		if (s->ret != XZ_OK && s->ret != XZ_STREAM_END)
+			return s->ret;
+
+		bcj_apply(s, s->temp.buf, &s->temp.filtered, s->temp.size);
+
+		/*
+		 * If the next filter returned XZ_STREAM_END, we mark that
+		 * everything is filtered, since the last unfiltered bytes
+		 * of the stream are meant to be left as is.
+		 */
+		if (s->ret == XZ_STREAM_END)
+			s->temp.filtered = s->temp.size;
+
+		bcj_flush(s, b);
+		if (s->temp.filtered > 0)
+			return XZ_OK;
+	}
+
+	return s->ret;
+}
+
+XZ_EXTERN struct xz_dec_bcj *xz_dec_bcj_create(bool single_call)
+{
+	struct xz_dec_bcj *s = kmalloc(sizeof(*s), GFP_KERNEL);
+	if (s != NULL)
+		s->single_call = single_call;
+
+	return s;
+}
+
+XZ_EXTERN enum xz_ret xz_dec_bcj_reset(struct xz_dec_bcj *s, uint8_t id)
+{
+	switch (id) {
+#ifdef XZ_DEC_X86
+	case BCJ_X86:
+#endif
+#ifdef XZ_DEC_POWERPC
+	case BCJ_POWERPC:
+#endif
+#ifdef XZ_DEC_IA64
+	case BCJ_IA64:
+#endif
+#ifdef XZ_DEC_ARM
+	case BCJ_ARM:
+#endif
+#ifdef XZ_DEC_ARMTHUMB
+	case BCJ_ARMTHUMB:
+#endif
+#ifdef XZ_DEC_SPARC
+	case BCJ_SPARC:
+#endif
+		break;
+
+	default:
+		/* Unsupported Filter ID */
+		return XZ_OPTIONS_ERROR;
+	}
+
+	s->type = id;
+	s->ret = XZ_OK;
+	s->pos = 0;
+	s->x86_prev_mask = 0;
+	s->temp.filtered = 0;
+	s->temp.size = 0;
+
+	return XZ_OK;
+}
+
+#endif