updated on Wed Jan 25 08:34:36 UTC 2012

[aur-mirror.git] / xen / dom0_xz_decompression.patch

diff --git a/xen/common/Makefile b/xen/common/Makefile
--- a/xen/common/Makefile
+++ b/xen/common/Makefile
@@ -43,7 +43,7 @@
 obj-y += rbtree.o
 obj-y += lzo.o
 
-obj-$(CONFIG_X86) += decompress.o bunzip2.o unlzma.o unlzo.o
+obj-$(CONFIG_X86) += decompress.o bunzip2.o unxz.o unlzma.o unlzo.o
 
 obj-$(perfc)       += perfc.o
 obj-$(crash_debug) += gdbstub.o
diff --git a/xen/common/decompress.c b/xen/common/decompress.c
--- a/xen/common/decompress.c
+++ b/xen/common/decompress.c
@@ -20,6 +20,9 @@
     if ( len >= 3 && !memcmp(inbuf, "\x42\x5a\x68", 3) )
         return bunzip2(inbuf, len, NULL, NULL, outbuf, NULL, error);
 
+    if ( len >= 6 && !memcmp(inbuf, "\3757zXZ", 6) )
+        return unxz(inbuf, len, NULL, NULL, outbuf, NULL, error);
+
     if ( len >= 2 && !memcmp(inbuf, "\135\000", 2) )
         return unlzma(inbuf, len, NULL, NULL, outbuf, NULL, error);
 
diff --git a/xen/common/decompress.h b/xen/common/decompress.h
--- a/xen/common/decompress.h
+++ b/xen/common/decompress.h
@@ -8,6 +8,7 @@
 
 #define STATIC
 #define INIT __init
+#define INITDATA __initdata
 
 static void(*__initdata error)(const char *);
 #define set_error_fn(x) error = x;
diff --git a/xen/common/unxz.c b/xen/common/unxz.c
new file mode 100644
--- /dev/null
+++ b/xen/common/unxz.c
@@ -0,0 +1,306 @@
+/*
+ * Wrapper for decompressing XZ-compressed kernel, initramfs, and initrd
+ *
+ * Author: Lasse Collin <lasse.collin@tukaani.org>
+ *
+ * This file has been put into the public domain.
+ * You can do whatever you want with this file.
+ */
+
+/*
+ * Important notes about in-place decompression
+ *
+ * At least on x86, the kernel is decompressed in place: the compressed data
+ * is placed to the end of the output buffer, and the decompressor overwrites
+ * most of the compressed data. There must be enough safety margin to
+ * guarantee that the write position is always behind the read position.
+ *
+ * The safety margin for XZ with LZMA2 or BCJ+LZMA2 is calculated below.
+ * Note that the margin with XZ is bigger than with Deflate (gzip)!
+ *
+ * The worst case for in-place decompression is that the beginning of
+ * the file is compressed extremely well, and the rest of the file is
+ * uncompressible. Thus, we must look for worst-case expansion when the
+ * compressor is encoding uncompressible data.
+ *
+ * The structure of the .xz file in case of a compresed kernel is as follows.
+ * Sizes (as bytes) of the fields are in parenthesis.
+ *
+ *    Stream Header (12)
+ *    Block Header:
+ *      Block Header (8-12)
+ *      Compressed Data (N)
+ *      Block Padding (0-3)
+ *      CRC32 (4)
+ *    Index (8-20)
+ *    Stream Footer (12)
+ *
+ * Normally there is exactly one Block, but let's assume that there are
+ * 2-4 Blocks just in case. Because Stream Header and also Block Header
+ * of the first Block don't make the decompressor produce any uncompressed
+ * data, we can ignore them from our calculations. Block Headers of possible
+ * additional Blocks have to be taken into account still. With these
+ * assumptions, it is safe to assume that the total header overhead is
+ * less than 128 bytes.
+ *
+ * Compressed Data contains LZMA2 or BCJ+LZMA2 encoded data. Since BCJ
+ * doesn't change the size of the data, it is enough to calculate the
+ * safety margin for LZMA2.
+ *
+ * LZMA2 stores the data in chunks. Each chunk has a header whose size is
+ * a maximum of 6 bytes, but to get round 2^n numbers, let's assume that
+ * the maximum chunk header size is 8 bytes. After the chunk header, there
+ * may be up to 64 KiB of actual payload in the chunk. Often the payload is
+ * quite a bit smaller though; to be safe, let's assume that an average
+ * chunk has only 32 KiB of payload.
+ *
+ * The maximum uncompressed size of the payload is 2 MiB. The minimum
+ * uncompressed size of the payload is in practice never less than the
+ * payload size itself. The LZMA2 format would allow uncompressed size
+ * to be less than the payload size, but no sane compressor creates such
+ * files. LZMA2 supports storing uncompressible data in uncompressed form,
+ * so there's never a need to create payloads whose uncompressed size is
+ * smaller than the compressed size.
+ *
+ * The assumption, that the uncompressed size of the payload is never
+ * smaller than the payload itself, is valid only when talking about
+ * the payload as a whole. It is possible that the payload has parts where
+ * the decompressor consumes more input than it produces output. Calculating
+ * the worst case for this would be tricky. Instead of trying to do that,
+ * let's simply make sure that the decompressor never overwrites any bytes
+ * of the payload which it is currently reading.
+ *
+ * Now we have enough information to calculate the safety margin. We need
+ *   - 128 bytes for the .xz file format headers;
+ *   - 8 bytes per every 32 KiB of uncompressed size (one LZMA2 chunk header
+ *     per chunk, each chunk having average payload size of 32 KiB); and
+ *   - 64 KiB (biggest possible LZMA2 chunk payload size) to make sure that
+ *     the decompressor never overwrites anything from the LZMA2 chunk
+ *     payload it is currently reading.
+ *
+ * We get the following formula:
+ *
+ *    safety_margin = 128 + uncompressed_size * 8 / 32768 + 65536
+ *                  = 128 + (uncompressed_size >> 12) + 65536
+ *
+ * For comparision, according to arch/x86/boot/compressed/misc.c, the
+ * equivalent formula for Deflate is this:
+ *
+ *    safety_margin = 18 + (uncompressed_size >> 12) + 32768
+ *
+ * Thus, when updating Deflate-only in-place kernel decompressor to
+ * support XZ, the fixed overhead has to be increased from 18+32768 bytes
+ * to 128+65536 bytes.
+ */
+
+#include "decompress.h"
+
+#define XZ_EXTERN STATIC
+
+/*
+ * For boot time use, we enable only the BCJ filter of the current
+ * architecture or none if no BCJ filter is available for the architecture.
+ */
+#ifdef CONFIG_X86
+#      define XZ_DEC_X86
+#endif
+#ifdef CONFIG_PPC
+#      define XZ_DEC_POWERPC
+#endif
+#ifdef CONFIG_ARM
+#      define XZ_DEC_ARM
+#endif
+#ifdef CONFIG_IA64
+#      define XZ_DEC_IA64
+#endif
+#ifdef CONFIG_SPARC
+#      define XZ_DEC_SPARC
+#endif
+
+/*
+ * This will get the basic headers so that memeq() and others
+ * can be defined.
+ */
+#include "xz/private.h"
+
+/*
+ * memeq and memzero are not used much and any remotely sane implementation
+ * is fast enough. memcpy/memmove speed matters in multi-call mode, but
+ * the kernel image is decompressed in single-call mode, in which only
+ * memcpy speed can matter and only if there is a lot of uncompressible data
+ * (LZMA2 stores uncompressible chunks in uncompressed form). Thus, the
+ * functions below should just be kept small; it's probably not worth
+ * optimizing for speed.
+ */
+
+#ifndef memeq
+#define memeq(p1, p2, sz) (memcmp(p1, p2, sz) == 0)
+#endif
+
+#ifndef memzero
+#define memzero(p, sz) memset(p, 0, sz)
+#endif
+
+#include "xz/crc32.c"
+#include "xz/dec_stream.c"
+#include "xz/dec_lzma2.c"
+#include "xz/dec_bcj.c"
+
+/* Size of the input and output buffers in multi-call mode */
+#define XZ_IOBUF_SIZE 4096
+
+/*
+ * This function implements the API defined in <linux/decompress/generic.h>.
+ *
+ * This wrapper will automatically choose single-call or multi-call mode
+ * of the native XZ decoder API. The single-call mode can be used only when
+ * both input and output buffers are available as a single chunk, i.e. when
+ * fill() and flush() won't be used.
+ */
+STATIC int INIT unxz(unsigned char *in, unsigned int in_size,
+                    int (*fill)(void *dest, unsigned int size),
+                    int (*flush)(void *src, unsigned int size),
+                    unsigned char *out, unsigned int *in_used,
+                    void (*error_fn)(const char *x))
+{
+       struct xz_buf b;
+       struct xz_dec *s;
+       enum xz_ret ret;
+       bool_t must_free_in = false;
+
+       set_error_fn(error_fn);
+
+       xz_crc32_init();
+
+       if (in_used != NULL)
+               *in_used = 0;
+
+       if (fill == NULL && flush == NULL)
+               s = xz_dec_init(XZ_SINGLE, 0);
+       else
+               s = xz_dec_init(XZ_DYNALLOC, (uint32_t)-1);
+
+       if (s == NULL)
+               goto error_alloc_state;
+
+       if (flush == NULL) {
+               b.out = out;
+               b.out_size = (size_t)-1;
+       } else {
+               b.out_size = XZ_IOBUF_SIZE;
+               b.out = malloc(XZ_IOBUF_SIZE);
+               if (b.out == NULL)
+                       goto error_alloc_out;
+       }
+
+       if (in == NULL) {
+               must_free_in = true;
+               in = malloc(XZ_IOBUF_SIZE);
+               if (in == NULL)
+                       goto error_alloc_in;
+       }
+
+       b.in = in;
+       b.in_pos = 0;
+       b.in_size = in_size;
+       b.out_pos = 0;
+
+       if (fill == NULL && flush == NULL) {
+               ret = xz_dec_run(s, &b);
+       } else {
+               do {
+                       if (b.in_pos == b.in_size && fill != NULL) {
+                               if (in_used != NULL)
+                                       *in_used += b.in_pos;
+
+                               b.in_pos = 0;
+
+                               in_size = fill(in, XZ_IOBUF_SIZE);
+                               if (in_size < 0) {
+                                       /*
+                                        * This isn't an optimal error code
+                                        * but it probably isn't worth making
+                                        * a new one either.
+                                        */
+                                       ret = XZ_BUF_ERROR;
+                                       break;
+                               }
+
+                               b.in_size = in_size;
+                       }
+
+                       ret = xz_dec_run(s, &b);
+
+                       if (flush != NULL && (b.out_pos == b.out_size
+                                       || (ret != XZ_OK && b.out_pos > 0))) {
+                               /*
+                                * Setting ret here may hide an error
+                                * returned by xz_dec_run(), but probably
+                                * it's not too bad.
+                                */
+                               if (flush(b.out, b.out_pos) != (int)b.out_pos)
+                                       ret = XZ_BUF_ERROR;
+
+                               b.out_pos = 0;
+                       }
+               } while (ret == XZ_OK);
+
+               if (must_free_in)
+                       free(in);
+
+               if (flush != NULL)
+                       free(b.out);
+       }
+
+       if (in_used != NULL)
+               *in_used += b.in_pos;
+
+       xz_dec_end(s);
+
+       switch (ret) {
+       case XZ_STREAM_END:
+               return 0;
+
+       case XZ_MEM_ERROR:
+               /* This can occur only in multi-call mode. */
+               error("XZ decompressor ran out of memory");
+               break;
+
+       case XZ_FORMAT_ERROR:
+               error("Input is not in the XZ format (wrong magic bytes)");
+               break;
+
+       case XZ_OPTIONS_ERROR:
+               error("Input was encoded with settings that are not "
+                               "supported by this XZ decoder");
+               break;
+
+       case XZ_DATA_ERROR:
+       case XZ_BUF_ERROR:
+               error("XZ-compressed data is corrupt");
+               break;
+
+       default:
+               error("Bug in the XZ decompressor");
+               break;
+       }
+
+       return -1;
+
+error_alloc_in:
+       if (flush != NULL)
+               free(b.out);
+
+error_alloc_out:
+       xz_dec_end(s);
+
+error_alloc_state:
+       error("XZ decompressor ran out of memory");
+       return -1;
+}
+
+/*
+ * This macro is used by architecture-specific files to decompress
+ * the kernel image.
+ */
+#define decompress unxz
diff --git a/xen/common/xz/crc32.c b/xen/common/xz/crc32.c
new file mode 100644
--- /dev/null
+++ b/xen/common/xz/crc32.c
@@ -0,0 +1,51 @@
+/*
+ * CRC32 using the polynomial from IEEE-802.3
+ *
+ * Authors: Lasse Collin <lasse.collin@tukaani.org>
+ *          Igor Pavlov <http://7-zip.org/>
+ *
+ * This file has been put into the public domain.
+ * You can do whatever you want with this file.
+ */
+
+/*
+ * This is not the fastest implementation, but it is pretty compact.
+ * The fastest versions of xz_crc32() on modern CPUs without hardware
+ * accelerated CRC instruction are 3-5 times as fast as this version,
+ * but they are bigger and use more memory for the lookup table.
+ */
+
+#include "private.h"
+
+XZ_EXTERN uint32_t INITDATA xz_crc32_table[256];
+
+XZ_EXTERN void INIT xz_crc32_init(void)
+{
+       const uint32_t poly = 0xEDB88320;
+
+       uint32_t i;
+       uint32_t j;
+       uint32_t r;
+
+       for (i = 0; i < 256; ++i) {
+               r = i;
+               for (j = 0; j < 8; ++j)
+                       r = (r >> 1) ^ (poly & ~((r & 1) - 1));
+
+               xz_crc32_table[i] = r;
+       }
+
+       return;
+}
+
+XZ_EXTERN uint32_t INIT xz_crc32(const uint8_t *buf, size_t size, uint32_t crc)
+{
+       crc = ~crc;
+
+       while (size != 0) {
+               crc = xz_crc32_table[*buf++ ^ (crc & 0xFF)] ^ (crc >> 8);
+               --size;
+       }
+
+       return ~crc;
+}
diff --git a/xen/common/xz/dec_bcj.c b/xen/common/xz/dec_bcj.c
new file mode 100644
--- /dev/null
+++ b/xen/common/xz/dec_bcj.c
@@ -0,0 +1,562 @@
+/*
+ * Branch/Call/Jump (BCJ) filter decoders
+ *
+ * Authors: Lasse Collin <lasse.collin@tukaani.org>
+ *          Igor Pavlov <http://7-zip.org/>
+ *
+ * This file has been put into the public domain.
+ * You can do whatever you want with this file.
+ */
+
+#include "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_t 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 INIT bcj_x86_test_msbyte(uint8_t b)
+{
+       return b == 0x00 || b == 0xFF;
+}
+
+static size_t INIT bcj_x86(struct xz_dec_bcj *s, uint8_t *buf, size_t size)
+{
+       static /*const*/ bool_t INITDATA mask_to_allowed_status[8]
+               = { true, true, true, false, true, false, false, false };
+
+       static /*const*/ uint8_t INITDATA 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 INIT 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 INIT 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 INIT 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 INIT 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 INIT 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 INIT 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 INIT 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 INIT 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
+        * immediatelly 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.
+        */
+       if (s->temp.size < b->out_size - b->out_pos) {
+               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 we have unfiltered data in temp, try to fill 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 (s->temp.size > 0) {
+               /* 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 *INIT xz_dec_bcj_create(bool_t single_call)
+{
+       struct xz_dec_bcj *s = malloc(sizeof(*s));
+       if (s != NULL)
+               s->single_call = single_call;
+
+       return s;
+}
+
+XZ_EXTERN enum xz_ret INIT 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
diff --git a/xen/common/xz/dec_lzma2.c b/xen/common/xz/dec_lzma2.c
new file mode 100644
--- /dev/null
+++ b/xen/common/xz/dec_lzma2.c
@@ -0,0 +1,1171 @@
+/*
+ * LZMA2 decoder
+ *
+ * Authors: Lasse Collin <lasse.collin@tukaani.org>
+ *          Igor Pavlov <http://7-zip.org/>
+ *
+ * This file has been put into the public domain.
+ * You can do whatever you want with this file.
+ */
+
+#include "private.h"
+#include "lzma2.h"
+
+/*
+ * Range decoder initialization eats the first five bytes of each LZMA chunk.
+ */
+#define RC_INIT_BYTES 5
+
+/*
+ * Minimum number of usable input buffer to safely decode one LZMA symbol.
+ * The worst case is that we decode 22 bits using probabilities and 26
+ * direct bits. This may decode at maximum of 20 bytes of input. However,
+ * lzma_main() does an extra normalization before returning, thus we
+ * need to put 21 here.
+ */
+#define LZMA_IN_REQUIRED 21
+
+/*
+ * Dictionary (history buffer)
+ *
+ * These are always true:
+ *    start <= pos <= full <= end
+ *    pos <= limit <= end
+ *
+ * In multi-call mode, also these are true:
+ *    end == size
+ *    size <= size_max
+ *    allocated <= size
+ *
+ * Most of these variables are size_t to support single-call mode,
+ * in which the dictionary variables address the actual output
+ * buffer directly.
+ */
+struct dictionary {
+       /* Beginning of the history buffer */
+       uint8_t *buf;
+
+       /* Old position in buf (before decoding more data) */
+       size_t start;
+
+       /* Position in buf */
+       size_t pos;
+
+       /*
+        * How full dictionary is. This is used to detect corrupt input that
+        * would read beyond the beginning of the uncompressed stream.
+        */
+       size_t full;
+
+       /* Write limit; we don't write to buf[limit] or later bytes. */
+       size_t limit;
+
+       /*
+        * End of the dictionary buffer. In multi-call mode, this is
+        * the same as the dictionary size. In single-call mode, this
+        * indicates the size of the output buffer.
+        */
+       size_t end;
+
+       /*
+        * Size of the dictionary as specified in Block Header. This is used
+        * together with "full" to detect corrupt input that would make us
+        * read beyond the beginning of the uncompressed stream.
+        */
+       uint32_t size;
+
+       /*
+        * Maximum allowed dictionary size in multi-call mode.
+        * This is ignored in single-call mode.
+        */
+       uint32_t size_max;
+
+       /*
+        * Amount of memory currently allocated for the dictionary.
+        * This is used only with XZ_DYNALLOC. (With XZ_PREALLOC,
+        * size_max is always the same as the allocated size.)
+        */
+       uint32_t allocated;
+
+       /* Operation mode */
+       enum xz_mode mode;
+};
+
+/* Range decoder */
+struct rc_dec {
+       uint32_t range;
+       uint32_t code;
+
+       /*
+        * Number of initializing bytes remaining to be read
+        * by rc_read_init().
+        */
+       uint32_t init_bytes_left;
+
+       /*
+        * Buffer from which we read our input. It can be either
+        * temp.buf or the caller-provided input buffer.
+        */
+       const uint8_t *in;
+       size_t in_pos;
+       size_t in_limit;
+};
+
+/* Probabilities for a length decoder. */
+struct lzma_len_dec {
+       /* Probability of match length being at least 10 */
+       uint16_t choice;
+
+       /* Probability of match length being at least 18 */
+       uint16_t choice2;
+
+       /* Probabilities for match lengths 2-9 */
+       uint16_t low[POS_STATES_MAX][LEN_LOW_SYMBOLS];
+
+       /* Probabilities for match lengths 10-17 */
+       uint16_t mid[POS_STATES_MAX][LEN_MID_SYMBOLS];
+
+       /* Probabilities for match lengths 18-273 */
+       uint16_t high[LEN_HIGH_SYMBOLS];
+};
+
+struct lzma_dec {
+       /* Distances of latest four matches */
+       uint32_t rep0;
+       uint32_t rep1;
+       uint32_t rep2;
+       uint32_t rep3;
+
+       /* Types of the most recently seen LZMA symbols */
+       enum lzma_state state;
+
+       /*
+        * Length of a match. This is updated so that dict_repeat can
+        * be called again to finish repeating the whole match.
+        */
+       uint32_t len;
+
+       /*
+        * LZMA properties or related bit masks (number of literal
+        * context bits, a mask dervied from the number of literal
+        * position bits, and a mask dervied from the number
+        * position bits)
+        */
+       uint32_t lc;
+       uint32_t literal_pos_mask; /* (1 << lp) - 1 */
+       uint32_t pos_mask;         /* (1 << pb) - 1 */
+
+       /* If 1, it's a match. Otherwise it's a single 8-bit literal. */
+       uint16_t is_match[STATES][POS_STATES_MAX];
+
+       /* If 1, it's a repeated match. The distance is one of rep0 .. rep3. */
+       uint16_t is_rep[STATES];
+
+       /*
+        * If 0, distance of a repeated match is rep0.
+        * Otherwise check is_rep1.
+        */
+       uint16_t is_rep0[STATES];
+
+       /*
+        * If 0, distance of a repeated match is rep1.
+        * Otherwise check is_rep2.
+        */
+       uint16_t is_rep1[STATES];
+
+       /* If 0, distance of a repeated match is rep2. Otherwise it is rep3. */
+       uint16_t is_rep2[STATES];
+
+       /*
+        * If 1, the repeated match has length of one byte. Otherwise
+        * the length is decoded from rep_len_decoder.
+        */
+       uint16_t is_rep0_long[STATES][POS_STATES_MAX];
+
+       /*
+        * Probability tree for the highest two bits of the match
+        * distance. There is a separate probability tree for match
+        * lengths of 2 (i.e. MATCH_LEN_MIN), 3, 4, and [5, 273].
+        */
+       uint16_t dist_slot[DIST_STATES][DIST_SLOTS];
+
+       /*
+        * Probility trees for additional bits for match distance
+        * when the distance is in the range [4, 127].
+        */
+       uint16_t dist_special[FULL_DISTANCES - DIST_MODEL_END];
+
+       /*
+        * Probability tree for the lowest four bits of a match
+        * distance that is equal to or greater than 128.
+        */
+       uint16_t dist_align[ALIGN_SIZE];
+
+       /* Length of a normal match */
+       struct lzma_len_dec match_len_dec;
+
+       /* Length of a repeated match */
+       struct lzma_len_dec rep_len_dec;
+
+       /* Probabilities of literals */
+       uint16_t literal[LITERAL_CODERS_MAX][LITERAL_CODER_SIZE];
+};
+
+struct lzma2_dec {
+       /* Position in xz_dec_lzma2_run(). */
+       enum lzma2_seq {
+               SEQ_CONTROL,
+               SEQ_UNCOMPRESSED_1,
+               SEQ_UNCOMPRESSED_2,
+               SEQ_COMPRESSED_0,
+               SEQ_COMPRESSED_1,
+               SEQ_PROPERTIES,
+               SEQ_LZMA_PREPARE,
+               SEQ_LZMA_RUN,
+               SEQ_COPY
+       } sequence;
+
+       /* Next position after decoding the compressed size of the chunk. */
+       enum lzma2_seq next_sequence;
+
+       /* Uncompressed size of LZMA chunk (2 MiB at maximum) */
+       uint32_t uncompressed;
+
+       /*
+        * Compressed size of LZMA chunk or compressed/uncompressed
+        * size of uncompressed chunk (64 KiB at maximum)
+        */
+       uint32_t compressed;
+
+       /*
+        * True if dictionary reset is needed. This is false before
+        * the first chunk (LZMA or uncompressed).
+        */
+       bool_t need_dict_reset;
+
+       /*
+        * True if new LZMA properties are needed. This is false
+        * before the first LZMA chunk.
+        */
+       bool_t need_props;
+};
+
+struct xz_dec_lzma2 {
+       /*
+        * The order below is important on x86 to reduce code size and
+        * it shouldn't hurt on other platforms. Everything up to and
+        * including lzma.pos_mask are in the first 128 bytes on x86-32,
+        * which allows using smaller instructions to access those
+        * variables. On x86-64, fewer variables fit into the first 128
+        * bytes, but this is still the best order without sacrificing
+        * the readability by splitting the structures.
+        */
+       struct rc_dec rc;
+       struct dictionary dict;
+       struct lzma2_dec lzma2;
+       struct lzma_dec lzma;
+
+       /*
+        * Temporary buffer which holds small number of input bytes between
+        * decoder calls. See lzma2_lzma() for details.
+        */
+       struct {
+               uint32_t size;
+               uint8_t buf[3 * LZMA_IN_REQUIRED];
+       } temp;
+};
+
+/**************
+ * Dictionary *
+ **************/
+
+/*
+ * Reset the dictionary state. When in single-call mode, set up the beginning
+ * of the dictionary to point to the actual output buffer.
+ */
+static void INIT dict_reset(struct dictionary *dict, struct xz_buf *b)
+{
+       if (DEC_IS_SINGLE(dict->mode)) {
+               dict->buf = b->out + b->out_pos;
+               dict->end = b->out_size - b->out_pos;
+       }
+
+       dict->start = 0;
+       dict->pos = 0;
+       dict->limit = 0;
+       dict->full = 0;
+}
+
+/* Set dictionary write limit */
+static void INIT dict_limit(struct dictionary *dict, size_t out_max)
+{
+       if (dict->end - dict->pos <= out_max)
+               dict->limit = dict->end;
+       else
+               dict->limit = dict->pos + out_max;
+}
+
+/* Return true if at least one byte can be written into the dictionary. */
+static inline bool_t INIT dict_has_space(const struct dictionary *dict)
+{
+       return dict->pos < dict->limit;
+}
+
+/*
+ * Get a byte from the dictionary at the given distance. The distance is
+ * assumed to valid, or as a special case, zero when the dictionary is
+ * still empty. This special case is needed for single-call decoding to
+ * avoid writing a '\0' to the end of the destination buffer.
+ */
+static inline uint32_t INIT dict_get(const struct dictionary *dict, uint32_t dist)
+{
+       size_t offset = dict->pos - dist - 1;
+
+       if (dist >= dict->pos)
+               offset += dict->end;
+
+       return dict->full > 0 ? dict->buf[offset] : 0;
+}
+
+/*
+ * Put one byte into the dictionary. It is assumed that there is space for it.
+ */
+static inline void INIT dict_put(struct dictionary *dict, uint8_t byte)
+{
+       dict->buf[dict->pos++] = byte;
+
+       if (dict->full < dict->pos)
+               dict->full = dict->pos;
+}
+
+/*
+ * Repeat given number of bytes from the given distance. If the distance is
+ * invalid, false is returned. On success, true is returned and *len is
+ * updated to indicate how many bytes were left to be repeated.
+ */
+static bool_t INIT dict_repeat(struct dictionary *dict, uint32_t *len, uint32_t dist)
+{
+       size_t back;
+       uint32_t left;
+
+       if (dist >= dict->full || dist >= dict->size)
+               return false;
+
+       left = min_t(size_t, dict->limit - dict->pos, *len);
+       *len -= left;
+
+       back = dict->pos - dist - 1;
+       if (dist >= dict->pos)
+               back += dict->end;
+
+       do {
+               dict->buf[dict->pos++] = dict->buf[back++];
+               if (back == dict->end)
+                       back = 0;
+       } while (--left > 0);
+
+       if (dict->full < dict->pos)
+               dict->full = dict->pos;
+
+       return true;
+}
+
+/* Copy uncompressed data as is from input to dictionary and output buffers. */
+static void INIT dict_uncompressed(struct dictionary *dict, struct xz_buf *b,
+                                  uint32_t *left)
+{
+       size_t copy_size;
+
+       while (*left > 0 && b->in_pos < b->in_size
+                       && b->out_pos < b->out_size) {
+               copy_size = min(b->in_size - b->in_pos,
+                               b->out_size - b->out_pos);
+               if (copy_size > dict->end - dict->pos)
+                       copy_size = dict->end - dict->pos;
+               if (copy_size > *left)
+                       copy_size = *left;
+
+               *left -= copy_size;
+
+               memcpy(dict->buf + dict->pos, b->in + b->in_pos, copy_size);
+               dict->pos += copy_size;
+
+               if (dict->full < dict->pos)
+                       dict->full = dict->pos;
+
+               if (DEC_IS_MULTI(dict->mode)) {
+                       if (dict->pos == dict->end)
+                               dict->pos = 0;
+
+                       memcpy(b->out + b->out_pos, b->in + b->in_pos,
+                                       copy_size);
+               }
+
+               dict->start = dict->pos;
+
+               b->out_pos += copy_size;
+               b->in_pos += copy_size;
+       }
+}
+
+/*
+ * Flush pending data from dictionary to b->out. It is assumed that there is
+ * enough space in b->out. This is guaranteed because caller uses dict_limit()
+ * before decoding data into the dictionary.
+ */
+static uint32_t INIT dict_flush(struct dictionary *dict, struct xz_buf *b)
+{
+       size_t copy_size = dict->pos - dict->start;
+
+       if (DEC_IS_MULTI(dict->mode)) {
+               if (dict->pos == dict->end)
+                       dict->pos = 0;
+
+               memcpy(b->out + b->out_pos, dict->buf + dict->start,
+                               copy_size);
+       }
+
+       dict->start = dict->pos;
+       b->out_pos += copy_size;
+       return copy_size;
+}
+
+/*****************
+ * Range decoder *
+ *****************/
+
+/* Reset the range decoder. */
+static void INIT rc_reset(struct rc_dec *rc)
+{
+       rc->range = (uint32_t)-1;
+       rc->code = 0;
+       rc->init_bytes_left = RC_INIT_BYTES;
+}
+
+/*
+ * Read the first five initial bytes into rc->code if they haven't been
+ * read already. (Yes, the first byte gets completely ignored.)
+ */
+static bool_t INIT rc_read_init(struct rc_dec *rc, struct xz_buf *b)
+{
+       while (rc->init_bytes_left > 0) {
+               if (b->in_pos == b->in_size)
+                       return false;
+
+               rc->code = (rc->code << 8) + b->in[b->in_pos++];
+               --rc->init_bytes_left;
+       }
+
+       return true;
+}
+
+/* Return true if there may not be enough input for the next decoding loop. */
+static inline bool_t INIT rc_limit_exceeded(const struct rc_dec *rc)
+{
+       return rc->in_pos > rc->in_limit;
+}
+
+/*
+ * Return true if it is possible (from point of view of range decoder) that
+ * we have reached the end of the LZMA chunk.
+ */
+static inline bool_t INIT rc_is_finished(const struct rc_dec *rc)
+{
+       return rc->code == 0;
+}
+
+/* Read the next input byte if needed. */
+static always_inline void rc_normalize(struct rc_dec *rc)
+{
+       if (rc->range < RC_TOP_VALUE) {
+               rc->range <<= RC_SHIFT_BITS;
+               rc->code = (rc->code << RC_SHIFT_BITS) + rc->in[rc->in_pos++];
+       }
+}
+
+/*
+ * Decode one bit. In some versions, this function has been splitted in three
+ * functions so that the compiler is supposed to be able to more easily avoid
+ * an extra branch. In this particular version of the LZMA decoder, this
+ * doesn't seem to be a good idea (tested with GCC 3.3.6, 3.4.6, and 4.3.3
+ * on x86). Using a non-splitted version results in nicer looking code too.
+ *
+ * NOTE: This must return an int. Do not make it return a bool or the speed
+ * of the code generated by GCC 3.x decreases 10-15 %. (GCC 4.3 doesn't care,
+ * and it generates 10-20 % faster code than GCC 3.x from this file anyway.)
+ */
+static always_inline int rc_bit(struct rc_dec *rc, uint16_t *prob)
+{
+       uint32_t bound;
+       int bit;
+
+       rc_normalize(rc);
+       bound = (rc->range >> RC_BIT_MODEL_TOTAL_BITS) * *prob;
+       if (rc->code < bound) {
+               rc->range = bound;
+               *prob += (RC_BIT_MODEL_TOTAL - *prob) >> RC_MOVE_BITS;
+               bit = 0;
+       } else {
+               rc->range -= bound;
+               rc->code -= bound;
+               *prob -= *prob >> RC_MOVE_BITS;
+               bit = 1;
+       }
+
+       return bit;
+}
+
+/* Decode a bittree starting from the most significant bit. */
+static always_inline uint32_t rc_bittree(struct rc_dec *rc,
+                                        uint16_t *probs, uint32_t limit)
+{
+       uint32_t symbol = 1;
+
+       do {
+               if (rc_bit(rc, &probs[symbol]))
+                       symbol = (symbol << 1) + 1;
+               else
+                       symbol <<= 1;
+       } while (symbol < limit);
+
+       return symbol;
+}
+
+/* Decode a bittree starting from the least significant bit. */
+static always_inline void rc_bittree_reverse(struct rc_dec *rc,
+                                            uint16_t *probs,
+                                            uint32_t *dest, uint32_t limit)
+{
+       uint32_t symbol = 1;
+       uint32_t i = 0;
+
+       do {
+               if (rc_bit(rc, &probs[symbol])) {
+                       symbol = (symbol << 1) + 1;
+                       *dest += 1 << i;
+               } else {
+                       symbol <<= 1;
+               }
+       } while (++i < limit);
+}
+
+/* Decode direct bits (fixed fifty-fifty probability) */
+static inline void INIT rc_direct(struct rc_dec *rc, uint32_t *dest, uint32_t limit)
+{
+       uint32_t mask;
+
+       do {
+               rc_normalize(rc);
+               rc->range >>= 1;
+               rc->code -= rc->range;
+               mask = (uint32_t)0 - (rc->code >> 31);
+               rc->code += rc->range & mask;
+               *dest = (*dest << 1) + (mask + 1);
+       } while (--limit > 0);
+}
+
+/********
+ * LZMA *
+ ********/
+
+/* Get pointer to literal coder probability array. */
+static uint16_t *INIT lzma_literal_probs(struct xz_dec_lzma2 *s)
+{
+       uint32_t prev_byte = dict_get(&s->dict, 0);
+       uint32_t low = prev_byte >> (8 - s->lzma.lc);
+       uint32_t high = (s->dict.pos & s->lzma.literal_pos_mask) << s->lzma.lc;
+       return s->lzma.literal[low + high];
+}
+
+/* Decode a literal (one 8-bit byte) */
+static void INIT lzma_literal(struct xz_dec_lzma2 *s)
+{
+       uint16_t *probs;
+       uint32_t symbol;
+       uint32_t match_byte;
+       uint32_t match_bit;
+       uint32_t offset;
+       uint32_t i;
+
+       probs = lzma_literal_probs(s);
+
+       if (lzma_state_is_literal(s->lzma.state)) {
+               symbol = rc_bittree(&s->rc, probs, 0x100);
+       } else {
+               symbol = 1;
+               match_byte = dict_get(&s->dict, s->lzma.rep0) << 1;
+               offset = 0x100;
+
+               do {
+                       match_bit = match_byte & offset;
+                       match_byte <<= 1;
+                       i = offset + match_bit + symbol;
+
+                       if (rc_bit(&s->rc, &probs[i])) {
+                               symbol = (symbol << 1) + 1;
+                               offset &= match_bit;
+                       } else {
+                               symbol <<= 1;
+                               offset &= ~match_bit;
+                       }
+               } while (symbol < 0x100);
+       }
+
+       dict_put(&s->dict, (uint8_t)symbol);
+       lzma_state_literal(&s->lzma.state);
+}
+
+/* Decode the length of the match into s->lzma.len. */
+static void INIT lzma_len(struct xz_dec_lzma2 *s, struct lzma_len_dec *l,
+                         uint32_t pos_state)
+{
+       uint16_t *probs;
+       uint32_t limit;
+
+       if (!rc_bit(&s->rc, &l->choice)) {
+               probs = l->low[pos_state];
+               limit = LEN_LOW_SYMBOLS;
+               s->lzma.len = MATCH_LEN_MIN;
+       } else {
+               if (!rc_bit(&s->rc, &l->choice2)) {
+                       probs = l->mid[pos_state];
+                       limit = LEN_MID_SYMBOLS;
+                       s->lzma.len = MATCH_LEN_MIN + LEN_LOW_SYMBOLS;
+               } else {
+                       probs = l->high;
+                       limit = LEN_HIGH_SYMBOLS;
+                       s->lzma.len = MATCH_LEN_MIN + LEN_LOW_SYMBOLS
+                                       + LEN_MID_SYMBOLS;
+               }
+       }
+
+       s->lzma.len += rc_bittree(&s->rc, probs, limit) - limit;
+}
+
+/* Decode a match. The distance will be stored in s->lzma.rep0. */
+static void INIT lzma_match(struct xz_dec_lzma2 *s, uint32_t pos_state)
+{
+       uint16_t *probs;
+       uint32_t dist_slot;
+       uint32_t limit;
+
+       lzma_state_match(&s->lzma.state);
+
+       s->lzma.rep3 = s->lzma.rep2;
+       s->lzma.rep2 = s->lzma.rep1;
+       s->lzma.rep1 = s->lzma.rep0;
+
+       lzma_len(s, &s->lzma.match_len_dec, pos_state);
+
+       probs = s->lzma.dist_slot[lzma_get_dist_state(s->lzma.len)];
+       dist_slot = rc_bittree(&s->rc, probs, DIST_SLOTS) - DIST_SLOTS;
+
+       if (dist_slot < DIST_MODEL_START) {
+               s->lzma.rep0 = dist_slot;
+       } else {
+               limit = (dist_slot >> 1) - 1;
+               s->lzma.rep0 = 2 + (dist_slot & 1);
+
+               if (dist_slot < DIST_MODEL_END) {
+                       s->lzma.rep0 <<= limit;
+                       probs = s->lzma.dist_special + s->lzma.rep0
+                                       - dist_slot - 1;
+                       rc_bittree_reverse(&s->rc, probs,
+                                       &s->lzma.rep0, limit);
+               } else {
+                       rc_direct(&s->rc, &s->lzma.rep0, limit - ALIGN_BITS);
+                       s->lzma.rep0 <<= ALIGN_BITS;
+                       rc_bittree_reverse(&s->rc, s->lzma.dist_align,
+                                       &s->lzma.rep0, ALIGN_BITS);
+               }
+       }
+}
+
+/*
+ * Decode a repeated match. The distance is one of the four most recently
+ * seen matches. The distance will be stored in s->lzma.rep0.
+ */
+static void INIT lzma_rep_match(struct xz_dec_lzma2 *s, uint32_t pos_state)
+{
+       uint32_t tmp;
+
+       if (!rc_bit(&s->rc, &s->lzma.is_rep0[s->lzma.state])) {
+               if (!rc_bit(&s->rc, &s->lzma.is_rep0_long[
+                               s->lzma.state][pos_state])) {
+                       lzma_state_short_rep(&s->lzma.state);
+                       s->lzma.len = 1;
+                       return;
+               }
+       } else {
+               if (!rc_bit(&s->rc, &s->lzma.is_rep1[s->lzma.state])) {
+                       tmp = s->lzma.rep1;
+               } else {
+                       if (!rc_bit(&s->rc, &s->lzma.is_rep2[s->lzma.state])) {
+                               tmp = s->lzma.rep2;
+                       } else {
+                               tmp = s->lzma.rep3;
+                               s->lzma.rep3 = s->lzma.rep2;
+                       }
+
+                       s->lzma.rep2 = s->lzma.rep1;
+               }
+
+               s->lzma.rep1 = s->lzma.rep0;
+               s->lzma.rep0 = tmp;
+       }
+
+       lzma_state_long_rep(&s->lzma.state);
+       lzma_len(s, &s->lzma.rep_len_dec, pos_state);
+}
+
+/* LZMA decoder core */
+static bool_t INIT lzma_main(struct xz_dec_lzma2 *s)
+{
+       uint32_t pos_state;
+
+       /*
+        * If the dictionary was reached during the previous call, try to
+        * finish the possibly pending repeat in the dictionary.
+        */
+       if (dict_has_space(&s->dict) && s->lzma.len > 0)
+               dict_repeat(&s->dict, &s->lzma.len, s->lzma.rep0);
+
+       /*
+        * Decode more LZMA symbols. One iteration may consume up to
+        * LZMA_IN_REQUIRED - 1 bytes.
+        */
+       while (dict_has_space(&s->dict) && !rc_limit_exceeded(&s->rc)) {
+               pos_state = s->dict.pos & s->lzma.pos_mask;
+
+               if (!rc_bit(&s->rc, &s->lzma.is_match[
+                               s->lzma.state][pos_state])) {
+                       lzma_literal(s);
+               } else {
+                       if (rc_bit(&s->rc, &s->lzma.is_rep[s->lzma.state]))
+                               lzma_rep_match(s, pos_state);
+                       else
+                               lzma_match(s, pos_state);
+
+                       if (!dict_repeat(&s->dict, &s->lzma.len, s->lzma.rep0))
+                               return false;
+               }
+       }
+
+       /*
+        * Having the range decoder always normalized when we are outside
+        * this function makes it easier to correctly handle end of the chunk.
+        */
+       rc_normalize(&s->rc);
+
+       return true;
+}
+
+/*
+ * Reset the LZMA decoder and range decoder state. Dictionary is nore reset
+ * here, because LZMA state may be reset without resetting the dictionary.
+ */
+static void INIT lzma_reset(struct xz_dec_lzma2 *s)
+{
+       uint16_t *probs;
+       size_t i;
+
+       s->lzma.state = STATE_LIT_LIT;
+       s->lzma.rep0 = 0;
+       s->lzma.rep1 = 0;
+       s->lzma.rep2 = 0;
+       s->lzma.rep3 = 0;
+
+       /*
+        * All probabilities are initialized to the same value. This hack
+        * makes the code smaller by avoiding a separate loop for each
+        * probability array.
+        *
+        * This could be optimized so that only that part of literal
+        * probabilities that are actually required. In the common case
+        * we would write 12 KiB less.
+        */
+       probs = s->lzma.is_match[0];
+       for (i = 0; i < PROBS_TOTAL; ++i)
+               probs[i] = RC_BIT_MODEL_TOTAL / 2;
+
+       rc_reset(&s->rc);
+}
+
+/*
+ * Decode and validate LZMA properties (lc/lp/pb) and calculate the bit masks
+ * from the decoded lp and pb values. On success, the LZMA decoder state is
+ * reset and true is returned.
+ */
+static bool_t INIT lzma_props(struct xz_dec_lzma2 *s, uint8_t props)
+{
+       if (props > (4 * 5 + 4) * 9 + 8)
+               return false;
+
+       s->lzma.pos_mask = 0;
+       while (props >= 9 * 5) {
+               props -= 9 * 5;
+               ++s->lzma.pos_mask;
+       }
+
+       s->lzma.pos_mask = (1 << s->lzma.pos_mask) - 1;
+
+       s->lzma.literal_pos_mask = 0;
+       while (props >= 9) {
+               props -= 9;
+               ++s->lzma.literal_pos_mask;
+       }
+
+       s->lzma.lc = props;
+
+       if (s->lzma.lc + s->lzma.literal_pos_mask > 4)
+               return false;
+
+       s->lzma.literal_pos_mask = (1 << s->lzma.literal_pos_mask) - 1;
+
+       lzma_reset(s);
+
+       return true;
+}
+
+/*********
+ * LZMA2 *
+ *********/
+
+/*
+ * The LZMA decoder assumes that if the input limit (s->rc.in_limit) hasn't
+ * been exceeded, it is safe to read up to LZMA_IN_REQUIRED bytes. This
+ * wrapper function takes care of making the LZMA decoder's assumption safe.
+ *
+ * As long as there is plenty of input left to be decoded in the current LZMA
+ * chunk, we decode directly from the caller-supplied input buffer until
+ * there's LZMA_IN_REQUIRED bytes left. Those remaining bytes are copied into
+ * s->temp.buf, which (hopefully) gets filled on the next call to this
+ * function. We decode a few bytes from the temporary buffer so that we can
+ * continue decoding from the caller-supplied input buffer again.
+ */
+static bool_t INIT lzma2_lzma(struct xz_dec_lzma2 *s, struct xz_buf *b)
+{
+       size_t in_avail;
+       uint32_t tmp;
+
+       in_avail = b->in_size - b->in_pos;
+       if (s->temp.size > 0 || s->lzma2.compressed == 0) {
+               tmp = 2 * LZMA_IN_REQUIRED - s->temp.size;
+               if (tmp > s->lzma2.compressed - s->temp.size)
+                       tmp = s->lzma2.compressed - s->temp.size;
+               if (tmp > in_avail)
+                       tmp = in_avail;
+
+               memcpy(s->temp.buf + s->temp.size, b->in + b->in_pos, tmp);
+
+               if (s->temp.size + tmp == s->lzma2.compressed) {
+                       memzero(s->temp.buf + s->temp.size + tmp,
+                                       sizeof(s->temp.buf)
+                                               - s->temp.size - tmp);
+                       s->rc.in_limit = s->temp.size + tmp;
+               } else if (s->temp.size + tmp < LZMA_IN_REQUIRED) {
+                       s->temp.size += tmp;
+                       b->in_pos += tmp;
+                       return true;
+               } else {
+                       s->rc.in_limit = s->temp.size + tmp - LZMA_IN_REQUIRED;
+               }
+
+               s->rc.in = s->temp.buf;
+               s->rc.in_pos = 0;
+
+               if (!lzma_main(s) || s->rc.in_pos > s->temp.size + tmp)
+                       return false;
+
+               s->lzma2.compressed -= s->rc.in_pos;
+
+               if (s->rc.in_pos < s->temp.size) {
+                       s->temp.size -= s->rc.in_pos;
+                       memmove(s->temp.buf, s->temp.buf + s->rc.in_pos,
+                                       s->temp.size);
+                       return true;
+               }
+
+               b->in_pos += s->rc.in_pos - s->temp.size;
+               s->temp.size = 0;
+       }
+
+       in_avail = b->in_size - b->in_pos;
+       if (in_avail >= LZMA_IN_REQUIRED) {
+               s->rc.in = b->in;
+               s->rc.in_pos = b->in_pos;
+
+               if (in_avail >= s->lzma2.compressed + LZMA_IN_REQUIRED)
+                       s->rc.in_limit = b->in_pos + s->lzma2.compressed;
+               else
+                       s->rc.in_limit = b->in_size - LZMA_IN_REQUIRED;
+
+               if (!lzma_main(s))
+                       return false;
+
+               in_avail = s->rc.in_pos - b->in_pos;
+               if (in_avail > s->lzma2.compressed)
+                       return false;
+
+               s->lzma2.compressed -= in_avail;
+               b->in_pos = s->rc.in_pos;
+       }
+
+       in_avail = b->in_size - b->in_pos;
+       if (in_avail < LZMA_IN_REQUIRED) {
+               if (in_avail > s->lzma2.compressed)
+                       in_avail = s->lzma2.compressed;
+
+               memcpy(s->temp.buf, b->in + b->in_pos, in_avail);
+               s->temp.size = in_avail;
+               b->in_pos += in_avail;
+       }
+
+       return true;
+}
+
+/*
+ * Take care of the LZMA2 control layer, and forward the job of actual LZMA
+ * decoding or copying of uncompressed chunks to other functions.
+ */
+XZ_EXTERN enum xz_ret INIT xz_dec_lzma2_run(struct xz_dec_lzma2 *s,
+                                           struct xz_buf *b)
+{
+       uint32_t tmp;
+
+       while (b->in_pos < b->in_size || s->lzma2.sequence == SEQ_LZMA_RUN) {
+               switch (s->lzma2.sequence) {
+               case SEQ_CONTROL:
+                       /*
+                        * LZMA2 control byte
+                        *
+                        * Exact values:
+                        *   0x00   End marker
+                        *   0x01   Dictionary reset followed by
+                        *          an uncompressed chunk
+                        *   0x02   Uncompressed chunk (no dictionary reset)
+                        *
+                        * Highest three bits (s->control & 0xE0):
+                        *   0xE0   Dictionary reset, new properties and state
+                        *          reset, followed by LZMA compressed chunk
+                        *   0xC0   New properties and state reset, followed
+                        *          by LZMA compressed chunk (no dictionary
+                        *          reset)
+                        *   0xA0   State reset using old properties,
+                        *          followed by LZMA compressed chunk (no
+                        *          dictionary reset)
+                        *   0x80   LZMA chunk (no dictionary or state reset)
+                        *
+                        * For LZMA compressed chunks, the lowest five bits
+                        * (s->control & 1F) are the highest bits of the
+                        * uncompressed size (bits 16-20).
+                        *
+                        * A new LZMA2 stream must begin with a dictionary
+                        * reset. The first LZMA chunk must set new
+                        * properties and reset the LZMA state.
+                        *
+                        * Values that don't match anything described above
+                        * are invalid and we return XZ_DATA_ERROR.
+                        */
+                       tmp = b->in[b->in_pos++];
+
+                       if (tmp >= 0xE0 || tmp == 0x01) {
+                               s->lzma2.need_props = true;
+                               s->lzma2.need_dict_reset = false;
+                               dict_reset(&s->dict, b);
+                       } else if (s->lzma2.need_dict_reset) {
+                               return XZ_DATA_ERROR;
+                       }
+
+                       if (tmp >= 0x80) {
+                               s->lzma2.uncompressed = (tmp & 0x1F) << 16;
+                               s->lzma2.sequence = SEQ_UNCOMPRESSED_1;
+
+                               if (tmp >= 0xC0) {
+                                       /*
+                                        * When there are new properties,
+                                        * state reset is done at
+                                        * SEQ_PROPERTIES.
+                                        */
+                                       s->lzma2.need_props = false;
+                                       s->lzma2.next_sequence
+                                                       = SEQ_PROPERTIES;
+
+                               } else if (s->lzma2.need_props) {
+                                       return XZ_DATA_ERROR;
+
+                               } else {
+                                       s->lzma2.next_sequence
+                                                       = SEQ_LZMA_PREPARE;
+                                       if (tmp >= 0xA0)
+                                               lzma_reset(s);
+                               }
+                       } else {
+                               if (tmp == 0x00)
+                                       return XZ_STREAM_END;
+
+                               if (tmp > 0x02)
+                                       return XZ_DATA_ERROR;
+
+                               s->lzma2.sequence = SEQ_COMPRESSED_0;
+                               s->lzma2.next_sequence = SEQ_COPY;
+                       }
+
+                       break;
+
+               case SEQ_UNCOMPRESSED_1:
+                       s->lzma2.uncompressed
+                                       += (uint32_t)b->in[b->in_pos++] << 8;
+                       s->lzma2.sequence = SEQ_UNCOMPRESSED_2;
+                       break;
+
+               case SEQ_UNCOMPRESSED_2:
+                       s->lzma2.uncompressed
+                                       += (uint32_t)b->in[b->in_pos++] + 1;
+                       s->lzma2.sequence = SEQ_COMPRESSED_0;
+                       break;
+
+               case SEQ_COMPRESSED_0:
+                       s->lzma2.compressed
+                                       = (uint32_t)b->in[b->in_pos++] << 8;
+                       s->lzma2.sequence = SEQ_COMPRESSED_1;
+                       break;
+
+               case SEQ_COMPRESSED_1:
+                       s->lzma2.compressed
+                                       += (uint32_t)b->in[b->in_pos++] + 1;
+                       s->lzma2.sequence = s->lzma2.next_sequence;
+                       break;
+
+               case SEQ_PROPERTIES:
+                       if (!lzma_props(s, b->in[b->in_pos++]))
+                               return XZ_DATA_ERROR;
+
+                       s->lzma2.sequence = SEQ_LZMA_PREPARE;
+
+               case SEQ_LZMA_PREPARE:
+                       if (s->lzma2.compressed < RC_INIT_BYTES)
+                               return XZ_DATA_ERROR;
+
+                       if (!rc_read_init(&s->rc, b))
+                               return XZ_OK;
+
+                       s->lzma2.compressed -= RC_INIT_BYTES;
+                       s->lzma2.sequence = SEQ_LZMA_RUN;
+
+               case SEQ_LZMA_RUN:
+                       /*
+                        * Set dictionary limit to indicate how much we want
+                        * to be encoded at maximum. Decode new data into the
+                        * dictionary. Flush the new data from dictionary to
+                        * b->out. Check if we finished decoding this chunk.
+                        * In case the dictionary got full but we didn't fill
+                        * the output buffer yet, we may run this loop
+                        * multiple times without changing s->lzma2.sequence.
+                        */
+                       dict_limit(&s->dict, min_t(size_t,
+                                       b->out_size - b->out_pos,
+                                       s->lzma2.uncompressed));
+                       if (!lzma2_lzma(s, b))
+                               return XZ_DATA_ERROR;
+
+                       s->lzma2.uncompressed -= dict_flush(&s->dict, b);
+
+                       if (s->lzma2.uncompressed == 0) {
+                               if (s->lzma2.compressed > 0 || s->lzma.len > 0
+                                               || !rc_is_finished(&s->rc))
+                                       return XZ_DATA_ERROR;
+
+                               rc_reset(&s->rc);
+                               s->lzma2.sequence = SEQ_CONTROL;
+
+                       } else if (b->out_pos == b->out_size
+                                       || (b->in_pos == b->in_size
+                                               && s->temp.size
+                                               < s->lzma2.compressed)) {
+                               return XZ_OK;
+                       }
+
+                       break;
+
+               case SEQ_COPY:
+                       dict_uncompressed(&s->dict, b, &s->lzma2.compressed);
+                       if (s->lzma2.compressed > 0)
+                               return XZ_OK;
+
+                       s->lzma2.sequence = SEQ_CONTROL;
+                       break;
+               }
+       }
+
+       return XZ_OK;
+}
+
+XZ_EXTERN struct xz_dec_lzma2 *INIT xz_dec_lzma2_create(enum xz_mode mode,
+                                                  uint32_t dict_max)
+{
+       struct xz_dec_lzma2 *s = malloc(sizeof(*s));
+       if (s == NULL)
+               return NULL;
+
+       s->dict.mode = mode;
+       s->dict.size_max = dict_max;
+
+       if (DEC_IS_PREALLOC(mode)) {
+               s->dict.buf = large_malloc(dict_max);
+               if (s->dict.buf == NULL) {
+                       free(s);
+                       return NULL;
+               }
+       } else if (DEC_IS_DYNALLOC(mode)) {
+               s->dict.buf = NULL;
+               s->dict.allocated = 0;
+       }
+
+       return s;
+}
+
+XZ_EXTERN enum xz_ret INIT xz_dec_lzma2_reset(struct xz_dec_lzma2 *s, uint8_t props)
+{
+       /* This limits dictionary size to 3 GiB to keep parsing simpler. */
+       if (props > 39)
+               return XZ_OPTIONS_ERROR;
+
+       s->dict.size = 2 + (props & 1);
+       s->dict.size <<= (props >> 1) + 11;
+
+       if (DEC_IS_MULTI(s->dict.mode)) {
+               if (s->dict.size > s->dict.size_max)
+                       return XZ_MEMLIMIT_ERROR;
+
+               s->dict.end = s->dict.size;
+
+               if (DEC_IS_DYNALLOC(s->dict.mode)) {
+                       if (s->dict.allocated < s->dict.size) {
+                               large_free(s->dict.buf);
+                               s->dict.buf = large_malloc(s->dict.size);
+                               if (s->dict.buf == NULL) {
+                                       s->dict.allocated = 0;
+                                       return XZ_MEM_ERROR;
+                               }
+                       }
+               }
+       }
+
+       s->lzma.len = 0;
+
+       s->lzma2.sequence = SEQ_CONTROL;
+       s->lzma2.need_dict_reset = true;
+
+       s->temp.size = 0;
+
+       return XZ_OK;
+}
+
+XZ_EXTERN void INIT xz_dec_lzma2_end(struct xz_dec_lzma2 *s)
+{
+       if (DEC_IS_MULTI(s->dict.mode))
+               large_free(s->dict.buf);
+
+       free(s);
+}
diff --git a/xen/common/xz/dec_stream.c b/xen/common/xz/dec_stream.c
new file mode 100644
--- /dev/null
+++ b/xen/common/xz/dec_stream.c
@@ -0,0 +1,821 @@
+/*
+ * .xz Stream decoder
+ *
+ * Author: Lasse Collin <lasse.collin@tukaani.org>
+ *
+ * This file has been put into the public domain.
+ * You can do whatever you want with this file.
+ */
+
+#include "private.h"
+#include "stream.h"
+
+/* Hash used to validate the Index field */
+struct xz_dec_hash {
+       vli_type unpadded;
+       vli_type uncompressed;
+       uint32_t crc32;
+};
+
+struct xz_dec {
+       /* Position in dec_main() */
+       enum {
+               SEQ_STREAM_HEADER,
+               SEQ_BLOCK_START,
+               SEQ_BLOCK_HEADER,
+               SEQ_BLOCK_UNCOMPRESS,
+               SEQ_BLOCK_PADDING,
+               SEQ_BLOCK_CHECK,
+               SEQ_INDEX,
+               SEQ_INDEX_PADDING,
+               SEQ_INDEX_CRC32,
+               SEQ_STREAM_FOOTER
+       } sequence;
+
+       /* Position in variable-length integers and Check fields */
+       uint32_t pos;
+
+       /* Variable-length integer decoded by dec_vli() */
+       vli_type vli;
+
+       /* Saved in_pos and out_pos */
+       size_t in_start;
+       size_t out_start;
+
+       /* CRC32 value in Block or Index */
+       uint32_t crc32;
+
+       /* Type of the integrity check calculated from uncompressed data */
+       enum xz_check check_type;
+
+       /* Operation mode */
+       enum xz_mode mode;
+
+       /*
+        * True if the next call to xz_dec_run() is allowed to return
+        * XZ_BUF_ERROR.
+        */
+       bool_t allow_buf_error;
+
+       /* Information stored in Block Header */
+       struct {
+               /*
+                * Value stored in the Compressed Size field, or
+                * VLI_UNKNOWN if Compressed Size is not present.
+                */
+               vli_type compressed;
+
+               /*
+                * Value stored in the Uncompressed Size field, or
+                * VLI_UNKNOWN if Uncompressed Size is not present.
+                */
+               vli_type uncompressed;
+
+               /* Size of the Block Header field */
+               uint32_t size;
+       } block_header;
+
+       /* Information collected when decoding Blocks */
+       struct {
+               /* Observed compressed size of the current Block */
+               vli_type compressed;
+
+               /* Observed uncompressed size of the current Block */
+               vli_type uncompressed;
+
+               /* Number of Blocks decoded so far */
+               vli_type count;
+
+               /*
+                * Hash calculated from the Block sizes. This is used to
+                * validate the Index field.
+                */
+               struct xz_dec_hash hash;
+       } block;
+
+       /* Variables needed when verifying the Index field */
+       struct {
+               /* Position in dec_index() */
+               enum {
+                       SEQ_INDEX_COUNT,
+                       SEQ_INDEX_UNPADDED,
+                       SEQ_INDEX_UNCOMPRESSED
+               } sequence;
+
+               /* Size of the Index in bytes */
+               vli_type size;
+
+               /* Number of Records (matches block.count in valid files) */
+               vli_type count;
+
+               /*
+                * Hash calculated from the Records (matches block.hash in
+                * valid files).
+                */
+               struct xz_dec_hash hash;
+       } index;
+
+       /*
+        * Temporary buffer needed to hold Stream Header, Block Header,
+        * and Stream Footer. The Block Header is the biggest (1 KiB)
+        * so we reserve space according to that. buf[] has to be aligned
+        * to a multiple of four bytes; the size_t variables before it
+        * should guarantee this.
+        */
+       struct {
+               size_t pos;
+               size_t size;
+               uint8_t buf[1024];
+       } temp;
+
+       struct xz_dec_lzma2 *lzma2;
+
+#ifdef XZ_DEC_BCJ
+       struct xz_dec_bcj *bcj;
+       bool_t bcj_active;
+#endif
+};
+
+#ifdef XZ_DEC_ANY_CHECK
+/* Sizes of the Check field with different Check IDs */
+static const uint8_t check_sizes[16] = {
+       0,
+       4, 4, 4,
+       8, 8, 8,
+       16, 16, 16,
+       32, 32, 32,
+       64, 64, 64
+};
+#endif
+
+/*
+ * Fill s->temp by copying data starting from b->in[b->in_pos]. Caller
+ * must have set s->temp.pos to indicate how much data we are supposed
+ * to copy into s->temp.buf. Return true once s->temp.pos has reached
+ * s->temp.size.
+ */
+static bool_t INIT fill_temp(struct xz_dec *s, struct xz_buf *b)
+{
+       size_t copy_size = min_t(size_t,
+                       b->in_size - b->in_pos, s->temp.size - s->temp.pos);
+
+       memcpy(s->temp.buf + s->temp.pos, b->in + b->in_pos, copy_size);
+       b->in_pos += copy_size;
+       s->temp.pos += copy_size;
+
+       if (s->temp.pos == s->temp.size) {
+               s->temp.pos = 0;
+               return true;
+       }
+
+       return false;
+}
+
+/* Decode a variable-length integer (little-endian base-128 encoding) */
+static enum xz_ret INIT dec_vli(struct xz_dec *s, const uint8_t *in,
+                               size_t *in_pos, size_t in_size)
+{
+       uint8_t byte;
+
+       if (s->pos == 0)
+               s->vli = 0;
+
+       while (*in_pos < in_size) {
+               byte = in[*in_pos];
+               ++*in_pos;
+
+               s->vli |= (vli_type)(byte & 0x7F) << s->pos;
+
+               if ((byte & 0x80) == 0) {
+                       /* Don't allow non-minimal encodings. */
+                       if (byte == 0 && s->pos != 0)
+                               return XZ_DATA_ERROR;
+
+                       s->pos = 0;
+                       return XZ_STREAM_END;
+               }
+
+               s->pos += 7;
+               if (s->pos == 7 * VLI_BYTES_MAX)
+                       return XZ_DATA_ERROR;
+       }
+
+       return XZ_OK;
+}
+
+/*
+ * Decode the Compressed Data field from a Block. Update and validate
+ * the observed compressed and uncompressed sizes of the Block so that
+ * they don't exceed the values possibly stored in the Block Header
+ * (validation assumes that no integer overflow occurs, since vli_type
+ * is normally uint64_t). Update the CRC32 if presence of the CRC32
+ * field was indicated in Stream Header.
+ *
+ * Once the decoding is finished, validate that the observed sizes match
+ * the sizes possibly stored in the Block Header. Update the hash and
+ * Block count, which are later used to validate the Index field.
+ */
+static enum xz_ret INIT dec_block(struct xz_dec *s, struct xz_buf *b)
+{
+       enum xz_ret ret;
+
+       s->in_start = b->in_pos;
+       s->out_start = b->out_pos;
+
+#ifdef XZ_DEC_BCJ
+       if (s->bcj_active)
+               ret = xz_dec_bcj_run(s->bcj, s->lzma2, b);
+       else
+#endif
+               ret = xz_dec_lzma2_run(s->lzma2, b);
+
+       s->block.compressed += b->in_pos - s->in_start;
+       s->block.uncompressed += b->out_pos - s->out_start;
+
+       /*
+        * There is no need to separately check for VLI_UNKNOWN, since
+        * the observed sizes are always smaller than VLI_UNKNOWN.
+        */
+       if (s->block.compressed > s->block_header.compressed
+                       || s->block.uncompressed
+                               > s->block_header.uncompressed)
+               return XZ_DATA_ERROR;
+
+       if (s->check_type == XZ_CHECK_CRC32)
+               s->crc32 = xz_crc32(b->out + s->out_start,
+                               b->out_pos - s->out_start, s->crc32);
+
+       if (ret == XZ_STREAM_END) {
+               if (s->block_header.compressed != VLI_UNKNOWN
+                               && s->block_header.compressed
+                                       != s->block.compressed)
+                       return XZ_DATA_ERROR;
+
+               if (s->block_header.uncompressed != VLI_UNKNOWN
+                               && s->block_header.uncompressed
+                                       != s->block.uncompressed)
+                       return XZ_DATA_ERROR;
+
+               s->block.hash.unpadded += s->block_header.size
+                               + s->block.compressed;
+
+#ifdef XZ_DEC_ANY_CHECK
+               s->block.hash.unpadded += check_sizes[s->check_type];
+#else
+               if (s->check_type == XZ_CHECK_CRC32)
+                       s->block.hash.unpadded += 4;
+#endif
+
+               s->block.hash.uncompressed += s->block.uncompressed;
+               s->block.hash.crc32 = xz_crc32(
+                               (const uint8_t *)&s->block.hash,
+                               sizeof(s->block.hash), s->block.hash.crc32);
+
+               ++s->block.count;
+       }
+
+       return ret;
+}
+
+/* Update the Index size and the CRC32 value. */
+static void INIT index_update(struct xz_dec *s, const struct xz_buf *b)
+{
+       size_t in_used = b->in_pos - s->in_start;
+       s->index.size += in_used;
+       s->crc32 = xz_crc32(b->in + s->in_start, in_used, s->crc32);
+}
+
+/*
+ * Decode the Number of Records, Unpadded Size, and Uncompressed Size
+ * fields from the Index field. That is, Index Padding and CRC32 are not
+ * decoded by this function.
+ *
+ * This can return XZ_OK (more input needed), XZ_STREAM_END (everything
+ * successfully decoded), or XZ_DATA_ERROR (input is corrupt).
+ */
+static enum xz_ret INIT dec_index(struct xz_dec *s, struct xz_buf *b)
+{
+       enum xz_ret ret;
+
+       do {
+               ret = dec_vli(s, b->in, &b->in_pos, b->in_size);
+               if (ret != XZ_STREAM_END) {
+                       index_update(s, b);
+                       return ret;
+               }
+
+               switch (s->index.sequence) {
+               case SEQ_INDEX_COUNT:
+                       s->index.count = s->vli;
+
+                       /*
+                        * Validate that the Number of Records field
+                        * indicates the same number of Records as
+                        * there were Blocks in the Stream.
+                        */
+                       if (s->index.count != s->block.count)
+                               return XZ_DATA_ERROR;
+
+                       s->index.sequence = SEQ_INDEX_UNPADDED;
+                       break;
+
+               case SEQ_INDEX_UNPADDED:
+                       s->index.hash.unpadded += s->vli;
+                       s->index.sequence = SEQ_INDEX_UNCOMPRESSED;
+                       break;
+
+               case SEQ_INDEX_UNCOMPRESSED:
+                       s->index.hash.uncompressed += s->vli;
+                       s->index.hash.crc32 = xz_crc32(
+                                       (const uint8_t *)&s->index.hash,
+                                       sizeof(s->index.hash),
+                                       s->index.hash.crc32);
+                       --s->index.count;
+                       s->index.sequence = SEQ_INDEX_UNPADDED;
+                       break;
+               }
+       } while (s->index.count > 0);
+
+       return XZ_STREAM_END;
+}
+
+/*
+ * Validate that the next four input bytes match the value of s->crc32.
+ * s->pos must be zero when starting to validate the first byte.
+ */
+static enum xz_ret INIT crc32_validate(struct xz_dec *s, struct xz_buf *b)
+{
+       do {
+               if (b->in_pos == b->in_size)
+                       return XZ_OK;
+
+               if (((s->crc32 >> s->pos) & 0xFF) != b->in[b->in_pos++])
+                       return XZ_DATA_ERROR;
+
+               s->pos += 8;
+
+       } while (s->pos < 32);
+
+       s->crc32 = 0;
+       s->pos = 0;
+
+       return XZ_STREAM_END;
+}
+
+#ifdef XZ_DEC_ANY_CHECK
+/*
+ * Skip over the Check field when the Check ID is not supported.
+ * Returns true once the whole Check field has been skipped over.
+ */
+static bool_t INIT check_skip(struct xz_dec *s, struct xz_buf *b)
+{
+       while (s->pos < check_sizes[s->check_type]) {
+               if (b->in_pos == b->in_size)
+                       return false;
+
+               ++b->in_pos;
+               ++s->pos;
+       }
+
+       s->pos = 0;
+
+       return true;
+}
+#endif
+
+/* Decode the Stream Header field (the first 12 bytes of the .xz Stream). */
+static enum xz_ret INIT dec_stream_header(struct xz_dec *s)
+{
+       if (!memeq(s->temp.buf, HEADER_MAGIC, HEADER_MAGIC_SIZE))
+               return XZ_FORMAT_ERROR;
+
+       if (xz_crc32(s->temp.buf + HEADER_MAGIC_SIZE, 2, 0)
+                       != get_le32(s->temp.buf + HEADER_MAGIC_SIZE + 2))
+               return XZ_DATA_ERROR;
+
+       if (s->temp.buf[HEADER_MAGIC_SIZE] != 0)
+               return XZ_OPTIONS_ERROR;
+
+       /*
+        * Of integrity checks, we support only none (Check ID = 0) and
+        * CRC32 (Check ID = 1). However, if XZ_DEC_ANY_CHECK is defined,
+        * we will accept other check types too, but then the check won't
+        * be verified and a warning (XZ_UNSUPPORTED_CHECK) will be given.
+        */
+       s->check_type = s->temp.buf[HEADER_MAGIC_SIZE + 1];
+
+#ifdef XZ_DEC_ANY_CHECK
+       if (s->check_type > XZ_CHECK_MAX)
+               return XZ_OPTIONS_ERROR;
+
+       if (s->check_type > XZ_CHECK_CRC32)
+               return XZ_UNSUPPORTED_CHECK;
+#else
+       if (s->check_type > XZ_CHECK_CRC32)
+               return XZ_OPTIONS_ERROR;
+#endif
+
+       return XZ_OK;
+}
+
+/* Decode the Stream Footer field (the last 12 bytes of the .xz Stream) */
+static enum xz_ret INIT dec_stream_footer(struct xz_dec *s)
+{
+       if (!memeq(s->temp.buf + 10, FOOTER_MAGIC, FOOTER_MAGIC_SIZE))
+               return XZ_DATA_ERROR;
+
+       if (xz_crc32(s->temp.buf + 4, 6, 0) != get_le32(s->temp.buf))
+               return XZ_DATA_ERROR;
+
+       /*
+        * Validate Backward Size. Note that we never added the size of the
+        * Index CRC32 field to s->index.size, thus we use s->index.size / 4
+        * instead of s->index.size / 4 - 1.
+        */
+       if ((s->index.size >> 2) != get_le32(s->temp.buf + 4))
+               return XZ_DATA_ERROR;
+
+       if (s->temp.buf[8] != 0 || s->temp.buf[9] != s->check_type)
+               return XZ_DATA_ERROR;
+
+       /*
+        * Use XZ_STREAM_END instead of XZ_OK to be more convenient
+        * for the caller.
+        */
+       return XZ_STREAM_END;
+}
+
+/* Decode the Block Header and initialize the filter chain. */
+static enum xz_ret INIT dec_block_header(struct xz_dec *s)
+{
+       enum xz_ret ret;
+
+       /*
+        * Validate the CRC32. We know that the temp buffer is at least
+        * eight bytes so this is safe.
+        */
+       s->temp.size -= 4;
+       if (xz_crc32(s->temp.buf, s->temp.size, 0)
+                       != get_le32(s->temp.buf + s->temp.size))
+               return XZ_DATA_ERROR;
+
+       s->temp.pos = 2;
+
+       /*
+        * Catch unsupported Block Flags. We support only one or two filters
+        * in the chain, so we catch that with the same test.
+        */
+#ifdef XZ_DEC_BCJ
+       if (s->temp.buf[1] & 0x3E)
+#else
+       if (s->temp.buf[1] & 0x3F)
+#endif
+               return XZ_OPTIONS_ERROR;
+
+       /* Compressed Size */
+       if (s->temp.buf[1] & 0x40) {
+               if (dec_vli(s, s->temp.buf, &s->temp.pos, s->temp.size)
+                                       != XZ_STREAM_END)
+                       return XZ_DATA_ERROR;
+
+               s->block_header.compressed = s->vli;
+       } else {
+               s->block_header.compressed = VLI_UNKNOWN;
+       }
+
+       /* Uncompressed Size */
+       if (s->temp.buf[1] & 0x80) {
+               if (dec_vli(s, s->temp.buf, &s->temp.pos, s->temp.size)
+                               != XZ_STREAM_END)
+                       return XZ_DATA_ERROR;
+
+               s->block_header.uncompressed = s->vli;
+       } else {
+               s->block_header.uncompressed = VLI_UNKNOWN;
+       }
+
+#ifdef XZ_DEC_BCJ
+       /* If there are two filters, the first one must be a BCJ filter. */
+       s->bcj_active = s->temp.buf[1] & 0x01;
+       if (s->bcj_active) {
+               if (s->temp.size - s->temp.pos < 2)
+                       return XZ_OPTIONS_ERROR;
+
+               ret = xz_dec_bcj_reset(s->bcj, s->temp.buf[s->temp.pos++]);
+               if (ret != XZ_OK)
+                       return ret;
+
+               /*
+                * We don't support custom start offset,
+                * so Size of Properties must be zero.
+                */
+               if (s->temp.buf[s->temp.pos++] != 0x00)
+                       return XZ_OPTIONS_ERROR;
+       }
+#endif
+
+       /* Valid Filter Flags always take at least two bytes. */
+       if (s->temp.size - s->temp.pos < 2)
+               return XZ_DATA_ERROR;
+
+       /* Filter ID = LZMA2 */
+       if (s->temp.buf[s->temp.pos++] != 0x21)
+               return XZ_OPTIONS_ERROR;
+
+       /* Size of Properties = 1-byte Filter Properties */
+       if (s->temp.buf[s->temp.pos++] != 0x01)
+               return XZ_OPTIONS_ERROR;
+
+       /* Filter Properties contains LZMA2 dictionary size. */
+       if (s->temp.size - s->temp.pos < 1)
+               return XZ_DATA_ERROR;
+
+       ret = xz_dec_lzma2_reset(s->lzma2, s->temp.buf[s->temp.pos++]);
+       if (ret != XZ_OK)
+               return ret;
+
+       /* The rest must be Header Padding. */
+       while (s->temp.pos < s->temp.size)
+               if (s->temp.buf[s->temp.pos++] != 0x00)
+                       return XZ_OPTIONS_ERROR;
+
+       s->temp.pos = 0;
+       s->block.compressed = 0;
+       s->block.uncompressed = 0;
+
+       return XZ_OK;
+}
+
+static enum xz_ret INIT dec_main(struct xz_dec *s, struct xz_buf *b)
+{
+       enum xz_ret ret;
+
+       /*
+        * Store the start position for the case when we are in the middle
+        * of the Index field.
+        */
+       s->in_start = b->in_pos;
+
+       while (true) {
+               switch (s->sequence) {
+               case SEQ_STREAM_HEADER:
+                       /*
+                        * Stream Header is copied to s->temp, and then
+                        * decoded from there. This way if the caller
+                        * gives us only little input at a time, we can
+                        * still keep the Stream Header decoding code
+                        * simple. Similar approach is used in many places
+                        * in this file.
+                        */
+                       if (!fill_temp(s, b))
+                               return XZ_OK;
+
+                       /*
+                        * If dec_stream_header() returns
+                        * XZ_UNSUPPORTED_CHECK, it is still possible
+                        * to continue decoding if working in multi-call
+                        * mode. Thus, update s->sequence before calling
+                        * dec_stream_header().
+                        */
+                       s->sequence = SEQ_BLOCK_START;
+
+                       ret = dec_stream_header(s);
+                       if (ret != XZ_OK)
+                               return ret;
+
+               case SEQ_BLOCK_START:
+                       /* We need one byte of input to continue. */
+                       if (b->in_pos == b->in_size)
+                               return XZ_OK;
+
+                       /* See if this is the beginning of the Index field. */
+                       if (b->in[b->in_pos] == 0) {
+                               s->in_start = b->in_pos++;
+                               s->sequence = SEQ_INDEX;
+                               break;
+                       }
+
+                       /*
+                        * Calculate the size of the Block Header and
+                        * prepare to decode it.
+                        */
+                       s->block_header.size
+                               = ((uint32_t)b->in[b->in_pos] + 1) * 4;
+
+                       s->temp.size = s->block_header.size;
+                       s->temp.pos = 0;
+                       s->sequence = SEQ_BLOCK_HEADER;
+
+               case SEQ_BLOCK_HEADER:
+                       if (!fill_temp(s, b))
+                               return XZ_OK;
+
+                       ret = dec_block_header(s);
+                       if (ret != XZ_OK)
+                               return ret;
+
+                       s->sequence = SEQ_BLOCK_UNCOMPRESS;
+
+               case SEQ_BLOCK_UNCOMPRESS:
+                       ret = dec_block(s, b);
+                       if (ret != XZ_STREAM_END)
+                               return ret;
+
+                       s->sequence = SEQ_BLOCK_PADDING;
+
+               case SEQ_BLOCK_PADDING:
+                       /*
+                        * Size of Compressed Data + Block Padding
+                        * must be a multiple of four. We don't need
+                        * s->block.compressed for anything else
+                        * anymore, so we use it here to test the size
+                        * of the Block Padding field.
+                        */
+                       while (s->block.compressed & 3) {
+                               if (b->in_pos == b->in_size)
+                                       return XZ_OK;
+
+                               if (b->in[b->in_pos++] != 0)
+                                       return XZ_DATA_ERROR;
+
+                               ++s->block.compressed;
+                       }
+
+                       s->sequence = SEQ_BLOCK_CHECK;
+
+               case SEQ_BLOCK_CHECK:
+                       if (s->check_type == XZ_CHECK_CRC32) {
+                               ret = crc32_validate(s, b);
+                               if (ret != XZ_STREAM_END)
+                                       return ret;
+                       }
+#ifdef XZ_DEC_ANY_CHECK
+                       else if (!check_skip(s, b)) {
+                               return XZ_OK;
+                       }
+#endif
+
+                       s->sequence = SEQ_BLOCK_START;
+                       break;
+
+               case SEQ_INDEX:
+                       ret = dec_index(s, b);
+                       if (ret != XZ_STREAM_END)
+                               return ret;
+
+                       s->sequence = SEQ_INDEX_PADDING;
+
+               case SEQ_INDEX_PADDING:
+                       while ((s->index.size + (b->in_pos - s->in_start))
+                                       & 3) {
+                               if (b->in_pos == b->in_size) {
+                                       index_update(s, b);
+                                       return XZ_OK;
+                               }
+
+                               if (b->in[b->in_pos++] != 0)
+                                       return XZ_DATA_ERROR;
+                       }
+
+                       /* Finish the CRC32 value and Index size. */
+                       index_update(s, b);
+
+                       /* Compare the hashes to validate the Index field. */
+                       if (!memeq(&s->block.hash, &s->index.hash,
+                                       sizeof(s->block.hash)))
+                               return XZ_DATA_ERROR;
+
+                       s->sequence = SEQ_INDEX_CRC32;
+
+               case SEQ_INDEX_CRC32:
+                       ret = crc32_validate(s, b);
+                       if (ret != XZ_STREAM_END)
+                               return ret;
+
+                       s->temp.size = STREAM_HEADER_SIZE;
+                       s->sequence = SEQ_STREAM_FOOTER;
+
+               case SEQ_STREAM_FOOTER:
+                       if (!fill_temp(s, b))
+                               return XZ_OK;
+
+                       return dec_stream_footer(s);
+               }
+       }
+
+       /* Never reached */
+}
+
+XZ_EXTERN void INIT xz_dec_reset(struct xz_dec *s)
+{
+       s->sequence = SEQ_STREAM_HEADER;
+       s->allow_buf_error = false;
+       s->pos = 0;
+       s->crc32 = 0;
+       memzero(&s->block, sizeof(s->block));
+       memzero(&s->index, sizeof(s->index));
+       s->temp.pos = 0;
+       s->temp.size = STREAM_HEADER_SIZE;
+}
+
+/*
+ * xz_dec_run() is a wrapper for dec_main() to handle some special cases in
+ * multi-call and single-call decoding.
+ *
+ * In multi-call mode, we must return XZ_BUF_ERROR when it seems clear that we
+ * are not going to make any progress anymore. This is to prevent the caller
+ * from calling us infinitely when the input file is truncated or otherwise
+ * corrupt. Since zlib-style API allows that the caller fills the input buffer
+ * only when the decoder doesn't produce any new output, we have to be careful
+ * to avoid returning XZ_BUF_ERROR too easily: XZ_BUF_ERROR is returned only
+ * after the second consecutive call to xz_dec_run() that makes no progress.
+ *
+ * In single-call mode, if we couldn't decode everything and no error
+ * occurred, either the input is truncated or the output buffer is too small.
+ * Since we know that the last input byte never produces any output, we know
+ * that if all the input was consumed and decoding wasn't finished, the file
+ * must be corrupt. Otherwise the output buffer has to be too small or the
+ * file is corrupt in a way that decoding it produces too big output.
+ *
+ * If single-call decoding fails, we reset b->in_pos and b->out_pos back to
+ * their original values. This is because with some filter chains there won't
+ * be any valid uncompressed data in the output buffer unless the decoding
+ * actually succeeds (that's the price to pay of using the output buffer as
+ * the workspace).
+ */
+XZ_EXTERN enum xz_ret INIT xz_dec_run(struct xz_dec *s, struct xz_buf *b)
+{
+       size_t in_start;
+       size_t out_start;
+       enum xz_ret ret;
+
+       if (DEC_IS_SINGLE(s->mode))
+               xz_dec_reset(s);
+
+       in_start = b->in_pos;
+       out_start = b->out_pos;
+       ret = dec_main(s, b);
+
+       if (DEC_IS_SINGLE(s->mode)) {
+               if (ret == XZ_OK)
+                       ret = b->in_pos == b->in_size
+                                       ? XZ_DATA_ERROR : XZ_BUF_ERROR;
+
+               if (ret != XZ_STREAM_END) {
+                       b->in_pos = in_start;
+                       b->out_pos = out_start;
+               }
+
+       } else if (ret == XZ_OK && in_start == b->in_pos
+                       && out_start == b->out_pos) {
+               if (s->allow_buf_error)
+                       ret = XZ_BUF_ERROR;
+
+               s->allow_buf_error = true;
+       } else {
+               s->allow_buf_error = false;
+       }
+
+       return ret;
+}
+
+XZ_EXTERN struct xz_dec *INIT xz_dec_init(enum xz_mode mode, uint32_t dict_max)
+{
+       struct xz_dec *s = malloc(sizeof(*s));
+       if (s == NULL)
+               return NULL;
+
+       s->mode = mode;
+
+#ifdef XZ_DEC_BCJ
+       s->bcj = xz_dec_bcj_create(DEC_IS_SINGLE(mode));
+       if (s->bcj == NULL)
+               goto error_bcj;
+#endif
+
+       s->lzma2 = xz_dec_lzma2_create(mode, dict_max);
+       if (s->lzma2 == NULL)
+               goto error_lzma2;
+
+       xz_dec_reset(s);
+       return s;
+
+error_lzma2:
+#ifdef XZ_DEC_BCJ
+       xz_dec_bcj_end(s->bcj);
+error_bcj:
+#endif
+       free(s);
+       return NULL;
+}
+
+XZ_EXTERN void INIT xz_dec_end(struct xz_dec *s)
+{
+       if (s != NULL) {
+               xz_dec_lzma2_end(s->lzma2);
+#ifdef XZ_DEC_BCJ
+               xz_dec_bcj_end(s->bcj);
+#endif
+               free(s);
+       }
+}
diff --git a/xen/common/xz/lzma2.h b/xen/common/xz/lzma2.h
new file mode 100644
--- /dev/null
+++ b/xen/common/xz/lzma2.h
@@ -0,0 +1,204 @@
+/*
+ * LZMA2 definitions
+ *
+ * Authors: Lasse Collin <lasse.collin@tukaani.org>
+ *          Igor Pavlov <http://7-zip.org/>
+ *
+ * This file has been put into the public domain.
+ * You can do whatever you want with this file.
+ */
+
+#ifndef XZ_LZMA2_H
+#define XZ_LZMA2_H
+
+/* Range coder constants */
+#define RC_SHIFT_BITS 8
+#define RC_TOP_BITS 24
+#define RC_TOP_VALUE (1 << RC_TOP_BITS)
+#define RC_BIT_MODEL_TOTAL_BITS 11
+#define RC_BIT_MODEL_TOTAL (1 << RC_BIT_MODEL_TOTAL_BITS)
+#define RC_MOVE_BITS 5
+
+/*
+ * Maximum number of position states. A position state is the lowest pb
+ * number of bits of the current uncompressed offset. In some places there
+ * are different sets of probabilities for different position states.
+ */
+#define POS_STATES_MAX (1 << 4)
+
+/*
+ * This enum is used to track which LZMA symbols have occurred most recently
+ * and in which order. This information is used to predict the next symbol.
+ *
+ * Symbols:
+ *  - Literal: One 8-bit byte
+ *  - Match: Repeat a chunk of data at some distance
+ *  - Long repeat: Multi-byte match at a recently seen distance
+ *  - Short repeat: One-byte repeat at a recently seen distance
+ *
+ * The symbol names are in from STATE_oldest_older_previous. REP means
+ * either short or long repeated match, and NONLIT means any non-literal.
+ */
+enum lzma_state {
+       STATE_LIT_LIT,
+       STATE_MATCH_LIT_LIT,
+       STATE_REP_LIT_LIT,
+       STATE_SHORTREP_LIT_LIT,
+       STATE_MATCH_LIT,
+       STATE_REP_LIT,
+       STATE_SHORTREP_LIT,
+       STATE_LIT_MATCH,
+       STATE_LIT_LONGREP,
+       STATE_LIT_SHORTREP,
+       STATE_NONLIT_MATCH,
+       STATE_NONLIT_REP
+};
+
+/* Total number of states */
+#define STATES 12
+
+/* The lowest 7 states indicate that the previous state was a literal. */
+#define LIT_STATES 7
+
+/* Indicate that the latest symbol was a literal. */
+static inline void INIT lzma_state_literal(enum lzma_state *state)
+{
+       if (*state <= STATE_SHORTREP_LIT_LIT)
+               *state = STATE_LIT_LIT;
+       else if (*state <= STATE_LIT_SHORTREP)
+               *state -= 3;
+       else
+               *state -= 6;
+}
+
+/* Indicate that the latest symbol was a match. */
+static inline void INIT lzma_state_match(enum lzma_state *state)
+{
+       *state = *state < LIT_STATES ? STATE_LIT_MATCH : STATE_NONLIT_MATCH;
+}
+
+/* Indicate that the latest state was a long repeated match. */
+static inline void INIT lzma_state_long_rep(enum lzma_state *state)
+{
+       *state = *state < LIT_STATES ? STATE_LIT_LONGREP : STATE_NONLIT_REP;
+}
+
+/* Indicate that the latest symbol was a short match. */
+static inline void INIT lzma_state_short_rep(enum lzma_state *state)
+{
+       *state = *state < LIT_STATES ? STATE_LIT_SHORTREP : STATE_NONLIT_REP;
+}
+
+/* Test if the previous symbol was a literal. */
+static inline bool_t INIT lzma_state_is_literal(enum lzma_state state)
+{
+       return state < LIT_STATES;
+}
+
+/* Each literal coder is divided in three sections:
+ *   - 0x001-0x0FF: Without match byte
+ *   - 0x101-0x1FF: With match byte; match bit is 0
+ *   - 0x201-0x2FF: With match byte; match bit is 1
+ *
+ * Match byte is used when the previous LZMA symbol was something else than
+ * a literal (that is, it was some kind of match).
+ */
+#define LITERAL_CODER_SIZE 0x300
+
+/* Maximum number of literal coders */
+#define LITERAL_CODERS_MAX (1 << 4)
+
+/* Minimum length of a match is two bytes. */
+#define MATCH_LEN_MIN 2
+
+/* Match length is encoded with 4, 5, or 10 bits.
+ *
+ * Length   Bits
+ *  2-9      4 = Choice=0 + 3 bits
+ * 10-17     5 = Choice=1 + Choice2=0 + 3 bits
+ * 18-273   10 = Choice=1 + Choice2=1 + 8 bits
+ */
+#define LEN_LOW_BITS 3
+#define LEN_LOW_SYMBOLS (1 << LEN_LOW_BITS)
+#define LEN_MID_BITS 3
+#define LEN_MID_SYMBOLS (1 << LEN_MID_BITS)
+#define LEN_HIGH_BITS 8
+#define LEN_HIGH_SYMBOLS (1 << LEN_HIGH_BITS)
+#define LEN_SYMBOLS (LEN_LOW_SYMBOLS + LEN_MID_SYMBOLS + LEN_HIGH_SYMBOLS)
+
+/*
+ * Maximum length of a match is 273 which is a result of the encoding
+ * described above.
+ */
+#define MATCH_LEN_MAX (MATCH_LEN_MIN + LEN_SYMBOLS - 1)
+
+/*
+ * Different sets of probabilities are used for match distances that have
+ * very short match length: Lengths of 2, 3, and 4 bytes have a separate
+ * set of probabilities for each length. The matches with longer length
+ * use a shared set of probabilities.
+ */
+#define DIST_STATES 4
+
+/*
+ * Get the index of the appropriate probability array for decoding
+ * the distance slot.
+ */
+static inline uint32_t INIT lzma_get_dist_state(uint32_t len)
+{
+       return len < DIST_STATES + MATCH_LEN_MIN
+                       ? len - MATCH_LEN_MIN : DIST_STATES - 1;
+}
+
+/*
+ * The highest two bits of a 32-bit match distance are encoded using six bits.
+ * This six-bit value is called a distance slot. This way encoding a 32-bit
+ * value takes 6-36 bits, larger values taking more bits.
+ */
+#define DIST_SLOT_BITS 6
+#define DIST_SLOTS (1 << DIST_SLOT_BITS)
+
+/* Match distances up to 127 are fully encoded using probabilities. Since
+ * the highest two bits (distance slot) are always encoded using six bits,
+ * the distances 0-3 don't need any additional bits to encode, since the
+ * distance slot itself is the same as the actual distance. DIST_MODEL_START
+ * indicates the first distance slot where at least one additional bit is
+ * needed.
+ */
+#define DIST_MODEL_START 4
+
+/*
+ * Match distances greater than 127 are encoded in three pieces:
+ *   - distance slot: the highest two bits
+ *   - direct bits: 2-26 bits below the highest two bits
+ *   - alignment bits: four lowest bits
+ *
+ * Direct bits don't use any probabilities.
+ *
+ * The distance slot value of 14 is for distances 128-191.
+ */
+#define DIST_MODEL_END 14
+
+/* Distance slots that indicate a distance <= 127. */
+#define FULL_DISTANCES_BITS (DIST_MODEL_END / 2)
+#define FULL_DISTANCES (1 << FULL_DISTANCES_BITS)
+
+/*
+ * For match distances greater than 127, only the highest two bits and the
+ * lowest four bits (alignment) is encoded using probabilities.
+ */
+#define ALIGN_BITS 4
+#define ALIGN_SIZE (1 << ALIGN_BITS)
+#define ALIGN_MASK (ALIGN_SIZE - 1)
+
+/* Total number of all probability variables */
+#define PROBS_TOTAL (1846 + LITERAL_CODERS_MAX * LITERAL_CODER_SIZE)
+
+/*
+ * LZMA remembers the four most recent match distances. Reusing these
+ * distances tends to take less space than re-encoding the actual
+ * distance value.
+ */
+#define REPS 4
+
+#endif
diff --git a/xen/common/xz/private.h b/xen/common/xz/private.h
new file mode 100644
--- /dev/null
+++ b/xen/common/xz/private.h
@@ -0,0 +1,271 @@
+/*
+ * Private includes and definitions
+ *
+ * Author: Lasse Collin <lasse.collin@tukaani.org>
+ *
+ * This file has been put into the public domain.
+ * You can do whatever you want with this file.
+ */
+
+#ifndef XZ_PRIVATE_H
+#define XZ_PRIVATE_H
+
+#include <xen/kernel.h>
+#include <asm/byteorder.h>
+#define get_le32(p) le32_to_cpup((const uint32_t *)(p))
+
+#if 1 /* ndef CONFIG_??? */
+static inline u32 INIT get_unaligned_le32(void *p)
+{
+       return le32_to_cpup(p);
+}
+
+static inline void INIT put_unaligned_le32(u32 val, void *p)
+{
+       *(__force __le32*)p = cpu_to_le32(val);
+}
+#else
+#include <asm/unaligned.h>
+
+static inline u32 INIT get_unaligned_le32(void *p)
+{
+       return le32_to_cpu(__get_unaligned(p, 4));
+}
+
+static inline void INIT put_unaligned_le32(u32 val, void *p)
+{
+       __put_unaligned(cpu_to_le32(val), p, 4);
+}
+#endif
+
+#define false 0
+#define true 1
+
+/**
+ * enum xz_mode - Operation mode
+ *
+ * @XZ_SINGLE:              Single-call mode. This uses less RAM than
+ *                          than multi-call modes, because the LZMA2
+ *                          dictionary doesn't need to be allocated as
+ *                          part of the decoder state. All required data
+ *                          structures are allocated at initialization,
+ *                          so xz_dec_run() cannot return XZ_MEM_ERROR.
+ * @XZ_PREALLOC:            Multi-call mode with preallocated LZMA2
+ *                          dictionary buffer. All data structures are
+ *                          allocated at initialization, so xz_dec_run()
+ *                          cannot return XZ_MEM_ERROR.
+ * @XZ_DYNALLOC:            Multi-call mode. The LZMA2 dictionary is
+ *                          allocated once the required size has been
+ *                          parsed from the stream headers. If the
+ *                          allocation fails, xz_dec_run() will return
+ *                          XZ_MEM_ERROR.
+ *
+ * It is possible to enable support only for a subset of the above
+ * modes at compile time by defining XZ_DEC_SINGLE, XZ_DEC_PREALLOC,
+ * or XZ_DEC_DYNALLOC. The xz_dec kernel module is always compiled
+ * with support for all operation modes, but the preboot code may
+ * be built with fewer features to minimize code size.
+ */
+enum xz_mode {
+       XZ_SINGLE,
+       XZ_PREALLOC,
+       XZ_DYNALLOC
+};
+
+/**
+ * enum xz_ret - Return codes
+ * @XZ_OK:                  Everything is OK so far. More input or more
+ *                          output space is required to continue. This
+ *                          return code is possible only in multi-call mode
+ *                          (XZ_PREALLOC or XZ_DYNALLOC).
+ * @XZ_STREAM_END:          Operation finished successfully.
+ * @XZ_UNSUPPORTED_CHECK:   Integrity check type is not supported. Decoding
+ *                          is still possible in multi-call mode by simply
+ *                          calling xz_dec_run() again.
+ *                          Note that this return value is used only if
+ *                          XZ_DEC_ANY_CHECK was defined at build time,
+ *                          which is not used in the kernel. Unsupported
+ *                          check types return XZ_OPTIONS_ERROR if
+ *                          XZ_DEC_ANY_CHECK was not defined at build time.
+ * @XZ_MEM_ERROR:           Allocating memory failed. This return code is
+ *                          possible only if the decoder was initialized
+ *                          with XZ_DYNALLOC. The amount of memory that was
+ *                          tried to be allocated was no more than the
+ *                          dict_max argument given to xz_dec_init().
+ * @XZ_MEMLIMIT_ERROR:      A bigger LZMA2 dictionary would be needed than
+ *                          allowed by the dict_max argument given to
+ *                          xz_dec_init(). This return value is possible
+ *                          only in multi-call mode (XZ_PREALLOC or
+ *                          XZ_DYNALLOC); the single-call mode (XZ_SINGLE)
+ *                          ignores the dict_max argument.
+ * @XZ_FORMAT_ERROR:        File format was not recognized (wrong magic
+ *                          bytes).
+ * @XZ_OPTIONS_ERROR:       This implementation doesn't support the requested
+ *                          compression options. In the decoder this means
+ *                          that the header CRC32 matches, but the header
+ *                          itself specifies something that we don't support.
+ * @XZ_DATA_ERROR:          Compressed data is corrupt.
+ * @XZ_BUF_ERROR:           Cannot make any progress. Details are slightly
+ *                          different between multi-call and single-call
+ *                          mode; more information below.
+ *
+ * In multi-call mode, XZ_BUF_ERROR is returned when two consecutive calls
+ * to XZ code cannot consume any input and cannot produce any new output.
+ * This happens when there is no new input available, or the output buffer
+ * is full while at least one output byte is still pending. Assuming your
+ * code is not buggy, you can get this error only when decoding a compressed
+ * stream that is truncated or otherwise corrupt.
+ *
+ * In single-call mode, XZ_BUF_ERROR is returned only when the output buffer
+ * is too small or the compressed input is corrupt in a way that makes the
+ * decoder produce more output than the caller expected. When it is
+ * (relatively) clear that the compressed input is truncated, XZ_DATA_ERROR
+ * is used instead of XZ_BUF_ERROR.
+ */
+enum xz_ret {
+       XZ_OK,
+       XZ_STREAM_END,
+       XZ_UNSUPPORTED_CHECK,
+       XZ_MEM_ERROR,
+       XZ_MEMLIMIT_ERROR,
+       XZ_FORMAT_ERROR,
+       XZ_OPTIONS_ERROR,
+       XZ_DATA_ERROR,
+       XZ_BUF_ERROR
+};
+
+/**
+ * struct xz_buf - Passing input and output buffers to XZ code
+ * @in:         Beginning of the input buffer. This may be NULL if and only
+ *              if in_pos is equal to in_size.
+ * @in_pos:     Current position in the input buffer. This must not exceed
+ *              in_size.
+ * @in_size:    Size of the input buffer
+ * @out:        Beginning of the output buffer. This may be NULL if and only
+ *              if out_pos is equal to out_size.
+ * @out_pos:    Current position in the output buffer. This must not exceed
+ *              out_size.
+ * @out_size:   Size of the output buffer
+ *
+ * Only the contents of the output buffer from out[out_pos] onward, and
+ * the variables in_pos and out_pos are modified by the XZ code.
+ */
+struct xz_buf {
+       const uint8_t *in;
+       size_t in_pos;
+       size_t in_size;
+
+       uint8_t *out;
+       size_t out_pos;
+       size_t out_size;
+};
+
+/**
+ * struct xz_dec - Opaque type to hold the XZ decoder state
+ */
+struct xz_dec;
+
+/* If no specific decoding mode is requested, enable support for all modes. */
+#if !defined(XZ_DEC_SINGLE) && !defined(XZ_DEC_PREALLOC) \
+               && !defined(XZ_DEC_DYNALLOC)
+#      define XZ_DEC_SINGLE
+#      define XZ_DEC_PREALLOC
+#      define XZ_DEC_DYNALLOC
+#endif
+
+/*
+ * The DEC_IS_foo(mode) macros are used in "if" statements. If only some
+ * of the supported modes are enabled, these macros will evaluate to true or
+ * false at compile time and thus allow the compiler to omit unneeded code.
+ */
+#ifdef XZ_DEC_SINGLE
+#      define DEC_IS_SINGLE(mode) ((mode) == XZ_SINGLE)
+#else
+#      define DEC_IS_SINGLE(mode) (false)
+#endif
+
+#ifdef XZ_DEC_PREALLOC
+#      define DEC_IS_PREALLOC(mode) ((mode) == XZ_PREALLOC)
+#else
+#      define DEC_IS_PREALLOC(mode) (false)
+#endif
+
+#ifdef XZ_DEC_DYNALLOC
+#      define DEC_IS_DYNALLOC(mode) ((mode) == XZ_DYNALLOC)
+#else
+#      define DEC_IS_DYNALLOC(mode) (false)
+#endif
+
+#if !defined(XZ_DEC_SINGLE)
+#      define DEC_IS_MULTI(mode) (true)
+#elif defined(XZ_DEC_PREALLOC) || defined(XZ_DEC_DYNALLOC)
+#      define DEC_IS_MULTI(mode) ((mode) != XZ_SINGLE)
+#else
+#      define DEC_IS_MULTI(mode) (false)
+#endif
+
+/*
+ * If any of the BCJ filter decoders are wanted, define XZ_DEC_BCJ.
+ * XZ_DEC_BCJ is used to enable generic support for BCJ decoders.
+ */
+#ifndef XZ_DEC_BCJ
+#      if defined(XZ_DEC_X86) || defined(XZ_DEC_POWERPC) \
+                       || defined(XZ_DEC_IA64) || defined(XZ_DEC_ARM) \
+                       || defined(XZ_DEC_ARM) || defined(XZ_DEC_ARMTHUMB) \
+                       || defined(XZ_DEC_SPARC)
+#              define XZ_DEC_BCJ
+#      endif
+#endif
+
+/*
+ * Allocate memory for LZMA2 decoder. xz_dec_lzma2_reset() must be used
+ * before calling xz_dec_lzma2_run().
+ */
+XZ_EXTERN struct xz_dec_lzma2 *xz_dec_lzma2_create(enum xz_mode mode,
+                                                  uint32_t dict_max);
+
+/*
+ * Decode the LZMA2 properties (one byte) and reset the decoder. Return
+ * XZ_OK on success, XZ_MEMLIMIT_ERROR if the preallocated dictionary is not
+ * big enough, and XZ_OPTIONS_ERROR if props indicates something that this
+ * decoder doesn't support.
+ */
+XZ_EXTERN enum xz_ret xz_dec_lzma2_reset(struct xz_dec_lzma2 *s,
+                                        uint8_t props);
+
+/* Decode raw LZMA2 stream from b->in to b->out. */
+XZ_EXTERN enum xz_ret xz_dec_lzma2_run(struct xz_dec_lzma2 *s,
+                                      struct xz_buf *b);
+
+/* Free the memory allocated for the LZMA2 decoder. */
+XZ_EXTERN void xz_dec_lzma2_end(struct xz_dec_lzma2 *s);
+
+#ifdef XZ_DEC_BCJ
+/*
+ * Allocate memory for BCJ decoders. xz_dec_bcj_reset() must be used before
+ * calling xz_dec_bcj_run().
+ */
+XZ_EXTERN struct xz_dec_bcj *xz_dec_bcj_create(bool_t single_call);
+
+/*
+ * Decode the Filter ID of a BCJ filter. This implementation doesn't
+ * support custom start offsets, so no decoding of Filter Properties
+ * is needed. Returns XZ_OK if the given Filter ID is supported.
+ * Otherwise XZ_OPTIONS_ERROR is returned.
+ */
+XZ_EXTERN enum xz_ret xz_dec_bcj_reset(struct xz_dec_bcj *s, uint8_t id);
+
+/*
+ * Decode raw BCJ + LZMA2 stream. This must be used only if there actually is
+ * a BCJ filter in the chain. If the chain has only LZMA2, xz_dec_lzma2_run()
+ * must be called directly.
+ */
+XZ_EXTERN enum xz_ret xz_dec_bcj_run(struct xz_dec_bcj *s,
+                                    struct xz_dec_lzma2 *lzma2,
+                                    struct xz_buf *b);
+
+/* Free the memory allocated for the BCJ filters. */
+#define xz_dec_bcj_end(s) free(s)
+#endif
+
+#endif
diff --git a/xen/common/xz/stream.h b/xen/common/xz/stream.h
new file mode 100644
--- /dev/null
+++ b/xen/common/xz/stream.h
@@ -0,0 +1,55 @@
+/*
+ * Definitions for handling the .xz file format
+ *
+ * Author: Lasse Collin <lasse.collin@tukaani.org>
+ *
+ * This file has been put into the public domain.
+ * You can do whatever you want with this file.
+ */
+
+#ifndef XZ_STREAM_H
+#define XZ_STREAM_H
+
+/*
+ * See the .xz file format specification at
+ * http://tukaani.org/xz/xz-file-format.txt
+ * to understand the container format.
+ */
+
+#define STREAM_HEADER_SIZE 12
+
+#define HEADER_MAGIC "\3757zXZ"
+#define HEADER_MAGIC_SIZE 6
+
+#define FOOTER_MAGIC "YZ"
+#define FOOTER_MAGIC_SIZE 2
+
+/*
+ * Variable-length integer can hold a 63-bit unsigned integer or a special
+ * value indicating that the value is unknown.
+ *
+ * Experimental: vli_type can be defined to uint32_t to save a few bytes
+ * in code size (no effect on speed). Doing so limits the uncompressed and
+ * compressed size of the file to less than 256 MiB and may also weaken
+ * error detection slightly.
+ */
+typedef uint64_t vli_type;
+
+#define VLI_MAX ((vli_type)-1 / 2)
+#define VLI_UNKNOWN ((vli_type)-1)
+
+/* Maximum encoded size of a VLI */
+#define VLI_BYTES_MAX (sizeof(vli_type) * 8 / 7)
+
+/* Integrity Check types */
+enum xz_check {
+       XZ_CHECK_NONE = 0,
+       XZ_CHECK_CRC32 = 1,
+       XZ_CHECK_CRC64 = 4,
+       XZ_CHECK_SHA256 = 10
+};
+
+/* Maximum possible Check ID */
+#define XZ_CHECK_MAX 15
+
+#endif
diff --git a/xen/include/xen/decompress.h b/xen/include/xen/decompress.h
--- a/xen/include/xen/decompress.h
+++ b/xen/include/xen/decompress.h
@@ -31,7 +31,7 @@
  * dependent).
  */
 
-decompress_fn bunzip2, unlzma, unlzo;
+decompress_fn bunzip2, unxz, unlzma, unlzo;
 
 int decompress(void *inbuf, unsigned int len, void *outbuf);