[Qemu-devel] [PULL 30/42] block/dmg: support bzip2 block entry types

[Kevin Wolf]

From: Peter Wu <address@hidden>

This patch adds support for bzip2-compressed block entries as introduced
with OS X 10.4 (source: https://en.wikipedia.org/wiki/Apple_Disk_Image).

It was tested against a 5.2G "OS X Yosemite" installation image which
stores the BLXX block in the XML property list (instead of resource
forks) and has over 5k chunks.

New configure entries are added (--enable-bzip2 / --disable-bzip2) to
control inclusion of bzip2 functionality (which requires linking against
libbz2). The help message suggests that this option is needed for DMG
files, but the tests are generic enough that other parts of QEMU can use
bzip2 if needed.

The identifiers are based on http://newosxbook.com/DMG.html.

The decompression routines are based on the zlib case, but as there is
no way to reset the decompression state (unlike zlib), memory is
allocated and deallocated for every decompression. This should not be
problematic as the decompression takes most of the time and as blocks
are typically about/over 1 MiB in size, only one allocation is done
every 2000 sectors.

Signed-off-by: Peter Wu <address@hidden>
Reviewed-by: John Snow <address@hidden>
Acked-by: Paolo Bonzini <address@hidden>
Message-id: address@hidden
Signed-off-by: Stefan Hajnoczi <address@hidden>
Signed-off-by: Kevin Wolf <address@hidden>
---
 block/Makefile.objs |  1 +
 block/dmg.c         | 43 ++++++++++++++++++++++++++++++++++++++++++-
 configure           | 31 +++++++++++++++++++++++++++++++
 3 files changed, 74 insertions(+), 1 deletion(-)

diff --git a/block/Makefile.objs b/block/Makefile.objs
index 010afad..db2933e 100644
--- a/block/Makefile.objs
+++ b/block/Makefile.objs
@@ -37,5 +37,6 @@ gluster.o-libs     := $(GLUSTERFS_LIBS)
 ssh.o-cflags       := $(LIBSSH2_CFLAGS)
 ssh.o-libs         := $(LIBSSH2_LIBS)
 archipelago.o-libs := $(ARCHIPELAGO_LIBS)
+dmg.o-libs         := $(BZIP2_LIBS)
 qcow.o-libs        := -lz
 linux-aio.o-libs   := -laio
diff --git a/block/dmg.c b/block/dmg.c
index cc584b5..797fda3 100644
--- a/block/dmg.c
+++ b/block/dmg.c
@@ -26,6 +26,9 @@
 #include "qemu/bswap.h"
 #include "qemu/module.h"
 #include <zlib.h>
+#ifdef CONFIG_BZIP2
+#include <bzlib.h>
+#endif
 #include <glib.h>
 
 enum {
@@ -56,6 +59,9 @@ typedef struct BDRVDMGState {
     uint8_t *compressed_chunk;
     uint8_t *uncompressed_chunk;
     z_stream zstream;
+#ifdef CONFIG_BZIP2
+    bz_stream bzstream;
+#endif
 } BDRVDMGState;
 
 static int dmg_probe(const uint8_t *buf, int buf_size, const char *filename)
@@ -123,6 +129,7 @@ static void update_max_chunk_size(BDRVDMGState *s, uint32_t 
chunk,
 
     switch (s->types[chunk]) {
     case 0x80000005: /* zlib compressed */
+    case 0x80000006: /* bzip2 compressed */
         compressed_size = s->lengths[chunk];
         uncompressed_sectors = s->sectorcounts[chunk];
         break;
@@ -198,6 +205,9 @@ static bool dmg_is_known_block_type(uint32_t entry_type)
     case 0x00000001:    /* uncompressed */
     case 0x00000002:    /* zeroes */
     case 0x80000005:    /* zlib */
+#ifdef CONFIG_BZIP2
+    case 0x80000006:    /* bzip2 */
+#endif
         return true;
     default:
         return false;
@@ -564,13 +574,16 @@ static inline int dmg_read_chunk(BlockDriverState *bs, 
uint64_t sector_num)
     if (!is_sector_in_chunk(s, s->current_chunk, sector_num)) {
         int ret;
         uint32_t chunk = search_chunk(s, sector_num);
+#ifdef CONFIG_BZIP2
+        uint64_t total_out;
+#endif
 
         if (chunk >= s->n_chunks) {
             return -1;
         }
 
         s->current_chunk = s->n_chunks;
-        switch (s->types[chunk]) {
+        switch (s->types[chunk]) { /* block entry type */
         case 0x80000005: { /* zlib compressed */
             /* we need to buffer, because only the chunk as whole can be
              * inflated. */
@@ -594,6 +607,34 @@ static inline int dmg_read_chunk(BlockDriverState *bs, 
uint64_t sector_num)
                 return -1;
             }
             break; }
+#ifdef CONFIG_BZIP2
+        case 0x80000006: /* bzip2 compressed */
+            /* we need to buffer, because only the chunk as whole can be
+             * inflated. */
+            ret = bdrv_pread(bs->file, s->offsets[chunk],
+                             s->compressed_chunk, s->lengths[chunk]);
+            if (ret != s->lengths[chunk]) {
+                return -1;
+            }
+
+            ret = BZ2_bzDecompressInit(&s->bzstream, 0, 0);
+            if (ret != BZ_OK) {
+                return -1;
+            }
+            s->bzstream.next_in = (char *)s->compressed_chunk;
+            s->bzstream.avail_in = (unsigned int) s->lengths[chunk];
+            s->bzstream.next_out = (char *)s->uncompressed_chunk;
+            s->bzstream.avail_out = (unsigned int) 512 * 
s->sectorcounts[chunk];
+            ret = BZ2_bzDecompress(&s->bzstream);
+            total_out = ((uint64_t)s->bzstream.total_out_hi32 << 32) +
+                        s->bzstream.total_out_lo32;
+            BZ2_bzDecompressEnd(&s->bzstream);
+            if (ret != BZ_STREAM_END ||
+                total_out != 512 * s->sectorcounts[chunk]) {
+                return -1;
+            }
+            break;
+#endif /* CONFIG_BZIP2 */
         case 1: /* copy */
             ret = bdrv_pread(bs->file, s->offsets[chunk],
                              s->uncompressed_chunk, s->lengths[chunk]);
diff --git a/configure b/configure
index e00e03a..7ba4bcb 100755
--- a/configure
+++ b/configure
@@ -313,6 +313,7 @@ glx=""
 zlib="yes"
 lzo=""
 snappy=""
+bzip2=""
 guest_agent=""
 guest_agent_with_vss="no"
 vss_win32_sdk=""
@@ -1060,6 +1061,10 @@ for opt do
   ;;
   --enable-snappy) snappy="yes"
   ;;
+  --disable-bzip2) bzip2="no"
+  ;;
+  --enable-bzip2) bzip2="yes"
+  ;;
   --enable-guest-agent) guest_agent="yes"
   ;;
   --disable-guest-agent) guest_agent="no"
@@ -1374,6 +1379,8 @@ Advanced options (experts only):
   --enable-usb-redir       enable usb network redirection support
   --enable-lzo             enable the support of lzo compression library
   --enable-snappy          enable the support of snappy compression library
+  --enable-bzip2           enable the support of bzip2 compression library (for
+                           reading bzip2-compressed dmg images)
   --disable-guest-agent    disable building of the QEMU Guest Agent
   --enable-guest-agent     enable building of the QEMU Guest Agent
   --with-vss-sdk=SDK-path  enable Windows VSS support in QEMU Guest Agent
@@ -1820,6 +1827,24 @@ EOF
 fi
 
 ##########################################
+# bzip2 check
+
+if test "$bzip2" != "no" ; then
+    cat > $TMPC << EOF
+#include <bzlib.h>
+int main(void) { BZ2_bzlibVersion(); return 0; }
+EOF
+    if compile_prog "" "-lbz2" ; then
+        bzip2="yes"
+    else
+        if test "$bzip2" = "yes"; then
+            feature_not_found "libbzip2" "Install libbzip2 devel"
+        fi
+        bzip2="no"
+    fi
+fi
+
+##########################################
 # libseccomp check
 
 if test "$seccomp" != "no" ; then
@@ -4385,6 +4410,7 @@ echo "vhdx              $vhdx"
 echo "Quorum            $quorum"
 echo "lzo support       $lzo"
 echo "snappy support    $snappy"
+echo "bzip2 support     $bzip2"
 echo "NUMA host support $numa"
 
 if test "$sdl_too_old" = "yes"; then
@@ -4743,6 +4769,11 @@ if test "$snappy" = "yes" ; then
   echo "CONFIG_SNAPPY=y" >> $config_host_mak
 fi
 
+if test "$bzip2" = "yes" ; then
+  echo "CONFIG_BZIP2=y" >> $config_host_mak
+  echo "BZIP2_LIBS=-lbz2" >> $config_host_mak
+fi
+
 if test "$libiscsi" = "yes" ; then
   echo "CONFIG_LIBISCSI=m" >> $config_host_mak
   echo "LIBISCSI_CFLAGS=$libiscsi_cflags" >> $config_host_mak
-- 
1.8.3.1