dmg: Move libbz2 code to dmg-bz2.so

dmg.o was moved to block-obj-m in 5505e8b76 to become a separate module,
so that its reference to libbz2, since 6b383c08c, doesn't add an extra
library to the main executable.

Until recently, commit 06e60f70a (blockdev: Add dynamic module loading
for block drivers) moved it back to block-obj-y to simplify the design
of dynamic loading of block modules. But we don't want to lose the
feature of less library dependency on the main executable.

The solution here is to move only the bz2 related code to a separate
DSO file, and load it when dmg_open is called.

dmg_probe doesn't depend on bz2 support to work, and is the only code in
this file which can run before dmg_open.

While we are at it, fix the unhelpful cast of last argument passed to
dmg_uncompress_bz2.

Signed-off-by: Fam Zheng <famz@redhat.com>
Message-id: 1473043845-13197-4-git-send-email-famz@redhat.com
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>

4 files changed, 139 insertions, 53 deletions

diff --git a/block/Makefile.objs b/block/Makefile.objs
index 7d4031dae5..67a036a1df 100644
--- a/block/Makefile.objs
+++ b/block/Makefile.objs
@@ -41,6 +41,7 @@ gluster.o-libs     := $(GLUSTERFS_LIBS)
 ssh.o-cflags       := $(LIBSSH2_CFLAGS)
 ssh.o-libs         := $(LIBSSH2_LIBS)
 archipelago.o-libs := $(ARCHIPELAGO_LIBS)
-dmg.o-libs         := $(BZIP2_LIBS)
+block-obj-$(if $(CONFIG_BZIP2),m,n) += dmg-bz2.o
+dmg-bz2.o-libs     := $(BZIP2_LIBS)
 qcow.o-libs        := -lz
 linux-aio.o-libs   := -laio
diff --git a/block/dmg-bz2.c b/block/dmg-bz2.c
new file mode 100644
index 0000000000..9059492a9f
--- /dev/null
+++ b/block/dmg-bz2.c
@@ -0,0 +1,61 @@
+/*
+ * DMG bzip2 uncompression
+ *
+ * Copyright (c) 2004 Johannes E. Schindelin
+ * Copyright (c) 2016 Red Hat, Inc.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+#include "qemu/osdep.h"
+#include "qemu-common.h"
+#include "dmg.h"
+#include <bzlib.h>
+
+static int dmg_uncompress_bz2_do(char *next_in, unsigned int avail_in,
+                                 char *next_out, unsigned int avail_out)
+{
+    int ret;
+    uint64_t total_out;
+    bz_stream bzstream = {};
+
+    ret = BZ2_bzDecompressInit(&bzstream, 0, 0);
+    if (ret != BZ_OK) {
+        return -1;
+    }
+    bzstream.next_in = next_in;
+    bzstream.avail_in = avail_in;
+    bzstream.next_out = next_out;
+    bzstream.avail_out = avail_out;
+    ret = BZ2_bzDecompress(&bzstream);
+    total_out = ((uint64_t)bzstream.total_out_hi32 << 32) +
+                bzstream.total_out_lo32;
+    BZ2_bzDecompressEnd(&bzstream);
+    if (ret != BZ_STREAM_END ||
+        total_out != avail_out) {
+        return -1;
+    }
+    return 0;
+}
+
+__attribute__((constructor))
+static void dmg_bz2_init(void)
+{
+    assert(!dmg_uncompress_bz2);
+    dmg_uncompress_bz2 = dmg_uncompress_bz2_do;
+}
diff --git a/block/dmg.c b/block/dmg.c
index b0ed89baa7..58a3ae86c1 100644
--- a/block/dmg.c
+++ b/block/dmg.c
@@ -28,10 +28,10 @@
 #include "qemu/bswap.h"
 #include "qemu/error-report.h"
 #include "qemu/module.h"
-#include <zlib.h>
-#ifdef CONFIG_BZIP2
-#include <bzlib.h>
-#endif
+#include "dmg.h"
+
+int (*dmg_uncompress_bz2)(char *next_in, unsigned int avail_in,
+                          char *next_out, unsigned int avail_out);
 
 enum {
     /* Limit chunk sizes to prevent unreasonable amounts of memory being used
@@ -41,31 +41,6 @@ enum {
     DMG_SECTORCOUNTS_MAX = DMG_LENGTHS_MAX / 512,
 };
 
-typedef struct BDRVDMGState {
-    CoMutex lock;
-    /* each chunk contains a certain number of sectors,
-     * offsets[i] is the offset in the .dmg file,
-     * lengths[i] is the length of the compressed chunk,
-     * sectors[i] is the sector beginning at offsets[i],
-     * sectorcounts[i] is the number of sectors in that chunk,
-     * the sectors array is ordered
-     * 0<=i<n_chunks */
-
-    uint32_t n_chunks;
-    uint32_t* types;
-    uint64_t* offsets;
-    uint64_t* lengths;
-    uint64_t* sectors;
-    uint64_t* sectorcounts;
-    uint32_t current_chunk;
-    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)
 {
     int len;
@@ -210,10 +185,9 @@ 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;
+    case 0x80000006:    /* bzip2 */
+        return !!dmg_uncompress_bz2;
     default:
         return false;
     }
@@ -439,6 +413,7 @@ static int dmg_open(BlockDriverState *bs, QDict *options, int flags,
     int64_t offset;
     int ret;
 
+    block_module_load_one("dmg-bz2");
     bs->read_only = true;
 
     s->n_chunks = 0;
@@ -587,9 +562,6 @@ 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;
@@ -620,8 +592,10 @@ static inline int dmg_read_chunk(BlockDriverState *bs, uint64_t sector_num)
                 return -1;
             }
             break; }
-#ifdef CONFIG_BZIP2
         case 0x80000006: /* bzip2 compressed */
+            if (!dmg_uncompress_bz2) {
+                break;
+            }
             /* we need to buffer, because only the chunk as whole can be
              * inflated. */
             ret = bdrv_pread(bs->file, s->offsets[chunk],
@@ -630,24 +604,15 @@ static inline int dmg_read_chunk(BlockDriverState *bs, uint64_t sector_num)
                 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;
+            ret = dmg_uncompress_bz2((char *)s->compressed_chunk,
+                                     (unsigned int) s->lengths[chunk],
+                                     (char *)s->uncompressed_chunk,
+                                     (unsigned int)
+                                         (512 * s->sectorcounts[chunk]));
+            if (ret < 0) {
+                return ret;
             }
             break;
-#endif /* CONFIG_BZIP2 */
         case 1: /* copy */
             ret = bdrv_pread(bs->file, s->offsets[chunk],
                              s->uncompressed_chunk, s->lengths[chunk]);
diff --git a/block/dmg.h b/block/dmg.h
new file mode 100644
index 0000000000..b592d6fa8b
--- /dev/null
+++ b/block/dmg.h
@@ -0,0 +1,59 @@
+/*
+ * Header for DMG driver
+ *
+ * Copyright (c) 2004-2006 Fabrice Bellard
+ * Copyright (c) 2016 Red hat, Inc.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#ifndef BLOCK_DMG_H
+#define BLOCK_DMG_H
+
+#include "qemu/osdep.h"
+#include "qemu-common.h"
+#include "block/block_int.h"
+#include <zlib.h>
+
+typedef struct BDRVDMGState {
+    CoMutex lock;
+    /* each chunk contains a certain number of sectors,
+     * offsets[i] is the offset in the .dmg file,
+     * lengths[i] is the length of the compressed chunk,
+     * sectors[i] is the sector beginning at offsets[i],
+     * sectorcounts[i] is the number of sectors in that chunk,
+     * the sectors array is ordered
+     * 0<=i<n_chunks */
+
+    uint32_t n_chunks;
+    uint32_t *types;
+    uint64_t *offsets;
+    uint64_t *lengths;
+    uint64_t *sectors;
+    uint64_t *sectorcounts;
+    uint32_t current_chunk;
+    uint8_t *compressed_chunk;
+    uint8_t *uncompressed_chunk;
+    z_stream zstream;
+} BDRVDMGState;
+
+extern int (*dmg_uncompress_bz2)(char *next_in, unsigned int avail_in,
+                                 char *next_out, unsigned int avail_out);
+
+#endif