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[Qemu-devel] [PATCH v2] block: add block driver read only whitelist


From: Fam Zheng
Subject: [Qemu-devel] [PATCH v2] block: add block driver read only whitelist
Date: Wed, 29 May 2013 16:41:41 +0800

We may want to include a driver in the whitelist for read only tasks
such as diagnosing or exporting guest data (with libguestfs as a good
example). This patch introduces a readonly whitelist option, and for
backward compatibility, the old configure option --block-drv-whitelist
is now an alias to rw whitelist.

Drivers in readonly list is only permitted to open file readonly, and
returns -ENOTSUP for RW opening.

E.g. To include vmdk readonly, and others read+write:
    ./configure --target-list=x86_64-softmmu \
                --block-drv-rw-whitelist=qcow2,raw,file,qed \
                --block-drv-ro-whitelist=vmdk

Signed-off-by: Fam Zheng <address@hidden>
---
 block.c               | 43 +++++++++++++++++++++++++++----------------
 blockdev.c            |  4 ++--
 configure             | 20 +++++++++++++++-----
 include/block/block.h |  3 ++-
 scripts/create_config | 11 +++++++++--
 5 files changed, 55 insertions(+), 26 deletions(-)

diff --git a/block.c b/block.c
index 3f87489..65c0b60 100644
--- a/block.c
+++ b/block.c
@@ -328,28 +328,40 @@ BlockDriver *bdrv_find_format(const char *format_name)
     return NULL;
 }
 
-static int bdrv_is_whitelisted(BlockDriver *drv)
+static int bdrv_is_whitelisted(BlockDriver *drv, bool read_only)
 {
-    static const char *whitelist[] = {
-        CONFIG_BDRV_WHITELIST
+    static const char *whitelist_rw[] = {
+        CONFIG_BDRV_RW_WHITELIST
+    };
+    static const char *whitelist_ro[] = {
+        CONFIG_BDRV_RO_WHITELIST
     };
     const char **p;
 
-    if (!whitelist[0])
+    if (!whitelist_rw[0] && !whitelist_ro[0]) {
         return 1;               /* no whitelist, anything goes */
+    }
 
-    for (p = whitelist; *p; p++) {
+    for (p = whitelist_rw; *p; p++) {
         if (!strcmp(drv->format_name, *p)) {
             return 1;
         }
     }
+    if (read_only) {
+        for (p = whitelist_ro; *p; p++) {
+            if (!strcmp(drv->format_name, *p)) {
+                return 1;
+            }
+        }
+    }
     return 0;
 }
 
-BlockDriver *bdrv_find_whitelisted_format(const char *format_name)
+BlockDriver *bdrv_find_whitelisted_format(const char *format_name,
+                                          bool read_only)
 {
     BlockDriver *drv = bdrv_find_format(format_name);
-    return drv && bdrv_is_whitelisted(drv) ? drv : NULL;
+    return drv && bdrv_is_whitelisted(drv, read_only) ? drv : NULL;
 }
 
 typedef struct CreateCo {
@@ -684,10 +696,6 @@ static int bdrv_open_common(BlockDriverState *bs, 
BlockDriverState *file,
 
     trace_bdrv_open_common(bs, filename ?: "", flags, drv->format_name);
 
-    if (use_bdrv_whitelist && !bdrv_is_whitelisted(drv)) {
-        return -ENOTSUP;
-    }
-
     /* bdrv_open() with directly using a protocol as drv. This layer is already
      * opened, so assign it to bs (while file becomes a closed 
BlockDriverState)
      * and return immediately. */
@@ -698,9 +706,15 @@ static int bdrv_open_common(BlockDriverState *bs, 
BlockDriverState *file,
 
     bs->open_flags = flags;
     bs->buffer_alignment = 512;
+    open_flags = bdrv_open_flags(bs, flags);
+    bs->read_only = !(open_flags & BDRV_O_RDWR);
+
+    if (use_bdrv_whitelist && !bdrv_is_whitelisted(drv, bs->read_only)) {
+        return -ENOTSUP;
+    }
 
     assert(bs->copy_on_read == 0); /* bdrv_new() and bdrv_close() make it so */
-    if ((flags & BDRV_O_RDWR) && (flags & BDRV_O_COPY_ON_READ)) {
+    if (!bs->read_only && (flags & BDRV_O_COPY_ON_READ)) {
         bdrv_enable_copy_on_read(bs);
     }
 
@@ -714,9 +728,6 @@ static int bdrv_open_common(BlockDriverState *bs, 
BlockDriverState *file,
     bs->opaque = g_malloc0(drv->instance_size);
 
     bs->enable_write_cache = !!(flags & BDRV_O_CACHE_WB);
-    open_flags = bdrv_open_flags(bs, flags);
-
-    bs->read_only = !(open_flags & BDRV_O_RDWR);
 
     /* Open the image, either directly or using a protocol */
     if (drv->bdrv_file_open) {
@@ -801,7 +812,7 @@ int bdrv_file_open(BlockDriverState **pbs, const char 
*filename,
     /* Find the right block driver */
     drvname = qdict_get_try_str(options, "driver");
     if (drvname) {
-        drv = bdrv_find_whitelisted_format(drvname);
+        drv = bdrv_find_whitelisted_format(drvname, !(flags & BDRV_O_RDWR));
         qdict_del(options, "driver");
     } else if (filename) {
         drv = bdrv_find_protocol(filename);
diff --git a/blockdev.c b/blockdev.c
index d1ec99a..b9b2d10 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -477,7 +477,7 @@ DriveInfo *drive_init(QemuOpts *all_opts, 
BlockInterfaceType block_default_type)
             error_printf("\n");
             return NULL;
         }
-        drv = bdrv_find_whitelisted_format(buf);
+        drv = bdrv_find_whitelisted_format(buf, ro);
         if (!drv) {
             error_report("'%s' invalid format", buf);
             return NULL;
@@ -1096,7 +1096,7 @@ void qmp_change_blockdev(const char *device, const char 
*filename,
     }
 
     if (format) {
-        drv = bdrv_find_whitelisted_format(format);
+        drv = bdrv_find_whitelisted_format(format, bs->read_only);
         if (!drv) {
             error_set(errp, QERR_INVALID_BLOCK_FORMAT, format);
             return;
diff --git a/configure b/configure
index eb74510..a71e8a1 100755
--- a/configure
+++ b/configure
@@ -123,7 +123,8 @@ interp_prefix="/usr/gnemul/qemu-%M"
 static="no"
 cross_prefix=""
 audio_drv_list=""
-block_drv_whitelist=""
+block_drv_rw_whitelist=""
+block_drv_ro_whitelist=""
 host_cc="cc"
 libs_softmmu=""
 libs_tools=""
@@ -708,7 +709,9 @@ for opt do
   ;;
   --audio-drv-list=*) audio_drv_list="$optarg"
   ;;
-  --block-drv-whitelist=*) block_drv_whitelist=`echo "$optarg" | sed -e 's/,/ 
/g'`
+  --block-drv-rw-whitelist=*|--block-drv-whitelist=*) 
block_drv_rw_whitelist=`echo "$optarg" | sed -e 's/,/ /g'`
+  ;;
+  --block-drv-ro-whitelist=*) block_drv_ro_whitelist=`echo "$optarg" | sed -e 
's/,/ /g'`
   ;;
   --enable-debug-tcg) debug_tcg="yes"
   ;;
@@ -1105,7 +1108,12 @@ echo "  --disable-cocoa          disable Cocoa (Mac OS X 
only)"
 echo "  --enable-cocoa           enable Cocoa (default on Mac OS X)"
 echo "  --audio-drv-list=LIST    set audio drivers list:"
 echo "                           Available drivers: $audio_possible_drivers"
-echo "  --block-drv-whitelist=L  set block driver whitelist"
+echo "  --block-drv-whitelist=L  Same as --block-drv-rw-whitelist=L"
+echo "  --block-drv-rw-whitelist=L"
+echo "                           set block driver read-write whitelist"
+echo "                           (affects only QEMU, not qemu-img)"
+echo "  --block-drv-ro-whitelist=L"
+echo "                           set block driver read-only whitelist"
 echo "                           (affects only QEMU, not qemu-img)"
 echo "  --enable-mixemu          enable mixer emulation"
 echo "  --disable-xen            disable xen backend driver support"
@@ -3525,7 +3533,8 @@ echo "curses support    $curses"
 echo "curl support      $curl"
 echo "mingw32 support   $mingw32"
 echo "Audio drivers     $audio_drv_list"
-echo "Block whitelist   $block_drv_whitelist"
+echo "Block whitelist (rw) $block_drv_rw_whitelist"
+echo "Block whitelist (ro) $block_drv_ro_whitelist"
 echo "Mixer emulation   $mixemu"
 echo "VirtFS support    $virtfs"
 echo "VNC support       $vnc"
@@ -3704,7 +3713,8 @@ fi
 if test "$audio_win_int" = "yes" ; then
   echo "CONFIG_AUDIO_WIN_INT=y" >> $config_host_mak
 fi
-echo "CONFIG_BDRV_WHITELIST=$block_drv_whitelist" >> $config_host_mak
+echo "CONFIG_BDRV_RW_WHITELIST=$block_drv_rw_whitelist" >> $config_host_mak
+echo "CONFIG_BDRV_RO_WHITELIST=$block_drv_ro_whitelist" >> $config_host_mak
 if test "$mixemu" = "yes" ; then
   echo "CONFIG_MIXEMU=y" >> $config_host_mak
 fi
diff --git a/include/block/block.h b/include/block/block.h
index 1251c5c..5604418 100644
--- a/include/block/block.h
+++ b/include/block/block.h
@@ -124,7 +124,8 @@ void bdrv_init(void);
 void bdrv_init_with_whitelist(void);
 BlockDriver *bdrv_find_protocol(const char *filename);
 BlockDriver *bdrv_find_format(const char *format_name);
-BlockDriver *bdrv_find_whitelisted_format(const char *format_name);
+BlockDriver *bdrv_find_whitelisted_format(const char *format_name,
+                                          bool readonly);
 int bdrv_create(BlockDriver *drv, const char* filename,
     QEMUOptionParameter *options);
 int bdrv_create_file(const char* filename, QEMUOptionParameter *options);
diff --git a/scripts/create_config b/scripts/create_config
index c471e8c..258513a 100755
--- a/scripts/create_config
+++ b/scripts/create_config
@@ -34,8 +34,15 @@ case $line in
     done
     echo ""
     ;;
- CONFIG_BDRV_WHITELIST=*)
-    echo "#define CONFIG_BDRV_WHITELIST \\"
+ CONFIG_BDRV_RW_WHITELIST=*)
+    echo "#define CONFIG_BDRV_RW_WHITELIST\\"
+    for drv in ${line#*=}; do
+      echo "    \"${drv}\",\\"
+    done
+    echo "    NULL"
+    ;;
+ CONFIG_BDRV_RO_WHITELIST=*)
+    echo "#define CONFIG_BDRV_RO_WHITELIST\\"
     for drv in ${line#*=}; do
       echo "    \"${drv}\",\\"
     done
-- 
1.8.2.3




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