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[1/5] qcow1: Make padding in the header explicit

Message ID 1399899851-5641-2-git-send-email-kwolf@redhat.com
State New
Headers show

Commit Message

Kevin Wolf May 12, 2014, 1:04 p.m. UTC 
We were relying on all compilers inserting the same padding in the
header struct that is used for the on-disk format. Let's not do that.
Mark the struct as packed and insert an explicit padding field for
compatibility.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
 block/qcow.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

Comments

Benoît Canet May 12, 2014, 2:39 p.m. UTC | #1 
The Monday 12 May 2014 à 15:04:07 (+0200), Kevin Wolf wrote :
> We were relying on all compilers inserting the same padding in the
> header struct that is used for the on-disk format. Let's not do that.
> Mark the struct as packed and insert an explicit padding field for
> compatibility.
> 
> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> ---
>  block/qcow.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/block/qcow.c b/block/qcow.c
> index 937dd6d..3684794 100644
> --- a/block/qcow.c
> +++ b/block/qcow.c
> @@ -48,9 +48,10 @@ typedef struct QCowHeader {
>      uint64_t size; /* in bytes */
>      uint8_t cluster_bits;
>      uint8_t l2_bits;
> +    uint16_t padding;
>      uint32_t crypt_method;
>      uint64_t l1_table_offset;
> -} QCowHeader;
> +} QEMU_PACKED QCowHeader;
>  
>  #define L2_CACHE_SIZE 16
>  
> -- 
> 1.8.3.1
> 
> 
Reviewed-by: Benoit Canet <benoit@irqsave.net>
diff mbox

Patch

diff --git a/block/qcow.c b/block/qcow.c
index 937dd6d..3684794 100644
--- a/block/qcow.c
+++ b/block/qcow.c
@@ -48,9 +48,10 @@  typedef struct QCowHeader {
     uint64_t size; /* in bytes */
     uint8_t cluster_bits;
     uint8_t l2_bits;
+    uint16_t padding;
     uint32_t crypt_method;
     uint64_t l1_table_offset;
-} QCowHeader;
+} QEMU_PACKED QCowHeader;
 
 #define L2_CACHE_SIZE 16