Linux Virtualization - Dec 2016 - [PATCH] linux/types.h: enable endian checks for all sparse builds

By now, linux is mostly endian-clean. Enabling endian-ness
checks for everyone produces about 200 new sparse warnings for me -
less than 10% over the 2000 sparse warnings already there.

Not a big deal, OTOH enabling this helps people notice
they are introducing new bugs.

So let's just drop __CHECK_ENDIAN__. Follow-up patches
can drop distinction between __bitwise and __bitwise__.

Cc: Linus Torvalds <torvalds at linux-foundation.org>
Suggested-by: Christoph Hellwig <hch at infradead.org>
Signed-off-by: Michael S. Tsirkin <mst at redhat.com>
---

Linus, could you ack this for upstream? If yes I'll
merge through my tree as a replacement for enabling
this just for virtio.

 include/uapi/linux/types.h | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/include/uapi/linux/types.h b/include/uapi/linux/types.h
index acf0979..41e5914 100644
--- a/include/uapi/linux/types.h
+++ b/include/uapi/linux/types.h
@@ -23,11 +23,7 @@
 #else
 #define __bitwise__
 #endif
-#ifdef __CHECK_ENDIAN__
 #define __bitwise __bitwise__
-#else
-#define __bitwise
-#endif
 
 typedef __u16 __bitwise __le16;
 typedef __u16 __bitwise __be16;
-- 
MST

On 12/07/16 18:29, Michael S. Tsirkin wrote:
> By now, linux is mostly endian-clean. Enabling endian-ness
> checks for everyone produces about 200 new sparse warnings for me -
> less than 10% over the 2000 sparse warnings already there.
>
> Not a big deal, OTOH enabling this helps people notice
> they are introducing new bugs.
>
> So let's just drop __CHECK_ENDIAN__. Follow-up patches
> can drop distinction between __bitwise and __bitwise__.
Hello Michael,

This patch makes a whole bunch of ccflags-y += -D__CHECK_ENDIAN__ 
statements obsolete. Have you considered to remove these statements?

Additionally, there are notable exceptions to the rule that most drivers 
are endian-clean, e.g. drivers/scsi/qla2xxx. I would appreciate it if it 
would remain possible to check such drivers with sparse without enabling 
endianness checks. Have you considered to change #ifdef __CHECK_ENDIAN__ 
into e.g. #ifndef __DONT_CHECK_ENDIAN__?

Thanks,

Bart.

On Thu, Dec 08, 2016 at 05:21:47AM +0000, Bart Van Assche
wrote:
> On 12/07/16 18:29, Michael S. Tsirkin wrote:
> > By now, linux is mostly endian-clean. Enabling endian-ness
> > checks for everyone produces about 200 new sparse warnings for me -
> > less than 10% over the 2000 sparse warnings already there.
> >
> > Not a big deal, OTOH enabling this helps people notice
> > they are introducing new bugs.
> >
> > So let's just drop __CHECK_ENDIAN__. Follow-up patches
> > can drop distinction between __bitwise and __bitwise__.
> 
> Hello Michael,
> 
> This patch makes a whole bunch of ccflags-y += -D__CHECK_ENDIAN__ 
> statements obsolete. Have you considered to remove these statements?
Absolutely. Just waiting for feedback on the idea.
> Additionally, there are notable exceptions to the rule that most drivers 
> are endian-clean, e.g. drivers/scsi/qla2xxx. I would appreciate it if it 
> would remain possible to check such drivers with sparse without enabling 
> endianness checks. Have you considered to change #ifdef __CHECK_ENDIAN__ 
> into e.g. #ifndef __DONT_CHECK_ENDIAN__?
> 
> Thanks,
> 
> Bart.
The right thing is probably just to fix these, isn't it?
Until then, why not just ignore the warnings?

-- 
MST

On Thu, 8 Dec 2016 04:29:39 +0200
"Michael S. Tsirkin" <mst at redhat.com> wrote:
> By now, linux is mostly endian-clean. Enabling endian-ness
> checks for everyone produces about 200 new sparse warnings for me -
> less than 10% over the 2000 sparse warnings already there.
Out of curiousity: Where do most of those warnings show up?
> 
> Not a big deal, OTOH enabling this helps people notice
> they are introducing new bugs.
> 
> So let's just drop __CHECK_ENDIAN__. Follow-up patches
> can drop distinction between __bitwise and __bitwise__.
> 
> Cc: Linus Torvalds <torvalds at linux-foundation.org>
> Suggested-by: Christoph Hellwig <hch at infradead.org>
> Signed-off-by: Michael S. Tsirkin <mst at redhat.com>
> ---
> 
> Linus, could you ack this for upstream? If yes I'll
> merge through my tree as a replacement for enabling
> this just for virtio.
> 
>  include/uapi/linux/types.h | 4 ----
>  1 file changed, 4 deletions(-)
> 
> diff --git a/include/uapi/linux/types.h b/include/uapi/linux/types.h
> index acf0979..41e5914 100644
> --- a/include/uapi/linux/types.h
> +++ b/include/uapi/linux/types.h
> @@ -23,11 +23,7 @@
>  #else
>  #define __bitwise__
>  #endif
> -#ifdef __CHECK_ENDIAN__
>  #define __bitwise __bitwise__
> -#else
> -#define __bitwise
> -#endif
> 
>  typedef __u16 __bitwise __le16;
>  typedef __u16 __bitwise __be16;
FWIW, I like this better than just enabling it for the virtio code.