Linux Virtualization - Jul 2015 - [PATCH RESEND] virtio: Fix typecast of pointer in vring_init()

The virtio_ring.h header is used in userspace programs (ie. QEMU),
too. Here we can not assume that sizeof(pointer) is the same as
sizeof(long), e.g. when compiling for Windows, so the typecast in
vring_init() should be done with (uintptr_t) instead of (unsigned long).

Signed-off-by: Thomas Huth <thuth at redhat.com>
---
 include/uapi/linux/virtio_ring.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/uapi/linux/virtio_ring.h b/include/uapi/linux/virtio_ring.h
index 915980a..8682551 100644
--- a/include/uapi/linux/virtio_ring.h
+++ b/include/uapi/linux/virtio_ring.h
@@ -143,7 +143,7 @@ static inline void vring_init(struct vring *vr, unsigned int
num, void *p,
 	vr->num = num;
 	vr->desc = p;
 	vr->avail = p + num*sizeof(struct vring_desc);
-	vr->used = (void *)(((unsigned long)&vr->avail->ring[num] +
sizeof(__virtio16)
+	vr->used = (void *)(((uintptr_t)&vr->avail->ring[num] +
sizeof(__virtio16)
 		+ align-1) & ~(align - 1));
 }
 
-- 
1.8.3.1

On Thu, Jul 02, 2015 at 09:21:22AM +0200, Thomas Huth
wrote:
> The virtio_ring.h header is used in userspace programs (ie. QEMU),
> too. Here we can not assume that sizeof(pointer) is the same as
> sizeof(long), e.g. when compiling for Windows, so the typecast in
> vring_init() should be done with (uintptr_t) instead of (unsigned long).
> 
> Signed-off-by: Thomas Huth <thuth at redhat.com>
This seems to break some userspace too:

  INSTALL usr/include/linux/ (413 files)
  CHECK   usr/include/linux/ (413 files)
  HOSTCC  Documentation/accounting/getdelays
  HOSTCC  Documentation/connector/ucon
  HOSTCC  Documentation/mic/mpssd/mpssd.o
In file included from Documentation/mic/mpssd/mpssd.c:36:0:
./usr/include/linux/virtio_ring.h: In function ?vring_init?:
./usr/include/linux/virtio_ring.h:146:24: error: ?uintptr_t? undeclared
(first use in this function)
  vr->used = (void *)(((uintptr_t)&vr->avail->ring[num] +
sizeof(__virtio16)
                        ^
./usr/include/linux/virtio_ring.h:146:24: note: each undeclared
identifier is reported only once for each function it appears in
scripts/Makefile.host:108: recipe for target
'Documentation/mic/mpssd/mpssd.o' failed
make[3]: *** [Documentation/mic/mpssd/mpssd.o] Error 1
scripts/Makefile.build:403: recipe for target 'Documentation/mic/mpssd'
failed
make[2]: *** [Documentation/mic/mpssd] Error 2
scripts/Makefile.build:403: recipe for target 'Documentation/mic' failed
make[1]: *** [Documentation/mic] Error 2


E.g. fuse.h has this code:
#ifdef __KERNEL__
#include <linux/types.h>
#else
#include <stdint.h>
#endif

Maybe we need something similar.
> ---
>  include/uapi/linux/virtio_ring.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/include/uapi/linux/virtio_ring.h
b/include/uapi/linux/virtio_ring.h
> index 915980a..8682551 100644
> --- a/include/uapi/linux/virtio_ring.h
> +++ b/include/uapi/linux/virtio_ring.h
> @@ -143,7 +143,7 @@ static inline void vring_init(struct vring *vr,
unsigned int num, void *p,
>  	vr->num = num;
>  	vr->desc = p;
>  	vr->avail = p + num*sizeof(struct vring_desc);
> -	vr->used = (void *)(((unsigned long)&vr->avail->ring[num] +
sizeof(__virtio16)
> +	vr->used = (void *)(((uintptr_t)&vr->avail->ring[num] +
sizeof(__virtio16)
>  		+ align-1) & ~(align - 1));
>  }
>  
> -- 
> 1.8.3.1

On Sun, Jul 05, 2015 at 12:58:53PM +0200, Michael S. Tsirkin
wrote:
> On Thu, Jul 02, 2015 at 09:21:22AM +0200, Thomas Huth wrote:
> > The virtio_ring.h header is used in userspace programs (ie. QEMU),
> > too. Here we can not assume that sizeof(pointer) is the same as
> > sizeof(long), e.g. when compiling for Windows, so the typecast in
> > vring_init() should be done with (uintptr_t) instead of (unsigned
long).
> > 
> > Signed-off-by: Thomas Huth <thuth at redhat.com>
> 
> This seems to break some userspace too:
> 
>   INSTALL usr/include/linux/ (413 files)
>   CHECK   usr/include/linux/ (413 files)
>   HOSTCC  Documentation/accounting/getdelays
>   HOSTCC  Documentation/connector/ucon
>   HOSTCC  Documentation/mic/mpssd/mpssd.o
> In file included from Documentation/mic/mpssd/mpssd.c:36:0:
> ./usr/include/linux/virtio_ring.h: In function ?vring_init?:
> ./usr/include/linux/virtio_ring.h:146:24: error: ?uintptr_t? undeclared
> (first use in this function)
>   vr->used = (void *)(((uintptr_t)&vr->avail->ring[num] +
> sizeof(__virtio16)
>                         ^
> ./usr/include/linux/virtio_ring.h:146:24: note: each undeclared
> identifier is reported only once for each function it appears in
> scripts/Makefile.host:108: recipe for target
> 'Documentation/mic/mpssd/mpssd.o' failed
> make[3]: *** [Documentation/mic/mpssd/mpssd.o] Error 1
> scripts/Makefile.build:403: recipe for target
'Documentation/mic/mpssd'
> failed
> make[2]: *** [Documentation/mic/mpssd] Error 2
> scripts/Makefile.build:403: recipe for target 'Documentation/mic'
failed
> make[1]: *** [Documentation/mic] Error 2
> 
> 
> E.g. fuse.h has this code:
> #ifdef __KERNEL__
> #include <linux/types.h>
> #else
> #include <stdint.h>
> #endif
> 
> Maybe we need something similar.
The following seems to help.  Does it help the windows build?

---
 include/uapi/linux/virtio_ring.h | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/include/uapi/linux/virtio_ring.h b/include/uapi/linux/virtio_ring.h
index 8682551..c072959 100644
--- a/include/uapi/linux/virtio_ring.h
+++ b/include/uapi/linux/virtio_ring.h
@@ -31,6 +31,9 @@
  * SUCH DAMAGE.
  *
  * Copyright Rusty Russell IBM Corporation 2007. */
+#ifndef __KERNEL__
+#include <stdint.h>
+#endif
 #include <linux/types.h>
 #include <linux/virtio_types.h>
 
-- 
MST