On Tue, Sep 19, 2017 at 10:38:40AM -0700, David Miller wrote:
> From: Stefan Hajnoczi <stefa...@redhat.com>
> Date: Mon, 18 Sep 2017 16:21:00 +0100
>
> > On Fri, Sep 15, 2017 at 02:14:32PM -0700, David Miller wrote:
> >> > diff --git a/include/uapi/linux/vm_sockets.h
> >> > b/include/uapi/linux/vm_sockets.h
> >> > index b4ed5d895699..4ae5c625ac56 100644
> >> > --- a/include/uapi/linux/vm_sockets.h
> >> > +++ b/include/uapi/linux/vm_sockets.h
> >> > @@ -18,6 +18,10 @@
> >> >
> >> > #include <linux/socket.h>
> >> >
> >> > +#ifndef __KERNEL__
> >> > +#include <sys/socket.h> /* struct sockaddr */
> >> > +#endif
> >> > +
> >>
> >> There is no precedence whatsoever to include sys/socket.h in _any_ UAPI
> >> header file provided by the kernel.
> >
> > <linux/if.h> does it for the same reason:
> >
> > include/uapi/linux/if.h:#include <sys/socket.h> /* for
> > struct sockaddr. */
>
> You don't need it for struct sockaddr, you need it for sa_family_t,
> the comment is very misleading.
>
> Please do as I have instructed and it will fix this problem.
No, you really cannot rely on struct sockaddr from <linux/socket.h> in
uapi headers. You can check this yourself:
$ cd /tmp && gcc -o a.o -c /usr/include/linux/vm_sockets.h
/usr/include/linux/vm_sockets.h:148:32: error: invalid application of
‘sizeof’ to incomplete type ‘struct sockaddr’
unsigned char svm_zero[sizeof(struct sockaddr) -
^~~~~~
The weird situation is:
1. When compiling the kernel, <linux/socket.h> brings in struct sockaddr
because the compiler finds include/linux/socket.h first before
include/uapi/linux/socket.h.
2. When compiling a userspace application, <linux/socket.h> does not
bring in struct sockaddr because include/uapi/linux/socket.h is
found.
This is why I added the #include <sys/socket> when !__KERNEL__. Sorry
that the commit description wasn't clear on this.
Am I misunderstanding something?
Stefan
