Re: [GIT PULL] [IPV6] COMPAT: Fix SSM applications on 64bit kernels.

[David Miller <davem@davemloft.net>]

From: YOSHIFUJI Hideaki / 吉藤英明 <yoshfuji@linux-ipv6.org>
Date: Thu, 24 Apr 2008 17:16:44 +0900 (JST)

> In article <20080424.010845.257071066.davem@davemloft.net> (at Thu, 24 Apr 2008 01:08:45 -0700 (PDT)), David Miller <davem@davemloft.net> says:
> 
> > From: YOSHIFUJI Hideaki / 吉藤英明 <yoshfuji@linux-ipv6.org>
> > Date: Thu, 24 Apr 2008 17:02:57 +0900 (JST)
> > 
> > > +#ifdef __KERNEL__
> > > +struct __compat_sockaddr_storage {
> > > +	unsigned short  ss_family;
> > > +	char		__data[_K_SS_MAXSIZE - sizeof(unsigned short)];
> > > +} __attribute__ ((aligned(4)));
> > > +#endif
> > 
> > Should include <linux/compat.h>, use compat types, and be guarded
> > by CONFIG_COMPAT.  This goes for all such structures.
> 
> Do you mean, something like this?
> 
> #ifdef __KERNEL__
> #include <linux/compat.h>
> 
> #ifdef CONFIG_COMPAT
> struct __compat_sockaddr_storage {
>    unsigned short  ss_family;
>   char            __data[_K_SS_MAXSIZE - sizeof(unsigned short)];
>  __attribute__ ((aligned(alignof(compat_uptr_t))));
> #endif
> #endif

I think first of all that ((packed)) is a better attribute to use than
the explicit alignment.

I thought we had a compat_ushort_t, but we don't.  So I guess you
can avoid the compat.h include, but you do need the CONFIG_COMPAT
guard.