On Thu, Jan 19, 2006 at 04:56:35PM -0800, David S. Miller wrote: > > [NETFILTER] x_tables: Fix XT_ALIGN() macro on [at least] ppc32 > > [...] > > The fix is an ugly kludge, but it has been tested to solve the problem. Yet > > another reason to move away from the current {ip,ip6,arp,eb}tables like > > data structures. > > > > Signed-off-by: Harald Welte > > Harald, I'm going to modify this to just use u_int64_t as that > should be totally sufficient. > > It is the largest type, and will produce the desired results without > the silly structure. Sorry dave, as I just learned, it isn't. As reported by Jiri Slaby , Linus' tree now breaks on i386 :( Interestingly, on i386: __alignof__(struct _xt_align) 4 __alignof__(u_int64_t) 8 __alignof__(void *) 4 whereas on ppc: __alignof__(struct _xt_align) 8 __alignof__(u_int64_t) 8 __alignof__(void *) 4 So your assumption that __alignof__(u_int64_t) == __alignof__(struct xt_align) doesn't hold true for all archs. I would therefore recommend applying my unmodified patch, and hope that it then works on all archs simultaneously. > Some malloc() implementations use "long double" to figure out the > largest type size and alignment requirements any C type might have > on the machine. But there is no reason to use that here. Our main problem is that we have to stay compatible with old userspace programs that had a different definition for what has now become XT_ALIGN(). So independent what might be the best solution from an alignment point of view, we must match what old userspace thinks. Yes, this all sucks. And yes, we will see a new interface this year. Promised. Cheers, Harald. -- - Harald Welte http://netfilter.org/ ============================================================================ "Fragmentation is like classful addressing -- an interesting early architectural error that shows how much experimentation was going on while IP was being designed." -- Paul Vixie