On Fri, 2007-06-15 at 13:55 +0200, Andi Kleen wrote: > On Friday 15 June 2007 11:31:37 Arnd Bergmann wrote: > > One common problem with 32 bit system call and ioctl emulation > > is the different alignment rules between i386 and 64 bit machines. > > A number of drivers work around this by marking the compat > > structures as 'attribute((packed))', which is not the right > > solution because it breaks all the non-x86 architectures that > > want to use the same compat code. > > Why does it break them? It should just make them a little slower. > > The network code requires unaligned accesses to work > anyways so if your architecture doesn't support them it is already > remotely crashable.
alignof(uint64_t) is 8 on just about every 32-bit architecture except i386. Using __attribute__((packed)) for the 32-on-64 compat code is thus wrong on every 64-bit architecture except x86_64 and ia64. It's the _location_ which is wrong; the handling of unaligned loads is irrelevant (and Linux actually supports a bunch of architecture on which fixups are impossible now, btw). -- dwmw2 - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
