From: Jan Engelhardt <jengelh@xxxxxxxxxxxxxxx> Date: Sun, 3 Jun 2007 12:26:45 +0200 (MEST) > > On Jun 3 2007 12:14, Bernhard R. Link wrote: > > > >* David Miller <davem@xxxxxxxxxxxxx> [070602 22:09]: > >> Types must be aligned on their natural size, and GCC can assume > >> this everywhere you reference such types unless you use the > >> "packed" GCC attribute. > > > >And even with packed, the struct itself must be naturally aligned > >(unless itself is in a packed struct, if course). > > It is not a struct actually. It is a bytestream that is reinterpreted > as an integer, that is, for example (it does not really need to be > skb_network_header), > > unsigned char *p = skb_network_header(skb); > uint32_t value = *(uint32_t *)(p[9]); > > I suppose this won't work, so one would have to... > > uint32_t value = (p[0] << 24) | (p[1] << 16) | (p[2] << 8) | p[3]; We have a way to handle this in the kernel, it's called get_unaligned() and it only emits special unaligned handling on the platforms that require it: value = get_unaligned((u32 *)(p + 9)); Use it :-) - To unsubscribe from this list: send the line "unsubscribe sparclinux" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
