David Laight <David.Laight@xxxxxxxxxx> wrote:
> From: Pablo Neira Ayuso
> > Sent: 08 January 2016 14:02
> > From: Florian Westphal <fw@xxxxxxxxx>
> >
> > Needed to convert the (64bit) conntrack counters to BE ordering.
> >
> ...
> > switch (priv->size) {
> > + case 8: {
> > + u64 src64;
> > +
> > + switch (priv->op) {
> > + case NFT_BYTEORDER_NTOH:
> > + for (i = 0; i < priv->len / 8; i++) {
> > + src64 = get_unaligned_be64(&src[i]);
> > + src64 = be64_to_cpu((__force __be64)src64);
> > + put_unaligned_be64(src64, &dst[i]);
> > + }
> > + break;
> > + case NFT_BYTEORDER_HTON:
> > + for (i = 0; i < priv->len / 8; i++) {
> > + src64 = get_unaligned_be64(&src[i]);
> > + src64 = (__force u64)cpu_to_be64(src64);
> > + put_unaligned_be64(src64, &dst[i]);
> > + }
> > + break;
> > + }
> > + break;
>
> That is horrid.
Yes, sorry for this, however ...
> On a little-endian system you are byteswapping the data 3 times.
> Image the code on a cpu that doesn't support misaligned transfers
> and doesn't have a byteswap instruction.
diff --git a/net/netfilter/nft_byteorder.c b/net/netfilter/nft_byteorder.c
--- a/net/netfilter/nft_byteorder.c
+++ b/net/netfilter/nft_byteorder.c
@@ -46,16 +46,16 @@ static void nft_byteorder_eval(const struct nft_expr *expr,
switch (priv->op) {
case NFT_BYTEORDER_NTOH:
for (i = 0; i < priv->len / 8; i++) {
- src64 = get_unaligned_be64(&src[i]);
+ src64 = get_unaligned((u64 *)&src[i]);
src64 = be64_to_cpu((__force __be64)src64);
- put_unaligned_be64(src64, &dst[i]);
+ put_unaligned(src64, (u64 *)&dst[i]);
}
break;
case NFT_BYTEORDER_HTON:
for (i = 0; i < priv->len / 8; i++) {
- src64 = get_unaligned_be64(&src[i]);
+ src64 = get_unaligned((u64 *)&src[i]);
src64 = (__force u64)cpu_to_be64(src64);
- put_unaligned_be64(src64, &dst[i]);
+ put_unaligned(src64, (u64 *)&dst[i]);
}
break;
}
Results in identical object code.
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