Re: [Qemu-devel] [PATCH] slirp: Use lduw_be_p in slirp_input

[Samuel Thibault <samuel.thibault@gnu.org>]

Hello,

Richard Henderson, le mer. 26 déc. 2018 14:42:54 +1100, a ecrit:
> The pointer may be unaligned, so we must use our routines for that.
> At the same time, we might as well use the big-endian version
> instead of ntohs.
> 
> This fixes sparc64 host SIGBUS during pxe boot.

I'm not at ease with applying this, when Marc-André is trying to make
slirp an external library...  I'd rather apply the change below, could
somebody review it?

Samuel


slirp: Avoid unaligned 16bit memory access

pkt parameter may be unaligned, so we must access it byte-wise.

This fixes sparc64 host SIGBUS during pxe boot.

Signed-off-by: Samuel Thibault <samuel.thibault@ens-lyon.org>

diff --git a/slirp/slirp.c b/slirp/slirp.c
index ab2fc4eb8b..0e41d5aedf 100644
--- a/slirp/slirp.c
+++ b/slirp/slirp.c
@@ -851,7 +851,7 @@ void slirp_input(Slirp *slirp, const uint8_t *pkt, int pkt_len)
     if (pkt_len < ETH_HLEN)
         return;
 
-    proto = ntohs(*(uint16_t *)(pkt + 12));
+    proto = (((uint16_t) pkt[12]) << 8) + pkt[13];
     switch(proto) {
     case ETH_P_ARP:
         arp_input(slirp, pkt, pkt_len);