From: Jakub Sitnicki <jakub@cloudflare.com>
Date: Sat, 19 Mar 2022 19:33:56 +0100
Subject: selftests/bpf: Fix test for 4-byte load from remote_port on
big-endian
Patch-mainline: v5.18-rc1
Git-commit: ce5236800116d18ac2c06c58f73930406e3ea4be
References: jsc#PED-1377
The context access converter rewrites the 4-byte load from
bpf_sk_lookup->remote_port to a 2-byte load from bpf_sk_lookup_kern
structure.
It means that we cannot treat the destination register contents as a 32-bit
value, or the code will not be portable across big- and little-endian
architectures.
This is exactly the same case as with 4-byte loads from bpf_sock->dst_port
so follow the approach outlined in [1] and treat the register contents as a
16-bit value in the test.
[1]: https://lore.kernel.org/bpf/20220317113920.1068535-5-jakub@cloudflare.com/
Fixes: 2ed0dc5937d3 ("selftests/bpf: Cover 4-byte load from remote_port in bpf_sk_lookup")
Signed-off-by: Jakub Sitnicki <jakub@cloudflare.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/bpf/20220319183356.233666-4-jakub@cloudflare.com
Acked-by: Shung-Hsi Yu <shung-hsi.yu@suse.com>
---
tools/testing/selftests/bpf/progs/test_sk_lookup.c | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)
--- a/tools/testing/selftests/bpf/progs/test_sk_lookup.c
+++ b/tools/testing/selftests/bpf/progs/test_sk_lookup.c
@@ -418,9 +418,15 @@ int ctx_narrow_access(struct bpf_sk_look
if (LSW(ctx->remote_port, 0) != SRC_PORT)
return SK_DROP;
- /* Load from remote_port field with zero padding (backward compatibility) */
+ /*
+ * NOTE: 4-byte load from bpf_sk_lookup at remote_port offset
+ * is quirky. It gets rewritten by the access converter to a
+ * 2-byte load for backward compatibility. Treating the load
+ * result as a be16 value makes the code portable across
+ * little- and big-endian platforms.
+ */
val_u32 = *(__u32 *)&ctx->remote_port;
- if (val_u32 != bpf_htonl(bpf_ntohs(SRC_PORT) << 16))
+ if (val_u32 != SRC_PORT)
return SK_DROP;
/* Narrow loads from local_port field. Expect DST_PORT. */