selftests/bpf: freplace tests for tracking of changes_packet_data

Try different combinations of global functions replacement:
- replace function that changes packet data with one that doesn't;
- replace function that changes packet data with one that does;
- replace function that doesn't change packet data with one that does;
- replace function that doesn't change packet data with one that doesn't;

Signed-off-by: Eduard Zingerman <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Alexei Starovoitov <[email protected]>

1 files changed, 26 insertions, 0 deletions

diff --git a/tools/testing/selftests/bpf/progs/changes_pkt_data.c b/tools/testing/selftests/bpf/progs/changes_pkt_data.c
new file mode 100644
index 000000000000..f87da8e9d6b3
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/changes_pkt_data.c
@@ -0,0 +1,26 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+
+__noinline
+long changes_pkt_data(struct __sk_buff *sk, __u32 len)
+{
+	return bpf_skb_pull_data(sk, len);
+}
+
+__noinline __weak
+long does_not_change_pkt_data(struct __sk_buff *sk, __u32 len)
+{
+	return 0;
+}
+
+SEC("tc")
+int dummy(struct __sk_buff *sk)
+{
+	changes_pkt_data(sk, 0);
+	does_not_change_pkt_data(sk, 0);
+	return 0;
+}
+
+char _license[] SEC("license") = "GPL";