selftests/bpf: Add test for libbpf's custom log_buf behavior

Add a selftest that validates that per-program and per-object log_buf
overrides work as expected. Also test same logic for low-level
bpf_prog_load() and bpf_btf_load() APIs.

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20211209193840.1248570-11-andrii@kernel.org

1 files changed, 24 insertions, 0 deletions

diff --git a/tools/testing/selftests/bpf/progs/test_log_buf.c b/tools/testing/selftests/bpf/progs/test_log_buf.c
new file mode 100644
index 000000000000..199f459bd5ae
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/test_log_buf.c
@@ -0,0 +1,24 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2021 Facebook */
+
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+
+int a[4];
+const volatile int off = 4000;
+
+SEC("raw_tp/sys_enter")
+int good_prog(const void *ctx)
+{
+	a[0] = (int)(long)ctx;
+	return a[1];
+}
+
+SEC("raw_tp/sys_enter")
+int bad_prog(const void *ctx)
+{
+	/* out of bounds access */
+	return a[off];
+}
+
+char _license[] SEC("license") = "GPL";