[PATCH bpf-next v4 4/4] selftests/bpf: Add test case for freplace attachment failure log

[Leon Hwang <leon.hwang@linux.dev>]

This patch adds a selftest to verify that freplace attachment failure
produces meaningful log.

cd tools/testing/selftests/bpf/; ./test_progs -t attach_log
115     freplace_attach_log:OK
Summary: 1/0 PASSED, 0 SKIPPED, 0 FAILED

Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
---
 .../bpf/prog_tests/tracing_link_attach_log.c  | 48 +++++++++++++++++++
 1 file changed, 48 insertions(+)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/tracing_link_attach_log.c

diff --git a/tools/testing/selftests/bpf/prog_tests/tracing_link_attach_log.c b/tools/testing/selftests/bpf/prog_tests/tracing_link_attach_log.c
new file mode 100644
index 0000000000000..92f770966f8cd
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/tracing_link_attach_log.c
@@ -0,0 +1,48 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <test_progs.h>
+#include "tailcall_bpf2bpf1.skel.h"
+#include "freplace_global_func.skel.h"
+
+void test_freplace_attach_log(void)
+{
+	struct freplace_global_func *freplace_skel = NULL;
+	struct tailcall_bpf2bpf1 *tailcall_skel = NULL;
+	struct bpf_link *freplace_link = NULL;
+	struct bpf_program *prog;
+	char log_buf[64];
+	int err, prog_fd;
+	LIBBPF_OPTS(bpf_freplace_opts, freplace_opts,
+		    .log_buf = log_buf,
+		    .log_buf_size = sizeof(log_buf),
+	);
+
+	tailcall_skel = tailcall_bpf2bpf1__open_and_load();
+	if (!ASSERT_OK_PTR(tailcall_skel, "tailcall_bpf2bpf1__open_and_load"))
+		return;
+
+	freplace_skel = freplace_global_func__open();
+	if (!ASSERT_OK_PTR(freplace_skel, "freplace_global_func__open"))
+		goto out;
+
+	prog = freplace_skel->progs.new_test_pkt_access;
+	prog_fd = bpf_program__fd(tailcall_skel->progs.entry);
+	err = bpf_program__set_attach_target(prog, prog_fd, "entry");
+	if (!ASSERT_OK(err, "bpf_program__set_attach_target"))
+		goto out;
+
+	err = freplace_global_func__load(freplace_skel);
+	if (!ASSERT_OK(err, "freplace_global_func__load"))
+		goto out;
+
+	freplace_opts.prog = prog;
+	freplace_opts.target_prog_fd = prog_fd;
+	freplace_opts.attach_func_name = "subprog_tail";
+	freplace_link = bpf_program__attach_freplace_opts(&freplace_opts);
+	ASSERT_ERR_PTR(freplace_link, "bpf_program__attach_freplace");
+	ASSERT_STREQ(log_buf, "subprog_tail() is not a global function\n", "log_buf");
+
+out:
+	bpf_link__destroy(freplace_link);
+	freplace_global_func__destroy(freplace_skel);
+	tailcall_bpf2bpf1__destroy(tailcall_skel);
+}
-- 
2.47.1