[PATCH bpf-next 6/9] selftests/bpf: Verify tracing link_create logs

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

Check the error code, log message, and reported log size for invalid
tracing and freplace link creation parameters. Cover reattachment and
attach-target checks, including incompatible kprobe_write_ctx settings.

Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
---
 .../selftests/bpf/prog_tests/tracing_link.c   | 275 ++++++++++++++++++
 1 file changed, 275 insertions(+)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/tracing_link.c

diff --git a/tools/testing/selftests/bpf/prog_tests/tracing_link.c b/tools/testing/selftests/bpf/prog_tests/tracing_link.c
new file mode 100644
index 000000000000..1b64cb3e9983
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/tracing_link.c
@@ -0,0 +1,275 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <test_progs.h>
+#include <bpf/btf.h>
+#include "fentry_recursive.skel.h"
+#include "priv_freplace_prog.skel.h"
+#include "xdp_dummy.skel.h"
+#include "kprobe_write_ctx.skel.h"
+
+static void test_fentry_link_create_log(int target_fd, __u32 target_btf_id, int cookie,
+					enum bpf_attach_type attach_type,
+					bool reattach, const char *msg)
+{
+	struct fentry_recursive *skel = NULL;
+	struct xdp_dummy *target;
+	char log_buf[128] = {};
+	int err, fd, prog_fd;
+	LIBBPF_OPTS(bpf_log_opts, log_opts,
+		    .buf = log_buf,
+		    .size = sizeof(log_buf),
+		    .level = 1,
+	);
+	LIBBPF_OPTS(bpf_link_create_opts, opts,
+		    .log_opts = &log_opts,
+		    .target_btf_id = target_btf_id,
+		    .tracing.cookie = cookie,
+	);
+
+	target = xdp_dummy__open_and_load();
+	if (!ASSERT_OK_PTR(target, "xdp_dummy__open_and_load"))
+		return;
+
+	skel = fentry_recursive__open();
+	if (!ASSERT_OK_PTR(skel, "fentry_recursive__open"))
+		goto out;
+
+	err = bpf_program__set_attach_target(skel->progs.recursive_attach,
+					     bpf_program__fd(target->progs.xdp_dummy_prog),
+					     "xdp_dummy_prog");
+	if (!ASSERT_OK(err, "bpf_program__set_attach_target"))
+		goto out;
+
+	err = fentry_recursive__load(skel);
+	if (!ASSERT_OK(err, "fentry_recursive__load"))
+		goto out;
+
+	prog_fd = bpf_program__fd(skel->progs.recursive_attach);
+	if (reattach) {
+		/* Consume the initial target saved when the program was loaded. */
+		fd = bpf_link_create(prog_fd, 0, BPF_TRACE_FENTRY, &opts);
+		if (!ASSERT_GE(fd, 0, "bpf_link_create first"))
+			goto out;
+
+		close(fd);
+		memset(log_buf, 0, sizeof(log_buf));
+		log_opts.true_size = 0;
+	}
+
+	fd = bpf_link_create(prog_fd, target_fd, attach_type, &opts);
+	if (!ASSERT_LT(fd, 0, "bpf_link_create")) {
+		close(fd);
+		goto out;
+	}
+
+	ASSERT_EQ(fd, -EINVAL, "err");
+	ASSERT_STREQ(log_buf, msg, "log_buf");
+	ASSERT_EQ(log_opts.true_size, strlen(msg) + 1, "log_size");
+
+out:
+	fentry_recursive__destroy(skel);
+	xdp_dummy__destroy(target);
+}
+
+static void test_log_invalid_attach_type(void)
+{
+	const char *msg = "Invalid attach_type.\n";
+
+	test_fentry_link_create_log(0, 0, 0, BPF_XDP, false, msg);
+}
+
+static void test_log_tgt_prog_fd_only(void)
+{
+	const char *msg = "tgt_prog_fd and btf_id must be both set or both unset.\n";
+
+	test_fentry_link_create_log(-1, 0, 1, BPF_TRACE_FENTRY, false, msg);
+}
+
+static void test_log_tgt_prog_fd_disallowed(void)
+{
+	const char *msg = "tgt_prog_fd is only allowed for freplace prog.\n";
+
+	test_fentry_link_create_log(-1, 1, 0, BPF_TRACE_FENTRY, false, msg);
+}
+
+static void test_log_invalid_attach_btf(void)
+{
+	const char *msg = "Invalid attach_btf.\n";
+
+	test_fentry_link_create_log(0, 0, 1, BPF_TRACE_FENTRY, true, msg);
+}
+
+static void test_freplace_link_create_log(int target_fd, __u32 target_btf_id, int err_exp,
+					  bool reattach, const char *msg)
+{
+	struct priv_freplace_prog *skel = NULL;
+	char log_buf[256] = {};
+	struct xdp_dummy *xdp;
+	int err, fd, prog_fd;
+	LIBBPF_OPTS(bpf_log_opts, log_opts,
+		    .buf = log_buf,
+		    .size = sizeof(log_buf),
+		    .level = 1,
+	);
+	LIBBPF_OPTS(bpf_link_create_opts, opts,
+		    .log_opts = &log_opts,
+		    .target_btf_id = target_btf_id,
+	);
+
+	xdp = xdp_dummy__open_and_load();
+	if (!ASSERT_OK_PTR(xdp, "xdp_dummy__open_and_load"))
+		return;
+
+	skel = priv_freplace_prog__open();
+	if (!ASSERT_OK_PTR(skel, "priv_freplace_prog__open"))
+		goto out;
+
+	err = bpf_program__set_attach_target(skel->progs.new_xdp_prog2,
+					     bpf_program__fd(xdp->progs.xdp_dummy_prog),
+					     "xdp_dummy_prog");
+	if (!ASSERT_OK(err, "bpf_program__set_attach_target"))
+		goto out;
+
+	err = priv_freplace_prog__load(skel);
+	if (!ASSERT_OK(err, "priv_freplace_prog__load"))
+		goto out;
+
+	prog_fd = bpf_program__fd(skel->progs.new_xdp_prog2);
+	if (reattach) {
+		/* Consume the initial target saved when the program was loaded. */
+		fd = bpf_link_create(prog_fd, 0, 0, &opts);
+		if (!ASSERT_GE(fd, 0, "bpf_link_create first"))
+			goto out;
+
+		close(fd);
+		memset(log_buf, 0, sizeof(log_buf));
+		log_opts.true_size = 0;
+	}
+
+	if (!target_fd && target_btf_id)
+		target_fd = bpf_program__fd(xdp->progs.xdp_dummy_prog);
+
+	fd = bpf_link_create(prog_fd, target_fd, 0, &opts);
+	if (!ASSERT_LT(fd, 0, "bpf_link_create")) {
+		close(fd);
+		goto out;
+	}
+
+	ASSERT_EQ(fd, err_exp, "err");
+	ASSERT_STREQ(log_buf, msg, "log_buf");
+	ASSERT_EQ(log_opts.true_size, strlen(msg) + 1, "log_size");
+
+out:
+	priv_freplace_prog__destroy(skel);
+	xdp_dummy__destroy(xdp);
+}
+
+static void test_log_invalid_target_fd(void)
+{
+	const char *msg = "Invalid tgt_prog_fd.\n";
+
+	test_freplace_link_create_log(-1, 1, -EBADF, false, msg);
+}
+
+static void test_log_reattach_without_target(void)
+{
+	const char *msg = "Only allow re-attach for tracing and lsm progs.\n";
+
+	test_freplace_link_create_log(0, 0, -EINVAL, true, msg);
+}
+
+static void test_log_invalid_target_btf_id(void)
+{
+	const char *msg = "attach_btf_id 4294967295 is invalid\n";
+
+	test_freplace_link_create_log(0, ~0U, -EINVAL, false, msg);
+}
+
+#ifdef __x86_64__
+static void test_log_invalid_kprobe_write_ctx(void)
+{
+	struct kprobe_write_ctx *skel_kprobe, *skel_freplace = NULL;
+	struct bpf_program *prog_kprobe, *prog_freplace;
+	const char *msg = "Invalid kprobe_write_ctx.\n";
+	int err, prog_fd, btf_id, fd;
+	char log_buf[128] = {};
+	LIBBPF_OPTS(bpf_log_opts, log_opts,
+		    .buf = log_buf,
+		    .size = sizeof(log_buf),
+		    .level = 1,
+	);
+	LIBBPF_OPTS(bpf_link_create_opts, link_opts,
+		    .log_opts = &log_opts,
+	);
+
+	skel_kprobe = kprobe_write_ctx__open();
+	if (!ASSERT_OK_PTR(skel_kprobe, "kprobe_write_ctx__open kprobe"))
+		return;
+
+	prog_kprobe = skel_kprobe->progs.kprobe_dummy;
+	bpf_program__set_autoload(prog_kprobe, true);
+
+	err = kprobe_write_ctx__load(skel_kprobe);
+	if (!ASSERT_OK(err, "kprobe_write_ctx__load kprobe"))
+		goto out;
+
+	skel_freplace = kprobe_write_ctx__open();
+	if (!ASSERT_OK_PTR(skel_freplace, "kprobe_write_ctx__open freplace"))
+		goto out;
+
+	prog_freplace = skel_freplace->progs.freplace_kprobe;
+	bpf_program__set_autoload(prog_freplace, true);
+
+	prog_fd = bpf_program__fd(skel_kprobe->progs.kprobe_write_ctx);
+	bpf_program__set_attach_target(prog_freplace, prog_fd, "kprobe_write_ctx");
+
+	err = kprobe_write_ctx__load(skel_freplace);
+	if (!ASSERT_OK(err, "kprobe_write_ctx__load freplace"))
+		goto out;
+
+	prog_fd = bpf_program__fd(prog_kprobe);
+	btf_id = btf__find_by_name_kind(bpf_object__btf(skel_kprobe->obj), "kprobe_dummy",
+					BTF_KIND_FUNC);
+	if (!ASSERT_GT(btf_id, 0, "btf__find_by_name_kind"))
+		goto out;
+
+	link_opts.target_btf_id = btf_id;
+	fd = bpf_link_create(bpf_program__fd(prog_freplace), prog_fd, 0, &link_opts);
+	if (!ASSERT_LT(fd, 0, "bpf_link_create")) {
+		close(fd);
+		goto out;
+	}
+
+	ASSERT_EQ(fd, -EINVAL, "err");
+	ASSERT_STREQ(log_buf, msg, "log_buf");
+	ASSERT_EQ(log_opts.true_size, strlen(msg) + 1, "log_size");
+
+out:
+	kprobe_write_ctx__destroy(skel_freplace);
+	kprobe_write_ctx__destroy(skel_kprobe);
+}
+#else
+static void test_log_invalid_kprobe_write_ctx(void)
+{
+	test__skip();
+}
+#endif
+
+void test_tracing_link_log(void)
+{
+	if (test__start_subtest("invalid_attach_type"))
+		test_log_invalid_attach_type();
+	if (test__start_subtest("tgt_prog_fd_only"))
+		test_log_tgt_prog_fd_only();
+	if (test__start_subtest("tgt_prog_fd_disallowed"))
+		test_log_tgt_prog_fd_disallowed();
+	if (test__start_subtest("invalid_attach_btf"))
+		test_log_invalid_attach_btf();
+	if (test__start_subtest("invalid_target_fd"))
+		test_log_invalid_target_fd();
+	if (test__start_subtest("reattach_without_target"))
+		test_log_reattach_without_target();
+	if (test__start_subtest("invalid_target_btf_id"))
+		test_log_invalid_target_btf_id();
+	if (test__start_subtest("invalid_kprobe_write_ctx"))
+		test_log_invalid_kprobe_write_ctx();
+}
-- 
2.55.0