[PATCH RFC 4/4] selftests/bpf: Add test for ftrace-based BPF attach/detach

["Joel Fernandes (Google)" <joel@joelfernandes.org>]

Here we add support for testing the attach and detach of a BPF program
to a tracepoint through tracefs.

Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
---
 .../raw_tp_writable_test_ftrace_run.c         | 89 +++++++++++++++++++
 1 file changed, 89 insertions(+)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/raw_tp_writable_test_ftrace_run.c

diff --git a/tools/testing/selftests/bpf/prog_tests/raw_tp_writable_test_ftrace_run.c b/tools/testing/selftests/bpf/prog_tests/raw_tp_writable_test_ftrace_run.c
new file mode 100644
index 000000000000..7b42e3a69b71
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/raw_tp_writable_test_ftrace_run.c
@@ -0,0 +1,89 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <test_progs.h>
+#include <linux/nbd.h>
+
+void test_raw_tp_writable_test_ftrace_run(void)
+{
+	__u32 duration = 0;
+	char error[4096];
+	int ret;
+
+	const struct bpf_insn trace_program[] = {
+		BPF_LDX_MEM(BPF_DW, BPF_REG_6, BPF_REG_1, 0),
+		BPF_LDX_MEM(BPF_W, BPF_REG_0, BPF_REG_6, 0),
+		BPF_MOV64_IMM(BPF_REG_0, 42),
+		BPF_STX_MEM(BPF_W, BPF_REG_6, BPF_REG_0, 0),
+		BPF_EXIT_INSN(),
+	};
+
+	struct bpf_load_program_attr load_attr = {
+		.prog_type = BPF_PROG_TYPE_RAW_TRACEPOINT_WRITABLE,
+		.license = "GPL v2",
+		.insns = trace_program,
+		.insns_cnt = sizeof(trace_program) / sizeof(struct bpf_insn),
+		.log_level = 2,
+	};
+
+	int bpf_fd = bpf_load_program_xattr(&load_attr, error, sizeof(error));
+
+	if (CHECK(bpf_fd < 0, "bpf_raw_tracepoint_writable loaded",
+		  "failed: %d errno %d\n", bpf_fd, errno))
+		return;
+
+	const struct bpf_insn skb_program[] = {
+		BPF_MOV64_IMM(BPF_REG_0, 0),
+		BPF_EXIT_INSN(),
+	};
+
+	struct bpf_load_program_attr skb_load_attr = {
+		.prog_type = BPF_PROG_TYPE_SOCKET_FILTER,
+		.license = "GPL v2",
+		.insns = skb_program,
+		.insns_cnt = sizeof(skb_program) / sizeof(struct bpf_insn),
+	};
+
+	int filter_fd =
+		bpf_load_program_xattr(&skb_load_attr, error, sizeof(error));
+	if (CHECK(filter_fd < 0, "test_program_loaded", "failed: %d errno %d\n",
+		  filter_fd, errno))
+		goto out_bpffd;
+
+	ret = bpf_raw_tracepoint_ftrace_attach("bpf_test_run",
+					       "bpf_test_finish",
+					       bpf_fd);
+	if (CHECK(ret < 0, "bpf_raw_tracepoint_ftrace_attach",
+		  "failed: %d errno %d\n", ret, errno))
+		goto out_filterfd;
+
+	char test_skb[128] = {
+		0,
+	};
+
+	__u32 prog_ret;
+	int err = bpf_prog_test_run(filter_fd, 1, test_skb, sizeof(test_skb), 0,
+				    0, &prog_ret, 0);
+	CHECK(err != 42, "test_run",
+	      "tracepoint did not modify return value\n");
+	CHECK(prog_ret != 0, "test_run_ret",
+	      "socket_filter did not return 0\n");
+
+	ret = bpf_raw_tracepoint_ftrace_detach("bpf_test_run",
+					       "bpf_test_finish",
+					       bpf_fd);
+	if (CHECK(ret < 0, "bpf_raw_tracepoint_ftrace_detach",
+		  "failed: %d errno %d\n", ret, errno))
+		goto out_filterfd;
+
+	err = bpf_prog_test_run(filter_fd, 1, test_skb, sizeof(test_skb), 0, 0,
+				&prog_ret, 0);
+	CHECK(err != 0, "test_run_notrace",
+	      "test_run failed with %d errno %d\n", err, errno);
+	CHECK(prog_ret != 0, "test_run_ret_notrace",
+	      "socket_filter did not return 0\n");
+
+out_filterfd:
+	close(filter_fd);
+out_bpffd:
+	close(bpf_fd);
+}
-- 
2.22.0.410.gd8fdbe21b5-goog