Verify the fact that only one fentry prog could be attached to another
fentry, building up an attachment chain of limited size. Use existing
bpf_testmod as a start of the chain.
Acked-by: Jiri Olsa <olsajiri@xxxxxxxxx>
Signed-off-by: Dmitrii Dolgov <9erthalion6@xxxxxxxxx>
---
Changes in v11:
- Use subtests, reduce code duplication
Changes in v10:
- Add tests for loading tracing progs without attaching, and
detaching tracing progs.
Changes in v8:
- Cleanup test bpf progs and the content of first/second condition
in the loop.
Changes in v5:
- Test only one level of attachment
.../bpf/prog_tests/recursive_attach.c | 111 ++++++++++++++++++
.../selftests/bpf/progs/fentry_recursive.c | 16 +++
.../bpf/progs/fentry_recursive_target.c | 17 +++
3 files changed, 144 insertions(+)
create mode 100644 tools/testing/selftests/bpf/prog_tests/recursive_attach.c
create mode 100644 tools/testing/selftests/bpf/progs/fentry_recursive.c
create mode 100644 tools/testing/selftests/bpf/progs/fentry_recursive_target.c
diff --git a/tools/testing/selftests/bpf/prog_tests/recursive_attach.c b/tools/testing/selftests/bpf/prog_tests/recursive_attach.c
new file mode 100644
index 000000000000..e9e576de6723
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/recursive_attach.c
@@ -0,0 +1,111 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2023 Red Hat, Inc. */
+#include <test_progs.h>
+#include "fentry_recursive.skel.h"
+#include "fentry_recursive_target.skel.h"
+#include <bpf/btf.h>
+#include "bpf/libbpf_internal.h"
+
+/*
+ * Test recursive attachment of tracing progs with more than one nesting level
+ * is not possible. Create a chain of attachment, verify that the last prog
+ * will fail. Depending on the arguments, following cases are tested:
+ *
+ * - Recursive loading of tracing progs, without attaching (attach = false,
+ * detach = false). The chain looks like this:
+ * load target
+ * load fentry1 -> target
+ * load fentry2 -> fentry1 (fail)
+ *
+ * - Recursive attach of tracing progs (attach = true, detach = false). The
+ * chain looks like this:
+ * load target
+ * load fentry1 -> target
+ * attach fentry1 -> target
+ * load fentry2 -> fentry1 (fail)
+ *
+ * - Recursive attach and detach of tracing progs (attach = true, detach =
+ * true). This validates that attach_tracing_prog flag will be set throughout
+ * the whole lifecycle of an fentry prog, independently from whether it's
+ * detached. The chain looks like this:
+ * load target
+ * load fentry1 -> target
+ * attach fentry1 -> target
+ * detach fentry1
+ * load fentry2 -> fentry1 (fail)
+ */
+static void test_recursive_fentry_chain(bool attach, bool detach)
+{
+ struct fentry_recursive_target *target_skel = NULL;
+ struct fentry_recursive *tracing_chain[2] = {};
+ struct bpf_program *prog;
+ int prev_fd, err;
+
+ target_skel = fentry_recursive_target__open_and_load();
+ if (!ASSERT_OK_PTR(target_skel, "fentry_recursive_target__open_and_load"))
+ goto close_prog;
+
+ /* Create an attachment chain with two fentry progs */
+ for (int i = 0; i < 2; i++) {
+ tracing_chain[i] = fentry_recursive__open();
+ if (!ASSERT_OK_PTR(tracing_chain[i], "fentry_recursive__open"))
+ goto close_prog;
+
+ /*
+ * The first prog in the chain is going to be attached to the target
+ * fentry program, the second one to the previous in the chain.
+ */
+ prog = tracing_chain[i]->progs.recursive_attach;
+ if (i == 0) {
+ prev_fd = bpf_program__fd(target_skel->progs.test1);
+ err = bpf_program__set_attach_target(prog, prev_fd, "test1");
+ } else {
+ prev_fd = bpf_program__fd(tracing_chain[i-1]->progs.recursive_attach);
+ err = bpf_program__set_attach_target(prog, prev_fd, "recursive_attach");
+ }
+
+ if (!ASSERT_OK(err, "bpf_program__set_attach_target"))
+ goto close_prog;
+
+ err = fentry_recursive__load(tracing_chain[i]);
+ /* The first attach should succeed, the second fail */
+ if (i == 0) {
+ if (!ASSERT_OK(err, "fentry_recursive__load"))
+ goto close_prog;
+
+ if (attach) {
+ err = fentry_recursive__attach(tracing_chain[i]);
+ if (!ASSERT_OK(err, "fentry_recursive__attach"))
+ goto close_prog;
+ }
+
+ if (detach) {
+ /*
+ * Flag attach_tracing_prog should still be set, preventing
+ * attachment of the following prog.
+ */
+ fentry_recursive__detach(tracing_chain[i]);
+ }
+ } else {
+ if (!ASSERT_ERR(err, "fentry_recursive__load"))
+ goto close_prog;
+ }
+ }
+
+close_prog:
+ fentry_recursive_target__destroy(target_skel);
+ for (int i = 0; i < 2; i++) {
+ if (tracing_chain[i])
+ fentry_recursive__destroy(tracing_chain[i]);
+ }
+}
+
+void test_recursive_fentry(void)
+{
+ if (test__start_subtest("attach"))
+ test_recursive_fentry_chain(true, false);
+ if (test__start_subtest("load"))
+ test_recursive_fentry_chain(false, false);
+ if (test__start_subtest("detach"))
+ test_recursive_fentry_chain(true, true);
+}
diff --git a/tools/testing/selftests/bpf/progs/fentry_recursive.c b/tools/testing/selftests/bpf/progs/fentry_recursive.c
new file mode 100644
index 000000000000..b9e4d35ac597
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/fentry_recursive.c
@@ -0,0 +1,16 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2023 Red Hat, Inc. */
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+
+char _license[] SEC("license") = "GPL";
+
+/*
+ * Dummy fentry bpf prog for testing fentry attachment chains
+ */
+SEC("fentry/XXX")
+int BPF_PROG(recursive_attach, int a)
+{
+ return 0;
+}
diff --git a/tools/testing/selftests/bpf/progs/fentry_recursive_target.c b/tools/testing/selftests/bpf/progs/fentry_recursive_target.c
new file mode 100644
index 000000000000..6e0b5c716f8e
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/fentry_recursive_target.c
@@ -0,0 +1,17 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2023 Red Hat, Inc. */
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+
+char _license[] SEC("license") = "GPL";
+
+/*
+ * Dummy fentry bpf prog for testing fentry attachment chains. It's going to be
+ * a start of the chain.
+ */
+SEC("fentry/bpf_testmod_fentry_test1")
+int BPF_PROG(test1, int a)
+{
+ return 0;
+}
--
2.41.0
