selftest/bpf: Add test for var-offset stack access

Add a higher-level test (C BPF program) for the new functionality -
variable access stack reads and writes.

Signed-off-by: Andrei Matei <andreimatei1@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20210207011027.676572-5-andreimatei1@gmail.com

1 files changed, 35 insertions, 0 deletions

diff --git a/tools/testing/selftests/bpf/prog_tests/stack_var_off.c b/tools/testing/selftests/bpf/prog_tests/stack_var_off.c
new file mode 100644
index 000000000000..2ce9deefa59c
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/stack_var_off.c
@@ -0,0 +1,35 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <test_progs.h>
+#include "test_stack_var_off.skel.h"
+
+/* Test read and writes to the stack performed with offsets that are not
+ * statically known.
+ */
+void test_stack_var_off(void)
+{
+	int duration = 0;
+	struct test_stack_var_off *skel;
+
+	skel = test_stack_var_off__open_and_load();
+	if (CHECK(!skel, "skel_open", "failed to open skeleton\n"))
+		return;
+
+	/* Give pid to bpf prog so it doesn't trigger for anyone else. */
+	skel->bss->test_pid = getpid();
+	/* Initialize the probe's input. */
+	skel->bss->input[0] = 2;
+	skel->bss->input[1] = 42;  /* This will be returned in probe_res. */
+
+	if (!ASSERT_OK(test_stack_var_off__attach(skel), "skel_attach"))
+		goto cleanup;
+
+	/* Trigger probe. */
+	usleep(1);
+
+	if (CHECK(skel->bss->probe_res != 42, "check_probe_res",
+		  "wrong probe res: %d\n", skel->bss->probe_res))
+		goto cleanup;
+
+cleanup:
+	test_stack_var_off__destroy(skel);
+}