Add a higher-level test (C BPF program) for the new functionality -
variable access stack reads and writes.
Signed-off-by: Andrei Matei <andreimatei1@xxxxxxxxx>
---
.../selftests/bpf/prog_tests/stack_var_off.c | 36 ++++++++++++
.../selftests/bpf/progs/test_stack_var_off.c | 56 +++++++++++++++++++
2 files changed, 92 insertions(+)
create mode 100644 tools/testing/selftests/bpf/prog_tests/stack_var_off.c
create mode 100644 tools/testing/selftests/bpf/progs/test_stack_var_off.c
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..52e00486b1aa
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/stack_var_off.c
@@ -0,0 +1,36 @@
+// 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;
+ if (CHECK(!skel->bss, "check_bss", ".bss wasn't mmap()-ed\n"))
+ goto cleanup;
+
+ test_stack_var_off__attach(skel);
+
+ /* 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. */
+
+ /* 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);
+}
diff --git a/tools/testing/selftests/bpf/progs/test_stack_var_off.c b/tools/testing/selftests/bpf/progs/test_stack_var_off.c
new file mode 100644
index 000000000000..bd9c8d86cd91
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/test_stack_var_off.c
@@ -0,0 +1,56 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (c) 2017 Facebook
+
+#include <linux/ptrace.h>
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+
+int probe_res;
+
+char input[4] = {};
+int test_pid;
+
+SEC("tracepoint/syscalls/sys_enter_nanosleep")
+int probe(void *ctx)
+{
+ /* This BPF program performs variable-offset reads and writes on a
+ * stack-allocated buffer.
+ */
+ char stack_buf[16];
+ unsigned long len;
+ unsigned long last;
+
+ if (test_pid == 0)
+ return 0;
+ if ((bpf_get_current_pid_tgid() >> 32) != test_pid)
+ return 0;
+
+ /* Copy the input to the stack. */
+ __builtin_memcpy(stack_buf, input, 4);
+
+ /* The first byte in the buffer indicates the length. */
+ len = stack_buf[0] & 0xf;
+ last = (len - 1) & 0xf;
+
+ /* Append something to the buffer. The offset where we write is not
+ * statically known; this is a variable-offset stack write.
+ */
+ stack_buf[len] = 42;
+
+ /* Index into the buffer at an unknown offset. This is a
+ * variable-offset stack read.
+ *
+ * Note that if it wasn't for the preceding variable-offset write, this
+ * read would be rejected because the stack slot cannot be verified as
+ * being initialized. With the preceding variable-offset write, the
+ * stack slot still cannot be verified, but the write inhibits the
+ * respective check on the reasoning that, if there was a
+ * variable-offset to a higher-or-equal spot, we're probably reading
+ * what we just wrote.
+ */
+ probe_res = stack_buf[last];
+ return 0;
+}
+
+char _license[] SEC("license") = "GPL";
--
2.27.0
