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 | 56 +++++++++++++++++++
.../selftests/bpf/progs/test_stack_var_off.c | 43 ++++++++++++++
2 files changed, 99 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..c4c47fb0f0af
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/stack_var_off.c
@@ -0,0 +1,56 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <test_progs.h>
+#include "test_stack_var_off.skel.h"
+
+int dummy;
+
+noinline void uprobed_function(char *s, int len)
+{
+ /* Do something to keep the compiler from removing the function.
+ */
+ dummy++;
+}
+
+void test_stack_var_off(void)
+{
+ int duration = 0;
+ struct bpf_link *uprobe_link;
+ struct test_stack_var_off *skel;
+ size_t uprobe_offset;
+ ssize_t base_addr;
+ char s[100];
+
+ base_addr = get_base_addr();
+ if (CHECK(base_addr < 0, "get_base_addr",
+ "failed to find base addr: %zd", base_addr))
+ return;
+ uprobe_offset = (size_t)&uprobed_function - base_addr;
+
+ 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;
+
+ uprobe_link = bpf_program__attach_uprobe(skel->progs.uprobe,
+ false /* retprobe */,
+ 0 /* self pid */,
+ "/proc/self/exe",
+ uprobe_offset);
+ if (CHECK(IS_ERR(uprobe_link), "attach_uprobe",
+ "err %ld\n", PTR_ERR(uprobe_link)))
+ goto cleanup;
+ skel->links.uprobe = uprobe_link;
+
+ /* trigger uprobe */
+ s[0] = 1;
+ s[1] = 10;
+ uprobed_function(&s[0], 2);
+
+ if (CHECK(skel->bss->uprobe_res != 10, "check_uprobe_res",
+ "wrong uprobe res: %d\n", skel->bss->uprobe_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..44f982684541
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/test_stack_var_off.c
@@ -0,0 +1,43 @@
+// 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 uprobe_res;
+
+SEC("uprobe/func")
+int BPF_KPROBE(uprobe, char *s, int len)
+{
+ /* This BPF program performs variable-offset reads and writes on a
+ * stack-allocated buffer.
+ */
+ char buf[16];
+ unsigned long idx;
+ char out;
+
+ /* Zero-out the buffer so we can read anywhere inside it. */
+ __builtin_memset(&buf, 0, 16);
+ /* Copy the contents of s from user-space. */
+ len &= 0xf;
+ if (bpf_probe_read_user(&buf, len, s)) {
+ bpf_printk("error reading user mem\n");
+ return 1;
+ }
+ /* Index into the buffer at an unknown offset that comes from the
+ * buffer itself. This is a variable-offset stack read.
+ */
+ idx = buf[0];
+ idx &= 0xf;
+ out = buf[idx];
+ /* Append something to the buffer. The position where we append it
+ * is unknown. This is a variable-offset stack write.
+ */
+ buf[len] = buf[idx];
+ uprobe_res = out;
+ return 0;
+}
+
+char _license[] SEC("license") = "GPL";
--
2.27.0
