selftests/bpf: Add ref_ctr_offset selftests

Extend attach_probe selftests to specify ref_ctr_offset for uprobe/uretprobe
and validate that its value is incremented from zero.

Turns out that once uprobe is attached with ref_ctr_offset, uretprobe for the
same location/function *has* to use ref_ctr_offset as well, otherwise
perf_event_open() fails with -EINVAL. So this test uses ref_ctr_offset for
both uprobe and uretprobe, even though for the purpose of test uprobe would be
enough.

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20210815070609.987780-17-andrii@kernel.org

1 files changed, 21 insertions, 0 deletions

diff --git a/tools/testing/selftests/bpf/trace_helpers.c b/tools/testing/selftests/bpf/trace_helpers.c
index 381dafce1d8f..e7a19b04d4ea 100644
--- a/tools/testing/selftests/bpf/trace_helpers.c
+++ b/tools/testing/selftests/bpf/trace_helpers.c
@@ -202,3 +202,24 @@ ssize_t get_base_addr(void)
 	fclose(f);
 	return -EINVAL;
 }
+
+ssize_t get_rel_offset(uintptr_t addr)
+{
+	size_t start, end, offset;
+	char buf[256];
+	FILE *f;
+
+	f = fopen("/proc/self/maps", "r");
+	if (!f)
+		return -errno;
+
+	while (fscanf(f, "%zx-%zx %s %zx %*[^\n]\n", &start, &end, buf, &offset) == 4) {
+		if (addr >= start && addr < end) {
+			fclose(f);
+			return (size_t)addr - start + offset;
+		}
+	}
+
+	fclose(f);
+	return -EINVAL;
+}