@@ -14,6 +14,20 @@ void test_attach_probe(void)
struct test_attach_probe* skel;
size_t uprobe_offset;
ssize_t base_addr, ref_ctr_offset;
+ bool legacy;
+
+ /* Check if new-style kprobe/uprobe API is supported.
+ * Kernels that support new FD-based kprobe and uprobe BPF attachment
+ * through perf_event_open() syscall expose
+ * /sys/bus/event_source/devices/kprobe/type and
+ * /sys/bus/event_source/devices/uprobe/type files, respectively. They
+ * contain magic numbers that are passed as "type" field of
+ * perf_event_attr. Lack of such file in the system indicates legacy
+ * kernel with old-style kprobe/uprobe attach interface through
+ * creating per-probe event through tracefs. For such cases
+ * ref_ctr_offset feature is not supported, so we don't test it.
+ */
+ legacy = access("/sys/bus/event_source/devices/kprobe/type", F_OK) != 0;
base_addr = get_base_addr();
if (CHECK(base_addr < 0, "get_base_addr",
@@ -45,10 +59,11 @@ void test_attach_probe(void)
goto cleanup;
skel->links.handle_kretprobe = kretprobe_link;
- ASSERT_EQ(uprobe_ref_ctr, 0, "uprobe_ref_ctr_before");
+ if (!legacy)
+ ASSERT_EQ(uprobe_ref_ctr, 0, "uprobe_ref_ctr_before");
uprobe_opts.retprobe = false;
- uprobe_opts.ref_ctr_offset = ref_ctr_offset;
+ uprobe_opts.ref_ctr_offset = legacy ? 0 : ref_ctr_offset;
uprobe_link = bpf_program__attach_uprobe_opts(skel->progs.handle_uprobe,
0 /* self pid */,
"/proc/self/exe",
@@ -58,11 +73,12 @@ void test_attach_probe(void)
goto cleanup;
skel->links.handle_uprobe = uprobe_link;
- ASSERT_GT(uprobe_ref_ctr, 0, "uprobe_ref_ctr_after");
+ if (!legacy)
+ ASSERT_GT(uprobe_ref_ctr, 0, "uprobe_ref_ctr_after");
/* if uprobe uses ref_ctr, uretprobe has to use ref_ctr as well */
uprobe_opts.retprobe = true;
- uprobe_opts.ref_ctr_offset = ref_ctr_offset;
+ uprobe_opts.ref_ctr_offset = legacy ? 0 : ref_ctr_offset;
uretprobe_link = bpf_program__attach_uprobe_opts(skel->progs.handle_uretprobe,
-1 /* any pid */,
"/proc/self/exe",
Make sure to not use ref_ctr_off feature when running on old kernels that don't support this feature. This allows to test libbpf's legacy kprobe and uprobe logic on old kernels. Signed-off-by: Andrii Nakryiko <andrii@kernel.org> --- .../selftests/bpf/prog_tests/attach_probe.c | 24 +++++++++++++++---- 1 file changed, 20 insertions(+), 4 deletions(-)