Commit d3b0e3b0 authored by Andrii Nakryiko's avatar Andrii Nakryiko Committed by Alexei Starovoitov
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selftests/bpf: Adopt attach_probe selftest to work on old kernels 



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: default avatarAndrii Nakryiko <andrii@kernel.org>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20210921210036.1545557-3-andrii@kernel.org
parent 303a2572

tools/testing/selftests/bpf/prog_tests/attach_probe.c

+20 −4
Original line number Diff line number Diff line
@@ -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;



	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;



	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",