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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: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20210921210036.1545557-3-andrii@kernel.org
This commit is contained in:
Andrii Nakryiko 2021-09-21 14:00:34 -07:00 committed by Alexei Starovoitov
parent 303a257223
commit d3b0e3b03c
1 changed files with 20 additions and 4 deletions
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24
tools/testing/selftests/bpf/prog_tests/attach_probe.c
View File

@ -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",