When building the selftest with arm64/clang20, the following test failed:
...
ubtest_multispec_usdt:PASS:usdt_100_called 0 nsec
subtest_multispec_usdt:PASS:usdt_100_sum 0 nsec
subtest_multispec_usdt:FAIL:usdt_300_bad_attach unexpected pointer: 0xaaaad82a2a80
#469/2 usdt/multispec:FAIL
#469 usdt:FAIL
But gcc11 built kernel/selftests succeeded. Further debug found clang generated
code has much less argument pattern after dedup, but gcc generated code has
a lot more.
Below is the test:usdt_100 stapsdt's with clang20 generated binary:
$ readelf -n usdt.test.o
Displaying notes found in: .note.stapsdt
Owner Data size Description
stapsdt 0x0000002e NT_STAPSDT (SystemTap probe descriptors)
Provider: test
Name: usdt_100
Location: 0x0000000000000024, Base: 0x0000000000000000, Semaphore: 0x0000000000000006
Arguments: -4@[x9]
stapsdt 0x0000002e NT_STAPSDT (SystemTap probe descriptors)
Provider: test
Name: usdt_100
Location: 0x000000000000003c, Base: 0x0000000000000000, Semaphore: 0x0000000000000006
Arguments: -4@[x9]
...
stapsdt 0x0000002e NT_STAPSDT (SystemTap probe descriptors)
Provider: test
Name: usdt_100
Location: 0x0000000000000954, Base: 0x0000000000000000, Semaphore: 0x0000000000000006
Arguments: -4@[x9]
stapsdt 0x0000002e NT_STAPSDT (SystemTap probe descriptors)
Provider: test
Name: usdt_100
Location: 0x000000000000096c, Base: 0x0000000000000000, Semaphore: 0x0000000000000006
Arguments: -4@[x8]
Below is the test:usdt_100 stapsdt's with gcc11 generated binary:
$ readelf -n usdt.test.o
Displaying notes found in: .note.stapsdt
Owner Data size Description
...
stapsdt 0x0000002e NT_STAPSDT (SystemTap probe descriptors)
Provider: test
Name: usdt_100
Location: 0x000000000000470c, Base: 0x0000000000000000, Semaphore: 0x0000000000000006
Arguments: -4@[sp]
stapsdt 0x00000031 NT_STAPSDT (SystemTap probe descriptors)
Provider: test
Name: usdt_100
Location: 0x0000000000004724, Base: 0x0000000000000000, Semaphore: 0x0000000000000006
Arguments: -4@[sp, 4]
...
stapsdt 0x00000033 NT_STAPSDT (SystemTap probe descriptors)
Provider: test
Name: usdt_100
Location: 0x000000000000503c, Base: 0x0000000000000000, Semaphore: 0x0000000000000006
Arguments: -4@[sp, 392]
stapsdt 0x00000033 NT_STAPSDT (SystemTap probe descriptors)
Provider: test
Name: usdt_100
Location: 0x0000000000005054, Base: 0x0000000000000000, Semaphore: 0x0000000000000006
Arguments: -4@[sp, 396]
Considering libbpf dedup of usdt spec's, the clang generated code has 3 spec's, and
gcc has 100 spec's. Due to this, bpf_program__attach_usdt() failed with gcc but succeeded
with clang. To fix the test failure for clang generated code, make bpf_program__attach_usdt()
succeed with necessary macro guards.
Signed-off-by: Yonghong Song <yonghong.song@xxxxxxxxx>
---
tools/testing/selftests/bpf/prog_tests/usdt.c | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/tools/testing/selftests/bpf/prog_tests/usdt.c b/tools/testing/selftests/bpf/prog_tests/usdt.c
index 495d66414b57..7429029cbd63 100644
--- a/tools/testing/selftests/bpf/prog_tests/usdt.c
+++ b/tools/testing/selftests/bpf/prog_tests/usdt.c
@@ -272,12 +272,19 @@ static void subtest_multispec_usdt(void)
/* we'll reuse usdt_100 BPF program for usdt_300 test */
bpf_link__destroy(skel->links.usdt_100);
+
skel->links.usdt_100 = bpf_program__attach_usdt(skel->progs.usdt_100, -1, "/proc/self/exe",
"test", "usdt_300", NULL);
+#if __clang__ && defined(__aarch64__)
+ if (!ASSERT_OK_PTR(skel->links.usdt_100, "usdt_300_bad_attach"))
+ goto cleanup;
+ bpf_link__destroy(skel->links.usdt_100);
+#else
err = -errno;
if (!ASSERT_ERR_PTR(skel->links.usdt_100, "usdt_300_bad_attach"))
goto cleanup;
ASSERT_EQ(err, -E2BIG, "usdt_300_attach_err");
+#endif
/* let's check that there are no "dangling" BPF programs attached due
* to partial success of the above test:usdt_300 attachment
--
2.47.1
