From: Yonghong Song <yonghong.song@linux.dev>
To: bpf@vger.kernel.org
Cc: Alexei Starovoitov <ast@kernel.org>,
Andrii Nakryiko <andrii@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
kernel-team@fb.com, Martin KaFai Lau <martin.lau@kernel.org>
Subject: [PATCH bpf-next] bpf: Fix a few selftest failures due to llvm18 change
Date: Sun, 26 Nov 2023 21:03:42 -0800 [thread overview]
Message-ID: <20231127050342.1945270-1-yonghong.song@linux.dev> (raw)
With latest upstream llvm18, the following test cases failed:
$ ./test_progs -j
#13/2 bpf_cookie/multi_kprobe_link_api:FAIL
#13/3 bpf_cookie/multi_kprobe_attach_api:FAIL
#13 bpf_cookie:FAIL
#77 fentry_fexit:FAIL
#78/1 fentry_test/fentry:FAIL
#78 fentry_test:FAIL
#82/1 fexit_test/fexit:FAIL
#82 fexit_test:FAIL
#112/1 kprobe_multi_test/skel_api:FAIL
#112/2 kprobe_multi_test/link_api_addrs:FAIL
...
#112 kprobe_multi_test:FAIL
#356/17 test_global_funcs/global_func17:FAIL
#356 test_global_funcs:FAIL
Further analysis shows llvm upstream patch [1] is responsible
for the above failures. For example, for function bpf_fentry_test7()
in net/bpf/test_run.c, without [1], the asm code is:
0000000000000400 <bpf_fentry_test7>:
400: f3 0f 1e fa endbr64
404: e8 00 00 00 00 callq 0x409 <bpf_fentry_test7+0x9>
409: 48 89 f8 movq %rdi, %rax
40c: c3 retq
40d: 0f 1f 00 nopl (%rax)
and with [1], the asm code is:
0000000000005d20 <bpf_fentry_test7.specialized.1>:
5d20: e8 00 00 00 00 callq 0x5d25 <bpf_fentry_test7.specialized.1+0x5>
5d25: c3 retq
and <bpf_fentry_test7.specialized.1> is called instead of <bpf_fentry_test7>
and this caused test failures for #13/#77 etc. except #356.
For test case #356/17, with [1] (progs/test_global_func17.c)),
the main prog looks like:
0000000000000000 <global_func17>:
0: b4 00 00 00 2a 00 00 00 w0 = 0x2a
1: 95 00 00 00 00 00 00 00 exit
which passed verification while the test itself expects a verification
failure.
Let us add 'barrier_var' style asm code in both places to prevent
function specialization which caused selftests failure.
[1] https://github.com/llvm/llvm-project/pull/72903
Signed-off-by: Yonghong Song <yonghong.song@linux.dev>
---
net/bpf/test_run.c | 2 +-
tools/testing/selftests/bpf/progs/test_global_func17.c | 1 +
2 files changed, 2 insertions(+), 1 deletion(-)
diff --git a/net/bpf/test_run.c b/net/bpf/test_run.c
index c9fdcc5cdce1..711cf5d59816 100644
--- a/net/bpf/test_run.c
+++ b/net/bpf/test_run.c
@@ -542,7 +542,7 @@ struct bpf_fentry_test_t {
int noinline bpf_fentry_test7(struct bpf_fentry_test_t *arg)
{
- asm volatile ("");
+ asm volatile ("": "+r"(arg));
return (long)arg;
}
diff --git a/tools/testing/selftests/bpf/progs/test_global_func17.c b/tools/testing/selftests/bpf/progs/test_global_func17.c
index a32e11c7d933..5de44b09e8ec 100644
--- a/tools/testing/selftests/bpf/progs/test_global_func17.c
+++ b/tools/testing/selftests/bpf/progs/test_global_func17.c
@@ -5,6 +5,7 @@
__noinline int foo(int *p)
{
+ barrier_var(p);
return p ? (*p = 42) : 0;
}
--
2.34.1
next reply other threads:[~2023-11-27 5:04 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-11-27 5:03 Yonghong Song [this message]
2023-11-27 14:00 ` [PATCH bpf-next] bpf: Fix a few selftest failures due to llvm18 change patchwork-bot+netdevbpf
2023-11-27 18:49 ` Andrii Nakryiko
2023-11-27 19:49 ` Yonghong Song
2023-11-27 19:57 ` Andrii Nakryiko
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