On Sat, Mar 2, 2024 at 8:50 AM Yonghong Song <yonghong.song@xxxxxxxxx> wrote:
>
> In my locally build clang LTO kernel (enabling CONFIG_LTO and
> CONFIG_LTO_CLANG_THIN), ksyms test failed like:
> test_ksyms:PASS:kallsyms_fopen 0 nsec
> test_ksyms:FAIL:ksym_find symbol 'bpf_link_fops' not found
> #118 ksyms:FAIL
>
> The reason is that 'bpf_link_fops' is renamed to
> bpf_link_fops.llvm.8325593422554671469
> Due to cross-file inlining, the static variable 'bpf_link_fops'
> in syscall.c is used by a function in another file. To avoid
> potential duplicated names, the llvm added suffix '.llvm.<hash>'.
>
> To fix the failure, we can skip this test with LTO kernel
> if the symbol 'bpf_link_fops' is not found in kallsyms.
>
> After this patch, with the same LTO kernel:
> #118 ksyms:SKIP
>
> Signed-off-by: Yonghong Song <yonghong.song@xxxxxxxxx>
> ---
> tools/testing/selftests/bpf/prog_tests/ksyms.c | 6 +++++-
> 1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/tools/testing/selftests/bpf/prog_tests/ksyms.c b/tools/testing/selftests/bpf/prog_tests/ksyms.c
> index e081f8bf3f17..cd81f190c5d7 100644
> --- a/tools/testing/selftests/bpf/prog_tests/ksyms.c
> +++ b/tools/testing/selftests/bpf/prog_tests/ksyms.c
> @@ -21,7 +21,11 @@ void test_ksyms(void)
> return;
> }
> if (err == -ENOENT) {
> - ASSERT_TRUE(false, "ksym_find for bpf_link_fops");
> + /* bpf_link_fops might be renamed to bpf_link_fops.llvm.<hash> in LTO kernel. */
> + if (check_lto_kernel() == 1)
> + test__skip();
> + else
> + ASSERT_TRUE(false, "ksym_find for bpf_link_fops");
I'm afraid LTO breakage is bigger than this.
pid_iter program as part of bpftool is using bpf_link_fops too.
I suspect that part of bpftool feature is broken on LTO kernel.
We need to find a solution instead of 'skip' a selftest.
