On 3/4/24 9:37 PM, Alexei Starovoitov wrote:
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.
Thanks for pointing this out! Let me do some investigation on how to resolve this.
