I hit the following failure when running selftests with
internal backported upstream kernel:
test_ksyms:PASS:kallsyms_fopen 0 nsec
test_ksyms:FAIL:ksym_find symbol 'bpf_link_fops' not found
#123 ksyms:FAIL
In /proc/kallsyms, we have
$ cat /proc/kallsyms | grep bpf_link_fops
ffffffff829f0cb0 d bpf_link_fops.llvm.12608678492448798416
The CONFIG_LTO_CLANG_THIN is enabled in the kernel which is responsible
for bpf_link_fops.llvm.12608678492448798416 symbol name.
In prog_tests/ksyms.c we have
kallsyms_find("bpf_link_fops", &link_fops_addr)
and kallsyms_find() compares "bpf_link_fops" with symbols
in /proc/kallsyms in order to find the entry. With
bpf_link_fops.llvm.<hash> in /proc/kallsyms, the kallsyms_find()
failed.
To fix the issue, in kallsyms_find(), if a symbol has suffix
.llvm.<hash>, that suffix will be ignored for comparison.
This fixed the test failure.
Signed-off-by: Yonghong Song <yonghong.song@xxxxxxxxx>
---
tools/testing/selftests/bpf/trace_helpers.c | 12 ++++++++++++
1 file changed, 12 insertions(+)
diff --git a/tools/testing/selftests/bpf/trace_helpers.c b/tools/testing/selftests/bpf/trace_helpers.c
index 70e29f316fe7..dc871e642ed5 100644
--- a/tools/testing/selftests/bpf/trace_helpers.c
+++ b/tools/testing/selftests/bpf/trace_helpers.c
@@ -221,6 +221,18 @@ int kallsyms_find(const char *sym, unsigned long long *addr)
return -EINVAL;
while (fscanf(f, "%llx %c %499s%*[^\n]\n", &value, &type, name) > 0) {
+ /* If CONFIG_LTO_CLANG_THIN is enabled, static variable/function
+ * symbols could be promoted to global due to cross-file inlining.
+ * For such cases, clang compiler will add .llvm.<hash> suffix
+ * to those symbols to avoid potential naming conflict.
+ * Let us ignore .llvm.<hash> suffix during symbol comparison.
+ */
+ if (type == 'd') {
+ char *res = strstr(name, ".llvm.");
+
+ if (res)
+ *res = '\0';
+ }
if (strcmp(name, sym) == 0) {
*addr = value;
goto out;
--
2.43.0
