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selftests/bpf: Ignore .llvm.<hash> suffix in kallsyms_find()

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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@linux.dev>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20240604180034.1356016-1-yonghong.song@linux.dev
This commit is contained in:
Yonghong Song
2024-06-04 11:00:34 -07:00
committed by Andrii Nakryiko
parent 61ce0ea759
commit 898ac74c5b
1 changed files with 12 additions and 1 deletions
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13
tools/testing/selftests/bpf/trace_helpers.c
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@@ -211,7 +211,7 @@ long ksym_get_addr(const char *name)
*/
int kallsyms_find(const char *sym, unsigned long long *addr)
{
char type, name[500];
char type, name[500], *match;
unsigned long long value;
int err = 0;
FILE *f;
@@ -221,6 +221,17 @@ 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') {
match = strstr(name, ".llvm.");
if (match)
*match = '\0';
}
if (strcmp(name, sym) == 0) {
*addr = value;
goto out;