I encountered an issue when building the test_progs using the repository[1]:
$ clang --version
Ubuntu clang version 17.0.6 (++20231208085846+6009708b4367-1~exp1~20231208085949.74)
Target: x86_64-pc-linux-gnu
Thread model: posix
InstalledDir: /usr/bin
$ pwd
/work/Qemu/x86_64/linux-6.10-rc2/tools/testing/selftests/bpf/
$ make test_progs V=1
...
/work/Qemu/x86_64/linux-6.10-rc2/tools/testing/selftests/bpf/tools/sbin/bpftool
gen object
/work/Qemu/x86_64/linux-6.10-rc2/tools/testing/selftests/bpf/ip_check_defrag.bpf.linked2.o
/work/Qemu/x86_64/linux-6.10-rc2/tools/testing/selftests/bpf/ip_check_defrag.bpf.linked1.o
libbpf: failed to find symbol for variable 'bpf_dynptr_slice' in section
'.ksyms'
Error: failed to link
'/work/Qemu/x86_64/linux-6.10-rc2/tools/testing/selftests/bpf/ip_check_defrag.bpf.linked1.o':
No such file or directory (2)
make: *** [Makefile:656:
/work/Qemu/x86_64/linux-6.10-rc2/tools/testing/selftests/bpf/ip_check_defrag.skel.h]
Error 254
After investigation, I found that the btf_types in the '.ksyms' section have a kind of
BTF_KIND_FUNC instead of BTF_KIND_VAR:
$ bpftool btf dump file ./ip_check_defrag.bpf.linked1.o
...
[2] DATASEC '.ksyms' size=0 vlen=2
type_id=16 offset=0 size=0 (FUNC 'bpf_dynptr_from_skb')
type_id=17 offset=0 size=0 (FUNC 'bpf_dynptr_slice')
...
[16] FUNC 'bpf_dynptr_from_skb' type_id=82 linkage=extern
[17] FUNC 'bpf_dynptr_slice' type_id=85 linkage=extern
...
To fix this, we can a add check for the kind.
[1] https://github.com/eddyz87/bpf/tree/binsort-btf-dedup
Link: https://lore.kernel.org/all/[email protected]/
Fixes: 8fd27bf69b86 ("libbpf: Add BPF static linker BTF and BTF.ext support")
Signed-off-by: Donglin Peng <[email protected]>
---
tools/lib/bpf/linker.c | 11 +++++++++--
1 file changed, 9 insertions(+), 2 deletions(-)
diff --git a/tools/lib/bpf/linker.c b/tools/lib/bpf/linker.c
index 0d4be829551b..7f5fc9ac4ad6 100644
--- a/tools/lib/bpf/linker.c
+++ b/tools/lib/bpf/linker.c
@@ -2213,10 +2213,17 @@ static int linker_fixup_btf(struct src_obj *obj)
vi = btf_var_secinfos(t);
for (j = 0, m = btf_vlen(t); j < m; j++, vi++) {
const struct btf_type *vt = btf__type_by_id(obj->btf, vi->type);
- const char *var_name = btf__str_by_offset(obj->btf, vt->name_off);
- int var_linkage = btf_var(vt)->linkage;
+ const char *var_name;
+ int var_linkage;
Elf64_Sym *sym;
+ /* should be a variable */
+ if (btf_kind(vt) != BTF_KIND_VAR)
+ continue;
+
+ var_name = btf__str_by_offset(obj->btf, vt->name_off);
+ var_linkage = btf_var(vt)->linkage;
+
/* no need to patch up static or extern vars */
if (var_linkage != BTF_VAR_GLOBAL_ALLOCATED)
continue;
--
2.25.1