@@ -3409,11 +3409,6 @@ static int bpf_object__collect_externs(struct bpf_object *obj)
return -ENOTSUP;
}
} else if (strcmp(sec_name, KSYMS_SEC) == 0) {
- if (btf_is_func(t) && ext->is_weak) {
- pr_warn("extern weak function %s is unsupported\n",
- ext->name);
- return -ENOTSUP;
- }
ksym_sec = sec;
ext->type = EXT_KSYM;
skip_mods_and_typedefs(obj->btf, t->type,
@@ -5342,8 +5337,12 @@ bpf_object__relocate_data(struct bpf_object *obj, struct bpf_program *prog)
case RELO_EXTERN_FUNC:
ext = &obj->externs[relo->sym_off];
insn[0].src_reg = BPF_PSEUDO_KFUNC_CALL;
- insn[0].imm = ext->ksym.kernel_btf_id;
- insn[0].off = ext->ksym.offset;
+ if (ext->is_set) {
+ insn[0].imm = ext->ksym.kernel_btf_id;
+ insn[0].off = ext->ksym.offset;
+ } else { /* unresolved weak kfunc */
+ insn[0].imm = insn[0].off = 0;
+ }
break;
case RELO_SUBPROG_ADDR:
if (insn[0].src_reg != BPF_PSEUDO_FUNC) {
@@ -6734,8 +6733,10 @@ static int bpf_object__resolve_ksym_func_btf_id(struct bpf_object *obj,
kfunc_id = find_ksym_btf_id(obj, ext->name, BTF_KIND_FUNC,
&kern_btf, &kern_btf_fd);
- if (kfunc_id < 0) {
- pr_warn("extern (func ksym) '%s': not found in kernel BTF\n",
+ if (kfunc_id == -ESRCH && ext->is_weak) {
+ return 0;
+ } else if (kfunc_id < 0) {
+ pr_warn("extern (func ksym) '%s': not found in kernel or module BTFs\n",
ext->name);
return kfunc_id;
}
Preserve these calls as it allows verifier to succeed in loading the program if they are determined to be unreachable after dead code elimination during program load. If not, the verifier will fail at runtime. This is done for ext->is_weak symbols similar to the case for variable ksyms. Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com> --- tools/lib/bpf/libbpf.c | 19 ++++++++++--------- 1 file changed, 10 insertions(+), 9 deletions(-)