Re: [PATCH bpf-next 1/3] selftests/bpf: Keep int return type for tailcall subprogs with maps

[Yonghong Song <yonghong.song@linux.dev>]

On 6/9/26 2:49 PM, Alexei Starovoitov wrote:
> On Tue Jun 9, 2026 at 2:30 PM PDT, Yonghong Song wrote:
>> const struct bpf_func_proto bpf_tail_call_proto = {         /* func is
>> unused for tail_call, we set it to pass the          * get_helper_proto
>> check          */         .func           = BPF_PTR_POISON,
>> .gpl_only       = false,         .ret_type       = RET_VOID,
>> .arg1_type      = ARG_PTR_TO_CTX,         .arg2_type      =
>> ARG_CONST_MAP_PTR,         .arg3_type      = ARG_ANYTHING, }; and for
>> RET_VOID, we have below in verifier.c:         switch
>> (base_type(ret_type)) {         case RET_INTEGER:                 /*
>> sets type to SCALAR_VALUE */                 mark_reg_unknown(env, regs,
>> BPF_REG_0);                 break;         case RET_VOID:
>>     regs[BPF_REG_0].type = NOT_INIT;                 break; so we cannot
>> return 'r0'.
> Ahh, so bpf_tail_call() is a void return.
> Then, I'll take it back. bpf_tail_call_static() is correct with void return.
> I guess we have to teach the verifier to accept void subprogs asap.
>
> In the meantime let's do shortest possible hack for tailcall_bpf2bpf_hierarchy1.c
> to pass with llvm 23.

Sounds good. Will do.