On Fri, Jan 28, 2022 at 4:36 PM Matteo Croce <mcroce@xxxxxxxxxxxxxxxxxxx> wrote: > > On Fri, Jan 28, 2022 at 9:09 PM Alexei Starovoitov > <alexei.starovoitov@xxxxxxxxx> wrote: > > > > On Fri, Jan 28, 2022 at 10:51 AM Matteo Croce > > <mcroce@xxxxxxxxxxxxxxxxxxx> wrote: > > > > > > On Fri, Jan 28, 2022 at 6:31 AM Alexei Starovoitov > > > <alexei.starovoitov@xxxxxxxxx> wrote: > > > > > > > > On Mon, Dec 20, 2021 at 10:34 PM Yonghong Song <yhs@xxxxxx> wrote: > > > > > > > > > > > > > > > https://reviews.llvm.org/D116063 improved the error message as below > > > > > to make it a little bit more evident what is the problem: > > > > > > > > > > $ clang -target bpf -O2 -g -c bug.c > > > > > > > > > > fatal error: error in backend: SubroutineType not supported for > > > > > BTF_TYPE_ID_REMOTE reloc > > > > > > > > Hi Matteo, > > > > > > > > Are you still working on a test? > > > > What's a timeline to repost the patch set? > > > > > > > > Thanks! > > > > > > Hi Alexei, > > > > > > The change itself is ready, I'm just stuck at writing a test which > > > will effectively calls __bpf_core_types_are_compat() with some > > > recursion. > > > I guess that I have to generate a BTF_KIND_FUNC_PROTO type somehow, so > > > __bpf_core_types_are_compat() is called again to check the prototipe > > > arguments type. > > > I tried with these two, with no luck: > > > > > > // 1 > > > typedef int (*func_proto_typedef)(struct sk_buff *); > > > bpf_core_type_exists(func_proto_typedef); > > > > > > // 2 > > > void func_proto(int, unsigned int); > > > bpf_core_type_id_kernel(func_proto); > > > > > > Which is a simple way to generate a BTF_KIND_FUNC_PROTO BTF field? > > > > What do you mean 'no luck'? > > Have you tried what progs/test_core_reloc_type_id.c is doing? > > typedef int (*func_proto_typedef)(long); > > bpf_core_type_id_kernel(func_proto_typedef); > > > > Without macros: > > typedef int (*func_proto_typedef)(long); > > > > int test() { > > return __builtin_btf_type_id(*(typeof(func_proto_typedef) *)0, 1); > > } > > int test2() { > > return __builtin_preserve_type_info(*(typeof(func_proto_typedef) *)0, 0); > > } > > > > > > compiles fine and generates relos. > > Yes, I tried that one. > We reach bpf_core_apply_relo_insn() but not bpf_core_spec_match(), > since cands->len is 0. > > [ 16.424821] bpf_core_apply_relo_insn:1202 cands->len: 0 > > That's a very simple raw_tracepoint/sys_enter program: Did you forget to attach it ? If it's doing bpf_core_type_id_kernel(func_proto_typedef) then, of course, cands->len will be zero. You need to add this typedef to bpf_testmod first. Then use two typedef flavors: func_proto_typedef___match and func_proto_typedef___doesnt_match with matching and mismatching prototypes, so both can call into bpf_core_types_are_compat() and return different results. Then build on top to test recursion.
