Re: ERROR: INT DW_ATE_unsigned_1 Error emitting BTF type

[Yonghong Song <yhs@fb.com>]

On 2/5/21 11:15 AM, Sedat Dilek wrote:
> On Fri, Feb 5, 2021 at 8:10 PM Yonghong Song <yhs@fb.com> wrote:
>>
>>
>>
>> On 2/5/21 11:06 AM, Sedat Dilek wrote:
>>> On Fri, Feb 5, 2021 at 7:53 PM Sedat Dilek <sedat.dilek@gmail.com> wrote:
>>>>
>>>> On Fri, Feb 5, 2021 at 6:48 PM Sedat Dilek <sedat.dilek@gmail.com> wrote:
>>>>>
>>>>> On Fri, Feb 5, 2021 at 4:28 PM Arnaldo Carvalho de Melo
>>>>> <arnaldo.melo@gmail.com> wrote:
>>>>>>
>>>>>> Em Fri, Feb 05, 2021 at 04:23:59PM +0100, Sedat Dilek escreveu:
>>>>>>> On Fri, Feb 5, 2021 at 3:41 PM Sedat Dilek <sedat.dilek@gmail.com> wrote:
>>>>>>>>
>>>>>>>> On Fri, Feb 5, 2021 at 3:37 PM Sedat Dilek <sedat.dilek@gmail.com> wrote:
>>>>>>>>>
>>>>>>>>> Hi,
>>>>>>>>>
>>>>>>>>> when building with pahole v1.20 and binutils v2.35.2 plus Clang
>>>>>>>>> v12.0.0-rc1 and DWARF-v5 I see:
>>>>>>>>> ...
>>>>>>>>> + info BTF .btf.vmlinux.bin.o
>>>>>>>>> + [  != silent_ ]
>>>>>>>>> + printf   %-7s %s\n BTF .btf.vmlinux.bin.o
>>>>>>>>>    BTF     .btf.vmlinux.bin.o
>>>>>>>>> + LLVM_OBJCOPY=/opt/binutils/bin/objcopy /opt/pahole/bin/pahole -J
>>>>>>>>> .tmp_vmlinux.btf
>>>>>>>>> [115] INT DW_ATE_unsigned_1 Error emitting BTF type
>>>>>>>>> Encountered error while encoding BTF.
>>>>>>>>
>>>>>>>> Grepping the pahole sources:
>>>>>>>>
>>>>>>>> $ git grep DW_ATE
>>>>>>>> dwarf_loader.c:         bt->is_bool = encoding == DW_ATE_boolean;
>>>>>>>> dwarf_loader.c:         bt->is_signed = encoding == DW_ATE_signed;
>>>>>>>>
>>>>>>>> Missing DW_ATE_unsigned encoding?
>>>>>>>>
>>>>>>>
>>>>>>> Checked the LLVM sources:
>>>>>>>
>>>>>>> clang/lib/CodeGen/CGDebugInfo.cpp:    Encoding =
>>>>>>> llvm::dwarf::DW_ATE_unsigned_char;
>>>>>>> clang/lib/CodeGen/CGDebugInfo.cpp:    Encoding = llvm::dwarf::DW_ATE_unsigned;
>>>>>>> clang/lib/CodeGen/CGDebugInfo.cpp:    Encoding =
>>>>>>> llvm::dwarf::DW_ATE_unsigned_fixed;
>>>>>>> clang/lib/CodeGen/CGDebugInfo.cpp:
>>>>>>>     ? llvm::dwarf::DW_ATE_unsigned
>>>>>>> ...
>>>>>>> lld/test/wasm/debuginfo.test:CHECK-NEXT:                DW_AT_encoding
>>>>>>>    (DW_ATE_unsigned)
>>>>>>>
>>>>>>> So, I will switch from GNU ld.bfd v2.35.2 to LLD-12.
>>>>>>
>>>>>> Thanks for the research, probably your conclusion is correct, can you go
>>>>>> the next step and add that part and check if the end result is the
>>>>>> expected one?
>>>>>>
>>>>>
>>>>> Still building...
>>>>>
>>>>> Can you give me a hand on what has to be changed in dwarves/pahole?
>>>>>
>>>>> I guess switching from ld.bfd to ld.lld will show the same ERROR.
>>>>>
>>>>
>>>> This builds successfully - untested:
>>>>
>>>> $ git diff
>>>> diff --git a/btf_loader.c b/btf_loader.c
>>>> index ec286f413f36..a39edd3362db 100644
>>>> --- a/btf_loader.c
>>>> +++ b/btf_loader.c
>>>> @@ -107,6 +107,7 @@ static struct base_type *base_type__new(strings_t
>>>> name, uint32_t attrs,
>>>>                  bt->bit_size = size;
>>>>                  bt->is_signed = attrs & BTF_INT_SIGNED;
>>>>                  bt->is_bool = attrs & BTF_INT_BOOL;
>>>> +               bt->is_unsigned = attrs & BTF_INT_UNSIGNED;
>>>>                  bt->name_has_encoding = false;
>>>>                  bt->float_type = float_type;
>>>>          }
>>>> diff --git a/ctf.h b/ctf.h
>>>> index 25b79892bde3..9e47c3c74677 100644
>>>> --- a/ctf.h
>>>> +++ b/ctf.h
>>>> @@ -100,6 +100,7 @@ struct ctf_full_type {
>>>> #define CTF_TYPE_INT_CHAR      0x2
>>>> #define CTF_TYPE_INT_BOOL      0x4
>>>> #define CTF_TYPE_INT_VARARGS   0x8
>>>> +#define CTF_TYPE_INT_UNSIGNED  0x16
>>>>
>>>> #define CTF_TYPE_FP_ATTRS(VAL)         ((VAL) >> 24)
>>>> #define CTF_TYPE_FP_OFFSET(VAL)                (((VAL) >> 16) & 0xff)
>>>> diff --git a/dwarf_loader.c b/dwarf_loader.c
>>>> index b73d7867e1e6..79d40f183c24 100644
>>>> --- a/dwarf_loader.c
>>>> +++ b/dwarf_loader.c
>>>> @@ -473,6 +473,7 @@ static struct base_type *base_type__new(Dwarf_Die
>>>> *die, struct cu *cu)
>>>>                  bt->is_bool = encoding == DW_ATE_boolean;
>>>>                  bt->is_signed = encoding == DW_ATE_signed;
>>>>                  bt->is_varargs = false;
>>>> +               bt->is_unsigned = encoding == DW_ATE_unsigned;
>>>>                  bt->name_has_encoding = true;
>>>>          }
>>>>
>>>> diff --git a/dwarves.h b/dwarves.h
>>>> index 98caf1abc54d..edf32d2e6f80 100644
>>>> --- a/dwarves.h
>>>> +++ b/dwarves.h
>>>> @@ -1261,6 +1261,7 @@ struct base_type {
>>>>          uint8_t         is_signed:1;
>>>>          uint8_t         is_bool:1;
>>>>          uint8_t         is_varargs:1;
>>>> +       uint8_t         is_unsigned:1;
>>>>          uint8_t         float_type:4;
>>>> };
>>>>
>>>> diff --git a/lib/bpf b/lib/bpf
>>>> --- a/lib/bpf
>>>> +++ b/lib/bpf
>>>> @@ -1 +1 @@
>>>> -Subproject commit 5af3d86b5a2c5fecdc3ab83822d083edd32b4396
>>>> +Subproject commit 5af3d86b5a2c5fecdc3ab83822d083edd32b4396-dirty
>>>> diff --git a/libbtf.c b/libbtf.c
>>>> index 9f7628304495..a0661a7bbed9 100644
>>>> --- a/libbtf.c
>>>> +++ b/libbtf.c
>>>> @@ -247,6 +247,8 @@ static const char *
>>>> btf_elf__int_encoding_str(uint8_t encoding)
>>>>                  return "CHAR";
>>>>          else if (encoding == BTF_INT_BOOL)
>>>>                  return "BOOL";
>>>> +       else if (encoding == BTF_INT_UNSIGNED)
>>>> +               return "UNSIGNED";
>>>>          else
>>>>                  return "UNKN";
>>>> }
>>>> @@ -379,6 +381,8 @@ int32_t btf_elf__add_base_type(struct btf_elf
>>>> *btfe, const struct base_type *bt,
>>>>                  encoding = BTF_INT_SIGNED;
>>>>          } else if (bt->is_bool) {
>>>>                  encoding = BTF_INT_BOOL;
>>>> +       } else if (bt->is_unsigned) {
>>>> +               encoding = BTF_INT_UNSIGNED;
>>>>          } else if (bt->float_type) {
>>>>                  fprintf(stderr, "float_type is not supported\n");
>>>>                  return -1;
>>>>
>>>> Additionally - I cannot see it with `git diff`:
>>>>
>>>> [ lib/bpf/include/uapi/linux/btf.h ]
>>>>
>>>> /* Attributes stored in the BTF_INT_ENCODING */
>>>> #define BTF_INT_SIGNED (1 << 0)
>>>> #define BTF_INT_CHAR (1 << 1)
>>>> #define BTF_INT_BOOL (1 << 2)
>>>> #define BTF_INT_UNSIGNED (1 << 3)
>>>>
>>>> Comments?
>>>>
>>>
>>> Hmmm...
>>>
>>> + info BTF .btf.vmlinux.bin.o
>>> + [  != silent_ ]
>>> + printf   %-7s %s\n BTF .btf.vmlinux.bin.o
>>>    BTF     .btf.vmlinux.bin.o
>>> + LLVM_OBJCOPY=llvm-objcopy /opt/pahole/bin/pahole -J .tmp_vmlinux.btf
>>> [2] INT long unsigned int Error emitting BTF type
>>> Encountered error while encoding BTF.
>>> + llvm-objcopy --only-section=.BTF --set-section-flags
>>> .BTF=alloc,readonly --strip-all .tmp_vmlinux.btf .btf.vmlinux.bin.o
>>> ...
>>> + info BTFIDS vmlinux
>>> + [  != silent_ ]
>>> + printf   %-7s %s\n BTFIDS vmlinux
>>>    BTFIDS  vmlinux
>>> + ./tools/bpf/resolve_btfids/resolve_btfids vmlinux
>>> FAILED: load BTF from vmlinux: Invalid argument
>>> + on_exit
>>> + [ 255 -ne 0 ]
>>> + cleanup
>>> + rm -f .btf.vmlinux.bin.o
>>> + rm -f .tmp_System.map
>>> + rm -f .tmp_vmlinux.btf .tmp_vmlinux.kallsyms1
>>> .tmp_vmlinux.kallsyms1.S .tmp_vmlinux.kallsyms1.o
>>> .tmp_vmlinux.kallsyms2 .tmp_vmlinux.kallsyms2.S .tmp_vmlinux.kallsyms
>>> 2.o
>>> + rm -f System.map
>>> + rm -f vmlinux
>>> + rm -f vmlinux.o
>>> make[3]: *** [Makefile:1166: vmlinux] Error 255
>>>
>>> Grepping through linux.git/tools I guess some BTF tools/libs need to
>>> know what BTF_INT_UNSIGNED is?
>>
>> BTF_INT_UNSIGNED needs kernel support. Maybe to teach pahole to
>> ignore this for now until kernel infrastructure is ready.
>> Not sure whether this information will be useful or not
>> for BTF. This needs to be discussed separately.
>>
> 
> [ CC Fangrui ]
> 
> How can I teach pahole to ignore BTF_INT_UNSIGNED?

i mean for the following:

@@ -379,6 +381,8 @@ int32_t btf_elf__add_base_type(struct btf_elf
*btfe, const struct base_type *bt,
                 encoding = BTF_INT_SIGNED;
         } else if (bt->is_bool) {
                 encoding = BTF_INT_BOOL;
+       } else if (bt->is_unsigned) {
+               encoding = BTF_INT_UNSIGNED;
         } else if (bt->float_type) {
                 fprintf(stderr, "float_type is not supported\n");
                 return -1;

You can do

@@ -379,6 +381,8 @@ int32_t btf_elf__add_base_type(struct btf_elf
*btfe, const struct base_type *bt,
                 encoding = BTF_INT_SIGNED;
         } else if (bt->is_bool) {
                 encoding = BTF_INT_BOOL;
+       } else if (bt->is_unsigned) {
+               ; /* ignored for now */
         } else if (bt->float_type) {
                 fprintf(stderr, "float_type is not supported\n");
                 return -1;

The default encoding is 0 which indicates an unsigned int.

> 
> Another tryout might be to use "-fbinutils-version=..." which is
> available for LLVM-12 according to Fangrui?
> Fangrui, which binutils versions can I pass and how?

> 
> Thanks.
> 
> - Sedat -
>