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SubjectRe: ERROR: INT DW_ATE_unsigned_1 Error emitting BTF type
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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 -
>

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