linux-kernel - Re: ERROR: INT DW_ATE_unsigned

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Message-ID: <d59c2a53-976c-c304-f208-67110bdd728a@fb.com>
Date:   Fri, 5 Feb 2021 13:54:02 -0800
From:   Yonghong Song <yhs@...com>
To:     <sedat.dilek@...il.com>
CC:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Arnaldo Carvalho de Melo <arnaldo.melo@...il.com>,
        <dwarves@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        <bpf@...r.kernel.org>, Jiri Olsa <jolsa@...nel.org>,
        Jan Engelhardt <jengelh@...i.de>,
        Domenico Andreoli <cavok@...ian.org>,
        Matthias Schwarzott <zzam@...too.org>,
        Andrii Nakryiko <andriin@...com>,
        Mark Wieelard <mjw@...hat.com>,
        Paul Moore <paul@...l-moore.com>,
        Ondrej Mosnacek <omosnace@...hat.com>,
        Daniel P. Berrangé <berrange@...hat.com>,
        Tom Stellard <tstellar@...hat.com>
Subject: Re: ERROR: INT DW_ATE_unsigned_1 Error emitting BTF type



On 2/5/21 12:31 PM, Sedat Dilek wrote:
> On Fri, Feb 5, 2021 at 9:03 PM Yonghong Song <yhs@...com> wrote:
>>
>>
>>
>> On 2/5/21 11:24 AM, Arnaldo Carvalho de Melo wrote:
>>> Em Fri, Feb 05, 2021 at 11:10:08AM -0800, Yonghong Song escreveu:
>>>> On 2/5/21 11:06 AM, Sedat Dilek wrote:
>>>>> On Fri, Feb 5, 2021 at 7:53 PM Sedat Dilek <sedat.dilek@...il.com> wrote:
>>>>> 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.
>>>
>>> Yeah, I thought about doing that.
>>>
>>>> Not sure whether this information will be useful or not
>>>> for BTF. This needs to be discussed separately.
>>>
>>> Maybe search for the rationale for its introduction in DWARF.
>>
>> In LLVM, we have:
>>     uint8_t BTFEncoding;
>>     switch (Encoding) {
>>     case dwarf::DW_ATE_boolean:
>>       BTFEncoding = BTF::INT_BOOL;
>>       break;
>>     case dwarf::DW_ATE_signed:
>>     case dwarf::DW_ATE_signed_char:
>>       BTFEncoding = BTF::INT_SIGNED;
>>       break;
>>     case dwarf::DW_ATE_unsigned:
>>     case dwarf::DW_ATE_unsigned_char:
>>       BTFEncoding = 0;
>>       break;
>>
>> I think DW_ATE_unsigned can be ignored in pahole since
>> the default encoding = 0. A simple comment is enough.
>>
> 
> Yonghong Son, do you have a patch/diff for me?

Looking at error message from log:

  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.

Not exactly what is the root cause. Maybe bt->bit_size is not
encoded correctly. Could you put vmlinux (in the above it is
.tmp_vmlinux.btf) somewhere, I or somebody else can investigate
and provide a proper fix.

> Thanks.
> 
> - Sedat -
>