linux-kernel - Re: ERROR: INT DW_ATE_unsigned

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Message-ID: <cb743ab8-9a66-a311-ed18-ecabf0947440@fb.com>
Date:   Fri, 5 Feb 2021 12:03:05 -0800
From:   Yonghong Song <yhs@...com>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>
CC:     <sedat.dilek@...il.com>,
        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 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.

> 
> - ARnaldo
>