From: Sedat Dilek <sedat.dilek@gmail.com>
To: Yonghong Song <yhs@fb.com>
Cc: "Mark Wieelard" <mark@klomp.org>,
"Masahiro Yamada" <masahiroy@kernel.org>,
"Arnaldo Carvalho de Melo" <acme@kernel.org>,
"Arnaldo Carvalho de Melo" <arnaldo.melo@gmail.com>,
dwarves@vger.kernel.org,
"Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>,
bpf@vger.kernel.org, "Jiri Olsa" <jolsa@kernel.org>,
"Jan Engelhardt" <jengelh@inai.de>,
"Domenico Andreoli" <cavok@debian.org>,
"Matthias Schwarzott" <zzam@gentoo.org>,
"Andrii Nakryiko" <andriin@fb.com>,
"Paul Moore" <paul@paul-moore.com>,
"Ondrej Mosnacek" <omosnace@redhat.com>,
"Daniel P. Berrangé" <berrange@redhat.com>,
"Tom Stellard" <tstellar@redhat.com>
Subject: Re: ERROR: INT DW_ATE_unsigned_1 Error emitting BTF type
Date: Sat, 6 Feb 2021 19:10:37 +0100 [thread overview]
Message-ID: <CA+icZUVfTH=yONintyJ+T8kvTrR4Q0gumJYNUCs6Ybraff5Kpg@mail.gmail.com> (raw)
In-Reply-To: <3f5a00ef-1c71-d0da-e9fd-c7f707760f5c@fb.com>
On Sat, Feb 6, 2021 at 6:53 PM Yonghong Song <yhs@fb.com> wrote:
>
>
>
> On 2/6/21 8:24 AM, Mark Wieelard wrote:
> > Hi,
> >
> > On Sat, Feb 06, 2021 at 12:26:44AM -0800, Yonghong Song wrote:
> >> With the above vmlinux, the issue appears to be handling
> >> DW_ATE_signed_1, DW_ATE_unsigned_{1,24,40}.
> >>
> >> The following patch should fix the issue:
> >
> > That doesn't really make sense to me. Why is the compiler emitting a
> > DW_TAG_base_type that needs to be interpreted according to the
> > DW_AT_name attribute?
> >
> > If the issue is that the size of the base type cannot be expressed in
> > bytes then the DWARF spec provides the following option:
> >
> > If the value of an object of the given type does not fully occupy
> > the storage described by a byte size attribute, the base type
> > entry may also have a DW_AT_bit_size and a DW_AT_data_bit_offset
> > attribute, both of whose values are integer constant values (see
> > Section 2.19 on page 55). The bit size attribute describes the
> > actual size in bits used to represent values of the given
> > type. The data bit offset attribute is the offset in bits from the
> > beginning of the containing storage to the beginning of the
> > value. Bits that are part of the offset are padding. If this
> > attribute is omitted a default data bit offset of zero is assumed.
> >
> > Would it be possible to use that encoding of those special types? If
>
> I agree with you. I do not like comparing me as well. Unfortunately,
> there is no enough information in dwarf to find out actual information.
> The following is the dwarf dump with vmlinux (Sedat provided) for
> DW_ATE_unsigned_1.
>
> 0x000e97e9: DW_TAG_base_type
> DW_AT_name ("DW_ATE_unsigned_1")
> DW_AT_encoding (DW_ATE_unsigned)
> DW_AT_byte_size (0x00)
>
> There is no DW_AT_bit_size and DW_AT_bit_offset for base type.
> AFAIK, these two attributes typically appear in struct/union members
> together with DW_AT_byte_size.
>
> Maybe compilers (clang in this case) can emit DW_AT_bit_size = 1
> and DW_AT_bit_offset = 0/7 (depending on big/little endian) and
> this case, we just test and get DW_AT_bit_size and it should work.
>
> But I think BTF does not need this (DW_ATE_unsigned_1) for now.
> I checked dwarf dump and it is mostly used for some arith operation
> encoded in dump (in this case, e.g., shift by 1 bit)
>
> 0x000015cf: DW_TAG_base_type
> DW_AT_name ("DW_ATE_unsigned_1")
> DW_AT_encoding (DW_ATE_unsigned)
> DW_AT_byte_size (0x00)
>
> 0x00010ed9: DW_TAG_formal_parameter
> DW_AT_location (DW_OP_lit0, DW_OP_not,
> DW_OP_convert (0x000015cf) "DW_ATE_unsigned_1", DW_OP_convert
> (0x000015d4) "DW_ATE_unsigned_8", DW_OP_stack_value)
> DW_AT_abstract_origin (0x00013984 "branch")
>
> Look at clang frontend, only the following types are encoded with
> unsigned dwarf type.
>
> case BuiltinType::UShort:
> case BuiltinType::UInt:
> case BuiltinType::UInt128:
> case BuiltinType::ULong:
> case BuiltinType::WChar_U:
> case BuiltinType::ULongLong:
> Encoding = llvm::dwarf::DW_ATE_unsigned;
> break;
>
>
> > not, can we try to come up with some extension that doesn't require
> > consumers to match magic names?
> >
You want me to upload mlx5_core.ko?
When looking with llvm-dwarf for DW_ATE_unsigned_160:
0x00d65616: DW_TAG_base_type
DW_AT_name ("DW_ATE_unsigned_160")
DW_AT_encoding (DW_ATE_unsigned)
DW_AT_byte_size (0x14)
If you need further information, please let me know.
Thanks.
- Sedat -
next prev parent reply other threads:[~2021-02-06 18:11 UTC|newest]
Thread overview: 64+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-04 22:07 ANNOUNCE: pahole v1.20 (gcc11 DWARF5's default, lots of ELF sections, BTF) Arnaldo Carvalho de Melo
2021-02-04 22:10 ` Sedat Dilek
2021-02-05 0:01 ` Andrii Nakryiko
2021-02-05 4:33 ` Arnaldo Carvalho de Melo
2021-02-05 7:39 ` Andrii Nakryiko
2021-02-05 9:33 ` Arnaldo Carvalho de Melo
2021-02-05 16:25 ` Arnaldo Carvalho de Melo
2021-02-05 22:11 ` Andrii Nakryiko
2021-02-05 23:55 ` Arnaldo Carvalho de Melo
2021-02-07 6:40 ` Andrii Nakryiko
2021-02-05 14:37 ` ERROR: INT DW_ATE_unsigned_1 Error emitting BTF type Sedat Dilek
2021-02-05 14:41 ` Sedat Dilek
2021-02-05 15:23 ` Sedat Dilek
2021-02-05 15:28 ` Arnaldo Carvalho de Melo
2021-02-05 15:40 ` Sedat Dilek
2021-02-05 17:48 ` Sedat Dilek
2021-02-05 18:53 ` Sedat Dilek
2021-02-05 19:06 ` Sedat Dilek
2021-02-05 19:10 ` Yonghong Song
2021-02-05 19:15 ` Sedat Dilek
2021-02-05 19:20 ` Yonghong Song
2021-02-05 19:24 ` Sedat Dilek
2021-02-05 19:44 ` Sedat Dilek
2021-02-05 19:21 ` Sedat Dilek
2021-02-05 19:30 ` Fāng-ruì Sòng
2021-02-05 19:38 ` Sedat Dilek
2021-02-05 19:24 ` Arnaldo Carvalho de Melo
2021-02-05 20:03 ` Yonghong Song
2021-02-05 20:31 ` Sedat Dilek
2021-02-05 21:54 ` Yonghong Song
2021-02-06 3:34 ` Sedat Dilek
2021-02-06 5:44 ` Sedat Dilek
2021-02-06 5:53 ` Sedat Dilek
2021-02-06 6:26 ` Sedat Dilek
2021-02-06 6:52 ` Sedat Dilek
2021-02-06 8:26 ` Yonghong Song
2021-02-06 8:32 ` Sedat Dilek
2021-02-06 9:32 ` Sedat Dilek
2021-02-06 9:37 ` Sedat Dilek
2021-02-06 9:48 ` Sedat Dilek
2021-02-06 10:16 ` Sedat Dilek
2021-02-06 10:23 ` Sedat Dilek
2021-02-06 11:27 ` Sedat Dilek
2021-02-06 12:54 ` Sedat Dilek
2021-02-06 16:24 ` Mark Wieelard
2021-02-06 17:53 ` Yonghong Song
2021-02-06 18:10 ` Sedat Dilek [this message]
2021-02-06 19:17 ` Yonghong Song
2021-02-06 19:22 ` Sedat Dilek
2021-02-06 19:28 ` Sedat Dilek
2021-02-06 19:32 ` Yonghong Song
2021-02-06 19:44 ` Sedat Dilek
2021-02-06 20:12 ` Yonghong Song
2021-02-06 20:46 ` Sedat Dilek
2021-02-06 7:26 ` Sedat Dilek
2021-02-05 21:10 ` Nick Desaulniers
2021-02-05 21:16 ` Sedat Dilek
2021-02-05 21:40 ` Nick Desaulniers
2021-02-05 21:42 ` Sedat Dilek
2021-02-08 2:44 ` ANNOUNCE: pahole v1.20 (gcc11 DWARF5's default, lots of ELF sections, BTF) Sedat Dilek
2021-02-08 12:32 ` Arnaldo Carvalho de Melo
2021-02-08 12:36 ` Sedat Dilek
2021-02-17 12:08 ` Domenico Andreoli
2021-02-17 12:48 ` Arnaldo Carvalho de Melo
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