diff mbox series

Introduce CONFIG_DEBUG_INFO_AS_DWARF2 and CONFIG_DEBUG_INFO_AS_DWARF4

Message ID CA+icZUV85LS08Y2qJ-mheecCrzZmCTV4B5x9kh=BGCUzQVOKaA@mail.gmail.com (mailing list archive)
State New, archived
Headers show
Series Introduce CONFIG_DEBUG_INFO_AS_DWARF2 and CONFIG_DEBUG_INFO_AS_DWARF4 | expand

Commit Message

Sedat Dilek Aug. 16, 2020, 12:14 p.m. UTC
Hi Masahiro,

I wondered why my generated linux-image-db Debian packages were so big
when I use GCC toolchain instead of LLVM toolchain.

It turned out I mixed both...

   KBUILD_AFLAGS += -Wa,-gdwarf-2

...together with...

   DEBUG_CFLAGS += -gdwarf-4

...when CONFIG_DEBUG_INFO_DWARF4=y is set.

So I hacked up something like the following to prevent this:


NOTE: This is on top of Linux v5.8 vanilla.

NOTE-2: When building with LLVM toolchain v11.0.0-rc1+ and especially
with LLVM_IAS=1 (and LLVM=1) DWARF version 4 is a good choice.

For details see below links.

Thoughts?

Regards,
- Sedat -

[1] https://github.com/ClangBuiltLinux/linux/issues/1086
[2] https://github.com/ClangBuiltLinux/linux/issues/1086#issuecomment-674503335
[3] https://github.com/ClangBuiltLinux/linux/issues/1086#issuecomment-674517876

Comments

Sedat Dilek Aug. 26, 2020, 12:11 p.m. UTC | #1
On Sun, Aug 16, 2020 at 2:14 PM Sedat Dilek <sedat.dilek@gmail.com> wrote:
>
> Hi Masahiro,
>
> I wondered why my generated linux-image-db Debian packages were so big
> when I use GCC toolchain instead of LLVM toolchain.
>
> It turned out I mixed both...
>
>    KBUILD_AFLAGS += -Wa,-gdwarf-2
>
> ...together with...
>
>    DEBUG_CFLAGS += -gdwarf-4
>
> ...when CONFIG_DEBUG_INFO_DWARF4=y is set.
>
> So I hacked up something like the following to prevent this:
>
> diff --git a/Makefile b/Makefile
> index 24a4c1b97bb0..e7a8e47b0e34 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -815,7 +815,11 @@ DEBUG_CFLAGS       += -gsplit-dwarf
>  else
>  DEBUG_CFLAGS   += -g
>  endif
> +ifdef CONFIG_DEBUG_INFO_AS_DWARF2
>  KBUILD_AFLAGS  += -Wa,-gdwarf-2
> +else ifdef CONFIG_DEBUG_INFO_AS_DWARF4
> +KBUILD_AFLAGS  += -Wa,-gdwarf-4
> +endif
>  endif
>  ifdef CONFIG_DEBUG_INFO_DWARF4
>  DEBUG_CFLAGS   += -gdwarf-4
> diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
> index 9ad9210d70a1..9f11fc71462c 100644
> --- a/lib/Kconfig.debug
> +++ b/lib/Kconfig.debug
> @@ -257,10 +257,23 @@ config DEBUG_INFO_SPLIT
>           to know about the .dwo files and include them.
>           Incompatible with older versions of ccache.
>
> +config DEBUG_INFO_AS_DWARF2
> +       bool "Use DWARF-2 assembler option with debuginfo"
> +       depends on $(cc-option,-Wa$(comma)-gdwarf-2)
> +       help
> +         Set DWARF-2 assembler option with debuginfo
> +
> +config DEBUG_INFO_AS_DWARF4
> +       bool "Use DWARF-4 assembler option with debuginfo"
> +       depends on $(cc-option,-Wa$(comma)-gdwarf-4)
> +       help
> +         Set DWARF-4 assembler option with debuginfo
> +
>  config DEBUG_INFO_DWARF4
>         bool "Generate dwarf4 debuginfo"
>         depends on DEBUG_INFO
>         depends on $(cc-option,-gdwarf-4)
> +       select DEBUG_INFO_AS_DWARF4
>         help
>           Generate dwarf4 debug info. This requires recent versions
>           of gcc and gdb. It makes the debug information larger.
>
> NOTE: This is on top of Linux v5.8 vanilla.
>
> NOTE-2: When building with LLVM toolchain v11.0.0-rc1+ and especially
> with LLVM_IAS=1 (and LLVM=1) DWARF version 4 is a good choice.
>
> For details see below links.
>
> Thoughts?
>
> Regards,
> - Sedat -
>
> [1] https://github.com/ClangBuiltLinux/linux/issues/1086
> [2] https://github.com/ClangBuiltLinux/linux/issues/1086#issuecomment-674503335
> [3] https://github.com/ClangBuiltLinux/linux/issues/1086#issuecomment-674517876

[ CC Sami ]

Hi,

while playing with Clang-CFI I needed this patch to fix these warnings:

$ grep DWARF BROKEN_DWARF2-only-supports-one-section-per-compilation-unit.txt
arch/x86/crypto/twofish-avx-x86_64-asm_64.S:17:1: warning: DWARF2 only
supports one section per compilation unit
arch/x86/crypto/twofish-avx-x86_64-asm_64.S:22:1: warning: DWARF2 only
supports one section per compilation unit
arch/x86/crypto/serpent-avx-x86_64-asm_64.S:17:1: warning: DWARF2 only
supports one section per compilation unit
arch/x86/crypto/serpent-avx-x86_64-asm_64.S:21:1: warning: DWARF2 only
supports one section per compilation unit
arch/x86/crypto/serpent-avx2-asm_64.S:18:1: warning: DWARF2 only
supports one section per compilation unit
arch/x86/crypto/serpent-avx2-asm_64.S:23:1: warning: DWARF2 only
supports one section per compilation unit
arch/x86/crypto/serpent-avx2-asm_64.S:28:1: warning: DWARF2 only
supports one section per compilation unit
arch/x86/crypto/des3_ede-asm_64.S:534:1: warning: DWARF2 only supports
one section per compilation unit
arch/x86/crypto/camellia-aesni-avx-asm_64.S:577:1: warning: DWARF2
only supports one section per compilation unit
arch/x86/crypto/camellia-aesni-avx-asm_64.S:717:1: warning: DWARF2
only supports one section per compilation unit
<instantiation>:2:2: warning: DWARF2 only supports one section per
compilation unit
<instantiation>:8:2: warning: DWARF2 only supports one section per
compilation unit
<instantiation>:13:2: warning: DWARF2 only supports one section per
compilation unit
arch/x86/crypto/camellia-aesni-avx2-asm_64.S:610:1: warning: DWARF2
only supports one section per compilation unit
arch/x86/crypto/camellia-aesni-avx2-asm_64.S:618:1: warning: DWARF2
only supports one section per compilation unit
arch/x86/crypto/camellia-aesni-avx2-asm_64.S:625:1: warning: DWARF2
only supports one section per compilation unit
arch/x86/crypto/camellia-aesni-avx2-asm_64.S:754:1: warning: DWARF2
only supports one section per compilation unit
<instantiation>:2:2: warning: DWARF2 only supports one section per
compilation unit
<instantiation>:8:2: warning: DWARF2 only supports one section per
compilation unit
<instantiation>:13:2: warning: DWARF2 only supports one section per
compilation unit
arch/x86/crypto/cast5-avx-x86_64-asm_64.S:183:1: warning: DWARF2 only
supports one section per compilation unit
arch/x86/crypto/cast5-avx-x86_64-asm_64.S:187:1: warning: DWARF2 only
supports one section per compilation unit
arch/x86/crypto/cast5-avx-x86_64-asm_64.S:191:1: warning: DWARF2 only
supports one section per compilation unit
arch/x86/crypto/cast5-avx-x86_64-asm_64.S:196:1: warning: DWARF2 only
supports one section per compilation unit
arch/x86/crypto/cast5-avx-x86_64-asm_64.S:200:1: warning: DWARF2 only
supports one section per compilation unit
arch/x86/crypto/cast5-avx-x86_64-asm_64.S:204:1: warning: DWARF2 only
supports one section per compilation unit
arch/x86/crypto/cast6-avx-x86_64-asm_64.S:213:1: warning: DWARF2 only
supports one section per compilation unit
arch/x86/crypto/cast6-avx-x86_64-asm_64.S:232:1: warning: DWARF2 only
supports one section per compilation unit
arch/x86/crypto/cast6-avx-x86_64-asm_64.S:237:1: warning: DWARF2 only
supports one section per compilation unit
arch/x86/crypto/cast6-avx-x86_64-asm_64.S:242:1: warning: DWARF2 only
supports one section per compilation unit
arch/x86/crypto/aegis128-aesni-asm.S:27:1: warning: DWARF2 only
supports one section per compilation unit
arch/x86/crypto/aegis128-aesni-asm.S:36:1: warning: DWARF2 only
supports one section per compilation unit

Can you please review?

Thanks.

Regards,
- Sedat -

P.S.: With the help of Sami I can now build and boot into Linux-kernel
with Clang-CFI support enabled.

[1] https://github.com/samitolvanen/linux/commits/clang-cfi
Sedat Dilek Aug. 26, 2020, 2:36 p.m. UTC | #2
On Wed, Aug 26, 2020 at 2:11 PM Sedat Dilek <sedat.dilek@gmail.com> wrote:
>
> On Sun, Aug 16, 2020 at 2:14 PM Sedat Dilek <sedat.dilek@gmail.com> wrote:
> >
> > Hi Masahiro,
> >
> > I wondered why my generated linux-image-db Debian packages were so big
> > when I use GCC toolchain instead of LLVM toolchain.
> >
> > It turned out I mixed both...
> >
> >    KBUILD_AFLAGS += -Wa,-gdwarf-2
> >
> > ...together with...
> >
> >    DEBUG_CFLAGS += -gdwarf-4
> >
> > ...when CONFIG_DEBUG_INFO_DWARF4=y is set.
> >
> > So I hacked up something like the following to prevent this:
> >
> > diff --git a/Makefile b/Makefile
> > index 24a4c1b97bb0..e7a8e47b0e34 100644
> > --- a/Makefile
> > +++ b/Makefile
> > @@ -815,7 +815,11 @@ DEBUG_CFLAGS       += -gsplit-dwarf
> >  else
> >  DEBUG_CFLAGS   += -g
> >  endif
> > +ifdef CONFIG_DEBUG_INFO_AS_DWARF2
> >  KBUILD_AFLAGS  += -Wa,-gdwarf-2
> > +else ifdef CONFIG_DEBUG_INFO_AS_DWARF4
> > +KBUILD_AFLAGS  += -Wa,-gdwarf-4
> > +endif
> >  endif
> >  ifdef CONFIG_DEBUG_INFO_DWARF4
> >  DEBUG_CFLAGS   += -gdwarf-4
> > diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
> > index 9ad9210d70a1..9f11fc71462c 100644
> > --- a/lib/Kconfig.debug
> > +++ b/lib/Kconfig.debug
> > @@ -257,10 +257,23 @@ config DEBUG_INFO_SPLIT
> >           to know about the .dwo files and include them.
> >           Incompatible with older versions of ccache.
> >
> > +config DEBUG_INFO_AS_DWARF2
> > +       bool "Use DWARF-2 assembler option with debuginfo"
> > +       depends on $(cc-option,-Wa$(comma)-gdwarf-2)
> > +       help
> > +         Set DWARF-2 assembler option with debuginfo
> > +
> > +config DEBUG_INFO_AS_DWARF4
> > +       bool "Use DWARF-4 assembler option with debuginfo"
> > +       depends on $(cc-option,-Wa$(comma)-gdwarf-4)
> > +       help
> > +         Set DWARF-4 assembler option with debuginfo
> > +
> >  config DEBUG_INFO_DWARF4
> >         bool "Generate dwarf4 debuginfo"
> >         depends on DEBUG_INFO
> >         depends on $(cc-option,-gdwarf-4)
> > +       select DEBUG_INFO_AS_DWARF4
> >         help
> >           Generate dwarf4 debug info. This requires recent versions
> >           of gcc and gdb. It makes the debug information larger.
> >
> > NOTE: This is on top of Linux v5.8 vanilla.
> >
> > NOTE-2: When building with LLVM toolchain v11.0.0-rc1+ and especially
> > with LLVM_IAS=1 (and LLVM=1) DWARF version 4 is a good choice.
> >
> > For details see below links.
> >
> > Thoughts?
> >
> > Regards,
> > - Sedat -
> >
> > [1] https://github.com/ClangBuiltLinux/linux/issues/1086
> > [2] https://github.com/ClangBuiltLinux/linux/issues/1086#issuecomment-674503335
> > [3] https://github.com/ClangBuiltLinux/linux/issues/1086#issuecomment-674517876
>
> [ CC Sami ]
>
> Hi,
>
> while playing with Clang-CFI I needed this patch to fix these warnings:
>
> $ grep DWARF BROKEN_DWARF2-only-supports-one-section-per-compilation-unit.txt
> arch/x86/crypto/twofish-avx-x86_64-asm_64.S:17:1: warning: DWARF2 only
> supports one section per compilation unit
> arch/x86/crypto/twofish-avx-x86_64-asm_64.S:22:1: warning: DWARF2 only
> supports one section per compilation unit
> arch/x86/crypto/serpent-avx-x86_64-asm_64.S:17:1: warning: DWARF2 only
> supports one section per compilation unit
> arch/x86/crypto/serpent-avx-x86_64-asm_64.S:21:1: warning: DWARF2 only
> supports one section per compilation unit
> arch/x86/crypto/serpent-avx2-asm_64.S:18:1: warning: DWARF2 only
> supports one section per compilation unit
> arch/x86/crypto/serpent-avx2-asm_64.S:23:1: warning: DWARF2 only
> supports one section per compilation unit
> arch/x86/crypto/serpent-avx2-asm_64.S:28:1: warning: DWARF2 only
> supports one section per compilation unit
> arch/x86/crypto/des3_ede-asm_64.S:534:1: warning: DWARF2 only supports
> one section per compilation unit
> arch/x86/crypto/camellia-aesni-avx-asm_64.S:577:1: warning: DWARF2
> only supports one section per compilation unit
> arch/x86/crypto/camellia-aesni-avx-asm_64.S:717:1: warning: DWARF2
> only supports one section per compilation unit
> <instantiation>:2:2: warning: DWARF2 only supports one section per
> compilation unit
> <instantiation>:8:2: warning: DWARF2 only supports one section per
> compilation unit
> <instantiation>:13:2: warning: DWARF2 only supports one section per
> compilation unit
> arch/x86/crypto/camellia-aesni-avx2-asm_64.S:610:1: warning: DWARF2
> only supports one section per compilation unit
> arch/x86/crypto/camellia-aesni-avx2-asm_64.S:618:1: warning: DWARF2
> only supports one section per compilation unit
> arch/x86/crypto/camellia-aesni-avx2-asm_64.S:625:1: warning: DWARF2
> only supports one section per compilation unit
> arch/x86/crypto/camellia-aesni-avx2-asm_64.S:754:1: warning: DWARF2
> only supports one section per compilation unit
> <instantiation>:2:2: warning: DWARF2 only supports one section per
> compilation unit
> <instantiation>:8:2: warning: DWARF2 only supports one section per
> compilation unit
> <instantiation>:13:2: warning: DWARF2 only supports one section per
> compilation unit
> arch/x86/crypto/cast5-avx-x86_64-asm_64.S:183:1: warning: DWARF2 only
> supports one section per compilation unit
> arch/x86/crypto/cast5-avx-x86_64-asm_64.S:187:1: warning: DWARF2 only
> supports one section per compilation unit
> arch/x86/crypto/cast5-avx-x86_64-asm_64.S:191:1: warning: DWARF2 only
> supports one section per compilation unit
> arch/x86/crypto/cast5-avx-x86_64-asm_64.S:196:1: warning: DWARF2 only
> supports one section per compilation unit
> arch/x86/crypto/cast5-avx-x86_64-asm_64.S:200:1: warning: DWARF2 only
> supports one section per compilation unit
> arch/x86/crypto/cast5-avx-x86_64-asm_64.S:204:1: warning: DWARF2 only
> supports one section per compilation unit
> arch/x86/crypto/cast6-avx-x86_64-asm_64.S:213:1: warning: DWARF2 only
> supports one section per compilation unit
> arch/x86/crypto/cast6-avx-x86_64-asm_64.S:232:1: warning: DWARF2 only
> supports one section per compilation unit
> arch/x86/crypto/cast6-avx-x86_64-asm_64.S:237:1: warning: DWARF2 only
> supports one section per compilation unit
> arch/x86/crypto/cast6-avx-x86_64-asm_64.S:242:1: warning: DWARF2 only
> supports one section per compilation unit
> arch/x86/crypto/aegis128-aesni-asm.S:27:1: warning: DWARF2 only
> supports one section per compilation unit
> arch/x86/crypto/aegis128-aesni-asm.S:36:1: warning: DWARF2 only
> supports one section per compilation unit
>
> Can you please review?
>
> Thanks.
>
> Regards,
> - Sedat -
>
> P.S.: With the help of Sami I can now build and boot into Linux-kernel
> with Clang-CFI support enabled.
>
> [1] https://github.com/samitolvanen/linux/commits/clang-cfi

Some more informations to clarify this is really needed.

I switched over to DWARF version 4 when dealing with Clang-IAS
(integrated assembler).
And saw similar problems.

This was always with...

CONFIG_DEBUG_INFO_DWARF4=y

There are 156 places here on x86 64bit...

[ Clang-CFI ]

$ grep '\-Wa,-gdwarf-4' build-log_5.9.0-rc2-5-amd64-llvm11-cfi.txt | wc -l
156

[ Clang-LTO ]

$ grep '\-Wa,-gdwarf-4' build-log_5.9.0-rc2-6-amd64-clang-lto.txt | wc -l
156

- Sedat -
Sedat Dilek Aug. 26, 2020, 4:05 p.m. UTC | #3
On Wed, Aug 26, 2020 at 4:36 PM Sedat Dilek <sedat.dilek@gmail.com> wrote:
>
> On Wed, Aug 26, 2020 at 2:11 PM Sedat Dilek <sedat.dilek@gmail.com> wrote:
> >
> > On Sun, Aug 16, 2020 at 2:14 PM Sedat Dilek <sedat.dilek@gmail.com> wrote:
> > >
> > > Hi Masahiro,
> > >
> > > I wondered why my generated linux-image-db Debian packages were so big
> > > when I use GCC toolchain instead of LLVM toolchain.
> > >
> > > It turned out I mixed both...
> > >
> > >    KBUILD_AFLAGS += -Wa,-gdwarf-2
> > >
> > > ...together with...
> > >
> > >    DEBUG_CFLAGS += -gdwarf-4
> > >
> > > ...when CONFIG_DEBUG_INFO_DWARF4=y is set.
> > >
> > > So I hacked up something like the following to prevent this:
> > >
> > > diff --git a/Makefile b/Makefile
> > > index 24a4c1b97bb0..e7a8e47b0e34 100644
> > > --- a/Makefile
> > > +++ b/Makefile
> > > @@ -815,7 +815,11 @@ DEBUG_CFLAGS       += -gsplit-dwarf
> > >  else
> > >  DEBUG_CFLAGS   += -g
> > >  endif
> > > +ifdef CONFIG_DEBUG_INFO_AS_DWARF2
> > >  KBUILD_AFLAGS  += -Wa,-gdwarf-2
> > > +else ifdef CONFIG_DEBUG_INFO_AS_DWARF4
> > > +KBUILD_AFLAGS  += -Wa,-gdwarf-4
> > > +endif
> > >  endif
> > >  ifdef CONFIG_DEBUG_INFO_DWARF4
> > >  DEBUG_CFLAGS   += -gdwarf-4
> > > diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
> > > index 9ad9210d70a1..9f11fc71462c 100644
> > > --- a/lib/Kconfig.debug
> > > +++ b/lib/Kconfig.debug
> > > @@ -257,10 +257,23 @@ config DEBUG_INFO_SPLIT
> > >           to know about the .dwo files and include them.
> > >           Incompatible with older versions of ccache.
> > >
> > > +config DEBUG_INFO_AS_DWARF2
> > > +       bool "Use DWARF-2 assembler option with debuginfo"
> > > +       depends on $(cc-option,-Wa$(comma)-gdwarf-2)
> > > +       help
> > > +         Set DWARF-2 assembler option with debuginfo
> > > +
> > > +config DEBUG_INFO_AS_DWARF4
> > > +       bool "Use DWARF-4 assembler option with debuginfo"
> > > +       depends on $(cc-option,-Wa$(comma)-gdwarf-4)
> > > +       help
> > > +         Set DWARF-4 assembler option with debuginfo
> > > +
> > >  config DEBUG_INFO_DWARF4
> > >         bool "Generate dwarf4 debuginfo"
> > >         depends on DEBUG_INFO
> > >         depends on $(cc-option,-gdwarf-4)
> > > +       select DEBUG_INFO_AS_DWARF4
> > >         help
> > >           Generate dwarf4 debug info. This requires recent versions
> > >           of gcc and gdb. It makes the debug information larger.
> > >
> > > NOTE: This is on top of Linux v5.8 vanilla.
> > >
> > > NOTE-2: When building with LLVM toolchain v11.0.0-rc1+ and especially
> > > with LLVM_IAS=1 (and LLVM=1) DWARF version 4 is a good choice.
> > >
> > > For details see below links.
> > >
> > > Thoughts?
> > >
> > > Regards,
> > > - Sedat -
> > >
> > > [1] https://github.com/ClangBuiltLinux/linux/issues/1086
> > > [2] https://github.com/ClangBuiltLinux/linux/issues/1086#issuecomment-674503335
> > > [3] https://github.com/ClangBuiltLinux/linux/issues/1086#issuecomment-674517876
> >
> > [ CC Sami ]
> >
> > Hi,
> >
> > while playing with Clang-CFI I needed this patch to fix these warnings:
> >
> > $ grep DWARF BROKEN_DWARF2-only-supports-one-section-per-compilation-unit.txt
> > arch/x86/crypto/twofish-avx-x86_64-asm_64.S:17:1: warning: DWARF2 only
> > supports one section per compilation unit
> > arch/x86/crypto/twofish-avx-x86_64-asm_64.S:22:1: warning: DWARF2 only
> > supports one section per compilation unit
> > arch/x86/crypto/serpent-avx-x86_64-asm_64.S:17:1: warning: DWARF2 only
> > supports one section per compilation unit
> > arch/x86/crypto/serpent-avx-x86_64-asm_64.S:21:1: warning: DWARF2 only
> > supports one section per compilation unit
> > arch/x86/crypto/serpent-avx2-asm_64.S:18:1: warning: DWARF2 only
> > supports one section per compilation unit
> > arch/x86/crypto/serpent-avx2-asm_64.S:23:1: warning: DWARF2 only
> > supports one section per compilation unit
> > arch/x86/crypto/serpent-avx2-asm_64.S:28:1: warning: DWARF2 only
> > supports one section per compilation unit
> > arch/x86/crypto/des3_ede-asm_64.S:534:1: warning: DWARF2 only supports
> > one section per compilation unit
> > arch/x86/crypto/camellia-aesni-avx-asm_64.S:577:1: warning: DWARF2
> > only supports one section per compilation unit
> > arch/x86/crypto/camellia-aesni-avx-asm_64.S:717:1: warning: DWARF2
> > only supports one section per compilation unit
> > <instantiation>:2:2: warning: DWARF2 only supports one section per
> > compilation unit
> > <instantiation>:8:2: warning: DWARF2 only supports one section per
> > compilation unit
> > <instantiation>:13:2: warning: DWARF2 only supports one section per
> > compilation unit
> > arch/x86/crypto/camellia-aesni-avx2-asm_64.S:610:1: warning: DWARF2
> > only supports one section per compilation unit
> > arch/x86/crypto/camellia-aesni-avx2-asm_64.S:618:1: warning: DWARF2
> > only supports one section per compilation unit
> > arch/x86/crypto/camellia-aesni-avx2-asm_64.S:625:1: warning: DWARF2
> > only supports one section per compilation unit
> > arch/x86/crypto/camellia-aesni-avx2-asm_64.S:754:1: warning: DWARF2
> > only supports one section per compilation unit
> > <instantiation>:2:2: warning: DWARF2 only supports one section per
> > compilation unit
> > <instantiation>:8:2: warning: DWARF2 only supports one section per
> > compilation unit
> > <instantiation>:13:2: warning: DWARF2 only supports one section per
> > compilation unit
> > arch/x86/crypto/cast5-avx-x86_64-asm_64.S:183:1: warning: DWARF2 only
> > supports one section per compilation unit
> > arch/x86/crypto/cast5-avx-x86_64-asm_64.S:187:1: warning: DWARF2 only
> > supports one section per compilation unit
> > arch/x86/crypto/cast5-avx-x86_64-asm_64.S:191:1: warning: DWARF2 only
> > supports one section per compilation unit
> > arch/x86/crypto/cast5-avx-x86_64-asm_64.S:196:1: warning: DWARF2 only
> > supports one section per compilation unit
> > arch/x86/crypto/cast5-avx-x86_64-asm_64.S:200:1: warning: DWARF2 only
> > supports one section per compilation unit
> > arch/x86/crypto/cast5-avx-x86_64-asm_64.S:204:1: warning: DWARF2 only
> > supports one section per compilation unit
> > arch/x86/crypto/cast6-avx-x86_64-asm_64.S:213:1: warning: DWARF2 only
> > supports one section per compilation unit
> > arch/x86/crypto/cast6-avx-x86_64-asm_64.S:232:1: warning: DWARF2 only
> > supports one section per compilation unit
> > arch/x86/crypto/cast6-avx-x86_64-asm_64.S:237:1: warning: DWARF2 only
> > supports one section per compilation unit
> > arch/x86/crypto/cast6-avx-x86_64-asm_64.S:242:1: warning: DWARF2 only
> > supports one section per compilation unit
> > arch/x86/crypto/aegis128-aesni-asm.S:27:1: warning: DWARF2 only
> > supports one section per compilation unit
> > arch/x86/crypto/aegis128-aesni-asm.S:36:1: warning: DWARF2 only
> > supports one section per compilation unit
> >
> > Can you please review?
> >
> > Thanks.
> >
> > Regards,
> > - Sedat -
> >
> > P.S.: With the help of Sami I can now build and boot into Linux-kernel
> > with Clang-CFI support enabled.
> >
> > [1] https://github.com/samitolvanen/linux/commits/clang-cfi
>
> Some more informations to clarify this is really needed.
>
> I switched over to DWARF version 4 when dealing with Clang-IAS
> (integrated assembler).
> And saw similar problems.
>
> This was always with...
>
> CONFIG_DEBUG_INFO_DWARF4=y
>
> There are 156 places here on x86 64bit...
>
> [ Clang-CFI ]
>
> $ grep '\-Wa,-gdwarf-4' build-log_5.9.0-rc2-5-amd64-llvm11-cfi.txt | wc -l
> 156
>
> [ Clang-LTO ]
>
> $ grep '\-Wa,-gdwarf-4' build-log_5.9.0-rc2-6-amd64-clang-lto.txt | wc -l
> 156
>

Hi Masahiro,

I would send a proper patch with all related information when you
agree with the handling of CONFIG_DEBUG_INFO_AS_DWARF{2,4}.

Just as note:
I tested this also with GNU/ld (BFD) version 2.35 with preliminary
DWARF4 support.

Thanks.

Regards,
- Sedat -
diff mbox series

Patch

diff --git a/Makefile b/Makefile
index 24a4c1b97bb0..e7a8e47b0e34 100644
--- a/Makefile
+++ b/Makefile
@@ -815,7 +815,11 @@  DEBUG_CFLAGS       += -gsplit-dwarf
 else
 DEBUG_CFLAGS   += -g
 endif
+ifdef CONFIG_DEBUG_INFO_AS_DWARF2
 KBUILD_AFLAGS  += -Wa,-gdwarf-2
+else ifdef CONFIG_DEBUG_INFO_AS_DWARF4
+KBUILD_AFLAGS  += -Wa,-gdwarf-4
+endif
 endif
 ifdef CONFIG_DEBUG_INFO_DWARF4
 DEBUG_CFLAGS   += -gdwarf-4
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 9ad9210d70a1..9f11fc71462c 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -257,10 +257,23 @@  config DEBUG_INFO_SPLIT
          to know about the .dwo files and include them.
          Incompatible with older versions of ccache.

+config DEBUG_INFO_AS_DWARF2
+       bool "Use DWARF-2 assembler option with debuginfo"
+       depends on $(cc-option,-Wa$(comma)-gdwarf-2)
+       help
+         Set DWARF-2 assembler option with debuginfo
+
+config DEBUG_INFO_AS_DWARF4
+       bool "Use DWARF-4 assembler option with debuginfo"
+       depends on $(cc-option,-Wa$(comma)-gdwarf-4)
+       help
+         Set DWARF-4 assembler option with debuginfo
+
 config DEBUG_INFO_DWARF4
        bool "Generate dwarf4 debuginfo"
        depends on DEBUG_INFO
        depends on $(cc-option,-gdwarf-4)
+       select DEBUG_INFO_AS_DWARF4
        help
          Generate dwarf4 debug info. This requires recent versions
          of gcc and gdb. It makes the debug information larger.