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SubjectRe: [PATCH v3 0/2] Kbuild: DWARF v5 support
On Sun, Dec 27, 2020 at 7:47 PM Sedat Dilek <sedat.dilek@gmail.com> wrote:
>
> On Fri, Dec 4, 2020 at 2:13 AM 'Nick Desaulniers' via Clang Built
> Linux <clang-built-linux@googlegroups.com> wrote:
> >
> > sigh...I ran a broken script to send the series which doesn't cc folks properly.
> > + lkml, linux-kbuild
> > (Might just resend, properly)
> >
> > On Thu, Dec 3, 2020 at 5:11 PM Nick Desaulniers <ndesaulniers@google.com> wrote:
> > >
> > > DWARF v5 is the latest standard of the DWARF debug info format.
> > >
> > > DWARF5 wins significantly in terms of size when mixed with compression
> > > (CONFIG_DEBUG_INFO_COMPRESSED).
> > >
> > > Link: http://www.dwarfstd.org/doc/DWARF5.pdf
> > >
> > > Patch 1 is a cleanup that lays the ground work and isn't DWARF
> > > v5 specific.
> > > Patch 2 implements Kconfig and Kbuild support for DWARFv5.
> > >
> > > Changes from v2:
> > > * Drop two of the earlier patches that have been accepted already.
> > > * Add measurements with GCC 10.2 to commit message.
> > > * Update help text as per Arvind with help from Caroline.
> > > * Improve case/wording between DWARF Versions as per Masahiro.
> > >
> > > Changes from the RFC:
> > > * split patch in 3 patch series, include Fangrui's patch, too.
> > > * prefer `DWARF vX` format, as per Fangrui.
> > > * use spaces between assignment in Makefile as per Masahiro.
> > > * simplify setting dwarf-version-y as per Masahiro.
> > > * indent `prompt` in Kconfig change as per Masahiro.
> > > * remove explicit default in Kconfig as per Masahiro.
> > > * add comments to test_dwarf5_support.sh.
> > > * change echo in test_dwarf5_support.sh as per Masahiro.
> > > * remove -u from test_dwarf5_support.sh as per Masahiro.
> > > * add a -gdwarf-5 cc-option check to Kconfig as per Jakub.
> > >
>
> I have tested v3 on top of Linux v5.10.3 on Debian/testing AMD64.
>
> Numbers talk - bullshit walks. [ Linus Torvalds ]
>
> [ 5.10.3-1-amd64-gcc10-bfd ]
>
> GNU-toolchain: GCC v10.2.1 and GNU/ld BFD v2.35.1
>
> 503096 vmlinux
> 6864 vmlinux.compressed
> 580104 vmlinux.o
>
> 701856 linux-image-5.10.3-1-amd64-gcc10-bfd-dbg_5.10.3-1~bullseye+dileks1_amd64.deb
>
> [ 5.10.3-1-amd64-clang-ias ]
>
> LLVM-toolchain: Clang and LLD v11.0.1-rc2
>
> 358424 vmlinux
> 7032 vmlinux.compressed
> 353788 vmlinux.o
>
> 508336 linux-image-5.10.3-1-amd64-clang-ias-dbg_5.10.3-1~bullseye+dileks1_amd64.deb
>
> [ 5.10.3-1-amd64-gcc10-bfd ]
>
> $ llvm-dwarfdump-11 vmlinux.o | head -15
> error: vmlinux.o: file format elf64-x86-64
>
> .debug_info contents:
> decoding address ranges: invalid range list offset 0x265
> 0x00000000: Compile Unit: length = 0x0000001f, format = DWARF32,
> version = 0x0005, unit_type = DW_UT_compile, abbr_offset = 0x0000,
> addr_size = 0x08 (next unit at 0x00
> 000023)
>
> 0x0000000c: DW_TAG_compile_unit
> DW_AT_stmt_list (0x00000000)
> DW_AT_ranges (0x0000000c
> [0x0000000000000000, 0x000000000000021c)
> [0x0000000000000000, 0x000000000000019e)
> [0x0000000000000000, 0x0000000000002000))
> DW_AT_name ("head_64.S")
> DW_AT_comp_dir ("/home/dileks/src/linux-kernel/git")
> DW_AT_producer ("GNU AS 2.35.1")
> DW_AT_language (DW_LANG_Mips_Assembler)
>
> [ 5.10.3-1-amd64-clang-ias ]
>
> $ llvm-dwarfdump-11 vmlinux.o | head -15
> vmlinux.o: file format elf64-x86-64
>
> .debug_info contents:
> 0x00000000: Compile Unit: length = 0x00000377, format = DWARF32,
> version = 0x0005, unit_type = DW_UT_compile, abbr_offset = 0x0000,
> addr_size = 0x08 (next unit at 0x00
> 00037b)
>
> 0x0000000c: DW_TAG_compile_unit
> DW_AT_stmt_list (0x00000000)
> DW_AT_ranges (0x0000000c
> [0x0000000000000000, 0x0000000000002000)
> [0x0000000000000000, 0x000000000000021c)
> [0x0000000000000000, 0x000000000000019e))
> DW_AT_name ("arch/x86/kernel/head_64.S")
> DW_AT_comp_dir ("/home/dileks/src/linux-kernel/git")
> DW_AT_producer ("Debian clang version 11.0.1-+rc2-1")
> DW_AT_language (DW_LANG_Mips_Assembler)
>

Some more numbers with Linux v5.11-rc1 and identical GNU and LLVM toolchains.

[ 5.11.0-rc1-1-amd64-gcc10-bfd ]

492 vmlinux
7 vmlinux.compressed
567 vmlinux.o
685 linux-image-5.11.0-rc1-1-amd64-gcc10-bfd-dbg_5.11.0~rc1-1~bullseye+dileks1_amd64.deb

[ 5.11.0-rc1-2-amd64-clang-ias ]

350 vmlinux
7 vmlinux.compressed
345 vmlinux.o
495 linux-image-5.11.0-rc1-2-amd64-clang-ias-dbg_5.11.0~rc1-2~bullseye+dileks1_amd64.deb

- Sedat -

> Attached are my kernel config files.
>
> Feel free to add my:
>
> Tested-by: Sedat Dilek <sedat.dilek@gmail.com>
>
> - sed@ -
>
> > > Nick Desaulniers (2):
> > > Kbuild: make DWARF version a choice
> > > Kbuild: implement support for DWARF v5
> > >
> > > Makefile | 15 +++++++------
> > > include/asm-generic/vmlinux.lds.h | 6 +++++-
> > > lib/Kconfig.debug | 35 ++++++++++++++++++++++++++-----
> > > scripts/test_dwarf5_support.sh | 9 ++++++++
> > > 4 files changed, 53 insertions(+), 12 deletions(-)
> > > create mode 100755 scripts/test_dwarf5_support.sh
> > >
> > > --
> > > 2.29.2.576.ga3fc446d84-goog
> > >
> >
> >
> > --
> > Thanks,
> > ~Nick Desaulniers
> >
> > --
> > You received this message because you are subscribed to the Google Groups "Clang Built Linux" group.
> > To unsubscribe from this group and stop receiving emails from it, send an email to clang-built-linux+unsubscribe@googlegroups.com.
> > To view this discussion on the web visit https://groups.google.com/d/msgid/clang-built-linux/CAKwvOdkZEiHK01OD420USb0j%3DF0LcrnRbauv9Yw26tu-GRbYkg%40mail.gmail.com.

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