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Date:   Tue, 12 Jan 2021 16:32:32 -0800
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Subject: [PATCH v4 0/3] Kbuild: DWARF v5 support
From:   Nick Desaulniers <ndesaulniers@google.com>
To:     Masahiro Yamada <masahiroy@kernel.org>
Cc:     Nathan Chancellor <natechancellor@gmail.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Sedat Dilek <sedat.dilek@gmail.com>,
        linux-kernel@vger.kernel.org, clang-built-linux@googlegroups.com,
        linux-kbuild@vger.kernel.org, linux-arch@vger.kernel.org,
        Jakub Jelinek <jakub@redhat.com>,
        Fangrui Song <maskray@google.com>,
        Caroline Tice <cmtice@google.com>,
        Nick Clifton <nickc@redhat.com>,
        Nick Desaulniers <ndesaulniers@google.com>
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Precedence: bulk

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 from Masahiro and isn't DWARF v5 specific.
Patch 2 is a cleanup that lays the ground work and isn't DWARF
v5 specific.
Patch 3 implements Kconfig and Kbuild support for DWARFv5.

Changes from v3:

Changes as per Arvind:
* only add -Wa,-gdwarf-5 for (LLVM=1|CC=clang)+LLVM_IAS=0 builds.
* add -gdwarf-5 to Kconfig shell script.
* only run Kconfig shell script for Clang.

Apologies to Sedat and Nathan; I appreciate previous testing/review, but
I did no carry forward your Tested-by and Reviewed-by tags, as the
patches have changed too much IMO.

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.

Masahiro Yamada (1):
  Remove $(cc-option,-gdwarf-4) dependency from CONFIG_DEBUG_INFO_DWARF4

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                 | 41 +++++++++++++++++++++++++------
 scripts/test_dwarf5_support.sh    |  9 +++++++
 4 files changed, 58 insertions(+), 13 deletions(-)
 create mode 100755 scripts/test_dwarf5_support.sh

-- 
2.30.0.284.gd98b1dd5eaa7-goog