DWARF v5 is the latest standard of the DWARF debug info format. DWARF5 wins significantly in terms of size and especially so 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 v5: * Drop previous patch 1, it has been accepted into kbuild: https://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild.git/commit/?h=kbuild&id=3f4d8ce271c7082be75bacbcbd2048aa78ce2b44 * Trying to set -Wa,-gdwarf-4 in the earlier patch was the source of additional complexity. Drop it that part of the patch. We can revisit clang without the integrated assembler setting -Wa,-gdwarf-4 later. That is a separate problem from generally supporting DWARF v5. * Rework the final patch for clang without the integrated assembler. -Wa,-gdwarf-5 is required for DWARF5 in that case otherwise GAS will not accept the assembler directives clang produces from C code when generating asm. Changes from v4: * drop set -e from script as per Nathan. * add dependency on !CONFIG_DEBUG_INFO_BTF for DWARF v5 as per Sedat. * Move LLVM_IAS=1 complexity from patch 2 to patch 3 as per Arvind and Masahiro. Sorry it took me a few tries to understand the point (I might still not), but it looks much cleaner this way. Sorry Nathan, I did not carry forward your previous reviews as a result, but I would appreciate if you could look again. * Add Nathan's reviewed by tag to patch 1. * Reword commit message for patch 3 to mention LLVM_IAS=1 and -gdwarf-5 binutils addition later, and BTF issue. * I still happen to see a pahole related error spew for the combination of: * LLVM=1 * LLVM_IAS=1 * CONFIG_DEBUG_INFO_DWARF4 * CONFIG_DEBUG_INFO_BTF Though they're non-fatal to the build. I'm not sure yet why removing any one of the above prevents the warning spew. Maybe we'll need a v6. 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. Nick Desaulniers (2): Kbuild: make DWARF version a choice Kbuild: implement support for DWARF v5 Makefile | 16 ++++++++++-- include/asm-generic/vmlinux.lds.h | 6 ++++- lib/Kconfig.debug | 41 ++++++++++++++++++++++++++----- scripts/test_dwarf5_support.sh | 8 ++++++ 4 files changed, 62 insertions(+), 9 deletions(-) create mode 100755 scripts/test_dwarf5_support.sh -- 2.30.0.365.g02bc693789-goog
