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 v6: * Reorder sections from linker script to match order from BFD's internal linker script. * Add .debug_names section, as per Fangrui. * Drop CONFIG_DEBUG_INFO_DWARF2. Patch 0001 becomes a menu with 1 choice. GCC's implicit default version of DWARF has been DWARF v4 since ~4.8. * Modify the test script to check for the presence of https://sourceware.org/bugzilla/show_bug.cgi?id=27195. * Drop the clang without integrated assembler block in 0002. Bumps the version requirement for GAS to 2.35.2, which isn't released yet (but should be released soon). Folks looking to test with clang but without the integrated assembler should fetch binutils-gdb, build it from source, add a symlink to binutils-gdb/gas/as-new to binutils-gdb/gas/as, then prefix binutils-gdb/gas/as to their $PATH when building the kernel. 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 | 6 +++--- include/asm-generic/vmlinux.lds.h | 7 +++++- lib/Kconfig.debug | 36 +++++++++++++++++++++++++------ scripts/test_dwarf5_support.sh | 8 +++++++ 4 files changed, 47 insertions(+), 10 deletions(-) create mode 100755 scripts/test_dwarf5_support.sh -- 2.30.0.365.g02bc693789-goog
