On Thu, Feb 4, 2021 at 7:40 AM Nick Desaulniers <ndesaulniers@xxxxxxxxxx> wrote: > > 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 v7: > (Strictly commit message changes) > * Pick up Nathan's reviewed by tags for both patches. > * Add note about only modifying compiler dwarf info, not assembler dwarf > info, as per Nathan. > * Add link to Red Hat bug report and Chris' reported by on patch 2. > * Add more info from Jakub on patch 2 commit message. > * Reorder info about validating version, noting the tree is not "clean" > in the sense that parts mess up existing CFLAGS, or don't use > DEBUG_CFLAGS. I will not be adding such cleanups to this series. They > can be done AFTER. > * Update note about 2.35.2 (rather than include the full text Jakub > wrote on it in https://patchwork.kernel.org/project/linux-kbuild/patch/20201022012106.1875129-1-ndesaulniers@xxxxxxxxxx/#23727667). > * Add note that GCC 11 has changed the implicit default version. > I have intensively tested a lot of versions of this series and some other issues reported and got fixed. So my comments for followers: [ Download v8 with b4 ] link="https://lore.kernel.org/r/20210204064037.1281726-1-ndesaulniers@xxxxxxxxxx"; b4 -d am $link [ Pre-Patch before applying v8 ] "kbuild: Remove $(cc-option,-gdwarf-4) dependency from DEBUG_INFO_DWARF4" https://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild.git/commit/?h=kbuild&id=3f4d8ce271c7082be75bacbcbd2048aa78ce2b44 [ DEBUG_CFLAGS thread and fix ] https://marc.info/?t=161233893400006&r=1&w=2 https://marc.info/?l=linux-kbuild&m=161233892923723&w=2 Feel free to be more verbose and include links (to patches). I guess I need to test harder to get a Tested-by credit :-)? Thanks for v8, I will use it for some testing with BTF/pahole. - Sedat - > 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 >
