On Tue, Apr 6, 2021 at 11:42 PM Alexander Lobakin <alobakin@xxxxx> wrote: > > On Friday, 2 April 2021, 18:09, Sami > Tolvanen <samitolvanen@xxxxxxxxxx> wrote: > > > On Fri, Apr 2, 2021 at 5:40 AM Alexander Lobakin alobakin@xxxxx wrote: > > > > > When building with CONFIG_LD_DEAD_CODE_DATA_ELIMINATION, > > > -fdata-sections and -ffunction-sections are being enabled by the > > > top-level Makefile, and module section merging is also needed. > > > Expand the ifdef (and the comment block) to cover that case too. > > > Fixes: 6a3193cdd5e5 ("kbuild: lto: Merge module sections if and only if CONFIG_LTO_CLANG is enabled") Did you test this patch before submission? See the top Makefile closely: ifdef CONFIG_LD_DEAD_CODE_DATA_ELIMINATION KBUILD_CFLAGS_KERNEL += -ffunction-sections -fdata-sections LDFLAGS_vmlinux += --gc-sections endif -ffunction-sections -fdata-sections are passed to only built-in objects, but not to module objects in the first place. KBUILD_CFLAGS_KERNEL is only passed to built-in objects. The situation you claimed never happens. > > Wouldn't this trigger the ld.bfd bug described in the commit message > > when LD_DEAD_CODE_DATA_ELIMINATION is enabled? LTO_CLANG always uses > > LLD, so it won't have this issue. > > LD_DEAD_CODE_DATA_ELIMINATION is marked > “EXPERIMENTAL“ in the config prompt, and > arches have to opt-in > HAS_LD_DEAD_CODE_DATA_ELIMINATION to give > an access to it (only a few does). This > should be relatively safe. > > > Sami > > Thanks, > Al -- Best Regards Masahiro Yamada