On Thu, Mar 31, 2022 at 10:45 AM Masami Hiramatsu <mhiramat@xxxxxxxxxx> wrote: > > Hi Nick, > > On Wed, 30 Mar 2022 11:04:50 -0700 > Nick Desaulniers <ndesaulniers@xxxxxxxxxx> wrote: > > > On Mon, Mar 28, 2022 at 7:29 AM Masami Hiramatsu <mhiramat@xxxxxxxxxx> wrote: > > > > > > KNOWN ISSUE: > > > > > > According to the report from Padmanabha[3] and my analysis [4], the embedded > > > bootconfig data may not be updated if you do incremental build the kernel > > > with CONFIG_LTO_CLANG_THIN. > > > > > > [3] https://lore.kernel.org/all/20220321183500.GA4065@pswork/T/#u > > > [4] https://lore.kernel.org/all/20220327115526.cc4b0ff55fc53c97683c3e4d@xxxxxxxxxx/ > > > > > > This seems like clang's LTO Thin mode issue. It may not detect the inline > > > asm depends on external files. > > > > > > I think the possible workaround is to split the inline asm which includes > > > '.incbin' directive into an asm file. But this should be done in another > > > seires because there are other features which uses '.incbin'. (e.g. > > > /proc/config.gz) > > > > Hi Masami, > > I saw Padmanabha's report (thanks for the report); sorry for not > > responding sooner, I've been traveling recently for a funeral. > > Oh, sorry about that. I think this is not so hurry. > > > > > Any chance we can use > > > > CFLAGS_REMOVE_<file>.o := $(CC_FLAGS_LTO) > > > > a la > > commit d2dcd3e37475 ("x86, cpu: disable LTO for cpu.c") > > Hm, this looks good to me. Let me confirm that works. > (Does this mean the bootconfig.o will be compiled to elf binary?) Why are you using ".incbin" in the C file in the first place? You might have mimicked kernel/configs.c but there was a reason; kernel/configs.c can be a module, but we cannot put MODULE_LICENSE() in *.S file. (commit 13610aa908dcfce77135bb799c0a10d0172da6ba) In this case, CONFIG_EMBED_BOOT_CONFIG is a bool option. Why don't you simply move the asm() part to a separate bootconfig-data.S ? Clang lto flags are only passed to *.c files, so we do not need to be worried about .incbin in *.S files. Then, Makefile will be even cleaner (no ifeq-block) lib-$(CONFIG_BOOT_CONFIG) += bootconfig.o obj-$(CONFIG_EMBED_BOOT_CONFIG) += bootconfig-data.o $(obj)/bootconfig-data.o: $(obj)/default.bconf targets += default.bconf filechk_defbconf = cat $(or $(real-prereqs), /dev/null) $(obj)/default.bconf: $(CONFIG_EMBED_BOOT_CONFIG_FILE) FORCE $(call filechk,defbconf) BTW, why lib-$(CONFIG_BOOT_CONFIG), instead of obj-$(CONFIG_BOOT_CONFIG) ? > > > > > with a comment linking to > > https://github.com/ClangBuiltLinux/linux/issues/1618 > > Thanks for reporting! > > > > > for the Translation Units using .incbin, until we have had more time > > to triage+fix? > > Yes. For this series, I can update with above one, but it doesn't cover the > other parts. And since this issue is independent from the bootconfig, > I think we need a wider patch series to mitigate this issue on config.gz > (and other .incbin users) too. > > Thank you, > > > > > -- > > Thanks, > > ~Nick Desaulniers > > > -- > Masami Hiramatsu <mhiramat@xxxxxxxxxx> -- Best Regards Masahiro Yamada
