Re: [PATCH v2 4/4] x86: Get rid of Makefile.postlink

Masahiro Yamada
2025-03-13T02:09:05Z

On Tue, Mar 11, 2025 at 8:06 PM Ard Biesheuvel <ardb+git@google.com> wrote:
>
> From: Ard Biesheuvel <ardb@kernel.org>
>
> Instead of generating the vmlinux.relocs file (needed by the
> decompressor build to construct the KASLR relocation tables) as a
> vmlinux postlink step, which is dubious because it depends on data that
> is stripped from vmlinux before the build completes, generate it from
> vmlinux.unstripped, which has been introduced specifically for this
> purpose.
>
> This ensures that each artifact is rebuilt as needed, rather than as a
> side effect of another build rule.
>
> This effectively reverts commit
>
> 9d9173e9ceb6 ("x86/build: Avoid relocation information in final vmlinux")
>
> Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
> ---
> arch/x86/Makefile.postlink | 38 --------------------
> arch/x86/boot/compressed/Makefile | 9 +++--
> 2 files changed, 6 insertions(+), 41 deletions(-)
>
> diff --git a/arch/x86/Makefile.postlink b/arch/x86/Makefile.postlink
> deleted file mode 100644
> index 445fce66630f..000000000000
> --- a/arch/x86/Makefile.postlink
> +++ /dev/null
> @@ -1,38 +0,0 @@
> -# SPDX-License-Identifier: GPL-2.0
> -# ===========================================================================
> -# Post-link x86 pass
> -# ===========================================================================
> -#
> -# 1. Separate relocations from vmlinux into vmlinux.relocs.
> -# 2. Strip relocations from vmlinux.
> -
> -PHONY := __archpost
> -__archpost:
> -
> --include include/config/auto.conf
> -include $(srctree)/scripts/Kbuild.include
> -
> -CMD_RELOCS = arch/x86/tools/relocs
> -OUT_RELOCS = arch/x86/boot/compressed
> -quiet_cmd_relocs = RELOCS $(OUT_RELOCS)/vmlinux.relocs
> - cmd_relocs = \
> - mkdir -p $(OUT_RELOCS); \
> - $(CMD_RELOCS) $@ > $(OUT_RELOCS)/vmlinux.relocs; \
> - $(CMD_RELOCS) --abs-relocs $@
> -
> -# `@true` prevents complaint when there is nothing to be done
> -
> -vmlinux vmlinux.unstripped: FORCE
> - @true
> -ifeq ($(CONFIG_X86_NEED_RELOCS),y)
> - $(call cmd,relocs)
> -endif
> -
> -clean:
> - @rm -f $(OUT_RELOCS)/vmlinux.relocs
> -
> -PHONY += FORCE clean
> -
> -FORCE:
> -
> -.PHONY: $(PHONY)
> diff --git a/arch/x86/boot/compressed/Makefile b/arch/x86/boot/compressed/Makefile
> index 606c74f27459..5edee7a9786c 100644
> --- a/arch/x86/boot/compressed/Makefile
> +++ b/arch/x86/boot/compressed/Makefile
> @@ -117,9 +117,12 @@ $(obj)/vmlinux.bin: vmlinux FORCE
>
> targets += $(patsubst $(obj)/%,%,$(vmlinux-objs-y)) vmlinux.bin.all vmlinux.relocs
>
> -# vmlinux.relocs is created by the vmlinux postlink step.
> -$(obj)/vmlinux.relocs: vmlinux
> - @true
> +CMD_RELOCS = arch/x86/tools/relocs
> +quiet_cmd_relocs = RELOCS $@
> + cmd_relocs = $(CMD_RELOCS) $< > $@;$(CMD_RELOCS) --abs-relocs $<
> +
> +$(obj)/vmlinux.relocs: vmlinux.unstripped FORCE
> + $(call if_changed,relocs)

Perhaps, it may make sense to rebuild vmlinux.relocs
when arch/x86/tools/relocs is changed, but
I do not see such dependency in the other
arch/x86/realmode/rm/Makefile.

https://github.com/torvalds/linux/blob/v6.14-rc5/arch/x86/realmode/rm/Makefile#L61

So, I decided it is ok.
If you mind, you can send v3.

--
Best Regards
Masahiro Yamada