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

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Message-ID: <20250311111745.GDZ9Ab2f6-iHLXmRra@fat_crate.local>
Date: Tue, 11 Mar 2025 12:17:45 +0100
From: Borislav Petkov <bp@...en8.de>
To: Ard Biesheuvel <ardb+git@...gle.com>
Cc: linux-kernel@...r.kernel.org, linux-kbuild@...r.kernel.org,
	x86@...nel.org, Ard Biesheuvel <ardb@...nel.org>,
	Masahiro Yamada <masahiroy@...nel.org>,
	Ingo Molnar <mingo@...nel.org>, Petr Pavlu <petr.pavlu@...e.com>
Subject: Re: [PATCH v2 4/4] x86: Get rid of Makefile.postlink

+ Petr for 9d9173e9ceb6

@Petr, you can find the whole thread on lore.

On Tue, Mar 11, 2025 at 12:06:21PM +0100, Ard Biesheuvel wrote:
> From: Ard Biesheuvel <ardb@...nel.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@...nel.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 $@
> -
> -# `@...e` prevents complaint when there is nothing to be done
> -
> -vmlinux vmlinux.unstripped: FORCE
> -	@true
> -ifeq ($(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)
>  
>  vmlinux.bin.all-y := $(obj)/vmlinux.bin
>  vmlinux.bin.all-$(CONFIG_X86_NEED_RELOCS) += $(obj)/vmlinux.relocs
> -- 
> 2.49.0.rc0.332.g42c0ae87b1-goog
> 

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette