diff mbox series

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

Message ID 20250311110616.148682-10-ardb+git@google.com (mailing list archive)
State New
Headers show
Series x86/build: Get rid of vmlinux postlink step | expand

Commit Message

Ard Biesheuvel March 11, 2025, 11:06 a.m. UTC 
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(-)

Comments

Borislav Petkov March 11, 2025, 11:17 a.m. UTC | #1 
+ 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@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)
>  
>  vmlinux.bin.all-y := $(obj)/vmlinux.bin
>  vmlinux.bin.all-$(CONFIG_X86_NEED_RELOCS) += $(obj)/vmlinux.relocs
> -- 
> 2.49.0.rc0.332.g42c0ae87b1-goog
>
Petr Pavlu March 12, 2025, 12:35 p.m. UTC | #2 
On 3/11/25 12:17, Borislav Petkov wrote:
> + 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@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>

For what it's worth, the changes look to me as an improvement over the
previous implementation.
diff mbox series

Patch

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)
 
 vmlinux.bin.all-y := $(obj)/vmlinux.bin
 vmlinux.bin.all-$(CONFIG_X86_NEED_RELOCS) += $(obj)/vmlinux.relocs