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

[Ard Biesheuvel <ardb+git@google.com>]

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 |  8 +++--
 2 files changed, 5 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..8b7da3fc3f03 100644
--- a/arch/x86/boot/compressed/Makefile
+++ b/arch/x86/boot/compressed/Makefile
@@ -117,9 +117,11 @@ $(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
-- 
2.48.1.601.g30ceb7b040-goog