linux-kernel - [PATCH v4 20/24] x86/kbuild: Incorporate boot/startup/ via Kbuild makefile

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Message-ID: <20250709080840.2233208-46-ardb+git@google.com>
Date: Wed,  9 Jul 2025 10:09:01 +0200
From: Ard Biesheuvel <ardb+git@...gle.com>
To: linux-kernel@...r.kernel.org
Cc: linux-efi@...r.kernel.org, x86@...nel.org, 
	Ard Biesheuvel <ardb@...nel.org>, Borislav Petkov <bp@...en8.de>, Ingo Molnar <mingo@...nel.org>, 
	Dionna Amalie Glaze <dionnaglaze@...gle.com>, Kevin Loughlin <kevinloughlin@...gle.com>, 
	Tom Lendacky <thomas.lendacky@....com>, Josh Poimboeuf <jpoimboe@...nel.org>, 
	Peter Zijlstra <peterz@...radead.org>
Subject: [PATCH v4 20/24] x86/kbuild: Incorporate boot/startup/ via Kbuild makefile

From: Ard Biesheuvel <ardb@...nel.org>

Using core-y is not the correct way to get kbuild to descend into
arch/x86/boot/startup. For instance, building an individual object does
not work as expected when the pattern rule is local to the Makefile

  $ make arch/x86/boot/startup/map_kernel.pi.o
    GEN     Makefile
    CALL    /home/ardb/linux/scripts/checksyscalls.sh
    DESCEND objtool
    INSTALL libsubcmd_headers
  make[3]: *** No rule to make target 'arch/x86/boot/startup/map_kernel.pi.o'.  Stop.
  make[2]: *** [/home/ardb/linux/scripts/Makefile.build:461: arch/x86] Error 2
  make[1]: *** [/home/ardb/linux/Makefile:2011: .] Error 2
  make: *** [/home/ardb/linux/Makefile:248: __sub-make] Error 2

So use obj-y from arch.x86/Kbuild instead, which makes things work as
expected.

Signed-off-by: Ard Biesheuvel <ardb@...nel.org>
---
 arch/x86/Kbuild   | 2 ++
 arch/x86/Makefile | 1 -
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/x86/Kbuild b/arch/x86/Kbuild
index f7fb3d88c57b..36b985d0e7bf 100644
--- a/arch/x86/Kbuild
+++ b/arch/x86/Kbuild
@@ -3,6 +3,8 @@
 # Branch profiling isn't noinstr-safe.  Disable it for arch/x86/*
 subdir-ccflags-$(CONFIG_TRACE_BRANCH_PROFILING) += -DDISABLE_BRANCH_PROFILING
 
+obj-y += boot/startup/
+
 obj-$(CONFIG_ARCH_HAS_CC_PLATFORM) += coco/
 
 obj-y += entry/
diff --git a/arch/x86/Makefile b/arch/x86/Makefile
index 1913d342969b..9b76e77ff7f7 100644
--- a/arch/x86/Makefile
+++ b/arch/x86/Makefile
@@ -286,7 +286,6 @@ archprepare: $(cpufeaturemasks.hdr)
 ###
 # Kernel objects
 
-core-y  += arch/x86/boot/startup/
 libs-y  += arch/x86/lib/
 
 # drivers-y are linked after core-y
-- 
2.50.0.727.gbf7dc18ff4-goog