[v7] x86: strict separation of startup code

[PATCH v7 18/22] x86/kbuild: Incorporate boot/startup/ via Kbuild makefile

Posted by Ard Biesheuvel 1 week, 3 days ago

From: Ard Biesheuvel <ardb@kernel.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@kernel.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 4b4e2a3ac6df..4db7e4bf69f5 100644
--- a/arch/x86/Makefile
+++ b/arch/x86/Makefile
@@ -275,7 +275,6 @@ archprepare: $(cpufeaturemasks.hdr)
 ###
 # Kernel objects
 
-core-y  += arch/x86/boot/startup/
 libs-y  += arch/x86/lib/
 
 # drivers-y are linked after core-y
-- 
2.51.0.268.g9569e192d0-goog

[tip: x86/sev] x86/kbuild: Incorporate boot/startup/ via Kbuild makefile

Posted by tip-bot2 for Ard Biesheuvel 3 days ago

The following commit has been merged into the x86/sev branch of tip:

Commit-ID:     749627c3980e4421b709857e979e8aa16a4c7147
Gitweb:        https://git.kernel.org/tip/749627c3980e4421b709857e979e8aa16a4c7147
Author:        Ard Biesheuvel <ardb@kernel.org>
AuthorDate:    Thu, 28 Aug 2025 12:22:21 +02:00
Committer:     Borislav Petkov (AMD) <bp@alien8.de>
CommitterDate: Wed, 03 Sep 2025 17:59:59 +02:00

x86/kbuild: Incorporate boot/startup/ via Kbuild makefile

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@kernel.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/20250828102202.1849035-42-ardb+git@google.com
---
 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 f7fb3d8..36b985d 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 1913d34..9b76e77 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