[PATCH v2] kbuild: move -Wundef from KBUILD_CFLAGS to KBUILD_CPPFLAGS

Masahiro Yamada masahiroy at kernel.org
Tue Sep 13 01:07:27 PDT 2022 

The use of an undefined macro in an #if directive is warned, but only
in *.c files. No warning from other files such as *.S, *.lds.S.

Since -Wundef is a preprocessor-related warning, it should be added to
KBUILD_CPPFLAGS instead of KBUILD_CFLAGS.

Fix some uncovered issues.

[1] Add -D__LINUX_ARM_ARCH__=* to KBUILD_CPPFLAGS

In file included from arch/arm/kernel/vmlinux.lds.S:13:
./arch/arm/include/asm/cache.h:23:31: warning: "__LINUX_ARM_ARCH__" is not defined, evaluates to 0 [-Wundef]
   23 | #if defined(CONFIG_AEABI) && (__LINUX_ARM_ARCH__ >= 5)
      |                               ^~~~~~~~~~~~~~~~~~

[2] Add missing #include <asm/pgtable.h>

In file included from arch/arm/mm/cache-v7.S:17:
arch/arm/mm/proc-macros.S:109:5: warning: "L_PTE_SHARED" is not defined, evaluates to 0 [-Wundef]
  109 | #if L_PTE_SHARED != PTE_EXT_SHARED
      |     ^~~~~~~~~~~~
arch/arm/mm/proc-macros.S:109:21: warning: "PTE_EXT_SHARED" is not defined, evaluates to 0 [-Wundef]
  109 | #if L_PTE_SHARED != PTE_EXT_SHARED
      |                     ^~~~~~~~~~~~~~
arch/arm/mm/proc-macros.S:113:10: warning: "L_PTE_XN" is not defined, evaluates to 0 [-Wundef]
  113 |         (L_PTE_XN+L_PTE_USER+L_PTE_RDONLY+L_PTE_DIRTY+L_PTE_YOUNG+\
      |          ^~~~~~~~
arch/arm/mm/proc-macros.S:113:19: warning: "L_PTE_USER" is not defined, evaluates to 0 [-Wundef]
  113 |         (L_PTE_XN+L_PTE_USER+L_PTE_RDONLY+L_PTE_DIRTY+L_PTE_YOUNG+\
      |                   ^~~~~~~~~~
arch/arm/mm/proc-macros.S:113:30: warning: "L_PTE_RDONLY" is not defined, evaluates to 0 [-Wundef]
  113 |         (L_PTE_XN+L_PTE_USER+L_PTE_RDONLY+L_PTE_DIRTY+L_PTE_YOUNG+\
      |                              ^~~~~~~~~~~~
arch/arm/mm/proc-macros.S:113:43: warning: "L_PTE_DIRTY" is not defined, evaluates to 0 [-Wundef]
  113 |         (L_PTE_XN+L_PTE_USER+L_PTE_RDONLY+L_PTE_DIRTY+L_PTE_YOUNG+\
      |                                           ^~~~~~~~~~~
arch/arm/mm/proc-macros.S:113:55: warning: "L_PTE_YOUNG" is not defined, evaluates to 0 [-Wundef]
  113 |         (L_PTE_XN+L_PTE_USER+L_PTE_RDONLY+L_PTE_DIRTY+L_PTE_YOUNG+\
      |                                                       ^~~~~~~~~~~
arch/arm/mm/proc-macros.S:114:10: warning: "L_PTE_PRESENT" is not defined, evaluates to 0 [-Wundef]
  114 |          L_PTE_PRESENT) > L_PTE_SHARED
      |          ^~~~~~~~~~~~~
arch/arm/mm/proc-macros.S:114:27: warning: "L_PTE_SHARED" is not defined, evaluates to 0 [-Wundef]
  114 |          L_PTE_PRESENT) > L_PTE_SHARED
      |                           ^~~~~~~~~~~~

[3] #if -> #ifdef

arch/riscv/kernel/head.S:329:5: warning: "CONFIG_RISCV_BOOT_SPINWAIT" is not defined, evaluates to 0 [-Wundef]
  329 | #if CONFIG_RISCV_BOOT_SPINWAIT
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~

[4] #elif -> #elif defined()

arch/s390/boot/decompressor.c:28:7: warning: "CONFIG_KERNEL_ZSTD" is not defined, evaluates to 0 [-Wundef]
   28 | #elif CONFIG_KERNEL_ZSTD
      |       ^~~~~~~~~~~~~~~~~~

Signed-off-by: Masahiro Yamada <masahiroy at kernel.org>
---

Changes in v2:
  - Fix warnings

 Makefile                      | 4 ++--
 arch/arm/Makefile             | 1 +
 arch/arm/mm/proc-macros.S     | 1 +
 arch/riscv/kernel/head.S      | 2 +-
 arch/s390/boot/decompressor.c | 2 +-
 5 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/Makefile b/Makefile
index 4beeb96f9d81..bf4328535cf9 100644
--- a/Makefile
+++ b/Makefile
@@ -523,12 +523,12 @@ LINUXINCLUDE    := \
 		$(USERINCLUDE)
 
 KBUILD_AFLAGS   := -D__ASSEMBLY__ -fno-PIE
-KBUILD_CFLAGS   := -Wall -Wundef -Werror=strict-prototypes -Wno-trigraphs \
+KBUILD_CFLAGS   := -Wall -Werror=strict-prototypes -Wno-trigraphs \
 		   -fno-strict-aliasing -fno-common -fshort-wchar -fno-PIE \
 		   -Werror=implicit-function-declaration -Werror=implicit-int \
 		   -Werror=return-type -Wno-format-security \
 		   -std=gnu11
-KBUILD_CPPFLAGS := -D__KERNEL__
+KBUILD_CPPFLAGS := -D__KERNEL__ -Wundef
 KBUILD_AFLAGS_KERNEL :=
 KBUILD_CFLAGS_KERNEL :=
 KBUILD_AFLAGS_MODULE  := -DMODULE
diff --git a/arch/arm/Makefile b/arch/arm/Makefile
index 29d15c9a433e..4bb5743fe3a4 100644
--- a/arch/arm/Makefile
+++ b/arch/arm/Makefile
@@ -129,6 +129,7 @@ AFLAGS_ISA	:=$(CFLAGS_ISA)
 endif
 
 # Need -Uarm for gcc < 3.x
+KBUILD_CPPFLAGS	+= $(filter -D%, $(arch-y))
 KBUILD_CFLAGS	+=$(CFLAGS_ABI) $(CFLAGS_ISA) $(arch-y) $(tune-y) $(call cc-option,-mshort-load-bytes,$(call cc-option,-malignment-traps,)) -msoft-float -Uarm
 KBUILD_AFLAGS	+=$(CFLAGS_ABI) $(AFLAGS_ISA) $(arch-y) $(tune-y) -include asm/unified.h -msoft-float
 
diff --git a/arch/arm/mm/proc-macros.S b/arch/arm/mm/proc-macros.S
index fa6999e24b07..e43f6d716b4b 100644
--- a/arch/arm/mm/proc-macros.S
+++ b/arch/arm/mm/proc-macros.S
@@ -6,6 +6,7 @@
  *  VM_EXEC
  */
 #include <asm/asm-offsets.h>
+#include <asm/pgtable.h>
 #include <asm/thread_info.h>
 
 #ifdef CONFIG_CPU_V7M
diff --git a/arch/riscv/kernel/head.S b/arch/riscv/kernel/head.S
index b865046e4dbb..4bf6c449d78b 100644
--- a/arch/riscv/kernel/head.S
+++ b/arch/riscv/kernel/head.S
@@ -326,7 +326,7 @@ clear_bss_done:
 	call soc_early_init
 	tail start_kernel
 
-#if CONFIG_RISCV_BOOT_SPINWAIT
+#ifdef CONFIG_RISCV_BOOT_SPINWAIT
 .Lsecondary_start:
 	/* Set trap vector to spin forever to help debug */
 	la a3, .Lsecondary_park
diff --git a/arch/s390/boot/decompressor.c b/arch/s390/boot/decompressor.c
index e27c2140d620..f96657faffdc 100644
--- a/arch/s390/boot/decompressor.c
+++ b/arch/s390/boot/decompressor.c
@@ -25,7 +25,7 @@
 
 #ifdef CONFIG_KERNEL_BZIP2
 #define BOOT_HEAP_SIZE	0x400000
-#elif CONFIG_KERNEL_ZSTD
+#elif defined(CONFIG_KERNEL_ZSTD)
 #define BOOT_HEAP_SIZE	0x30000
 #else
 #define BOOT_HEAP_SIZE	0x10000
-- 
2.34.1

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