[PATCH v3 1/2] kbuild: move -Werror from KBUILD_CFLAGS to KBUILD_CPPFLAGS

[PATCH v3 1/2] kbuild: move -Werror from KBUILD_CFLAGS to KBUILD_CPPFLAGS

[Masahiro Yamada]

CONFIG_WERROR turns warnings into errors, which  happens only for *.c
files because -Werror is added to KBUILD_CFLAGS.

Adding it to KBUILD_CPPFLAGS makes more sense because preprocessors
understand the -Werror option.

For example, you can put a #warning directive in any preprocessed code.

    warning: #warning "this is a warning message" [-Wcpp]

If -Werror is added, it is promoted to an error.

    error: #warning "this is a warning message" [-Werror=cpp]

This commit moves -Werror to KBUILD_CPPFLAGS so it works in the same way
for *.c, *.S, *.lds.S or whatever needs preprocessing.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
---

(no changes since v1)

 Makefile | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/Makefile b/Makefile
index 85a63a1d29b3..790760d26ea0 100644
--- a/Makefile
+++ b/Makefile
@@ -859,7 +859,8 @@ stackp-flags-$(CONFIG_STACKPROTECTOR_STRONG)      := -fstack-protector-strong
 
 KBUILD_CFLAGS += $(stackp-flags-y)
 
-KBUILD_CFLAGS-$(CONFIG_WERROR) += -Werror
+KBUILD_CPPFLAGS-$(CONFIG_WERROR) += -Werror
+KBUILD_CPPFLAGS += $(KBUILD_CPPFLAGS-y)
 KBUILD_CFLAGS-$(CONFIG_CC_NO_ARRAY_BOUNDS) += -Wno-array-bounds
 
 KBUILD_RUSTFLAGS-$(CONFIG_WERROR) += -Dwarnings
-- 
2.34.1

[PATCH v3 2/2] kbuild: move -Wundef from KBUILD_CFLAGS to KBUILD_CPPFLAGS

[Masahiro Yamada]

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
      |       ^~~~~~~~~~~~~~~~~~

[5] Exclude arm64 for now

In file included from arch/arm64/kernel/vmlinux.lds.S:65:
arch/arm64/include/asm/kernel-pgtable.h:135:41: warning: "PMD_SHIFT" is not defined, evaluates to 0 [-Wundef]
  135 | #define ARM64_MEMSTART_SHIFT            PMD_SHIFT
      |                                         ^~~~~~~~~
In file included from arch/arm64/include/asm/asm-uaccess.h:8,
                 from arch/arm64/kernel/entry.S:29:
arch/arm64/include/asm/kernel-pgtable.h:135:41: warning: "PMD_SHIFT" is not defined, evaluates to 0 [-Wundef]
  135 | #define ARM64_MEMSTART_SHIFT            PMD_SHIFT
      |                                         ^~~~~~~~~

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

Changes in v3:
  - Suppress arm64 warnings

Changes in v2:
  - Fix warnings

 Makefile                      | 4 ++--
 arch/arm/Makefile             | 1 +
 arch/arm/mm/proc-macros.S     | 1 +
 arch/arm64/Makefile           | 4 ++++
 arch/riscv/kernel/head.S      | 2 +-
 arch/s390/boot/decompressor.c | 2 +-
 6 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/Makefile b/Makefile
index 790760d26ea0..b7fff76a33eb 100644
--- a/Makefile
+++ b/Makefile
@@ -559,12 +559,12 @@ 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_RUSTFLAGS := $(rust_common_flags) \
 		    --target=$(objtree)/rust/target.json \
 		    -Cpanic=abort -Cembed-bitcode=n -Clto=n \
diff --git a/arch/arm/Makefile b/arch/arm/Makefile
index c846119c448f..f8a1ae6beef7 100644
--- a/arch/arm/Makefile
+++ b/arch/arm/Makefile
@@ -132,6 +132,7 @@ 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/arm64/Makefile b/arch/arm64/Makefile
index 5e56d26a2239..ca8a02e3e591 100644
--- a/arch/arm64/Makefile
+++ b/arch/arm64/Makefile
@@ -36,6 +36,10 @@ ifeq ($(CONFIG_BROKEN_GAS_INST),y)
 $(warning Detected assembler with broken .inst; disassembly will be unreliable)
 endif
 
+# REVISIT
+KBUILD_CPPFLAGS	:= $(filter-out -Wundef, $(KBUILD_CPPFLAGS))
+KBUILD_CFLAGS	+= -Wundef
+
 KBUILD_CFLAGS	+= -mgeneral-regs-only	\
 		   $(compat_vdso) $(cc_has_k_constraint)
 KBUILD_CFLAGS	+= $(call cc-disable-warning, psabi)
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

Re: [PATCH v3 1/2] kbuild: move -Werror from KBUILD_CFLAGS to KBUILD_CPPFLAGS

[Nathan Chancellor]

On Thu, Oct 13, 2022 at 03:01:17AM +0900, Masahiro Yamada wrote:
> CONFIG_WERROR turns warnings into errors, which  happens only for *.c
> files because -Werror is added to KBUILD_CFLAGS.
> 
> Adding it to KBUILD_CPPFLAGS makes more sense because preprocessors
> understand the -Werror option.
> 
> For example, you can put a #warning directive in any preprocessed code.
> 
>     warning: #warning "this is a warning message" [-Wcpp]
> 
> If -Werror is added, it is promoted to an error.
> 
>     error: #warning "this is a warning message" [-Werror=cpp]
> 
> This commit moves -Werror to KBUILD_CPPFLAGS so it works in the same way
> for *.c, *.S, *.lds.S or whatever needs preprocessing.
> 
> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
> Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
> ---
> 
> (no changes since v1)
> 
>  Makefile | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/Makefile b/Makefile
> index 85a63a1d29b3..790760d26ea0 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -859,7 +859,8 @@ stackp-flags-$(CONFIG_STACKPROTECTOR_STRONG)      := -fstack-protector-strong
>  
>  KBUILD_CFLAGS += $(stackp-flags-y)
>  
> -KBUILD_CFLAGS-$(CONFIG_WERROR) += -Werror
> +KBUILD_CPPFLAGS-$(CONFIG_WERROR) += -Werror
> +KBUILD_CPPFLAGS += $(KBUILD_CPPFLAGS-y)
>  KBUILD_CFLAGS-$(CONFIG_CC_NO_ARRAY_BOUNDS) += -Wno-array-bounds
>  
>  KBUILD_RUSTFLAGS-$(CONFIG_WERROR) += -Dwarnings
> -- 
> 2.34.1
> 
> 

For what it's worth, this is going to break 32-bit ARM builds with clang
plus the integrated assembler due to
https://github.com/ClangBuiltLinux/linux/issues/1315:

clang-16: error: argument unused during compilation: '-march=armv7-a' [-Werror,-Wunused-command-line-argument]

Ultimately, I want -Wunused-command-line-argument to be an error anyways
(https://github.com/ClangBuiltLinux/linux/issues/1587) but it would be
nice to get these cleaned up before this goes in.

Cheers,
Nathan

Re: [PATCH v3 1/2] kbuild: move -Werror from KBUILD_CFLAGS to KBUILD_CPPFLAGS

[Nick Desaulniers]

On Fri, Oct 14, 2022 at 9:03 AM Nathan Chancellor <nathan@kernel.org> wrote:
>
> On Thu, Oct 13, 2022 at 03:01:17AM +0900, Masahiro Yamada wrote:
> > CONFIG_WERROR turns warnings into errors, which  happens only for *.c
> > files because -Werror is added to KBUILD_CFLAGS.
> >
> > Adding it to KBUILD_CPPFLAGS makes more sense because preprocessors
> > understand the -Werror option.
> >
> For what it's worth, this is going to break 32-bit ARM builds with clang
> plus the integrated assembler due to
> https://github.com/ClangBuiltLinux/linux/issues/1315:
>
> clang-16: error: argument unused during compilation: '-march=armv7-a' [-Werror,-Wunused-command-line-argument]

Ah, sorry, I should have finished off that series back then. I've
rebased the series and sent a v4.
https://lore.kernel.org/llvm/20221014201354.3190007-1-ndesaulniers@google.com/

You mentioned to me on IRC
https://lore.kernel.org/linux-next/CAK7LNARg8OpqLR_71PJV3ZoLuDV8+mz9mphg=CzEeEEMY0G3rw@mail.gmail.com/
maybe will be a conflict.

>
> Ultimately, I want -Wunused-command-line-argument to be an error anyways
> (https://github.com/ClangBuiltLinux/linux/issues/1587) but it would be
> nice to get these cleaned up before this goes in.
>
> Cheers,
> Nathan



-- 
Thanks,
~Nick Desaulniers

Re: [PATCH v3 1/2] kbuild: move -Werror from KBUILD_CFLAGS to KBUILD_CPPFLAGS

[Masahiro Yamada]

On Sat, Oct 15, 2022 at 1:03 AM Nathan Chancellor <nathan@kernel.org> wrote:
>
> On Thu, Oct 13, 2022 at 03:01:17AM +0900, Masahiro Yamada wrote:
> > CONFIG_WERROR turns warnings into errors, which  happens only for *.c
> > files because -Werror is added to KBUILD_CFLAGS.
> >
> > Adding it to KBUILD_CPPFLAGS makes more sense because preprocessors
> > understand the -Werror option.
> >
> > For example, you can put a #warning directive in any preprocessed code.
> >
> >     warning: #warning "this is a warning message" [-Wcpp]
> >
> > If -Werror is added, it is promoted to an error.
> >
> >     error: #warning "this is a warning message" [-Werror=cpp]
> >
> > This commit moves -Werror to KBUILD_CPPFLAGS so it works in the same way
> > for *.c, *.S, *.lds.S or whatever needs preprocessing.
> >
> > Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
> > Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
> > ---
> >
> > (no changes since v1)
> >
> >  Makefile | 3 ++-
> >  1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/Makefile b/Makefile
> > index 85a63a1d29b3..790760d26ea0 100644
> > --- a/Makefile
> > +++ b/Makefile
> > @@ -859,7 +859,8 @@ stackp-flags-$(CONFIG_STACKPROTECTOR_STRONG)      := -fstack-protector-strong
> >
> >  KBUILD_CFLAGS += $(stackp-flags-y)
> >
> > -KBUILD_CFLAGS-$(CONFIG_WERROR) += -Werror
> > +KBUILD_CPPFLAGS-$(CONFIG_WERROR) += -Werror
> > +KBUILD_CPPFLAGS += $(KBUILD_CPPFLAGS-y)
> >  KBUILD_CFLAGS-$(CONFIG_CC_NO_ARRAY_BOUNDS) += -Wno-array-bounds
> >
> >  KBUILD_RUSTFLAGS-$(CONFIG_WERROR) += -Dwarnings
> > --
> > 2.34.1
> >
> >
>
> For what it's worth, this is going to break 32-bit ARM builds with clang
> plus the integrated assembler due to
> https://github.com/ClangBuiltLinux/linux/issues/1315:
>
> clang-16: error: argument unused during compilation: '-march=armv7-a' [-Werror,-Wunused-command-line-argument]
>
> Ultimately, I want -Wunused-command-line-argument to be an error anyways
> (https://github.com/ClangBuiltLinux/linux/issues/1587) but it would be
> nice to get these cleaned up before this goes in.
>
> Cheers,
> Nathan


OK, I will postpone this patch.
Thanks.



-- 
Best Regards
Masahiro Yamada