When building with CONFIG_THUMB2_KERNEL=y + a version of clang from
Debian using CROSS_COMPILE=arm-linux-gnueabihf-, the following warning
occurs frequently:
<built-in>:383:9: warning: '__thumb2__' macro redefined [-Wmacro-redefined]
#define __thumb2__ 2
^
<built-in>:353:9: note: previous definition is here
#define __thumb2__ 1
^
1 warning generated.
Debian carries a downstream patch that changes the default CPU of the
arm-linux-gnueabihf target from 'arm1176jzf-s' (v6) to 'cortex-a7' (v7).
As a result, '-mthumb' defines both '__thumb__' and '__thumb2__'. The
define of '__thumb2__' via the command line was purposefully added to
catch a situation like this.
In a similar vein as commit 26b12e084bce ("ARM: 9264/1: only use
-mtp=cp15 for the compiler"), do not add '-mthumb' to AFLAGS_ISA, as it
is already passed to the assembler via '-Wa,-mthumb' and '__thumb2__' is
already defined for preprocessing.
Fixes: 1d2e9b67b001 ("ARM: 9265/1: pass -march= only to compiler")
Link: https://salsa.debian.org/pkg-llvm-team/llvm-toolchain/-/raw/622dbcbd40b316ed3905a2d25d9623544a06e6b1/debian/patches/930008-arm.diff
Reported-by: "kernelci.org bot" <[email protected]>
Reviewed-by: Nick Desaulniers <[email protected]>
Tested-by: Nick Desaulniers <[email protected]>
Signed-off-by: Nathan Chancellor <[email protected]>
---
v2:
* Add Nick's review and test tags.
* Call out explicitly that CROSS_COMPILE=arm-linux-gnueabihf- is
needed to reproduce this issue in commit message (Nick).
* Fix dead link in commit message (Nick).
* Use the snapshot branch for the patch link, as the diff is more up
to date against upstream LLVM (Nick).
v1: https://lore.kernel.org/[email protected]/
arch/arm/Makefile | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/arch/arm/Makefile b/arch/arm/Makefile
index 357f0d9b8607..d1ebb746ff40 100644
--- a/arch/arm/Makefile
+++ b/arch/arm/Makefile
@@ -131,8 +131,9 @@ endif
AFLAGS_NOWARN :=$(call as-option,-Wa$(comma)-mno-warn-deprecated,-Wa$(comma)-W)
ifeq ($(CONFIG_THUMB2_KERNEL),y)
-CFLAGS_ISA :=-mthumb -Wa,-mimplicit-it=always $(AFLAGS_NOWARN)
+CFLAGS_ISA :=-Wa,-mimplicit-it=always $(AFLAGS_NOWARN)
AFLAGS_ISA :=$(CFLAGS_ISA) -Wa$(comma)-mthumb -D__thumb2__=2
+CFLAGS_ISA +=-mthumb
else
CFLAGS_ISA :=$(call cc-option,-marm,) $(AFLAGS_NOWARN)
AFLAGS_ISA :=$(CFLAGS_ISA)
base-commit: 0c52591d22e99759da3793f19249bbf45ad742bd
--
2.38.1
On Fri, 18 Nov 2022 at 01:34, Nathan Chancellor <[email protected]> wrote:
>
> When building with CONFIG_THUMB2_KERNEL=y + a version of clang from
> Debian using CROSS_COMPILE=arm-linux-gnueabihf-, the following warning
> occurs frequently:
>
> <built-in>:383:9: warning: '__thumb2__' macro redefined [-Wmacro-redefined]
> #define __thumb2__ 2
> ^
> <built-in>:353:9: note: previous definition is here
> #define __thumb2__ 1
> ^
> 1 warning generated.
>
> Debian carries a downstream patch that changes the default CPU of the
> arm-linux-gnueabihf target from 'arm1176jzf-s' (v6) to 'cortex-a7' (v7).
> As a result, '-mthumb' defines both '__thumb__' and '__thumb2__'. The
> define of '__thumb2__' via the command line was purposefully added to
> catch a situation like this.
>
> In a similar vein as commit 26b12e084bce ("ARM: 9264/1: only use
> -mtp=cp15 for the compiler"), do not add '-mthumb' to AFLAGS_ISA, as it
> is already passed to the assembler via '-Wa,-mthumb' and '__thumb2__' is
> already defined for preprocessing.
>
> Fixes: 1d2e9b67b001 ("ARM: 9265/1: pass -march= only to compiler")
> Link: https://salsa.debian.org/pkg-llvm-team/llvm-toolchain/-/raw/622dbcbd40b316ed3905a2d25d9623544a06e6b1/debian/patches/930008-arm.diff
> Reported-by: "kernelci.org bot" <[email protected]>
> Reviewed-by: Nick Desaulniers <[email protected]>
> Tested-by: Nick Desaulniers <[email protected]>
> Signed-off-by: Nathan Chancellor <[email protected]>
Reviewed-by: Ard Biesheuvel <[email protected]>
> ---
> v2:
> * Add Nick's review and test tags.
> * Call out explicitly that CROSS_COMPILE=arm-linux-gnueabihf- is
> needed to reproduce this issue in commit message (Nick).
> * Fix dead link in commit message (Nick).
> * Use the snapshot branch for the patch link, as the diff is more up
> to date against upstream LLVM (Nick).
> v1: https://lore.kernel.org/[email protected]/
> arch/arm/Makefile | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/arch/arm/Makefile b/arch/arm/Makefile
> index 357f0d9b8607..d1ebb746ff40 100644
> --- a/arch/arm/Makefile
> +++ b/arch/arm/Makefile
> @@ -131,8 +131,9 @@ endif
> AFLAGS_NOWARN :=$(call as-option,-Wa$(comma)-mno-warn-deprecated,-Wa$(comma)-W)
>
> ifeq ($(CONFIG_THUMB2_KERNEL),y)
> -CFLAGS_ISA :=-mthumb -Wa,-mimplicit-it=always $(AFLAGS_NOWARN)
> +CFLAGS_ISA :=-Wa,-mimplicit-it=always $(AFLAGS_NOWARN)
> AFLAGS_ISA :=$(CFLAGS_ISA) -Wa$(comma)-mthumb -D__thumb2__=2
> +CFLAGS_ISA +=-mthumb
> else
> CFLAGS_ISA :=$(call cc-option,-marm,) $(AFLAGS_NOWARN)
> AFLAGS_ISA :=$(CFLAGS_ISA)
>
> base-commit: 0c52591d22e99759da3793f19249bbf45ad742bd
> --
> 2.38.1
>