[PATCH] efi/libstub: arm: support building with clang

[PATCH] efi/libstub: arm: support building with clang

[Alistair Strachan]

When building with CONFIG_EFI and CONFIG_EFI_STUB on ARM, the libstub
Makefile would use -mno-single-pic-base without checking it was
supported by the compiler. As the ARM (32-bit) clang backend does not
support this flag, the build would fail.

This changes the Makefile to check the compiler's support for
-mno-single-pic-base before using it, similar to c1c386681bd7 ("ARM:
8767/1: add support for building ARM kernel with clang").

Cc: Stefan Agner <stefan@agner.ch>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Russell King <linux@armlinux.org.uk>
Cc: linux-efi@vger.kernel.org
Cc: linux-arm-kernel@lists.infradead.org
Signed-off-by: Alistair Strachan <astrachan@google.com>
---
 drivers/firmware/efi/libstub/Makefile | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/firmware/efi/libstub/Makefile b/drivers/firmware/efi/libstub/Makefile
index a34e9290a699..91339d13f2a1 100644
--- a/drivers/firmware/efi/libstub/Makefile
+++ b/drivers/firmware/efi/libstub/Makefile
@@ -13,7 +13,8 @@ cflags-$(CONFIG_X86)		+= -m$(BITS) -D__KERNEL__ -O2 \
 
 cflags-$(CONFIG_ARM64)		:= $(subst -pg,,$(KBUILD_CFLAGS)) -fpie
 cflags-$(CONFIG_ARM)		:= $(subst -pg,,$(KBUILD_CFLAGS)) \
-				   -fno-builtin -fpic -mno-single-pic-base
+				   -fno-builtin -fpic \
+				   $(call cc-option,-mno-single-pic-base)
 
 cflags-$(CONFIG_EFI_ARMSTUB)	+= -I$(srctree)/scripts/dtc/libfdt
 
-- 
2.18.0.597.ga71716f1ad-goog

Re: [PATCH] efi/libstub: arm: support building with clang

[Stefan Agner]

On 09.08.2018 18:40, Alistair Strachan wrote:
> When building with CONFIG_EFI and CONFIG_EFI_STUB on ARM, the libstub
> Makefile would use -mno-single-pic-base without checking it was
> supported by the compiler. As the ARM (32-bit) clang backend does not
> support this flag, the build would fail.
> 
> This changes the Makefile to check the compiler's support for
> -mno-single-pic-base before using it, similar to c1c386681bd7 ("ARM:
> 8767/1: add support for building ARM kernel with clang").

Looks good to me:

Reviewed-by: Stefan Agner <stefan@agner.ch>

> 
> Cc: Stefan Agner <stefan@agner.ch>
> Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> Cc: Will Deacon <will.deacon@arm.com>
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Cc: Russell King <linux@armlinux.org.uk>
> Cc: linux-efi@vger.kernel.org
> Cc: linux-arm-kernel@lists.infradead.org
> Signed-off-by: Alistair Strachan <astrachan@google.com>
> ---
>  drivers/firmware/efi/libstub/Makefile | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/firmware/efi/libstub/Makefile
> b/drivers/firmware/efi/libstub/Makefile
> index a34e9290a699..91339d13f2a1 100644
> --- a/drivers/firmware/efi/libstub/Makefile
> +++ b/drivers/firmware/efi/libstub/Makefile
> @@ -13,7 +13,8 @@ cflags-$(CONFIG_X86)		+= -m$(BITS) -D__KERNEL__ -O2 \
>  
>  cflags-$(CONFIG_ARM64)		:= $(subst -pg,,$(KBUILD_CFLAGS)) -fpie
>  cflags-$(CONFIG_ARM)		:= $(subst -pg,,$(KBUILD_CFLAGS)) \
> -				   -fno-builtin -fpic -mno-single-pic-base
> +				   -fno-builtin -fpic \
> +				   $(call cc-option,-mno-single-pic-base)
>  
>  cflags-$(CONFIG_EFI_ARMSTUB)	+= -I$(srctree)/scripts/dtc/libfdt

Re: [PATCH] efi/libstub: arm: support building with clang

[Ard Biesheuvel]

On 11 August 2018 at 10:49, Stefan Agner <stefan@agner.ch> wrote:
> On 09.08.2018 18:40, Alistair Strachan wrote:
>> When building with CONFIG_EFI and CONFIG_EFI_STUB on ARM, the libstub
>> Makefile would use -mno-single-pic-base without checking it was
>> supported by the compiler. As the ARM (32-bit) clang backend does not
>> support this flag, the build would fail.
>>
>> This changes the Makefile to check the compiler's support for
>> -mno-single-pic-base before using it, similar to c1c386681bd7 ("ARM:
>> 8767/1: add support for building ARM kernel with clang").
>
> Looks good to me:
>
> Reviewed-by: Stefan Agner <stefan@agner.ch>
>


Thanks. I will queue this after the merge window closes

>>
>> Cc: Stefan Agner <stefan@agner.ch>
>> Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
>> Cc: Will Deacon <will.deacon@arm.com>
>> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
>> Cc: Russell King <linux@armlinux.org.uk>
>> Cc: linux-efi@vger.kernel.org
>> Cc: linux-arm-kernel@lists.infradead.org
>> Signed-off-by: Alistair Strachan <astrachan@google.com>
>> ---
>>  drivers/firmware/efi/libstub/Makefile | 3 ++-
>>  1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/firmware/efi/libstub/Makefile
>> b/drivers/firmware/efi/libstub/Makefile
>> index a34e9290a699..91339d13f2a1 100644
>> --- a/drivers/firmware/efi/libstub/Makefile
>> +++ b/drivers/firmware/efi/libstub/Makefile
>> @@ -13,7 +13,8 @@ cflags-$(CONFIG_X86)                += -m$(BITS) -D__KERNEL__ -O2 \
>>
>>  cflags-$(CONFIG_ARM64)               := $(subst -pg,,$(KBUILD_CFLAGS)) -fpie
>>  cflags-$(CONFIG_ARM)         := $(subst -pg,,$(KBUILD_CFLAGS)) \
>> -                                -fno-builtin -fpic -mno-single-pic-base
>> +                                -fno-builtin -fpic \
>> +                                $(call cc-option,-mno-single-pic-base)
>>
>>  cflags-$(CONFIG_EFI_ARMSTUB) += -I$(srctree)/scripts/dtc/libfdt