Re: [PATCH] ARM: disable ARMv6 for Clang older than 8.0

From: Joe Perches
Date: Sun Sep 30 2018 - 19:48:27 EST


On Mon, 2018-10-01 at 00:22 +0200, Stefan Agner wrote:
> The kernel passes the ArmV6K architecture to the compiler when
> using the multi platform selection and enabling ARMv6. Clang
> older than version 8.0 emit assembly with an non-existing CPU,
> which then makes the assembler fail. Prevent the user from
> selecting ARMv6 when using Clang before 8.0.
>
> Signed-off-by: Stefan Agner <stefan@xxxxxxxx>
> Link: https://github.com/ClangBuiltLinux/linux/issues/55
> ---
> arch/arm/Kconfig | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
> index e8cd55a5b04c..8da160757381 100644
> --- a/arch/arm/Kconfig
> +++ b/arch/arm/Kconfig
> @@ -671,6 +671,7 @@ config ARCH_MULTI_V4_V5
>
> config ARCH_MULTI_V6
> bool "ARMv6 based platforms (ARM11)"
> + depends on !CC_IS_CLANG || CLANG_VERSION>=80000
> select ARCH_MULTI_V6_V7
> select CPU_V6K
>

Perhaps it'd be better to avoid this in selection
criteria in Kconfig and instead add this to
include/linux/compiler_clang.h
---
include/linux/compiler-clang.h | 4 ++++
1 file changed, 4 insertions(+)

diff --git a/include/linux/compiler-clang.h b/include/linux/compiler-clang.h
index b1ce500fe8b3..90fd16c85359 100644
--- a/include/linux/compiler-clang.h
+++ b/include/linux/compiler-clang.h
@@ -3,6 +3,10 @@
#error "Please don't include <linux/compiler-clang.h> directly, include <linux/compiler.h> instead."
#endif

+#if defined(CONFIG_ARCH_MULTI_V6) && CLANG_VERSION < 80000
+# error Sorry, your compiler is too old - please upgrade it.
+#endif
+
/* Some compiler specific definitions are overwritten here
* for Clang compiler
*/