On Wed, Mar 21, 2018 at 12:02:06AM +0100, Stefan Agner wrote:
> Use cc-options call for compiler options which are not available
> in clang. With this patch an ARMv7 multi platform kernel can be
> successfully build using clang (tested with version 5.0.1).
>
> Based-on-patches-by: Behan Webster <beh...@converseincode.com>
> Signed-off-by: Stefan Agner <ste...@agner.ch>
> ---
> arch/arm/Makefile | 2 +-
> arch/arm/boot/compressed/Makefile | 2 +-
> 2 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/arch/arm/Makefile b/arch/arm/Makefile
> index e9e3fde3c657..20e9fee1ccc5 100644
> --- a/arch/arm/Makefile
> +++ b/arch/arm/Makefile
> @@ -39,7 +39,7 @@ KBUILD_CFLAGS += $(call
> cc-option,-mno-unaligned-access)
> endif
>
> ifeq ($(CONFIG_FRAME_POINTER),y)
> -KBUILD_CFLAGS +=-fno-omit-frame-pointer -mapcs -mno-sched-prolog
> +KBUILD_CFLAGS +=-fno-omit-frame-pointer $(call cc-option,-mapcs,)
> $(call cc-option,-mno-sched-prolog,)
Some of these options here are to ensure that we generate the following
code, so we can backtrace:
mov ip, sp
stmfd sp!, {fp, ip, lr, pc}
sub fp, ip, #4
If clang isn't producing that code at the start of functions with
CONFIG_FRAME_POINTER=y, then backtracing will not work, and arguably
CONFIG_FRAME_POINTER=y is useless there. In that circumstance, it's
probably better to fail so the user can configure something more
debuggable, rather than having the kernel potentially producing
undebuggable oopses.
--
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