Re: [PATCH] x86: add the flag -fno-reorder-blocks-and-partition

[Ingo Molnar <mingo@kernel.org>]

* Mikulas Patocka <mpatocka@redhat.com> wrote:

> GCC 8 turns on -freorder-blocks-and-partition by default, the ORC unwinder 
> can't deal with it and it results in a lot of warnings "sibling call from 
> callable instruction with modified stack frame". This patch adds the 
> -fno-reorder-blocks-and-partition option to KBUILD_CFLAGS.
> 
> Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
> Cc: stable@vger.kernel.org
> 
> ---
>  arch/x86/Makefile |    1 +
>  1 file changed, 1 insertion(+)
> 
> Index: linux-2.6/arch/x86/Makefile
> ===================================================================
> --- linux-2.6.orig/arch/x86/Makefile	2018-05-15 07:19:40.000000000 +0200
> +++ linux-2.6/arch/x86/Makefile	2018-05-15 07:19:40.000000000 +0200
> @@ -59,6 +59,7 @@ endif
>  #
>  KBUILD_CFLAGS += -mno-sse -mno-mmx -mno-sse2 -mno-3dnow
>  KBUILD_CFLAGS += $(call cc-option,-mno-avx,)
> +KBUILD_CFLAGS += $(call cc-option,-fno-reorder-blocks-and-partition,)

Could you check whether the latest objtool fixes in -tip:

  git git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip.git master

solves those warnings?

Thanks,

	Ingo