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SubjectRe: PROBLEM: 5.11.0-rc7 fails to compile with error: ‘-mindirect-branch’ and ‘-fcf-protection’ are not compatible
And for good measure: reverting that commit 

20bf2b378729c4a0366a53e2018a0b70ace94bcd

flagged by the bisect right on top of the current tree compiles fine.

On Sun, Feb 07, 2021 at 07:26:01PM -0500, Stuart Little wrote:
> The result of the bisect on the issue reported in the previous message:
>
> --- cut ---
>
> 20bf2b378729c4a0366a53e2018a0b70ace94bcd is the first bad commit
> commit 20bf2b378729c4a0366a53e2018a0b70ace94bcd
> Author: Josh Poimboeuf <jpoimboe@redhat.com>
> Date: Thu Jan 28 15:52:19 2021 -0600
>
> x86/build: Disable CET instrumentation in the kernel
>
> With retpolines disabled, some configurations of GCC, and specifically
> the GCC versions 9 and 10 in Ubuntu will add Intel CET instrumentation
> to the kernel by default. That breaks certain tracing scenarios by
> adding a superfluous ENDBR64 instruction before the fentry call, for
> functions which can be called indirectly.
>
> CET instrumentation isn't currently necessary in the kernel, as CET is
> only supported in user space. Disable it unconditionally and move it
> into the x86's Makefile as CET/CFI... enablement should be a per-arch
> decision anyway.
>
> [ bp: Massage and extend commit message. ]
>
> Fixes: 29be86d7f9cb ("kbuild: add -fcf-protection=none when using retpoline flags")
> Reported-by: Nikolay Borisov <nborisov@suse.com>
> Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
> Signed-off-by: Borislav Petkov <bp@suse.de>
> Reviewed-by: Nikolay Borisov <nborisov@suse.com>
> Tested-by: Nikolay Borisov <nborisov@suse.com>
> Cc: <stable@vger.kernel.org>
> Cc: Seth Forshee <seth.forshee@canonical.com>
> Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
> Link: https://lkml.kernel.org/r/20210128215219.6kct3h2eiustncws@treble
>
> Makefile | 6 ------
> arch/x86/Makefile | 3 +++
> 2 files changed, 3 insertions(+), 6 deletions(-)
>
> --- end ---
>
> On Sun, Feb 07, 2021 at 06:31:22PM -0500, Stuart Little wrote:
> > I am trying to compile on an x86_64 host for a 32-bit system; my config is at
> >
> > https://termbin.com/v8jl
> >
> > I am getting numerous errors of the form
> >
> > ./include/linux/kasan-checks.h:17:1: error: ‘-mindirect-branch’ and ‘-fcf-protection’ are not compatible
> >
> > and
> >
> > ./include/linux/kcsan-checks.h:143:6: error: ‘-mindirect-branch’ and ‘-fcf-protection’ are not compatible
> >
> > and
> >
> > ./arch/x86/include/asm/arch_hweight.h:16:1: error: ‘-mindirect-branch’ and ‘-fcf-protection’ are not compatible
> >
> > (those include files indicated whom I should add to this list; apologies if this reaches you in error).
> >
> > The full log of the build is at
> >
> > https://termbin.com/wbgs
> >
> > ---
> >
> > 5.11.0-rc6 built fine last week on this same setup.

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