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References: <20210303170932.1838634-1-jthierry@redhat.com> <20210305235102.384950-1-ndesaulniers@google.com>
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From:   Nick Desaulniers <ndesaulniers@google.com>
Date:   Fri, 5 Mar 2021 16:04:07 -0800
Message-ID: <CAKwvOdmgRAJXVdaHAnZoYm-Y4Dt01CYxvsnJC6zaSwr5amRWBg@mail.gmail.com>
Subject: Re: [RFC PATCH v2 00/13] objtool: add base support for arm64
To:     Julien Thierry <jthierry@redhat.com>
Cc:     Ard Biesheuvel <ardb@kernel.org>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Josh Poimboeuf <jpoimboe@redhat.com>,
        Linux ARM <linux-arm-kernel@lists.infradead.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Masahiro Yamada <masahiroy@kernel.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Will Deacon <will@kernel.org>, ycote@redhat.com,
        Fangrui Song <maskray@google.com>,
        Bill Wendling <morbo@google.com>,
        Pete Swain <swine@google.com>,
        Yonghyun Hwang <yonghyun@google.com>,
        clang-built-linux <clang-built-linux@googlegroups.com>
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On Fri, Mar 5, 2021 at 3:51 PM Nick Desaulniers <ndesaulniers@google.com> wrote:
>
> (in response to
> https://lore.kernel.org/linux-arm-kernel/20210303170932.1838634-1-jthierry@redhat.com/
> from the command line)
>
> > Changes since v1[2]:
> > - Drop gcc plugin in favor of -fno-jump-tables
>
> Thank you for this!  I built+booted(under emulation) arm64 defconfig and built
> arm64 allmodconfig with LLVM=1 with this series applied.
>
> Tested-by: Nick Desaulniers <ndesaulniers@google.com>
>
> One thing I noticed was a spew of warnings for allmodconfig, like:
> init/main.o: warning: objtool: asan.module_ctor()+0xc: call without frame pointer save/setup
> init/main.o: warning: objtool: asan.module_dtor()+0xc: call without frame pointer save/setup
>
> I assume those are from the KASAN constructors. See also:
> https://github.com/ClangBuiltLinux/linux/issues/1238
>
> Can we disable HAVE_STACK_PROTECTOR if CC_IS_CLANG and CONFIG_KASAN is set,
> until we can resolve the above issue?

Ah, filtering the logs more, it looks like GCOV is has the same issue
KASAN does (known issue).  Here's a filtered log:
https://gist.github.com/nickdesaulniers/01358015b33bd16ccd7d951c4a8c44e7

I'm curious about the failure to decode certain instructions?

The stack state mismatches are what are valuable to me; we'll need
some help digging into those at some point.  The logs from defconfig
are clean.
-- 
Thanks,
~Nick Desaulniers