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Date:   Wed, 16 Sep 2020 10:30:32 +0200
From:   peterz@infradead.org
To:     Marco Elver <elver@google.com>
Cc:     Josh Poimboeuf <jpoimboe@redhat.com>,
        Borislav Petkov <bp@alien8.de>,
        Nick Desaulniers <ndesaulniers@google.com>,
        Rong Chen <rong.a.chen@intel.com>,
        kernel test robot <lkp@intel.com>,
        "Li, Philip" <philip.li@intel.com>, x86-ml <x86@kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        clang-built-linux <clang-built-linux@googlegroups.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Kees Cook <keescook@chromium.org>,
        Masahiro Yamada <masahiroy@kernel.org>,
        kasan-dev <kasan-dev@googlegroups.com>
Subject: Re: [tip:x86/seves] BUILD SUCCESS WITH WARNING
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On Tue, Sep 15, 2020 at 08:09:16PM +0200, Marco Elver wrote:
> On Tue, 15 Sep 2020 at 19:40, Nick Desaulniers <ndesaulniers@google.com> wrote:
> > On Tue, Sep 15, 2020 at 10:21 AM Borislav Petkov <bp@alien8.de> wrote:

> > > init/calibrate.o: warning: objtool: asan.module_ctor()+0xc: call without frame pointer save/setup
> > > init/calibrate.o: warning: objtool: asan.module_dtor()+0xc: call without frame pointer save/setup
> > > init/version.o: warning: objtool: asan.module_ctor()+0xc: call without frame pointer save/setup
> > > init/version.o: warning: objtool: asan.module_dtor()+0xc: call without frame pointer save/setup
> > > certs/system_keyring.o: warning: objtool: asan.module_ctor()+0xc: call without frame pointer save/setup
> > > certs/system_keyring.o: warning: objtool: asan.module_dtor()+0xc: call without frame pointer save/setup
> 
> This one also appears with Clang 11. This is new I think because we
> started emitting ASAN ctors for globals redzone initialization.
> 
> I think we really do not care about precise stack frames in these
> compiler-generated functions. So, would it be reasonable to make
> objtool ignore all *san.module_ctor and *san.module_dtor functions (we
> have them for ASAN, TSAN, MSAN)?

The thing is, if objtool cannot follow, it cannot generate ORC data and
our unwinder cannot unwind through the instrumentation, and that is a
fail.

Or am I missing something here?