Re: [tip:x86/seves] BUILD SUCCESS WITH WARNING e6eb15c9ba3165698488ae5c34920eea20eaa38e

Marco Elver
2020-09-15T18:17:55Z

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:
> >
> > On Tue, Sep 15, 2020 at 12:02:48PM -0500, Josh Poimboeuf wrote:
> > > If somebody can share the .o file, I can take a look.
> >
> > If only I could reproduce...
> >
> > So I built:
> >
> > /home/share/src/llvm/tc-build/install/bin/clang-12 --version
> > ClangBuiltLinux clang version 12.0.0 (https://github.com/llvm/llvm-project 74a9c6d7e1c49cd0e3a8e8072b8aa03f7a84caff)
> > Target: x86_64-unknown-linux-gnu
> > Thread model: posix
> > InstalledDir: /home/share/src/llvm/tc-build/install/bin
> >
> > and I don't trigger that warning even with that compiler.
> >
> > What I do get is a lot of those pairs:
> >
> > 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)?

Thanks,
-- Marco