linux-kernel - Re: gcc-8 objtool warnings

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Date:   Tue, 19 Sep 2017 22:43:31 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Josh Poimboeuf <jpoimboe@...hat.com>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: gcc-8 objtool warnings

On Tue, Sep 19, 2017 at 9:52 PM, Josh Poimboeuf <jpoimboe@...hat.com> wrote:
> On Mon, Sep 11, 2017 at 04:34:52PM +0200, Arnd Bergmann wrote:
>> On Thu, Aug 24, 2017 at 9:19 PM, Josh Poimboeuf <jpoimboe@...hat.com> wrote:
>> 1. one configuration causing tons of warnings, on most compiler
>>   versions (4.9 and newer), and even a couple of "unreachable
>>   instruction warnings on gcc-4.3.
>>
>> arch/x86/mm/pageattr.o: warning: objtool: set_memory_x()+0x3a: call
>> without frame pointer save/setup
>> security/keys/keyring.o: warning: objtool: keyring_read()+0x70: leave
>> instruction with modified stack frame
>> arch/x86/events/intel/pt.o: warning: objtool:
>> pt_event_addr_filters_sync uses BP as a scratch register
>
> I downloaded the tarball, and I see configs/logs for the other problems,
> but not for this one.  Did you forget to attach it, or did I miss it?

I think what I ended up doing was to take the smallest files for that
configuration and packed them up, but the warnings I listed in the
mail don't match the ones for those files. However, it seems the
0xEBFDB964_defconfig/log file got corrupted.

I've uploaded a new copy to http://paste.ubuntu.com/25574959/ now.

I've also experimented with other compiler versions
in the meantime and ran into similar problems on those version but did
not bother to take detailed notes about them since they are likely just
variants of the ones I already reported. If you can work around the
warnings I reported here, I can rerun with all compilers I have to
see if anything else shows up.

      Arnd