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SubjectRe: [tip:x86/seves] BUILD SUCCESS WITH WARNING e6eb15c9ba3165698488ae5c34920eea20eaa38e
On Tue, Sep 15, 2020 at 10:02 AM Josh Poimboeuf <jpoimboe@redhat.com> wrote:
>
> On Tue, Sep 15, 2020 at 06:05:54PM +0200, Borislav Petkov wrote:
> > On Tue, Sep 15, 2020 at 10:18:16PM +0800, Rong Chen wrote:
> > > On Tue, Sep 15, 2020 at 03:55:19PM +0200, Borislav Petkov wrote:
> > > > On Tue, Sep 15, 2020 at 09:42:56PM +0800, kernel test robot wrote:
> > > > > tree/branch: https://git.kernel.org/pub/scm/linux/kernel/git/peterz/queue.git x86/seves
> > > > > branch HEAD: e6eb15c9ba3165698488ae5c34920eea20eaa38e KVM: nSVM: Avoid freeing uninitialized pointers in svm_set_nested_state()
> > > > >
> > > > > Warning in current branch:
> > > > >
> > > > > arch/x86/kernel/sev-es.o: warning: objtool: ist_exc_vmm_communication()+0x12: unreachable instruction
> > > > >
> > > > > Warning ids grouped by kconfigs:
> > > > >
> > > > > clang_recent_errors
> > > > > `-- x86_64-randconfig-r001-20200913
> > > > > `-- arch-x86-kernel-sev-es.o:warning:objtool:ist_exc_vmm_communication():unreachable-instruction
> >
> > Ok, I can't trigger this with gcc-9, gcc-10 and clang-10.
> >
> > .config below says clang-12 so it could be some experimental
> > bug^Wfeature :)
> >
> > peterz says this has been fixed by:
> >
> > 318af7b80b6a ("Revert "kbuild: use -flive-patching when CONFIG_LIVEPATCH is enabled"")
> >
> > but that was reportedly for gcc.
> >
> > Lemme Cc the people of interest and leave the rest in here for
> > reference. Note that CONFIG_LIVEPATCH is enabled in that .config.
>
> If somebody can share the .o file, I can take a look.

I'm cc'ed on and read every report from 0day bot from builds with
Clang. I started noticing a few randconfigs getting this report from
objtool. I had filed a bug to follow up on this:
https://github.com/ClangBuiltLinux/linux/issues/1148. They all seem
to be coming from randconfigs. I've not yet had the time to bisect
configs to isolate which config this is coming from, but I wouldn't be
surprised if it was UBSAN.

--
Thanks,
~Nick Desaulniers

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