Re: [PATCH v3 16/16] objtool,x86: Rewrite retpoline thunk calls

[Nathan Chancellor]

On 6/8/2021 10:22 AM, Peter Zijlstra wrote:
> On Tue, Jun 08, 2021 at 09:58:03AM -0700, Nathan Chancellor wrote:
> > On 6/7/2021 1:54 PM, 'Nick Desaulniers' via Clang Built Linux wrote:
> > > On Mon, Jun 7, 2021 at 2:46 AM Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
> > > >
> > >
> > > Thanks, the below diff resolves the linker error reported in
> > > https://github.com/ClangBuiltLinux/linux/issues/1388
> > >
> > > Both readelf implementations seem happy with the results, too.
> > >
> > > Tested-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx>
> > >
> > > Nathan,
> > > Can you please test the below diff and see if that resolves your boot
> > > issue reported in:
> > > https://github.com/ClangBuiltLinux/linux/issues/1384
> >
> > Unfortunately, it does not appear to resolve that issue.
> >
> > $ git log -2 --decorate=no --oneline
> > eea6a9d6d277 Peter's fix
> > 614124bea77e Linux 5.13-rc5
> >
> > $ strings /mnt/c/Users/natec/Linux/kernel-investigation | grep microsoft
> > 5.13.0-rc5-microsoft-standard-WSL2-00001-geea6a9d6d277
> > (nathan@archlinux-ax161) #3 SMP Tue Jun 8 09:46:19 MST 2021
> >
> > My VM still never makes it to userspace.
>
> Since it's a VM, can you use the gdb-stub to ask it where it's stuck?

Unfortunately, this is the VM provided by the Windows Subsystem for 
Linux so examining it is nigh-impossible :/ I am considering bisecting 
the transforms that objtool does to try and figure out the one that 
causes the machine to fail to boot or try to reproduce in a different 
hypervisor, unless you have any other ideas.

Cheers,
Nathan