Re: [PATCH v6 22/25] x86/asm: annotate indirect jumps

Sami Tolvanen
2020-10-21T15:01:52Z

On Wed, Oct 21, 2020 at 1:56 AM Peter Zijlstra <peterz@infradead.org> wrote:
>
> On Tue, Oct 20, 2020 at 12:24:37PM -0700, Sami Tolvanen wrote:
> > > > Building allyesconfig with this series and LTO enabled, I still see
> > > > the following objtool warnings for vmlinux.o, grouped by source file:
> > > >
> > > > arch/x86/entry/entry_64.S:
> > > > __switch_to_asm()+0x0: undefined stack state
> > > > .entry.text+0xffd: sibling call from callable instruction with
> > > > modified stack frame
> > > > .entry.text+0x48: stack state mismatch: cfa1=7-8 cfa2=-1+0
> > >
> > > Not sure what this one's about, there's no OBJECT_FILES_NON_STANDARD?
> >
> > Correct, because with LTO, we won't have an ELF binary to process
> > until we compile everything into vmlinux.o, and at that point we can
> > no longer skip individual object files.
>
> I think what Josh was trying to say is; this file is subject to objtool
> on a normal build and does not generate warnings. So why would it
> generate warnings when subject to objtool as result of a vmlinux run
> (due to LTO or otherwise).

Ah, right. It also doesn't generate warnings when I build defconfig
with LTO, so clearly something confuses objtool here.

Sami