Re: [PATCH v6 00/15] x86-64: Stack protector and percpu improvements

[Ard Biesheuvel]

On Thu, 20 Feb 2025 at 18:24, Brian Gerst <brgerst@xxxxxxxxx> wrote:
>
> On Thu, Feb 20, 2025 at 5:52 AM Ard Biesheuvel <ardb@xxxxxxxxxx> wrote:
> >
> > On Thu, 20 Feb 2025 at 11:46, Uros Bizjak <ubizjak@xxxxxxxxx> wrote:
> > >
> > > OTOH, we could simply do it your way and put stack canary at the
> > > beginning of pcpu_hot structure, with
> > >
> > > static_assert(offsetof(struct pcpu_hot, stack_canary) == 0));
> > >
> > > for good measure.
> >
> > I think this would be the most straight-forward if there are no other
> > locality concerns this might interfere with.
>
> I'd prefer it at the end of pcpu_hot, that way the disassembler
> doesn't latch on to the __stack_chk_guard symbol when referencing the
> other fields of pcpu_hot.
>

__stack_chk_guard would no longer exist, only __ref_stack_chk_guard,
which would be equal to pcpu_hot. We could just call that
__ref_pcpu_hot instead if it might cause confusion otherwise. (We
can't use pcpu_hot directly in -mstack-check-guard-symbol= for the
same reasons I had to add the indirection via __ref_stack_chk_guard)