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

From: Brian Gerst
Date: Thu Feb 20 2025 - 12:47:50 EST


On Thu, Feb 20, 2025 at 12:36 PM Ard Biesheuvel <ardb@xxxxxxxxxx> wrote:
>
> 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)

That works for me.


Brian Gerst