[PATCH v4 1/5] gcc-plugins: arm-ssp: Prepare for THREAD_INFO_IN_TASK support

[Ard Biesheuvel]

On Wed, 15 Sept 2021 at 00:04, Linus Walleij <linus.walleij at linaro.org> wrote:
>
> Hi Ard,
>
> thanks for this patch series!
>
> On Mon, Sep 13, 2021 at 12:40 PM Ard Biesheuvel <ardb at kernel.org> wrote:
>
> >  config STACKPROTECTOR_PER_TASK
> >         bool "Use a unique stack canary value for each task"
> > -       depends on GCC_PLUGINS && STACKPROTECTOR && SMP && !XIP_DEFLATED_DATA
> > +       depends on GCC_PLUGINS && STACKPROTECTOR && THREAD_INFO_IN_TASK && !XIP_DEFLATED_DATA
> >         select GCC_PLUGIN_ARM_SSP_PER_TASK
>
> Am I reading this right that STACKPROTECTOR_PER_TASK
> was available for ARMv6 with SMP before this
> change and after this change it will only be available for
> ARMv7 since THREAD_INFO_IN_TASK which is now a dependency
> will only be available for ARMv7 (or ARMv6k)?
>

Yes. We could potentially keep the old code path in the plugin as
well, but what I would really prefer to do is get
-mstack-protector-guard=tls implemented in GCC, so we can phase out
the plugin entirely.

> I suppose this is a reasonable compromise, as I don't use it or need
> it on my ARM PB11MPCore and neither do I think the Oxnas router,
> but we should write this explicitly in the commit message.
>

OK, I will add this.