Re: [PATCH v5 14/14] arm64: implement Shadow Call Stack

[Sami Tolvanen]

On Fri, Nov 15, 2019 at 7:20 AM Mark Rutland <mark.rutland@xxxxxxx> wrote:
>
> On Tue, Nov 05, 2019 at 03:56:08PM -0800, Sami Tolvanen wrote:
> > This change implements shadow stack switching, initial SCS set-up,
> > and interrupt shadow stacks for arm64.
>
> Each CPU also has an overflow stack, and two SDEI stacks, which should
> presumably be given their own SCS. SDEI is effectively a software-NMI,
> so it should almost certainly have the same treatement as IRQ.

Makes sense. I'll take a look at adding shadow stacks for the SDEI handler.

> Can we please fold this comment into the one above, and have:
>
>         /*
>          * The callee-saved regs (x19-x29) should be preserved between
>          * irq_stack_entry and irq_stack_exit.
>          */
>         .macro irq_stack_exit
>         mov     sp, x19
> #ifdef CONFIG_SHADOW_CALL_STACK
>         mov     x18, x20
> #endif
>         .endm

Sure, I'll change this in the next version.

Sami