Re: [PATCH 13/18] arm64: preserve x18 when CPU is suspended

[Mark Rutland]

On Fri, Oct 18, 2019 at 09:10:28AM -0700, Sami Tolvanen wrote:
> Don't lose the current task's shadow stack when the CPU is suspended.
> 
> Signed-off-by: Sami Tolvanen <samitolvanen@xxxxxxxxxx>
> ---
>  arch/arm64/mm/proc.S | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/arch/arm64/mm/proc.S b/arch/arm64/mm/proc.S
> index fdabf40a83c8..9a8bd4bc8549 100644
> --- a/arch/arm64/mm/proc.S
> +++ b/arch/arm64/mm/proc.S
> @@ -73,6 +73,9 @@ alternative_endif
>  	stp	x8, x9, [x0, #48]
>  	stp	x10, x11, [x0, #64]
>  	stp	x12, x13, [x0, #80]
> +#ifdef CONFIG_SHADOW_CALL_STACK
> +	stp	x18, xzr, [x0, #96]
> +#endif

This should have a corresponding change to cpu_suspend_ctx in
<asm/suspend.h>. Otherwise we're corrupting a portion of the stack.

Mark.

>  	ret
>  ENDPROC(cpu_do_suspend)
>  
> @@ -89,6 +92,9 @@ ENTRY(cpu_do_resume)
>  	ldp	x9, x10, [x0, #48]
>  	ldp	x11, x12, [x0, #64]
>  	ldp	x13, x14, [x0, #80]
> +#ifdef CONFIG_SHADOW_CALL_STACK
> +	ldp	x18, x19, [x0, #96]
> +#endif
>  	msr	tpidr_el0, x2
>  	msr	tpidrro_el0, x3
>  	msr	contextidr_el1, x4
> -- 
> 2.23.0.866.gb869b98d4c-goog
>