[U-Boot] [PATCH 1/3] ARM: HYP/non-sec: save and restore stack

[Alexander Graf]

On 12.06.18 19:27, Mark Kettenis wrote:
> The current code that switches into HYP mode doesn't bother to set
> up a stack for HYP mode.  This doesn't work for EFI applications
> as they expect a usable stack.  Fix this by saving the stack
> pointer before switching and use it to set SP_hyp from monitor.
> This restores the stack pointer when we drop into HYP mode.
> 
> Signed-off-by: Mark Kettenis <kettenis at openbsd.org>

Can we be sure that the stack in MON is usable from HYP?

Alex

> ---
>  arch/arm/cpu/armv7/nonsec_virt.S | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/arm/cpu/armv7/nonsec_virt.S b/arch/arm/cpu/armv7/nonsec_virt.S
> index 56bdba1d38..246d817340 100644
> --- a/arch/arm/cpu/armv7/nonsec_virt.S
> +++ b/arch/arm/cpu/armv7/nonsec_virt.S
> @@ -52,9 +52,9 @@ _secure_monitor:
>  	bl	psci_stack_setup
>  
>  	@ Configure the PSCI backend
> -	push	{r0, r1, r2, ip}
> +	push	{r0, r1, r2, r3, ip}
>  	bl	psci_arch_init
> -	pop	{r0, r1, r2, ip}
> +	pop	{r0, r1, r2, r3, ip}
>  #endif
>  
>  #ifdef CONFIG_ARM_ERRATA_773022
> @@ -80,6 +80,7 @@ _secure_monitor:
>  #ifdef CONFIG_ARMV7_VIRT
>  	orreq	r5, r5, #0x100			@ allow HVC instruction
>  	moveq	r6, #HYP_MODE			@ Enter the kernel as HYP
> +	msreq	sp_hyp, r3			@ restore saved stack
>  #endif
>  
>  	mcr	p15, 0, r5, c1, c1, 0		@ write SCR (with NS bit set)
> @@ -106,6 +107,7 @@ ENTRY(_do_nonsec_entry)
>  	mov	r0, r1
>  	mov	r1, r2
>  	mov	r2, r3
> +	mov	r3, sp
>  	smc	#0
>  ENDPROC(_do_nonsec_entry)
>  
>