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

[Mark Kettenis]

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>
---
 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)
 
-- 
2.16.2