From: Wei Chen <wei.chen@xxxxxxx>
If we enable the SCTLR_ELx.SA, Arm64 stack pointer must be aligned to
16-byte before being used as base address. But some valid EL1 exceptions
don't guarantee that SP_EL1 was aligned when entering the exceptions.
Signed-off-by: Wei Chen <wei.chen@xxxxxxx>
Signed-off-by: Jia He <justin.he@xxxxxxx>
---
plat/kvm/arm/exceptions.S | 69 ++++++++++++++++++++++++++++++++-------
1 file changed, 57 insertions(+), 12 deletions(-)
diff --git a/plat/kvm/arm/exceptions.S b/plat/kvm/arm/exceptions.S
index e4a5c74..704bd0a 100644
--- a/plat/kvm/arm/exceptions.S
+++ b/plat/kvm/arm/exceptions.S
@@ -29,9 +29,51 @@
#include <uk/arch/lcpu.h>
#include <uk/asm.h>
+.macro EXCHANGE_SP_WITH_X0
+ add sp, sp, x0 // new_sp = sp + x0
+ sub x0, sp, x0 // new_x0 = new_sp - x0 = sp + x0 - x0 = sp
+ sub sp, sp, x0 // new_sp = new_sp - new_x0 = sp + x0 - sp = x0
+.endm
+
+.macro ALIGN_STACK
+ // First, exchange the SP with x0
+ EXCHANGE_SP_WITH_X0
+
+ // Check whether the stack is alignment
+ tst x0, #0xf
+ // If yes, save and go out. If not, align the stack
+ b.eq 0f
+
+ // Start to align the stack.
+
+ // We will use the x1 as temporary, save x1 to stack temporary
+ str x1, [x0]
+
+ // Align down sp to 16-byte, save old sp to aligned_sp[__SP_OFFSET]
+ bic x1, x0, #0xf
+ str x0, [x1, #__SP_OFFSET]
+
+ // Restore x1 before x0 is overridden
+ ldr x1, [x0]
+
+ // Save aligned_sp to x0
+ bic x0, x0, #0xf
+ b 1f
+0:
+ str x0, [x0, #__SP_OFFSET]
+1:
+ // Change back the SP from x0
+ EXCHANGE_SP_WITH_X0
+.endm
+
.macro ENTER_TRAP, el
sub sp, sp, #__TRAP_STACK_SIZE
+.if \el != 0
+ /* Force align the stack, and save SP to __SP_OFFSET */
+ ALIGN_STACK
+.endif
+
/* Save general purpose registers */
stp x0, x1, [sp, #16 * 0]
stp x2, x3, [sp, #16 * 1]
@@ -58,25 +100,17 @@
mrs x23, esr_el1
stp x22, x23, [sp, #16 * 16]
- /* Save stack pointer for lower level exception */
.if \el == 0
+ /* Save stack pointer for lower level exception */
mrs x18, sp_el0
-.else
- add x18, sp, #__TRAP_STACK_SIZE
+ str x18, [sp, #__SP_EL0_OFFSET]
.endif
- str x18, [sp, #16 * 17]
+
.endm
.macro LEAVE_TRAP, el
/* Mask IRQ to make sure restore would not be interrupted by IRQ */
msr daifset, #2
-
- /* Restore stack pointer for lower level exception */
- ldr x18, [sp, #16 * 17]
-.if \el == 0
- msr sp_el0, x18
-.endif
-
/* Restore pstate and exception status register */
ldp x22, x23, [sp, #16 * 16]
msr spsr_el1, x22
@@ -92,7 +126,6 @@
ldp x24, x25, [sp, #16 * 12]
ldp x22, x23, [sp, #16 * 11]
ldp x20, x21, [sp, #16 * 10]
- ldp x18, x19, [sp, #16 * 9]
ldp x16, x17, [sp, #16 * 8]
ldp x14, x15, [sp, #16 * 7]
ldp x12, x13, [sp, #16 * 6]
@@ -103,8 +136,20 @@
ldp x2, x3, [sp, #16 * 1]
ldp x0, x1, [sp, #16 * 0]
+.if \el == 0
+ /* Restore stack pointer for exception from EL0 */
+ ldr x18, [sp, #__SP_EL0_OFFSET]
+ msr sp_el0, x18
+.else
+ /* Restore stack pointer for exception from EL1 */
+ ldr x18, [sp, #__SP_OFFSET]
+ mov sp, x18
+.endif
add sp, sp, #__TRAP_STACK_SIZE
+ /* Restore x18,x19 */
+ ldp x18, x19, [sp, #16 * 9]
+
eret
.endm
