Merge pull request #229 from VisorFolks/bugfix/akashkollipara/228-avr…

…-irq-hndlr

<AVR8> SP computation fixed in ISR

src/arch/avr/8/common_5x_6/terravisor/asm.S

@@ -57,14 +57,12 @@ function arch_panic_handler
 	push	r26
 	push	r27
 	push	r30
-	push	r31
 .endm
 
 /**
  * CONTEXT_RESTORE - A macro that defines the context restore operation
  */
 .macro CONTEXT_RESTORE
-	pop	r31
 	pop	r30
 	pop	r27
 	pop	r26
@@ -106,11 +104,17 @@ function int_\id
  */
 function isr
 	CONTEXT_SAVE
-	push	r24
 	in	r22, IO_SPL
 	in	r23, IO_SPH
-	pop	r24
+	/*
+	 * SP at this location needs to be captured
+	 * and passed to interrupt_handler as SP post
+	 * decrements which results in SP pointing to
+	 * incorrect stack frame.
+	 */
+	push	r31
 	call	interrupt_handler
+	pop	r31
 	CONTEXT_RESTORE
 	pop	r24
 	reti