* Make total stack size available as a symbol

* Implement SWI handler to enable/disable interrupts
* Implement event system to deal with kicking non-interrupt code

crt0.s

@@ -10,12 +10,24 @@
 	.equ	APB_DIVIDER,	4 /* 1, 2 or 4 */
 
 	.equ	UND_STACK_SIZE,	0x0004
-	.equ	SVC_STACK_SIZE,	0x0004
+	.equ	SVC_STACK_SIZE,	0x0010
 	.equ	ABT_STACK_SIZE,	0x0004
 	.equ	FIQ_STACK_SIZE,	0x0004
 	.equ	IRQ_STACK_SIZE,	0x0080
 	.equ	USR_STACK_SIZE,	0x0400
 
+
+.global _stack_size
+
+	.equ	_stack_size,  0
+	.equ	_stack_size, _stack_size + UND_STACK_SIZE
+	.equ	_stack_size, _stack_size + SVC_STACK_SIZE
+	.equ	_stack_size, _stack_size + ABT_STACK_SIZE
+	.equ	_stack_size, _stack_size + FIQ_STACK_SIZE
+	.equ	_stack_size, _stack_size + IRQ_STACK_SIZE
+	.equ	_stack_size, _stack_size + USR_STACK_SIZE
+
+
 # Processor definitions
 
 	.equ    Mode_USR,       0x10
@@ -174,7 +186,6 @@ lzi:
 
 # Undefined handlers can just spin for now
 undefined_handler:
-swi_handler:
 prefetch_abort_handler:
 data_abort_handler:
 fiq_handler:
@@ -182,5 +193,37 @@ fiq_handler:
 __back:
 	b	__back
 
+
+	.equ	SWI_MAX, 1
+
+swi_handler:
+	stmfd	sp!, {ip, lr}
+	ldr	ip, [lr, #-4]
+	bic	ip, #0xff000000
+
+	cmp	ip, #SWI_MAX
+	ldmhifd	sp!, {ip, pc}^
+
+	add	ip, pc, ip, lsl #2
+	ldr	pc, [ip]
+
+swi_branch_table:
+	.word	disable_interrupts
+	.word	enable_interrupts
+
+
+disable_interrupts:
+	mrs	ip, SPSR
+	orr	ip, ip, #I_Bit
+	msr	SPSR_c,ip
+	ldmfd	sp!, {ip, pc}^
+
+enable_interrupts:
+	mrs	ip, SPSR
+	bic	ip, ip, #I_Bit
+	msr	SPSR_c,ip
+	ldmfd	sp!, {ip, pc}^
+
+
 .endfunc
 .end