1 files changed, 103 insertions, 0 deletions
diff --git a/asm/crt0.s b/asm/crt0.s
new file mode 100644
index 0000000..fe1f127
--- /dev/null
+++ b/asm/crt0.s
@@ -0,0 +1,103 @@
+	.include "constants/gba_constants.inc"
+
+	.syntax unified
+
+	.global Start
+
+	.text
+
+	.arm
+
+Start: @ 8000000
+	b Init
+
+	.include "asm/rom_header.inc"
+
+	.arm
+	.align 2, 0
+	.global Init
+Init: @ 80000C0
+	mov r0, PSR_IRQ_MODE
+	msr cpsr_cf, r0
+	ldr sp, sp_irq
+	mov r0, PSR_SYS_MODE
+	msr cpsr_cf, r0
+	ldr sp, sp_sys
+	ldr r1, =INTR_VECTOR
+	adr r0, IntrMain
+	str r0, [r1]
+	ldr r1, =AgbMain
+	mov lr, pc
+	bx r1
+	b Init
+
+	.align 2, 0
+sp_sys: .word IWRAM_END - 0x100
+sp_irq: .word IWRAM_END - 0x60
+
+	.pool
+
+	.arm
+	.align 2, 0
+	.global IntrMain
+IntrMain: @ 8000104
+	mov r3, REG_BASE
+	add r3, r3, 0x200
+	ldr r2, [r3, OFFSET_REG_IE - 0x200]
+	ldrh r1, [r3, OFFSET_REG_IME - 0x200]
+	mrs r0, spsr
+	stmdb sp!, {r0-r3,lr}
+	mov r0, 1
+	strh r0, [r3, OFFSET_REG_IME - 0x200]
+	and r1, r2, r2, lsr 16
+	mov r12, 0
+	ands r0, r1, INTR_FLAG_SERIAL | INTR_FLAG_TIMER3
+	bne IntrMain_FoundIntr
+	add r12, r12, 0x4
+	ands r0, r1, INTR_FLAG_VBLANK
+	bne IntrMain_FoundIntr
+	add r12, r12, 0x4
+	ands r0, r1, INTR_FLAG_VCOUNT
+	bne IntrMain_FoundIntr
+	add r12, r12, 0x4
+	ands r0, r1, INTR_FLAG_TIMER2
+	bne IntrMain_FoundIntr
+	add r12, r12, 0x4
+	ands r0, r1, INTR_FLAG_TIMER3
+	bne IntrMain_FoundIntr
+	add r12, r12, 0x4
+	ands r0, r1, INTR_FLAG_GAMEPAK
+	strbne r0, [r3, OFFSET_REG_SOUNDCNT_X - 0x200]
+IntrMain_Loop:
+	bne IntrMain_Loop
+IntrMain_FoundIntr:
+	strh r0, [r3, OFFSET_REG_IF - 0x200]
+	mov r1, INTR_FLAG_GAMEPAK | INTR_FLAG_SERIAL
+	bic r2, r2, r0
+	and r1, r1, r2
+	strh r1, [r3, OFFSET_REG_IE - 0x200]
+	mrs r3, cpsr
+	bic r3, r3, PSR_I_BIT | PSR_F_BIT | PSR_MODE_MASK
+	orr r3, r3, PSR_SYS_MODE
+	msr cpsr_cf, r3
+	ldr r1, =gIntrTable
+	add r1, r1, r12
+	ldr r0, [r1]
+	stmdb sp!, {lr}
+	adr lr, IntrMain_RetAddr
+	bx r0
+IntrMain_RetAddr:
+	ldmia sp!, {lr}
+	mrs r3, cpsr
+	bic r3, r3, PSR_I_BIT | PSR_F_BIT | PSR_MODE_MASK
+	orr r3, r3, PSR_I_BIT | PSR_IRQ_MODE
+	msr cpsr_cf, r3
+	ldmia sp!, {r0-r3,lr}
+	strh r2, [r3, OFFSET_REG_IE - 0x200]
+	strh r1, [r3, OFFSET_REG_IME - 0x200]
+	msr spsr_cf, r0
+	bx lr
+
+	.pool
+
+	.align 2, 0 @ Don't pad with nop.