gba/crt0.s

129 lines
3.1 KiB
ArmAsm
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.arm
__start:
b .Linit
2019-06-02 22:27:35 +10:00
@ ROM header
.byte 0x24,0xff,0xae,0x51,0x69,0x9a,0xa2,0x21,0x3d,0x84,0x82,0x0a,0x84,0xe4,0x09,0xad
.byte 0x11,0x24,0x8b,0x98,0xc0,0x81,0x7f,0x21,0xa3,0x52,0xbe,0x19,0x93,0x09,0xce,0x20
.byte 0x10,0x46,0x4a,0x4a,0xf8,0x27,0x31,0xec,0x58,0xc7,0xe8,0x33,0x82,0xe3,0xce,0xbf
.byte 0x85,0xf4,0xdf,0x94,0xce,0x4b,0x09,0xc1,0x94,0x56,0x8a,0xc0,0x13,0x72,0xa7,0xfc
.byte 0x9f,0x84,0x4d,0x73,0xa3,0xca,0x9a,0x61,0x58,0x97,0xa3,0x27,0xfc,0x03,0x98,0x76
.byte 0x23,0x1d,0xc7,0x61,0x03,0x04,0xae,0x56,0xbf,0x38,0x84,0x00,0x40,0xa7,0x0e,0xfd
.byte 0xff,0x52,0xfe,0x03,0x6f,0x95,0x30,0xf1,0x97,0xfb,0xc0,0x85,0x60,0xd6,0x80,0x25
.byte 0xa9,0x63,0xbe,0x03,0x01,0x4e,0x38,0xe2,0xf9,0xa2,0x34,0xff,0xbb,0x3e,0x03,0x44
.byte 0x78,0x00,0x90,0xcb,0x88,0x11,0x3a,0x94,0x65,0xc0,0x7c,0x63,0x87,0xf0,0x3c,0xaf
.byte 0xd6,0x25,0xe4,0x8b,0x38,0x0a,0xac,0x72,0x21,0xd4,0xf8,0x07
@ game title
.byte 0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00
@ game code
.byte 0x00,0x00,0x00,0x00
@ maker code
.byte 0x00,0x00
.byte 0x96
@ main unit code
.byte 0x00
@ device type (0x00 retail, 0x80 debug)
.byte 0x00
@ reserved
.byte 0x00,0x00,0x00,0x00,0x00,0x00,0x00
@ software version
.byte 0x00
@ complement check
.byte 0x51
@ reserved area
.space 2
.Linit:
@ Set address of user IRQ handler
ldr r0, =MainIrqHandler
ldr r1, =0x03FFFFFC
str r0, [r1]
@ set IRQ stack pointer
mov r0, #0x12
msr CPSR_cf, r0
ldr sp, =0x3007fa0
@ set user stack pointer
mov r0, #0x1f
msr CPSR_cf, r0
ldr sp, =0x3007f00
@ copy .data section to IWRAM
ldr r0, =__data_lma @ source address
ldr r1, =__data_start @ destination address
ldr r2, =__data_end
sub r2, r2, r1
beq .Lskip @ don't try to copy an empty .data section
add r2, #3
mov r2, r2, asr #2 @ length (in words)
add r2, #0x04000000 @ copy by words
swi 0xb0000
.Lskip:
@ jump to user code
ldr r0, =main
bx r0
.arm
.global MainIrqHandler
.align 4, 0
MainIrqHandler:
@ Load base I/O register address
mov r2, #0x04000000
add r2, r2, #0x200
@ Save IRQ stack pointer and IME
mrs r0, spsr
ldrh r1, [r2, #8]
stmdb sp!, {r0-r2,lr}
@ Disable all interrupts by writing to IME
mov r0, #0
strh r0, [r2, #8]
@ Acknowledge all received interrupts that were enabled in IE
ldr r3, [r2, #0]
and r0, r3, r3, lsr #16
strh r0, [r2, #2]
@ Switch to system mode
mrs r2, cpsr
bic r2, r2, #0x1F
orr r2, r2, #0x1F
msr cpsr_cf, r2
@ Jump to user specified IRQ handler
ldr r2, =__IRQ_HANDLER
ldr r1, [r2]
stmdb sp!, {lr}
adr lr, .Lreturn
bx r1
.Lreturn:
ldmia sp!, {lr}
@ Switch to IRQ mode
mrs r2, cpsr
bic r2, r2, #0x1F
orr r2, r2, #0x92
msr cpsr_cf, r2
@ Restore IRQ stack pointer and IME
ldmia sp!, {r0-r2,lr}
strh r1, [r2, #8]
msr spsr_cf, r0
@ Return to BIOS IRQ handler
bx lr
.pool