mirror of
https://github.com/italicsjenga/gba.git
synced 2024-12-23 19:01:30 +11:00
130 lines
3.2 KiB
ArmAsm
130 lines
3.2 KiB
ArmAsm
.arm
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__start:
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b .Linit
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@ ROM header
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.byte 0x24,0xff,0xae,0x51,0x69,0x9a,0xa2,0x21,0x3d,0x84,0x82,0x0a,0x84,0xe4,0x09,0xad
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.byte 0x11,0x24,0x8b,0x98,0xc0,0x81,0x7f,0x21,0xa3,0x52,0xbe,0x19,0x93,0x09,0xce,0x20
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.byte 0x10,0x46,0x4a,0x4a,0xf8,0x27,0x31,0xec,0x58,0xc7,0xe8,0x33,0x82,0xe3,0xce,0xbf
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.byte 0x85,0xf4,0xdf,0x94,0xce,0x4b,0x09,0xc1,0x94,0x56,0x8a,0xc0,0x13,0x72,0xa7,0xfc
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.byte 0x9f,0x84,0x4d,0x73,0xa3,0xca,0x9a,0x61,0x58,0x97,0xa3,0x27,0xfc,0x03,0x98,0x76
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.byte 0x23,0x1d,0xc7,0x61,0x03,0x04,0xae,0x56,0xbf,0x38,0x84,0x00,0x40,0xa7,0x0e,0xfd
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.byte 0xff,0x52,0xfe,0x03,0x6f,0x95,0x30,0xf1,0x97,0xfb,0xc0,0x85,0x60,0xd6,0x80,0x25
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.byte 0xa9,0x63,0xbe,0x03,0x01,0x4e,0x38,0xe2,0xf9,0xa2,0x34,0xff,0xbb,0x3e,0x03,0x44
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.byte 0x78,0x00,0x90,0xcb,0x88,0x11,0x3a,0x94,0x65,0xc0,0x7c,0x63,0x87,0xf0,0x3c,0xaf
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.byte 0xd6,0x25,0xe4,0x8b,0x38,0x0a,0xac,0x72,0x21,0xd4,0xf8,0x07
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@ game title
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.byte 0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00
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@ game code
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.byte 0x00,0x00,0x00,0x00
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@ maker code
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.byte 0x00,0x00
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.byte 0x96
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@ main unit code
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.byte 0x00
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@ device type (0x00 retail, 0x80 debug)
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.byte 0x00
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@ reserved
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.byte 0x00,0x00,0x00,0x00,0x00,0x00,0x00
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@ software version
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.byte 0x00
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@ complement check
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.byte 0x51
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@ reserved area
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.space 2
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.Linit:
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@ Set address of user IRQ handler
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ldr r0, =MainIrqHandler
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ldr r1, =0x03FFFFFC
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str r0, [r1]
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@ set IRQ stack pointer
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mov r0, #0x12
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msr CPSR_c, r0
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ldr sp, =0x3007fa0
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@ set user stack pointer
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mov r0, #0x1f
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msr CPSR_c, r0
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ldr sp, =0x3007f00
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@ copy .data section to IWRAM
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ldr r0, =__data_lma @ source address
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ldr r1, =__data_start @ destination address
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ldr r2, =__data_end
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subs r2, r1 @ length
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@ these instructions are only executed if r2 is nonzero
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@ (i.e. don't bother copying an empty .data section)
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addne r2, #3
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asrne r2, #2
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addne r2, #0x04000000
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swine 0xb0000
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@ jump to user code
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ldr r0, =main
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bx r0
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.arm
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.global MainIrqHandler
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.align 4, 0
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MainIrqHandler:
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@ Load base I/O register address
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mov r2, #0x04000000
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add r2, r2, #0x200
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@ Save IRQ stack pointer and IME
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mrs r0, spsr
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ldrh r1, [r2, #8]
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stmdb sp!, {r0-r2,lr}
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@ Disable all interrupts by writing to IME
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@ r2 (0x4000200) can be used as we only care about bit 0 being unset
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strh r2, [r2, #8]
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@ Acknowledge all received interrupts that were enabled in IE
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ldr r3, [r2, #0]
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and r0, r3, r3, lsr #16
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strh r0, [r2, #2]
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@ Switch from IRQ mode to system mode
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@ cpsr_c = 0b000_10010u8 | 0b000_01101u8
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mrs r2, cpsr
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orr r2, r2, #0xD
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msr cpsr_c, r2
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@ Jump to user specified IRQ handler
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ldr r2, =__IRQ_HANDLER
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ldr r1, [r2]
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stmdb sp!, {lr}
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adr lr, .Lreturn
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bx r1
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.Lreturn:
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ldmia sp!, {lr}
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@ Switch from ??? mode to IRQ mode, disable IRQ
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@ cpsr_c = ( !0b000_01101u8 & cpsr_c ) | 0b100_10010u8
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mrs r2, cpsr
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bic r2, r2, #0xD
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orr r2, r2, #0x92
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msr cpsr_c, r2
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@ Restore IRQ stack pointer and IME
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ldmia sp!, {r0-r2,lr}
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strh r1, [r2, #8]
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msr spsr_cf, r0
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@ Return to BIOS IRQ handler
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bx lr
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.pool
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