gpsp/bios/source/core.s

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@---------------------------------------------------------------------------------
.section ".init"
@---------------------------------------------------------------------------------
.global _start
.type _start STT_FUNC
.align 4
.arm
@---------------------------------------------------------------------------------
_start:
@---------------------------------------------------------------------------------
b reset_vector @ 0x00 Reset
b reserved_vector @ 0x04 Undefined
b swi_vector @ 0x08 SWI
b reserved_vector @ 0x0C Abort Prefetch
b reserved_vector @ 0x10 Abort Data
b reserved_vector @ 0x14 Reserved
b irq_vector @ 0x18 IRQ
b irq_vector @ 0x1C FIQ
@---------------------------------------------------------------------------------
irq_vector:
@---------------------------------------------------------------------------------
@ Save these registers, IRQ functions will be allowed to modify them w/o
@ saving.
stmdb sp!, { r0 - r3, r12, lr }
@ Pointer to IRQ handler is at 0x03FFFFFC (mirrored WRAM)
mov r0, #0x04000000
@ Store return address and branch to handler
mov lr, pc
ldr pc, [ r0, #-4 ]
@ Return from IRQ
ldmia sp!, { r0 - r3, r12, lr }
subs pc, lr, #4
@---------------------------------------------------------------------------------
reset_vector: @This isn't required if not booting from bios
@---------------------------------------------------------------------------------
mov r0, #0xDF
msr cpsr_cf, r0
@Disable Interrupts IME=0
mov r3, #0x04000000
strb r3, [r3,#0x208]
@Setup stacks
bl init
mov r2, #1
strb r2, [r3,#0x208]
ldr r0, =DrawLogo
ldr lr, =swi_SoftReset
bx r0
@---------------------------------------------------------------------------------
reserved_vector: @Lets just infinite loop for now
@---------------------------------------------------------------------------------
b reserved_vector
@ SWI calling convention:
@ Parameters are passed in via r0 - r3
@ Called SWI can modify r0 - r3 (and return things here), r12, and r14.
@ They can't modify anything else.
@---------------------------------------------------------------------------------
swi_vector:
@---------------------------------------------------------------------------------
@ Save these as temporaries
stmdb sp!, { r11, r12, lr }
@ Load comment from SWI instruction, which indicates which SWI
@ to use.
ldrb r12, [lr,#-2]
adr r11, swi_branch_table
ldr r12, [r11,r12,lsl#2]
@ get SPSR and enter system mode, interrupts on
MRS R11, SPSR
@ This must be stacked and not just saved, because otherwise SWI won't
@ be reentrant, which can happen if you're waiting for interrupts and the
@ interrupt handler triggers the SWI.
stmfd sp!, {r11}
@ Set up new CPSR value
and r11, r11, #0x80
orr r11, r11, #0x1f
msr cpsr_cf, r11
@ We have to now save system-mode lr register as well
stmfd sp!, {r2, r3, lr}
@ Set return address
adr lr, swi_complete
@ Branch to SWI handler
bx r12
swi_complete:
@ Restore system mode lr
ldmfd sp!, {r2, r3, lr}
@ Go back to supervisor mode to get back to that stack
mov r12, #0xD3
msr cpsr_cf, r12
@ SPSR has to be restored because the transition to system mode broke it
ldmfd sp!, {r11}
msr spsr_cf, r11
@ Restore stuff we saved
ldmfd sp!, {r11,r12,lr}
@ Return from exception handler
movs pc, lr
@---------------------------------------------------------------------------------
swi_branch_table:
@---------------------------------------------------------------------------------
.word swi_SoftReset @ 0x00_SoftReset
.word swi_RegisterRamReset @ 0x01_RegisterRAMReset
.word swi_Halt @ 0x02_Halt
.word swi_Stop @ 0x03_Stop
.word swi_IntrWait @ 0x04_IntrWait
.word swi_VBlankIntrWait @ 0x05_VBlankIntrWait
.word swi_Div @ 0x06_Div
.word swi_DivARM @ 0x07_DivARM
.word swi_Sqrt @ 0x08_Sqrt
.word swi_ArcTan @ 0x09_ArcTan
.word swi_ArcTan2 @ 0x0A_ArcTan2
.word swi_CpuSet @ 0x0B_CPUSet
.word swi_CpuFastSet @ 0x0C_CPUFastSet
.word swi_GetBiosChecksum @ 0x0D_GetBiosChecksum
.word swi_BgAffineSet @ 0x0E_BgAffineSet
.word swi_ObjAffineSet @ 0x0F_ObjAffineSet
.word swi_BitUnPack @ 0x10_BitUnPack
.word swi_LZ77UnCompWram @ 0x11_LZ77UnCompWram
.word swi_LZ77UnCompVram @ 0x12_LZ77UnCompVram
.word swi_HuffUnComp @ 0x13_HuffUnComp
.word swi_RLUnCompWram @ 0x14_RLUnCompWram
.word swi_RLUnCompVram @ 0x15_RLUnCompVram
.word swi_Diff8bitUnFilterWram @ 0x16_Diff8bitUnFilterWram
.word swi_Diff8bitUnFilterVram @ 0x17_Diff8bitUnFilterVram
.word swi_Diff16bitUnFilter @ 0x18_Diff16bitUnFilter
.word swi_Invalid @ 0x19_SoundBiasChange
.word swi_Invalid @ 0x1A_SoundDriverInit
.word swi_Invalid @ 0x1B_SoundDriverMode
.word swi_Invalid @ 0x1C_SoundDriverMain
@ .word swi_SoundDriverMain @ 0x1C_SoundDriverMain
.word swi_Invalid @ 0x1D_SoundDriverVSync
.word swi_Invalid @ 0x1E_SoundChannelClear
.word swi_MidiKey2Freq @ 0x1F_MidiKey2Freq
.word swi_Invalid @ 0x20_MusicPlayerOpen
.word swi_Invalid @ 0x21_MusicPlayerStart
.word swi_Invalid @ 0x22_MusicPlayerStop
.word swi_MusicPlayerContinue @ 0x23_MusicPlayerContinue
.word swi_MusicPlayerFadeOut @ 0x24_MusicPlayerFadeOut
.word swi_Invalid @ 0x25_MultiBoot
.word swi_Invalid @ 0x26_HardReset
.word swi_CustomHalt @ 0x27_CustomHalt
.word swi_Invalid @ 0x28_SoundDriverVSyncOff
.word swi_Invalid @ 0x29_SoundDriverVSyncOn
.word swi_SoundGetJumpList @ 0x2A_SoundGetJumpList
@---------------------------------------------------------------------------------
.global swi_Invalid
.type swi_Invalid STT_FUNC
swi_Invalid:
@---------------------------------------------------------------------------------
@ Infinite loop for now
@b swi_Invalid
@ Do nothing for release builds
bx lr
@---------------------------------------------------------------------------------