iris/entry.S

	// The kernel stack.
	.lcomm kernel_stack, KERNEL_STACK_SIZE

	.globl run_idle
	.set noat

#define Index 0
#define Random 1
#define EntryLo0 2
#define EntryLo1 3
#define BadVAddr 8
#define EntryHi 10
#define Status 12
#define EPC 14

// register save positions in Thread
#define SAVE_PC (5 * 4)
#define SAVE_SP (SAVE_PC + 4)
#define SAVE_AT (SAVE_SP + 4)
#define SAVE_V0 (SAVE_AT + 4)
#define SAVE_V1 (SAVE_V0 + 4)
#define SAVE_A0 (SAVE_V1 + 4)
#define SAVE_A1 (SAVE_A0 + 4)
#define SAVE_A2 (SAVE_A1 + 4)
#define SAVE_A3 (SAVE_A2 + 4)
#define SAVE_T0 (SAVE_A3 + 4)
#define SAVE_T1 (SAVE_T0 + 4)
#define SAVE_T2 (SAVE_T1 + 4)
#define SAVE_T3 (SAVE_T2 + 4)
#define SAVE_T4 (SAVE_T3 + 4)
#define SAVE_T5 (SAVE_T4 + 4)
#define SAVE_T6 (SAVE_T5 + 4)
#define SAVE_T7 (SAVE_T6 + 4)
#define SAVE_T8 (SAVE_T7 + 4)
#define SAVE_T9 (SAVE_T8 + 4)
#define SAVE_S0 (SAVE_T9 + 4)
#define SAVE_S1 (SAVE_S0 + 4)
#define SAVE_S2 (SAVE_S1 + 4)
#define SAVE_S3 (SAVE_S2 + 4)
#define SAVE_S4 (SAVE_S3 + 4)
#define SAVE_S5 (SAVE_S4 + 4)
#define SAVE_S6 (SAVE_S5 + 4)
#define SAVE_S7 (SAVE_S6 + 4)
#define SAVE_GP (SAVE_S7 + 4)
#define SAVE_FP (SAVE_GP + 4)
#define SAVE_RA (SAVE_FP + 4)
#define SAVE_HI (SAVE_RA + 4)
#define SAVE_LO (SAVE_HI + 4)
#define SAVE_K0 (SAVE_LO + 4)
#define SAVE_K1 (SAVE_K0 + 4)

addr_000:
	// TLB refill
	// TODO: this should probably be assembly-only for speed reasons
	sw $ra, -0xd88($zero)
	bal save_regs
	la $t9, tlb_refill
	jr $t9
	nop
	.fill 0x100 - (. - addr_000)
addr_100:
	// Cache error
	sw $ra, -0xd88($zero)
	bal save_regs
	la $t9, cache_error
	jr $t9
	nop
	.fill 0x180 - (. - addr_000)
addr_180:
	// General exception
	sw $ra, -0xd88($zero)
	bal save_regs
	la $t9, exception
	jr $t9
	nop
	.fill 0x200 - (. - addr_000)
addr_200:
	// Interrupt
	sw $ra, -0xd88($zero)
	bal save_regs
	la $t9, interrupt
	jr $t9
	nop
	.fill 0x280 - (. - addr_000) - 16

	// space for save_regs: k0; current Thread; ra; gp
	.word 0			// -d90 == k0
	.word idle		// -d8c == current
	.word 0			// -d88	== ra
	.word _gp		// -d84 == gp

	.word idle_page		// 280
	.word 0x80000000	// 284  A pointer to the current page.
start_idle:			// 288
	// Wait for the next interrupt, then the first thread will be scheduled.
	// It is impractical to try to call schedule, because for that the
	// idle task would need to own capabilities.
	move $v0, $zero
	syscall
	nop
1:	wait
	b 1b
	nop

// TODO: save only fragile registers now, the rest on task switch.
kernel_exit:
	lw $k0, SAVE_PC($v0)
	mtc0 $k0, $EPC
	lw $k0, SAVE_LO($v0)
	lw $k1, SAVE_HI($v0)
	mtlo $k0
	mthi $k1
	lw $v1, SAVE_V1($v0)
	lw $a0, SAVE_A0($v0)
	lw $a1, SAVE_A1($v0)
	lw $a2, SAVE_A2($v0)
	lw $a3, SAVE_A3($v0)
	lw $t0, SAVE_T0($v0)
	lw $t1, SAVE_T1($v0)
	lw $t2, SAVE_T2($v0)
	lw $t3, SAVE_T3($v0)
	lw $t4, SAVE_T4($v0)
	lw $t5, SAVE_T5($v0)
	lw $t6, SAVE_T6($v0)
	lw $t7, SAVE_T7($v0)
	lw $t8, SAVE_T8($v0)
	lw $t9, SAVE_T9($v0)
	lw $s0, SAVE_S0($v0)
	lw $s1, SAVE_S1($v0)
	lw $s2, SAVE_S2($v0)
	lw $s3, SAVE_S3($v0)
	lw $s4, SAVE_S4($v0)
	lw $s5, SAVE_S5($v0)
	lw $s6, SAVE_S6($v0)
	lw $s7, SAVE_S7($v0)
	lw $fp, SAVE_FP($v0)
	lw $ra, SAVE_RA($v0)
	lw $at, SAVE_AT($v0)
	lw $k0, SAVE_K0($v0)
	lw $k1, SAVE_V0($v0)
	sw $k1, -0xd90($zero)
	lw $k1, SAVE_K1($v0)
	sw $v0, -0xd8c($zero)

	lw $sp, SAVE_SP($v0)
	lw $gp, SAVE_GP($v0)
	lw $v0, -0xd90($zero)
	eret

save_regs:
	sw $k0, -0xd90($zero)
	lw $k0, -0xd8c($zero)

	sw $at, SAVE_AT($k0)
	sw $gp, SAVE_GP($k0)
	sw $sp, SAVE_SP($k0)
	sw $fp, SAVE_FP($k0)

	sw $k1, SAVE_K1($k0)
	lw $k1, -0xd90($zero)
	sw $k1, SAVE_K0($k0)

	lw $k1, -0xd88($zero)
	sw $k1, SAVE_RA($k0)
	sw $v0, SAVE_V0($k0)
	sw $v1, SAVE_V1($k0)
	sw $a0, SAVE_A0($k0)
	sw $a1, SAVE_A1($k0)
	sw $a2, SAVE_A2($k0)
	sw $a3, SAVE_A3($k0)
	sw $t0, SAVE_T0($k0)
	sw $t1, SAVE_T1($k0)
	sw $t2, SAVE_T2($k0)
	sw $t3, SAVE_T3($k0)
	sw $t4, SAVE_T4($k0)
	sw $t5, SAVE_T5($k0)
	sw $t6, SAVE_T6($k0)
	sw $t7, SAVE_T7($k0)
	sw $t8, SAVE_T8($k0)
	sw $t9, SAVE_T9($k0)
	sw $s0, SAVE_S0($k0)
	sw $s1, SAVE_S1($k0)
	sw $s2, SAVE_S2($k0)
	sw $s3, SAVE_S3($k0)
	sw $s4, SAVE_S4($k0)
	sw $s5, SAVE_S5($k0)
	sw $s6, SAVE_S6($k0)
	sw $s7, SAVE_S7($k0)
	mfhi $v0
	mflo $v1
	sw $v0, SAVE_HI($k0)
	sw $v1, SAVE_LO($k0)
	mfc0 $k1, $EPC
	sw $k1, SAVE_PC($k0)

	lw $gp, -0xd84($zero)
	la $sp, kernel_stack + KERNEL_STACK_SIZE
	move $t9, $ra
	la $ra, kernel_exit
	jr $t9
	nop

	.globl thread0
	.globl thread1
	.globl thread2
	.balign 0x1000
thread0:
	.incbin "thread0"
	.balign 0x1000
thread1:
	.incbin "thread1"
thread2: