iris/mips/entry.S

// Iris: micro-kernel for a capability-based operating system.
// mips/entry.S: Routines which are entered from user space.
// Copyright 2009 Bas Wijnen <wijnen@debian.org>
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program.  If not, see <http://www.gnu.org/licenses/>.

	// The kernel stack.
	.lcomm kernel_stack, KERNEL_STACK_SIZE

	.globl run_idle
	.globl directory
	.set noat
	.set noreorder

#define ARCH
#define ASM
#define __KERNEL
#include "arch.hh"

addr_000:
#if 0
	// TLB refill
	bne $zero, $k1, slow_refill
	nop
	bne $zero, $k0, slow_refill
	lw $k1, -0xd94($zero)
	mfc0 $k0, $CP0_ENTRY_HI
	srl $k0, $k0, 19
	and $k0, $k0, 0x3fc
	addu $k0, $k0, $k1
	beq $zero, $k0, zero_refill
	lw $k0, 0($k0)
	mfc0 $k1, $CP0_ENTRY_HI
	srl $k1, $k1, 10
	and $k1, $k1, 0x1f8
	add $k0, $k0, $k1
	lw $k1, 0($k0)
	mtc0 $k1, $CP0_ENTRY_LO0
	lw $k1, 4($k0)
	mtc0 $k1, $CP0_ENTRY_LO1
1:	tlbwr
	move $zero, $k0
	move $zero, $k1
	eret

zero_refill:
	mtc0 $zero, $CP_ENTRY_LO0
	b 1b
	mtc0 $zero, $CP_ENTRY_LO1

slow_refill:
	move $k1, $zero
#endif
	sw $ra, -0xd88($zero)
	bal save_regs
	nop
	la $t9, tlb_refill
	jr $t9
	nop
	.fill 0x100 - (. - addr_000)
addr_100:
	// Cache error
	sw $ra, -0xd88($zero)
	bal save_regs
	nop
	la $t9, cache_error
	jr $t9
	nop
	.fill 0x180 - (. - addr_000)
addr_180:
	// General exception
	sw $ra, -0xd88($zero)
	bal save_regs
	nop
	la $t9, exception
	jr $t9
	nop
	.fill 0x200 - (. - addr_000) - 8
	.word 0x0000001e	// 1f8	EntryLo data for idle page.
	.word 0x80000000	// 1fc  A pointer to the current page.
addr_200:
	// Interrupt
	sw $ra, -0xd88($zero)
	bal save_regs
	nop
	la $t9, interrupt
	jr $t9
	nop
	.fill 0x280 - (. - addr_000) - 20

directory:
	.word 0			// -d94 == directory
	// space for save_regs
	.word 0			// -d90 == k0
	.word idle		// -d8c == current
	.word 0			// -d88	== ra
	.word _gp		// -d84 == gp

start_idle:			// 280
	// 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:
#ifndef NDEBUG
	// Allow interrupts to set EPC and friends.
	mfc0 $k0, $CP0_STATUS
	ori $k0, $k0, 0xff13
	mtc0 $k0, $CP0_STATUS
#endif
	lw $k0, SAVE_PC($v0)
	mtc0 $k0, $CP0_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, $CP0_EPC
	sw $k1, SAVE_PC($k0)

	lw $gp, -0xd84($zero)
	la $sp, kernel_stack + KERNEL_STACK_SIZE

#ifndef NDEBUG
	// Allow interrupts to set EPC and friends.
	mfc0 $k0, $CP0_STATUS
	andi $k0, $k0, 0xff00
	mtc0 $k0, $CP0_STATUS
#endif

	move $t9, $ra
	la $ra, kernel_exit
	jr $t9
	nop

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