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#

# Copyright (c) 2003-2004 Jakub Jermar

# All rights reserved.

#

# Redistribution and use in source and binary forms, with or without

# modification, are permitted provided that the following conditions

# are met:

#

# - Redistributions of source code must retain the above copyright

#   notice, this list of conditions and the following disclaimer.

# - Redistributions in binary form must reproduce the above copyright

#   notice, this list of conditions and the following disclaimer in the

#   documentation and/or other materials provided with the distribution.

# - The name of the author may not be used to endorse or promote products

#   derived from this software without specific prior written permission.

#

# THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR

# IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES

# OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.

# IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,

# INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT

# NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,

# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY

# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT

# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF

# THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

#

#include <arch/asm/regname.h>

#include <arch/mm/page.h>

#include <arch/asm/boot.h>

#include <arch/context_offset.h>

#include <arch/stack.h>

.text

.set noat

.set noreorder

.set nomacro

.global kernel_image_start

.global tlb_refill_entry

.global cache_error_entry

.global exception_entry

.global userspace_asm

# Which status bits should are thread-local

#define REG_SAVE_MASK 0x1f # KSU(UM), EXL, ERL, IE

# Save registers to space defined by \r

# We will change status: Disable ERL,EXL,UM,IE

# These changes will be automatically reversed in REGISTER_LOAD

# SP is NOT saved as part of these registers

.macro REGISTERS_STORE_AND_EXC_RESET r

	sw $at, EOFFSET_AT(\r)

	sw $v0, EOFFSET_V0(\r)

	sw $v1, EOFFSET_V1(\r)

	sw $a0, EOFFSET_A0(\r)

	sw $a1, EOFFSET_A1(\r)

	sw $a2, EOFFSET_A2(\r)

	sw $a3, EOFFSET_A3(\r)

	sw $t0, EOFFSET_T0(\r)

	sw $t1, EOFFSET_T1(\r)

	sw $t2, EOFFSET_T2(\r)

	sw $t3, EOFFSET_T3(\r)

	sw $t4, EOFFSET_T4(\r)

	sw $t5, EOFFSET_T5(\r)

	sw $t6, EOFFSET_T6(\r)

	sw $t7, EOFFSET_T7(\r)

	sw $t8, EOFFSET_T8(\r)

	sw $t9, EOFFSET_T9(\r)

	mflo $at

	sw $at, EOFFSET_LO(\r)

	mfhi $at

	sw $at, EOFFSET_HI(\r)

	sw $gp, EOFFSET_GP(\r)

	sw $ra, EOFFSET_RA(\r)

	sw $k1, EOFFSET_K1(\r)

	mfc0 $t0, $status

	mfc0 $t1, $epc

	and $t2, $t0, REG_SAVE_MASK	# Save only KSU,EXL,ERL,IE

	li $t3, ~(0x1f)

	and $t0, $t0, $t3		# Clear KSU,EXL,ERL,IE

	sw $t2,EOFFSET_STATUS(\r)

	sw $t1,EOFFSET_EPC(\r)

	mtc0 $t0, $status

.endm

.macro REGISTERS_LOAD r

	# Update only UM,EXR,IE from status, the rest

	# is controlled by OS and not bound to task

	mfc0 $t0, $status

	lw $t1,EOFFSET_STATUS(\r)

	li $t2, ~REG_SAVE_MASK		# Mask UM,EXL,ERL,IE

	and $t0, $t0, $t2

	or $t0, $t0, $t1		# Copy UM,EXL, ERL, IE from saved status

	mtc0 $t0, $status

	lw $v0, EOFFSET_V0(\r)

	lw $v1, EOFFSET_V1(\r)

	lw $a0, EOFFSET_A0(\r)

	lw $a1, EOFFSET_A1(\r)

	lw $a2, EOFFSET_A2(\r)

	lw $a3, EOFFSET_A3(\r)

	lw $t0, EOFFSET_T0(\r)

	lw $t1, EOFFSET_T1(\r)

	lw $t2, EOFFSET_T2(\r)

	lw $t3, EOFFSET_T3(\r)

	lw $t4, EOFFSET_T4(\r)

	lw $t5, EOFFSET_T5(\r)

	lw $t6, EOFFSET_T6(\r)

	lw $t7, EOFFSET_T7(\r)

	lw $t8, EOFFSET_T8(\r)

	lw $t9, EOFFSET_T9(\r)

	lw $gp, EOFFSET_GP(\r)

	lw $ra, EOFFSET_RA(\r)

	lw $k1, EOFFSET_K1(\r)

	lw $at, EOFFSET_LO(\r)

	mtlo $at

	lw $at, EOFFSET_HI(\r)

	mthi $at

	lw $at, EOFFSET_EPC(\r)

	mtc0 $at, $epc

	lw $at, EOFFSET_AT(\r)

	lw $sp, EOFFSET_SP(\r)

.endm

# Move kernel stack pointer address to register K0

# - if we are in user mode, load the appropriate stack

# address

.macro KERNEL_STACK_TO_K0

	# If we are in user mode

	mfc0 $k0, $status

	andi $k0, 0x10

	beq $k0, $0, 1f

	add $k0, $sp, 0

	# Move $k0 pointer to kernel stack

	lui $k0, %hi(supervisor_sp)

	ori $k0, $k0, %lo(supervisor_sp)

	# Move $k0 (superveisor_sp)

	lw $k0, 0($k0)

1:

.endm

.org 0x0

kernel_image_start:

	/* Load temporary stack */

	lui $sp, %hi(end_stack)

	ori $sp, $sp, %lo(end_stack)

	/* Not sure about this, but might

	   be needed for PIC code */

	lui $gp, 0x8000

	/* $a1 contains physical address of bootinfo_t */

	jal arch_pre_main

	nop

	j main_bsp

	nop

	.space TEMP_STACK_SIZE

end_stack:

tlb_refill_entry:

	j tlb_refill_handler

	nop

cache_error_entry:

	j cache_error_handler

	nop

exception_entry:

	j exception_handler

	nop

exception_handler:

	KERNEL_STACK_TO_K0

	sub $k0, REGISTER_SPACE

	sw $sp, EOFFSET_SP($k0)

	move $sp, $k0

	mfc0 $k0, $cause

	sra $k0, $k0, 0x2    # cp0_exc_cause() part 1

	andi $k0, $k0, 0x1f  # cp0_exc_cause() part 2

	sub $k0, 8           # 8 = SYSCALL

	beqz $k0, syscall_shortcut

	add $k0, 8           # Revert $k0 back to correct exc number

	REGISTERS_STORE_AND_EXC_RESET $sp

	move $a1, $sp

	jal exc_dispatch     # exc_dispatch(excno, register_space)

	move $a0, $k0

	REGISTERS_LOAD $sp

	# The $sp is automatically restored to former value

	eret

## Syscall entry

#

# Registers:

#

# @param v0		Syscall number.

# @param a0		1st argument.

# @param a1		2nd argument.

# @param a2		3rd argument.

# @param a3		4th argument.

# @param t0		5th argument.

# @param t1		6th argument.

#

# @return		The return value will be stored in v0.

#

#define SS_SP		EOFFSET_SP

#define SS_STATUS	EOFFSET_STATUS

#define SS_EPC		EOFFSET_EPC

#define SS_K1		EOFFSET_K1

syscall_shortcut:

	# We have a lot of space on the stack, with free use

	mfc0 $t3, $epc

	mfc0 $t2, $status

	sw $t3, SS_EPC($sp)		# Save EPC

	sw $k1, SS_K1($sp)   		# Save k1 not saved on context switch

	and $t4, $t2, REG_SAVE_MASK	# Save only KSU, EXL, ERL, IE

	li $t5, ~(0x1f)

	and $t2, $t2, $t5		# Clear KSU, EXL, ERL

	ori $t2, $t2, 0x1		# Set IE

	sw $t4, SS_STATUS($sp)

	mtc0 $t2, $status

	#

	# Call the higher level system call handler

	# We are going to reuse part of the unused exception stack frame

	#

	sw $t0, STACK_ARG4($sp)		# save the 5th argument on the stack

	sw $t1, STACK_ARG5($sp)		# save the 6th argument on the stack

	jal syscall_handler

	sw $v0, STACK_ARG6($sp)		# save the syscall number on the stack

	# restore status

	mfc0 $t2, $status

	lw $t3, SS_STATUS($sp)

	# Change back to EXL = 1 (from last exception), otherwise

	# an interrupt could rewrite the CP0 - EPC

	li $t4, ~REG_SAVE_MASK		# Mask UM, EXL, ERL, IE

	and $t2, $t2, $t4

	or $t2, $t2, $t3		# Copy saved UM, EXL, ERL, IE

	mtc0 $t2, $status

	# restore epc + 4

	lw $t2, SS_EPC($sp)

	lw $k1, SS_K1($sp)

	addi $t2, $t2, 4

	mtc0 $t2, $epc

	lw $sp, SS_SP($sp)		# restore sp

	eret

tlb_refill_handler:

	KERNEL_STACK_TO_K0

	sub $k0, REGISTER_SPACE

	REGISTERS_STORE_AND_EXC_RESET $k0

	sw $sp,EOFFSET_SP($k0)

	add $sp, $k0, 0

	jal tlb_refill

	add $a0, $sp, 0 

	REGISTERS_LOAD $sp

	eret

cache_error_handler:

	KERNEL_STACK_TO_K0

	sub $k0, REGISTER_SPACE

	REGISTERS_STORE_AND_EXC_RESET $k0

	sw $sp,EOFFSET_SP($k0)

	add $sp, $k0, 0

	jal cache_error

	add $a0, $sp, 0 

	REGISTERS_LOAD $sp

	eret

userspace_asm:

	add $sp, $a0, 0

	add $v0, $a1, 0 

	add $t9, $a2, 0			# Set up correct entry into PIC code

	xor $a0, $a0, $a0		# $a0 is defined to hold pcb_ptr

					# set it to 0

	eret