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308 jermar 1
#
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# Copyright (c) 2003-2004 Jakub Jermar
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# All rights reserved.
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#
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# Redistribution and use in source and binary forms, with or without
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# modification, are permitted provided that the following conditions
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# are met:
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#
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# - Redistributions of source code must retain the above copyright
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#   notice, this list of conditions and the following disclaimer.
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# - Redistributions in binary form must reproduce the above copyright
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#   notice, this list of conditions and the following disclaimer in the
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#   documentation and/or other materials provided with the distribution.
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# - The name of the author may not be used to endorse or promote products
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#   derived from this software without specific prior written permission.
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#
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# THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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# IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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# OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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# IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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# INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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# NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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# THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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#
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#include <arch/asm/regname.h>
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#include <arch/mm/page.h>
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#include <arch/asm/boot.h>
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#include <arch/context_offset.h>
2607 jermar 33
#include <arch/stack.h>
3922 decky 34
 
1 jermar 35
.text
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37
.set noat
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.set noreorder
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.set nomacro
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41
.global kernel_image_start
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.global tlb_refill_entry
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.global cache_error_entry
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.global exception_entry
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.global userspace_asm
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1096 palkovsky 47
# Which status bits should are thread-local
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#define REG_SAVE_MASK 0x1f # KSU(UM), EXL, ERL, IE
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313 palkovsky 50
# Save registers to space defined by \r
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# We will change status: Disable ERL,EXL,UM,IE
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# These changes will be automatically reversed in REGISTER_LOAD
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# SP is NOT saved as part of these registers
1096 palkovsky 54
.macro REGISTERS_STORE_AND_EXC_RESET r
2607 jermar 55
	sw $at, EOFFSET_AT(\r)
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	sw $v0, EOFFSET_V0(\r)
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	sw $v1, EOFFSET_V1(\r)
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	sw $a0, EOFFSET_A0(\r)
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	sw $a1, EOFFSET_A1(\r)
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	sw $a2, EOFFSET_A2(\r)
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	sw $a3, EOFFSET_A3(\r)
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	sw $t0, EOFFSET_T0(\r)
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	sw $t1, EOFFSET_T1(\r)
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	sw $t2, EOFFSET_T2(\r)
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	sw $t3, EOFFSET_T3(\r)
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	sw $t4, EOFFSET_T4(\r)
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	sw $t5, EOFFSET_T5(\r)
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	sw $t6, EOFFSET_T6(\r)
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	sw $t7, EOFFSET_T7(\r)
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	sw $t8, EOFFSET_T8(\r)
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	sw $t9, EOFFSET_T9(\r)
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73
	mflo $at
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	sw $at, EOFFSET_LO(\r)
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	mfhi $at
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	sw $at, EOFFSET_HI(\r)
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2607 jermar 78
	sw $gp, EOFFSET_GP(\r)
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	sw $ra, EOFFSET_RA(\r)
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	sw $k1, EOFFSET_K1(\r)
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1096 palkovsky 82
	mfc0 $t0, $status
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	mfc0 $t1, $epc
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2607 jermar 85
	and $t2, $t0, REG_SAVE_MASK	# Save only KSU,EXL,ERL,IE
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	li $t3, ~(0x1f)
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	and $t0, $t0, $t3		# Clear KSU,EXL,ERL,IE
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	sw $t2,EOFFSET_STATUS(\r)
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	sw $t1,EOFFSET_EPC(\r)
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	mtc0 $t0, $status
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.endm
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.macro REGISTERS_LOAD r
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	# Update only UM,EXR,IE from status, the rest
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	# is controlled by OS and not bound to task
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	mfc0 $t0, $status
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	lw $t1,EOFFSET_STATUS(\r)
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2607 jermar 100
	li $t2, ~REG_SAVE_MASK		# Mask UM,EXL,ERL,IE
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	and $t0, $t0, $t2
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2607 jermar 103
	or $t0, $t0, $t1		# Copy UM,EXL, ERL, IE from saved status
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	mtc0 $t0, $status
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2607 jermar 106
	lw $v0, EOFFSET_V0(\r)
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	lw $v1, EOFFSET_V1(\r)
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	lw $a0, EOFFSET_A0(\r)
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	lw $a1, EOFFSET_A1(\r)
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	lw $a2, EOFFSET_A2(\r)
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	lw $a3, EOFFSET_A3(\r)
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	lw $t0, EOFFSET_T0(\r)
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	lw $t1, EOFFSET_T1(\r)
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	lw $t2, EOFFSET_T2(\r)
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	lw $t3, EOFFSET_T3(\r)
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	lw $t4, EOFFSET_T4(\r)
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	lw $t5, EOFFSET_T5(\r)
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	lw $t6, EOFFSET_T6(\r)
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	lw $t7, EOFFSET_T7(\r)
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	lw $t8, EOFFSET_T8(\r)
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	lw $t9, EOFFSET_T9(\r)
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2607 jermar 123
	lw $gp, EOFFSET_GP(\r)
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	lw $ra, EOFFSET_RA(\r)
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	lw $k1, EOFFSET_K1(\r)
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2607 jermar 127
	lw $at, EOFFSET_LO(\r)
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	mtlo $at
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	lw $at, EOFFSET_HI(\r)
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	mthi $at
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2607 jermar 132
	lw $at, EOFFSET_EPC(\r)
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	mtc0 $at, $epc
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2607 jermar 135
	lw $at, EOFFSET_AT(\r)
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	lw $sp, EOFFSET_SP(\r)
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.endm
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# Move kernel stack pointer address to register K0
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# - if we are in user mode, load the appropriate stack
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# address
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.macro KERNEL_STACK_TO_K0
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	# If we are in user mode
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	mfc0 $k0, $status
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	andi $k0, 0x10
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	beq $k0, $0, 1f
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	add $k0, $sp, 0
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	# Move $k0 pointer to kernel stack
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	lui $k0, %hi(supervisor_sp)
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	ori $k0, $k0, %lo(supervisor_sp)
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	# Move $k0 (superveisor_sp)
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	lw $k0, 0($k0)
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1:
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.endm
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.org 0x0
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kernel_image_start:
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	/* Load temporary stack */
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	lui $sp, %hi(end_stack)
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	ori $sp, $sp, %lo(end_stack)
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3922 decky 164
	/* Not sure about this, but might
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	   be needed for PIC code */
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	lui $gp, 0x8000
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3922 decky 168
	/* $a1 contains physical address of bootinfo_t */
1686 decky 169
 
1222 decky 170
	jal arch_pre_main
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	nop
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173
	j main_bsp
174
	nop
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176
	.space TEMP_STACK_SIZE
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end_stack:
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tlb_refill_entry:
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	j tlb_refill_handler
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	nop
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cache_error_entry:
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	j cache_error_handler
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	nop
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187
exception_entry:
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	j exception_handler
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	nop
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313 palkovsky 191
exception_handler:
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	KERNEL_STACK_TO_K0
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	sub $k0, REGISTER_SPACE
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	sw $sp, EOFFSET_SP($k0)
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	move $sp, $k0
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	mfc0 $k0, $cause
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3922 decky 199
	sra $k0, $k0, 0x2    # cp0_exc_cause() part 1
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	andi $k0, $k0, 0x1f  # cp0_exc_cause() part 2
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	sub $k0, 8           # 8 = SYSCALL
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1102 palkovsky 203
	beqz $k0, syscall_shortcut
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	add $k0, 8           # Revert $k0 back to correct exc number
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1102 palkovsky 206
	REGISTERS_STORE_AND_EXC_RESET $sp
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	move $a1, $sp
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	jal exc_dispatch     # exc_dispatch(excno, register_space)
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	move $a0, $k0
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	REGISTERS_LOAD $sp
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	# The $sp is automatically restored to former value
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	eret
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2607 jermar 216
## Syscall entry
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#
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# Registers:
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#
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# @param v0		Syscall number.
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# @param a0		1st argument.
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# @param a1		2nd argument.
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# @param a2		3rd argument.
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# @param a3		4th argument.
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# @param t0		5th argument.
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# @param t1		6th argument.
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#
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# @return		The return value will be stored in v0.
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#
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#define SS_SP		EOFFSET_SP
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#define SS_STATUS	EOFFSET_STATUS
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#define SS_EPC		EOFFSET_EPC
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#define SS_K1		EOFFSET_K1
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syscall_shortcut:
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	# We have a lot of space on the stack, with free use
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	mfc0 $t3, $epc
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	mfc0 $t2, $status
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	sw $t3, SS_EPC($sp)		# Save EPC
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	sw $k1, SS_K1($sp)   		# Save k1 not saved on context switch
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2607 jermar 241
	and $t4, $t2, REG_SAVE_MASK	# Save only KSU, EXL, ERL, IE
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	li $t5, ~(0x1f)
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	and $t2, $t2, $t5		# Clear KSU, EXL, ERL
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	ori $t2, $t2, 0x1		# Set IE
1096 palkovsky 245
 
2607 jermar 246
	sw $t4, SS_STATUS($sp)
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	mtc0 $t2, $status
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2607 jermar 249
	#
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	# Call the higher level system call handler
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	# We are going to reuse part of the unused exception stack frame
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	#
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	sw $t0, STACK_ARG4($sp)		# save the 5th argument on the stack
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	sw $t1, STACK_ARG5($sp)		# save the 6th argument on the stack
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	jal syscall_handler
2607 jermar 256
	sw $v0, STACK_ARG6($sp)		# save the syscall number on the stack
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	# restore status
2607 jermar 259
	mfc0 $t2, $status
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	lw $t3, SS_STATUS($sp)
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2607 jermar 262
	# Change back to EXL = 1 (from last exception), otherwise
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	# an interrupt could rewrite the CP0 - EPC
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	li $t4, ~REG_SAVE_MASK		# Mask UM, EXL, ERL, IE
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	and $t2, $t2, $t4
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	or $t2, $t2, $t3		# Copy saved UM, EXL, ERL, IE
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	mtc0 $t2, $status
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2607 jermar 269
	# restore epc + 4
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	lw $t2, SS_EPC($sp)
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	lw $k1, SS_K1($sp)
272
	addi $t2, $t2, 4
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	mtc0 $t2, $epc
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2607 jermar 275
	lw $sp, SS_SP($sp)		# restore sp
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277
	eret
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1 jermar 279
tlb_refill_handler:
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	KERNEL_STACK_TO_K0
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	sub $k0, REGISTER_SPACE
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	REGISTERS_STORE_AND_EXC_RESET $k0
1102 palkovsky 283
	sw $sp,EOFFSET_SP($k0)
313 palkovsky 284
	add $sp, $k0, 0
125 jermar 285
 
1769 jermar 286
	jal tlb_refill
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	add $a0, $sp, 0 
125 jermar 288
 
306 palkovsky 289
	REGISTERS_LOAD $sp
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50 jermar 291
	eret
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293
cache_error_handler:
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	KERNEL_STACK_TO_K0
1102 palkovsky 295
	sub $k0, REGISTER_SPACE
296
	REGISTERS_STORE_AND_EXC_RESET $k0
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	sw $sp,EOFFSET_SP($k0)
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	add $sp, $k0, 0
1 jermar 299
 
50 jermar 300
	jal cache_error
1769 jermar 301
	add $a0, $sp, 0 
125 jermar 302
 
306 palkovsky 303
	REGISTERS_LOAD $sp
1 jermar 304
 
50 jermar 305
	eret
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307
userspace_asm:
308
	add $sp, $a0, 0
1122 palkovsky 309
	add $v0, $a1, 0 
3222 svoboda 310
	add $t9, $a2, 0			# Set up correct entry into PIC code
311
	xor $a0, $a0, $a0		# $a0 is defined to hold pcb_ptr
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					# set it to 0
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	eret