| 1 | #
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| 2 | # Copyright (c) 2003-2004 Jakub Jermar
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| 3 | # All rights reserved.
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| 4 | #
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| 5 | # Redistribution and use in source and binary forms, with or without
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| 6 | # modification, are permitted provided that the following conditions
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| 7 | # are met:
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| 8 | #
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| 9 | # - Redistributions of source code must retain the above copyright
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| 10 | # notice, this list of conditions and the following disclaimer.
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| 11 | # - Redistributions in binary form must reproduce the above copyright
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| 12 | # notice, this list of conditions and the following disclaimer in the
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| 13 | # documentation and/or other materials provided with the distribution.
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| 14 | # - The name of the author may not be used to endorse or promote products
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| 15 | # derived from this software without specific prior written permission.
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| 16 | #
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| 17 | # THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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| 18 | # IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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| 19 | # OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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| 20 | # IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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| 21 | # INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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| 22 | # NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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| 23 | # DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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| 24 | # THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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| 25 | # (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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| 26 | # THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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| 27 | #
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| 28 |
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| 29 | #include <arch/asm/regname.h>
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| 30 | #include <arch/mm/page.h>
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| 31 | #include <arch/asm/boot.h>
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| 32 | #include <arch/context_offset.h>
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| 33 | #include <arch/stack.h>
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| 34 |
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| 35 | .text
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| 36 |
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| 37 | .set noat
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| 38 | .set noreorder
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| 39 | .set nomacro
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| 40 |
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| 41 | .global kernel_image_start
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| 42 | .global tlb_refill_entry
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| 43 | .global cache_error_entry
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| 44 | .global exception_entry
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| 45 | .global userspace_asm
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| 46 |
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| 47 | # Which status bits should are thread-local
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| 48 | #define REG_SAVE_MASK 0x1f # KSU(UM), EXL, ERL, IE
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| 49 |
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| 50 | # Save registers to space defined by \r
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| 51 | # We will change status: Disable ERL, EXL, UM, IE
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| 52 | # These changes will be automatically reversed in REGISTER_LOAD
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| 53 | # %sp is NOT saved as part of these registers
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| 54 | .macro REGISTERS_STORE_AND_EXC_RESET r
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| 55 | sw $at, EOFFSET_AT(\r)
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| 56 | sw $v0, EOFFSET_V0(\r)
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| 57 | sw $v1, EOFFSET_V1(\r)
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| 58 | sw $a0, EOFFSET_A0(\r)
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| 59 | sw $a1, EOFFSET_A1(\r)
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| 60 | sw $a2, EOFFSET_A2(\r)
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| 61 | sw $a3, EOFFSET_A3(\r)
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| 62 | sw $t0, EOFFSET_T0(\r)
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| 63 | sw $t1, EOFFSET_T1(\r)
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| 64 | sw $t2, EOFFSET_T2(\r)
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| 65 | sw $t3, EOFFSET_T3(\r)
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| 66 | sw $t4, EOFFSET_T4(\r)
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| 67 | sw $t5, EOFFSET_T5(\r)
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| 68 | sw $t6, EOFFSET_T6(\r)
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| 69 | sw $t7, EOFFSET_T7(\r)
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| 70 | sw $t8, EOFFSET_T8(\r)
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| 71 | sw $t9, EOFFSET_T9(\r)
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| 72 |
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| 73 | mflo $at
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| 74 | sw $at, EOFFSET_LO(\r)
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| 75 | mfhi $at
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| 76 | sw $at, EOFFSET_HI(\r)
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| 77 |
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| 78 | sw $gp, EOFFSET_GP(\r)
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| 79 | sw $ra, EOFFSET_RA(\r)
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| 80 | sw $k1, EOFFSET_K1(\r)
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| 81 |
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| 82 | mfc0 $t0, $status
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| 83 | mfc0 $t1, $epc
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| 84 |
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| 85 | # save only KSU, EXL, ERL, IE
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| 86 | and $t2, $t0, REG_SAVE_MASK
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| 87 |
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| 88 | # clear KSU, EXL, ERL, IE
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| 89 | li $t3, ~(REG_SAVE_MASK)
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| 90 | and $t0, $t0, $t3
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| 91 |
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| 92 | sw $t2, EOFFSET_STATUS(\r)
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| 93 | sw $t1, EOFFSET_EPC(\r)
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| 94 | mtc0 $t0, $status
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| 95 | .endm
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| 96 |
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| 97 | .macro REGISTERS_LOAD r
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| 98 | # Update only UM, EXR, IE from status, the rest
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| 99 | # is controlled by OS and not bound to task
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| 100 | mfc0 $t0, $status
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| 101 | lw $t1,EOFFSET_STATUS(\r)
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| 102 |
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| 103 | # Mask UM, EXL, ERL, IE
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| 104 | li $t2, ~REG_SAVE_MASK
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| 105 | and $t0, $t0, $t2
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| 106 |
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| 107 | # Copy UM, EXL, ERL, IE from saved status
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| 108 | or $t0, $t0, $t1
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| 109 | mtc0 $t0, $status
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| 110 |
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| 111 | lw $v0, EOFFSET_V0(\r)
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| 112 | lw $v1, EOFFSET_V1(\r)
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| 113 | lw $a0, EOFFSET_A0(\r)
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| 114 | lw $a1, EOFFSET_A1(\r)
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| 115 | lw $a2, EOFFSET_A2(\r)
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| 116 | lw $a3, EOFFSET_A3(\r)
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| 117 | lw $t0, EOFFSET_T0(\r)
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| 118 | lw $t1, EOFFSET_T1(\r)
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| 119 | lw $t2, EOFFSET_T2(\r)
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| 120 | lw $t3, EOFFSET_T3(\r)
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| 121 | lw $t4, EOFFSET_T4(\r)
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| 122 | lw $t5, EOFFSET_T5(\r)
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| 123 | lw $t6, EOFFSET_T6(\r)
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| 124 | lw $t7, EOFFSET_T7(\r)
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| 125 | lw $t8, EOFFSET_T8(\r)
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| 126 | lw $t9, EOFFSET_T9(\r)
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| 127 |
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| 128 | lw $gp, EOFFSET_GP(\r)
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| 129 | lw $ra, EOFFSET_RA(\r)
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| 130 | lw $k1, EOFFSET_K1(\r)
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| 131 |
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| 132 | lw $at, EOFFSET_LO(\r)
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| 133 | mtlo $at
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| 134 | lw $at, EOFFSET_HI(\r)
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| 135 | mthi $at
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| 136 |
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| 137 | lw $at, EOFFSET_EPC(\r)
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| 138 | mtc0 $at, $epc
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| 139 |
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| 140 | lw $at, EOFFSET_AT(\r)
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| 141 | lw $sp, EOFFSET_SP(\r)
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| 142 | .endm
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| 143 |
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| 144 | # Move kernel stack pointer address to register K0
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| 145 | # - if we are in user mode, load the appropriate stack address
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| 146 | .macro KERNEL_STACK_TO_K0
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| 147 | # if we are in user mode
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| 148 | mfc0 $k0, $status
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| 149 | andi $k0, 0x10
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| 150 |
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| 151 | beq $k0, $0, 1f
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| 152 | add $k0, $sp, 0
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| 153 |
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| 154 | # move $k0 pointer to kernel stack
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| 155 | lui $k0, %hi(supervisor_sp)
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| 156 | ori $k0, $k0, %lo(supervisor_sp)
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| 157 |
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| 158 | # move $k0 (supervisor_sp)
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| 159 | lw $k0, 0($k0)
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| 160 |
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| 161 | 1:
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| 162 | .endm
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| 163 |
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| 164 | .org 0x0
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| 165 | kernel_image_start:
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| 166 | # load temporary stack
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| 167 | lui $sp, %hi(end_stack)
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| 168 | ori $sp, $sp, %lo(end_stack)
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| 169 |
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| 170 | # Not sure about this, but might
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| 171 | # be needed for PIC code
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| 172 | lui $gp, 0x8000
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| 173 |
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| 174 | # $a1 contains physical address of bootinfo_t
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| 175 | jal arch_pre_main
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| 176 | nop
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| 177 |
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| 178 | j main_bsp
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| 179 | nop
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| 180 |
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| 181 | .space TEMP_STACK_SIZE
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| 182 | end_stack:
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| 183 |
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| 184 | tlb_refill_entry:
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| 185 | j tlb_refill_handler
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| 186 | nop
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| 187 |
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| 188 | cache_error_entry:
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| 189 | j cache_error_handler
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| 190 | nop
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| 191 |
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| 192 | exception_entry:
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| 193 | j exception_handler
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| 194 | nop
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| 195 |
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| 196 | exception_handler:
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| 197 | KERNEL_STACK_TO_K0
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| 198 |
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| 199 | sub $k0, REGISTER_SPACE
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| 200 | sw $sp, EOFFSET_SP($k0)
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| 201 | move $sp, $k0
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| 202 |
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| 203 | mfc0 $k0, $cause
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| 204 |
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| 205 | sra $k0, $k0, 0x2 # cp0_exc_cause() part 1
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| 206 | andi $k0, $k0, 0x1f # cp0_exc_cause() part 2
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| 207 | sub $k0, 8 # 8 = SYSCALL
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| 208 |
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| 209 | beqz $k0, syscall_shortcut
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| 210 | add $k0, 8 # Revert $k0 back to correct exc number
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| 211 |
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| 212 | REGISTERS_STORE_AND_EXC_RESET $sp
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| 213 |
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| 214 | move $a1, $sp
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| 215 | jal exc_dispatch # exc_dispatch(excno, register_space)
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| 216 | move $a0, $k0
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| 217 |
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| 218 | REGISTERS_LOAD $sp
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| 219 | # The $sp is automatically restored to former value
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| 220 | eret
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| 221 |
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| 222 | ## Syscall entry
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| 223 | #
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| 224 | # Registers:
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| 225 | #
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| 226 | # @param v0 Syscall number.
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| 227 | # @param a0 1st argument.
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| 228 | # @param a1 2nd argument.
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| 229 | # @param a2 3rd argument.
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| 230 | # @param a3 4th argument.
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| 231 | # @param t0 5th argument.
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| 232 | # @param t1 6th argument.
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| 233 | #
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| 234 | # @return The return value will be stored in v0.
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| 235 | #
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| 236 | #define SS_SP EOFFSET_SP
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| 237 | #define SS_STATUS EOFFSET_STATUS
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| 238 | #define SS_EPC EOFFSET_EPC
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| 239 | #define SS_K1 EOFFSET_K1
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| 240 | syscall_shortcut:
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| 241 | # We have a lot of space on the stack, with free use
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| 242 | mfc0 $t3, $epc
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| 243 | mfc0 $t2, $status
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| 244 | sw $t3, SS_EPC($sp) # Save EPC
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| 245 | sw $k1, SS_K1($sp) # Save k1 not saved on context switch
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| 246 |
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| 247 | and $t4, $t2, REG_SAVE_MASK # Save only KSU, EXL, ERL, IE
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| 248 | li $t5, ~(0x1f)
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| 249 | and $t2, $t2, $t5 # Clear KSU, EXL, ERL
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| 250 | ori $t2, $t2, 0x1 # Set IE
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| 251 |
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| 252 | sw $t4, SS_STATUS($sp)
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| 253 | mtc0 $t2, $status
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| 254 |
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| 255 | #
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| 256 | # Call the higher level system call handler
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| 257 | # We are going to reuse part of the unused exception stack frame
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| 258 | #
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| 259 | sw $t0, STACK_ARG4($sp) # save the 5th argument on the stack
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| 260 | sw $t1, STACK_ARG5($sp) # save the 6th argument on the stack
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| 261 | jal syscall_handler
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| 262 | sw $v0, STACK_ARG6($sp) # save the syscall number on the stack
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| 263 |
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| 264 | # restore status
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| 265 | mfc0 $t2, $status
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| 266 | lw $t3, SS_STATUS($sp)
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| 267 |
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| 268 | # Change back to EXL = 1 (from last exception), otherwise
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| 269 | # an interrupt could rewrite the CP0 - EPC
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| 270 | li $t4, ~REG_SAVE_MASK # Mask UM, EXL, ERL, IE
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| 271 | and $t2, $t2, $t4
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| 272 | or $t2, $t2, $t3 # Copy saved UM, EXL, ERL, IE
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| 273 | mtc0 $t2, $status
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| 274 |
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| 275 | # restore epc + 4
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| 276 | lw $t2, SS_EPC($sp)
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| 277 | lw $k1, SS_K1($sp)
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| 278 | addi $t2, $t2, 4
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| 279 | mtc0 $t2, $epc
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| 280 |
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| 281 | lw $sp, SS_SP($sp) # restore sp
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| 282 |
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| 283 | eret
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| 284 |
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| 285 | tlb_refill_handler:
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| 286 | KERNEL_STACK_TO_K0
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| 287 | sub $k0, REGISTER_SPACE
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| 288 | REGISTERS_STORE_AND_EXC_RESET $k0
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| 289 | sw $sp,EOFFSET_SP($k0)
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| 290 | add $sp, $k0, 0
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| 291 |
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| 292 | jal tlb_refill
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| 293 | add $a0, $sp, 0
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| 294 |
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| 295 | REGISTERS_LOAD $sp
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| 296 |
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| 297 | eret
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| 298 |
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| 299 | cache_error_handler:
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| 300 | KERNEL_STACK_TO_K0
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| 301 | sub $k0, REGISTER_SPACE
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| 302 | REGISTERS_STORE_AND_EXC_RESET $k0
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| 303 | sw $sp,EOFFSET_SP($k0)
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| 304 | add $sp, $k0, 0
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| 305 |
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| 306 | jal cache_error
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| 307 | add $a0, $sp, 0
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| 308 |
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| 309 | REGISTERS_LOAD $sp
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| 310 |
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| 311 | eret
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| 312 |
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| 313 | userspace_asm:
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| 314 | add $sp, $a0, 0
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| 315 | add $v0, $a1, 0
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| 316 | add $t9, $a2, 0 # Set up correct entry into PIC code
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| 317 | xor $a0, $a0, $a0 # $a0 is defined to hold pcb_ptr
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| 318 | # set it to 0
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| 319 | eret
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