1 /* 2 * Interrupt and TLB miss handling support. 3 * 4 * Copyright (C) 2015, 2016 Paul Boddie <paul@boddie.org.uk> 5 * 6 * This program is free software: you can redistribute it and/or modify 7 * it under the terms of the GNU General Public License as published by 8 * the Free Software Foundation, either version 3 of the License, or 9 * (at your option) any later version. 10 * 11 * This program is distributed in the hope that it will be useful, 12 * but WITHOUT ANY WARRANTY; without even the implied warranty of 13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 14 * GNU General Public License for more details. 15 * 16 * You should have received a copy of the GNU General Public License 17 * along with this program. If not, see <http://www.gnu.org/licenses/>. 18 */ 19 20 .text 21 .extern interrupt_handler 22 .extern current_registers 23 .extern current_stack_pointer 24 .extern _shared_end 25 .globl _tlb_entry 26 .globl _exc_entry 27 .globl _irq_entry 28 .globl _end_entries 29 .globl _enter_task 30 .set noreorder 31 32 #include "paging.h" 33 34 _tlb_entry: 35 /* Get the bad address. */ 36 37 mfc0 $k0, $10 /* CP0_ENTRYHI */ 38 nop 39 andi $k1, $k0, 0xff /* ASID */ 40 41 /* For ASID == 0... */ 42 43 beqz $k1, _tlb_entry_direct 44 nop 45 46 /* For addresses beyond the program and data... */ 47 48 lui $k1, %hi(_shared_end - 0x80000000) 49 ori $k1, $k1, %lo(_shared_end - 0x80000000) 50 sltu $k1, $k1, $k0 51 bnez $k1, _tlb_entry_direct 52 nop 53 54 _tlb_entry_table: 55 /* Otherwise, load the page table entries. */ 56 57 andi $k1, $k0, 0xff /* ASID */ 58 li $k0, page_table_task_size 59 mul $k0, $k0, $k1 /* [ASID] (ASID * page_table_task_size) */ 60 li $k1, page_table_start /* page_table */ 61 addu $k1, $k0, $k1 /* page_table[ASID] */ 62 63 mfc0 $k0, $4 /* CP0_CONTEXT */ 64 nop 65 srl $k0, $k0, 1 /* use 8 byte - not 16 byte - entries */ 66 addu $k0, $k0, $k1 /* page_table[ASID][entry] */ 67 68 lw $k1, 0($k0) /* page_table[ASID][entry][0] */ 69 mtc0 $k1, $2 /* CP0_ENTRYLO0 */ 70 71 lw $k1, 4($k0) /* page_table[ASID][entry][1] */ 72 mtc0 $k1, $3 /* CP0_ENTRYLO1 */ 73 /* page size is 4KB */ 74 mtc0 $zero, $5 /* CP0_PAGEMASK */ 75 nop 76 77 tlbwr 78 nop 79 80 j _tlb_exit 81 nop 82 83 _tlb_entry_direct: 84 /* Otherwise, just translate the address directly. */ 85 86 li $k1, 0xffffe000 87 and $k0, $k0, $k1 /* VPN2 (8KB resolution) */ 88 srl $k0, $k0, 6 /* PFN (maintain 8KB resolution, bit 6 remaining zero) */ 89 ori $k0, $k0, 0x1e /* flags */ 90 91 mtc0 $k0, $2 /* CP0_ENTRYLO0 */ 92 ori $k0, $k0, 0x40 /* page size is 4KB (bit 6 set) */ 93 mtc0 $k0, $3 /* CP0_ENTRYLO1 */ 94 nop /* page size is 4KB */ 95 mtc0 $zero, $5 /* CP0_PAGEMASK */ 96 nop 97 98 tlbwr 99 nop 100 101 /* For ASID == 0... */ 102 103 andi $k1, $k0, 0xff /* ASID */ 104 bnez $k1, _tlb_exit 105 nop 106 eret 107 nop 108 109 _tlb_exit: 110 /* For ASID != 0... */ 111 112 lui $k0, %hi(_enter_task) 113 ori $k0, $k0, %lo(_enter_task) 114 lw $k1, 0($k0) 115 jr $k1 116 nop 117 118 _exc_entry: 119 /* Handle TLB refill exceptions. */ 120 121 mfc0 $k0, $13 /* CP0_CAUSE */ 122 li $k1, 0x0000007c 123 and $k0, $k0, $k1 /* ExcCode << 2 */ 124 srl $k0, $k0, 2 /* ExcCode */ 125 addi $k1, $k0, -2 /* ExcCode == 2 */ 126 beqz $k1, _tlb_entry 127 addi $k1, $k0, -3 /* ExcCode == 3 */ 128 beqz $k1, _tlb_entry 129 nop 130 _fail: 131 b _fail 132 nop 133 134 _irq_entry: 135 /* Set the ASID. */ 136 137 mtc0 $zero, $10 /* CP0_ENTRYHI */ 138 nop 139 140 /* Obtain the kernel global offset table. */ 141 142 move $k0, $gp 143 lui $gp, %hi(_GLOBAL_OFFSET_TABLE_) 144 ori $gp, $gp, %lo(_GLOBAL_OFFSET_TABLE_) 145 146 /* Obtain a store of registers for the current task. */ 147 148 la $k1, current_registers 149 lw $k1, 0($k1) 150 151 /* Save registers that the assembler wants to trash. */ 152 153 sw $t9, 100($k1) 154 sw $k0, 104($k1) /* old gp */ 155 sw $ra, 112($k1) 156 157 /* Record the stack pointer. */ 158 159 la $k1, current_stack_pointer 160 lw $k1, 0($k1) /* &stack_pointers[current_task] */ 161 sw $sp, 0($k1) 162 163 /* Switch to the kernel stack. */ 164 165 li $sp, 0x80070000 166 167 /* Invoke the rest of the interrupt handling process. */ 168 169 la $k0, interrupt_handler 170 jr $k0 171 nop 172 173 _end_entries: 174 175 .set reorder
