1; WARNING : The refill handler has been modified, see below !!! 2 3/* 4 * Copyright (C) 2003 Axis Communications AB 5 * 6 * Authors: Mikael Starvik (starvik@axis.com) 7 * 8 * Code for the fault low-level handling routines. 9 * 10 */ 11 12#include <asm/page.h> 13#include <asm/pgtable.h> 14 15; Save all register. Must save in same order as struct pt_regs. 16.macro SAVE_ALL 17 subq 12, $sp 18 move $erp, [$sp] 19 subq 4, $sp 20 move $srp, [$sp] 21 subq 4, $sp 22 move $ccs, [$sp] 23 subq 4, $sp 24 move $spc, [$sp] 25 subq 4, $sp 26 move $mof, [$sp] 27 subq 4, $sp 28 move $srs, [$sp] 29 subq 4, $sp 30 move.d $acr, [$sp] 31 subq 14*4, $sp 32 movem $r13, [$sp] 33 subq 4, $sp 34 move.d $r10, [$sp] 35.endm 36 37; Bus fault handler. Extracts relevant information and calls mm subsystem 38; to handle the fault. 39.macro MMU_BUS_FAULT_HANDLER handler, mmu, we, ex 40 .globl \handler 41\handler: 42 SAVE_ALL 43 move \mmu, $srs ; Select MMU support register bank 44 move.d $sp, $r11 ; regs 45 moveq 1, $r12 ; protection fault 46 moveq \we, $r13 ; write exception? 47 orq \ex << 1, $r13 ; execute? 48 move $s3, $r10 ; rw_mm_cause 49 and.d ~8191, $r10 ; Get faulting page start address 50 51 jsr do_page_fault 52 nop 53 ba ret_from_intr 54 nop 55.endm 56 57; Refill handler. Three cases may occur: 58; 1. PMD and PTE exists in mm subsystem but not in TLB 59; 2. PMD exists but not PTE 60; 3. PMD doesn't exist 61; The code below handles case 1 and calls the mm subsystem for case 2 and 3. 62; Do not touch this code without very good reasons and extensive testing. 63; Note that the code is optimized to minimize stalls (makes the code harder 64; to read). 65; 66; WARNING !!! 67; Modified by Mikael Asker 060725: added a workaround for strange TLB 68; behavior. If the same PTE is present in more than one set, the TLB 69; doesn't recognize it and we get stuck in a loop of refill exceptions. 70; The workaround detects such loops and exits them by flushing 71; the TLB contents. The problem and workaround were verified 72; in VCS by Mikael Starvik. 73; 74; Each page is 8 KB. Each PMD holds 8192/4 PTEs (each PTE is 4 bytes) so each 75; PMD holds 16 MB of virtual memory. 76; Bits 0-12 : Offset within a page 77; Bits 13-23 : PTE offset within a PMD 78; Bits 24-31 : PMD offset within the PGD 79 80.macro MMU_REFILL_HANDLER handler, mmu 81 .data 821: .dword 0 ; refill_count 83 ; == 0 <=> last_refill_cause is invalid 842: .dword 0 ; last_refill_cause 85 .text 86 .globl \handler 87\handler: 88 subq 4, $sp 89; (The pipeline stalls for one cycle; $sp used as address in the next cycle.) 90 move $srs, [$sp] 91 subq 4, $sp 92 move \mmu, $srs ; Select MMU support register bank 93 move.d $acr, [$sp] 94 subq 12, $sp 95 move.d 1b, $acr ; Point to refill_count 96 movem $r2, [$sp] 97 98 test.d [$acr] ; refill_count == 0 ? 99 beq 5f ; yes, last_refill_cause is invalid 100 move.d $acr, $r1 101 102 ; last_refill_cause is valid, investigate cause 103 addq 4, $r1 ; Point to last_refill_cause 104 move $s3, $r0 ; Get rw_mm_cause 105 move.d [$r1], $r2 ; Get last_refill_cause 106 cmp.d $r0, $r2 ; rw_mm_cause == last_refill_cause ? 107 beq 6f ; yes, increment count 108 moveq 1, $r2 109 110 ; rw_mm_cause != last_refill_cause 111 move.d $r2, [$acr] ; refill_count = 1 112 move.d $r0, [$r1] ; last_refill_cause = rw_mm_cause 113 1143: ; Probably not in a loop, continue normal processing 115#ifdef CONFIG_SMP 116 move $s7, $acr ; PGD 117#else 118 move.d per_cpu__current_pgd, $acr ; PGD 119#endif 120 ; Look up PMD in PGD 121 lsrq 24, $r0 ; Get PMD index into PGD (bit 24-31) 122 move.d [$acr], $acr ; PGD for the current process 123 addi $r0.d, $acr, $acr 124 move $s3, $r0 ; rw_mm_cause 125 move.d [$acr], $acr ; Get PMD 126 beq 8f 127 ; Look up PTE in PMD 128 lsrq PAGE_SHIFT, $r0 129 and.w PAGE_MASK, $acr ; Remove PMD flags 130 and.d 0x7ff, $r0 ; Get PTE index into PMD (bit 13-23) 131 addi $r0.d, $acr, $acr 132 move.d [$acr], $acr ; Get PTE 133 beq 9f 134 movem [$sp], $r2 ; Restore r0-r2 in delay slot 135 addq 12, $sp 136 ; Store in TLB 137 move $acr, $s5 1384: ; Return 139 move.d [$sp+], $acr 140 move [$sp], $srs 141 addq 4, $sp 142 rete 143 rfe 144 1455: ; last_refill_cause is invalid 146 moveq 1, $r2 147 addq 4, $r1 ; Point to last_refill_cause 148 move.d $r2, [$acr] ; refill_count = 1 149 move $s3, $r0 ; Get rw_mm_cause 150 ba 3b ; Continue normal processing 151 move.d $r0,[$r1] ; last_refill_cause = rw_mm_cause 152 1536: ; rw_mm_cause == last_refill_cause 154 move.d [$acr], $r2 ; Get refill_count 155 cmpq 4, $r2 ; refill_count > 4 ? 156 bhi 7f ; yes 157 addq 1, $r2 ; refill_count++ 158 ba 3b ; Continue normal processing 159 move.d $r2, [$acr] 160 1617: ; refill_count > 4, error 162 move.d $acr, $r0 ; Save pointer to refill_count 163 clear.d [$r0] ; refill_count = 0 164 165 ;; rewind the short stack 166 movem [$sp], $r2 ; Restore r0-r2 167 addq 12, $sp 168 move.d [$sp+], $acr 169 move [$sp], $srs 170 addq 4, $sp 171 ;; Keep it simple (slow), save all the regs. 172 SAVE_ALL 173 jsr __flush_tlb_all 174 nop 175 ba ret_from_intr ; Return 176 nop 177 1788: ; PMD missing, let the mm subsystem fix it up. 179 movem [$sp], $r2 ; Restore r0-r2 1809: ; PTE missing, let the mm subsystem fix it up. 181 addq 12, $sp 182 move.d [$sp+], $acr 183 move [$sp], $srs 184 addq 4, $sp 185 SAVE_ALL 186 move \mmu, $srs 187 move.d $sp, $r11 ; regs 188 clear.d $r12 ; Not a protection fault 189 move.w PAGE_MASK, $acr 190 move $s3, $r10 ; rw_mm_cause 191 btstq 9, $r10 ; Check if write access 192 smi $r13 193 and.w PAGE_MASK, $r10 ; Get VPN (virtual address) 194 jsr do_page_fault 195 and.w $acr, $r10 196 ; Return 197 ba ret_from_intr 198 nop 199.endm 200 201 ; This is the MMU bus fault handlers. 202 203MMU_REFILL_HANDLER i_mmu_refill, 1 204MMU_BUS_FAULT_HANDLER i_mmu_invalid, 1, 0, 0 205MMU_BUS_FAULT_HANDLER i_mmu_access, 1, 0, 0 206MMU_BUS_FAULT_HANDLER i_mmu_execute, 1, 0, 1 207MMU_REFILL_HANDLER d_mmu_refill, 2 208MMU_BUS_FAULT_HANDLER d_mmu_invalid, 2, 0, 0 209MMU_BUS_FAULT_HANDLER d_mmu_access, 2, 0, 0 210MMU_BUS_FAULT_HANDLER d_mmu_write, 2, 1, 0 211