| ; WARNING : The refill handler has been modified, see below !!! |
| |
| /* |
| * Copyright (C) 2003 Axis Communications AB |
| * |
| * Authors: Mikael Starvik (starvik@axis.com) |
| * |
| * Code for the fault low-level handling routines. |
| * |
| */ |
| |
| #include <asm/page.h> |
| #include <asm/pgtable.h> |
| |
| ; Save all register. Must save in same order as struct pt_regs. |
| .macro SAVE_ALL |
| subq 12, $sp |
| move $erp, [$sp] |
| subq 4, $sp |
| move $srp, [$sp] |
| subq 4, $sp |
| move $ccs, [$sp] |
| subq 4, $sp |
| move $spc, [$sp] |
| subq 4, $sp |
| move $mof, [$sp] |
| subq 4, $sp |
| move $srs, [$sp] |
| subq 4, $sp |
| move.d $acr, [$sp] |
| subq 14*4, $sp |
| movem $r13, [$sp] |
| subq 4, $sp |
| move.d $r10, [$sp] |
| .endm |
| |
| ; Bus fault handler. Extracts relevant information and calls mm subsystem |
| ; to handle the fault. |
| .macro MMU_BUS_FAULT_HANDLER handler, mmu, we, ex |
| .globl \handler |
| .type \handler,"function" |
| \handler: |
| SAVE_ALL |
| move \mmu, $srs ; Select MMU support register bank |
| move.d $sp, $r11 ; regs |
| moveq 1, $r12 ; protection fault |
| moveq \we, $r13 ; write exception? |
| orq \ex << 1, $r13 ; execute? |
| move $s3, $r10 ; rw_mm_cause |
| and.d ~8191, $r10 ; Get faulting page start address |
| |
| jsr do_page_fault |
| nop |
| ba ret_from_intr |
| nop |
| .size \handler, . - \handler |
| .endm |
| |
| ; Refill handler. Three cases may occur: |
| ; 1. PMD and PTE exists in mm subsystem but not in TLB |
| ; 2. PMD exists but not PTE |
| ; 3. PMD doesn't exist |
| ; The code below handles case 1 and calls the mm subsystem for case 2 and 3. |
| ; Do not touch this code without very good reasons and extensive testing. |
| ; Note that the code is optimized to minimize stalls (makes the code harder |
| ; to read). |
| ; |
| ; WARNING !!! |
| ; Modified by Mikael Asker 060725: added a workaround for strange TLB |
| ; behavior. If the same PTE is present in more than one set, the TLB |
| ; doesn't recognize it and we get stuck in a loop of refill exceptions. |
| ; The workaround detects such loops and exits them by flushing |
| ; the TLB contents. The problem and workaround were verified |
| ; in VCS by Mikael Starvik. |
| ; |
| ; Each page is 8 KB. Each PMD holds 8192/4 PTEs (each PTE is 4 bytes) so each |
| ; PMD holds 16 MB of virtual memory. |
| ; Bits 0-12 : Offset within a page |
| ; Bits 13-23 : PTE offset within a PMD |
| ; Bits 24-31 : PMD offset within the PGD |
| |
| .macro MMU_REFILL_HANDLER handler, mmu |
| .data |
| 1: .dword 0 ; refill_count |
| ; == 0 <=> last_refill_cause is invalid |
| 2: .dword 0 ; last_refill_cause |
| .text |
| .globl \handler |
| .type \handler, "function" |
| \handler: |
| subq 4, $sp |
| ; (The pipeline stalls for one cycle; $sp used as address in the next cycle.) |
| move $srs, [$sp] |
| subq 4, $sp |
| move \mmu, $srs ; Select MMU support register bank |
| move.d $acr, [$sp] |
| subq 12, $sp |
| move.d 1b, $acr ; Point to refill_count |
| movem $r2, [$sp] |
| |
| test.d [$acr] ; refill_count == 0 ? |
| beq 5f ; yes, last_refill_cause is invalid |
| move.d $acr, $r1 |
| |
| ; last_refill_cause is valid, investigate cause |
| addq 4, $r1 ; Point to last_refill_cause |
| move $s3, $r0 ; Get rw_mm_cause |
| move.d [$r1], $r2 ; Get last_refill_cause |
| cmp.d $r0, $r2 ; rw_mm_cause == last_refill_cause ? |
| beq 6f ; yes, increment count |
| moveq 1, $r2 |
| |
| ; rw_mm_cause != last_refill_cause |
| move.d $r2, [$acr] ; refill_count = 1 |
| move.d $r0, [$r1] ; last_refill_cause = rw_mm_cause |
| |
| 3: ; Probably not in a loop, continue normal processing |
| move.d current_pgd, $acr ; PGD |
| ; Look up PMD in PGD |
| lsrq 24, $r0 ; Get PMD index into PGD (bit 24-31) |
| move.d [$acr], $acr ; PGD for the current process |
| addi $r0.d, $acr, $acr |
| move $s3, $r0 ; rw_mm_cause |
| move.d [$acr], $acr ; Get PMD |
| beq 8f |
| ; Look up PTE in PMD |
| lsrq PAGE_SHIFT, $r0 |
| and.w PAGE_MASK, $acr ; Remove PMD flags |
| and.d 0x7ff, $r0 ; Get PTE index into PMD (bit 13-23) |
| addi $r0.d, $acr, $acr |
| move.d [$acr], $acr ; Get PTE |
| beq 9f |
| movem [$sp], $r2 ; Restore r0-r2 in delay slot |
| addq 12, $sp |
| ; Store in TLB |
| move $acr, $s5 |
| 4: ; Return |
| move.d [$sp+], $acr |
| move [$sp], $srs |
| addq 4, $sp |
| rete |
| rfe |
| |
| 5: ; last_refill_cause is invalid |
| moveq 1, $r2 |
| addq 4, $r1 ; Point to last_refill_cause |
| move.d $r2, [$acr] ; refill_count = 1 |
| move $s3, $r0 ; Get rw_mm_cause |
| ba 3b ; Continue normal processing |
| move.d $r0,[$r1] ; last_refill_cause = rw_mm_cause |
| |
| 6: ; rw_mm_cause == last_refill_cause |
| move.d [$acr], $r2 ; Get refill_count |
| cmpq 4, $r2 ; refill_count > 4 ? |
| bhi 7f ; yes |
| addq 1, $r2 ; refill_count++ |
| ba 3b ; Continue normal processing |
| move.d $r2, [$acr] |
| |
| 7: ; refill_count > 4, error |
| move.d $acr, $r0 ; Save pointer to refill_count |
| clear.d [$r0] ; refill_count = 0 |
| |
| ;; rewind the short stack |
| movem [$sp], $r2 ; Restore r0-r2 |
| addq 12, $sp |
| move.d [$sp+], $acr |
| move [$sp], $srs |
| addq 4, $sp |
| ;; Keep it simple (slow), save all the regs. |
| SAVE_ALL |
| jsr __flush_tlb_all |
| nop |
| ba ret_from_intr ; Return |
| nop |
| |
| 8: ; PMD missing, let the mm subsystem fix it up. |
| movem [$sp], $r2 ; Restore r0-r2 |
| 9: ; PTE missing, let the mm subsystem fix it up. |
| addq 12, $sp |
| move.d [$sp+], $acr |
| move [$sp], $srs |
| addq 4, $sp |
| SAVE_ALL |
| move \mmu, $srs |
| move.d $sp, $r11 ; regs |
| clear.d $r12 ; Not a protection fault |
| move.w PAGE_MASK, $acr |
| move $s3, $r10 ; rw_mm_cause |
| btstq 9, $r10 ; Check if write access |
| smi $r13 |
| and.w PAGE_MASK, $r10 ; Get VPN (virtual address) |
| jsr do_page_fault |
| and.w $acr, $r10 |
| ; Return |
| ba ret_from_intr |
| nop |
| .size \handler, . - \handler |
| .endm |
| |
| ; This is the MMU bus fault handlers. |
| |
| MMU_REFILL_HANDLER i_mmu_refill, 1 |
| MMU_BUS_FAULT_HANDLER i_mmu_invalid, 1, 0, 0 |
| MMU_BUS_FAULT_HANDLER i_mmu_access, 1, 0, 0 |
| MMU_BUS_FAULT_HANDLER i_mmu_execute, 1, 0, 1 |
| MMU_REFILL_HANDLER d_mmu_refill, 2 |
| MMU_BUS_FAULT_HANDLER d_mmu_invalid, 2, 0, 0 |
| MMU_BUS_FAULT_HANDLER d_mmu_access, 2, 0, 0 |
| MMU_BUS_FAULT_HANDLER d_mmu_write, 2, 1, 0 |
