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+; 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