86 lines
2.7 KiB
C
86 lines
2.7 KiB
C
/*
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* This file contains the routines for handling the MMU on those
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* PowerPC implementations where the MMU substantially follows the
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* architecture specification. This includes the 6xx, 7xx, 7xxx,
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* and 8260 implementations but excludes the 8xx and 4xx.
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* -- paulus
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*
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* Derived from arch/ppc/mm/init.c:
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* Copyright (C) 1995-1996 Gary Thomas (gdt@linuxppc.org)
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*
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* Modifications by Paul Mackerras (PowerMac) (paulus@cs.anu.edu.au)
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* and Cort Dougan (PReP) (cort@cs.nmt.edu)
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* Copyright (C) 1996 Paul Mackerras
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* Amiga/APUS changes by Jesper Skov (jskov@cygnus.co.uk).
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*
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* Derived from "arch/i386/mm/init.c"
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* Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version
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* 2 of the License, or (at your option) any later version.
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*
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*/
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#include <linux/mm.h>
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#include <linux/init.h>
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#include <asm/mmu_context.h>
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#include <asm/tlbflush.h>
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unsigned long next_mmu_context;
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unsigned long context_map[LAST_CONTEXT / BITS_PER_LONG + 1];
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#ifdef FEW_CONTEXTS
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atomic_t nr_free_contexts;
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struct mm_struct *context_mm[LAST_CONTEXT+1];
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void steal_context(void);
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#endif /* FEW_CONTEXTS */
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/*
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* Initialize the context management stuff.
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*/
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void __init
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mmu_context_init(void)
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{
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/*
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* Some processors have too few contexts to reserve one for
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* init_mm, and require using context 0 for a normal task.
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* Other processors reserve the use of context zero for the kernel.
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* This code assumes FIRST_CONTEXT < 32.
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*/
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context_map[0] = (1 << FIRST_CONTEXT) - 1;
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next_mmu_context = FIRST_CONTEXT;
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#ifdef FEW_CONTEXTS
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atomic_set(&nr_free_contexts, LAST_CONTEXT - FIRST_CONTEXT + 1);
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#endif /* FEW_CONTEXTS */
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}
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#ifdef FEW_CONTEXTS
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/*
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* Steal a context from a task that has one at the moment.
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* This is only used on 8xx and 4xx and we presently assume that
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* they don't do SMP. If they do then this will have to check
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* whether the MM we steal is in use.
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* We also assume that this is only used on systems that don't
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* use an MMU hash table - this is true for 8xx and 4xx.
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* This isn't an LRU system, it just frees up each context in
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* turn (sort-of pseudo-random replacement :). This would be the
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* place to implement an LRU scheme if anyone was motivated to do it.
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* -- paulus
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*/
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void
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steal_context(void)
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{
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struct mm_struct *mm;
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/* free up context `next_mmu_context' */
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/* if we shouldn't free context 0, don't... */
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if (next_mmu_context < FIRST_CONTEXT)
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next_mmu_context = FIRST_CONTEXT;
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mm = context_mm[next_mmu_context];
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flush_tlb_mm(mm);
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destroy_context(mm);
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}
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#endif /* FEW_CONTEXTS */
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