linux/arch/powerpc/mm/highmem.c
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   1/*
   2 * highmem.c: virtual kernel memory mappings for high memory
   3 *
   4 * PowerPC version, stolen from the i386 version.
   5 *
   6 * Used in CONFIG_HIGHMEM systems for memory pages which
   7 * are not addressable by direct kernel virtual addresses.
   8 *
   9 * Copyright (C) 1999 Gerhard Wichert, Siemens AG
  10 *                    Gerhard.Wichert@pdb.siemens.de
  11 *
  12 *
  13 * Redesigned the x86 32-bit VM architecture to deal with
  14 * up to 16 Terrabyte physical memory. With current x86 CPUs
  15 * we now support up to 64 Gigabytes physical RAM.
  16 *
  17 * Copyright (C) 1999 Ingo Molnar <mingo@redhat.com>
  18 *
  19 * Reworked for PowerPC by various contributors. Moved from
  20 * highmem.h by Benjamin Herrenschmidt (c) 2009 IBM Corp.
  21 */
  22
  23#include <linux/highmem.h>
  24#include <linux/module.h>
  25
  26/*
  27 * The use of kmap_atomic/kunmap_atomic is discouraged - kmap/kunmap
  28 * gives a more generic (and caching) interface. But kmap_atomic can
  29 * be used in IRQ contexts, so in some (very limited) cases we need
  30 * it.
  31 */
  32void *kmap_atomic_prot(struct page *page, pgprot_t prot)
  33{
  34        unsigned long vaddr;
  35        int idx, type;
  36
  37        /* even !CONFIG_PREEMPT needs this, for in_atomic in do_page_fault */
  38        pagefault_disable();
  39        if (!PageHighMem(page))
  40                return page_address(page);
  41
  42        type = kmap_atomic_idx_push();
  43        idx = type + KM_TYPE_NR*smp_processor_id();
  44        vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
  45#ifdef CONFIG_DEBUG_HIGHMEM
  46        BUG_ON(!pte_none(*(kmap_pte-idx)));
  47#endif
  48        __set_pte_at(&init_mm, vaddr, kmap_pte-idx, mk_pte(page, prot), 1);
  49        local_flush_tlb_page(NULL, vaddr);
  50
  51        return (void*) vaddr;
  52}
  53EXPORT_SYMBOL(kmap_atomic_prot);
  54
  55void __kunmap_atomic(void *kvaddr)
  56{
  57        unsigned long vaddr = (unsigned long) kvaddr & PAGE_MASK;
  58        int type;
  59
  60        if (vaddr < __fix_to_virt(FIX_KMAP_END)) {
  61                pagefault_enable();
  62                return;
  63        }
  64
  65        type = kmap_atomic_idx();
  66
  67#ifdef CONFIG_DEBUG_HIGHMEM
  68        {
  69                unsigned int idx;
  70
  71                idx = type + KM_TYPE_NR * smp_processor_id();
  72                BUG_ON(vaddr != __fix_to_virt(FIX_KMAP_BEGIN + idx));
  73
  74                /*
  75                 * force other mappings to Oops if they'll try to access
  76                 * this pte without first remap it
  77                 */
  78                pte_clear(&init_mm, vaddr, kmap_pte-idx);
  79                local_flush_tlb_page(NULL, vaddr);
  80        }
  81#endif
  82
  83        kmap_atomic_idx_pop();
  84        pagefault_enable();
  85}
  86EXPORT_SYMBOL(__kunmap_atomic);
  87