LXR linux/arch/i386/mm/highmem.c

   1#include <linux/highmem.h>
   2#include <linux/module.h>
   3
   4void *kmap(struct page *page)
   5{
   6        might_sleep();
   7        if (!PageHighMem(page))
   8                return page_address(page);
   9        return kmap_high(page);
  10}
  11
  12void kunmap(struct page *page)
  13{
  14        if (in_interrupt())
  15                BUG();
  16        if (!PageHighMem(page))
  17                return;
  18        kunmap_high(page);
  19}
  20
  21/*
  22 * kmap_atomic/kunmap_atomic is significantly faster than kmap/kunmap because
  23 * no global lock is needed and because the kmap code must perform a global TLB
  24 * invalidation when the kmap pool wraps.
  25 *
  26 * However when holding an atomic kmap is is not legal to sleep, so atomic
  27 * kmaps are appropriate for short, tight code paths only.
  28 */
  29void *kmap_atomic_prot(struct page *page, enum km_type type, pgprot_t prot)
  30{
  31        enum fixed_addresses idx;
  32        unsigned long vaddr;
  33
  34        /* even !CONFIG_PREEMPT needs this, for in_atomic in do_page_fault */
  35        pagefault_disable();
  36
  37        idx = type + KM_TYPE_NR*smp_processor_id();
  38        BUG_ON(!pte_none(*(kmap_pte-idx)));
  39
  40        if (!PageHighMem(page))
  41                return page_address(page);
  42
  43        vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
  44        set_pte(kmap_pte-idx, mk_pte(page, prot));
  45        arch_flush_lazy_mmu_mode();
  46
  47        return (void*) vaddr;
  48}
  49
  50void *kmap_atomic(struct page *page, enum km_type type)
  51{
  52        return kmap_atomic_prot(page, type, kmap_prot);
  53}
  54
  55void kunmap_atomic(void *kvaddr, enum km_type type)
  56{
  57        unsigned long vaddr = (unsigned long) kvaddr & PAGE_MASK;
  58        enum fixed_addresses idx = type + KM_TYPE_NR*smp_processor_id();
  59
  60        /*
  61         * Force other mappings to Oops if they'll try to access this pte
  62         * without first remap it.  Keeping stale mappings around is a bad idea
  63         * also, in case the page changes cacheability attributes or becomes
  64         * a protected page in a hypervisor.
  65         */
  66        if (vaddr == __fix_to_virt(FIX_KMAP_BEGIN+idx))
  67                kpte_clear_flush(kmap_pte-idx, vaddr);
  68        else {
  69#ifdef CONFIG_DEBUG_HIGHMEM
  70                BUG_ON(vaddr < PAGE_OFFSET);
  71                BUG_ON(vaddr >= (unsigned long)high_memory);
  72#endif
  73        }
  74
  75        arch_flush_lazy_mmu_mode();
  76        pagefault_enable();
  77}
  78
  79/* This is the same as kmap_atomic() but can map memory that doesn't
  80 * have a struct page associated with it.
  81 */
  82void *kmap_atomic_pfn(unsigned long pfn, enum km_type type)
  83{
  84        enum fixed_addresses idx;
  85        unsigned long vaddr;
  86
  87        pagefault_disable();
  88
  89        idx = type + KM_TYPE_NR*smp_processor_id();
  90        vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
  91        set_pte(kmap_pte-idx, pfn_pte(pfn, kmap_prot));
  92        arch_flush_lazy_mmu_mode();
  93
  94        return (void*) vaddr;
  95}
  96
  97struct page *kmap_atomic_to_page(void *ptr)
  98{
  99        unsigned long idx, vaddr = (unsigned long)ptr;
 100        pte_t *pte;
 101
 102        if (vaddr < FIXADDR_START)
 103                return virt_to_page(ptr);
 104
 105        idx = virt_to_fix(vaddr);
 106        pte = kmap_pte - (idx - FIX_KMAP_BEGIN);
 107        return pte_page(*pte);
 108}
 109
 110EXPORT_SYMBOL(kmap);
 111EXPORT_SYMBOL(kunmap);
 112EXPORT_SYMBOL(kmap_atomic);
 113EXPORT_SYMBOL(kunmap_atomic);
 114EXPORT_SYMBOL(kmap_atomic_to_page);
 115