arch/i386/mm/highmem.c

   1 #include <linux/highmem.h>
   2 #include <linux/module.h>
   3
   4 void *kmap(struct page *page)
   5 {
   6         might_sleep();
   7         if (!PageHighMem(page))
   8                 return page_address(page);
   9         return kmap_high(page);
  10 }
  11
  12 void 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  */
  29 void *kmap_atomic(struct page *page, enum km_type type)
  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, kmap_prot));
  45
  46         return (void*) vaddr;
  47 }
  48
  49 void kunmap_atomic(void *kvaddr, enum km_type type)
  50 {
  51         unsigned long vaddr = (unsigned long) kvaddr & PAGE_MASK;
  52         enum fixed_addresses idx = type + KM_TYPE_NR*smp_processor_id();
  53
  54         /*
  55          * Force other mappings to Oops if they'll try to access this pte
  56          * without first remap it.  Keeping stale mappings around is a bad idea
  57          * also, in case the page changes cacheability attributes or becomes
  58          * a protected page in a hypervisor.
  59          */
  60         if (vaddr == __fix_to_virt(FIX_KMAP_BEGIN+idx))
  61                 kpte_clear_flush(kmap_pte-idx, vaddr);
  62         else {
  63 #ifdef CONFIG_DEBUG_HIGHMEM
  64                 BUG_ON(vaddr < PAGE_OFFSET);
  65                 BUG_ON(vaddr >= (unsigned long)high_memory);
  66 #endif
  67         }
  68
  69         pagefault_enable();
  70 }
  71
  72 /* This is the same as kmap_atomic() but can map memory that doesn't
  73  * have a struct page associated with it.
  74  */
  75 void *kmap_atomic_pfn(unsigned long pfn, enum km_type type)
  76 {
  77         enum fixed_addresses idx;
  78         unsigned long vaddr;
  79
  80         pagefault_disable();
  81
  82         idx = type + KM_TYPE_NR*smp_processor_id();
  83         vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
  84         set_pte(kmap_pte-idx, pfn_pte(pfn, kmap_prot));
  85
  86         return (void*) vaddr;
  87 }
  88
  89 struct page *kmap_atomic_to_page(void *ptr)
  90 {
  91         unsigned long idx, vaddr = (unsigned long)ptr;
  92         pte_t *pte;
  93
  94         if (vaddr < FIXADDR_START)
  95                 return virt_to_page(ptr);
  96
  97         idx = virt_to_fix(vaddr);
  98         pte = kmap_pte - (idx - FIX_KMAP_BEGIN);
  99         return pte_page(*pte);
 100 }
 101
 102 EXPORT_SYMBOL(kmap);
 103 EXPORT_SYMBOL(kunmap);
 104 EXPORT_SYMBOL(kmap_atomic);
 105 EXPORT_SYMBOL(kunmap_atomic);
 106 EXPORT_SYMBOL(kmap_atomic_to_page);