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         inc_preempt_count();
  36         if (!PageHighMem(page))
  37                 return page_address(page);
  38
  39         idx = type + KM_TYPE_NR*smp_processor_id();
  40         vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
  41         if (!pte_none(*(kmap_pte-idx)))
  42                 BUG();
  43         set_pte(kmap_pte-idx, mk_pte(page, kmap_prot));
  44
  45         return (void*) vaddr;
  46 }
  47
  48 void kunmap_atomic(void *kvaddr, enum km_type type)
  49 {
  50         unsigned long vaddr = (unsigned long) kvaddr & PAGE_MASK;
  51         enum fixed_addresses idx = type + KM_TYPE_NR*smp_processor_id();
  52
  53 #ifdef CONFIG_DEBUG_HIGHMEM
  54         if (vaddr >= PAGE_OFFSET && vaddr < (unsigned long)high_memory) {
  55                 dec_preempt_count();
  56                 preempt_check_resched();
  57                 return;
  58         }
  59
  60         if (vaddr != __fix_to_virt(FIX_KMAP_BEGIN+idx))
  61                 BUG();
  62 #endif
  63         /*
  64          * Force other mappings to Oops if they'll try to access this pte
  65          * without first remap it.  Keeping stale mappings around is a bad idea
  66          * also, in case the page changes cacheability attributes or becomes
  67          * a protected page in a hypervisor.
  68          */
  69         kpte_clear_flush(kmap_pte-idx, vaddr);
  70
  71         dec_preempt_count();
  72         preempt_check_resched();
  73 }
  74
  75 /* This is the same as kmap_atomic() but can map memory that doesn't
  76  * have a struct page associated with it.
  77  */
  78 void *kmap_atomic_pfn(unsigned long pfn, enum km_type type)
  79 {
  80         enum fixed_addresses idx;
  81         unsigned long vaddr;
  82
  83         inc_preempt_count();
  84
  85         idx = type + KM_TYPE_NR*smp_processor_id();
  86         vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
  87         set_pte(kmap_pte-idx, pfn_pte(pfn, kmap_prot));
  88
  89         return (void*) vaddr;
  90 }
  91
  92 struct page *kmap_atomic_to_page(void *ptr)
  93 {
  94         unsigned long idx, vaddr = (unsigned long)ptr;
  95         pte_t *pte;
  96
  97         if (vaddr < FIXADDR_START)
  98                 return virt_to_page(ptr);
  99
 100         idx = virt_to_fix(vaddr);
 101         pte = kmap_pte - (idx - FIX_KMAP_BEGIN);
 102         return pte_page(*pte);
 103 }
 104
 105 EXPORT_SYMBOL(kmap);
 106 EXPORT_SYMBOL(kunmap);
 107 EXPORT_SYMBOL(kmap_atomic);
 108 EXPORT_SYMBOL(kunmap_atomic);
 109 EXPORT_SYMBOL(kmap_atomic_to_page);