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