arch/i386/mm/highmem.c

   1 #include <linux/highmem.h>
   2
   3 void *kmap(struct page *page)
   4 {
   5         might_sleep();
   6         if (!PageHighMem(page))
   7                 return page_address(page);
   8         return kmap_high(page);
   9 }
  10
  11 void kunmap(struct page *page)
  12 {
  13         if (in_interrupt())
  14                 BUG();
  15         if (!PageHighMem(page))
  16                 return;
  17         kunmap_high(page);
  18 }
  19
  20 /*
  21  * kmap_atomic/kunmap_atomic is significantly faster than kmap/kunmap because
  22  * no global lock is needed and because the kmap code must perform a global TLB
  23  * invalidation when the kmap pool wraps.
  24  *
  25  * However when holding an atomic kmap is is not legal to sleep, so atomic
  26  * kmaps are appropriate for short, tight code paths only.
  27  */
  28 void *kmap_atomic(struct page *page, enum km_type type)
  29 {
  30         enum fixed_addresses idx;
  31         unsigned long vaddr;
  32
  33         /* even !CONFIG_PREEMPT needs this, for in_atomic in do_page_fault */
  34         inc_preempt_count();
  35         if (!PageHighMem(page))
  36                 return page_address(page);
  37
  38         idx = type + KM_TYPE_NR*smp_processor_id();
  39         vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
  40 #ifdef CONFIG_DEBUG_HIGHMEM
  41         if (!pte_none(*(kmap_pte-idx)))
  42                 BUG();
  43 #endif
  44         set_pte(kmap_pte-idx, mk_pte(page, kmap_prot));
  45         __flush_tlb_one(vaddr);
  46
  47         return (void*) vaddr;
  48 }
  49
  50 void kunmap_atomic(void *kvaddr, enum km_type type)
  51 {
  52 #ifdef CONFIG_DEBUG_HIGHMEM
  53         unsigned long vaddr = (unsigned long) kvaddr & PAGE_MASK;
  54         enum fixed_addresses idx = type + KM_TYPE_NR*smp_processor_id();
  55
  56         if (vaddr < FIXADDR_START) { // FIXME
  57                 dec_preempt_count();
  58                 preempt_check_resched();
  59                 return;
  60         }
  61
  62         if (vaddr != __fix_to_virt(FIX_KMAP_BEGIN+idx))
  63                 BUG();
  64
  65         /*
  66          * force other mappings to Oops if they'll try to access
  67          * this pte without first remap it
  68          */
  69         pte_clear(&init_mm, vaddr, kmap_pte-idx);
  70         __flush_tlb_one(vaddr);
  71 #endif
  72
  73         dec_preempt_count();
  74         preempt_check_resched();
  75 }
  76
  77 struct page *kmap_atomic_to_page(void *ptr)
  78 {
  79         unsigned long idx, vaddr = (unsigned long)ptr;
  80         pte_t *pte;
  81
  82         if (vaddr < FIXADDR_START)
  83                 return virt_to_page(ptr);
  84
  85         idx = virt_to_fix(vaddr);
  86         pte = kmap_pte - (idx - FIX_KMAP_BEGIN);
  87         return pte_page(*pte);
  88 }
  89