arch/i386/mm/highmem.c

   1 #include <linux/highmem.h>
   2
   3 void *kmap(struct page *page)
   4 {
   5         might_sleep();
   6         if (page < highmem_start_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 (page < highmem_start_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 (page < highmem_start_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         /*
  45          * If the page is not a normal RAM page, then map it
  46          * uncached to be on the safe side - it could be device
  47          * memory that must not be prefetched:
  48          */
  49         if (PageReserved(page))
  50                 set_pte(kmap_pte-idx, mk_pte(page, kmap_prot_nocache));
  51         else
  52                 set_pte(kmap_pte-idx, mk_pte(page, kmap_prot));
  53         __flush_tlb_one(vaddr);
  54
  55         return (void*) vaddr;
  56 }
  57
  58 /*
  59  * page frame number based kmaps - useful for PCI mappings.
  60  * NOTE: we map the page with the dont-cache flag.
  61  */
  62 void *kmap_atomic_nocache_pfn(unsigned long pfn, enum km_type type)
  63 {
  64         enum fixed_addresses idx;
  65         unsigned long vaddr;
  66
  67         /* even !CONFIG_PREEMPT needs this, for in_atomic in do_page_fault */
  68         inc_preempt_count();
  69         if (pfn < highstart_pfn)
  70                 return pfn_to_kaddr(pfn);
  71
  72         idx = type + KM_TYPE_NR*smp_processor_id();
  73         vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
  74 #ifdef CONFIG_DEBUG_HIGHMEM
  75         if (!pte_none(*(kmap_pte-idx)))
  76                 BUG();
  77 #endif
  78         set_pte(kmap_pte-idx, pfn_pte(pfn, kmap_prot_nocache));
  79         __flush_tlb_one(vaddr);
  80
  81         return (void*) vaddr;
  82 }
  83
  84
  85 void kunmap_atomic(void *kvaddr, enum km_type type)
  86 {
  87 #ifdef CONFIG_DEBUG_HIGHMEM
  88         unsigned long vaddr = (unsigned long) kvaddr & PAGE_MASK;
  89         enum fixed_addresses idx = type + KM_TYPE_NR*smp_processor_id();
  90
  91         if (vaddr < FIXADDR_START) { // FIXME
  92                 dec_preempt_count();
  93                 preempt_check_resched();
  94                 return;
  95         }
  96
  97         if (vaddr != __fix_to_virt(FIX_KMAP_BEGIN+idx))
  98                 BUG();
  99
 100         /*
 101          * force other mappings to Oops if they'll try to access
 102          * this pte without first remap it
 103          */
 104         pte_clear(kmap_pte-idx);
 105         __flush_tlb_one(vaddr);
 106 #endif
 107
 108         dec_preempt_count();
 109         preempt_check_resched();
 110 }
 111
 112 struct page *kmap_atomic_to_page(void *ptr)
 113 {
 114         unsigned long idx, vaddr = (unsigned long)ptr;
 115         pte_t *pte;
 116
 117         if (vaddr < FIXADDR_START)
 118                 return virt_to_page(ptr);
 119
 120         idx = virt_to_fix(vaddr);
 121         pte = kmap_pte - (idx - FIX_KMAP_BEGIN);
 122         return pte_page(*pte);
 123 }
 124