arch/x86/mm/highmem_32.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 static void debug_kmap_atomic_prot(enum km_type type)
  22 {
  23 #ifdef CONFIG_DEBUG_HIGHMEM
  24         static unsigned warn_count = 10;
  25
  26         if (unlikely(warn_count == 0))
  27                 return;
  28
  29         if (unlikely(in_interrupt())) {
  30                 if (in_irq()) {
  31                         if (type != KM_IRQ0 && type != KM_IRQ1 &&
  32                             type != KM_BIO_SRC_IRQ && type != KM_BIO_DST_IRQ &&
  33                             type != KM_BOUNCE_READ) {
  34                                 WARN_ON(1);
  35                                 warn_count--;
  36                         }
  37                 } else if (!irqs_disabled()) {  /* softirq */
  38                         if (type != KM_IRQ0 && type != KM_IRQ1 &&
  39                             type != KM_SOFTIRQ0 && type != KM_SOFTIRQ1 &&
  40                             type != KM_SKB_SUNRPC_DATA &&
  41                             type != KM_SKB_DATA_SOFTIRQ &&
  42                             type != KM_BOUNCE_READ) {
  43                                 WARN_ON(1);
  44                                 warn_count--;
  45                         }
  46                 }
  47         }
  48
  49         if (type == KM_IRQ0 || type == KM_IRQ1 || type == KM_BOUNCE_READ ||
  50                         type == KM_BIO_SRC_IRQ || type == KM_BIO_DST_IRQ) {
  51                 if (!irqs_disabled()) {
  52                         WARN_ON(1);
  53                         warn_count--;
  54                 }
  55         } else if (type == KM_SOFTIRQ0 || type == KM_SOFTIRQ1) {
  56                 if (irq_count() == 0 && !irqs_disabled()) {
  57                         WARN_ON(1);
  58                         warn_count--;
  59                 }
  60         }
  61 #endif
  62 }
  63
  64 /*
  65  * kmap_atomic/kunmap_atomic is significantly faster than kmap/kunmap because
  66  * no global lock is needed and because the kmap code must perform a global TLB
  67  * invalidation when the kmap pool wraps.
  68  *
  69  * However when holding an atomic kmap is is not legal to sleep, so atomic
  70  * kmaps are appropriate for short, tight code paths only.
  71  */
  72 void *kmap_atomic_prot(struct page *page, enum km_type type, pgprot_t prot)
  73 {
  74         enum fixed_addresses idx;
  75         unsigned long vaddr;
  76         /* even !CONFIG_PREEMPT needs this, for in_atomic in do_page_fault */
  77
  78         debug_kmap_atomic_prot(type);
  79
  80         pagefault_disable();
  81
  82         if (!PageHighMem(page))
  83                 return page_address(page);
  84
  85         idx = type + KM_TYPE_NR*smp_processor_id();
  86         vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
  87         BUG_ON(!pte_none(*(kmap_pte-idx)));
  88         set_pte(kmap_pte-idx, mk_pte(page, prot));
  89         arch_flush_lazy_mmu_mode();
  90
  91         return (void *)vaddr;
  92 }
  93
  94 void *kmap_atomic(struct page *page, enum km_type type)
  95 {
  96         return kmap_atomic_prot(page, type, kmap_prot);
  97 }
  98
  99 void kunmap_atomic(void *kvaddr, enum km_type type)
 100 {
 101         unsigned long vaddr = (unsigned long) kvaddr & PAGE_MASK;
 102         enum fixed_addresses idx = type + KM_TYPE_NR*smp_processor_id();
 103
 104         /*
 105          * Force other mappings to Oops if they'll try to access this pte
 106          * without first remap it.  Keeping stale mappings around is a bad idea
 107          * also, in case the page changes cacheability attributes or becomes
 108          * a protected page in a hypervisor.
 109          */
 110         if (vaddr == __fix_to_virt(FIX_KMAP_BEGIN+idx))
 111                 kpte_clear_flush(kmap_pte-idx, vaddr);
 112         else {
 113 #ifdef CONFIG_DEBUG_HIGHMEM
 114                 BUG_ON(vaddr < PAGE_OFFSET);
 115                 BUG_ON(vaddr >= (unsigned long)high_memory);
 116 #endif
 117         }
 118
 119         arch_flush_lazy_mmu_mode();
 120         pagefault_enable();
 121 }
 122
 123 /* This is the same as kmap_atomic() but can map memory that doesn't
 124  * have a struct page associated with it.
 125  */
 126 void *kmap_atomic_pfn(unsigned long pfn, enum km_type type)
 127 {
 128         enum fixed_addresses idx;
 129         unsigned long vaddr;
 130
 131         pagefault_disable();
 132
 133         idx = type + KM_TYPE_NR*smp_processor_id();
 134         vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
 135         set_pte(kmap_pte-idx, pfn_pte(pfn, kmap_prot));
 136         arch_flush_lazy_mmu_mode();
 137
 138         return (void*) vaddr;
 139 }
 140
 141 struct page *kmap_atomic_to_page(void *ptr)
 142 {
 143         unsigned long idx, vaddr = (unsigned long)ptr;
 144         pte_t *pte;
 145
 146         if (vaddr < FIXADDR_START)
 147                 return virt_to_page(ptr);
 148
 149         idx = virt_to_fix(vaddr);
 150         pte = kmap_pte - (idx - FIX_KMAP_BEGIN);
 151         return pte_page(*pte);
 152 }
 153
 154 EXPORT_SYMBOL(kmap);
 155 EXPORT_SYMBOL(kunmap);
 156 EXPORT_SYMBOL(kmap_atomic);
 157 EXPORT_SYMBOL(kunmap_atomic);
 158 EXPORT_SYMBOL(kmap_atomic_to_page);