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highmem_32.c

#include <linux/highmem.h>
#include <linux/module.h>

void *kmap(struct page *page)
{
      might_sleep();
      if (!PageHighMem(page))
            return page_address(page);
      return kmap_high(page);
}

void kunmap(struct page *page)
{
      if (in_interrupt())
            BUG();
      if (!PageHighMem(page))
            return;
      kunmap_high(page);
}

/*
 * kmap_atomic/kunmap_atomic is significantly faster than kmap/kunmap because
 * no global lock is needed and because the kmap code must perform a global TLB
 * invalidation when the kmap pool wraps.
 *
 * However when holding an atomic kmap is is not legal to sleep, so atomic
 * kmaps are appropriate for short, tight code paths only.
 */
void *kmap_atomic_prot(struct page *page, enum km_type type, pgprot_t prot)
{
      enum fixed_addresses idx;
      unsigned long vaddr;

      /* even !CONFIG_PREEMPT needs this, for in_atomic in do_page_fault */
      pagefault_disable();

      if (!PageHighMem(page))
            return page_address(page);

      idx = type + KM_TYPE_NR*smp_processor_id();
      vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
      BUG_ON(!pte_none(*(kmap_pte-idx)));
      set_pte(kmap_pte-idx, mk_pte(page, prot));
      arch_flush_lazy_mmu_mode();

      return (void *)vaddr;
}

void *kmap_atomic(struct page *page, enum km_type type)
{
      return kmap_atomic_prot(page, type, kmap_prot);
}

void kunmap_atomic(void *kvaddr, enum km_type type)
{
      unsigned long vaddr = (unsigned long) kvaddr & PAGE_MASK;
      enum fixed_addresses idx = type + KM_TYPE_NR*smp_processor_id();

      /*
       * Force other mappings to Oops if they'll try to access this pte
       * without first remap it.  Keeping stale mappings around is a bad idea
       * also, in case the page changes cacheability attributes or becomes
       * a protected page in a hypervisor.
       */
      if (vaddr == __fix_to_virt(FIX_KMAP_BEGIN+idx))
            kpte_clear_flush(kmap_pte-idx, vaddr);
      else {
#ifdef CONFIG_DEBUG_HIGHMEM
            BUG_ON(vaddr < PAGE_OFFSET);
            BUG_ON(vaddr >= (unsigned long)high_memory);
#endif
      }

      arch_flush_lazy_mmu_mode();
      pagefault_enable();
}

/* This is the same as kmap_atomic() but can map memory that doesn't
 * have a struct page associated with it.
 */
void *kmap_atomic_pfn(unsigned long pfn, enum km_type type)
{
      enum fixed_addresses idx;
      unsigned long vaddr;

      pagefault_disable();

      idx = type + KM_TYPE_NR*smp_processor_id();
      vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
      set_pte(kmap_pte-idx, pfn_pte(pfn, kmap_prot));
      arch_flush_lazy_mmu_mode();

      return (void*) vaddr;
}

struct page *kmap_atomic_to_page(void *ptr)
{
      unsigned long idx, vaddr = (unsigned long)ptr;
      pte_t *pte;

      if (vaddr < FIXADDR_START)
            return virt_to_page(ptr);

      idx = virt_to_fix(vaddr);
      pte = kmap_pte - (idx - FIX_KMAP_BEGIN);
      return pte_page(*pte);
}

EXPORT_SYMBOL(kmap);
EXPORT_SYMBOL(kunmap);
EXPORT_SYMBOL(kmap_atomic);
EXPORT_SYMBOL(kunmap_atomic);
EXPORT_SYMBOL(kmap_atomic_to_page);

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