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highmem.h

/*
 * highmem.h: virtual kernel memory mappings for high memory
 *
 * PowerPC version, stolen from the i386 version.
 *
 * Used in CONFIG_HIGHMEM systems for memory pages which
 * are not addressable by direct kernel virtual addresses.
 *
 * Copyright (C) 1999 Gerhard Wichert, Siemens AG
 *                Gerhard.Wichert@pdb.siemens.de
 *
 *
 * Redesigned the x86 32-bit VM architecture to deal with
 * up to 16 Terrabyte physical memory. With current x86 CPUs
 * we now support up to 64 Gigabytes physical RAM.
 *
 * Copyright (C) 1999 Ingo Molnar <mingo@redhat.com>
 */

#ifndef _ASM_HIGHMEM_H
#define _ASM_HIGHMEM_H

#ifdef __KERNEL__

#include <linux/init.h>
#include <linux/interrupt.h>
#include <asm/kmap_types.h>
#include <asm/tlbflush.h>
#include <asm/page.h>
#include <asm/fixmap.h>

extern pte_t *kmap_pte;
extern pgprot_t kmap_prot;
extern pte_t *pkmap_page_table;

/*
 * Right now we initialize only a single pte table. It can be extended
 * easily, subsequent pte tables have to be allocated in one physical
 * chunk of RAM.
 */
#define LAST_PKMAP      (1 << PTE_SHIFT)
#define LAST_PKMAP_MASK (LAST_PKMAP-1)
#define PKMAP_BASE      ((FIXADDR_START - PAGE_SIZE*(LAST_PKMAP + 1)) & PMD_MASK)
#define PKMAP_NR(virt)  ((virt-PKMAP_BASE) >> PAGE_SHIFT)
#define PKMAP_ADDR(nr)  (PKMAP_BASE + ((nr) << PAGE_SHIFT))

extern void *kmap_high(struct page *page);
extern void kunmap_high(struct page *page);

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

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

/*
 * The use of kmap_atomic/kunmap_atomic is discouraged - kmap/kunmap
 * gives a more generic (and caching) interface. But kmap_atomic can
 * be used in IRQ contexts, so in some (very limited) cases we need
 * it.
 */
static inline void *kmap_atomic_prot(struct page *page, enum km_type type, pgprot_t prot)
{
      unsigned int 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);
#ifdef CONFIG_DEBUG_HIGHMEM
      BUG_ON(!pte_none(*(kmap_pte-idx)));
#endif
      set_pte_at(&init_mm, vaddr, kmap_pte-idx, mk_pte(page, prot));
      flush_tlb_page(NULL, vaddr);

      return (void*) vaddr;
}

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

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

      if (vaddr < __fix_to_virt(FIX_KMAP_END)) {
            pagefault_enable();
            return;
      }

      BUG_ON(vaddr != __fix_to_virt(FIX_KMAP_BEGIN + idx));

      /*
       * force other mappings to Oops if they'll try to access
       * this pte without first remap it
       */
      pte_clear(&init_mm, vaddr, kmap_pte-idx);
      flush_tlb_page(NULL, vaddr);
#endif
      pagefault_enable();
}

static inline 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);
}

#define flush_cache_kmaps()   flush_cache_all()

#endif /* __KERNEL__ */

#endif /* _ASM_HIGHMEM_H */

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