text: /*
   *  highmem.c: virtual kernel memory mappings for high memory
   *
   *  Provides kernel-static versions of atomic kmap functions originally
   *  found as inlines in include/asm-sparc/highmem.h.  These became
   *  needed as kmap_atomic() and kunmap_atomic() started getting
   *  called from within modules.
   *  -- Tomas Szepe <szepe@pinerecords.com>, September 2002
   *
   *  But kmap_atomic() and kunmap_atomic() cannot be inlined in
   *  modules because they are loaded with btfixup-ped functions.
   */
  
  /*
   * 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.
   *
   * XXX This is an old text. Actually, it's good to use atomic kmaps,
   * provided you remember that they are atomic and not try to sleep
   * with a kmap taken, much like a spinlock. Non-atomic kmaps are
   * shared by CPUs, and so precious, and establishing them requires IPI.
   * Atomic kmaps are lightweight and we may have NCPUS more of them.
   */
  #include <linux/highmem.h>
  #include <linux/export.h>
  #include <linux/mm.h>
  
  #include <asm/cacheflush.h>
  #include <asm/tlbflush.h>
  #include <asm/pgalloc.h>
  #include <asm/vaddrs.h>
  
  pgprot_t kmap_prot;
  
  static pte_t *kmap_pte;
  
  void __init kmap_init(void)
  {
  	unsigned long address;
  	pmd_t *dir;
  
  	address = __fix_to_virt(FIX_KMAP_BEGIN);
  	dir = pmd_offset(pgd_offset_k(address), address);
  
          /* cache the first kmap pte */
          kmap_pte = pte_offset_kernel(dir, address);
          kmap_prot = __pgprot(SRMMU_ET_PTE | SRMMU_PRIV | SRMMU_CACHE);
  }
  
  void *kmap_atomic(struct page *page)
  {
  	unsigned long vaddr;
  	long idx, type;
  
  	/* even !CONFIG_PREEMPT needs this, for in_atomic in do_page_fault */
  	pagefault_disable();
  	if (!PageHighMem(page))
  		return page_address(page);
  
  	type = kmap_atomic_idx_push();
  	idx = type + KM_TYPE_NR*smp_processor_id();
  	vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
  
  /* XXX Fix - Anton */
  #if 0
  	__flush_cache_one(vaddr);
  #else
  	flush_cache_all();
  #endif
  
  #ifdef CONFIG_DEBUG_HIGHMEM
  	BUG_ON(!pte_none(*(kmap_pte-idx)));
  #endif
  	set_pte(kmap_pte-idx, mk_pte(page, kmap_prot));
  /* XXX Fix - Anton */
  #if 0
  	__flush_tlb_one(vaddr);
  #else
  	flush_tlb_all();
  #endif
  
  	return (void*) vaddr;
  }
  EXPORT_SYMBOL(kmap_atomic);
  
  void __kunmap_atomic(void *kvaddr)
  {
  	unsigned long vaddr = (unsigned long) kvaddr & PAGE_MASK;
  	int type;
  
  	if (vaddr < FIXADDR_START) { // FIXME
  		pagefault_enable();
  		return;
  	}
  
  	type = kmap_atomic_idx();
  
  #ifdef CONFIG_DEBUG_HIGHMEM
  	{
  		unsigned long idx;
  
  		idx = type + KM_TYPE_NR * smp_processor_id();
  		BUG_ON(vaddr != __fix_to_virt(FIX_KMAP_BEGIN+idx));
  
  		/* XXX Fix - Anton */
  #if 0
  		__flush_cache_one(vaddr);
  #else
  		flush_cache_all();
  #endif
  
  		/*
  		 * 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);
  		/* XXX Fix - Anton */
  #if 0
  		__flush_tlb_one(vaddr);
  #else
  		flush_tlb_all();
  #endif
  	}
  #endif
  
  	kmap_atomic_idx_pop();
  	pagefault_enable();
  }
  EXPORT_SYMBOL(__kunmap_atomic);
  