arch/sparc/mm/highmem.c

   1 /*
   2  *  highmem.c: virtual kernel memory mappings for high memory
   3  *
   4  *  Provides kernel-static versions of atomic kmap functions originally
   5  *  found as inlines in include/asm-sparc/highmem.h.  These became
   6  *  needed as kmap_atomic() and kunmap_atomic() started getting
   7  *  called from within modules.
   8  *  -- Tomas Szepe <szepe@pinerecords.com>, September 2002
   9  *
  10  *  But kmap_atomic() and kunmap_atomic() cannot be inlined in
  11  *  modules because they are loaded with btfixup-ped functions.
  12  */
  13
  14 /*
  15  * The use of kmap_atomic/kunmap_atomic is discouraged - kmap/kunmap
  16  * gives a more generic (and caching) interface. But kmap_atomic can
  17  * be used in IRQ contexts, so in some (very limited) cases we need it.
  18  *
  19  * XXX This is an old text. Actually, it's good to use atomic kmaps,
  20  * provided you remember that they are atomic and not try to sleep
  21  * with a kmap taken, much like a spinlock. Non-atomic kmaps are
  22  * shared by CPUs, and so precious, and establishing them requires IPI.
  23  * Atomic kmaps are lightweight and we may have NCPUS more of them.
  24  */
  25 #include <linux/mm.h>
  26 #include <linux/highmem.h>
  27 #include <linux/export.h>
  28 #include <asm/pgalloc.h>
  29 #include <asm/cacheflush.h>
  30 #include <asm/tlbflush.h>
  31 #include <asm/fixmap.h>
  32
  33 void *kmap_atomic(struct page *page)
  34 {
  35         unsigned long vaddr;
  36         long idx, type;
  37
  38         /* even !CONFIG_PREEMPT needs this, for in_atomic in do_page_fault */
  39         pagefault_disable();
  40         if (!PageHighMem(page))
  41                 return page_address(page);
  42
  43         type = kmap_atomic_idx_push();
  44         idx = type + KM_TYPE_NR*smp_processor_id();
  45         vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
  46
  47 /* XXX Fix - Anton */
  48 #if 0
  49         __flush_cache_one(vaddr);
  50 #else
  51         flush_cache_all();
  52 #endif
  53
  54 #ifdef CONFIG_DEBUG_HIGHMEM
  55         BUG_ON(!pte_none(*(kmap_pte-idx)));
  56 #endif
  57         set_pte(kmap_pte-idx, mk_pte(page, kmap_prot));
  58 /* XXX Fix - Anton */
  59 #if 0
  60         __flush_tlb_one(vaddr);
  61 #else
  62         flush_tlb_all();
  63 #endif
  64
  65         return (void*) vaddr;
  66 }
  67 EXPORT_SYMBOL(kmap_atomic);
  68
  69 void __kunmap_atomic(void *kvaddr)
  70 {
  71         unsigned long vaddr = (unsigned long) kvaddr & PAGE_MASK;
  72         int type;
  73
  74         if (vaddr < FIXADDR_START) { // FIXME
  75                 pagefault_enable();
  76                 return;
  77         }
  78
  79         type = kmap_atomic_idx();
  80
  81 #ifdef CONFIG_DEBUG_HIGHMEM
  82         {
  83                 unsigned long idx;
  84
  85                 idx = type + KM_TYPE_NR * smp_processor_id();
  86                 BUG_ON(vaddr != __fix_to_virt(FIX_KMAP_BEGIN+idx));
  87
  88                 /* XXX Fix - Anton */
  89 #if 0
  90                 __flush_cache_one(vaddr);
  91 #else
  92                 flush_cache_all();
  93 #endif
  94
  95                 /*
  96                  * force other mappings to Oops if they'll try to access
  97                  * this pte without first remap it
  98                  */
  99                 pte_clear(&init_mm, vaddr, kmap_pte-idx);
 100                 /* XXX Fix - Anton */
 101 #if 0
 102                 __flush_tlb_one(vaddr);
 103 #else
 104                 flush_tlb_all();
 105 #endif
 106         }
 107 #endif
 108
 109         kmap_atomic_idx_pop();
 110         pagefault_enable();
 111 }
 112 EXPORT_SYMBOL(__kunmap_atomic);
 113
 114 /* We may be fed a pagetable here by ptep_to_xxx and others. */
 115 struct page *kmap_atomic_to_page(void *ptr)
 116 {
 117         unsigned long idx, vaddr = (unsigned long)ptr;
 118         pte_t *pte;
 119
 120         if (vaddr < SRMMU_NOCACHE_VADDR)
 121                 return virt_to_page(ptr);
 122         if (vaddr < PKMAP_BASE)
 123                 return pfn_to_page(__nocache_pa(vaddr) >> PAGE_SHIFT);
 124         BUG_ON(vaddr < FIXADDR_START);
 125         BUG_ON(vaddr > FIXADDR_TOP);
 126
 127         idx = virt_to_fix(vaddr);
 128         pte = kmap_pte - (idx - FIX_KMAP_BEGIN);
 129         return pte_page(*pte);
 130 }