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 <asm/pgalloc.h>
  28 #include <asm/cacheflush.h>
  29 #include <asm/tlbflush.h>
  30 #include <asm/fixmap.h>
  31
  32 void *kmap_atomic(struct page *page, enum km_type type)
  33 {
  34         unsigned long idx;
  35         unsigned long vaddr;
  36
  37         /* even !CONFIG_PREEMPT needs this, for in_atomic in do_page_fault */
  38         pagefault_disable();
  39         if (!PageHighMem(page))
  40                 return page_address(page);
  41
  42         debug_kmap_atomic(type);
  43         idx = type + KM_TYPE_NR*smp_processor_id();
  44         vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
  45
  46 /* XXX Fix - Anton */
  47 #if 0
  48         __flush_cache_one(vaddr);
  49 #else
  50         flush_cache_all();
  51 #endif
  52
  53 #ifdef CONFIG_DEBUG_HIGHMEM
  54         BUG_ON(!pte_none(*(kmap_pte-idx)));
  55 #endif
  56         set_pte(kmap_pte-idx, mk_pte(page, kmap_prot));
  57 /* XXX Fix - Anton */
  58 #if 0
  59         __flush_tlb_one(vaddr);
  60 #else
  61         flush_tlb_all();
  62 #endif
  63
  64         return (void*) vaddr;
  65 }
  66 EXPORT_SYMBOL(kmap_atomic);
  67
  68 void kunmap_atomic(void *kvaddr, enum km_type type)
  69 {
  70 #ifdef CONFIG_DEBUG_HIGHMEM
  71         unsigned long vaddr = (unsigned long) kvaddr & PAGE_MASK;
  72         unsigned long idx = type + KM_TYPE_NR*smp_processor_id();
  73
  74         if (vaddr < FIXADDR_START) { // FIXME
  75                 pagefault_enable();
  76                 return;
  77         }
  78
  79         BUG_ON(vaddr != __fix_to_virt(FIX_KMAP_BEGIN+idx));
  80
  81 /* XXX Fix - Anton */
  82 #if 0
  83         __flush_cache_one(vaddr);
  84 #else
  85         flush_cache_all();
  86 #endif
  87
  88         /*
  89          * force other mappings to Oops if they'll try to access
  90          * this pte without first remap it
  91          */
  92         pte_clear(&init_mm, vaddr, kmap_pte-idx);
  93 /* XXX Fix - Anton */
  94 #if 0
  95         __flush_tlb_one(vaddr);
  96 #else
  97         flush_tlb_all();
  98 #endif
  99 #endif
 100
 101         pagefault_enable();
 102 }
 103 EXPORT_SYMBOL(kunmap_atomic);
 104
 105 /* We may be fed a pagetable here by ptep_to_xxx and others. */
 106 struct page *kmap_atomic_to_page(void *ptr)
 107 {
 108         unsigned long idx, vaddr = (unsigned long)ptr;
 109         pte_t *pte;
 110
 111         if (vaddr < SRMMU_NOCACHE_VADDR)
 112                 return virt_to_page(ptr);
 113         if (vaddr < PKMAP_BASE)
 114                 return pfn_to_page(__nocache_pa(vaddr) >> PAGE_SHIFT);
 115         BUG_ON(vaddr < FIXADDR_START);
 116         BUG_ON(vaddr > FIXADDR_TOP);
 117
 118         idx = virt_to_fix(vaddr);
 119         pte = kmap_pte - (idx - FIX_KMAP_BEGIN);
 120         return pte_page(*pte);
 121 }