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