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         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                 pagefault_enable();
  74                 return;
  75         }
  76
  77         BUG_ON(vaddr != __fix_to_virt(FIX_KMAP_BEGIN+idx));
  78
  79 /* XXX Fix - Anton */
  80 #if 0
  81         __flush_cache_one(vaddr);
  82 #else
  83         flush_cache_all();
  84 #endif
  85
  86         /*
  87          * force other mappings to Oops if they'll try to access
  88          * this pte without first remap it
  89          */
  90         pte_clear(&init_mm, vaddr, kmap_pte-idx);
  91 /* XXX Fix - Anton */
  92 #if 0
  93         __flush_tlb_one(vaddr);
  94 #else
  95         flush_tlb_all();
  96 #endif
  97 #endif
  98
  99         pagefault_enable();
 100 }
 101
 102 /* We may be fed a pagetable here by ptep_to_xxx and others. */
 103 struct page *kmap_atomic_to_page(void *ptr)
 104 {
 105         unsigned long idx, vaddr = (unsigned long)ptr;
 106         pte_t *pte;
 107
 108         if (vaddr < SRMMU_NOCACHE_VADDR)
 109                 return virt_to_page(ptr);
 110         if (vaddr < PKMAP_BASE)
 111                 return pfn_to_page(__nocache_pa(vaddr) >> PAGE_SHIFT);
 112         BUG_ON(vaddr < FIXADDR_START);
 113         BUG_ON(vaddr > FIXADDR_TOP);
 114
 115         idx = virt_to_fix(vaddr);
 116         pte = kmap_pte - (idx - FIX_KMAP_BEGIN);
 117         return pte_page(*pte);
 118 }