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/highmem.h>
  26 #include <linux/export.h>
  27 #include <linux/mm.h>
  28
  29 #include <asm/cacheflush.h>
  30 #include <asm/tlbflush.h>
  31 #include <asm/pgalloc.h>
  32 #include <asm/vaddrs.h>
  33
  34 pgprot_t kmap_prot;
  35
  36 static pte_t *kmap_pte;
  37
  38 void __init kmap_init(void)
  39 {
  40         unsigned long address;
  41         pmd_t *dir;
  42
  43         address = __fix_to_virt(FIX_KMAP_BEGIN);
  44         dir = pmd_offset(pgd_offset_k(address), address);
  45
  46         /* cache the first kmap pte */
  47         kmap_pte = pte_offset_kernel(dir, address);
  48         kmap_prot = __pgprot(SRMMU_ET_PTE | SRMMU_PRIV | SRMMU_CACHE);
  49 }
  50
  51 void *kmap_atomic(struct page *page)
  52 {
  53         unsigned long vaddr;
  54         long idx, type;
  55
  56         /* even !CONFIG_PREEMPT needs this, for in_atomic in do_page_fault */
  57         pagefault_disable();
  58         if (!PageHighMem(page))
  59                 return page_address(page);
  60
  61         type = kmap_atomic_idx_push();
  62         idx = type + KM_TYPE_NR*smp_processor_id();
  63         vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
  64
  65 /* XXX Fix - Anton */
  66 #if 0
  67         __flush_cache_one(vaddr);
  68 #else
  69         flush_cache_all();
  70 #endif
  71
  72 #ifdef CONFIG_DEBUG_HIGHMEM
  73         BUG_ON(!pte_none(*(kmap_pte-idx)));
  74 #endif
  75         set_pte(kmap_pte-idx, mk_pte(page, kmap_prot));
  76 /* XXX Fix - Anton */
  77 #if 0
  78         __flush_tlb_one(vaddr);
  79 #else
  80         flush_tlb_all();
  81 #endif
  82
  83         return (void*) vaddr;
  84 }
  85 EXPORT_SYMBOL(kmap_atomic);
  86
  87 void __kunmap_atomic(void *kvaddr)
  88 {
  89         unsigned long vaddr = (unsigned long) kvaddr & PAGE_MASK;
  90         int type;
  91
  92         if (vaddr < FIXADDR_START) { // FIXME
  93                 pagefault_enable();
  94                 return;
  95         }
  96
  97         type = kmap_atomic_idx();
  98
  99 #ifdef CONFIG_DEBUG_HIGHMEM
 100         {
 101                 unsigned long idx;
 102
 103                 idx = type + KM_TYPE_NR * smp_processor_id();
 104                 BUG_ON(vaddr != __fix_to_virt(FIX_KMAP_BEGIN+idx));
 105
 106                 /* XXX Fix - Anton */
 107 #if 0
 108                 __flush_cache_one(vaddr);
 109 #else
 110                 flush_cache_all();
 111 #endif
 112
 113                 /*
 114                  * force other mappings to Oops if they'll try to access
 115                  * this pte without first remap it
 116                  */
 117                 pte_clear(&init_mm, vaddr, kmap_pte-idx);
 118                 /* XXX Fix - Anton */
 119 #if 0
 120                 __flush_tlb_one(vaddr);
 121 #else
 122                 flush_tlb_all();
 123 #endif
 124         }
 125 #endif
 126
 127         kmap_atomic_idx_pop();
 128         pagefault_enable();
 129 }
 130 EXPORT_SYMBOL(__kunmap_atomic);