LXR linux/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
  34pgprot_t kmap_prot;
  35
  36static pte_t *kmap_pte;
  37
  38void __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
  51void *kmap_atomic(struct page *page)
  52{
  53        unsigned long vaddr;
  54        long idx, type;
  55
  56        preempt_disable();
  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}
  85EXPORT_SYMBOL(kmap_atomic);
  86
  87void __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                preempt_enable();
  95                return;
  96        }
  97
  98        type = kmap_atomic_idx();
  99
 100#ifdef CONFIG_DEBUG_HIGHMEM
 101        {
 102                unsigned long idx;
 103
 104                idx = type + KM_TYPE_NR * smp_processor_id();
 105                BUG_ON(vaddr != __fix_to_virt(FIX_KMAP_BEGIN+idx));
 106
 107                /* XXX Fix - Anton */
 108#if 0
 109                __flush_cache_one(vaddr);
 110#else
 111                flush_cache_all();
 112#endif
 113
 114                /*
 115                 * force other mappings to Oops if they'll try to access
 116                 * this pte without first remap it
 117                 */
 118                pte_clear(&init_mm, vaddr, kmap_pte-idx);
 119                /* XXX Fix - Anton */
 120#if 0
 121                __flush_tlb_one(vaddr);
 122#else
 123                flush_tlb_all();
 124#endif
 125        }
 126#endif
 127
 128        kmap_atomic_idx_pop();
 129        pagefault_enable();
 130        preempt_enable();
 131}
 132EXPORT_SYMBOL(__kunmap_atomic);
 133