LXR linux/arch/powerpc/mm/highmem.c

   1/*
   2 * highmem.c: virtual kernel memory mappings for high memory
   3 *
   4 * PowerPC version, stolen from the i386 version.
   5 *
   6 * Used in CONFIG_HIGHMEM systems for memory pages which
   7 * are not addressable by direct kernel virtual addresses.
   8 *
   9 * Copyright (C) 1999 Gerhard Wichert, Siemens AG
  10 *                    Gerhard.Wichert@pdb.siemens.de
  11 *
  12 *
  13 * Redesigned the x86 32-bit VM architecture to deal with
  14 * up to 16 Terrabyte physical memory. With current x86 CPUs
  15 * we now support up to 64 Gigabytes physical RAM.
  16 *
  17 * Copyright (C) 1999 Ingo Molnar <mingo@redhat.com>
  18 *
  19 * Reworked for PowerPC by various contributors. Moved from
  20 * highmem.h by Benjamin Herrenschmidt (c) 2009 IBM Corp.
  21 */
  22
  23#include <linux/highmem.h>
  24#include <linux/module.h>
  25
  26/*
  27 * The use of kmap_atomic/kunmap_atomic is discouraged - kmap/kunmap
  28 * gives a more generic (and caching) interface. But kmap_atomic can
  29 * be used in IRQ contexts, so in some (very limited) cases we need
  30 * it.
  31 */
  32void *kmap_atomic_prot(struct page *page, enum km_type type, pgprot_t prot)
  33{
  34        unsigned int 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#ifdef CONFIG_DEBUG_HIGHMEM
  46        BUG_ON(!pte_none(*(kmap_pte-idx)));
  47#endif
  48        __set_pte_at(&init_mm, vaddr, kmap_pte-idx, mk_pte(page, prot), 1);
  49        local_flush_tlb_page(NULL, vaddr);
  50
  51        return (void*) vaddr;
  52}
  53EXPORT_SYMBOL(kmap_atomic_prot);
  54
  55void kunmap_atomic(void *kvaddr, enum km_type type)
  56{
  57#ifdef CONFIG_DEBUG_HIGHMEM
  58        unsigned long vaddr = (unsigned long) kvaddr & PAGE_MASK;
  59        enum fixed_addresses idx = type + KM_TYPE_NR*smp_processor_id();
  60
  61        if (vaddr < __fix_to_virt(FIX_KMAP_END)) {
  62                pagefault_enable();
  63                return;
  64        }
  65
  66        BUG_ON(vaddr != __fix_to_virt(FIX_KMAP_BEGIN + idx));
  67
  68        /*
  69         * force other mappings to Oops if they'll try to access
  70         * this pte without first remap it
  71         */
  72        pte_clear(&init_mm, vaddr, kmap_pte-idx);
  73        local_flush_tlb_page(NULL, vaddr);
  74#endif
  75        pagefault_enable();
  76}
  77EXPORT_SYMBOL(kunmap_atomic);
  78