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  */
  32 void *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 }
  53 EXPORT_SYMBOL(kmap_atomic_prot);
  54
  55 void 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 }
  77 EXPORT_SYMBOL(kunmap_atomic);