arch/microblaze/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/export.h>
  24 #include <linux/highmem.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 #include <asm/tlbflush.h>
  33
  34 void *kmap_atomic_prot(struct page *page, pgprot_t prot)
  35 {
  36
  37         unsigned long vaddr;
  38         int idx, type;
  39
  40         /* even !CONFIG_PREEMPT needs this, for in_atomic in do_page_fault */
  41         pagefault_disable();
  42         if (!PageHighMem(page))
  43                 return page_address(page);
  44
  45
  46         type = kmap_atomic_idx_push();
  47         idx = type + KM_TYPE_NR*smp_processor_id();
  48         vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
  49 #ifdef CONFIG_DEBUG_HIGHMEM
  50         BUG_ON(!pte_none(*(kmap_pte-idx)));
  51 #endif
  52         set_pte_at(&init_mm, vaddr, kmap_pte-idx, mk_pte(page, prot));
  53         local_flush_tlb_page(NULL, vaddr);
  54
  55         return (void *) vaddr;
  56 }
  57 EXPORT_SYMBOL(kmap_atomic_prot);
  58
  59 void __kunmap_atomic(void *kvaddr)
  60 {
  61         unsigned long vaddr = (unsigned long) kvaddr & PAGE_MASK;
  62         int type;
  63
  64         if (vaddr < __fix_to_virt(FIX_KMAP_END)) {
  65                 pagefault_enable();
  66                 return;
  67         }
  68
  69         type = kmap_atomic_idx();
  70 #ifdef CONFIG_DEBUG_HIGHMEM
  71         {
  72                 unsigned int idx;
  73
  74                 idx = type + KM_TYPE_NR * smp_processor_id();
  75                 BUG_ON(vaddr != __fix_to_virt(FIX_KMAP_BEGIN + idx));
  76
  77                 /*
  78                  * force other mappings to Oops if they'll try to access
  79                  * this pte without first remap it
  80                  */
  81                 pte_clear(&init_mm, vaddr, kmap_pte-idx);
  82                 local_flush_tlb_page(NULL, vaddr);
  83         }
  84 #endif
  85         kmap_atomic_idx_pop();
  86         pagefault_enable();
  87 }
  88 EXPORT_SYMBOL(__kunmap_atomic);