arch/powerpc/include/asm/highmem.h

   1 /*
   2  * highmem.h: 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
  20 #ifndef _ASM_HIGHMEM_H
  21 #define _ASM_HIGHMEM_H
  22
  23 #ifdef __KERNEL__
  24
  25 #include <linux/init.h>
  26 #include <linux/interrupt.h>
  27 #include <asm/kmap_types.h>
  28 #include <asm/tlbflush.h>
  29 #include <asm/page.h>
  30 #include <asm/fixmap.h>
  31
  32 extern pte_t *kmap_pte;
  33 extern pgprot_t kmap_prot;
  34 extern pte_t *pkmap_page_table;
  35
  36 /*
  37  * Right now we initialize only a single pte table. It can be extended
  38  * easily, subsequent pte tables have to be allocated in one physical
  39  * chunk of RAM.
  40  */
  41 #define LAST_PKMAP      (1 << PTE_SHIFT)
  42 #define LAST_PKMAP_MASK (LAST_PKMAP-1)
  43 #define PKMAP_BASE      ((FIXADDR_START - PAGE_SIZE*(LAST_PKMAP + 1)) & PMD_MASK)
  44 #define PKMAP_NR(virt)  ((virt-PKMAP_BASE) >> PAGE_SHIFT)
  45 #define PKMAP_ADDR(nr)  (PKMAP_BASE + ((nr) << PAGE_SHIFT))
  46
  47 extern void *kmap_high(struct page *page);
  48 extern void kunmap_high(struct page *page);
  49
  50 static inline void *kmap(struct page *page)
  51 {
  52         might_sleep();
  53         if (!PageHighMem(page))
  54                 return page_address(page);
  55         return kmap_high(page);
  56 }
  57
  58 static inline void kunmap(struct page *page)
  59 {
  60         BUG_ON(in_interrupt());
  61         if (!PageHighMem(page))
  62                 return;
  63         kunmap_high(page);
  64 }
  65
  66 /*
  67  * The use of kmap_atomic/kunmap_atomic is discouraged - kmap/kunmap
  68  * gives a more generic (and caching) interface. But kmap_atomic can
  69  * be used in IRQ contexts, so in some (very limited) cases we need
  70  * it.
  71  */
  72 static inline void *kmap_atomic_prot(struct page *page, enum km_type type, pgprot_t prot)
  73 {
  74         unsigned int idx;
  75         unsigned long vaddr;
  76
  77         /* even !CONFIG_PREEMPT needs this, for in_atomic in do_page_fault */
  78         pagefault_disable();
  79         if (!PageHighMem(page))
  80                 return page_address(page);
  81
  82         idx = type + KM_TYPE_NR*smp_processor_id();
  83         vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
  84 #ifdef CONFIG_DEBUG_HIGHMEM
  85         BUG_ON(!pte_none(*(kmap_pte-idx)));
  86 #endif
  87         __set_pte_at(&init_mm, vaddr, kmap_pte-idx, mk_pte(page, prot));
  88         flush_tlb_page(NULL, vaddr);
  89
  90         return (void*) vaddr;
  91 }
  92
  93 static inline void *kmap_atomic(struct page *page, enum km_type type)
  94 {
  95         return kmap_atomic_prot(page, type, kmap_prot);
  96 }
  97
  98 static inline void kunmap_atomic(void *kvaddr, enum km_type type)
  99 {
 100 #ifdef CONFIG_DEBUG_HIGHMEM
 101         unsigned long vaddr = (unsigned long) kvaddr & PAGE_MASK;
 102         enum fixed_addresses idx = type + KM_TYPE_NR*smp_processor_id();
 103
 104         if (vaddr < __fix_to_virt(FIX_KMAP_END)) {
 105                 pagefault_enable();
 106                 return;
 107         }
 108
 109         BUG_ON(vaddr != __fix_to_virt(FIX_KMAP_BEGIN + idx));
 110
 111         /*
 112          * force other mappings to Oops if they'll try to access
 113          * this pte without first remap it
 114          */
 115         pte_clear(&init_mm, vaddr, kmap_pte-idx);
 116         flush_tlb_page(NULL, vaddr);
 117 #endif
 118         pagefault_enable();
 119 }
 120
 121 static inline struct page *kmap_atomic_to_page(void *ptr)
 122 {
 123         unsigned long idx, vaddr = (unsigned long) ptr;
 124         pte_t *pte;
 125
 126         if (vaddr < FIXADDR_START)
 127                 return virt_to_page(ptr);
 128
 129         idx = virt_to_fix(vaddr);
 130         pte = kmap_pte - (idx - FIX_KMAP_BEGIN);
 131         return pte_page(*pte);
 132 }
 133
 134 #define flush_cache_kmaps()     flush_cache_all()
 135
 136 #endif /* __KERNEL__ */
 137
 138 #endif /* _ASM_HIGHMEM_H */