include/asm-powerpc/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
  31 /* undef for production */
  32 #define HIGHMEM_DEBUG 1
  33
  34 extern pte_t *kmap_pte;
  35 extern pgprot_t kmap_prot;
  36 extern pte_t *pkmap_page_table;
  37
  38 /*
  39  * Right now we initialize only a single pte table. It can be extended
  40  * easily, subsequent pte tables have to be allocated in one physical
  41  * chunk of RAM.
  42  */
  43 #define PKMAP_BASE      CONFIG_HIGHMEM_START
  44 #define LAST_PKMAP      (1 << PTE_SHIFT)
  45 #define LAST_PKMAP_MASK (LAST_PKMAP-1)
  46 #define PKMAP_NR(virt)  ((virt-PKMAP_BASE) >> PAGE_SHIFT)
  47 #define PKMAP_ADDR(nr)  (PKMAP_BASE + ((nr) << PAGE_SHIFT))
  48
  49 #define KMAP_FIX_BEGIN  (PKMAP_BASE + 0x00400000UL)
  50
  51 extern void *kmap_high(struct page *page);
  52 extern void kunmap_high(struct page *page);
  53
  54 static inline void *kmap(struct page *page)
  55 {
  56         might_sleep();
  57         if (!PageHighMem(page))
  58                 return page_address(page);
  59         return kmap_high(page);
  60 }
  61
  62 static inline void kunmap(struct page *page)
  63 {
  64         BUG_ON(in_interrupt());
  65         if (!PageHighMem(page))
  66                 return;
  67         kunmap_high(page);
  68 }
  69
  70 /*
  71  * The use of kmap_atomic/kunmap_atomic is discouraged - kmap/kunmap
  72  * gives a more generic (and caching) interface. But kmap_atomic can
  73  * be used in IRQ contexts, so in some (very limited) cases we need
  74  * it.
  75  */
  76 static inline void *kmap_atomic(struct page *page, enum km_type type)
  77 {
  78         unsigned int idx;
  79         unsigned long vaddr;
  80
  81         /* even !CONFIG_PREEMPT needs this, for in_atomic in do_page_fault */
  82         pagefault_disable();
  83         if (!PageHighMem(page))
  84                 return page_address(page);
  85
  86         idx = type + KM_TYPE_NR*smp_processor_id();
  87         vaddr = KMAP_FIX_BEGIN + idx * PAGE_SIZE;
  88 #ifdef HIGHMEM_DEBUG
  89         BUG_ON(!pte_none(*(kmap_pte+idx)));
  90 #endif
  91         set_pte_at(&init_mm, vaddr, kmap_pte+idx, mk_pte(page, kmap_prot));
  92         flush_tlb_page(NULL, vaddr);
  93
  94         return (void*) vaddr;
  95 }
  96
  97 static inline void kunmap_atomic(void *kvaddr, enum km_type type)
  98 {
  99 #ifdef HIGHMEM_DEBUG
 100         unsigned long vaddr = (unsigned long) kvaddr & PAGE_MASK;
 101         unsigned int idx = type + KM_TYPE_NR*smp_processor_id();
 102
 103         if (vaddr < KMAP_FIX_BEGIN) { // FIXME
 104                 pagefault_enable();
 105                 return;
 106         }
 107
 108         BUG_ON(vaddr != KMAP_FIX_BEGIN + idx * PAGE_SIZE);
 109
 110         /*
 111          * force other mappings to Oops if they'll try to access
 112          * this pte without first remap it
 113          */
 114         pte_clear(&init_mm, vaddr, kmap_pte+idx);
 115         flush_tlb_page(NULL, vaddr);
 116 #endif
 117         pagefault_enable();
 118 }
 119
 120 static inline struct page *kmap_atomic_to_page(void *ptr)
 121 {
 122         unsigned long idx, vaddr = (unsigned long) ptr;
 123
 124         if (vaddr < KMAP_FIX_BEGIN)
 125                 return virt_to_page(ptr);
 126
 127         idx = (vaddr - KMAP_FIX_BEGIN) >> PAGE_SHIFT;
 128         return pte_page(kmap_pte[idx]);
 129 }
 130
 131 #define flush_cache_kmaps()     flush_cache_all()
 132
 133 #endif /* __KERNEL__ */
 134
 135 #endif /* _ASM_HIGHMEM_H */