include/asm-ppc/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 extern void kmap_init(void) __init;
  39
  40 /*
  41  * Right now we initialize only a single pte table. It can be extended
  42  * easily, subsequent pte tables have to be allocated in one physical
  43  * chunk of RAM.
  44  */
  45 #define PKMAP_BASE      CONFIG_HIGHMEM_START
  46 #define LAST_PKMAP      (1 << PTE_SHIFT)
  47 #define LAST_PKMAP_MASK (LAST_PKMAP-1)
  48 #define PKMAP_NR(virt)  ((virt-PKMAP_BASE) >> PAGE_SHIFT)
  49 #define PKMAP_ADDR(nr)  (PKMAP_BASE + ((nr) << PAGE_SHIFT))
  50
  51 #define KMAP_FIX_BEGIN  (PKMAP_BASE + 0x00400000UL)
  52
  53 extern void *kmap_high(struct page *page);
  54 extern void kunmap_high(struct page *page);
  55
  56 static inline void *kmap(struct page *page)
  57 {
  58         might_sleep();
  59         if (page < highmem_start_page)
  60                 return page_address(page);
  61         return kmap_high(page);
  62 }
  63
  64 static inline void kunmap(struct page *page)
  65 {
  66         BUG_ON(in_interrupt());
  67         if (page < highmem_start_page)
  68                 return;
  69         kunmap_high(page);
  70 }
  71
  72 /*
  73  * The use of kmap_atomic/kunmap_atomic is discouraged - kmap/kunmap
  74  * gives a more generic (and caching) interface. But kmap_atomic can
  75  * be used in IRQ contexts, so in some (very limited) cases we need
  76  * it.
  77  */
  78 static inline void *kmap_atomic(struct page *page, enum km_type type)
  79 {
  80         unsigned int idx;
  81         unsigned long vaddr;
  82
  83         /* even !CONFIG_PREEMPT needs this, for in_atomic in do_page_fault */
  84         inc_preempt_count();
  85         if (page < highmem_start_page)
  86                 return page_address(page);
  87
  88         idx = type + KM_TYPE_NR*smp_processor_id();
  89         vaddr = KMAP_FIX_BEGIN + idx * PAGE_SIZE;
  90 #ifdef HIGHMEM_DEBUG
  91         BUG_ON(!pte_none(*(kmap_pte+idx)));
  92 #endif
  93         set_pte(kmap_pte+idx, mk_pte(page, kmap_prot));
  94         flush_tlb_page(NULL, vaddr);
  95
  96         return (void*) vaddr;
  97 }
  98
  99 static inline void kunmap_atomic(void *kvaddr, enum km_type type)
 100 {
 101 #ifdef HIGHMEM_DEBUG
 102         unsigned long vaddr = (unsigned long) kvaddr & PAGE_MASK;
 103         unsigned int idx = type + KM_TYPE_NR*smp_processor_id();
 104
 105         if (vaddr < KMAP_FIX_BEGIN) { // FIXME
 106                 dec_preempt_count();
 107                 preempt_check_resched();
 108                 return;
 109         }
 110
 111         BUG_ON(vaddr != KMAP_FIX_BEGIN + idx * PAGE_SIZE);
 112
 113         /*
 114          * force other mappings to Oops if they'll try to access
 115          * this pte without first remap it
 116          */
 117         pte_clear(kmap_pte+idx);
 118         flush_tlb_page(NULL, vaddr);
 119 #endif
 120         dec_preempt_count();
 121         preempt_check_resched();
 122 }
 123
 124 static inline struct page *kmap_atomic_to_page(void *ptr)
 125 {
 126         unsigned long idx, vaddr = (unsigned long) ptr;
 127
 128         if (vaddr < KMAP_FIX_BEGIN)
 129                 return virt_to_page(ptr);
 130
 131         idx = (vaddr - KMAP_FIX_BEGIN) >> PAGE_SHIFT;
 132         return pte_page(kmap_pte[idx]);
 133 }
 134
 135 #define flush_cache_kmaps()     flush_cache_all()
 136
 137 #endif /* __KERNEL__ */
 138
 139 #endif /* _ASM_HIGHMEM_H */