include/asm-um/fixmap.h

   1 #ifndef __UM_FIXMAP_H
   2 #define __UM_FIXMAP_H
   3
   4 #include <asm/system.h>
   5 #include <asm/kmap_types.h>
   6 #include <asm/archparam.h>
   7 #include <asm/page.h>
   8
   9 /*
  10  * Here we define all the compile-time 'special' virtual
  11  * addresses. The point is to have a constant address at
  12  * compile time, but to set the physical address only
  13  * in the boot process. We allocate these special  addresses
  14  * from the end of virtual memory (0xfffff000) backwards.
  15  * Also this lets us do fail-safe vmalloc(), we
  16  * can guarantee that these special addresses and
  17  * vmalloc()-ed addresses never overlap.
  18  *
  19  * these 'compile-time allocated' memory buffers are
  20  * fixed-size 4k pages. (or larger if used with an increment
  21  * highger than 1) use fixmap_set(idx,phys) to associate
  22  * physical memory with fixmap indices.
  23  *
  24  * TLB entries of such buffers will not be flushed across
  25  * task switches.
  26  */
  27
  28 /*
  29  * on UP currently we will have no trace of the fixmap mechanizm,
  30  * no page table allocations, etc. This might change in the
  31  * future, say framebuffers for the console driver(s) could be
  32  * fix-mapped?
  33  */
  34 enum fixed_addresses {
  35 #ifdef CONFIG_HIGHMEM
  36         FIX_KMAP_BEGIN, /* reserved pte's for temporary kernel mappings */
  37         FIX_KMAP_END = FIX_KMAP_BEGIN+(KM_TYPE_NR*NR_CPUS)-1,
  38 #endif
  39         __end_of_fixed_addresses
  40 };
  41
  42 extern void __set_fixmap (enum fixed_addresses idx,
  43                           unsigned long phys, pgprot_t flags);
  44
  45 #define set_fixmap(idx, phys) \
  46                 __set_fixmap(idx, phys, PAGE_KERNEL)
  47 /*
  48  * Some hardware wants to get fixmapped without caching.
  49  */
  50 #define set_fixmap_nocache(idx, phys) \
  51                 __set_fixmap(idx, phys, PAGE_KERNEL_NOCACHE)
  52 /*
  53  * used by vmalloc.c.
  54  *
  55  * Leave one empty page between vmalloc'ed areas and
  56  * the start of the fixmap, and leave one page empty
  57  * at the top of mem..
  58  */
  59
  60 #define FIXADDR_TOP     (CONFIG_TOP_ADDR - 2 * PAGE_SIZE)
  61 #define FIXADDR_SIZE    (__end_of_fixed_addresses << PAGE_SHIFT)
  62 #define FIXADDR_START   (FIXADDR_TOP - FIXADDR_SIZE)
  63
  64 #define __fix_to_virt(x)        (FIXADDR_TOP - ((x) << PAGE_SHIFT))
  65 #define __virt_to_fix(x)      ((FIXADDR_TOP - ((x)&PAGE_MASK)) >> PAGE_SHIFT)
  66
  67 extern void __this_fixmap_does_not_exist(void);
  68
  69 /*
  70  * 'index to address' translation. If anyone tries to use the idx
  71  * directly without tranlation, we catch the bug with a NULL-deference
  72  * kernel oops. Illegal ranges of incoming indices are caught too.
  73  */
  74 static inline unsigned long fix_to_virt(const unsigned int idx)
  75 {
  76         /*
  77          * this branch gets completely eliminated after inlining,
  78          * except when someone tries to use fixaddr indices in an
  79          * illegal way. (such as mixing up address types or using
  80          * out-of-range indices).
  81          *
  82          * If it doesn't get removed, the linker will complain
  83          * loudly with a reasonably clear error message..
  84          */
  85         if (idx >= __end_of_fixed_addresses)
  86                 __this_fixmap_does_not_exist();
  87
  88         return __fix_to_virt(idx);
  89 }
  90
  91 static inline unsigned long virt_to_fix(const unsigned long vaddr)
  92 {
  93       BUG_ON(vaddr >= FIXADDR_TOP || vaddr < FIXADDR_START);
  94       return __virt_to_fix(vaddr);
  95 }
  96
  97 #endif