include/asm-um/fixmap.h

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