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