include/asm-um/fixmap.h

   1 #ifndef __UM_FIXMAP_H
   2 #define __UM_FIXMAP_H
   3
   4 #include <linux/config.h>
   5 #include <asm/kmap_types.h>
   6
   7 /*
   8  * Here we define all the compile-time 'special' virtual
   9  * addresses. The point is to have a constant address at
  10  * compile time, but to set the physical address only
  11  * in the boot process. We allocate these special  addresses
  12  * from the end of virtual memory (0xfffff000) backwards.
  13  * Also this lets us do fail-safe vmalloc(), we
  14  * can guarantee that these special addresses and
  15  * vmalloc()-ed addresses never overlap.
  16  *
  17  * these 'compile-time allocated' memory buffers are
  18  * fixed-size 4k pages. (or larger if used with an increment
  19  * highger than 1) use fixmap_set(idx,phys) to associate
  20  * physical memory with fixmap indices.
  21  *
  22  * TLB entries of such buffers will not be flushed across
  23  * task switches.
  24  */
  25
  26 /*
  27  * on UP currently we will have no trace of the fixmap mechanizm,
  28  * no page table allocations, etc. This might change in the
  29  * future, say framebuffers for the console driver(s) could be
  30  * fix-mapped?
  31  */
  32 enum fixed_addresses {
  33 #ifdef CONFIG_HIGHMEM
  34         FIX_KMAP_BEGIN, /* reserved pte's for temporary kernel mappings */
  35         FIX_KMAP_END = FIX_KMAP_BEGIN+(KM_TYPE_NR*NR_CPUS)-1,
  36 #endif
  37         FIX_VSYSCALL,
  38         __end_of_fixed_addresses
  39 };
  40
  41 extern void __set_fixmap (enum fixed_addresses idx,
  42                           unsigned long phys, pgprot_t flags);
  43
  44 #define set_fixmap(idx, phys) \
  45                 __set_fixmap(idx, phys, PAGE_KERNEL)
  46 /*
  47  * Some hardware wants to get fixmapped without caching.
  48  */
  49 #define set_fixmap_nocache(idx, phys) \
  50                 __set_fixmap(idx, phys, PAGE_KERNEL_NOCACHE)
  51 /*
  52  * used by vmalloc.c.
  53  *
  54  * Leave one empty page between vmalloc'ed areas and
  55  * the start of the fixmap, and leave one page empty
  56  * at the top of mem..
  57  */
  58 extern unsigned long get_kmem_end(void);
  59
  60 #define FIXADDR_TOP     (get_kmem_end() - 0x2000)
  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 /*
  68  * This is the range that is readable by user mode, and things
  69  * acting like user mode such as get_user_pages.
  70  */
  71 #define FIXADDR_USER_START      (__fix_to_virt(FIX_VSYSCALL))
  72 #define FIXADDR_USER_END        (FIXADDR_USER_START + PAGE_SIZE)
  73
  74 extern void __this_fixmap_does_not_exist(void);
  75
  76 /*
  77  * 'index to address' translation. If anyone tries to use the idx
  78  * directly without tranlation, we catch the bug with a NULL-deference
  79  * kernel oops. Illegal ranges of incoming indices are caught too.
  80  */
  81 static inline unsigned long fix_to_virt(const unsigned int idx)
  82 {
  83         /*
  84          * this branch gets completely eliminated after inlining,
  85          * except when someone tries to use fixaddr indices in an
  86          * illegal way. (such as mixing up address types or using
  87          * out-of-range indices).
  88          *
  89          * If it doesn't get removed, the linker will complain
  90          * loudly with a reasonably clear error message..
  91          */
  92         if (idx >= __end_of_fixed_addresses)
  93                 __this_fixmap_does_not_exist();
  94
  95         return __fix_to_virt(idx);
  96 }
  97
  98 static inline unsigned long virt_to_fix(const unsigned long vaddr)
  99 {
 100       BUG_ON(vaddr >= FIXADDR_TOP || vaddr < FIXADDR_START);
 101       return __virt_to_fix(vaddr);
 102 }
 103
 104 #endif