LXR linux/include/asm-um/fixmap.h

   1#ifndef __UM_FIXMAP_H
   2#define __UM_FIXMAP_H
   3
   4#include <asm/kmap_types.h>
   5#include <asm/archparam.h>
   6#include <asm/elf.h>
   7
   8/*
   9 * Here we define all the compile-time 'special' virtual
  10 * addresses. The point is to have a constant address at
  11 * compile time, but to set the physical address only
  12 * in the boot process. We allocate these special  addresses
  13 * from the end of virtual memory (0xfffff000) backwards.
  14 * Also this lets us do fail-safe vmalloc(), we
  15 * can guarantee that these special addresses and
  16 * vmalloc()-ed addresses never overlap.
  17 *
  18 * these 'compile-time allocated' memory buffers are
  19 * fixed-size 4k pages. (or larger if used with an increment
  20 * highger than 1) use fixmap_set(idx,phys) to associate
  21 * physical memory with fixmap indices.
  22 *
  23 * TLB entries of such buffers will not be flushed across
  24 * task switches.
  25 */
  26
  27/*
  28 * on UP currently we will have no trace of the fixmap mechanizm,
  29 * no page table allocations, etc. This might change in the
  30 * future, say framebuffers for the console driver(s) could be
  31 * fix-mapped?
  32 */
  33enum fixed_addresses {
  34#ifdef CONFIG_HIGHMEM
  35        FIX_KMAP_BEGIN, /* reserved pte's for temporary kernel mappings */
  36        FIX_KMAP_END = FIX_KMAP_BEGIN+(KM_TYPE_NR*NR_CPUS)-1,
  37#endif
  38        __end_of_fixed_addresses
  39};
  40
  41extern 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 */
  58extern 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
  67extern 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 */
  74static 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
  91static 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
  98