include/asm-mips/fixmap.h

   1 /*
   2  * fixmap.h: compile-time virtual memory allocation
   3  *
   4  * This file is subject to the terms and conditions of the GNU General Public
   5  * License.  See the file "COPYING" in the main directory of this archive
   6  * for more details.
   7  *
   8  * Copyright (C) 1998 Ingo Molnar
   9  *
  10  * Support of BIGMEM added by Gerhard Wichert, Siemens AG, July 1999
  11  */
  12
  13 #ifndef _ASM_FIXMAP_H
  14 #define _ASM_FIXMAP_H
  15
  16 #include <linux/config.h>
  17 #include <asm/page.h>
  18 #ifdef CONFIG_HIGHMEM
  19 #include <linux/threads.h>
  20 #include <asm/kmap_types.h>
  21 #endif
  22
  23 /*
  24  * Here we define all the compile-time 'special' virtual
  25  * addresses. The point is to have a constant address at
  26  * compile time, but to set the physical address only
  27  * in the boot process. We allocate these special  addresses
  28  * from the end of virtual memory (0xfffff000) backwards.
  29  * Also this lets us do fail-safe vmalloc(), we
  30  * can guarantee that these special addresses and
  31  * vmalloc()-ed addresses never overlap.
  32  *
  33  * these 'compile-time allocated' memory buffers are
  34  * fixed-size 4k pages. (or larger if used with an increment
  35  * highger than 1) use fixmap_set(idx,phys) to associate
  36  * physical memory with fixmap indices.
  37  *
  38  * TLB entries of such buffers will not be flushed across
  39  * task switches.
  40  */
  41
  42 /*
  43  * on UP currently we will have no trace of the fixmap mechanizm,
  44  * no page table allocations, etc. This might change in the
  45  * future, say framebuffers for the console driver(s) could be
  46  * fix-mapped?
  47  */
  48 enum fixed_addresses {
  49 #ifdef CONFIG_HIGHMEM
  50         FIX_KMAP_BEGIN, /* reserved pte's for temporary kernel mappings */
  51         FIX_KMAP_END = FIX_KMAP_BEGIN+(KM_TYPE_NR*NR_CPUS)-1,
  52 #endif
  53         __end_of_fixed_addresses
  54 };
  55
  56 extern void __set_fixmap (enum fixed_addresses idx,
  57                                         unsigned long phys, pgprot_t flags);
  58
  59 #define set_fixmap(idx, phys) \
  60                 __set_fixmap(idx, phys, PAGE_KERNEL)
  61 /*
  62  * Some hardware wants to get fixmapped without caching.
  63  */
  64 #define set_fixmap_nocache(idx, phys) \
  65                 __set_fixmap(idx, phys, PAGE_KERNEL_NOCACHE)
  66 /*
  67  * used by vmalloc.c.
  68  *
  69  * Leave one empty page between vmalloc'ed areas and
  70  * the start of the fixmap, and leave one page empty
  71  * at the top of mem..
  72  */
  73 #define FIXADDR_TOP     (0xffffe000UL)
  74 #define FIXADDR_SIZE    (__end_of_fixed_addresses << PAGE_SHIFT)
  75 #define FIXADDR_START   (FIXADDR_TOP - FIXADDR_SIZE)
  76
  77 #define __fix_to_virt(x)        (FIXADDR_TOP - ((x) << PAGE_SHIFT))
  78 #define __virt_to_fix(x)        ((FIXADDR_TOP - ((x)&PAGE_MASK)) >> PAGE_SHIFT)
  79
  80 extern void __this_fixmap_does_not_exist(void);
  81
  82 /*
  83  * 'index to address' translation. If anyone tries to use the idx
  84  * directly without tranlation, we catch the bug with a NULL-deference
  85  * kernel oops. Illegal ranges of incoming indices are caught too.
  86  */
  87 static inline unsigned long fix_to_virt(const unsigned int idx)
  88 {
  89         /*
  90          * this branch gets completely eliminated after inlining,
  91          * except when someone tries to use fixaddr indices in an
  92          * illegal way. (such as mixing up address types or using
  93          * out-of-range indices).
  94          *
  95          * If it doesn't get removed, the linker will complain
  96          * loudly with a reasonably clear error message..
  97          */
  98         if (idx >= __end_of_fixed_addresses)
  99                 __this_fixmap_does_not_exist();
 100
 101         return __fix_to_virt(idx);
 102 }
 103
 104 static inline unsigned long virt_to_fix(const unsigned long vaddr)
 105 {
 106         BUG_ON(vaddr >= FIXADDR_TOP || vaddr < FIXADDR_START);
 107         return __virt_to_fix(vaddr);
 108 }
 109
 110 /*
 111  * Called from pgtable_init()
 112  */
 113 extern void fixrange_init(unsigned long start, unsigned long end,
 114         pgd_t *pgd_base);
 115
 116
 117 #endif