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