include/asm-i386/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 <linux/kernel.h>
  18 #include <asm/apicdef.h>
  19 #include <asm/page.h>
  20 #ifdef CONFIG_HIGHMEM
  21 #include <linux/threads.h>
  22 #include <asm/kmap_types.h>
  23 #endif
  24
  25 /*
  26  * Here we define all the compile-time 'special' virtual
  27  * addresses. The point is to have a constant address at
  28  * compile time, but to set the physical address only
  29  * in the boot process. We allocate these special  addresses
  30  * from the end of virtual memory (0xfffff000) backwards.
  31  * Also this lets us do fail-safe vmalloc(), we
  32  * can guarantee that these special addresses and
  33  * vmalloc()-ed addresses never overlap.
  34  *
  35  * these 'compile-time allocated' memory buffers are
  36  * fixed-size 4k pages. (or larger if used with an increment
  37  * highger than 1) use fixmap_set(idx,phys) to associate
  38  * physical memory with fixmap indices.
  39  *
  40  * TLB entries of such buffers will not be flushed across
  41  * task switches.
  42  */
  43
  44 /*
  45  * on UP currently we will have no trace of the fixmap mechanizm,
  46  * no page table allocations, etc. This might change in the
  47  * future, say framebuffers for the console driver(s) could be
  48  * fix-mapped?
  49  */
  50 enum fixed_addresses {
  51 #ifdef CONFIG_X86_LOCAL_APIC
  52         FIX_APIC_BASE,  /* local (CPU) APIC) -- required for SMP or not */
  53 #endif
  54 #ifdef CONFIG_X86_IO_APIC
  55         FIX_IO_APIC_BASE_0,
  56         FIX_IO_APIC_BASE_END = FIX_IO_APIC_BASE_0 + MAX_IO_APICS-1,
  57 #endif
  58 #ifdef CONFIG_X86_VISWS_APIC
  59         FIX_CO_CPU,     /* Cobalt timer */
  60         FIX_CO_APIC,    /* Cobalt APIC Redirection Table */
  61         FIX_LI_PCIA,    /* Lithium PCI Bridge A */
  62         FIX_LI_PCIB,    /* Lithium PCI Bridge B */
  63 #endif
  64 #ifdef CONFIG_HIGHMEM
  65         FIX_KMAP_BEGIN, /* reserved pte's for temporary kernel mappings */
  66         FIX_KMAP_END = FIX_KMAP_BEGIN+(KM_TYPE_NR*NR_CPUS)-1,
  67 #endif
  68         __end_of_fixed_addresses
  69 };
  70
  71 extern void __set_fixmap (enum fixed_addresses idx,
  72                                         unsigned long phys, pgprot_t flags);
  73
  74 #define set_fixmap(idx, phys) \
  75                 __set_fixmap(idx, phys, PAGE_KERNEL)
  76 /*
  77  * Some hardware wants to get fixmapped without caching.
  78  */
  79 #define set_fixmap_nocache(idx, phys) \
  80                 __set_fixmap(idx, phys, PAGE_KERNEL_NOCACHE)
  81 /*
  82  * used by vmalloc.c.
  83  *
  84  * Leave one empty page between vmalloc'ed areas and
  85  * the start of the fixmap, and leave one page empty
  86  * at the top of mem..
  87  */
  88 #define FIXADDR_TOP     (0xffffe000UL)
  89 #define FIXADDR_SIZE    (__end_of_fixed_addresses << PAGE_SHIFT)
  90 #define FIXADDR_START   (FIXADDR_TOP - FIXADDR_SIZE)
  91
  92 #define __fix_to_virt(x)        (FIXADDR_TOP - ((x) << PAGE_SHIFT))
  93
  94 extern void __this_fixmap_does_not_exist(void);
  95
  96 /*
  97  * 'index to address' translation. If anyone tries to use the idx
  98  * directly without tranlation, we catch the bug with a NULL-deference
  99  * kernel oops. Illegal ranges of incoming indices are caught too.
 100  */
 101 extern inline unsigned long fix_to_virt(const unsigned int idx)
 102 {
 103         /*
 104          * this branch gets completely eliminated after inlining,
 105          * except when someone tries to use fixaddr indices in an
 106          * illegal way. (such as mixing up address types or using
 107          * out-of-range indices).
 108          *
 109          * If it doesn't get removed, the linker will complain
 110          * loudly with a reasonably clear error message..
 111          */
 112         if (idx >= __end_of_fixed_addresses)
 113                 __this_fixmap_does_not_exist();
 114
 115         return __fix_to_virt(idx);
 116 }
 117
 118 #endif