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
  11 #ifndef _ASM_FIXMAP_H
  12 #define _ASM_FIXMAP_H
  13
  14 #include <linux/config.h>
  15 #include <linux/kernel.h>
  16 #include <asm/page.h>
  17
  18 /*
  19  * Here we define all the compile-time 'special' virtual
  20  * addresses. The point is to have a constant address at
  21  * compile time, but to set the physical address only
  22  * in the boot process. We allocate these special  addresses
  23  * from the end of virtual memory (0xfffff000) backwards.
  24  * Also this lets us do fail-safe vmalloc(), we
  25  * can guarantee that these special addresses and
  26  * vmalloc()-ed addresses never overlap.
  27  *
  28  * these 'compile-time allocated' memory buffers are
  29  * fixed-size 4k pages. (or larger if used with an increment
  30  * bigger than 1) use fixmap_set(idx,phys) to associate
  31  * physical memory with fixmap indices.
  32  *
  33  * TLB entries of such buffers will not be flushed across
  34  * task switches.
  35  */
  36
  37 /*
  38  * on UP currently we will have no trace of the fixmap mechanizm,
  39  * no page table allocations, etc. This might change in the
  40  * future, say framebuffers for the console driver(s) could be
  41  * fix-mapped?
  42  */
  43 enum fixed_addresses {
  44 #ifdef CONFIG_X86_LOCAL_APIC
  45         FIX_APIC_BASE,  /* local (CPU) APIC) -- required for SMP or not */
  46 #endif
  47 #ifdef CONFIG_X86_IO_APIC
  48         FIX_IO_APIC_BASE,
  49 #endif
  50 #ifdef CONFIG_X86_VISWS_APIC
  51         FIX_CO_CPU,     /* Cobalt timer */
  52         FIX_CO_APIC,    /* Cobalt APIC Redirection Table */
  53         FIX_LI_PCIA,    /* Lithium PCI Bridge A */
  54         FIX_LI_PCIB,    /* Lithium PCI Bridge B */
  55 #endif
  56         __end_of_fixed_addresses
  57 };
  58
  59 extern void set_fixmap (enum fixed_addresses idx, unsigned long phys);
  60
  61 /*
  62  * used by vmalloc.c.
  63  *
  64  * Leave one empty page between vmalloc'ed areas and
  65  * the start of the fixmap, and leave one page empty
  66  * at the top of mem..
  67  */
  68 #define FIXADDR_TOP     (0xffffe000UL)
  69 #define FIXADDR_SIZE    (__end_of_fixed_addresses << PAGE_SHIFT)
  70 #define FIXADDR_START   (FIXADDR_TOP - FIXADDR_SIZE)
  71
  72 #define __fix_to_virt(x)        (FIXADDR_TOP - ((x) << PAGE_SHIFT))
  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 extern 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 #endif