LXR linux/arch/sparc/include/asm/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/kernel.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 top of unused virtual memory (0xfd000000 - 1 page) 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 mechanism,
  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 */
  48enum fixed_addresses {
  49        FIX_HOLE,
  50#ifdef CONFIG_HIGHMEM
  51        FIX_KMAP_BEGIN,
  52        FIX_KMAP_END = FIX_KMAP_BEGIN+(KM_TYPE_NR*NR_CPUS)-1,
  53#endif
  54        __end_of_fixed_addresses
  55};
  56
  57extern void __set_fixmap (enum fixed_addresses idx,
  58                                        unsigned long phys, pgprot_t flags);
  59
  60#define set_fixmap(idx, phys) \
  61                __set_fixmap(idx, phys, PAGE_KERNEL)
  62/*
  63 * Some hardware wants to get fixmapped without caching.
  64 */
  65#define set_fixmap_nocache(idx, phys) \
  66                __set_fixmap(idx, phys, PAGE_KERNEL_NOCACHE)
  67/*
  68 * used by vmalloc.c.
  69 *
  70 * Leave one empty page between IO pages at 0xfd000000 and
  71 * the start of the fixmap.
  72 */
  73#define FIXADDR_TOP     (0xfcfff000UL)
  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
  80extern 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 */
  87static 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
 104static 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#endif
 111