linux/arch/mips/include/asm/fixmap.h
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   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#include <spaces.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 */
  48enum fixed_addresses {
  49#define FIX_N_COLOURS 8
  50        FIX_CMAP_BEGIN,
  51#ifdef CONFIG_MIPS_MT_SMTC
  52        FIX_CMAP_END = FIX_CMAP_BEGIN + (FIX_N_COLOURS * NR_CPUS * 2),
  53#else
  54        FIX_CMAP_END = FIX_CMAP_BEGIN + (FIX_N_COLOURS * 2),
  55#endif
  56#ifdef CONFIG_HIGHMEM
  57        /* reserved pte's for temporary kernel mappings */
  58        FIX_KMAP_BEGIN = FIX_CMAP_END + 1,
  59        FIX_KMAP_END = FIX_KMAP_BEGIN+(KM_TYPE_NR*NR_CPUS)-1,
  60#endif
  61        __end_of_fixed_addresses
  62};
  63
  64/*
  65 * used by vmalloc.c.
  66 *
  67 * Leave one empty page between vmalloc'ed areas and
  68 * the start of the fixmap, and leave one page empty
  69 * at the top of mem..
  70 */
  71#define FIXADDR_SIZE    (__end_of_fixed_addresses << PAGE_SHIFT)
  72#define FIXADDR_START   (FIXADDR_TOP - FIXADDR_SIZE)
  73
  74#define __fix_to_virt(x)        (FIXADDR_TOP - ((x) << PAGE_SHIFT))
  75#define __virt_to_fix(x)        ((FIXADDR_TOP - ((x)&PAGE_MASK)) >> PAGE_SHIFT)
  76
  77extern void __this_fixmap_does_not_exist(void);
  78
  79/*
  80 * 'index to address' translation. If anyone tries to use the idx
  81 * directly without tranlation, we catch the bug with a NULL-deference
  82 * kernel oops. Illegal ranges of incoming indices are caught too.
  83 */
  84static inline unsigned long fix_to_virt(const unsigned int idx)
  85{
  86        /*
  87         * this branch gets completely eliminated after inlining,
  88         * except when someone tries to use fixaddr indices in an
  89         * illegal way. (such as mixing up address types or using
  90         * out-of-range indices).
  91         *
  92         * If it doesn't get removed, the linker will complain
  93         * loudly with a reasonably clear error message..
  94         */
  95        if (idx >= __end_of_fixed_addresses)
  96                __this_fixmap_does_not_exist();
  97
  98        return __fix_to_virt(idx);
  99}
 100
 101static inline unsigned long virt_to_fix(const unsigned long vaddr)
 102{
 103        BUG_ON(vaddr >= FIXADDR_TOP || vaddr < FIXADDR_START);
 104        return __virt_to_fix(vaddr);
 105}
 106
 107#define kmap_get_fixmap_pte(vaddr)                                      \
 108        pte_offset_kernel(pmd_offset(pud_offset(pgd_offset_k(vaddr), (vaddr)), (vaddr)), (vaddr))
 109
 110/*
 111 * Called from pgtable_init()
 112 */
 113extern void fixrange_init(unsigned long start, unsigned long end,
 114        pgd_t *pgd_base);
 115
 116
 117#endif
 118