arch/sh/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 <linux/threads.h>
  18 #include <asm/page.h>
  19 #ifdef CONFIG_HIGHMEM
  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 P3 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  */
  48 enum fixed_addresses {
  49         /*
  50          * The FIX_CMAP entries are used by kmap_coherent() to get virtual
  51          * addresses which are of a known color, and so their values are
  52          * important. __fix_to_virt(FIX_CMAP_END - n) must give an address
  53          * which is the same color as a page (n<<PAGE_SHIFT).
  54          */
  55 #define FIX_N_COLOURS 8
  56         FIX_CMAP_BEGIN,
  57         FIX_CMAP_END = FIX_CMAP_BEGIN + (FIX_N_COLOURS * NR_CPUS) - 1,
  58         FIX_UNCACHED,
  59 #ifdef CONFIG_HIGHMEM
  60         FIX_KMAP_BEGIN, /* reserved pte's for temporary kernel mappings */
  61         FIX_KMAP_END = FIX_KMAP_BEGIN+(KM_TYPE_NR*NR_CPUS)-1,
  62 #endif
  63         __end_of_fixed_addresses
  64 };
  65
  66 extern void __set_fixmap(enum fixed_addresses idx,
  67                          unsigned long phys, pgprot_t flags);
  68
  69 #define set_fixmap(idx, phys) \
  70                 __set_fixmap(idx, phys, PAGE_KERNEL)
  71 /*
  72  * Some hardware wants to get fixmapped without caching.
  73  */
  74 #define set_fixmap_nocache(idx, phys) \
  75                 __set_fixmap(idx, phys, PAGE_KERNEL_NOCACHE)
  76 /*
  77  * used by vmalloc.c.
  78  *
  79  * Leave one empty page between vmalloc'ed areas and
  80  * the start of the fixmap, and leave one page empty
  81  * at the top of mem..
  82  */
  83 #ifdef CONFIG_SUPERH32
  84 #define FIXADDR_TOP     (P4SEG - PAGE_SIZE)
  85 #else
  86 #define FIXADDR_TOP     (0xff000000 - PAGE_SIZE)
  87 #endif
  88 #define FIXADDR_SIZE    (__end_of_fixed_addresses << PAGE_SHIFT)
  89 #define FIXADDR_START   (FIXADDR_TOP - FIXADDR_SIZE)
  90
  91 #define __fix_to_virt(x)        (FIXADDR_TOP - ((x) << PAGE_SHIFT))
  92 #define __virt_to_fix(x)        ((FIXADDR_TOP - ((x)&PAGE_MASK)) >> 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 static 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 static inline unsigned long virt_to_fix(const unsigned long vaddr)
 119 {
 120         BUG_ON(vaddr >= FIXADDR_TOP || vaddr < FIXADDR_START);
 121         return __virt_to_fix(vaddr);
 122 }
 123 #endif