include/asm-sh/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/page.h>
  19 #ifdef CONFIG_HIGHMEM
  20 #include <linux/threads.h>
  21 #include <asm/kmap_types.h>
  22 #endif
  23
  24 /*
  25  * Here we define all the compile-time 'special' virtual
  26  * addresses. The point is to have a constant address at
  27  * compile time, but to set the physical address only
  28  * in the boot process. We allocate these special  addresses
  29  * from the end of virtual memory (0xfffff000) backwards.
  30  * Also this lets us do fail-safe vmalloc(), we
  31  * can guarantee that these special addresses and
  32  * vmalloc()-ed addresses never overlap.
  33  *
  34  * these 'compile-time allocated' memory buffers are
  35  * fixed-size 4k pages. (or larger if used with an increment
  36  * highger than 1) use fixmap_set(idx,phys) to associate
  37  * physical memory with fixmap indices.
  38  *
  39  * TLB entries of such buffers will not be flushed across
  40  * task switches.
  41  */
  42
  43 /*
  44  * on UP currently we will have no trace of the fixmap mechanizm,
  45  * no page table allocations, etc. This might change in the
  46  * future, say framebuffers for the console driver(s) could be
  47  * fix-mapped?
  48  */
  49 enum fixed_addresses {
  50 #ifdef CONFIG_HIGHMEM
  51         FIX_KMAP_BEGIN, /* reserved pte's for temporary kernel mappings */
  52         FIX_KMAP_END = FIX_KMAP_BEGIN+(KM_TYPE_NR*NR_CPUS)-1,
  53 #endif
  54         __end_of_fixed_addresses
  55 };
  56
  57 extern 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 vmalloc'ed areas and
  71  * the start of the fixmap, and leave one page empty
  72  * at the top of mem..
  73  */
  74 #define FIXADDR_TOP     (P4SEG - PAGE_SIZE)
  75 #define FIXADDR_SIZE    (__end_of_fixed_addresses << PAGE_SHIFT)
  76 #define FIXADDR_START   (FIXADDR_TOP - FIXADDR_SIZE)
  77
  78 #define __fix_to_virt(x)        (FIXADDR_TOP - ((x) << PAGE_SHIFT))
  79 #define __virt_to_fix(x)        ((FIXADDR_TOP - ((x)&PAGE_MASK)) >> PAGE_SHIFT)
  80
  81 extern void __this_fixmap_does_not_exist(void);
  82
  83 /*
  84  * 'index to address' translation. If anyone tries to use the idx
  85  * directly without tranlation, we catch the bug with a NULL-deference
  86  * kernel oops. Illegal ranges of incoming indices are caught too.
  87  */
  88 static inline unsigned long fix_to_virt(const unsigned int idx)
  89 {
  90         /*
  91          * this branch gets completely eliminated after inlining,
  92          * except when someone tries to use fixaddr indices in an
  93          * illegal way. (such as mixing up address types or using
  94          * out-of-range indices).
  95          *
  96          * If it doesn't get removed, the linker will complain
  97          * loudly with a reasonably clear error message..
  98          */
  99         if (idx >= __end_of_fixed_addresses)
 100                 __this_fixmap_does_not_exist();
 101
 102         return __fix_to_virt(idx);
 103 }
 104
 105 static inline unsigned long virt_to_fix(const unsigned long vaddr)
 106 {
 107         BUG_ON(vaddr >= FIXADDR_TOP || vaddr < FIXADDR_START);
 108         return __virt_to_fix(vaddr);
 109 }
 110
 111 #endif