fixmap.h 4.1 KB

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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. #ifndef _ASM_FIXMAP_H
  13. #define _ASM_FIXMAP_H
  14. #include <linux/kernel.h>
  15. #include <linux/threads.h>
  16. #include <asm/page.h>
  17. #ifdef CONFIG_HIGHMEM
  18. #include <asm/kmap_types.h>
  19. #endif
  20. /*
  21. * Here we define all the compile-time 'special' virtual
  22. * addresses. The point is to have a constant address at
  23. * compile time, but to set the physical address only
  24. * in the boot process. We allocate these special addresses
  25. * from the end of P3 backwards.
  26. * Also this lets us do fail-safe vmalloc(), we
  27. * can guarantee that these special addresses and
  28. * vmalloc()-ed addresses never overlap.
  29. *
  30. * these 'compile-time allocated' memory buffers are
  31. * fixed-size 4k pages. (or larger if used with an increment
  32. * highger than 1) use fixmap_set(idx,phys) to associate
  33. * physical memory with fixmap indices.
  34. *
  35. * TLB entries of such buffers will not be flushed across
  36. * task switches.
  37. */
  38. /*
  39. * on UP currently we will have no trace of the fixmap mechanizm,
  40. * no page table allocations, etc. This might change in the
  41. * future, say framebuffers for the console driver(s) could be
  42. * fix-mapped?
  43. */
  44. enum fixed_addresses {
  45. /*
  46. * The FIX_CMAP entries are used by kmap_coherent() to get virtual
  47. * addresses which are of a known color, and so their values are
  48. * important. __fix_to_virt(FIX_CMAP_END - n) must give an address
  49. * which is the same color as a page (n<<PAGE_SHIFT).
  50. */
  51. #define FIX_N_COLOURS 8
  52. FIX_CMAP_BEGIN,
  53. FIX_CMAP_END = FIX_CMAP_BEGIN + (FIX_N_COLOURS * NR_CPUS) - 1,
  54. #ifdef CONFIG_HIGHMEM
  55. FIX_KMAP_BEGIN, /* reserved pte's for temporary kernel mappings */
  56. FIX_KMAP_END = FIX_KMAP_BEGIN + (KM_TYPE_NR * NR_CPUS) - 1,
  57. #endif
  58. #ifdef CONFIG_IOREMAP_FIXED
  59. /*
  60. * FIX_IOREMAP entries are useful for mapping physical address
  61. * space before ioremap() is useable, e.g. really early in boot
  62. * before kmalloc() is working.
  63. */
  64. #define FIX_N_IOREMAPS 32
  65. FIX_IOREMAP_BEGIN,
  66. FIX_IOREMAP_END = FIX_IOREMAP_BEGIN + FIX_N_IOREMAPS - 1,
  67. #endif
  68. __end_of_fixed_addresses
  69. };
  70. extern void __set_fixmap(enum fixed_addresses idx,
  71. unsigned long phys, pgprot_t flags);
  72. extern void __clear_fixmap(enum fixed_addresses idx, pgprot_t flags);
  73. #define set_fixmap(idx, phys) \
  74. __set_fixmap(idx, phys, PAGE_KERNEL)
  75. /*
  76. * Some hardware wants to get fixmapped without caching.
  77. */
  78. #define set_fixmap_nocache(idx, phys) \
  79. __set_fixmap(idx, phys, PAGE_KERNEL_NOCACHE)
  80. /*
  81. * used by vmalloc.c.
  82. *
  83. * Leave one empty page between vmalloc'ed areas and
  84. * the start of the fixmap, and leave one page empty
  85. * at the top of mem..
  86. */
  87. #ifdef CONFIG_SUPERH32
  88. #define FIXADDR_TOP (P4SEG - PAGE_SIZE)
  89. #else
  90. #define FIXADDR_TOP (0xff000000 - PAGE_SIZE)
  91. #endif
  92. #define FIXADDR_SIZE (__end_of_fixed_addresses << PAGE_SHIFT)
  93. #define FIXADDR_START (FIXADDR_TOP - FIXADDR_SIZE)
  94. #define __fix_to_virt(x) (FIXADDR_TOP - ((x) << PAGE_SHIFT))
  95. #define __virt_to_fix(x) ((FIXADDR_TOP - ((x)&PAGE_MASK)) >> PAGE_SHIFT)
  96. extern void __this_fixmap_does_not_exist(void);
  97. /*
  98. * 'index to address' translation. If anyone tries to use the idx
  99. * directly without tranlation, we catch the bug with a NULL-deference
  100. * kernel oops. Illegal ranges of incoming indices are caught too.
  101. */
  102. static inline unsigned long fix_to_virt(const unsigned int idx)
  103. {
  104. /*
  105. * this branch gets completely eliminated after inlining,
  106. * except when someone tries to use fixaddr indices in an
  107. * illegal way. (such as mixing up address types or using
  108. * out-of-range indices).
  109. *
  110. * If it doesn't get removed, the linker will complain
  111. * loudly with a reasonably clear error message..
  112. */
  113. if (idx >= __end_of_fixed_addresses)
  114. __this_fixmap_does_not_exist();
  115. return __fix_to_virt(idx);
  116. }
  117. static inline unsigned long virt_to_fix(const unsigned long vaddr)
  118. {
  119. BUG_ON(vaddr >= FIXADDR_TOP || vaddr < FIXADDR_START);
  120. return __virt_to_fix(vaddr);
  121. }
  122. #endif