Linux Kernel  3.7.1
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fixmap.h
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1 #ifndef __UM_FIXMAP_H
2 #define __UM_FIXMAP_H
3 
4 #include <asm/processor.h>
5 #include <asm/kmap_types.h>
6 #include <asm/archparam.h>
7 #include <asm/page.h>
8 #include <linux/threads.h>
9 
10 /*
11  * Here we define all the compile-time 'special' virtual
12  * addresses. The point is to have a constant address at
13  * compile time, but to set the physical address only
14  * in the boot process. We allocate these special addresses
15  * from the end of virtual memory (0xfffff000) backwards.
16  * Also this lets us do fail-safe vmalloc(), we
17  * can guarantee that these special addresses and
18  * vmalloc()-ed addresses never overlap.
19  *
20  * these 'compile-time allocated' memory buffers are
21  * fixed-size 4k pages. (or larger if used with an increment
22  * highger than 1) use fixmap_set(idx,phys) to associate
23  * physical memory with fixmap indices.
24  *
25  * TLB entries of such buffers will not be flushed across
26  * task switches.
27  */
28 
29 /*
30  * on UP currently we will have no trace of the fixmap mechanizm,
31  * no page table allocations, etc. This might change in the
32  * future, say framebuffers for the console driver(s) could be
33  * fix-mapped?
34  */
36 #ifdef CONFIG_HIGHMEM
37  FIX_KMAP_BEGIN, /* reserved pte's for temporary kernel mappings */
39 #endif
41 };
42 
43 extern void __set_fixmap (enum fixed_addresses idx,
44  unsigned long phys, pgprot_t flags);
45 
46 #define set_fixmap(idx, phys) \
47  __set_fixmap(idx, phys, PAGE_KERNEL)
48 /*
49  * Some hardware wants to get fixmapped without caching.
50  */
51 #define set_fixmap_nocache(idx, phys) \
52  __set_fixmap(idx, phys, PAGE_KERNEL_NOCACHE)
53 /*
54  * used by vmalloc.c.
55  *
56  * Leave one empty page between vmalloc'ed areas and
57  * the start of the fixmap, and leave one page empty
58  * at the top of mem..
59  */
60 
61 #define FIXADDR_TOP (TASK_SIZE - 2 * PAGE_SIZE)
62 #define FIXADDR_SIZE (__end_of_fixed_addresses << PAGE_SHIFT)
63 #define FIXADDR_START (FIXADDR_TOP - FIXADDR_SIZE)
64 
65 #define __fix_to_virt(x) (FIXADDR_TOP - ((x) << PAGE_SHIFT))
66 #define __virt_to_fix(x) ((FIXADDR_TOP - ((x)&PAGE_MASK)) >> PAGE_SHIFT)
67 
68 extern void __this_fixmap_does_not_exist(void);
69 
70 /*
71  * 'index to address' translation. If anyone tries to use the idx
72  * directly without tranlation, we catch the bug with a NULL-deference
73  * kernel oops. Illegal ranges of incoming indices are caught too.
74  */
75 static inline unsigned long fix_to_virt(const unsigned int idx)
76 {
77  /*
78  * this branch gets completely eliminated after inlining,
79  * except when someone tries to use fixaddr indices in an
80  * illegal way. (such as mixing up address types or using
81  * out-of-range indices).
82  *
83  * If it doesn't get removed, the linker will complain
84  * loudly with a reasonably clear error message..
85  */
86  if (idx >= __end_of_fixed_addresses)
88 
89  return __fix_to_virt(idx);
90 }
91 
92 static inline unsigned long virt_to_fix(const unsigned long vaddr)
93 {
94  BUG_ON(vaddr >= FIXADDR_TOP || vaddr < FIXADDR_START);
95  return __virt_to_fix(vaddr);
96 }
97 
98 #endif