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
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
64 #ifdef CONFIG_IOREMAP_FIXED
65 /*
66 * FIX_IOREMAP entries are useful for mapping physical address
67 * space before ioremap() is useable, e.g. really early in boot
68 * before kmalloc() is working.
69 */
70 #define FIX_N_IOREMAPS 32
71 FIX_IOREMAP_BEGIN,
72 FIX_IOREMAP_END = FIX_IOREMAP_BEGIN + FIX_N_IOREMAPS - 1,
73 #endif
74
75 __end_of_fixed_addresses
76 };
77
78 extern void __set_fixmap(enum fixed_addresses idx,
79 unsigned long phys, pgprot_t flags);
80 extern void __clear_fixmap(enum fixed_addresses idx, pgprot_t flags);
81
82 #define set_fixmap(idx, phys) \
83 __set_fixmap(idx, phys, PAGE_KERNEL)
84 /*
85 * Some hardware wants to get fixmapped without caching.
86 */
87 #define set_fixmap_nocache(idx, phys) \
88 __set_fixmap(idx, phys, PAGE_KERNEL_NOCACHE)
89 /*
90 * used by vmalloc.c.
91 *
92 * Leave one empty page between vmalloc'ed areas and
93 * the start of the fixmap, and leave one page empty
94 * at the top of mem..
95 */
96 #ifdef CONFIG_SUPERH32
97 #define FIXADDR_TOP (P4SEG - PAGE_SIZE)
98 #else
99 #define FIXADDR_TOP ((unsigned long)(-PAGE_SIZE))
100 #endif
101 #define FIXADDR_SIZE (__end_of_fixed_addresses << PAGE_SHIFT)
102 #define FIXADDR_START (FIXADDR_TOP - FIXADDR_SIZE)
103
104 #define __fix_to_virt(x) (FIXADDR_TOP - ((x) << PAGE_SHIFT))
105 #define __virt_to_fix(x) ((FIXADDR_TOP - ((x)&PAGE_MASK)) >> PAGE_SHIFT)
106
107 extern void __this_fixmap_does_not_exist(void);
108
109 /*
110 * 'index to address' translation. If anyone tries to use the idx
111 * directly without tranlation, we catch the bug with a NULL-deference
112 * kernel oops. Illegal ranges of incoming indices are caught too.
113 */
fix_to_virt(const unsigned int idx)114 static inline unsigned long fix_to_virt(const unsigned int idx)
115 {
116 /*
117 * this branch gets completely eliminated after inlining,
118 * except when someone tries to use fixaddr indices in an
119 * illegal way. (such as mixing up address types or using
120 * out-of-range indices).
121 *
122 * If it doesn't get removed, the linker will complain
123 * loudly with a reasonably clear error message..
124 */
125 if (idx >= __end_of_fixed_addresses)
126 __this_fixmap_does_not_exist();
127
128 return __fix_to_virt(idx);
129 }
130
virt_to_fix(const unsigned long vaddr)131 static inline unsigned long virt_to_fix(const unsigned long vaddr)
132 {
133 BUG_ON(vaddr >= FIXADDR_TOP || vaddr < FIXADDR_START);
134 return __virt_to_fix(vaddr);
135 }
136 #endif
137