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 <asm/page.h>
18 #ifdef CONFIG_HIGHMEM
19 #include <linux/threads.h>
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 top of unused virtual memory (0xfd000000 - 1 page) 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 mechanism,
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 FIX_HOLE,
50 #ifdef CONFIG_HIGHMEM
51 FIX_KMAP_BEGIN,
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 IO pages at 0xfd000000 and
71 * the start of the fixmap.
72 */
73 #define FIXADDR_TOP (0xfcfff000UL)
74 #define FIXADDR_SIZE ((__end_of_fixed_addresses) << PAGE_SHIFT)
75 #define FIXADDR_START (FIXADDR_TOP - FIXADDR_SIZE)
76
77 #define __fix_to_virt(x) (FIXADDR_TOP - ((x) << PAGE_SHIFT))
78 #define __virt_to_fix(x) ((FIXADDR_TOP - ((x)&PAGE_MASK)) >> PAGE_SHIFT)
79
80 extern void __this_fixmap_does_not_exist(void);
81
82 /*
83 * 'index to address' translation. If anyone tries to use the idx
84 * directly without tranlation, we catch the bug with a NULL-deference
85 * kernel oops. Illegal ranges of incoming indices are caught too.
86 */
fix_to_virt(const unsigned int idx)87 static inline unsigned long fix_to_virt(const unsigned int idx)
88 {
89 /*
90 * this branch gets completely eliminated after inlining,
91 * except when someone tries to use fixaddr indices in an
92 * illegal way. (such as mixing up address types or using
93 * out-of-range indices).
94 *
95 * If it doesn't get removed, the linker will complain
96 * loudly with a reasonably clear error message..
97 */
98 if (idx >= __end_of_fixed_addresses)
99 __this_fixmap_does_not_exist();
100
101 return __fix_to_virt(idx);
102 }
103
virt_to_fix(const unsigned long vaddr)104 static inline unsigned long virt_to_fix(const unsigned long vaddr)
105 {
106 BUG_ON(vaddr >= FIXADDR_TOP || vaddr < FIXADDR_START);
107 return __virt_to_fix(vaddr);
108 }
109
110 #endif
111