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 */
49enum 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
57extern 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	(0xffffe000UL)
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
80extern 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 */
87static 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
104#endif
105