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