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 */ 48enum 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 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 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 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 104static 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