projects / deliverable / linux.git / blame
| Commit | Line | Data |
|---|---|---|
| 3a94707d KC |
1 | /* |
| 2 | * This code is used on x86_64 to create page table identity mappings on | |
| 3 | * demand by building up a new set of page tables (or appending to the | |
| 4 | * existing ones), and then switching over to them when ready. | |
| 11fdf97a KC |
5 | * |
| 6 | * Copyright (C) 2015-2016 Yinghai Lu | |
| 7 | * Copyright (C) 2016 Kees Cook | |
| 3a94707d KC |
8 | */ |
| 9 | ||
| 10 | /* | |
| 11 | * Since we're dealing with identity mappings, physical and virtual | |
| 12 | * addresses are the same, so override these defines which are ultimately | |
| 13 | * used by the headers in misc.h. | |
| 14 | */ | |
| 15 | #define __pa(x) ((unsigned long)(x)) | |
| 16 | #define __va(x) ((void *)((unsigned long)(x))) | |
| 17 | ||
| 18 | #include "misc.h" | |
| 19 | ||
| 20 | /* These actually do the work of building the kernel identity maps. */ | |
| 21 | #include <asm/init.h> | |
| 22 | #include <asm/pgtable.h> | |
| 021182e5 TG |
23 | /* Use the static base for this part of the boot process */ |
| 24 | #undef __PAGE_OFFSET | |
| 25 | #define __PAGE_OFFSET __PAGE_OFFSET_BASE | |
| 3a94707d KC |
26 | #include "../../mm/ident_map.c" |
| 27 | ||
| 28 | /* Used by pgtable.h asm code to force instruction serialization. */ | |
| 29 | unsigned long __force_order; | |
| 30 | ||
| 31 | /* Used to track our page table allocation area. */ | |
| 32 | struct alloc_pgt_data { | |
| 33 | unsigned char *pgt_buf; | |
| 34 | unsigned long pgt_buf_size; | |
| 35 | unsigned long pgt_buf_offset; | |
| 36 | }; | |
| 37 | ||
| 38 | /* | |
| 39 | * Allocates space for a page table entry, using struct alloc_pgt_data | |
| 40 | * above. Besides the local callers, this is used as the allocation | |
| 41 | * callback in mapping_info below. | |
| 42 | */ | |
| 43 | static void *alloc_pgt_page(void *context) | |
| 44 | { | |
| 45 | struct alloc_pgt_data *pages = (struct alloc_pgt_data *)context; | |
| 46 | unsigned char *entry; | |
| 47 | ||
| 48 | /* Validate there is space available for a new page. */ | |
| 49 | if (pages->pgt_buf_offset >= pages->pgt_buf_size) { | |
| 50 | debug_putstr("out of pgt_buf in " __FILE__ "!?\n"); | |
| 51 | debug_putaddr(pages->pgt_buf_offset); | |
| 52 | debug_putaddr(pages->pgt_buf_size); | |
| 53 | return NULL; | |
| 54 | } | |
| 55 | ||
| 56 | entry = pages->pgt_buf + pages->pgt_buf_offset; | |
| 57 | pages->pgt_buf_offset += PAGE_SIZE; | |
| 58 | ||
| 59 | return entry; | |
| 60 | } | |
| 61 | ||
| 62 | /* Used to track our allocated page tables. */ | |
| 63 | static struct alloc_pgt_data pgt_data; | |
| 64 | ||
| 65 | /* The top level page table entry pointer. */ | |
| 66 | static unsigned long level4p; | |
| 67 | ||
| 11fdf97a KC |
68 | /* |
| 69 | * Mapping information structure passed to kernel_ident_mapping_init(). | |
| 70 | * Due to relocation, pointers must be assigned at run time not build time. | |
| 71 | */ | |
| 72 | static struct x86_mapping_info mapping_info = { | |
| 73 | .pmd_flag = __PAGE_KERNEL_LARGE_EXEC, | |
| 74 | }; | |
| 75 | ||
| 3a94707d | 76 | /* Locates and clears a region for a new top level page table. */ |
| 11fdf97a | 77 | void initialize_identity_maps(void) |
| 3a94707d | 78 | { |
| 11fdf97a KC |
79 | /* Init mapping_info with run-time function/buffer pointers. */ |
| 80 | mapping_info.alloc_pgt_page = alloc_pgt_page; | |
| 81 | mapping_info.context = &pgt_data; | |
| 82 | ||
| 3a94707d KC |
83 | /* |
| 84 | * It should be impossible for this not to already be true, | |
| 85 | * but since calling this a second time would rewind the other | |
| 86 | * counters, let's just make sure this is reset too. | |
| 87 | */ | |
| 88 | pgt_data.pgt_buf_offset = 0; | |
| 89 | ||
| 90 | /* | |
| 91 | * If we came here via startup_32(), cr3 will be _pgtable already | |
| 92 | * and we must append to the existing area instead of entirely | |
| 93 | * overwriting it. | |
| 94 | */ | |
| 95 | level4p = read_cr3(); | |
| 96 | if (level4p == (unsigned long)_pgtable) { | |
| 97 | debug_putstr("booted via startup_32()\n"); | |
| 98 | pgt_data.pgt_buf = _pgtable + BOOT_INIT_PGT_SIZE; | |
| 99 | pgt_data.pgt_buf_size = BOOT_PGT_SIZE - BOOT_INIT_PGT_SIZE; | |
| 100 | memset(pgt_data.pgt_buf, 0, pgt_data.pgt_buf_size); | |
| 101 | } else { | |
| 102 | debug_putstr("booted via startup_64()\n"); | |
| 103 | pgt_data.pgt_buf = _pgtable; | |
| 104 | pgt_data.pgt_buf_size = BOOT_PGT_SIZE; | |
| 105 | memset(pgt_data.pgt_buf, 0, pgt_data.pgt_buf_size); | |
| 106 | level4p = (unsigned long)alloc_pgt_page(&pgt_data); | |
| 107 | } | |
| 108 | } | |
| 109 | ||
| 3a94707d KC |
110 | /* |
| 111 | * Adds the specified range to what will become the new identity mappings. | |
| 112 | * Once all ranges have been added, the new mapping is activated by calling | |
| 113 | * finalize_identity_maps() below. | |
| 114 | */ | |
| 115 | void add_identity_map(unsigned long start, unsigned long size) | |
| 116 | { | |
| 117 | unsigned long end = start + size; | |
| 118 | ||
| 3a94707d KC |
119 | /* Align boundary to 2M. */ |
| 120 | start = round_down(start, PMD_SIZE); | |
| 121 | end = round_up(end, PMD_SIZE); | |
| 122 | if (start >= end) | |
| 123 | return; | |
| 124 | ||
| 125 | /* Build the mapping. */ | |
| 126 | kernel_ident_mapping_init(&mapping_info, (pgd_t *)level4p, | |
| 127 | start, end); | |
| 128 | } | |
| 129 | ||
| 130 | /* | |
| 131 | * This switches the page tables to the new level4 that has been built | |
| 132 | * via calls to add_identity_map() above. If booted via startup_32(), | |
| 133 | * this is effectively a no-op. | |
| 134 | */ | |
| 135 | void finalize_identity_maps(void) | |
| 136 | { | |
| 137 | write_cr3(level4p); | |
| 138 | } |