1 /* 2 * This file contains kasan initialization code for ARM64. 3 * 4 * Copyright (c) 2015 Samsung Electronics Co., Ltd. 5 * Author: Andrey Ryabinin <ryabinin.a.a@gmail.com> 6 * 7 * This program is free software; you can redistribute it and/or modify 8 * it under the terms of the GNU General Public License version 2 as 9 * published by the Free Software Foundation. 10 * 11 */ 12 13 #define pr_fmt(fmt) "kasan: " fmt 14 #include <linux/kasan.h> 15 #include <linux/kernel.h> 16 #include <linux/memblock.h> 17 #include <linux/start_kernel.h> 18 #include <linux/mm.h> 19 20 #include <asm/mmu_context.h> 21 #include <asm/kernel-pgtable.h> 22 #include <asm/page.h> 23 #include <asm/pgalloc.h> 24 #include <asm/pgtable.h> 25 #include <asm/sections.h> 26 #include <asm/tlbflush.h> 27 28 static pgd_t tmp_pg_dir[PTRS_PER_PGD] __initdata __aligned(PGD_SIZE); 29 30 /* 31 * The p*d_populate functions call virt_to_phys implicitly so they can't be used 32 * directly on kernel symbols (bm_p*d). All the early functions are called too 33 * early to use lm_alias so __p*d_populate functions must be used to populate 34 * with the physical address from __pa_symbol. 35 */ 36 37 static void __init kasan_early_pte_populate(pmd_t *pmd, unsigned long addr, 38 unsigned long end) 39 { 40 pte_t *pte; 41 unsigned long next; 42 43 if (pmd_none(*pmd)) 44 __pmd_populate(pmd, __pa_symbol(kasan_zero_pte), PMD_TYPE_TABLE); 45 46 pte = pte_offset_kimg(pmd, addr); 47 do { 48 next = addr + PAGE_SIZE; 49 set_pte(pte, pfn_pte(sym_to_pfn(kasan_zero_page), 50 PAGE_KERNEL)); 51 } while (pte++, addr = next, addr != end && pte_none(*pte)); 52 } 53 54 static void __init kasan_early_pmd_populate(pud_t *pud, 55 unsigned long addr, 56 unsigned long end) 57 { 58 pmd_t *pmd; 59 unsigned long next; 60 61 if (pud_none(*pud)) 62 __pud_populate(pud, __pa_symbol(kasan_zero_pmd), PMD_TYPE_TABLE); 63 64 pmd = pmd_offset_kimg(pud, addr); 65 do { 66 next = pmd_addr_end(addr, end); 67 kasan_early_pte_populate(pmd, addr, next); 68 } while (pmd++, addr = next, addr != end && pmd_none(*pmd)); 69 } 70 71 static void __init kasan_early_pud_populate(pgd_t *pgd, 72 unsigned long addr, 73 unsigned long end) 74 { 75 pud_t *pud; 76 unsigned long next; 77 78 if (pgd_none(*pgd)) 79 __pgd_populate(pgd, __pa_symbol(kasan_zero_pud), PUD_TYPE_TABLE); 80 81 pud = pud_offset_kimg(pgd, addr); 82 do { 83 next = pud_addr_end(addr, end); 84 kasan_early_pmd_populate(pud, addr, next); 85 } while (pud++, addr = next, addr != end && pud_none(*pud)); 86 } 87 88 static void __init kasan_map_early_shadow(void) 89 { 90 unsigned long addr = KASAN_SHADOW_START; 91 unsigned long end = KASAN_SHADOW_END; 92 unsigned long next; 93 pgd_t *pgd; 94 95 pgd = pgd_offset_k(addr); 96 do { 97 next = pgd_addr_end(addr, end); 98 kasan_early_pud_populate(pgd, addr, next); 99 } while (pgd++, addr = next, addr != end); 100 } 101 102 asmlinkage void __init kasan_early_init(void) 103 { 104 BUILD_BUG_ON(KASAN_SHADOW_OFFSET != KASAN_SHADOW_END - (1UL << 61)); 105 BUILD_BUG_ON(!IS_ALIGNED(KASAN_SHADOW_START, PGDIR_SIZE)); 106 BUILD_BUG_ON(!IS_ALIGNED(KASAN_SHADOW_END, PGDIR_SIZE)); 107 kasan_map_early_shadow(); 108 } 109 110 /* 111 * Copy the current shadow region into a new pgdir. 112 */ 113 void __init kasan_copy_shadow(pgd_t *pgdir) 114 { 115 pgd_t *pgd, *pgd_new, *pgd_end; 116 117 pgd = pgd_offset_k(KASAN_SHADOW_START); 118 pgd_end = pgd_offset_k(KASAN_SHADOW_END); 119 pgd_new = pgd_offset_raw(pgdir, KASAN_SHADOW_START); 120 do { 121 set_pgd(pgd_new, *pgd); 122 } while (pgd++, pgd_new++, pgd != pgd_end); 123 } 124 125 static void __init clear_pgds(unsigned long start, 126 unsigned long end) 127 { 128 /* 129 * Remove references to kasan page tables from 130 * swapper_pg_dir. pgd_clear() can't be used 131 * here because it's nop on 2,3-level pagetable setups 132 */ 133 for (; start < end; start += PGDIR_SIZE) 134 set_pgd(pgd_offset_k(start), __pgd(0)); 135 } 136 137 void __init kasan_init(void) 138 { 139 u64 kimg_shadow_start, kimg_shadow_end; 140 u64 mod_shadow_start, mod_shadow_end; 141 struct memblock_region *reg; 142 int i; 143 144 kimg_shadow_start = (u64)kasan_mem_to_shadow(_text); 145 kimg_shadow_end = (u64)kasan_mem_to_shadow(_end); 146 147 mod_shadow_start = (u64)kasan_mem_to_shadow((void *)MODULES_VADDR); 148 mod_shadow_end = (u64)kasan_mem_to_shadow((void *)MODULES_END); 149 150 /* 151 * We are going to perform proper setup of shadow memory. 152 * At first we should unmap early shadow (clear_pgds() call bellow). 153 * However, instrumented code couldn't execute without shadow memory. 154 * tmp_pg_dir used to keep early shadow mapped until full shadow 155 * setup will be finished. 156 */ 157 memcpy(tmp_pg_dir, swapper_pg_dir, sizeof(tmp_pg_dir)); 158 dsb(ishst); 159 cpu_replace_ttbr1(lm_alias(tmp_pg_dir)); 160 161 clear_pgds(KASAN_SHADOW_START, KASAN_SHADOW_END); 162 163 vmemmap_populate(kimg_shadow_start, kimg_shadow_end, 164 pfn_to_nid(virt_to_pfn(_text))); 165 166 /* 167 * vmemmap_populate() has populated the shadow region that covers the 168 * kernel image with SWAPPER_BLOCK_SIZE mappings, so we have to round 169 * the start and end addresses to SWAPPER_BLOCK_SIZE as well, to prevent 170 * kasan_populate_zero_shadow() from replacing the page table entries 171 * (PMD or PTE) at the edges of the shadow region for the kernel 172 * image. 173 */ 174 kimg_shadow_start = round_down(kimg_shadow_start, SWAPPER_BLOCK_SIZE); 175 kimg_shadow_end = round_up(kimg_shadow_end, SWAPPER_BLOCK_SIZE); 176 177 kasan_populate_zero_shadow((void *)KASAN_SHADOW_START, 178 (void *)mod_shadow_start); 179 kasan_populate_zero_shadow((void *)kimg_shadow_end, 180 kasan_mem_to_shadow((void *)PAGE_OFFSET)); 181 182 if (kimg_shadow_start > mod_shadow_end) 183 kasan_populate_zero_shadow((void *)mod_shadow_end, 184 (void *)kimg_shadow_start); 185 186 for_each_memblock(memory, reg) { 187 void *start = (void *)__phys_to_virt(reg->base); 188 void *end = (void *)__phys_to_virt(reg->base + reg->size); 189 190 if (start >= end) 191 break; 192 193 /* 194 * end + 1 here is intentional. We check several shadow bytes in 195 * advance to slightly speed up fastpath. In some rare cases 196 * we could cross boundary of mapped shadow, so we just map 197 * some more here. 198 */ 199 vmemmap_populate((unsigned long)kasan_mem_to_shadow(start), 200 (unsigned long)kasan_mem_to_shadow(end) + 1, 201 pfn_to_nid(virt_to_pfn(start))); 202 } 203 204 /* 205 * KAsan may reuse the contents of kasan_zero_pte directly, so we 206 * should make sure that it maps the zero page read-only. 207 */ 208 for (i = 0; i < PTRS_PER_PTE; i++) 209 set_pte(&kasan_zero_pte[i], 210 pfn_pte(sym_to_pfn(kasan_zero_page), PAGE_KERNEL_RO)); 211 212 memset(kasan_zero_page, 0, PAGE_SIZE); 213 cpu_replace_ttbr1(lm_alias(swapper_pg_dir)); 214 215 /* At this point kasan is fully initialized. Enable error messages */ 216 init_task.kasan_depth = 0; 217 pr_info("KernelAddressSanitizer initialized\n"); 218 } 219