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