1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * This file contains kasan initialization code for ARM. 4 * 5 * Copyright (c) 2018 Samsung Electronics Co., Ltd. 6 * Author: Andrey Ryabinin <ryabinin.a.a@gmail.com> 7 * Author: Linus Walleij <linus.walleij@linaro.org> 8 */ 9 10 #define pr_fmt(fmt) "kasan: " fmt 11 #include <linux/kasan.h> 12 #include <linux/kernel.h> 13 #include <linux/memblock.h> 14 #include <linux/sched/task.h> 15 #include <linux/start_kernel.h> 16 #include <linux/pgtable.h> 17 #include <asm/cputype.h> 18 #include <asm/highmem.h> 19 #include <asm/mach/map.h> 20 #include <asm/memory.h> 21 #include <asm/page.h> 22 #include <asm/pgalloc.h> 23 #include <asm/procinfo.h> 24 #include <asm/proc-fns.h> 25 26 #include "mm.h" 27 28 static pgd_t tmp_pgd_table[PTRS_PER_PGD] __initdata __aligned(PGD_SIZE); 29 30 pmd_t tmp_pmd_table[PTRS_PER_PMD] __page_aligned_bss; 31 32 static __init void *kasan_alloc_block(size_t size) 33 { 34 return memblock_alloc_try_nid(size, size, __pa(MAX_DMA_ADDRESS), 35 MEMBLOCK_ALLOC_KASAN, NUMA_NO_NODE); 36 } 37 38 static void __init kasan_pte_populate(pmd_t *pmdp, unsigned long addr, 39 unsigned long end, bool early) 40 { 41 unsigned long next; 42 pte_t *ptep = pte_offset_kernel(pmdp, addr); 43 44 do { 45 pte_t entry; 46 void *p; 47 48 next = addr + PAGE_SIZE; 49 50 if (!early) { 51 if (!pte_none(READ_ONCE(*ptep))) 52 continue; 53 54 p = kasan_alloc_block(PAGE_SIZE); 55 if (!p) { 56 panic("%s failed to allocate shadow page for address 0x%lx\n", 57 __func__, addr); 58 return; 59 } 60 memset(p, KASAN_SHADOW_INIT, PAGE_SIZE); 61 entry = pfn_pte(virt_to_pfn(p), 62 __pgprot(pgprot_val(PAGE_KERNEL))); 63 } else if (pte_none(READ_ONCE(*ptep))) { 64 /* 65 * The early shadow memory is mapping all KASan 66 * operations to one and the same page in memory, 67 * "kasan_early_shadow_page" so that the instrumentation 68 * will work on a scratch area until we can set up the 69 * proper KASan shadow memory. 70 */ 71 entry = pfn_pte(virt_to_pfn(kasan_early_shadow_page), 72 __pgprot(_L_PTE_DEFAULT | L_PTE_DIRTY | L_PTE_XN)); 73 } else { 74 /* 75 * Early shadow mappings are PMD_SIZE aligned, so if the 76 * first entry is already set, they must all be set. 77 */ 78 return; 79 } 80 81 set_pte_at(&init_mm, addr, ptep, entry); 82 } while (ptep++, addr = next, addr != end); 83 } 84 85 /* 86 * The pmd (page middle directory) is only used on LPAE 87 */ 88 static void __init kasan_pmd_populate(pud_t *pudp, unsigned long addr, 89 unsigned long end, bool early) 90 { 91 unsigned long next; 92 pmd_t *pmdp = pmd_offset(pudp, addr); 93 94 do { 95 if (pmd_none(*pmdp)) { 96 /* 97 * We attempt to allocate a shadow block for the PMDs 98 * used by the PTEs for this address if it isn't already 99 * allocated. 100 */ 101 void *p = early ? kasan_early_shadow_pte : 102 kasan_alloc_block(PAGE_SIZE); 103 104 if (!p) { 105 panic("%s failed to allocate shadow block for address 0x%lx\n", 106 __func__, addr); 107 return; 108 } 109 pmd_populate_kernel(&init_mm, pmdp, p); 110 flush_pmd_entry(pmdp); 111 } 112 113 next = pmd_addr_end(addr, end); 114 kasan_pte_populate(pmdp, addr, next, early); 115 } while (pmdp++, addr = next, addr != end); 116 } 117 118 static void __init kasan_pgd_populate(unsigned long addr, unsigned long end, 119 bool early) 120 { 121 unsigned long next; 122 pgd_t *pgdp; 123 p4d_t *p4dp; 124 pud_t *pudp; 125 126 pgdp = pgd_offset_k(addr); 127 128 do { 129 /* 130 * Allocate and populate the shadow block of p4d folded into 131 * pud folded into pmd if it doesn't already exist 132 */ 133 if (!early && pgd_none(*pgdp)) { 134 void *p = kasan_alloc_block(PAGE_SIZE); 135 136 if (!p) { 137 panic("%s failed to allocate shadow block for address 0x%lx\n", 138 __func__, addr); 139 return; 140 } 141 pgd_populate(&init_mm, pgdp, p); 142 } 143 144 next = pgd_addr_end(addr, end); 145 /* 146 * We just immediately jump over the p4d and pud page 147 * directories since we believe ARM32 will never gain four 148 * nor five level page tables. 149 */ 150 p4dp = p4d_offset(pgdp, addr); 151 pudp = pud_offset(p4dp, addr); 152 153 kasan_pmd_populate(pudp, addr, next, early); 154 } while (pgdp++, addr = next, addr != end); 155 } 156 157 extern struct proc_info_list *lookup_processor_type(unsigned int); 158 159 void __init kasan_early_init(void) 160 { 161 struct proc_info_list *list; 162 163 /* 164 * locate processor in the list of supported processor 165 * types. The linker builds this table for us from the 166 * entries in arch/arm/mm/proc-*.S 167 */ 168 list = lookup_processor_type(read_cpuid_id()); 169 if (list) { 170 #ifdef MULTI_CPU 171 processor = *list->proc; 172 #endif 173 } 174 175 BUILD_BUG_ON((KASAN_SHADOW_END - (1UL << 29)) != KASAN_SHADOW_OFFSET); 176 /* 177 * We walk the page table and set all of the shadow memory to point 178 * to the scratch page. 179 */ 180 kasan_pgd_populate(KASAN_SHADOW_START, KASAN_SHADOW_END, true); 181 } 182 183 static void __init clear_pgds(unsigned long start, 184 unsigned long end) 185 { 186 for (; start && start < end; start += PMD_SIZE) 187 pmd_clear(pmd_off_k(start)); 188 } 189 190 static int __init create_mapping(void *start, void *end) 191 { 192 void *shadow_start, *shadow_end; 193 194 shadow_start = kasan_mem_to_shadow(start); 195 shadow_end = kasan_mem_to_shadow(end); 196 197 pr_info("Mapping kernel virtual memory block: %px-%px at shadow: %px-%px\n", 198 start, end, shadow_start, shadow_end); 199 200 kasan_pgd_populate((unsigned long)shadow_start & PAGE_MASK, 201 PAGE_ALIGN((unsigned long)shadow_end), false); 202 return 0; 203 } 204 205 void __init kasan_init(void) 206 { 207 phys_addr_t pa_start, pa_end; 208 u64 i; 209 210 /* 211 * We are going to perform proper setup of shadow memory. 212 * 213 * At first we should unmap early shadow (clear_pgds() call bellow). 214 * However, instrumented code can't execute without shadow memory. 215 * 216 * To keep the early shadow memory MMU tables around while setting up 217 * the proper shadow memory, we copy swapper_pg_dir (the initial page 218 * table) to tmp_pgd_table and use that to keep the early shadow memory 219 * mapped until the full shadow setup is finished. Then we swap back 220 * to the proper swapper_pg_dir. 221 */ 222 223 memcpy(tmp_pgd_table, swapper_pg_dir, sizeof(tmp_pgd_table)); 224 #ifdef CONFIG_ARM_LPAE 225 /* We need to be in the same PGD or this won't work */ 226 BUILD_BUG_ON(pgd_index(KASAN_SHADOW_START) != 227 pgd_index(KASAN_SHADOW_END)); 228 memcpy(tmp_pmd_table, 229 pgd_page_vaddr(*pgd_offset_k(KASAN_SHADOW_START)), 230 sizeof(tmp_pmd_table)); 231 set_pgd(&tmp_pgd_table[pgd_index(KASAN_SHADOW_START)], 232 __pgd(__pa(tmp_pmd_table) | PMD_TYPE_TABLE | L_PGD_SWAPPER)); 233 #endif 234 cpu_switch_mm(tmp_pgd_table, &init_mm); 235 local_flush_tlb_all(); 236 237 clear_pgds(KASAN_SHADOW_START, KASAN_SHADOW_END); 238 239 kasan_populate_early_shadow(kasan_mem_to_shadow((void *)VMALLOC_START), 240 kasan_mem_to_shadow((void *)-1UL) + 1); 241 242 for_each_mem_range(i, &pa_start, &pa_end) { 243 void *start = __va(pa_start); 244 void *end = __va(pa_end); 245 246 /* Do not attempt to shadow highmem */ 247 if (pa_start >= arm_lowmem_limit) { 248 pr_info("Skip highmem block at %pa-%pa\n", &pa_start, &pa_end); 249 continue; 250 } 251 if (pa_end > arm_lowmem_limit) { 252 pr_info("Truncating shadow for memory block at %pa-%pa to lowmem region at %pa\n", 253 &pa_start, &pa_end, &arm_lowmem_limit); 254 end = __va(arm_lowmem_limit); 255 } 256 if (start >= end) { 257 pr_info("Skipping invalid memory block %pa-%pa (virtual %p-%p)\n", 258 &pa_start, &pa_end, start, end); 259 continue; 260 } 261 262 create_mapping(start, end); 263 } 264 265 /* 266 * 1. The module global variables are in MODULES_VADDR ~ MODULES_END, 267 * so we need to map this area. 268 * 2. PKMAP_BASE ~ PKMAP_BASE+PMD_SIZE's shadow and MODULES_VADDR 269 * ~ MODULES_END's shadow is in the same PMD_SIZE, so we can't 270 * use kasan_populate_zero_shadow. 271 */ 272 create_mapping((void *)MODULES_VADDR, (void *)(PKMAP_BASE + PMD_SIZE)); 273 274 /* 275 * KAsan may reuse the contents of kasan_early_shadow_pte directly, so 276 * we should make sure that it maps the zero page read-only. 277 */ 278 for (i = 0; i < PTRS_PER_PTE; i++) 279 set_pte_at(&init_mm, KASAN_SHADOW_START + i*PAGE_SIZE, 280 &kasan_early_shadow_pte[i], 281 pfn_pte(virt_to_pfn(kasan_early_shadow_page), 282 __pgprot(pgprot_val(PAGE_KERNEL) 283 | L_PTE_RDONLY))); 284 285 cpu_switch_mm(swapper_pg_dir, &init_mm); 286 local_flush_tlb_all(); 287 288 memset(kasan_early_shadow_page, 0, PAGE_SIZE); 289 pr_info("Kernel address sanitizer initialized\n"); 290 init_task.kasan_depth = 0; 291 } 292