arch/arm/mm/kasan_init.c

   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 }