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/page.h>
  21 #include <asm/pgalloc.h>
  22 #include <asm/procinfo.h>
  23 #include <asm/proc-fns.h>
  24
  25 #include "mm.h"
  26
  27 static pgd_t tmp_pgd_table[PTRS_PER_PGD] __initdata __aligned(PGD_SIZE);
  28
  29 pmd_t tmp_pmd_table[PTRS_PER_PMD] __page_aligned_bss;
  30
  31 static __init void *kasan_alloc_block(size_t size)
  32 {
  33         return memblock_alloc_try_nid(size, size, __pa(MAX_DMA_ADDRESS),
  34                                       MEMBLOCK_ALLOC_NOLEAKTRACE, NUMA_NO_NODE);
  35 }
  36
  37 static void __init kasan_pte_populate(pmd_t *pmdp, unsigned long addr,
  38                                       unsigned long end, bool early)
  39 {
  40         unsigned long next;
  41         pte_t *ptep = pte_offset_kernel(pmdp, addr);
  42
  43         do {
  44                 pte_t entry;
  45                 void *p;
  46
  47                 next = addr + PAGE_SIZE;
  48
  49                 if (!early) {
  50                         if (!pte_none(READ_ONCE(*ptep)))
  51                                 continue;
  52
  53                         p = kasan_alloc_block(PAGE_SIZE);
  54                         if (!p) {
  55                                 panic("%s failed to allocate shadow page for address 0x%lx\n",
  56                                       __func__, addr);
  57                                 return;
  58                         }
  59                         memset(p, KASAN_SHADOW_INIT, PAGE_SIZE);
  60                         entry = pfn_pte(virt_to_pfn(p),
  61                                         __pgprot(pgprot_val(PAGE_KERNEL)));
  62                 } else if (pte_none(READ_ONCE(*ptep))) {
  63                         /*
  64                          * The early shadow memory is mapping all KASan
  65                          * operations to one and the same page in memory,
  66                          * "kasan_early_shadow_page" so that the instrumentation
  67                          * will work on a scratch area until we can set up the
  68                          * proper KASan shadow memory.
  69                          */
  70                         entry = pfn_pte(virt_to_pfn(kasan_early_shadow_page),
  71                                         __pgprot(_L_PTE_DEFAULT | L_PTE_DIRTY | L_PTE_XN));
  72                 } else {
  73                         /*
  74                          * Early shadow mappings are PMD_SIZE aligned, so if the
  75                          * first entry is already set, they must all be set.
  76                          */
  77                         return;
  78                 }
  79
  80                 set_pte_at(&init_mm, addr, ptep, entry);
  81         } while (ptep++, addr = next, addr != end);
  82 }
  83
  84 /*
  85  * The pmd (page middle directory) is only used on LPAE
  86  */
  87 static void __init kasan_pmd_populate(pud_t *pudp, unsigned long addr,
  88                                       unsigned long end, bool early)
  89 {
  90         unsigned long next;
  91         pmd_t *pmdp = pmd_offset(pudp, addr);
  92
  93         do {
  94                 if (pmd_none(*pmdp)) {
  95                         /*
  96                          * We attempt to allocate a shadow block for the PMDs
  97                          * used by the PTEs for this address if it isn't already
  98                          * allocated.
  99                          */
 100                         void *p = early ? kasan_early_shadow_pte :
 101                                 kasan_alloc_block(PAGE_SIZE);
 102
 103                         if (!p) {
 104                                 panic("%s failed to allocate shadow block for address 0x%lx\n",
 105                                       __func__, addr);
 106                                 return;
 107                         }
 108                         pmd_populate_kernel(&init_mm, pmdp, p);
 109                         flush_pmd_entry(pmdp);
 110                 }
 111
 112                 next = pmd_addr_end(addr, end);
 113                 kasan_pte_populate(pmdp, addr, next, early);
 114         } while (pmdp++, addr = next, addr != end);
 115 }
 116
 117 static void __init kasan_pgd_populate(unsigned long addr, unsigned long end,
 118                                       bool early)
 119 {
 120         unsigned long next;
 121         pgd_t *pgdp;
 122         p4d_t *p4dp;
 123         pud_t *pudp;
 124
 125         pgdp = pgd_offset_k(addr);
 126
 127         do {
 128                 /*
 129                  * Allocate and populate the shadow block of p4d folded into
 130                  * pud folded into pmd if it doesn't already exist
 131                  */
 132                 if (!early && pgd_none(*pgdp)) {
 133                         void *p = kasan_alloc_block(PAGE_SIZE);
 134
 135                         if (!p) {
 136                                 panic("%s failed to allocate shadow block for address 0x%lx\n",
 137                                       __func__, addr);
 138                                 return;
 139                         }
 140                         pgd_populate(&init_mm, pgdp, p);
 141                 }
 142
 143                 next = pgd_addr_end(addr, end);
 144                 /*
 145                  * We just immediately jump over the p4d and pud page
 146                  * directories since we believe ARM32 will never gain four
 147                  * nor five level page tables.
 148                  */
 149                 p4dp = p4d_offset(pgdp, addr);
 150                 pudp = pud_offset(p4dp, addr);
 151
 152                 kasan_pmd_populate(pudp, addr, next, early);
 153         } while (pgdp++, addr = next, addr != end);
 154 }
 155
 156 extern struct proc_info_list *lookup_processor_type(unsigned int);
 157
 158 void __init kasan_early_init(void)
 159 {
 160         struct proc_info_list *list;
 161
 162         /*
 163          * locate processor in the list of supported processor
 164          * types.  The linker builds this table for us from the
 165          * entries in arch/arm/mm/proc-*.S
 166          */
 167         list = lookup_processor_type(read_cpuid_id());
 168         if (list) {
 169 #ifdef MULTI_CPU
 170                 processor = *list->proc;
 171 #endif
 172         }
 173
 174         BUILD_BUG_ON((KASAN_SHADOW_END - (1UL << 29)) != KASAN_SHADOW_OFFSET);
 175         /*
 176          * We walk the page table and set all of the shadow memory to point
 177          * to the scratch page.
 178          */
 179         kasan_pgd_populate(KASAN_SHADOW_START, KASAN_SHADOW_END, true);
 180 }
 181
 182 static void __init clear_pgds(unsigned long start,
 183                         unsigned long end)
 184 {
 185         for (; start && start < end; start += PMD_SIZE)
 186                 pmd_clear(pmd_off_k(start));
 187 }
 188
 189 static int __init create_mapping(void *start, void *end)
 190 {
 191         void *shadow_start, *shadow_end;
 192
 193         shadow_start = kasan_mem_to_shadow(start);
 194         shadow_end = kasan_mem_to_shadow(end);
 195
 196         pr_info("Mapping kernel virtual memory block: %px-%px at shadow: %px-%px\n",
 197                 start, end, shadow_start, shadow_end);
 198
 199         kasan_pgd_populate((unsigned long)shadow_start & PAGE_MASK,
 200                            PAGE_ALIGN((unsigned long)shadow_end), false);
 201         return 0;
 202 }
 203
 204 void __init kasan_init(void)
 205 {
 206         phys_addr_t pa_start, pa_end;
 207         u64 i;
 208
 209         /*
 210          * We are going to perform proper setup of shadow memory.
 211          *
 212          * At first we should unmap early shadow (clear_pgds() call bellow).
 213          * However, instrumented code can't execute without shadow memory.
 214          *
 215          * To keep the early shadow memory MMU tables around while setting up
 216          * the proper shadow memory, we copy swapper_pg_dir (the initial page
 217          * table) to tmp_pgd_table and use that to keep the early shadow memory
 218          * mapped until the full shadow setup is finished. Then we swap back
 219          * to the proper swapper_pg_dir.
 220          */
 221
 222         memcpy(tmp_pgd_table, swapper_pg_dir, sizeof(tmp_pgd_table));
 223 #ifdef CONFIG_ARM_LPAE
 224         /* We need to be in the same PGD or this won't work */
 225         BUILD_BUG_ON(pgd_index(KASAN_SHADOW_START) !=
 226                      pgd_index(KASAN_SHADOW_END));
 227         memcpy(tmp_pmd_table,
 228                (void*)pgd_page_vaddr(*pgd_offset_k(KASAN_SHADOW_START)),
 229                sizeof(tmp_pmd_table));
 230         set_pgd(&tmp_pgd_table[pgd_index(KASAN_SHADOW_START)],
 231                 __pgd(__pa(tmp_pmd_table) | PMD_TYPE_TABLE | L_PGD_SWAPPER));
 232 #endif
 233         cpu_switch_mm(tmp_pgd_table, &init_mm);
 234         local_flush_tlb_all();
 235
 236         clear_pgds(KASAN_SHADOW_START, KASAN_SHADOW_END);
 237
 238         if (!IS_ENABLED(CONFIG_KASAN_VMALLOC))
 239                 kasan_populate_early_shadow(kasan_mem_to_shadow((void *)VMALLOC_START),
 240                                             kasan_mem_to_shadow((void *)VMALLOC_END));
 241
 242         kasan_populate_early_shadow(kasan_mem_to_shadow((void *)VMALLOC_END),
 243                                     kasan_mem_to_shadow((void *)-1UL) + 1);
 244
 245         for_each_mem_range(i, &pa_start, &pa_end) {
 246                 void *start = __va(pa_start);
 247                 void *end = __va(pa_end);
 248
 249                 /* Do not attempt to shadow highmem */
 250                 if (pa_start >= arm_lowmem_limit) {
 251                         pr_info("Skip highmem block at %pa-%pa\n", &pa_start, &pa_end);
 252                         continue;
 253                 }
 254                 if (pa_end > arm_lowmem_limit) {
 255                         pr_info("Truncating shadow for memory block at %pa-%pa to lowmem region at %pa\n",
 256                                 &pa_start, &pa_end, &arm_lowmem_limit);
 257                         end = __va(arm_lowmem_limit);
 258                 }
 259                 if (start >= end) {
 260                         pr_info("Skipping invalid memory block %pa-%pa (virtual %p-%p)\n",
 261                                 &pa_start, &pa_end, start, end);
 262                         continue;
 263                 }
 264
 265                 create_mapping(start, end);
 266         }
 267
 268         /*
 269          * 1. The module global variables are in MODULES_VADDR ~ MODULES_END,
 270          *    so we need to map this area if CONFIG_KASAN_VMALLOC=n. With
 271          *    VMALLOC support KASAN will manage this region dynamically,
 272          *    refer to kasan_populate_vmalloc() and ARM's implementation of
 273          *    module_alloc().
 274          * 2. PKMAP_BASE ~ PKMAP_BASE+PMD_SIZE's shadow and MODULES_VADDR
 275          *    ~ MODULES_END's shadow is in the same PMD_SIZE, so we can't
 276          *    use kasan_populate_zero_shadow.
 277          */
 278         if (!IS_ENABLED(CONFIG_KASAN_VMALLOC) && IS_ENABLED(CONFIG_MODULES))
 279                 create_mapping((void *)MODULES_VADDR, (void *)(MODULES_END));
 280         create_mapping((void *)PKMAP_BASE, (void *)(PKMAP_BASE + PMD_SIZE));
 281
 282         /*
 283          * KAsan may reuse the contents of kasan_early_shadow_pte directly, so
 284          * we should make sure that it maps the zero page read-only.
 285          */
 286         for (i = 0; i < PTRS_PER_PTE; i++)
 287                 set_pte_at(&init_mm, KASAN_SHADOW_START + i*PAGE_SIZE,
 288                            &kasan_early_shadow_pte[i],
 289                            pfn_pte(virt_to_pfn(kasan_early_shadow_page),
 290                                 __pgprot(pgprot_val(PAGE_KERNEL)
 291                                          | L_PTE_RDONLY)));
 292
 293         cpu_switch_mm(swapper_pg_dir, &init_mm);
 294         local_flush_tlb_all();
 295
 296         memset(kasan_early_shadow_page, 0, PAGE_SIZE);
 297         pr_info("Kernel address sanitizer initialized\n");
 298         init_task.kasan_depth = 0;
 299 }