arch/arm64/mm/kasan_init.c

   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 phys_addr_t __init kasan_alloc_zeroed_page(int node)
  39 {
  40         void *p = memblock_alloc_try_nid(PAGE_SIZE, PAGE_SIZE,
  41                                               __pa(MAX_DMA_ADDRESS),
  42                                               MEMBLOCK_ALLOC_KASAN, node);
  43         if (!p)
  44                 panic("%s: Failed to allocate %lu bytes align=0x%lx nid=%d from=%llx\n",
  45                       __func__, PAGE_SIZE, PAGE_SIZE, node,
  46                       __pa(MAX_DMA_ADDRESS));
  47
  48         return __pa(p);
  49 }
  50
  51 static phys_addr_t __init kasan_alloc_raw_page(int node)
  52 {
  53         void *p = memblock_alloc_try_nid_raw(PAGE_SIZE, PAGE_SIZE,
  54                                                 __pa(MAX_DMA_ADDRESS),
  55                                                 MEMBLOCK_ALLOC_KASAN, node);
  56         if (!p)
  57                 panic("%s: Failed to allocate %lu bytes align=0x%lx nid=%d from=%llx\n",
  58                       __func__, PAGE_SIZE, PAGE_SIZE, node,
  59                       __pa(MAX_DMA_ADDRESS));
  60
  61         return __pa(p);
  62 }
  63
  64 static pte_t *__init kasan_pte_offset(pmd_t *pmdp, unsigned long addr, int node,
  65                                       bool early)
  66 {
  67         if (pmd_none(READ_ONCE(*pmdp))) {
  68                 phys_addr_t pte_phys = early ?
  69                                 __pa_symbol(kasan_early_shadow_pte)
  70                                         : kasan_alloc_zeroed_page(node);
  71                 __pmd_populate(pmdp, pte_phys, PMD_TYPE_TABLE);
  72         }
  73
  74         return early ? pte_offset_kimg(pmdp, addr)
  75                      : pte_offset_kernel(pmdp, addr);
  76 }
  77
  78 static pmd_t *__init kasan_pmd_offset(pud_t *pudp, unsigned long addr, int node,
  79                                       bool early)
  80 {
  81         if (pud_none(READ_ONCE(*pudp))) {
  82                 phys_addr_t pmd_phys = early ?
  83                                 __pa_symbol(kasan_early_shadow_pmd)
  84                                         : kasan_alloc_zeroed_page(node);
  85                 __pud_populate(pudp, pmd_phys, PMD_TYPE_TABLE);
  86         }
  87
  88         return early ? pmd_offset_kimg(pudp, addr) : pmd_offset(pudp, addr);
  89 }
  90
  91 static pud_t *__init kasan_pud_offset(pgd_t *pgdp, unsigned long addr, int node,
  92                                       bool early)
  93 {
  94         if (pgd_none(READ_ONCE(*pgdp))) {
  95                 phys_addr_t pud_phys = early ?
  96                                 __pa_symbol(kasan_early_shadow_pud)
  97                                         : kasan_alloc_zeroed_page(node);
  98                 __pgd_populate(pgdp, pud_phys, PMD_TYPE_TABLE);
  99         }
 100
 101         return early ? pud_offset_kimg(pgdp, addr) : pud_offset(pgdp, addr);
 102 }
 103
 104 static void __init kasan_pte_populate(pmd_t *pmdp, unsigned long addr,
 105                                       unsigned long end, int node, bool early)
 106 {
 107         unsigned long next;
 108         pte_t *ptep = kasan_pte_offset(pmdp, addr, node, early);
 109
 110         do {
 111                 phys_addr_t page_phys = early ?
 112                                 __pa_symbol(kasan_early_shadow_page)
 113                                         : kasan_alloc_raw_page(node);
 114                 if (!early)
 115                         memset(__va(page_phys), KASAN_SHADOW_INIT, PAGE_SIZE);
 116                 next = addr + PAGE_SIZE;
 117                 set_pte(ptep, pfn_pte(__phys_to_pfn(page_phys), PAGE_KERNEL));
 118         } while (ptep++, addr = next, addr != end && pte_none(READ_ONCE(*ptep)));
 119 }
 120
 121 static void __init kasan_pmd_populate(pud_t *pudp, unsigned long addr,
 122                                       unsigned long end, int node, bool early)
 123 {
 124         unsigned long next;
 125         pmd_t *pmdp = kasan_pmd_offset(pudp, addr, node, early);
 126
 127         do {
 128                 next = pmd_addr_end(addr, end);
 129                 kasan_pte_populate(pmdp, addr, next, node, early);
 130         } while (pmdp++, addr = next, addr != end && pmd_none(READ_ONCE(*pmdp)));
 131 }
 132
 133 static void __init kasan_pud_populate(pgd_t *pgdp, unsigned long addr,
 134                                       unsigned long end, int node, bool early)
 135 {
 136         unsigned long next;
 137         pud_t *pudp = kasan_pud_offset(pgdp, addr, node, early);
 138
 139         do {
 140                 next = pud_addr_end(addr, end);
 141                 kasan_pmd_populate(pudp, addr, next, node, early);
 142         } while (pudp++, addr = next, addr != end && pud_none(READ_ONCE(*pudp)));
 143 }
 144
 145 static void __init kasan_pgd_populate(unsigned long addr, unsigned long end,
 146                                       int node, bool early)
 147 {
 148         unsigned long next;
 149         pgd_t *pgdp;
 150
 151         pgdp = pgd_offset_k(addr);
 152         do {
 153                 next = pgd_addr_end(addr, end);
 154                 kasan_pud_populate(pgdp, addr, next, node, early);
 155         } while (pgdp++, addr = next, addr != end);
 156 }
 157
 158 /* The early shadow maps everything to a single page of zeroes */
 159 asmlinkage void __init kasan_early_init(void)
 160 {
 161         BUILD_BUG_ON(KASAN_SHADOW_OFFSET !=
 162                 KASAN_SHADOW_END - (1UL << (64 - KASAN_SHADOW_SCALE_SHIFT)));
 163         BUILD_BUG_ON(!IS_ALIGNED(KASAN_SHADOW_START, PGDIR_SIZE));
 164         BUILD_BUG_ON(!IS_ALIGNED(KASAN_SHADOW_END, PGDIR_SIZE));
 165         kasan_pgd_populate(KASAN_SHADOW_START, KASAN_SHADOW_END, NUMA_NO_NODE,
 166                            true);
 167 }
 168
 169 /* Set up full kasan mappings, ensuring that the mapped pages are zeroed */
 170 static void __init kasan_map_populate(unsigned long start, unsigned long end,
 171                                       int node)
 172 {
 173         kasan_pgd_populate(start & PAGE_MASK, PAGE_ALIGN(end), node, false);
 174 }
 175
 176 /*
 177  * Copy the current shadow region into a new pgdir.
 178  */
 179 void __init kasan_copy_shadow(pgd_t *pgdir)
 180 {
 181         pgd_t *pgdp, *pgdp_new, *pgdp_end;
 182
 183         pgdp = pgd_offset_k(KASAN_SHADOW_START);
 184         pgdp_end = pgd_offset_k(KASAN_SHADOW_END);
 185         pgdp_new = pgd_offset_raw(pgdir, KASAN_SHADOW_START);
 186         do {
 187                 set_pgd(pgdp_new, READ_ONCE(*pgdp));
 188         } while (pgdp++, pgdp_new++, pgdp != pgdp_end);
 189 }
 190
 191 static void __init clear_pgds(unsigned long start,
 192                         unsigned long end)
 193 {
 194         /*
 195          * Remove references to kasan page tables from
 196          * swapper_pg_dir. pgd_clear() can't be used
 197          * here because it's nop on 2,3-level pagetable setups
 198          */
 199         for (; start < end; start += PGDIR_SIZE)
 200                 set_pgd(pgd_offset_k(start), __pgd(0));
 201 }
 202
 203 void __init kasan_init(void)
 204 {
 205         u64 kimg_shadow_start, kimg_shadow_end;
 206         u64 mod_shadow_start, mod_shadow_end;
 207         struct memblock_region *reg;
 208         int i;
 209
 210         kimg_shadow_start = (u64)kasan_mem_to_shadow(_text) & PAGE_MASK;
 211         kimg_shadow_end = PAGE_ALIGN((u64)kasan_mem_to_shadow(_end));
 212
 213         mod_shadow_start = (u64)kasan_mem_to_shadow((void *)MODULES_VADDR);
 214         mod_shadow_end = (u64)kasan_mem_to_shadow((void *)MODULES_END);
 215
 216         /*
 217          * We are going to perform proper setup of shadow memory.
 218          * At first we should unmap early shadow (clear_pgds() call below).
 219          * However, instrumented code couldn't execute without shadow memory.
 220          * tmp_pg_dir used to keep early shadow mapped until full shadow
 221          * setup will be finished.
 222          */
 223         memcpy(tmp_pg_dir, swapper_pg_dir, sizeof(tmp_pg_dir));
 224         dsb(ishst);
 225         cpu_replace_ttbr1(lm_alias(tmp_pg_dir));
 226
 227         clear_pgds(KASAN_SHADOW_START, KASAN_SHADOW_END);
 228
 229         kasan_map_populate(kimg_shadow_start, kimg_shadow_end,
 230                            early_pfn_to_nid(virt_to_pfn(lm_alias(_text))));
 231
 232         kasan_populate_early_shadow((void *)KASAN_SHADOW_START,
 233                                     (void *)mod_shadow_start);
 234         kasan_populate_early_shadow((void *)kimg_shadow_end,
 235                                     kasan_mem_to_shadow((void *)PAGE_OFFSET));
 236
 237         if (kimg_shadow_start > mod_shadow_end)
 238                 kasan_populate_early_shadow((void *)mod_shadow_end,
 239                                             (void *)kimg_shadow_start);
 240
 241         for_each_memblock(memory, reg) {
 242                 void *start = (void *)__phys_to_virt(reg->base);
 243                 void *end = (void *)__phys_to_virt(reg->base + reg->size);
 244
 245                 if (start >= end)
 246                         break;
 247
 248                 kasan_map_populate((unsigned long)kasan_mem_to_shadow(start),
 249                                    (unsigned long)kasan_mem_to_shadow(end),
 250                                    early_pfn_to_nid(virt_to_pfn(start)));
 251         }
 252
 253         /*
 254          * KAsan may reuse the contents of kasan_early_shadow_pte directly,
 255          * so we should make sure that it maps the zero page read-only.
 256          */
 257         for (i = 0; i < PTRS_PER_PTE; i++)
 258                 set_pte(&kasan_early_shadow_pte[i],
 259                         pfn_pte(sym_to_pfn(kasan_early_shadow_page),
 260                                 PAGE_KERNEL_RO));
 261
 262         memset(kasan_early_shadow_page, KASAN_SHADOW_INIT, PAGE_SIZE);
 263         cpu_replace_ttbr1(lm_alias(swapper_pg_dir));
 264
 265         /* At this point kasan is fully initialized. Enable error messages */
 266         init_task.kasan_depth = 0;
 267         pr_info("KernelAddressSanitizer initialized\n");
 268 }