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/bootmem.h>
  15 #include <linux/kasan.h>
  16 #include <linux/kernel.h>
  17 #include <linux/sched/task.h>
  18 #include <linux/memblock.h>
  19 #include <linux/start_kernel.h>
  20 #include <linux/mm.h>
  21
  22 #include <asm/mmu_context.h>
  23 #include <asm/kernel-pgtable.h>
  24 #include <asm/page.h>
  25 #include <asm/pgalloc.h>
  26 #include <asm/pgtable.h>
  27 #include <asm/sections.h>
  28 #include <asm/tlbflush.h>
  29
  30 static pgd_t tmp_pg_dir[PTRS_PER_PGD] __initdata __aligned(PGD_SIZE);
  31
  32 /*
  33  * The p*d_populate functions call virt_to_phys implicitly so they can't be used
  34  * directly on kernel symbols (bm_p*d). All the early functions are called too
  35  * early to use lm_alias so __p*d_populate functions must be used to populate
  36  * with the physical address from __pa_symbol.
  37  */
  38
  39 static phys_addr_t __init kasan_alloc_zeroed_page(int node)
  40 {
  41         void *p = memblock_virt_alloc_try_nid(PAGE_SIZE, PAGE_SIZE,
  42                                               __pa(MAX_DMA_ADDRESS),
  43                                               MEMBLOCK_ALLOC_ACCESSIBLE, node);
  44         return __pa(p);
  45 }
  46
  47 static pte_t *__init kasan_pte_offset(pmd_t *pmd, unsigned long addr, int node,
  48                                       bool early)
  49 {
  50         if (pmd_none(*pmd)) {
  51                 phys_addr_t pte_phys = early ? __pa_symbol(kasan_zero_pte)
  52                                              : kasan_alloc_zeroed_page(node);
  53                 __pmd_populate(pmd, pte_phys, PMD_TYPE_TABLE);
  54         }
  55
  56         return early ? pte_offset_kimg(pmd, addr)
  57                      : pte_offset_kernel(pmd, addr);
  58 }
  59
  60 static pmd_t *__init kasan_pmd_offset(pud_t *pud, unsigned long addr, int node,
  61                                       bool early)
  62 {
  63         if (pud_none(*pud)) {
  64                 phys_addr_t pmd_phys = early ? __pa_symbol(kasan_zero_pmd)
  65                                              : kasan_alloc_zeroed_page(node);
  66                 __pud_populate(pud, pmd_phys, PMD_TYPE_TABLE);
  67         }
  68
  69         return early ? pmd_offset_kimg(pud, addr) : pmd_offset(pud, addr);
  70 }
  71
  72 static pud_t *__init kasan_pud_offset(pgd_t *pgd, unsigned long addr, int node,
  73                                       bool early)
  74 {
  75         if (pgd_none(*pgd)) {
  76                 phys_addr_t pud_phys = early ? __pa_symbol(kasan_zero_pud)
  77                                              : kasan_alloc_zeroed_page(node);
  78                 __pgd_populate(pgd, pud_phys, PMD_TYPE_TABLE);
  79         }
  80
  81         return early ? pud_offset_kimg(pgd, addr) : pud_offset(pgd, addr);
  82 }
  83
  84 static void __init kasan_pte_populate(pmd_t *pmd, unsigned long addr,
  85                                       unsigned long end, int node, bool early)
  86 {
  87         unsigned long next;
  88         pte_t *pte = kasan_pte_offset(pmd, addr, node, early);
  89
  90         do {
  91                 phys_addr_t page_phys = early ? __pa_symbol(kasan_zero_page)
  92                                               : kasan_alloc_zeroed_page(node);
  93                 next = addr + PAGE_SIZE;
  94                 set_pte(pte, pfn_pte(__phys_to_pfn(page_phys), PAGE_KERNEL));
  95         } while (pte++, addr = next, addr != end && pte_none(*pte));
  96 }
  97
  98 static void __init kasan_pmd_populate(pud_t *pud, unsigned long addr,
  99                                       unsigned long end, int node, bool early)
 100 {
 101         unsigned long next;
 102         pmd_t *pmd = kasan_pmd_offset(pud, addr, node, early);
 103
 104         do {
 105                 next = pmd_addr_end(addr, end);
 106                 kasan_pte_populate(pmd, addr, next, node, early);
 107         } while (pmd++, addr = next, addr != end && pmd_none(*pmd));
 108 }
 109
 110 static void __init kasan_pud_populate(pgd_t *pgd, unsigned long addr,
 111                                       unsigned long end, int node, bool early)
 112 {
 113         unsigned long next;
 114         pud_t *pud = kasan_pud_offset(pgd, addr, node, early);
 115
 116         do {
 117                 next = pud_addr_end(addr, end);
 118                 kasan_pmd_populate(pud, addr, next, node, early);
 119         } while (pud++, addr = next, addr != end && pud_none(*pud));
 120 }
 121
 122 static void __init kasan_pgd_populate(unsigned long addr, unsigned long end,
 123                                       int node, bool early)
 124 {
 125         unsigned long next;
 126         pgd_t *pgd;
 127
 128         pgd = pgd_offset_k(addr);
 129         do {
 130                 next = pgd_addr_end(addr, end);
 131                 kasan_pud_populate(pgd, addr, next, node, early);
 132         } while (pgd++, addr = next, addr != end);
 133 }
 134
 135 /* The early shadow maps everything to a single page of zeroes */
 136 asmlinkage void __init kasan_early_init(void)
 137 {
 138         BUILD_BUG_ON(KASAN_SHADOW_OFFSET !=
 139                 KASAN_SHADOW_END - (1UL << (64 - KASAN_SHADOW_SCALE_SHIFT)));
 140         BUILD_BUG_ON(!IS_ALIGNED(KASAN_SHADOW_START, PGDIR_SIZE));
 141         BUILD_BUG_ON(!IS_ALIGNED(KASAN_SHADOW_END, PGDIR_SIZE));
 142         kasan_pgd_populate(KASAN_SHADOW_START, KASAN_SHADOW_END, NUMA_NO_NODE,
 143                            true);
 144 }
 145
 146 /* Set up full kasan mappings, ensuring that the mapped pages are zeroed */
 147 static void __init kasan_map_populate(unsigned long start, unsigned long end,
 148                                       int node)
 149 {
 150         kasan_pgd_populate(start & PAGE_MASK, PAGE_ALIGN(end), node, false);
 151 }
 152
 153 /*
 154  * Copy the current shadow region into a new pgdir.
 155  */
 156 void __init kasan_copy_shadow(pgd_t *pgdir)
 157 {
 158         pgd_t *pgd, *pgd_new, *pgd_end;
 159
 160         pgd = pgd_offset_k(KASAN_SHADOW_START);
 161         pgd_end = pgd_offset_k(KASAN_SHADOW_END);
 162         pgd_new = pgd_offset_raw(pgdir, KASAN_SHADOW_START);
 163         do {
 164                 set_pgd(pgd_new, *pgd);
 165         } while (pgd++, pgd_new++, pgd != pgd_end);
 166 }
 167
 168 static void __init clear_pgds(unsigned long start,
 169                         unsigned long end)
 170 {
 171         /*
 172          * Remove references to kasan page tables from
 173          * swapper_pg_dir. pgd_clear() can't be used
 174          * here because it's nop on 2,3-level pagetable setups
 175          */
 176         for (; start < end; start += PGDIR_SIZE)
 177                 set_pgd(pgd_offset_k(start), __pgd(0));
 178 }
 179
 180 void __init kasan_init(void)
 181 {
 182         u64 kimg_shadow_start, kimg_shadow_end;
 183         u64 mod_shadow_start, mod_shadow_end;
 184         struct memblock_region *reg;
 185         int i;
 186
 187         kimg_shadow_start = (u64)kasan_mem_to_shadow(_text) & PAGE_MASK;
 188         kimg_shadow_end = PAGE_ALIGN((u64)kasan_mem_to_shadow(_end));
 189
 190         mod_shadow_start = (u64)kasan_mem_to_shadow((void *)MODULES_VADDR);
 191         mod_shadow_end = (u64)kasan_mem_to_shadow((void *)MODULES_END);
 192
 193         /*
 194          * We are going to perform proper setup of shadow memory.
 195          * At first we should unmap early shadow (clear_pgds() call bellow).
 196          * However, instrumented code couldn't execute without shadow memory.
 197          * tmp_pg_dir used to keep early shadow mapped until full shadow
 198          * setup will be finished.
 199          */
 200         memcpy(tmp_pg_dir, swapper_pg_dir, sizeof(tmp_pg_dir));
 201         dsb(ishst);
 202         cpu_replace_ttbr1(lm_alias(tmp_pg_dir));
 203
 204         clear_pgds(KASAN_SHADOW_START, KASAN_SHADOW_END);
 205
 206         kasan_map_populate(kimg_shadow_start, kimg_shadow_end,
 207                            pfn_to_nid(virt_to_pfn(lm_alias(_text))));
 208
 209         kasan_populate_zero_shadow((void *)KASAN_SHADOW_START,
 210                                    (void *)mod_shadow_start);
 211         kasan_populate_zero_shadow((void *)kimg_shadow_end,
 212                                    kasan_mem_to_shadow((void *)PAGE_OFFSET));
 213
 214         if (kimg_shadow_start > mod_shadow_end)
 215                 kasan_populate_zero_shadow((void *)mod_shadow_end,
 216                                            (void *)kimg_shadow_start);
 217
 218         for_each_memblock(memory, reg) {
 219                 void *start = (void *)__phys_to_virt(reg->base);
 220                 void *end = (void *)__phys_to_virt(reg->base + reg->size);
 221
 222                 if (start >= end)
 223                         break;
 224
 225                 kasan_map_populate((unsigned long)kasan_mem_to_shadow(start),
 226                                    (unsigned long)kasan_mem_to_shadow(end),
 227                                    pfn_to_nid(virt_to_pfn(start)));
 228         }
 229
 230         /*
 231          * KAsan may reuse the contents of kasan_zero_pte directly, so we
 232          * should make sure that it maps the zero page read-only.
 233          */
 234         for (i = 0; i < PTRS_PER_PTE; i++)
 235                 set_pte(&kasan_zero_pte[i],
 236                         pfn_pte(sym_to_pfn(kasan_zero_page), PAGE_KERNEL_RO));
 237
 238         memset(kasan_zero_page, 0, PAGE_SIZE);
 239         cpu_replace_ttbr1(lm_alias(swapper_pg_dir));
 240
 241         /* At this point kasan is fully initialized. Enable error messages */
 242         init_task.kasan_depth = 0;
 243         pr_info("KernelAddressSanitizer initialized\n");
 244 }