LXR linux/arch/arm64/mm/kasan

   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/memblock.h>
  17#include <linux/start_kernel.h>
  18
  19#include <asm/page.h>
  20#include <asm/pgalloc.h>
  21#include <asm/pgtable.h>
  22#include <asm/tlbflush.h>
  23
  24static pgd_t tmp_pg_dir[PTRS_PER_PGD] __initdata __aligned(PGD_SIZE);
  25
  26static void __init kasan_early_pte_populate(pmd_t *pmd, unsigned long addr,
  27                                        unsigned long end)
  28{
  29        pte_t *pte;
  30        unsigned long next;
  31
  32        if (pmd_none(*pmd))
  33                pmd_populate_kernel(&init_mm, pmd, kasan_zero_pte);
  34
  35        pte = pte_offset_kernel(pmd, addr);
  36        do {
  37                next = addr + PAGE_SIZE;
  38                set_pte(pte, pfn_pte(virt_to_pfn(kasan_zero_page),
  39                                        PAGE_KERNEL));
  40        } while (pte++, addr = next, addr != end && pte_none(*pte));
  41}
  42
  43static void __init kasan_early_pmd_populate(pud_t *pud,
  44                                        unsigned long addr,
  45                                        unsigned long end)
  46{
  47        pmd_t *pmd;
  48        unsigned long next;
  49
  50        if (pud_none(*pud))
  51                pud_populate(&init_mm, pud, kasan_zero_pmd);
  52
  53        pmd = pmd_offset(pud, addr);
  54        do {
  55                next = pmd_addr_end(addr, end);
  56                kasan_early_pte_populate(pmd, addr, next);
  57        } while (pmd++, addr = next, addr != end && pmd_none(*pmd));
  58}
  59
  60static void __init kasan_early_pud_populate(pgd_t *pgd,
  61                                        unsigned long addr,
  62                                        unsigned long end)
  63{
  64        pud_t *pud;
  65        unsigned long next;
  66
  67        if (pgd_none(*pgd))
  68                pgd_populate(&init_mm, pgd, kasan_zero_pud);
  69
  70        pud = pud_offset(pgd, addr);
  71        do {
  72                next = pud_addr_end(addr, end);
  73                kasan_early_pmd_populate(pud, addr, next);
  74        } while (pud++, addr = next, addr != end && pud_none(*pud));
  75}
  76
  77static void __init kasan_map_early_shadow(void)
  78{
  79        unsigned long addr = KASAN_SHADOW_START;
  80        unsigned long end = KASAN_SHADOW_END;
  81        unsigned long next;
  82        pgd_t *pgd;
  83
  84        pgd = pgd_offset_k(addr);
  85        do {
  86                next = pgd_addr_end(addr, end);
  87                kasan_early_pud_populate(pgd, addr, next);
  88        } while (pgd++, addr = next, addr != end);
  89}
  90
  91asmlinkage void __init kasan_early_init(void)
  92{
  93        BUILD_BUG_ON(KASAN_SHADOW_OFFSET != KASAN_SHADOW_END - (1UL << 61));
  94        BUILD_BUG_ON(!IS_ALIGNED(KASAN_SHADOW_START, PGDIR_SIZE));
  95        BUILD_BUG_ON(!IS_ALIGNED(KASAN_SHADOW_END, PGDIR_SIZE));
  96        kasan_map_early_shadow();
  97}
  98
  99static void __init clear_pgds(unsigned long start,
 100                        unsigned long end)
 101{
 102        /*
 103         * Remove references to kasan page tables from
 104         * swapper_pg_dir. pgd_clear() can't be used
 105         * here because it's nop on 2,3-level pagetable setups
 106         */
 107        for (; start < end; start += PGDIR_SIZE)
 108                set_pgd(pgd_offset_k(start), __pgd(0));
 109}
 110
 111static void __init cpu_set_ttbr1(unsigned long ttbr1)
 112{
 113        asm(
 114        "       msr     ttbr1_el1, %0\n"
 115        "       isb"
 116        :
 117        : "r" (ttbr1));
 118}
 119
 120void __init kasan_init(void)
 121{
 122        struct memblock_region *reg;
 123        int i;
 124
 125        /*
 126         * We are going to perform proper setup of shadow memory.
 127         * At first we should unmap early shadow (clear_pgds() call bellow).
 128         * However, instrumented code couldn't execute without shadow memory.
 129         * tmp_pg_dir used to keep early shadow mapped until full shadow
 130         * setup will be finished.
 131         */
 132        memcpy(tmp_pg_dir, swapper_pg_dir, sizeof(tmp_pg_dir));
 133        cpu_set_ttbr1(__pa(tmp_pg_dir));
 134        flush_tlb_all();
 135
 136        clear_pgds(KASAN_SHADOW_START, KASAN_SHADOW_END);
 137
 138        kasan_populate_zero_shadow((void *)KASAN_SHADOW_START,
 139                        kasan_mem_to_shadow((void *)MODULES_VADDR));
 140
 141        for_each_memblock(memory, reg) {
 142                void *start = (void *)__phys_to_virt(reg->base);
 143                void *end = (void *)__phys_to_virt(reg->base + reg->size);
 144
 145                if (start >= end)
 146                        break;
 147
 148                /*
 149                 * end + 1 here is intentional. We check several shadow bytes in
 150                 * advance to slightly speed up fastpath. In some rare cases
 151                 * we could cross boundary of mapped shadow, so we just map
 152                 * some more here.
 153                 */
 154                vmemmap_populate((unsigned long)kasan_mem_to_shadow(start),
 155                                (unsigned long)kasan_mem_to_shadow(end) + 1,
 156                                pfn_to_nid(virt_to_pfn(start)));
 157        }
 158
 159        /*
 160         * KAsan may reuse the contents of kasan_zero_pte directly, so we
 161         * should make sure that it maps the zero page read-only.
 162         */
 163        for (i = 0; i < PTRS_PER_PTE; i++)
 164                set_pte(&kasan_zero_pte[i],
 165                        pfn_pte(virt_to_pfn(kasan_zero_page), PAGE_KERNEL_RO));
 166
 167        memset(kasan_zero_page, 0, PAGE_SIZE);
 168        cpu_set_ttbr1(__pa(swapper_pg_dir));
 169        flush_tlb_all();
 170
 171        /* At this point kasan is fully initialized. Enable error messages */
 172        init_task.kasan_depth = 0;
 173        pr_info("KernelAddressSanitizer initialized\n");
 174}
 175