mm/kasan/kasan_init.c

   1 /*
   2  * This file contains some kasan initialization code.
   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 #include <linux/bootmem.h>
  14 #include <linux/init.h>
  15 #include <linux/kasan.h>
  16 #include <linux/kernel.h>
  17 #include <linux/memblock.h>
  18 #include <linux/mm.h>
  19 #include <linux/pfn.h>
  20
  21 #include <asm/page.h>
  22 #include <asm/pgalloc.h>
  23
  24 /*
  25  * This page serves two purposes:
  26  *   - It used as early shadow memory. The entire shadow region populated
  27  *     with this page, before we will be able to setup normal shadow memory.
  28  *   - Latter it reused it as zero shadow to cover large ranges of memory
  29  *     that allowed to access, but not handled by kasan (vmalloc/vmemmap ...).
  30  */
  31 unsigned char kasan_zero_page[PAGE_SIZE] __page_aligned_bss;
  32
  33 #if CONFIG_PGTABLE_LEVELS > 3
  34 pud_t kasan_zero_pud[PTRS_PER_PUD] __page_aligned_bss;
  35 #endif
  36 #if CONFIG_PGTABLE_LEVELS > 2
  37 pmd_t kasan_zero_pmd[PTRS_PER_PMD] __page_aligned_bss;
  38 #endif
  39 pte_t kasan_zero_pte[PTRS_PER_PTE] __page_aligned_bss;
  40
  41 static __init void *early_alloc(size_t size, int node)
  42 {
  43         return memblock_virt_alloc_try_nid(size, size, __pa(MAX_DMA_ADDRESS),
  44                                         BOOTMEM_ALLOC_ACCESSIBLE, node);
  45 }
  46
  47 static void __init zero_pte_populate(pmd_t *pmd, unsigned long addr,
  48                                 unsigned long end)
  49 {
  50         pte_t *pte = pte_offset_kernel(pmd, addr);
  51         pte_t zero_pte;
  52
  53         zero_pte = pfn_pte(PFN_DOWN(__pa_symbol(kasan_zero_page)), PAGE_KERNEL);
  54         zero_pte = pte_wrprotect(zero_pte);
  55
  56         while (addr + PAGE_SIZE <= end) {
  57                 set_pte_at(&init_mm, addr, pte, zero_pte);
  58                 addr += PAGE_SIZE;
  59                 pte = pte_offset_kernel(pmd, addr);
  60         }
  61 }
  62
  63 static void __init zero_pmd_populate(pud_t *pud, unsigned long addr,
  64                                 unsigned long end)
  65 {
  66         pmd_t *pmd = pmd_offset(pud, addr);
  67         unsigned long next;
  68
  69         do {
  70                 next = pmd_addr_end(addr, end);
  71
  72                 if (IS_ALIGNED(addr, PMD_SIZE) && end - addr >= PMD_SIZE) {
  73                         pmd_populate_kernel(&init_mm, pmd, lm_alias(kasan_zero_pte));
  74                         continue;
  75                 }
  76
  77                 if (pmd_none(*pmd)) {
  78                         pmd_populate_kernel(&init_mm, pmd,
  79                                         early_alloc(PAGE_SIZE, NUMA_NO_NODE));
  80                 }
  81                 zero_pte_populate(pmd, addr, next);
  82         } while (pmd++, addr = next, addr != end);
  83 }
  84
  85 static void __init zero_pud_populate(pgd_t *pgd, unsigned long addr,
  86                                 unsigned long end)
  87 {
  88         pud_t *pud = pud_offset(pgd, addr);
  89         unsigned long next;
  90
  91         do {
  92                 next = pud_addr_end(addr, end);
  93                 if (IS_ALIGNED(addr, PUD_SIZE) && end - addr >= PUD_SIZE) {
  94                         pmd_t *pmd;
  95
  96                         pud_populate(&init_mm, pud, lm_alias(kasan_zero_pmd));
  97                         pmd = pmd_offset(pud, addr);
  98                         pmd_populate_kernel(&init_mm, pmd, lm_alias(kasan_zero_pte));
  99                         continue;
 100                 }
 101
 102                 if (pud_none(*pud)) {
 103                         pud_populate(&init_mm, pud,
 104                                 early_alloc(PAGE_SIZE, NUMA_NO_NODE));
 105                 }
 106                 zero_pmd_populate(pud, addr, next);
 107         } while (pud++, addr = next, addr != end);
 108 }
 109
 110 /**
 111  * kasan_populate_zero_shadow - populate shadow memory region with
 112  *                               kasan_zero_page
 113  * @shadow_start - start of the memory range to populate
 114  * @shadow_end   - end of the memory range to populate
 115  */
 116 void __init kasan_populate_zero_shadow(const void *shadow_start,
 117                                 const void *shadow_end)
 118 {
 119         unsigned long addr = (unsigned long)shadow_start;
 120         unsigned long end = (unsigned long)shadow_end;
 121         pgd_t *pgd = pgd_offset_k(addr);
 122         unsigned long next;
 123
 124         do {
 125                 next = pgd_addr_end(addr, end);
 126
 127                 if (IS_ALIGNED(addr, PGDIR_SIZE) && end - addr >= PGDIR_SIZE) {
 128                         pud_t *pud;
 129                         pmd_t *pmd;
 130
 131                         /*
 132                          * kasan_zero_pud should be populated with pmds
 133                          * at this moment.
 134                          * [pud,pmd]_populate*() below needed only for
 135                          * 3,2 - level page tables where we don't have
 136                          * puds,pmds, so pgd_populate(), pud_populate()
 137                          * is noops.
 138                          */
 139                         pgd_populate(&init_mm, pgd, lm_alias(kasan_zero_pud));
 140                         pud = pud_offset(pgd, addr);
 141                         pud_populate(&init_mm, pud, lm_alias(kasan_zero_pmd));
 142                         pmd = pmd_offset(pud, addr);
 143                         pmd_populate_kernel(&init_mm, pmd, lm_alias(kasan_zero_pte));
 144                         continue;
 145                 }
 146
 147                 if (pgd_none(*pgd)) {
 148                         pgd_populate(&init_mm, pgd,
 149                                 early_alloc(PAGE_SIZE, NUMA_NO_NODE));
 150                 }
 151                 zero_pud_populate(pgd, addr, next);
 152         } while (pgd++, addr = next, addr != end);
 153 }