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