arch/xtensa/mm/kasan_init.c

   1 /*
   2  * Xtensa KASAN shadow map initialization
   3  *
   4  * This file is subject to the terms and conditions of the GNU General Public
   5  * License.  See the file "COPYING" in the main directory of this archive
   6  * for more details.
   7  *
   8  * Copyright (C) 2017 Cadence Design Systems Inc.
   9  */
  10
  11 #include <linux/bootmem.h>
  12 #include <linux/init_task.h>
  13 #include <linux/kasan.h>
  14 #include <linux/kernel.h>
  15 #include <linux/memblock.h>
  16 #include <asm/initialize_mmu.h>
  17 #include <asm/tlbflush.h>
  18 #include <asm/traps.h>
  19
  20 void __init kasan_early_init(void)
  21 {
  22         unsigned long vaddr = KASAN_SHADOW_START;
  23         pgd_t *pgd = pgd_offset_k(vaddr);
  24         pmd_t *pmd = pmd_offset(pgd, vaddr);
  25         int i;
  26
  27         for (i = 0; i < PTRS_PER_PTE; ++i)
  28                 set_pte(kasan_zero_pte + i,
  29                         mk_pte(virt_to_page(kasan_zero_page), PAGE_KERNEL));
  30
  31         for (vaddr = 0; vaddr < KASAN_SHADOW_SIZE; vaddr += PMD_SIZE, ++pmd) {
  32                 BUG_ON(!pmd_none(*pmd));
  33                 set_pmd(pmd, __pmd((unsigned long)kasan_zero_pte));
  34         }
  35         early_trap_init();
  36 }
  37
  38 static void __init populate(void *start, void *end)
  39 {
  40         unsigned long n_pages = (end - start) / PAGE_SIZE;
  41         unsigned long n_pmds = n_pages / PTRS_PER_PTE;
  42         unsigned long i, j;
  43         unsigned long vaddr = (unsigned long)start;
  44         pgd_t *pgd = pgd_offset_k(vaddr);
  45         pmd_t *pmd = pmd_offset(pgd, vaddr);
  46         pte_t *pte = memblock_virt_alloc(n_pages * sizeof(pte_t), PAGE_SIZE);
  47
  48         pr_debug("%s: %p - %p\n", __func__, start, end);
  49
  50         for (i = j = 0; i < n_pmds; ++i) {
  51                 int k;
  52
  53                 for (k = 0; k < PTRS_PER_PTE; ++k, ++j) {
  54                         phys_addr_t phys =
  55                                 memblock_alloc_base(PAGE_SIZE, PAGE_SIZE,
  56                                                     MEMBLOCK_ALLOC_ANYWHERE);
  57
  58                         set_pte(pte + j, pfn_pte(PHYS_PFN(phys), PAGE_KERNEL));
  59                 }
  60         }
  61
  62         for (i = 0; i < n_pmds ; ++i, pte += PTRS_PER_PTE)
  63                 set_pmd(pmd + i, __pmd((unsigned long)pte));
  64
  65         local_flush_tlb_all();
  66         memset(start, 0, end - start);
  67 }
  68
  69 void __init kasan_init(void)
  70 {
  71         int i;
  72
  73         BUILD_BUG_ON(KASAN_SHADOW_OFFSET != KASAN_SHADOW_START -
  74                      (KASAN_START_VADDR >> KASAN_SHADOW_SCALE_SHIFT));
  75         BUILD_BUG_ON(VMALLOC_START < KASAN_START_VADDR);
  76
  77         /*
  78          * Replace shadow map pages that cover addresses from VMALLOC area
  79          * start to the end of KSEG with clean writable pages.
  80          */
  81         populate(kasan_mem_to_shadow((void *)VMALLOC_START),
  82                  kasan_mem_to_shadow((void *)XCHAL_KSEG_BYPASS_VADDR));
  83
  84         /* Write protect kasan_zero_page and zero-initialize it again. */
  85         for (i = 0; i < PTRS_PER_PTE; ++i)
  86                 set_pte(kasan_zero_pte + i,
  87                         mk_pte(virt_to_page(kasan_zero_page), PAGE_KERNEL_RO));
  88
  89         local_flush_tlb_all();
  90         memset(kasan_zero_page, 0, PAGE_SIZE);
  91
  92         /* At this point kasan is fully initialized. Enable error messages. */
  93         current->kasan_depth = 0;
  94         pr_info("KernelAddressSanitizer initialized\n");
  95 }