arch/arm64/mm/pageattr.c

   1 /*
   2  * Copyright (c) 2014, The Linux Foundation. All rights reserved.
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License version 2 and
   6  * only version 2 as published by the Free Software Foundation.
   7  *
   8  * This program is distributed in the hope that it will be useful,
   9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  11  * GNU General Public License for more details.
  12  */
  13 #include <linux/kernel.h>
  14 #include <linux/mm.h>
  15 #include <linux/module.h>
  16 #include <linux/sched.h>
  17 #include <linux/vmalloc.h>
  18
  19 #include <asm/pgtable.h>
  20 #include <asm/tlbflush.h>
  21
  22 struct page_change_data {
  23         pgprot_t set_mask;
  24         pgprot_t clear_mask;
  25 };
  26
  27 static int change_page_range(pte_t *ptep, pgtable_t token, unsigned long addr,
  28                         void *data)
  29 {
  30         struct page_change_data *cdata = data;
  31         pte_t pte = *ptep;
  32
  33         pte = clear_pte_bit(pte, cdata->clear_mask);
  34         pte = set_pte_bit(pte, cdata->set_mask);
  35
  36         set_pte(ptep, pte);
  37         return 0;
  38 }
  39
  40 /*
  41  * This function assumes that the range is mapped with PAGE_SIZE pages.
  42  */
  43 static int __change_memory_common(unsigned long start, unsigned long size,
  44                                 pgprot_t set_mask, pgprot_t clear_mask)
  45 {
  46         struct page_change_data data;
  47         int ret;
  48
  49         data.set_mask = set_mask;
  50         data.clear_mask = clear_mask;
  51
  52         ret = apply_to_page_range(&init_mm, start, size, change_page_range,
  53                                         &data);
  54
  55         flush_tlb_kernel_range(start, start + size);
  56         return ret;
  57 }
  58
  59 static int change_memory_common(unsigned long addr, int numpages,
  60                                 pgprot_t set_mask, pgprot_t clear_mask)
  61 {
  62         unsigned long start = addr;
  63         unsigned long size = PAGE_SIZE*numpages;
  64         unsigned long end = start + size;
  65         struct vm_struct *area;
  66
  67         if (!PAGE_ALIGNED(addr)) {
  68                 start &= PAGE_MASK;
  69                 end = start + size;
  70                 WARN_ON_ONCE(1);
  71         }
  72
  73         /*
  74          * Kernel VA mappings are always live, and splitting live section
  75          * mappings into page mappings may cause TLB conflicts. This means
  76          * we have to ensure that changing the permission bits of the range
  77          * we are operating on does not result in such splitting.
  78          *
  79          * Let's restrict ourselves to mappings created by vmalloc (or vmap).
  80          * Those are guaranteed to consist entirely of page mappings, and
  81          * splitting is never needed.
  82          *
  83          * So check whether the [addr, addr + size) interval is entirely
  84          * covered by precisely one VM area that has the VM_ALLOC flag set.
  85          */
  86         area = find_vm_area((void *)addr);
  87         if (!area ||
  88             end > (unsigned long)area->addr + area->size ||
  89             !(area->flags & VM_ALLOC))
  90                 return -EINVAL;
  91
  92         if (!numpages)
  93                 return 0;
  94
  95         return __change_memory_common(start, size, set_mask, clear_mask);
  96 }
  97
  98 int set_memory_ro(unsigned long addr, int numpages)
  99 {
 100         return change_memory_common(addr, numpages,
 101                                         __pgprot(PTE_RDONLY),
 102                                         __pgprot(PTE_WRITE));
 103 }
 104
 105 int set_memory_rw(unsigned long addr, int numpages)
 106 {
 107         return change_memory_common(addr, numpages,
 108                                         __pgprot(PTE_WRITE),
 109                                         __pgprot(PTE_RDONLY));
 110 }
 111
 112 int set_memory_nx(unsigned long addr, int numpages)
 113 {
 114         return change_memory_common(addr, numpages,
 115                                         __pgprot(PTE_PXN),
 116                                         __pgprot(0));
 117 }
 118 EXPORT_SYMBOL_GPL(set_memory_nx);
 119
 120 int set_memory_x(unsigned long addr, int numpages)
 121 {
 122         return change_memory_common(addr, numpages,
 123                                         __pgprot(0),
 124                                         __pgprot(PTE_PXN));
 125 }
 126 EXPORT_SYMBOL_GPL(set_memory_x);
 127
 128 #ifdef CONFIG_DEBUG_PAGEALLOC
 129 void __kernel_map_pages(struct page *page, int numpages, int enable)
 130 {
 131         unsigned long addr = (unsigned long) page_address(page);
 132
 133         if (enable)
 134                 __change_memory_common(addr, PAGE_SIZE * numpages,
 135                                         __pgprot(PTE_VALID),
 136                                         __pgprot(0));
 137         else
 138                 __change_memory_common(addr, PAGE_SIZE * numpages,
 139                                         __pgprot(0),
 140                                         __pgprot(PTE_VALID));
 141 }
 142 #ifdef CONFIG_HIBERNATION
 143 /*
 144  * When built with CONFIG_DEBUG_PAGEALLOC and CONFIG_HIBERNATION, this function
 145  * is used to determine if a linear map page has been marked as not-valid by
 146  * CONFIG_DEBUG_PAGEALLOC. Walk the page table and check the PTE_VALID bit.
 147  * This is based on kern_addr_valid(), which almost does what we need.
 148  *
 149  * Because this is only called on the kernel linear map,  p?d_sect() implies
 150  * p?d_present(). When debug_pagealloc is enabled, sections mappings are
 151  * disabled.
 152  */
 153 bool kernel_page_present(struct page *page)
 154 {
 155         pgd_t *pgd;
 156         pud_t *pud;
 157         pmd_t *pmd;
 158         pte_t *pte;
 159         unsigned long addr = (unsigned long)page_address(page);
 160
 161         pgd = pgd_offset_k(addr);
 162         if (pgd_none(*pgd))
 163                 return false;
 164
 165         pud = pud_offset(pgd, addr);
 166         if (pud_none(*pud))
 167                 return false;
 168         if (pud_sect(*pud))
 169                 return true;
 170
 171         pmd = pmd_offset(pud, addr);
 172         if (pmd_none(*pmd))
 173                 return false;
 174         if (pmd_sect(*pmd))
 175                 return true;
 176
 177         pte = pte_offset_kernel(pmd, addr);
 178         return pte_valid(*pte);
 179 }
 180 #endif /* CONFIG_HIBERNATION */
 181 #endif /* CONFIG_DEBUG_PAGEALLOC */