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/set_memory.h>
  21 #include <asm/tlbflush.h>
  22
  23 struct page_change_data {
  24         pgprot_t set_mask;
  25         pgprot_t clear_mask;
  26 };
  27
  28 static int change_page_range(pte_t *ptep, pgtable_t token, unsigned long addr,
  29                         void *data)
  30 {
  31         struct page_change_data *cdata = data;
  32         pte_t pte = READ_ONCE(*ptep);
  33
  34         pte = clear_pte_bit(pte, cdata->clear_mask);
  35         pte = set_pte_bit(pte, cdata->set_mask);
  36
  37         set_pte(ptep, pte);
  38         return 0;
  39 }
  40
  41 /*
  42  * This function assumes that the range is mapped with PAGE_SIZE pages.
  43  */
  44 static int __change_memory_common(unsigned long start, unsigned long size,
  45                                 pgprot_t set_mask, pgprot_t clear_mask)
  46 {
  47         struct page_change_data data;
  48         int ret;
  49
  50         data.set_mask = set_mask;
  51         data.clear_mask = clear_mask;
  52
  53         ret = apply_to_page_range(&init_mm, start, size, change_page_range,
  54                                         &data);
  55
  56         flush_tlb_kernel_range(start, start + size);
  57         return ret;
  58 }
  59
  60 static int change_memory_common(unsigned long addr, int numpages,
  61                                 pgprot_t set_mask, pgprot_t clear_mask)
  62 {
  63         unsigned long start = addr;
  64         unsigned long size = PAGE_SIZE*numpages;
  65         unsigned long end = start + size;
  66         struct vm_struct *area;
  67
  68         if (!PAGE_ALIGNED(addr)) {
  69                 start &= PAGE_MASK;
  70                 end = start + size;
  71                 WARN_ON_ONCE(1);
  72         }
  73
  74         /*
  75          * Kernel VA mappings are always live, and splitting live section
  76          * mappings into page mappings may cause TLB conflicts. This means
  77          * we have to ensure that changing the permission bits of the range
  78          * we are operating on does not result in such splitting.
  79          *
  80          * Let's restrict ourselves to mappings created by vmalloc (or vmap).
  81          * Those are guaranteed to consist entirely of page mappings, and
  82          * splitting is never needed.
  83          *
  84          * So check whether the [addr, addr + size) interval is entirely
  85          * covered by precisely one VM area that has the VM_ALLOC flag set.
  86          */
  87         area = find_vm_area((void *)addr);
  88         if (!area ||
  89             end > (unsigned long)area->addr + area->size ||
  90             !(area->flags & VM_ALLOC))
  91                 return -EINVAL;
  92
  93         if (!numpages)
  94                 return 0;
  95
  96         return __change_memory_common(start, size, set_mask, clear_mask);
  97 }
  98
  99 int set_memory_ro(unsigned long addr, int numpages)
 100 {
 101         return change_memory_common(addr, numpages,
 102                                         __pgprot(PTE_RDONLY),
 103                                         __pgprot(PTE_WRITE));
 104 }
 105
 106 int set_memory_rw(unsigned long addr, int numpages)
 107 {
 108         return change_memory_common(addr, numpages,
 109                                         __pgprot(PTE_WRITE),
 110                                         __pgprot(PTE_RDONLY));
 111 }
 112
 113 int set_memory_nx(unsigned long addr, int numpages)
 114 {
 115         return change_memory_common(addr, numpages,
 116                                         __pgprot(PTE_PXN),
 117                                         __pgprot(0));
 118 }
 119 EXPORT_SYMBOL_GPL(set_memory_nx);
 120
 121 int set_memory_x(unsigned long addr, int numpages)
 122 {
 123         return change_memory_common(addr, numpages,
 124                                         __pgprot(0),
 125                                         __pgprot(PTE_PXN));
 126 }
 127 EXPORT_SYMBOL_GPL(set_memory_x);
 128
 129 int set_memory_valid(unsigned long addr, int numpages, int enable)
 130 {
 131         if (enable)
 132                 return __change_memory_common(addr, PAGE_SIZE * numpages,
 133                                         __pgprot(PTE_VALID),
 134                                         __pgprot(0));
 135         else
 136                 return __change_memory_common(addr, PAGE_SIZE * numpages,
 137                                         __pgprot(0),
 138                                         __pgprot(PTE_VALID));
 139 }
 140
 141 #ifdef CONFIG_DEBUG_PAGEALLOC
 142 void __kernel_map_pages(struct page *page, int numpages, int enable)
 143 {
 144         set_memory_valid((unsigned long)page_address(page), numpages, enable);
 145 }
 146 #ifdef CONFIG_HIBERNATION
 147 /*
 148  * When built with CONFIG_DEBUG_PAGEALLOC and CONFIG_HIBERNATION, this function
 149  * is used to determine if a linear map page has been marked as not-valid by
 150  * CONFIG_DEBUG_PAGEALLOC. Walk the page table and check the PTE_VALID bit.
 151  * This is based on kern_addr_valid(), which almost does what we need.
 152  *
 153  * Because this is only called on the kernel linear map,  p?d_sect() implies
 154  * p?d_present(). When debug_pagealloc is enabled, sections mappings are
 155  * disabled.
 156  */
 157 bool kernel_page_present(struct page *page)
 158 {
 159         pgd_t *pgdp;
 160         pud_t *pudp, pud;
 161         pmd_t *pmdp, pmd;
 162         pte_t *ptep;
 163         unsigned long addr = (unsigned long)page_address(page);
 164
 165         pgdp = pgd_offset_k(addr);
 166         if (pgd_none(READ_ONCE(*pgdp)))
 167                 return false;
 168
 169         pudp = pud_offset(pgdp, addr);
 170         pud = READ_ONCE(*pudp);
 171         if (pud_none(pud))
 172                 return false;
 173         if (pud_sect(pud))
 174                 return true;
 175
 176         pmdp = pmd_offset(pudp, addr);
 177         pmd = READ_ONCE(*pmdp);
 178         if (pmd_none(pmd))
 179                 return false;
 180         if (pmd_sect(pmd))
 181                 return true;
 182
 183         ptep = pte_offset_kernel(pmdp, addr);
 184         return pte_valid(READ_ONCE(*ptep));
 185 }
 186 #endif /* CONFIG_HIBERNATION */
 187 #endif /* CONFIG_DEBUG_PAGEALLOC */