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 static int change_memory_common(unsigned long addr, int numpages,
  41                                 pgprot_t set_mask, pgprot_t clear_mask)
  42 {
  43         unsigned long start = addr;
  44         unsigned long size = PAGE_SIZE*numpages;
  45         unsigned long end = start + size;
  46         int ret;
  47         struct page_change_data data;
  48         struct vm_struct *area;
  49
  50         if (!PAGE_ALIGNED(addr)) {
  51                 start &= PAGE_MASK;
  52                 end = start + size;
  53                 WARN_ON_ONCE(1);
  54         }
  55
  56         /*
  57          * Kernel VA mappings are always live, and splitting live section
  58          * mappings into page mappings may cause TLB conflicts. This means
  59          * we have to ensure that changing the permission bits of the range
  60          * we are operating on does not result in such splitting.
  61          *
  62          * Let's restrict ourselves to mappings created by vmalloc (or vmap).
  63          * Those are guaranteed to consist entirely of page mappings, and
  64          * splitting is never needed.
  65          *
  66          * So check whether the [addr, addr + size) interval is entirely
  67          * covered by precisely one VM area that has the VM_ALLOC flag set.
  68          */
  69         area = find_vm_area((void *)addr);
  70         if (!area ||
  71             end > (unsigned long)area->addr + area->size ||
  72             !(area->flags & VM_ALLOC))
  73                 return -EINVAL;
  74
  75         if (!numpages)
  76                 return 0;
  77
  78         data.set_mask = set_mask;
  79         data.clear_mask = clear_mask;
  80
  81         ret = apply_to_page_range(&init_mm, start, size, change_page_range,
  82                                         &data);
  83
  84         flush_tlb_kernel_range(start, end);
  85         return ret;
  86 }
  87
  88 int set_memory_ro(unsigned long addr, int numpages)
  89 {
  90         return change_memory_common(addr, numpages,
  91                                         __pgprot(PTE_RDONLY),
  92                                         __pgprot(PTE_WRITE));
  93 }
  94
  95 int set_memory_rw(unsigned long addr, int numpages)
  96 {
  97         return change_memory_common(addr, numpages,
  98                                         __pgprot(PTE_WRITE),
  99                                         __pgprot(PTE_RDONLY));
 100 }
 101
 102 int set_memory_nx(unsigned long addr, int numpages)
 103 {
 104         return change_memory_common(addr, numpages,
 105                                         __pgprot(PTE_PXN),
 106                                         __pgprot(0));
 107 }
 108 EXPORT_SYMBOL_GPL(set_memory_nx);
 109
 110 int set_memory_x(unsigned long addr, int numpages)
 111 {
 112         return change_memory_common(addr, numpages,
 113                                         __pgprot(0),
 114                                         __pgprot(PTE_PXN));
 115 }
 116 EXPORT_SYMBOL_GPL(set_memory_x);