LXR linux/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
  23struct page_change_data {
  24        pgprot_t set_mask;
  25        pgprot_t clear_mask;
  26};
  27
  28static 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 */
  44static 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
  60static 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
  99int 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
 106int 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
 113int set_memory_nx(unsigned long addr, int numpages)
 114{
 115        return change_memory_common(addr, numpages,
 116                                        __pgprot(PTE_PXN),
 117                                        __pgprot(0));
 118}
 119EXPORT_SYMBOL_GPL(set_memory_nx);
 120
 121int set_memory_x(unsigned long addr, int numpages)
 122{
 123        return change_memory_common(addr, numpages,
 124                                        __pgprot(0),
 125                                        __pgprot(PTE_PXN));
 126}
 127EXPORT_SYMBOL_GPL(set_memory_x);
 128
 129int 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
 142void __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 */
 157bool 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 */
 188