linux/arch/arm64/mm/pageattr.c
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   1// SPDX-License-Identifier: GPL-2.0-only
   2/*
   3 * Copyright (c) 2014, The Linux Foundation. All rights reserved.
   4 */
   5#include <linux/kernel.h>
   6#include <linux/mm.h>
   7#include <linux/module.h>
   8#include <linux/sched.h>
   9#include <linux/vmalloc.h>
  10
  11#include <asm/pgtable.h>
  12#include <asm/set_memory.h>
  13#include <asm/tlbflush.h>
  14
  15struct page_change_data {
  16        pgprot_t set_mask;
  17        pgprot_t clear_mask;
  18};
  19
  20bool rodata_full __ro_after_init = IS_ENABLED(CONFIG_RODATA_FULL_DEFAULT_ENABLED);
  21
  22static int change_page_range(pte_t *ptep, unsigned long addr, void *data)
  23{
  24        struct page_change_data *cdata = data;
  25        pte_t pte = READ_ONCE(*ptep);
  26
  27        pte = clear_pte_bit(pte, cdata->clear_mask);
  28        pte = set_pte_bit(pte, cdata->set_mask);
  29
  30        set_pte(ptep, pte);
  31        return 0;
  32}
  33
  34/*
  35 * This function assumes that the range is mapped with PAGE_SIZE pages.
  36 */
  37static int __change_memory_common(unsigned long start, unsigned long size,
  38                                pgprot_t set_mask, pgprot_t clear_mask)
  39{
  40        struct page_change_data data;
  41        int ret;
  42
  43        data.set_mask = set_mask;
  44        data.clear_mask = clear_mask;
  45
  46        ret = apply_to_page_range(&init_mm, start, size, change_page_range,
  47                                        &data);
  48
  49        flush_tlb_kernel_range(start, start + size);
  50        return ret;
  51}
  52
  53static int change_memory_common(unsigned long addr, int numpages,
  54                                pgprot_t set_mask, pgprot_t clear_mask)
  55{
  56        unsigned long start = addr;
  57        unsigned long size = PAGE_SIZE*numpages;
  58        unsigned long end = start + size;
  59        struct vm_struct *area;
  60        int i;
  61
  62        if (!PAGE_ALIGNED(addr)) {
  63                start &= PAGE_MASK;
  64                end = start + size;
  65                WARN_ON_ONCE(1);
  66        }
  67
  68        /*
  69         * Kernel VA mappings are always live, and splitting live section
  70         * mappings into page mappings may cause TLB conflicts. This means
  71         * we have to ensure that changing the permission bits of the range
  72         * we are operating on does not result in such splitting.
  73         *
  74         * Let's restrict ourselves to mappings created by vmalloc (or vmap).
  75         * Those are guaranteed to consist entirely of page mappings, and
  76         * splitting is never needed.
  77         *
  78         * So check whether the [addr, addr + size) interval is entirely
  79         * covered by precisely one VM area that has the VM_ALLOC flag set.
  80         */
  81        area = find_vm_area((void *)addr);
  82        if (!area ||
  83            end > (unsigned long)area->addr + area->size ||
  84            !(area->flags & VM_ALLOC))
  85                return -EINVAL;
  86
  87        if (!numpages)
  88                return 0;
  89
  90        /*
  91         * If we are manipulating read-only permissions, apply the same
  92         * change to the linear mapping of the pages that back this VM area.
  93         */
  94        if (rodata_full && (pgprot_val(set_mask) == PTE_RDONLY ||
  95                            pgprot_val(clear_mask) == PTE_RDONLY)) {
  96                for (i = 0; i < area->nr_pages; i++) {
  97                        __change_memory_common((u64)page_address(area->pages[i]),
  98                                               PAGE_SIZE, set_mask, clear_mask);
  99                }
 100        }
 101
 102        /*
 103         * Get rid of potentially aliasing lazily unmapped vm areas that may
 104         * have permissions set that deviate from the ones we are setting here.
 105         */
 106        vm_unmap_aliases();
 107
 108        return __change_memory_common(start, size, set_mask, clear_mask);
 109}
 110
 111int set_memory_ro(unsigned long addr, int numpages)
 112{
 113        return change_memory_common(addr, numpages,
 114                                        __pgprot(PTE_RDONLY),
 115                                        __pgprot(PTE_WRITE));
 116}
 117
 118int set_memory_rw(unsigned long addr, int numpages)
 119{
 120        return change_memory_common(addr, numpages,
 121                                        __pgprot(PTE_WRITE),
 122                                        __pgprot(PTE_RDONLY));
 123}
 124
 125int set_memory_nx(unsigned long addr, int numpages)
 126{
 127        return change_memory_common(addr, numpages,
 128                                        __pgprot(PTE_PXN),
 129                                        __pgprot(0));
 130}
 131
 132int set_memory_x(unsigned long addr, int numpages)
 133{
 134        return change_memory_common(addr, numpages,
 135                                        __pgprot(0),
 136                                        __pgprot(PTE_PXN));
 137}
 138
 139int set_memory_valid(unsigned long addr, int numpages, int enable)
 140{
 141        if (enable)
 142                return __change_memory_common(addr, PAGE_SIZE * numpages,
 143                                        __pgprot(PTE_VALID),
 144                                        __pgprot(0));
 145        else
 146                return __change_memory_common(addr, PAGE_SIZE * numpages,
 147                                        __pgprot(0),
 148                                        __pgprot(PTE_VALID));
 149}
 150
 151int set_direct_map_invalid_noflush(struct page *page)
 152{
 153        struct page_change_data data = {
 154                .set_mask = __pgprot(0),
 155                .clear_mask = __pgprot(PTE_VALID),
 156        };
 157
 158        if (!rodata_full)
 159                return 0;
 160
 161        return apply_to_page_range(&init_mm,
 162                                   (unsigned long)page_address(page),
 163                                   PAGE_SIZE, change_page_range, &data);
 164}
 165
 166int set_direct_map_default_noflush(struct page *page)
 167{
 168        struct page_change_data data = {
 169                .set_mask = __pgprot(PTE_VALID | PTE_WRITE),
 170                .clear_mask = __pgprot(PTE_RDONLY),
 171        };
 172
 173        if (!rodata_full)
 174                return 0;
 175
 176        return apply_to_page_range(&init_mm,
 177                                   (unsigned long)page_address(page),
 178                                   PAGE_SIZE, change_page_range, &data);
 179}
 180
 181void __kernel_map_pages(struct page *page, int numpages, int enable)
 182{
 183        if (!debug_pagealloc_enabled() && !rodata_full)
 184                return;
 185
 186        set_memory_valid((unsigned long)page_address(page), numpages, enable);
 187}
 188
 189/*
 190 * This function is used to determine if a linear map page has been marked as
 191 * not-valid. Walk the page table and check the PTE_VALID bit. This is based
 192 * on kern_addr_valid(), which almost does what we need.
 193 *
 194 * Because this is only called on the kernel linear map,  p?d_sect() implies
 195 * p?d_present(). When debug_pagealloc is enabled, sections mappings are
 196 * disabled.
 197 */
 198bool kernel_page_present(struct page *page)
 199{
 200        pgd_t *pgdp;
 201        pud_t *pudp, pud;
 202        pmd_t *pmdp, pmd;
 203        pte_t *ptep;
 204        unsigned long addr = (unsigned long)page_address(page);
 205
 206        if (!debug_pagealloc_enabled() && !rodata_full)
 207                return true;
 208
 209        pgdp = pgd_offset_k(addr);
 210        if (pgd_none(READ_ONCE(*pgdp)))
 211                return false;
 212
 213        pudp = pud_offset(pgdp, addr);
 214        pud = READ_ONCE(*pudp);
 215        if (pud_none(pud))
 216                return false;
 217        if (pud_sect(pud))
 218                return true;
 219
 220        pmdp = pmd_offset(pudp, addr);
 221        pmd = READ_ONCE(*pmdp);
 222        if (pmd_none(pmd))
 223                return false;
 224        if (pmd_sect(pmd))
 225                return true;
 226
 227        ptep = pte_offset_kernel(pmdp, addr);
 228        return pte_valid(READ_ONCE(*ptep));
 229}
 230