root/arch/arm64/mm/pageattr.c

DEFINITIONS

1. change_page_range
2. __change_memory_common
3. change_memory_common
4. set_memory_ro
5. set_memory_rw
6. set_memory_nx
7. set_memory_x
8. set_memory_valid
9. set_direct_map_invalid_noflush
10. set_direct_map_default_noflush
11. __kernel_map_pages
12. kernel_page_present

   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 
  15 struct page_change_data {
  16         pgprot_t set_mask;
  17         pgprot_t clear_mask;
  18 };
  19 
  20 bool rodata_full __ro_after_init = IS_ENABLED(CONFIG_RODATA_FULL_DEFAULT_ENABLED);
  21 
  22 static 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  */
  37 static 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 
  53 static 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 
 111 int 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 
 118 int 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 
 125 int 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 
 132 int 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 
 139 int 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 
 151 int 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 
 166 int 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 
 181 void __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  */
 198 bool 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 }